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In recent years, Spartina alterniflora as an invasive species has seriously threatened the native coastal ecosystem of China. There is a lack of effective management and utilization methods towards Spartina alterniflora at present. To realize the ecological remediation and resource utilization of Spartina alterniflora , the functional biochar (BC) materials were successfully prepared using Spartina alterniflora as the substrates via the high temperature calcination method, which were utilized for efficient removal of antibiotics. The biochar was further activated by ZnCl 2 (ZnBC) and optimized under different calcination temperatures and ZnCl 2 dosages to improve the adsorption ability. Among these biochar materials, the ZnCl 2 -activated biochar obtained under the mass ratio of Spartina alterniflora to ZnCl 2 of 1:5 and calcination temperature of 600 °C (ZnBC-600) exhibited the strongest adsorption performance towards sulfadiazine (SDZ) and ciprofloxacin (CIP), which can be attributed to the larger specific surface area, richer pore structure and more abundant surface oxygen-containing functional groups. Additionally, the adsorption kinetics and isotherms demonstrated that the adsorption of both SDZ and CIP onto ZnBC-600 (1:5) followed the pseudo-second-order kinetic model and Freundlich model. At the same time, the performances of Spartina alterniflora biochar derived from different biomass were compared under the condition of activation with ZnCl 2 , presenting the superior performance of ZnCl 2 activated Spartina alterniflora biochar. Moreover, the adsorption mechanism of ZnBC-600 (1:5) was proposed, illustrating the crucial roles of effects of electrostatic attraction, pore filling, oxygen-containing groups complexation, π-π stacking and hydrogen bonding in the adsorption of antibiotics. Above all, this study not only provides a feasible strategy for the preparation of functional biochar derived from Spartina alterniflora for removing organic pollutants, but also opens up a new pathway for resource utilization of Spartina alterniflora. [Display omitted] [ABSTRACT FROM AUTHOR]

Water scarcity and water-related soil erosion are severely exacerbated by inappropriate human activities and global climate change. Hence, to find a suitable technology to mitigate drought and soil erosion, three consecutive field experiments were conducted to explore the impact of ridge-furrow cropping with biochar amendment on soil water storage, runoff, sediment yield, soil nutrient losses, alfalfa (Medicago sativa L) fodder yield, crop water productivity (WP c), and economic benefit from 2019 to 2021. This experiment was conducted in a split-plot design, taking biochar amendment patterns (no biochar amendment and biochar amendment at a rate of 3× 104 kg ha−1) as a main plot and ridge-furrow technologies (traditional planting, open-ridging, and tied-ridging) as a split-plot. The combination of biochar amendment with ridge-furrow technology, especially tied-ridging technology, increased soil water storage, and captured runoff, sediment, and related soil nutrient losses, consequently increasing alfalfa fodder yield, WP c , and income. During this study, compared to traditional planting, open-ridging depicted an increase in soil water storage by a range of 9.8–39.6 mm, an alfalfa fodder yield boost ranging from 9.8% to 38.6%, and a WP c increase ranging from 0.1 to 16.5 kg ha−1 mm−1. On the other hand, tied-ridging showed greater improvements with soil water storage increasing by 29.1–65.1 mm, alfalfa fodder yield growing by 11.6–44.4%, and WP c advancing by 0.9–17.5 kg ha−1 mm−1. The mean decrease in runoff, sediment, and nutrients (total nitrogen, total phosphorus, and organic matter) loss for open-ridging was 17.9%-37.7%, 46.4%-75.5%, and 40.4%-75.3%, respectively, while for tied-ridging, it was 22.3%-55.5%, 62.1%-87.6%, and 49.0%-87.3%, respectively. Compared to no biochar amendment, soil water storage, alfalfa fodder yield, and WP c for biochar amendment increased by 9.1%-20.4%, 5.8%-52.7%, and 4.6–7.8 kg ha−1 mm−1, respectively, while runoff, sediment, and nutrients loss for biochar amendment decreased by 32.2%-40.9%, 25.5%-55.5%, and 35.9%-53.3%, respectively. Structural equation modeling analysis indicated that the significant direct effect of biochar amendment and ridge-furrow technology on WP c was 0.20 and 0.62, respectively, whereas the significant direct effect of runoff and actual crop evapotranspiration on alfalfa fodder yield was −0.40 and 0.94, respectively. Tied-ridge cropping combined with biochar addition was a highly suggested approach for addressing soil erosion and enhancing alfalfa fodder yields in the Loess Plateau in China. This technology could mitigate soil water scarcity and soil erosion, and give farmers the confidence to invest in this technology in dryland regions. • Ridge-furrow technology with biochar amendment reduced soil erosion. • Ridge-furrow technology with biochar amendment increased crop yield. • Biochar amendment and ridge-furrow technology had a direct effect on water use efficiency. • Runoff and evapotranspiration had a direct effect on alfalfa fodder yield. • Tied-ridge cropping with biochar amendment was recommended. [ABSTRACT FROM AUTHOR]

Biochar application to agricultural fields is an effective carbon sequestration measure that has the potential to reduce N 2 O emissions and increase soil water holding capacity. However, the interaction mechanisms of biochar under deficit irrigation on N 2 O emissions remain unclear. A two-year field experiment is conducted in the Guanzhong Plain, China, in order to quantify the effects of biochar and deficit irrigation on N 2 O emissions from winter wheat–summer maize crop rotation and to investigate the potential mechanisms of nitrification and denitrification. According to the combination of biochar application and actual evapotranspiration-based irrigation scheduling, four treatments are designed (B 1 W 100 : biochar 30 t·ha−1 + ET; B 1 W 80 : biochar 30 t·ha−1+ 0.8 ET; B 0 W 100 : no biochar + ET; B 0 W 80 : no biochar + 0.8ET). The soil N 2 O flux, soil physical and chemical properties, and key functional gene abundance related to N 2 O emissions in nitrification and denitrification at different growth stages are investigated and discussed. Results show that the interaction between deficit irrigation and biochar significantly reduces soil N 2 O emissions. During the wheat and maize season, the application of biochar reduces the N 2 O emissions by an average of 12.9% and 15.2%, respectively. Deficit irrigation also reduces the N 2 O emissions by an average of 17.4% and 15.5%, respectively. Pearson correlation analysis shows that soil N 2 O is significantly correlated with soil water-filled pore space during the phase with intense N 2 O emissions. Soil functional gene abundance is determined at different growth stages for both wheat and maize. Maximum soil denitrification functional gene abundance is observed at the time when wheat and maize enter the stage of their peak growth at the jointing stage. With biochar addition and deficit irrigation, the abundance of nirK and nosZ genes increases and AOB amoA genes decreases. These results suggest that biochar with deficit irrigation is a better solution to reduce N 2 O emissions from agricultural soils. • The interaction of deficit irrigation and biochar reduce N 2 O emissions from wheat-maize rotation croplands. • A sudden increase in N 2 O emissions after irrigation, with soil water-filled pore space (WFPS) as the main regulator. • Deficit irrigation and biochar addition reduced AOB gene abundance and increased nirK and nosZ gene abundance. [ABSTRACT FROM AUTHOR]

Excessive water and nitrogen inputs in agricultural production can result in resource wastage and environmental pollution. This makes it imperative to identify effective farmland management strategies to ensure sustainable agriculture development, and it remains to be explored whether biochar can be an effective solution. In this study, a 2-year (2021 and 2022) field experiment was conducted with two irrigation levels, W 100 (ET) and W 80 (0.8 ET), and three nitrogen fertilizer levels, N H (270 kg ha−1), N M (180 kg ha−1), and N L (90 kg ha−1), in full combination with biochar (30 t ha−1). The N M and N 0 treatments without biochar at both irrigation levels were set as controls. The results of the study showed that there was no significant difference in maize yield between the high and medium N treatments. Further, maximum water productivity (WP), nitrogen agronomic efficiency (NAE), and nitrogen recovery efficiency (NRE) were obtained in N M treatments when water and nitrogen were kept consistent. Deficit irrigation was effective in reducing water consumption and increased WP by 15.54% and 11.06% in 2021 and 2022, respectively. Biochar application increased WP, nitrogen use efficiencies, and significantly increased the yield by 7.02% and 6.46% in 2021 and 2022, respectively. Therefore, the application of biochar can be an effective measure to promote crop growth and resource use. Based on the results of this experiment, an irrigation level of 0.8 ET in combination with N M and biochar application is recommended to ensure the sustainability of agricultural production. • Deficit irrigation reduced water consumption and increased water productivity (WP). • Biochar promoted crop growth and resource utilization combined with suited W/N programs. • Medium N increased water productivity and did not significantly reduce yield than high N. • Biochar, medium N, and deficit irrigation produced high yields, WP & N utilization. [ABSTRACT FROM AUTHOR]

• Maize-based organic amendments were examined after seven years of annual application. • All organic amendments increased SOM in bulk soil and all physical fractions. • Biochar exerted the strongest positive effect on SOC contents and thermal stability. • The majority of the accumulated C and N occurred in the silt + clay fractions. Application of organic amendments and N fertilizer can affect C and N sequestration, however, the degree to which diverse organic amendments and optimal N fertilization for matching demand for high crop productivity contributes to soil organic matter (SOM) of Cambisol in the North China Plain is not fully known. The objective was to evaluate the combined effects of annual maize straw-derived organic amendments (straw, manure, compost, biogas residue, or biochar) and in-season mineral N fertilizer amendment on soil organic carbon (SOC) and total N (TN) accumulation and thermal stability in bulk soils and physically isolated soil aggregate fractions in a long-term field experiment on the North China Plain. Application of organic amendments either alone or with N increased the proportion of macroaggregates (+62 to 137 %), aggregate mean weight diameter (+50 to 106 %), SOC (+38 to 206 %) and TN (+13 to 52 %) contents in bulk soil. The organic amendments and N fertilizer additions also increased SOC and TN contents in each of the isolated fractions: macroaggregates (+119 to 851 % for SOC, +109 to 237 % for TN) and microaggregates (+42 to 192 % for SOC and +30 to 145 % for TN), total fine particulate organic matter (T fPOM, +143 to 891 % for T fPOM-SOC, +129 to 549 % for T fPOM-TN) and total silt + clay within aggregates (53–139 % for SOC and 20–106 % for TN). Biochar resulted in the largest increase in SOC contents and improved soil aggregation without N fertilization, but fertilization greatly decreased these responses. The majority of the accumulated C and N occurred in the total silt + clay fractions, making up 50–90 % of total SOC and 79–96 % of total TN. Total fine POM and total silt + clay within aggregates contributed to 40–78 % and 10–56 % of SOC, 28–60 % and 37–71 % of TN increase between soil with and without organic amendments. Our results suggested that C and N retained in T fPOM and silt + clay fractions within aggregates were important mechanisms for C and N stabilization. Substitution of annual above-ground litter with biochar with or without mineral N fertilizer was the most effective way for SOM build up and stabilization under a wheat/maize system in the North China Plain, while manure, compost and biogas residue resulted in little to no increases of SOM in bulk soils and physically isolated aggregate fractions compared to straw amendment. Besides the effects of each amendment type on SOC, the different recovery rates of the various amendments, which determines the total quantity of each amendment that can be produced, should be taken into consideration in decisions about maize residue management at the regional scale in the North China Plain. [ABSTRACT FROM AUTHOR]

