Search

Abstract Biochar-derived dissolved organic matter (DOM) is important for determining the application potential of biochar in soil remediation. However, little is known about the degradation behavior of biochar-derived DOM and its interaction with heavy metals. Here, incubation experiments combined with quenching titration experiments, which analyzed by spectroscopic technology and chemometric method, were conducted to reveal such behaviors and mechanisms. Ultraviolet–visible (UV–Vis) spectra showed that high aromatic and hydrophobic fractions were enriched in biochar-derived DOM and enhanced during the cultivation process, thus the biochar-derived DOM may retain a high aromaticity, stability, and resistance. However, the environmental risk of Cu caused by the increase of DOM hydrophobicity cannot be overlooked while applying biochar to polluted soil. One fulvic-like (C1), one protein-like (C2) and two humic-like (C3, C4) substances were identified from biochar-derived DOM by using parallel factor analysis of excitation-emission matrix. Additionally, the fluorescence intensity variations of these components in DOM offered an additional interpretation for the observations from UV–Vis spectra. Two-dimensional correlation spectroscopy revealed that Cd binding to biochar-derived DOM first occurred in the protein- and fulvic-like fraction while protein- and humic-like substances had a stronger affinity for Cu. Furthermore, both phenolic and carboxyl groups firstly participated in the binding process of Cd with biochar-derived DOM, while polysaccharide gave the fastest response to Cu binding. These results clearly demonstrated the differences in specific heavy metal binding features of individual fluorescent substances and functional groups in biochar-derived DOM and contribute to improving the application effect of biochar in a multi-heavy metal polluted soil system. Graphical abstract Unlabelled Image Highlights • The biochar-derived DOM has a high aromaticity, stability, and resistance. • Environmental risk of Cu cannot be neglected while using biochar in polluted soil. • Binding behaviors of DOM with heavy metals was analyzed using 2DCOS of SF and FTIR. • The work enhances the knowledge of behavior of Cd and Cu in biochar-amended soils. [ABSTRACT FROM AUTHOR]

Poor water and nutrient retention are the major soil fertility limitations in the low productivity agricultural soils of Nepal. The addition of biochar to these soils is one way these hindrances can be overcome. In the present study, six different biochar doses (control, 5 t ha −1 , 10 t ha −1 , 15 t ha −1 , 25 t ha −1 and 40 t ha −1 ) were applied to a moderately acidic silty loam soil from Rasuwa, Nepal and the effects on soil physicochemical properties and maize and mustard yield over three years (i.e., six cropping seasons), were investigated. Biochar addition did not show significant effects on maize and mustard grain yield in the first year, however significant positive effects (p   <   0.01) were observed during the second and third years. During the second year, maize grain yield significantly increased by 50%, 47% and 93% and mustard grain yield by 96%, 128% and 134% at 15 t ha −1 , 25 t ha −1 and 40 t ha −1 of biochar respectively. A similar significant increase in yield of both crops was observed in the third year. Yields for both maize and mustard correlated significantly (p   <   0.001 ) with plant available P, K + , pH, total OC%, CEC, base saturation, and increased as a function of biochar addition. On the basis of the measured crop yields for the various biochar doses, a cost-benefit analysis was carried out, and gross margin was calculated to optimize biochar dose for local farming practice. Total costs included financial cost (farm input, labor and biochar production cost), health cost and methane emission cost during biochar production. Health costs were a minor factor (<2% of total biochar preparation cost), whereas methane emission costs were significant (up to 30% of biochar cost, depending on the C price). Total income comprised sale of crops and carbon sequestration credits. The cost-benefit analysis showed that the optimal biochar application dose was 15 t ha −1 for all C price scenarios, increasing gross margin by 21% and 53%, respectively, for 0 and 42 US$ per ton CO 2 price scenarios. In the current situation, only the 0 US$ price scenario is realistic for rural farmers in Nepal, but this still gives benefits of biochar amendment, which are capped at a 15 t ha −1 biochar addition. [ABSTRACT FROM AUTHOR]