Biochar as a prospective renewable energy candidate could be incorporated into the iron and steel production system to replace part of fossil fuels and reduce high-intensity greenhouse gas emissions. However, great uncertainties still exist on biochar's emission reduction capacity and economic feasibility, depending on different biochar precursors, substitution scenarios, energy consumption of biochar production and financial cost. This study aimed to explore the optimized substitution strategies concerning the above issues. A systematic carbon accounting was performed by material flow analysis method (MFA). Two biochar incorporated iron and steel production routes, integrated production route (BF-BOF) and short production route (EAF), which took the proportion of 71.5% and 28.2% in worldwide production, were considered. CO 2 Supply Curve (CSC) was conducted to carry out a quantitative economic viability analysis of biochar substitution under carbon emission trading schemes (ETS). Results showed that compared with straw-based biochar, wood-based biochar showed stronger carbon reduction capacity of 1.47 t CO 2e (CO 2-equivalent) /t crude steel, and the reduction potential reached 66.94% mostly. Among all the steel production processes, Blast furnace in BF-BOF route had the largest emission contribution proportion (72.06%), achieving the best GWP100 reduction potential of 73.66%. The incorporation of wood-based biochar in sintering (−0.037 yuan/t CO 2e) was selected as the scenario with both reduction potential and economic viability. If the scenario was fully implemented in China, it could reduce 2.01 million tons of CO 2e in 2021. This study would play a vital role in guiding iron and steel industry for biochar substituted fuels. [Display omitted] • Modern self-heating biochar production is considered in fuels substitution. • Wood-based biochar stands out in the emission reduction capacity of GWP100. • Biochar fuels substitution can reduce 66.94% CO 2e /t crude steel of GWP100. • Blast furnace process contributes 73.66% of the GWP100 reduction potential. • Implementation of wood-based biochar in sintering is the most economical route. [ABSTRACT FROM AUTHOR]

In this study, we used different concentrations of H 3 PO 4 to activate pristine biochar (BC) derived from cow dung (BC and BC modified with phosphoric acid at concentrations of 10% (10P-BC), 30% (30P-BC), and 50% (50P-BC)) in order to obtain cheap, high-performance adsorbents. Brunauer–Emmett–Teller analysis, scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, organic element composition determination, and other analyses showed that activation with H3PO4 increased the porosity and hydrophilicity compared with the original BC, thereby enhancing the adsorption properties. The Langmuir isotherm model obtained the best fit and the maximum capacities for adsorbing enrofloxacin by BCs were 12.66 mg/g for BC, 51.90 mg/g for 10P-BC, 63.61 mg/g for 30P-BC, and 26.79 mg/g for 50P-BC. The main mechanisms responsible for antibiotic loading on BC were hydrogen bonding, π–π electron donor–acceptor interactions, pore filling, and electrostatic interactions. Calculations of fixed carbon retention before and after pyrolysis, and adsorption showed that activated BC had a good carbon fixation capacity and it was more capable of adsorbing enrofloxacin compared with the original BC, thereby providing a new method for removing organic pollutants from the environment and reducing carbon emissions. The cost efficiency was analyzed using the improved fuzzy comprehensive evaluation model based on the entropy method. Removal efficiency and utilization efficiency indicators were calculated for the different phosphoric acid activated BCs. The pollutant removal efficiencies were better for 10P-BC and 30P-BC, and the optimal removal efficiency was determined for 30P-BC. Given the current global climate change situation, using 10P-BC and 30P-BC could also help to meet China's carbon neutrality goals by reducing emissions of pollutants containing carbon. [Display omitted] • Enrofloxacin-adsorption using biochar modified were investigated. • The adsorption kinetics and isotherm of enrofloxacin by biochar were carried out. • Mechanisms were explained. [ABSTRACT FROM AUTHOR]

• BC is explored in the engineering practice for sediment remediation. • In situ BC capping is feasible to control NH 4 +-N release from sediments. • DGT is firstly used to measure NH 4 +-N in the pore water of field experiment. • The mechanism of BC controlling NH 4 +-N release from sediments is firstly proposed. Evaluation of in situ capping with biochar (BC) to control ammonia nitrogen (NH 4 +-N) release from the sediments of Baiyangdian Lake, the largest freshwater lake in northern China, was performed after 10 months of field and mesocosm experiments. The concentration of NH 4 +-N in pore water and its resupply from native sediments and capped sediments were determined using the technique of diffusive equilibrium in thin films (DET) and the technique of diffusive gradients in thin films with CMI-7000 cation ion exchange membrane (CMI-DGT) binding layer. The results showed a low concentration of NH 4 +-N in pore water and a low resupply from the sediment or capping materials after BC capping. The concentration of bioavailable NH 4 +-N measured by DGT of the top 4 cm layer in BC capping layer was only 12.8%−29.2% of the native sediments. Flux DET -NH 4 +-N , could be reduced from 12.74 to 3.44 mg·m−2·d−1 and Flux DGT -NH 4 +-N was further reduced from 13.38 to 1.59 mg·m−2·d−1. The calculated concentration gradient at the sediment-water interface following the capping treatment was lower than the control. These results implied that BC capping reduced the release of NH 4 +-N from the sediments. The low resupply from the sediments was further demonstrated by the smaller ratio of C DGT to C DET (R) in the BC capping layer, which their average values were 0.48, 0.59, 0.68 in the BC capping layer, BC/soil layer and native sediments, respectively. The physical, chemical and microbiological effects were attributed to inhibit the NH 4 +-N release from sediments by the BC capping. [ABSTRACT FROM AUTHOR]

Biochar addition affects soil conditions and soil microorganisms, and it may reduce soil CO 2 emissions. However, knowledge on how biochar addition induces the changes in soil microbial communities with soil depth and time and affects soil respiration is limited in forest ecosystems. We investigated the effects of biochar addition on soil respiration rate and its sensitivity to soil temperature and microbial community composition in moso bamboo (Phyllostachys eduis) plantations in subtropical China for two years. We set up four treatments of biochar addition onto the soil surface of the plantations with the level of 0 (control, CK), 5 (low biochar, LB), 10 (medium biochar, MB), or 20 t biochar ha−1 (high biochar, HB) in April 2014. Biochar addition significantly improved soil moisture at 5 cm soil depth but did not affect soil temperature. Microbial biomass increased significantly with biochar addition at 10–20 cm soil depth but showed no response in the 0–10 cm depth soil layer. Compared to CK, biochar addition significantly affected the mean soil respiration rate during the two–year experiment, but the difference between CK and biochar treatments decreased both with time following biochar addition and with increasing biochar dosage. Annual cumulative soil respiration was significantly and positively correlated with the biomass of total PLFAs, gram-negative bacteria, bacteria, and arbuscular mycorrhizal fungi (P < 0.05) at 0–10 cm soil depth but not at 10–20 cm. Overall, only LB significant decreased the total CO 2 emissions. Our results suggest that lower dosage additions of biochar have a positive effect in reducing total CO 2 emissions and promote soil organic carbon sequestration in bamboo forests in subtropical China. • Low biochar addition seems to be the best dosage to decrease soil respiration rate. • Biochar addition significantly increased microbial biomass in subsurface soil layer. • Increased subsurface microbial biomass has limited effect on reducing soil CO 2 efflux. • Annual cumulative CO 2 efflux was consistent with total PLFAs biomass in surface soil. [ABSTRACT FROM AUTHOR]

To reduce water scarcity in China, the use of reclaimed water or anaerobically treated piggery wastewater, either alone or coupled with biochar supplementation, is attracting increasing attention. However, little information is available regarding their effects on the soil and plant microbiomes receiving irrigation. The objective of this study was to evaluate different water quality irrigation (distilled water, reclaimed water, and piggery wastewater), biochar supplementation, and their interactions on the microbiomes of rhizosphere and bulk soil, and the root endosphere of maize using high-throughput 16S rRNA amplicon sequencing. The experiments were conducted in greenhouse rhizoboxes. The microbiome functional potentials were predicted using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). After a 60-day cultivation period, the bacterial communities and potential functions of rhizosphere, bulk soil, and root endosphere displayed distinct differences between irrigation water sources. Irrigation water quality and biochar supplementation influenced bacterial diversity in rhizosphere soil, and bacterial composition was more sensitive to irrigation water quality than to biochar supplementation in soil and root samples. Reclaimed water and piggery wastewater irrigation decreased the abundance of putative plant growth-promoting rhizobacteria (PGPR) and increased the abundance of known pathogenic bacteria. Biochar supplementation elicited the same behaviour. Mantel tests indicated that soil pH and available P exerted strong influences on the structure of the bacterial community in rhizosphere and bulk soil, but total N significantly influenced the bacterial community structure within the root. The current study implies the potential ecological effects (e. g. PGPR and pathogenic bacteria) of the irrigation with different quality water should be considered with biochar supplementation. • Irrigation water quality affected bacterial community alpha and beta diversity. • Bacterial community differed between soil and root samples (P < 0.01). • Under irrigation, the role of biochar on PGPR and pathogens should be considered. • pH and available P were main factors in shaping microbiome composition in soil. [ABSTRACT FROM AUTHOR]

Straw-return methods that neither negatively impact yield nor bring environmental risk are ideal patterns. To attain this goal, it is necessary to conduct field observation to evaluate the environmental influence of different straw-return methods. Therefore, we conducted a 2-year field study in 2015–2017 to investigate the emissions of methane (CH 4) and nitrous oxide (N 2 O) and the changes in topsoil (0–20 cm) organic carbon (SOC) density in a typical Chinese rice-wheat rotation in the Eastern China. These measurements allowed a complete greenhouse gas accounting (net GWP and GHGI) of five treatments including: FP (no straw, plus fertilizer), FS (wheat straw plus fertilizer), FB (straw-derived biochar plus fertilizer), FSDI (wheat straw with straw-decomposing microbial inoculants plus fertilizer) and CK (control: no straw, no fertilizer). Average annual SOC sequestration rates were estimated to be 0.20, 0.97, 1.97 and 1.87 t C ha−1 yr−1 (0–20 cm) for the FP, FS, FB and FSDI treatments respectively. Relative to the FP treatment, the FS and FSDI treatments increased CH 4 emissions by 12.4 and 17.9% respectively, but decreased N 2 O emissions by 19.1 and 26.6%. Conversely, the FB treatment decreased CH 4 emission by 7.2% and increased N 2 O emission by 10.9% compared to FP. FB increased grain yield, but FS and FSDI did not. Compared to the net GWP (11.6 t CO 2 -eq ha−1 yr−1) and GHGI (1.20 kg CO 2 -eq kg−1 grain) of FP, the FS, FB and FSDI treatments reduced net GWP by 12.6, 59.9 and 34.6% and GHGI by 10.5, 65.8 and 37.7% respectively. In rice-wheat systems of eastern China, the environmentally beneficial effects of returning wheat straw can be greatly enhanced by application of straw-decomposing microbial inoculants or by applying straw-derived biochar. Image 1 1. Global warming potentials of different straw-return methods compared in two-year rice-wheat study. 2. Straw retention increased soil CH 4 and N 2 O emitted, but not soil organic C (SOC). 3. Straw plus microbial inoculants increased SOC and CH 4 emitted, but decreased N 2 O. 4. Straw-derived biochar increased SOC, crop yields and N 2 O emitted, but reduced CH 4. 5. Global warming potential reduced by straw plus microbial inoculants or straw-biochar. [ABSTRACT FROM AUTHOR]