Abstract The effects of reduced nitrogen release from sediments were studied using biochar (BC) capping in simulated water–sediment systems. Dried solid waste of Phyllostachys pubescens was used to produce BC, which was then pyrolyzed at 500 °C. Subsequently, 14 sediment cores were collected, including the sediment–water interface and some overlying water, from two sites in Baiyangdian Lake (China). The sediment cores were split into two batches (A and B), and then two each were capped with soil, BC or a BC/soil mixture, and incubated for 30 days. In the BC capped cores, the ammonia nitrogen (NH 4 +-N), nitrate nitrogen (NO 3 −-N) and total nitrogen (TN) concentrations decreased from 0.90 mg·L−1 to 0.05 mg·L−1, 0.88 mg·L−1 to 0.18 mg·L−1, 6.93 mg·L−1 to 2.81 mg·L−1, respectively, in batch A and 3.51 mg·L−1 to 0.11 mg·L−1, 0.92 mg·L−1 to 0.61 mg·L−1, 8.88 mg·L−1 to 3.32 mg·L−1, respectively, in batch B. The sediments to water fluxes of NH 4 +-N, NO 3 −-N and TN were greatly reduced or reversed. Compared with other cappings, the BC layer was shown to absorb more NH 4 +-N from the pore water, thereby breaking the diffusion gradient of NH 4 +-N at the sediment–water interface, and has a good inhibitory effect on the endogenous release of NH 4 +-N from the sediments. Additionally, in the BC capped cores, the redox potential remarkably increased and dissolved oxygen was comparatively high. This study suggests that BC capping can reduce the amount of nitrogen released from polluted sediments because the diffusion of nitrogen to the overlying water is chemically blocked by the cap. Graphical abstract Unlabelled Image Highlights • This study investigates the use of solid waste of Phyllostachys pubescens. • We first propose the idea of using biochar for sediment nitrogen remediation. • Biochar has a good effect on reducing nitrogen release, especially NH 4 +-N. • We propose a good application of biochar capping technology. [ABSTRACT FROM AUTHOR]

Abstract Landfills commonly occupy large areas of land that may be ecologically important. Ecological restoration of landfill cover is a necessary approach to rebuild sustainable habitats. However, unfavourable soil conditions and invasion by exotic plants in certain regions hinder the restoration. In this study, the effects of biochar as a soil amendment on the restoration of a landfill cover were investigated under field condition. Topsoils of a landfill cover in the subtropical region (Shenzhen, China) were mixed with 0, 5 and 10% (v/v) of biochar. Soil pH, electronic conductivity, organic matter, total organic carbon, water content, total N and total P were enhanced by biochar amendment. After nine months of self-succession, plant productivity, species richness and diversity were enhanced by biochar. The structures of soil bacterial and arbuscular mycorrhizal (AM) fungal communities were changed, and species richness and diversity were moderately promoted. Enhanced plant growth and diversity were probably attributed to a number of enhanced bacterial functions related to nutrient cycling including aerobic ammonia oxidation, aerobic nitrite oxidation, nitrification, sulphur respiration, nitrate respiration, nitrogen respiration, ureolysis, chemoheterotrophy and fermentation. The higher abundances of bacteria Streptomyces sp. and Pseudomonas sp. in biochar treatments potentially enhanced the AM fungal diversity. The bacterial diversity was more related to the soil properties, especially pH, than AM fungi. Continuous monitoring is necessary to track the changes of species composition and ecological functions over time. This is the first comprehensive study on the effects of biochar on the ecological performance of a man-made ecosystem. In addition to agricultural application, biochar can be used for restoring degraded lands. Graphical abstract Unlabelled Image Highlights • Effects of biochar on ecological restoration of disturbed lands are not clear. • Biochar was added on landfill to study the ecological performance. • Biodiversities (plant, bacteria and fungi) and ecological functions were studied. • Biochar enhanced biodiversities (especially plant) and nutrient-cycling functions. • Biochar amendment is a considerable approach for ecological restoration. [ABSTRACT FROM AUTHOR]

Evidence suggests that biochar is among ideal strategies for climate change mitigation and sustainable agriculture. However, the effects of soil aging on the physicochemical characteristics of biochar and nitrous oxide (N 2 O) production remain elusive. We set up a microcosm experiment with two greenhouse vegetable production (GVP) (alkaline and acid) soils by using the 15 N tracing technique and quantitative polymerase chain reaction (qPCR) to investigate the mechanisms of N 2 O production as affected by fresh (FB) and aged biochar (AB) amendment. The results showed that AB increased the specific surface area, organic C, ammonium sorption capacity and cation exchange capacity, whereas decreased the pore size and pH relative to the FB. Results also demonstrated that FB effectively decreased N 2 O emissions from both soils while it enhanced the abundance of nirK and nosZI genes in alkaline soil and reduced the abundance of ammonia-oxidizing bacteria (AOB) amoA and increased nirK and nosZII genes in acid soil. In contrast, AB significantly stimulated nitrification and denitrification in both soils and thus significantly increased the N 2 O emissions by 43–78%. Furthermore, AB induced increases in ammonia-oxidizing archaeal (AOA) amoA and nirK gene abundances in alkaline soil and fungal nirK gene abundances in acid soil. These results suggest that AB may not be suitable for the mitigation of soil N 2 O emissions in GVP soils thus improving our understanding of the potential mechanism of biochar in N 2 O emissions. [ABSTRACT FROM AUTHOR]