There are global concerns about heavy metal (HM) contamination in soils, which in turn has produced an increased demand for soil remediation. Biochar has been widely documented to effectively immobilize metals in contaminated soils and has received increasing attention for use in soil remediation. Here, we review recent progresses in understanding metal-biochar interactions in soils, potential risks associated with biochar amendment, and application of biochar in soil remediation in China. These recent studies indicate that: (1) the remediation effect depends on the characteristics of both biochar and soil and their interactions; (2) biochar applications could decrease the mobility/bioavailability of HMs in soils and HM accumulation in plants; and (3) despite its advantages, biochar applications could pose ecological and health risks, e.g., by releasing toxic substances into soils or by inhalation of biochar dust. Research gaps still exist in the development of practical methods for preparing and applying different biochars that target specific HMs. In the future, the long term effects and security of biochar applications on soil remediation, soil organisms and plant growth need to be considered. Image 10888 • The metal-biochar interactions and mechanisms in soils were reviewed. • Potential risks associated with biochar amendment were discussed. • Cases of biochar application in soils in China were summarized. • Long term effects of biochar on soil remediation need further investigation. The remediation of heavy metal contaminated soils by biochar in China was reviewed, including metal-biochar interactions and mechanisms, its application risk and status. [ABSTRACT FROM AUTHOR]

Biochar (BC) addition is widely used in agriculture to condition soils. However, the effects of BC addition on soil microbial community diversity and composition in karstic regions are unclear, especially after long-term application. To address this knowledge-gap, a field experiment was established to examine changes in soil physicochemical properties and microbial communities following six years of BC amendment. BC was applied to calcareous soils in a karstic region of southwestern China at four levels (w/w): 0%, 1.0%, 5.0%, and 10%. Bacterial community composition was then investigated in both the rhizosphere and bulk soils by 16S rRNA gene sequencing on the Illumina MiSeq Platform. BC addition increased soil pH, total carbon (TC), total nitrogen (TN), and total hydrogen (TH) contents in the rhizosphere and bulk soils. In addition, BC amendment was associated with changes in soil bacterial community compositions and diversities, especially at higher BC application levels. The relative abundances of Gemmatimonadetes increased in rhizosphere soils with increasing BC amendment, while those of the Bacteroidetes , Firmicutes , and Cyanobacteria decreased. The relative abundances of Proteobacteria and Chloroflexi increased in bulk soils with increasing BC application levels, while those of the Bacteroidetes and Verrucomicrobia decreased. Canonical correspondence analysis indicated that bacterial community composition was related to soil characteristics including pH, TC, TN, and TH contents in both rhizosphere and bulk soils. Importantly, variations in these soil parameters were closely associated with BC application rates. These results indicate that long-term BC application significantly impacts soil bacterial community characteristics in karstic regions via modulation of soil physiochemical properties. • Six years biochar addition altered rhizosphere and bulk soil properties. • Biochar changed the diversity and composition of soil bacterial communities. • Abundance of rhizosphere Gemmatimonadetes was increased by biochar addition. • Biochar increased the abundance of Proteobacteria and Chloroflexi in the bulk soil. • Long-term biochar application significantly affects the bacterial community. [ABSTRACT FROM AUTHOR]

Abstract The soils in northwest China are severely stressed with nutrient deficiency and water depletion, thus limiting crop production and sustainable agricultural development. Biochar-based amendments, tailored for specific soil issues, have raised great public interest for soil improvement and carbon sequestration. Peanut shell-derived biochar (PBC) and PBC-based amendment (PAD) obtained from composting were added at concentrations of 0%, 1.5%, 3%, and 5% (w/w) into light sierozem soil to compare their effects on growth of crown daisy (Chrysanthemum coronarium L.) and leaf lettuce (Lactuca sativa var longifoliaf L.). PBC had no significant effect on the yields of the two vegetables due to the second season growth, while addition of low concentrations of PAD (≤3%) significantly increased their yields by 15.8%–107%. The positive effect of PAD was primarily attributed to the improved soil qualities (e.g., water holding capacity (WHC), soil organic matter (SOM), electrical conductivity (EC)) and increased contents of available macronutrients (e.g., P and K), and micronutrients (e.g., B, Zn and Mn). However, addition of 5% PAD decreased the yield of crown daisy by 26.9% compared to that grown in untreated soil because of surplus nutrient input resulting in high EC. Overall, our findings demonstrated that the designed PAD synthesized from PBC compost had the potential to ameliorate the infertility in the soil and thus to improve vegetable yield. Graphical abstract Image 1 Highlights • Peanut shell-derived biochar (PBC) was added to produce PBC-based amendment (PAD) by composting. • PBC had little effect on growth and mass yields of crown daisy and leaf lettuce. • PAD at lower concentrations (≤3%) markedly increased the yields of two vegetables. • Increased yields were due to the enhanced soil properties and available nutrients. • 5%PAD decreased yields due to excessive nutrient and high electrical conductivity. [ABSTRACT FROM AUTHOR]

Abstract Biochar application is proposed having a potential of inhibiting greenhouse gases emissions from paddy fields, which is considered to be a main source of atmospheric greenhouse gases. However, the impacts of biochar on greenhouse gases from paddy field have not been investigated under controlled irrigation (CI). Field experiments were conducted during 2016–2017 to determine the effect of biochar application combined with controlled irrigation on rice yield and methane (CH 4) and nitrous oxide (N 2 O) emission from paddy fields in the Taihu Lake Region of China. Four treatments (0 t ha−1 biochar +CI, 20 t ha−1 biochar +CI, 40 t ha−1 biochar +CI, and 40 t ha−1 biochar + flooding irrigation (FI), named CA, CB, CC and FC, respectively) were designed in this study. The results showed that the effect of biochar application on greenhouse gases emissions from paddy fields under controlled irrigation had significant interannual differences. In the first season, CC decreased the global warming potential(GWP) of CH 4 and N 2 O emission, and the CB increased the GWP of CH 4 and N 2 O emission compared to CA, but these differences were not significant. For the second season, CB and CC decreased the GWP of CH 4 and N 2 O emission by 35.7% and 21.5% significantly compared to CA due to the significant mitigation of CH 4 and N 2 O emission. Biochar application significantly increased CH 4 emission and decreased N 2 O emission from paddy fields under flooding irrigation compared to controlled irrigation (CC), which led to the FC's GWP was 1.70 and 5.47 times higher than CC's in the first and second season. In addition, biochar application increased soil organic carbon, dissolved organic carbon and total nitrogen contents of paddy fields under controlled irrigation. And CB and CC increased rice yield by 16.7% and 24.3% and irrigation water productivity by 26.1% and 30.8% compared with CA (mean of two seasons). These results suggest that 20 and 40 t ha−1 biochar can be utilized under controlled irrigation not only for mitigation of CH 4 and N 2 O emission but also to increase rice yield, soil fertility and irrigation water productivity. Therefore, the combination of biochar amendment and controlled irrigation might be a good option for mitigating greenhouse gases emission and realizing the sustainable utilization of soil and water resources of paddy fields in the Taihu Lake Region of China. Highlights • 20 t ha−1 biochar application significantly increased soil DOC, TN, NH 4 +-N and decreased NO 3 −-N concentrations. • Biochar amendments increased rice yield and irrigation water productivity (mean of two rice seasons). • Biochar application combined with controlled irrigation reduced the mean GWP of two rice seasons. [ABSTRACT FROM AUTHOR]

Excessive water and nitrogen (N) input can lead to environmental problems in irrigated areas. By using acidified N loaded biochar with hydrophilic functional groups, it may be possible to reduce water and N usage in rice fields. Therefore, a two–year pot experiment was conducted in northeast China in 2019 and 2020, using a two–factor randomized block design with two irrigation regimes including alternate wet–dry irrigation (I AWD) and continuous flooding irrigation (I CF) as the first factor. The second factor was combinations of NH 4 Cl acidified N–loaded biochar (NB) and N reduction including the control (local practice, 100%NC0), 10 t ha−1 or 20 t ha−1 NB and 25% less N fertilizer (75%NC1, 75%NC2), and 10 t ha−1 or 20 t ha−1 NB and 50% less N fertilizer (50%NC1, 50%NC2). The effects of NB on N concentrations in surface water, water consumption, N use and water productivity (WP), yields and its components under different irrigation regimes were studied. Results show that exposed to 25% and 50% less N input, the grain yield of C2 was 2.96% and 3.74% higher than that of C1, respectively (two–year average), indicating that NB treatment improved the stability of yield. Stable effective panicles and increased grains per panicle were the main reasons of NB for stabilization of rice grain yield. Compared to the 100%NC0 treatment, 75%NC1 and 75%NC2 significantly reduced the total water consumption by 9.6% and 10.4%, respectively, across two irrigation regimes. The I AWD reduced water consumption during all growth stages, resulting in an average reduction of total water consumption by 10.5%. As a result, the 75%NC2 treatment (1.26 g kg−1, 64.76 g pot−1) had the highest statistical WP and yield. I AWD resulted in the highest increase in surface water ammonium N for the 75%NC1 and 75%NC2 treatments. Under I AWD , from 59 to 99 days after transplanting, the surface water ammonium N concentrations of 75%NC1 and 75%NC2 were 9.7% and 22.5% higher than that of 100%NC0, respectively. This effect was most evident in the later growth stages, resulting in a 5.9% increase in panicle N accumulation and a 10.7% increase in root N accumulation. In summary, using 75%NC2 combined with I AWD was the most effective way to save irrigation water by 10.4%, reduce N input by 25%, promote N uptake in panicles and roots while maintaining rice yield stability. • NB (nitrogen-loaded biochar) maintained yield despite 25% less N and 10% less water. • Partial substitution of chemical N with NB to reduce N input and potential loss. • NB released a mount of available N for panicle N accumulation. • NB combined with water-saving irrigation promoted the development of root system. [ABSTRACT FROM AUTHOR]

Common reed (Phragmatic australis) is a vigorous growing wetland plant that forms dense monotypic stands in the Baiyang Lake in the Xiong'an New Area (XNA) of Hebei Province in north China. As a result of untimely harvesting, it has recently developed into an endogenous invasive plant. We assessed the feasibility of reed biochar addition in soils from the ash tree (Fraxinus chinensis) plantation to evaluate the impact of biochar addition on the soil multi-functionality with a bag trial using a greenhouse incubation approach. The soil nutrient turnover was promoted by increasing the abundance of key functional genes of cbbL , nifH , nirK , and pqqC at the early stage. Bacterial taxa tended to be convergent communities irrespective of biochar addition. Path analysis showed that soil variables and bacterial network parameters were positively correlated with soil function in general, whereas alpha diversity has shown an almost opposite relationship. Biochar increased the number of keystone taxa at the treatment's middle stages and improved the network's stability. The whole primary succession of the bacterial communities remarkably homogenous dispersal, contributing to 80% of bacterial community assemblies, which indicates little competitive pressure. Collectively, these results point to a role for biochar addition in enhancing soil functions in ash tree plantations, which can be considered cleaner production to contribute to the greening efforts of the plantation forest sustainability. [Display omitted] • Biochar addition prompts convergent succession. • Biochar (T60) triggered an abrupt transition in the bacterial community assembly. • Keystone taxa of biochar-treated soils differed entirely from their controls. [ABSTRACT FROM AUTHOR]

Soil microbes are of great importance in assessing key ecosystem functions due to their high sensitivity and capacity of providing ecologically relevant information. Benefits of biochar have been demonstrated, including enhancing carbon (C) sequestration and improving soil fertility. Considerable attention has been taken to effects of biochar on soil properties; however, information regarding effects of biochar on seasonal changes of soil microbial activities in field experiments in dryland soil was not well known. Based on a 2-year spring maize ( Zea mays L.) field experiment, we examined changes in soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), urease and alkaline phosphatase activities with three biochar application rates (0, 10, and 30 t ha −1 ) at 0–10 cm and 10–20 cm soil layers in year 2013 and 2014 in silty loam soils on the Loess Plateau in North-Western China. Our results indicated that biochar increased MBC except at silking stage (R1) in 2013, whereas it tended to decrease MBC except at 6-leaf stage (V6) in 2014. MBN in the shallower (0–10 cm) soil layer in 2013 and MBP in 2014 generally increased with biochar rates. Significant positive correlations between microbial biomass and soil water content (SWC) were observed. Results also showed that there were considerable fluctuations in enzymes activities across the growth periods and depths. Biochar significantly increased alkaline phosphatase activities in 2014, and resulted in small but detectable shifts in soil urease activities in both years. These results provided evidence that biochar addition could be an effective management practice for soil microbial activities throughout crop growing season in a dry agricultural system, although soil factors from different climates might lead to some shifts of effects of biochar. [ABSTRACT FROM AUTHOR]

Although biochar has been widely evaluated as a soil-amendment, the response of soil bacterial community to biochar addition, especially after several years’ addition, has not yet been fully understood. Here, we studied the effect of a single addition of biochar on bacterial community compositions in a black soil of northeast China. The biochar was added with dosages of 0%, 2%, 4% and 8% of the total mass of the top 20 cm soils in the spring of 2012, and soil samples were collected seasonally four times in 2014. The abundance and composition of bacterial community were determined using quantitative real-time PCR and Illumina MiSeq sequencing methods, respectively. The results showed that soil pH, moisture, total C, total N, total P, NO 3 − -N, available K and the C/N ratio significantly increased with biochar addition, but that soil bulk density and total K content decreased. The bacterial abundance increased with biochar addition, especially at a higher dosage. The biochar addition increased the alpha-diversity of soil bacterial community and changed the bacterial community compositions. Taxonomic analyses showed that Proteobacteria , Acidobacteria , Actinobacteria , Chloroflexi and Bacteroidetes were the dominant phyla in this study, and the relative abundances of Acidobacteria decreased but Chloroflexi increased with biochar addition. Additionally, biochar addition increased the relative abundances of Bacillus and Pedomicrobium , but decreased the relative abundance of Bradyrhizobium . Canonical correspondence analysis indicated that bacterial community compositions were closely associated with soil parameters such as pH, total C, total N and total K. Given the changes of these soil parameters were highly correlated with the amounts of biochar addition, which suggested that the impacts of long-term biochar amendment on the soil bacterial community were linked to the alteration of soil physiochemical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • DNDC-BC was established on the water balance principle and two-pool biochar model. • DNDC-BC can model GHG, SOC and rice yield of paddy under CI and biochar. • DNDC-BC performed better in simulating GHG and soil moisture than the original one. • Coupling CI and biochar decrease CH 4 and N 2 O emissions, boost SOC and rice yield. • CH 4 and N 2 O emissions from CI paddy are most sensitive to rainfall and irrigation. Simulating the impacts of biochar and controlled irrigation (CI, a water-saving irrigation technology without surface ponding of water) combination on greenhouse gas (GHG) emissions from paddy fields is crucial, however, the original DNDC model is not capable of capturing these management impacts on emissions. In this study, we have created a new modelling approach called DNDC-Biochar-Controlled Irrigation (DNDC-BC) by adding two modules to the original DNDC: the water balance principle, and the two-pool biochar model. The performance of the DNDC-BC was tested and validated using a two-year field experiment, designed with two irrigation treatments (flood irrigation (FI), and CI) and three biochar application rates (0, 20, and 40 t ha−1), carried in the Lake Taihu region, China. Results revealed that the DNDC-BC model performed satisfactorily in simulating impacts of biochar-CI combination on emissions of CH 4 , N 2 O, SOC, and grain yield. The corresponding R2 values of DNDC-BC increased by 22.63%-35.66%, 43.00%-71.26%, 1.06%-60.87% and 15.38%-34.78% compared with those of the original model. Sensitivity analysis for the DNDC-BC showed that CH 4 emissions were most sensitive to rainfall and irrigation; N 2 O emissions were sensitive to rainfall, irrigation and N fertilizer application rate, and SOC was sensitive to biochar application rates. Our results suggest that the combination of biochar- and CI can save water resources and mitigate GHG emissions without detrimental impacts on rice yield. The DNDC-BC can be used to estimate the long-term impacts of biochar-CI combination on GHG emission, crop productivity and climate change. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Hap-doped magnetic biochar was prepared for efficient U(VI) adsorption. • The static saturated adsorption capacity for U(VI) of mNi@Hap@oPMB achieved 1723.5 mg/g. • The removal efficiency was higher than 96.3% after eight cycles. • mNi@Hap@oPMB could be easily recovered after U(VI) adsorption. In this work, three magnetic biochar-supported nano-hydroxyapatite materials were prepared by endowing different magnetic sources, which showed excellent reusability and adsorption ability. It was worth mentioning that the maximum adsorption capacity of the magnetic biochar-hydroxyapatite composite with nickel chloride as the magnetic source reached 1723.5 mg/g and the residual concentration of uranium in the solution could reach the limit standard of China for the discharge of uranium-containing wastewater at low uranium concentration. The removal efficiencies of the composite for uranium in different water systems were all higher than 90.2 %, which reflected the applicability of the composite. Besides, the material was easy to be recycled and reused due to the magnetization. After eight times of reuse, the uranium removal efficiency was still higher than 96.3 % and the magnetism was not significantly weakened. The multiple strong chemical reactions of active sites with uranium, including ion exchange, surface complexation and ionization-precipitation, were the major reason for the excellent adsorption ability. In conclusion, the magnetization of biochar-based materials might be a promising uranium adsorbent, which would open a new direction for the design of biochar-based adsorbents for uranium removal. [ABSTRACT FROM AUTHOR]

Forest soil, especially temperate forest soil, is a prominent sink of atmospheric methane (CH 4). Biochar has been increasingly applied to enhance CH 4 uptake by soil. However, the effect of biochar size and temperature on CH 4 uptake is still largely unknown. A series of incubation experiments were conducted to examine the single and combined effects of biochar addition and temperature (10 °C, 20 °C, and 30 °C) on CH 4 uptake by temperate forest soil in China. The biochar was classified into three particle sizes (<0.1 mm, 0.1–0.5 mm, and 0.5–1 mm) and two application rates (0.73% and 3.65%, m: m). Results showed that the CH 4 uptake was accelerated with the reduced particle sizes and the increased application rates of biochar. This variation was caused by two factors. Firstly, both the reduced particle sizes and increased application rates of biochar decreased the concentration of inorganic N, which had a negative relationship with CH 4 uptake (P < 0.05). Secondly, the reduced particle sizes and increased application rates of biochar promoted both available phosphorus concentration and pH, and these two factors positively correlated with CH 4 uptake (P < 0.05). The increased temperatures produced a negative effect on CH 4 uptake (P < 0.05) due to the increased concentration of inorganic N after rising temperatures. Furthermore, the combined effect of biochar addition and increasing temperatures on CH 4 uptake was antagonistic owing to the reduced Q 10 value of CH 4 uptake after biochar addition. This research highlights the importance of particle size of biochar on CH 4 uptake. Our results also suggest that the positive effect of biochar addition on CH 4 uptake may be dampened by global warming in the near future. • Fine-grain biochar addition absorbed more CH 4 than coarse-grain biochar. • Increased temperatures reduced soil CH 4 uptake. • Combined effect of biochar addition and temperature was antagonistic. • The antagonistic effect was due to the reduced Q 10 of CH 4 uptake. [ABSTRACT FROM AUTHOR]

• Long-term biochar application changed the diversity and composition of rhizobacterial communities. • Long-term biochar application had the potential to improve growth traits of winter wheat. • The rhizobacteria community partly explained the variations in winter wheat development. The use of biochar as a soil amendment has obvious impacts on soil biota and crop productivity. However, the relationship between the rhizosphere bacterial community and crop growth under biochar application is unclear, especially long-term analysis under repeated application of biochar. Thus, we evaluated changes in soil environmental factors, rhizosphere bacterial community structure, and growth traits of winter wheat following the application of different amounts of biochar. Biochar was applied twice in October 2011 and October 2016. The medium or high amount of biochar (10 t ha–1 or 20 t ha−1) application increased the soil moisture, nutrient contents, and urease and catalase activities. The β-diversity of the rhizosphere bacterial community was significantly affected by biochar and its interaction with different growth stages. Biomarkers enriched under biochar addition belonged to phyla comprising Cyanobacteria, Gemmatimonadetes, Nitrospirae, and Chloroflexi. Biochar addition significantly (P < 0.05) improved crop biomass, carbon and nitrogen uptake, and increased the relative crop nitrogen and carbon uptake rates (RNU and RCU) in all growth stages, with the highest dose in a medium amount of biochar (10 t ha−1). Biomarkers enriched under biochar treatments had positive correlations with RNU and RCU, such as Chloroflexales, Thermobioceraceae, and Parviterribacter. Our study furthers the understanding of the association of rhizobacteria community and crop growth under long-term application of biochar. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and lead (Pb) have become serious soil contaminants in China. In this work, we immobilized B. thuringiensis HM-311 (a heavy metal resistant strain) using vinegar residue biochar and hydroxyapatite (HAP) to form Bt HM-311@HAP@biochar calcium alginate beads. In aqueous solution, the beads respectively reduced 1000 mg/L Pb2+ to 14.59 mg/L and 200 mg/L Cd2+ to 5.40 mg/L within 20 h. Furthermore, the results of pot experiment showed that the Bt HM-311@HAP@biochar beads reduced the bioavailability of Pb and Cd in soil. The accumulation of Pb2+ in rice decreased by 39.97% in shoots and 46.40% in roots, while that of Cd2+ decreased by 34.59 and 44.9%, respectively. Similarly, the accumulation of Pb2+ in corn decreased by 40.86% in shoots and 51.34% in roots, while that of Cd2+ decreased by 41.28 and 42.91%, respectively. The beads also increased the microbial community diversity in the rhizosphere soil. These findings indicate that Bt HM-311@HAP@biochar beads may be applicable for the bioremediation of Cd- and Pb-contaminated farmland soil. [Display omitted] • A heavy metal resistant BtHM-311 strain was used to form Bt HM-311@HAP@biochar beads. • The beads reduced the bioavailability of Pb and Cd in soil and promoted crop growth. • The beads increased the microbial community diversity in the rhizosphere soil. [ABSTRACT FROM AUTHOR]

The problem of potentially toxic elements (PTEs) in farmland is a key issue in global pollution prevention and control and has an important impact on environmental safety, human health, and sustainable agricultural development. Based on the climate background of high–latitude cold regions, this study simulated freeze–thaw cycles through indoor tests. Different initial conditions, such as biochar application rates (0%, 1%, 2%) and different initial soil moisture contents (15%, 20%, 25%), were set to explore the morphological changes in cadmium (Cd) and lead (Pb) in soil and the response relationship to the changes in soil physicochemical properties. The results indicate that soil pH decreases during freeze–thaw cycles, and soil alkalinity increases with increasing biochar content. Freeze–thaw cycles caused the total amount of PTEs to have a U–shaped distribution, and the amount of PTEs in the soluble (SOL) and reducible (RED) fraction increased by 0.28–56.19%. Biochar reduced the amount of Cd and Pb migration in the soil, and an increase in soil moisture content reduced the availability of Cd and Pb in the soil. Freezing and thawing damaged the soil structure, and biochar reduced the fractionation of small particle aggregates by enhancing the stability of soil aggregates, thereby reducing the soil's ability to adsorb Cd and Pb. In summary, for farmland soil remediation and pollution control, the application of biochar has a certain ability to optimize soil properties. Considering the distribution of PTEs in the soil and the physicochemical properties of the soil, the application of 1% biochar to soil with a 20% moisture content is optimal for regulating seasonally frozen soil remediation. [Display omitted] • Exploring reasonable soil initial conditions to reduce soil Cd and Pb pollution. • Seek the distribution law of Cd and Pb in soil aggregates. • The favorable mechanisms for mitigating Cd and Pb pollution in soil are refined. • Freeze-thaw cycles alter the composition and distribution of Cd and Pb in soil. • Biochar as a new curing agent to reduce the toxic forms of Cd and Pb in soil. [ABSTRACT FROM AUTHOR]

Adding biochar to agricultural soils is an innovative method to improve soil fertility and sequester recalcitrant carbon. However, effects of biochar application on soil nitrogen balance under dryland conditions have not been assessed. In this study, we applied biochar at four rates [no biochar (B0), 5 t ha−1 (B5), 10 t ha−1 (B10), and 20 t ha−1 (B20)] to a rainfed winter-wheat agroecosystem on the Loess Plateau in China in October 2011 and 2016. Biochar application at the low and medium rates (5 and 10 t ha−1) reduced nitrogen losses through NH 3 volatilization and N 2 O emissions by 9.23–15.41 % and 2.77–10.44 %, respectively, in all the three experimental study seasons from 2016 to 2019. In addition, biochar application reduced soil NO 3 −-N leaching by 14.71–37.96 % within 100 cm soil depth in a dose-dependent manner. The reduced nitrogen losses increased the retention of soil total nitrogen in the 0–60 cm soil layer (particularly in the 0–20 cm layer). Biochar application increased the crop and grain nitrogen uptake by 5.07–17.77 % and 1.73–21.74 %, respectively, and this effect was more pronounced at higher biochar application rates (10 and 20 t ha−1). Estimation of N inputs and outputs indicated that biochar application significantly (P < 0.05) increased the mean soil nitrogen balance by 52.09–116.84 % through decreased nitrogen losses and increased soil nitrogen retention. The results indicate that biochar application at 10 t ha−1 could be recommended as the optimal dose for sustainable nitrogen management in rainfed wheat cropping ecosystems on the Loess Plateau. • Biochar application reduces N losses intensity. • Biochar application increased the soil N retention and crop N uptake. • Biochar application significantly improved the mean soil N balance. • 10 t biochar ha−1 should be recommended as the optimal dose for N sustainability in agroecosystem. [ABSTRACT FROM AUTHOR]

In China, a large amount of distiller's grains produced by liquor production need to be effectively utilized. Herein, wet-process phosphoric acid was used to treat distiller's grains to achieve the material exchange between them. And water-soluble suspended fertilizer products with sufficient P 2 O 5 (34.57%), N (7.31%), chelated trace elements (4.84%), amino acids (0.42%) and carbohydrates (2.73%) can be prepared by adding 8% EDTA (w: w) in the recovered phosphoric acid. High concentration, high Zeta potential (52.46 mV) and good thixotropy made it resistant to storage and transportation (>30 day). In addition, the residual solid residue capturing sufficient P, Fe, Al and Mg was pyrolyzed into biochar sustained-release phosphate fertilizer. TG-FTIR, in-situ DRAFTS, XRD, Raman, and SEM-EDS demonstrated that polyphosphates and biochar skeleton can be suitably synthesized simultaneously to achieve in situ binding at 400 °C. Long-term observation by ion chromatography showed that polyphosphate could be slowly released from the biochar structure and gradually converted to Ortho-P through hydrolysis reaction. In water, Ortho-P, Fe, Al and Mg can slowly release out from biochar fertilizer within 60 days, whose maximum release rates were 91.72%, 61.5%, 83.5% and 83.6%, respectively. It was confirmed that biochar structure was innovatively combined with polyphosphate to realize the slow-release characteristics and activate impurity ions to become microelement nutrients. This study proposed a clean production strategy to effectively utilize biomass waste residue, improve the utilization rate of phosphorus and impurity ions, and show the potential of carbon sequestration. [Display omitted] • Wet-process phosphoric acid combined with biomass waste to produce two fertilizers. • Biochar fertilizer synthesized had multi-nutrients slow-release characteristics. • Impurity metal ions in wet-process phosphoric acid were utilized. • Combination of biochar and polyphosphate enhanced the sustained release effect. • High concentration suspension fertilizer had thixotropy and storage resistance. [ABSTRACT FROM AUTHOR]

The disposal and utilization of antibiotic residues (ARs) are a serious concern and have been identified as “a hazardous material” in China because of the residual antibiotic. However, little attention was paid to the potential environmental risk of the persistence of toxic heavy metals in those residues. Pyrolysis is an effective technology that used to reduce solid waste. Thus, in order to systematically investigate the influence of pyrolysis temperature and residence time on physicochemical characteristics, heavy metal speciation and bioavaibility in ARs derived biochars, ARs was pyrolyzed at different temperatures (300–700 °C) and residence time (1 and 2 h). The residue and biochar characteristics were characterized with a thermogravimetric analyzer, element analyzer, scanning electron microscopy, and Brunauer–Emmerr–Teller (BET) methods. Zn species in the biochars were determined with modified BCR sequential extraction procedure. The bioavailability of Zn in biochars and the resulted phytotoxicity were measured through a phytotoxicity test. Results indicated that both temperature and residence time have effects on biochar physiochemical properties, Zn speciation and bioavailability. Residual antibiotic was eliminated, and Zn was enriched and stabilized through pyrolysis. Zn bioavailability and phytotoxicity decreased with the increasing temperature and residence time. A temperature at 500 °C was optimal for this residue disposal. The results obtained in this study would enhance our knowledge on heavy metal transformation in pyrolysis and would be useful in designing an environment friendly approach to utilize this Zn-rich AR or other biowaste with similar characteristics. [ABSTRACT FROM AUTHOR]

This preliminary study examines the feasibility and applications of pyrolysis and biochar in China to understand issues about bioenergy generation, agricultural cost savings and enhancement of atmospheric quality. Multiple agricultural and animal wastes are analyzed and quantitative measures of economic and environmental benefits are provided. The Poyang Lake, one of the most important clean water lakes in China, is examined to see how pyrolysis and biochar applications can be beneficiary to farmers and society in terms of the economic and greenhouse gas values. Rice straw, corn stover, poplar, orchard wastes, animal wastes and open pasture wastes are primary feedstocks for fast and slow pyrolysis. The results show that both fast and slow pyrolysis are profitable under current situations where corn stover-based pyrolysis yields the highest economic benefits but that of animal wastes-based can offset more GHG emissions. Rice straw yields a loss but it can still be a potential choice since the material is the most popular in study area. Sensitivity analysis is provided to understand the changes of economic and environmental benefits under various market conditions and the results indicate that in general, significant profits of pyrolysis and biochar application bring additional margin of safety and therefore, pyrolysis and biochar does not incur a loss unless input costs increase more than 53% to 64%. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to determine the effects of nitrogen (N) fertilization and biochar addition on the net global warming potential (net GWP), greenhouse gas intensity (GHGI) and net ecosystem economic budget (NEEB). These experiments were conducted in an intensive vegetable field with 4 consecutive vegetable crops in 2012 and 2013 in southeastern China. The experiment was conducted with a 3 2 factorial design in triplicate at N fertilizer rates of 0, 1475, 1967 kg N ha −1 and biochar rates of 0, 20, and 40 t ha −1 . Although CH 4 emissions were not obviously affected by N fertilization, N 2 O emissions increased by 27.2–116.2% and the net GWP increased by 30.6–307.2%. Consequently, the GHGI increased significantly, but vegetable yield and the NEEB did not improve. Furthermore, biochar amendments did not significantly influence CH 4 emissions, but significantly decreased the N 2 O emissions by 1.7–25.4%, the net GWP by 89.6–700.5%, and the GHGI by 89.5–644.8%. In addition, vegetable yields significantly increased by 2.1–74.1%, which improved the NEEB. Thus, N fertilization did not increase vegetable yields or the NEEB. However, N fertilization did increase the net GWP and GHGI. In contrast, biochar additions resulted in lower N 2 O emissions and net GWP and GHGI, but increased vegetable yield and the NEEB in the intensive vegetable production system. Therefore, appropriate biochar amendment should be studied to combat changing climate and to improve the economic profits of vegetable production. [ABSTRACT FROM AUTHOR]

Biochar is an efficient amendment to improve soil quality and crop productivity, but the potential of biochar as a substitute for chemical fertilizers is still unknown. Here we conducted a 6-year field experiment to investigate how partial substitution of biochar to NPK fertilizers affect soil quality and rice yield in the northeast of China. The experiment included three treatments: Control (B0: NPK fertilizers only: 240 kg N ha−1, 52 kg P ha−1, and 100 kg K ha−1); Low-input biochar (B1.5: 95% N, 89% P, 75% K + 1.5 t biochar ha−1 year−1); and High-input biochar (B3.0: 90% N, 78% P, 50% K + 3.0 t biochar ha−1 year−1). The amounts of NPK application in the biochar treatments were determined according to an equivalent method. We evaluated the soil pore structure characteristics via a CT technology, and investigated soil nutrients, plant biomass, root growth, and grain yields. The results showed that, after the 6-year application, the soil pore structure and rice productivity of B1.5 were significantly improved in compared to those of B0 and B3.0. B1.5 had similar soil available NPK contents, but 6.6% higher rice yield as compared to B0, because of increased root length density (33.2%) and aboveground biomass (10.2%). B1.5 also increased soil macroporosity (>100 μm) (141.4%), fraction dimension (8.4%), and pore connectivity (16.6%) in compared with those of B0. However, B3.0 showed the lowest rice yield due to lower soil available N content (19.2%), macroporosity (28.5%), fraction dimension (5.5%), and pore connectivity (85.3%) than B0. This study demonstrated that a moderate NPK fertilizer replacement by biochar could be an effective practice that improves soil quality, increases rice growth and yield, and reduces the input of chemical fertilizers for rice production. [Display omitted] • This study was based on a 6-year biochar application experiment in paddy soil. • 1.5 t ha−1 of biochar maintained sufficient soil nutrients and improved pore structure. • 1.5 t ha−1 of biochar increased rice productivity, but inverse in 3.0 t ha−1. [ABSTRACT FROM AUTHOR]

The increasing pressures of global warming, population growth and epidemic occurrence are causing challenges in meeting the growing requirements for water, energy and food. In particular, the contradiction between the supply and demand for water, food, and energy is exacerbated by inefficient resource utilization and carbon emission increase. Incorporation of the interlinked aspects of water, energy, food and carbon emissions from agricultural systems into one water-food-energy-carbon nexus facilitates integrated resource management. Biochar application to farmland is a potential strategy for carbon management and agricultural productivity improvement. The integration of biochar systems and the water-food-energy-carbon nexus is an efficient and coordinated alternative method for sustainable agricultural management and a crucial strategy for addressing water, energy and food security issues. Accordingly, this paper proposes an approach for the synergistic regulation of water, land, energy, and carbon emissions in a circular agricultural system by balancing water supply and demand, land allocation, electricity consumption, and economic upgrading principles. A two-stage circular agriculture framework is constructed, with biochar and electricity generated from agricultural residues at the first stage and employed at the second stage. Economic-environmental-energy harmonization is considered in the methodology, and the agrotechnical potential of biochar is quantified via crop yield increase and greenhouse gas emission reduction functions. This approach can assist decision makers in providing the best policy options given certain agricultural resources to achieve the maximum economic performance of the system while minimizing environmental side effects. In this paper, the model framework is applied to the Sanjiang Plain in northeastern China to verify the feasibility of the approach. The results indicate that the external electricity demand is reduced by 87.8% due to the generation of biofuels. Cropland greenhouse gas emissions are reduced by 34.09%–67.06% via the application of biochar. This study proposes an optimization method with important implications for the improvement of regional cropland management techniques and development of sustainable circular agriculture. This methodology can be extended to other agriculture-centered regions with limited resources and environmental problems. • Carbon cycle is integrated in agricultural water-food-energy-carbon (AWFEC) nexus. • An AWFEC nexus based model is developed for agricultural resources recycling. • Biochar and electricity are optimized sustainably for circular agriculture. • Analysis of resources recycling on economic-environmental balance is performed. [ABSTRACT FROM AUTHOR]

Spiramycin (SPI) fermentation residue (SFR) is classified as hazardous waste in China because of the residual antibiotics in it. SFR disposal in the traditional way is costly and wasteful of resources. In this study, pyrolysis method was adopted to covert SFR to biochar for SPI removal from wastewater, and the SPI adsorption performance was investigated. The results showed that the optimal pyrolysis temperature was 700 °C as the prepared biochar BC700 exhibited the highest SPI removal efficiency. The specific surface area of BC700 was 451.68 m2/g, and the maximum adsorption capacity was 147.28 mg/g. The adsorption mechanism involved electrostatic interaction, pore filling, π-π interaction, hydrogen bonding, and the participation of C–C and O–C O functional groups in the adsorption. No residual SPI was detected in BC700 indicating the detoxification of SFR was achieved. Moreover, after recycling for 5 times, the SPI removal efficiency was still higher than 80.0%. Therefore, this study could provide a promising method for SFR disposal. [Display omitted] • Spiramycin fermentation residue (SFR) detoxification attained by pyrolysis. • The biochar prepared under 700 °C was the best for SPI removal. • 100% of SPI can be removed from wastewater when the BC700 dosage was 2.0 g/L. • The maximum SPI adsorption capacity of BC700 was 147.28 mg/g. • After being recycled for 5 times, SPI removal rate was still higher than 80.0%. [ABSTRACT FROM AUTHOR]

It is of great significance to explore the remediation pattern in actual heavy metal (HM) contaminated sites. The field trial was carried out to research the remediation effect of biochar near a lead-zinc smelter in Feng County, China, under the rotation condition of different crops. This kind of cultivation mode is very representative in northern of China. And the pattern of production and restoration is suitable for scarce land resources and large food demand in China. The changes of soil physiochemical properties with the biochar addition, crop growth and the accumulated HMs by crops were focused on. The results showed the biochar application was excellent in improving soil nutrient elements and crop growth. The contents of TK were more obvious than those of TN and TP, with an increase of 2.6%–28.2% compared with the controls (without the addition of biochar). The yield of first season crops, i.e., soybean and corn, increased by 30%–42% and 34%–61%, respectively, and the second season crops, i.e., rape and wheat, with the increment of 25%–41% and 9%–29%, respectively. The availability forms of Cd and Pb decreased by 1.07–10.0% and 2.92–8.35%, respectively. While the improvement on the status of the HMs accumulated by crops was disappointing. The contents of HMs accumulated by crops increased to varying degrees (e.g., Pb and Zn in root, Cu and Pb in grain, and Cd in stems and leaves). Moreover, the concentrations of HMs in seeds of crops were higher than the limited levels given by the Chinese directive. Considering the results of the study and food safety, it is suggested to change the nature of the land around the smelter into woodland or construction land to prohibit the cultivation of food crops in this area. [Display omitted] • The effect of biochar on the HM availability under rotation pattern was explored. • The contents of THC had a significant relationship with the dose of biochar. • Biochar has more obvious effects on immobilizing Cu, Pb and Cd than Zn. • The factors controlling the changes of samples in the same season were similar. [ABSTRACT FROM AUTHOR]

Worldwide, massive amounts of food waste have been generated at increasingly accelerated rates, posing potentially great risks to the environment. Shifting traditional waste treatment to a sustainable bioeconomy thus challenges food chain management worldwide. In this study, food waste was copyrolyzed with rice husk to produce biochar with a pilot-scale industrialized system. The efficiency of the material conversion and the properties and functions of the produced biochars as well as the potential environmental impacts of pyrolysis were evaluated using in situ measurements, physico-chemical characterization and in vitro (pot) experiments with biochar. The results showed that the emissions of potential toxic compounds and metals from the pyrolysis system were within the guideline limits under the legislation of China or the EU commission. On average, biochar yielded approximately 20% of feedstock and contained a total organic carbon content of 433 g kg−1. In the pot experiment, Chinese cabbage yield and quality were significantly improved, and the plant uptake of heavy metals was significantly reduced in soil amended with food waste biochar compared to no biochar amendment. Furthermore, the food waste biochar was blended with mineral nutrients to create a biochar based compounded N-P-K fertilizer. Application of the biochar based compound fertilizer exerted a significant positive effect on cabbage growth and nutrient use efficiency relative to a conventional mineral compound fertilizer. For per tonne of dry mass of food waste, copyrolysis costed less than 60 USD but gained a gross profit of more than 30 USD. Therefore, the copyrolysis of food waste with crop residues could be applicable to the safe recycling of food waste into value added products to raise agricultural production. [Display omitted] • A pilot-scale copyrolysis system was used to convert food waste into biochar. • The concentrations of potential toxic elements in flue gas was negligible. • Food waste biochar (BC) and biochar compound fertilizer (BCF) was analyzed. • BC and BCF significantly improved the yield and quality of Chinese cabbage. • The average cost and gross profit were 54.5 and 32.9 USD per tonne. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly efficient exfoliated biochar containing thin layered nanosheets was synthesized. • Exfoliated biochar showed higher BET surface area 421.24 m2g−1 than pristine biochar 3.81 m2g−1. • A higher Q max of Tl(I) was observed than previously reported adsorbents. • Exfoliated biochar removed ∼ 90% of T1(I) in complex river water under real scale study. Tailoring the pathways to synthesize efficient biochars for pollutant adsorption has received extensive attention. Here, we synthesized highly efficient exfoliated biochar having thin layered nanosheets in its structure from agricultural wastes (wheat straw) by an innovative method involving biomass pre-treatment, nitrogen pyrolysis, and a flash heat exfoliation for thallium(I) removal from contaminated waters. Exfoliated biochar with nanosheets in its structure (EBNs) exhibited an open porous structure with a BET surface area 421.24 m2 g−1 and pore size 3.98 nm, much higher than the 3.81 m2 g−1 and 2.05 nm, respectively, of pristine wheat-straw biochar (PB). Using these materials for the adsorption of T1(I) revealed that the EBNs had a maximum adsorption capacity of 382.38 mg g−1 at pH 7.0, over 9 times higher than the PB. The adsorption kinetics and isotherm data were better fitted by pseudo-second order and Langmuir models. Moreover, EBNs retained its selective adsorption capacity for T1(I) in the presence of competing ions (Ca2+, Mg2+, K+, Cu2+, Zn2+) and organic materials (humic acid, fulvic acid). Also, high regeneration ability (>93%) of EBNs was noted for five consecutive adsorption–desorption cycles. The efficiency of EBNs was also tested in river water (sampled from Bahe river, Xi'an, West China) spiked with T1(I) where it removed ∼ 90% of T1(I). These findings highlight the potential of EBNs for practical water treatment applications by developing the biochar nanosheets from agricultural wastes and provide insights into a new strategy to develop cost-effective carbon-based nanomaterials for wastewater treatment. [ABSTRACT FROM AUTHOR]

Biochar can significantly enhance soil organic carbon (SOC) and crop yield, and it is therefore the preferred material for soil improvement in medium-low yield fields. In this study, a field experiment was designed to explore the impacts of biochar application on SOC content and fraction composition. Results indicated that incorporation of biochar into soil increased the SOC content by 26.9%–65.3% in the surface layer (0–10 cm) and 30.3%–63.0% in the subsurface layer (10–20 cm) of soil, while water-soluble organic carbon (WSOC) of the two layers was increased by 2.2–40.0% and 2.3–39.8%, respectively. Microbial biomass carbon decreased under conventional nitrogen treatments and increased with biochar addition under increased nitrogen application. The C:N value increased with biochar application, while the water-soluble C:N value of soil applied with 30 t ha−1 biochar was lower than that of soil applied with 15 t ha−1 biochar, both in the two tested soil layers. Wheat yield is evidently correlated with SOC, with the correlation coefficients of 0.919 and 0.952 in the surface and subsurface soil layers (P < 0.01), respectively. Particularly, increasing fulvic and humic acid-like compounds of WSOC promoted the bioavailability of nutrient elements, thereby increasing the crop yields. Therefore, biochar application is an effective means to fertilize middle-low yield soils through increasing SOC sequestration and nutrient reserves, or adjusting soil C:N value to a proper range, thereby reducing nutrient loss and increasing wheat yield. [Display omitted] • Biochar addition increased SOC and WSOC in medium-low-yield farmland. • Biochar combination nitrogen fertilizer application changed Soil C:N and affected wheat yield. • Biochar application increased fulvic and humic acid-like components as detected by EEM analysis. • Biochar is a carbon-rich production and widely used in improving soil quality and carbon sequestration. [ABSTRACT FROM AUTHOR]

Coastal salt marshes have been significantly suffering degradation worldwide, turning these wetlands from carbon sink to carbon source. The additions of carbon-rich substrates in degraded coastal wetlands have been documented to alleviate this situation; however, the microbial responses as well as their carbon metabolisms to the input are not well explored. Here, we investigated the effects of different addition levels (0.1%, 1%, and 3%) of reed straw and biochar addition on microbial communities (bacteria and fungi) and predicted functions of carbon metabolism in degraded coastal salt marshes. The effects of the carbon-rich substrates on microbial communities are more pronounced under 3% of reed straw and biochar than other levels, straw increased opportunistic bacteria (e.g., Bacillus and Cellvibrionaceae) and biochar increased low carbon turnover bacteria (e.g., Acidobacteria and Actinobacteria). The addition of higher doses of reed straw and biochar promoted the carbon metabolism of soil bacteria as predicted by the PICRUSt 2. Interestingly, the addition of reed straw increased the abundance involved in fungal carbon metabolism, but this was not the case for the biochar input. The addition of reed straw and biochar promoted the growth of some bacteria (e.g., Rhizobiales and Bacillus) that are beneficial to plant growth, and decreased some fungal pathogen (e.g., Magnaporthaceae and Phaeosphaeria). Our findings revealed that the carbon-rich substrates addition can reshape the microbial structure and shift their carbon metabolisms, specially, biochar has a higher potential to improve the ecosystem services, such as blue carbon sequestration, of these degraded coastal salt marshes. [Display omitted] • Higher doses of carbon-rich substrate addition reduced microbial diversity. • Adding reed straw increased copiotrophic bacteria but decreased oligotrophic bacteria. • Higher doses of carbon-rich substrate addition promoted bacteria carbon metabolism. • A lower dose of biochar input decreased the carbon metabolism of soil fungi. [ABSTRACT FROM AUTHOR]

The situation of imbalance application of nitrogenous fertilizers in maize production is a serious issue in China, and excessive nitrogen (N) application is hazardous to sustainable agricultural production and environment. In this experiment, two biochar levels (C0: 0, C1: 2 %), three different N rates (N1: 50, N2: 100, and N3: 200 mg kg−1), and two fertilization methods (T: traditional N fertilizer application mode and D: deep N fertilizer placement mode) were set up to study the response of different treatments on maize yield, N uptake, and N use efficiency. Herein, we found that fresh and dry biomasses were increased by 292 % and 283 % under C1N3 treatment with the deep application of N fertilizer compared to the control treatment (without nitrogen fertilizers and biochar). According to structural equation modeling (SEM), soil physical and chemical properties, N component and C component in different soil layers were associated with biochar and N fertilizer treatment, especially at 20–40 depth. The combination of N fertilizer and biochar application promoted the effects of biochar on the improving NUE of plants. The biochar alleviated the loss of soil nitrogen (from 52.00 to 25.94 %) under traditional N fertilizer application. Overall, excessive input of N fertilizer not only promotes the growth of crops but also causes a waste of resources and environmental pollution. We suggest that combined application of biochar and N fertilizer could significantly reduce N loss, and improve root growth and N uptake, resulting in improving NUE by improving soil environment (pH, SOM, EC) and adjusting soil C/N component. [Display omitted] • Biochar application could improve root growth and nitrogen uptake by adjusting soil C/N component. • The biochar could greatly alleviate the loss of soil nitrogen under traditional N fertilizer application mode. • Combing application of N fertilizer and biochar had more better effects on improving NUE of plant. [ABSTRACT FROM AUTHOR]

Rice, as a dominant crop in China and Asia, can be a major route of methylmercury (MeHg) exposure for humans in inland China, especially in those living in mercury (Hg) polluted areas. Soil is the most prominent MeHg accumulation source for rice grains. The development of management practices to reduce MeHg in rice grains is crucial. This study explored the mitigation effect of biochar (BC) and sodium selenite-amended biochar (BC + Se) on MeHg production in paddy soil and accumulation in rice. Mercury-contaminated soil was treated with 1% and 5% of both BC and BC + Se. Soil MeHg concentration slightly increased under 1% BC/BC + Se compared to control soil but decreased at the rate of 5%. Moreover, soil phytoavailable MeHg (P–MeHg) diminished as the amount of Se-amended BC increased. BC + Se effectively mitigated MeHg accumulation in rice grains. The highest average contents of MeHg and inorganic Hg (IHg) in rice seeds were found in the control samples, followed by the 1%-BC, 5%-BC, 1%-BC + Se, and 5%-BC + Se samples. Under the 5%-BC + Se treatment, rice MeHg levels were reduced significantly (94%) compared to the control, and P–MeHg concentrations in soil were lower than all the other experimental groups throughout the rice-growing season. These results demonstrate the effectiveness of BC + Se in reducing MeHg and IHg accumulation in rice and could be employed for remediation of Hg polluted paddies. [Display omitted] • Investigated the influence of biochar and Se-amended biochar on MeHg uptake in rice. • Addition of biochar in soil increase MeHg level while phytoavailable MeHg decrease. • Se-amended biochar reduces phytoavailable MeHg and decreases MeHg levels in rice. • Se-amended biochar more effectively than biochar in mitigating Hg uptake in rice. [ABSTRACT FROM AUTHOR]

Representing the staple crop for half of the world population, rice can accumulate high levels of cadmium (Cd) in its grain, posing concerns on food safety. Different soil amendments have been proposed to decrease Cd accumulation in rice grain by either decreasing soil Cd availability, introducing competitive ions on Cd uptake, or down-regulating the expression of transporters for Cd uptake. However, the effectiveness of soil amendments applied alone or in combinations needs to be tested under field conditions. Here, we present results of field trials with two rice cultivars differing in Cd accumulation grown at three field sites in southern China in two years, to investigate the effects of two Mn-containing soil amendments (MnO 2 , Mn-loaded biochar (MB)), Si fertilizer (Si), limestone, and K 2 SO 4 , as well as interactions among MnO 2 , Si, and limestone on decreasing Cd accumulation in rice grain. We found that single applications of MnO 2 or MB to acidic soils low in Mn decreased grain Cd concentrations by 44–53 % or 78–82 %, respectively, over two years without decrease in performance. These effects were comparable to or greater than those induced by limestone liming alone (45–62 %). Strong interactions between MnO 2 and limestone resulting from their influence on soil extractable Cd and Mn led to non-additive effects on lowering grain Cd. MB addition minimized grain Cd concentrations, primarily by increasing extractable and dissolved Mn concentrations, but also by decreasing Cd extractability in soil. In comparison, Si and K 2 SO 4 amendments affected grain Cd levels only weakly. We conclude that the amendments that decrease labile Cd and increase labile Mn in soils are most effective at reducing Cd accumulation in rice grain, thus contributing to food safety. [Display omitted] • Soil Mn amendment can effectively decrease Cd accumulation in rice grain on acidic soils low in Mn. • Non-additive interactions between soil liming and MnO 2 amendment on grain Cd were discovered using a factorial treatment design. • Mn-loaded biochar was most effective in decreasing grain Cd by simultaneously increasing extractable Mn and decreasing extractable Cd of field-moist soils at rice grain-filling stage. [ABSTRACT FROM AUTHOR]

The plant Phytolacca americana L. simultaneously hyperaccumulates manganese (Mn) and rare earth elements (REEs), but the underlying mechanisms are largely unknown. In this study, P. americana and the corresponding rhizosphere soil samples were collected from an ion-adsorption REE mine area in China, and the elemental composition and soil properties were analyzed in order to explore the relationship between metal accumulation and soil properties. The results show that P. americana accumulates high concentrations of REEs (up to 1040 mg kg−1), Mn (up to 10400 mg kg−1) and aluminum (Al) (up to 5960 mg kg−1) in leaves. The REE concentrations in leaves were positively correlated with those of Al, Fe and Zn, while light REE concentrations were negatively correlated with P concentrations (p < 0.05). The soil properties explained 81.7%, 72.9% and 67.1% of REEs, Mn and Al accumulated in P. americana , respectively. The variation of REE accumulation in P. americana was primarily explained by plant available P (24.4%), pH (12.9%), TOC (9.4%) and total P (7.7%). The accumulation of Mn was primarily explained by plant available REEs (42.9%) and available Al (13.1%) while Al in P. americana was primarily explained by soil pH (14.4%). This study suggests the potential by regulation of soil properties in improving the efficiency of phytoextraction for REEs by hyperaccumulators. [Display omitted] • Phytolacca americana is a co-hyperaccumulator of REEs, Mn and Al. • Foliar REE concentrations are positively correlated with Al, Fe and Zn. • Plant available P is an important factor affecting foliar REE accumulation. • P deficiency-induced organic acid secretion contributes to the accumulation of REEs. [ABSTRACT FROM AUTHOR]

Red mud (RM) is an industrial waste that needs proper disposal without incurring hazards to the environment. In this study, we used RM and corn straw (CS) to fabricate functional biochar composites (FBCs) via pyrolysis. We fully characterized the changes in morphology and composition on the preparation of FBCs at different pyrolytic temperature and the gaseous products during pyrolysis. It was found that a porous structure was generated on CS, endowing FBCs with the ability to remove dyes in water. Moreover, CaO was created through the decomposition of CaCO 3 in RM at ~700 °C, suggesting that FBCs could be used to neutralize the acidic wastewater. Hence, FBCs showed excellent performance in treating acidic dye wastewater, a common industrial wastewater with high contents of acid and dye and for which disposal is laborious. Additionally, FBCs exhibited magnetism because magnetic zero-valent iron was generated by the reduction of ferric oxide in RM with the CS gaseous product (CO) during pyrolysis. This work provided a dual-win strategy for waste recyclability and wastewater treatment, and the proposed method may have potential applications. [Display omitted] • FBC was fabricated from solid wastes of red mud and corn straw via pyrolysis. • The mechanism of structural transformation was investigated. • FBC could remove dyes and alleviate acid upon treatment with acidic dye wastewater. • FBC was collectable by magnet after wastewater treatment. • A dual-win strategy to recycle solid wastes and remedy acidic dye wastewater. [ABSTRACT FROM AUTHOR]

Biochar is often applied to paddy soils as a soil improver, as it retains nutrients and increases C sequestration; as such, it is a tool in the move towards C-neutral agriculture. Nitrogen (N) fertilizers have been excessively applied to rice paddies, particularly in small farms in China, because N is the major limiting factor for rice production. In paddy soils, dynamic changes in iron (Fe) continuously affect soil emissions of methane (CH 4) and carbon dioxide (CO 2); however, the links between Fe dynamics and greenhouse gas emissions, dissolved organic carbon (DOC), and rice yields following application of biochar remain unclear. The aims of this study were to examine the effects of two rates of nitrogen (N)-enriched biochar (4 and 8 t ha−1 y−1) on paddy soil C emissions and storage, rice yields, and Fe dynamics in subtropical early and late rice growing seasons. Field application of N-enriched biochar at 4 and 8 t ha−1 increased C emissions in early and late rice, whereas application at 4 t ha−1 significantly increased rice yields. The results of a culture experiment and a field experiment showed that the application of N-enriched biochar increased soil Fe 2+ concentration. There were positive correlations between Fe 2+ concentrations and soil CO 2 , CH 4 , and total C emissions, and with soil DOC concentrations. On the other way around, these correlations were negative for soil Fe 3+ concentrations. In the soil culture experiment, under the exclusion of plant growth, N-enriched biochar reduced cumulative soil emissions of CH 4 and CO 2. We conclude that moderate inputs of N-rich biochar (4 t ha−1) increase rice crop yield and biomass, and soil DOC concentrations, while moderating soil cumulative C emissions, in part, by the impacts of biochar on soil Fe dynamics. We suggest that water management strategies, such as dry-wet cycles, should be employed in rice cultivation to increase Fe2+ oxidation for the inhibition of soil CH 4 and CO 2 production. Overall, we showed that application of 4 t ha−1 of N-enriched biochar may represent a potential tool to improve sustainable food production and security, while minimizing negative environmental impacts. [Display omitted] • Application of N-enriched biochar favors the soil conversion of Fe3+ to Fe2+. • Can be a tool to improve fertilization efficiency and yield in a C neutral scenario. • At 8 t ha−1 promoted gaseous C emissions in paddy soil without yield improvement. • At 4 t ha−1 increased yield and decreased the C gas emissions in culture experiments. • Fe2+ content was positively correlated with DOC content, CO 2 and CH 4 emissions. [ABSTRACT FROM AUTHOR]

Soil pollution, caused by heavy metals, is an environmental problem that requires an urgent solution in China. Chemical passivation is a technology that uses various passivators to reduce the availability of heavy metals in soil and realize the remediation of contaminated soil. In this study, we examined the effects of fly ash (FA), alkali-fused fly ash (AFFA), swine manure biochar (SB), and modifying biochar (MB) on the leachability of Cu, Zn, Pb, and Cd via soil culture experiments. The results showed that the addition of AFFA, SB, and MB significantly reduced the extractable contents of Cu, Pb, and Cd in the soil. AFFA and MB had the best passivation effect, followed by SB and FA. The passivation effect on Pb was the best, followed by that on Cu and Cd. AFFA modification significantly improved the passivation effect of MB on Cu, Pb, and Cd in composite contaminated soil. With the addition of 3% MB, the Pb, Cu, and Cd extracted by TCLP decreased by 95.7, 74.1, and 59.1%, respectively. Correlation analysis, Fourier transform infrared spectrometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy showed that the passivation mechanism is mainly due to an increase in the soil pH, silicate content, and cohesiveness. The soil culture experiments in this study proved that MB is a low-cost and highly efficient organic-inorganic composite passivator for multi-metal contaminated soils. [Display omitted] • New organic-inorganic composite passivator synthesized by alkali-fused fly ash and swine manure. • Modifying biochar has a good passivation effect on Pb, Cu, and Cd in polluted soil. • Heavy metal passivation via alkalinity and silicate introduced by alkali-fused fly ash. • Modifying biochar an efficient passivator for multi-metal contaminated soil. [ABSTRACT FROM AUTHOR]

Biochar, as a valuable and eco-friendly material generated from greenwaste, has a potential to mitigate CH 4 emission in rice paddy soil. However, the response of methanogenesis and associated archaeal community in paddy soil to biochar amendment remains controversial. In this study, we explored the effect of three different biochars (derived from rice straw, orange peel or bamboo powder, respectively) on CH 4 emission and associated archaeal microbial community in paddy soil of southern China within 90 days of anaerobic incubation. Results showed that biochar amendment overall inhibited CH 4 emission in paddy soil. Significant decrease of α-diversity of archaeal community was observed in all samples in the end of incubation as revealed by 16S rRNA gene sequencing, and the addition of biochars mitigated the loss of archaeal biodiversity in paddy soil. Incubation time was found to be the major driver for the succession of archaeal community. Besides, Methanosaeta , Methanocella , Methanobacterium and Methanosarcina were mainly responsible for CH 4 production. In addition, biochars had no significant effect on altering relative abundance of methanogens. Overall, our study demonstrated that the addition of three different types of biochar reduced methane emission and total archaeal diversity, while caused no significant change in methanogenic communities in paddy soil. • The addition of three different types of biochar reduced CH 4 emission in paddy soil. • Biochars mitigated the loss of soil archaeal biodiversity during anaerobic incubation. • Incubation time was the major driver for the succession of archaeal community. • Methanosaeta , Methanocella , Methanobacterium and Methanosarcina were mainly responsible for CH 4 production. • Biochars amendment had little effect on the succession of soil methanogens. [ABSTRACT FROM AUTHOR]

Oiltea camellia shells are a substantial agricultural waste in southern China, but their resource utilization has not been given due attention. In this study, we prepared oiltea camellia shell biochar by pyrolysis (500 °C) in the presence of sodium silicate, and investigated its adsorption capacity for Cd removal. The SEM characterization shows that silicon (Si) is loaded on biochar surfaces as fine particles, and are identified as quartz (SiO 2), silicate and C–Si mixture according to X-ray diffraction. Silicate-modification significantly increases (∼45–112%) specific surface area (SSA) and slightly increases (∼5–12%) porosity of biochar. Batch results reveal that Si-modification significantly enhances Cd adsorption, and this increment is more pronounced at pH > 5. Furthermore, silicate-modification promotes the internal diffusion of Cd on biochar. FTIR and XPS analyses suggest that ion exchange with Na+, surface precipitation (CdCO 3 , CdSiO 3 or Cd 2 SiO 4), coordination with π electrons (C C) and complexation with carboxyl and C–Si–O groups are the predominant sorption mechanisms. This study puts a new perspective on the waste utilization of oiltea camellia shells for heavy metal removal from wastewaters or stabilization in contaminated soils. Image 1 • Na 2 SiO 3 modification improves porosity and functional groups on biochar surface. • Na 2 SiO 3 modification significantly enhances Cd removal than raw biochar. • Cd adsorption fits the Langmuir isotherm and pseudo-second-order kinetic model. • Ion exchange, surface precipitation and complexation dominant Cd adsorption. [ABSTRACT FROM AUTHOR]

• Biochar soil storage and biofuel utility achieve over 900 kgCO 2e ·t−1 sequestration. • Biochar implementation could reduce around 4.5% of annual national carbon emission. • Central south, east and northeast of China contribute 65% of the national GWP100. • Biochar system could mitigate aquatic ecotoxicity and soil acidification, etc. • Bio-energy offsetting coal-fired power generation dominates carbon negativity. Conversion of biomass into biofuel and biochar with a subsequent soil storage is assumed as a prospective strategy of reducing atmospheric CO 2 concentrations. However, substantial uncertainties exist in this field regarding the country-level potential of biochar carbon sequestration, indirect effects of biochar implementation on overall environment, and dominating factors. This study conducted a life cycle assessment of country-wide incorporation of biochar in agriculture, and associated potential benefits. Results showed that over 920 kg CO 2e (CO 2 -equivalent) could be sequestrated via converting 1 t of crop residues into biochar. As an example, based on crop residues availability statistics for China in 2014, the estimated annual carbon sequestration potential could be as high as 0.50 Pg CO 2e (1 Pg = 1 × 109 t). The most significant potential for biochar carbon sequestration was identified in the central south, east and northeast of China, which contributed 65% of the national biochar carbon sequestration potential. The biochar system could also contribute to mitigation of the following environmental problems: marine aquatic biodiversity destruction, surface soil and water acidification, etc. Sensitivity analysis demonstrated that biochar yield, carbon content in biochar, electricity conversion efficiencies of bio-oil and pyrolysis gas were the critical parameters determining the biochar system's overall carbon sequestration potential and environmental effects. This study provides guidance on evaluating biochar's potential carbon sequestration capacity and comprehensive environmental impacts, as well as research and development needs. [ABSTRACT FROM AUTHOR]

The knowledge about lead (Pb) sorption on soil-derived black carbons (SBCs) under different cultivation intensities of soils is limited. In this study, chemical and spectroscopic methods were applied to investigate the Pb sorption mechanisms on SBCs in soils from a forest land, a rubber plantation area, and a vegetable farm with none, less and highly intensive cultivation, respectively, that are located in the Hainan Island of China. Results showed that the specific surface area and cation exchange capacity of the SBCs from the less and highly intensive cultivation soils were 4.5- and 2.7-fold, and 1.3- and 1.8-fold higher compared to that of SBC from the no-cultivation soil, which subsequently enhanced the Pb sorption capacities of SBCs in iron exchange fraction. Ion exchange and hydrogen bonded Pb fractions together accounted for about 80% of total Pb sorbed on all SBCs at an externally added 1000 mg L−1 Pb solution concentration. The O C–O groups also played key roles in Pb sorption by forming complexes of O C–O–Pb–O and/or O C–O–Pb. Overall, SBCs in soils under all studied cultivation intensities showed high potential to sorb Pb (with the maximum absorbed Pb amount of 46.0–91.3 mg g−1), and increased Pb sorption capacities of the studied soils by 18.7–21.1 mg kg−1 in the stable fraction (complexation). Therefore, SBC might be a potential environment-friendly material to enhance the Pb immobilization capacity of soil. Image 1 • Cultivation intensities of soils significantly affect black carbon characteristics. • High cultivation intensity increased Pb in ion exchange fraction on black carbon. • Ion exchange and hydrogen bonded Pb fractions accounted for about 80% of total Pb. • Black carbon had high potential to retain Pb in stable form (by 18.7–21.1 mg kg−1). • Pb amount in ion exchange fraction was highly correlated with CEC of black carbon. [ABSTRACT FROM AUTHOR]

In China, more than 10,000 tons of bean-worm, which is rich in protein (68.5%) and essential amino acids (52.8%), is consumed annually. Thus, a large amount of bean-worm skin waste is generated, and is often indiscriminately disposed of, potentially causing environment problems. In this study, bean-worm skin (BWS) waste was pyrolyzed at 500 °C to produce biochar (BWS-BC), and the surface properties of BWS and BWS-BC were characterized using various spectroscopic techniques. Pb(II) adsorption properties of BWS and the corresponding biochar as a function of solution pH, contact time, and equilibrium concentration of Pb(II) were examined using adsorption isotherm, kinetics and thermodynamics studies. The maximum Pb(II) adsorption capacities based on the Langmuir isotherm model were calculated as 45 and 62 mg g−1 for BWS and BWS-BC, respectively, which were comparable to the values obtained for biochars derived from other agro-wastes. The adsorption feasibility, favorability and spontaneity of Pb(II), as derived from the thermodynamic parameters, indicated that chemisorption and precipitation (e.g., hydroxypyromorphite) were the main adsorption mechanism in case of BWS and BWS-BC, respectively. Thus, conversion of BWS to biochar for Pb(II) adsorption can be considered as a feasible, promising and high value-added approach for BWS recycling. Image 1 • A novel phosphorus (P) rich biochar (BWS-BC) was produced from bean-worm skin waste. • BWS-BC was effective in adsorption of Pb(II) from wastewater. • BWS-BC showed a fast initial adsorption rate in Pb(II) adsorption. • P in BWS-BC played an important role in Pb(II) adsorption. [ABSTRACT FROM AUTHOR]