Biochar, produced through pyrolysis of organic matter, is negatively charged, thus contributing to electrostatic adsorption of cations. However, due to its porous structure and contents of alkaline ashes, the determination of the cation exchange capacity (CEC) is challenging. Literature values for the CEC of biochar are surprisingly variable and are often poorly reproducible, suggesting methodological problems. Here, we modify and critically assess different steps in the existing ammonium acetate (NH 4 OAc) method (pH 7), where ammonium (NH 4 + ) is displaced by potassium chloride (KCl), following removal of excess NH 4 OAc with isopropanol, in batch mode. We used pigeon pea biochar to develop the method and conducted a test on three additional biochars with different acid neutralizing capacity. A pretreatment step of biochar was introduced, using diluted hydrochloric acid, to decrease biochar pH to near neutral, so that 1 M NH 4 OAc effectively buffers the biochar suspension pH at 7. This allows the CEC of all biochars to be determined at pH 7, which is crucial for biochar comparison. The dissolution of ashes may cause relatively large weight losses (e.g. for cacao shell biochar), which need to be accounted for when computing the CEC of raw biochar. The sum of NH 4 OAC-extractable base cations provided a smaller and better estimate of the CEC than KCl-extractable NH 4 + . We hypothesize that the overestimation of the CEC based on KCl-extractable NH 4 + is due to the ineffectiveness of the relatively large isopropanol molecules to remove excess NH 4 OAc in biochars rich in micro-pores, due to size exclusion. The amount of base cations removed in the pretreatment was about three (rice husk biochar) to ten times (pigeon pea biochar) greater than the amount of exchangeable cations. The CEC values of biochar increased from 10.8 cmol/Kg carbon to 119.6 cmol/Kg carbon. These values are smaller than reported CEC values of soil organic carbon. [ABSTRACT FROM AUTHOR]

While metal immobilization had been increasingly reported with biochar soil amendment (BSA), changes in microbial activity and nitrogen (N) transformation in metal contaminated croplands following biochar addition had been insufficiently addressed. In a field experiment, a Pb/Cd contaminated Inceptisol from North China was amended to topsoil with wheat straw biochar at 0 (CK), 20 (C1) and 40 t ha −1 (C2). The changes within two years following BSA were tested in microbial biomass and respiration, and in abundance of N transforming microbial communities and their activities. Corresponding to the results of decreased soil extractable Cd and Pb, significant reductions in q CO 2 were found in rhizosphere and bulk soil only under C2 in the first year. The potential nitrification activity was significantly increased by 20–71%, along with an increase in ammonium (by 7–21%) and nitrate (by 21%–70%) concentration, with BSA compared to CK. Meanwhile, N 2 O production activity was slightly increased (by up to 20%) but N 2 O reduction activity greatly enhanced (by up to 84%), with a higher ratio of nosZ /( nirS  +  nirK) , under C2 in rhizosphere in both wheat seasons. Whereas, such changes were not remarkable in bulk soil. Moreover, microbial communities were less respondent to biochar in the second year following the addition. Therefore, microbial growth and functioning for N transforming and cycling in metal contaminated soils could be largely improved with BSA at 40 t ha −1 . Of course, studies are still deserved to mimic the long term changes with biochar in N cycling of the metal contaminated dry croplands. [ABSTRACT FROM AUTHOR]

Biochar has shown great potential as an amendment to improve soil quality and promote plant growth, as well as to adsorb pollutants from water. However, information about the effect of biochar on the wastewater treatment efficiency in horizontal subsurface flow (HSSF) constructed wetlands (CWs) is still scarce. In this study, we assessed the effect of biochar amendment on the purification efficiency of pretreated municipal wastewater in planted ( Typha latifolia ) experimental horizontal subsurface flow filters filled with lightweight expanded clay aggregates (LECA). The addition of wood-derived biochar (10% v/v) to LECA significantly increased plant biomass production and enhanced the wastewater treatment efficiency of the planted filters. Both the aboveground plant biomass and belowground plant biomass were higher (1.9- and 1.5-fold, respectively) in the filters of the LBP (LECA + biochar + plants) treatments compared to the LP (LECA + plants) filters. The water pH was significantly lower in the planted filters (LBP < LP < LB-LECA + biochar). The efficiencies of TN and TP removal from wastewater were highest in the LBP filters (20.0% and 22.5%, respectively), followed by the LP (13.7% and 16.2%, respectively) and LB (9.5% and 15.6%, respectively) filters. More N and P were incorporated into the plant biomass from wastewater in the presence of biochar in the filter medium. The study results confirm that biochar can be an advantageous supplement for planted HSSF CWs to enhance the treatment efficiency of these systems. [ABSTRACT FROM AUTHOR]

Biochar nitrogen is key to improving soil fertility, but the distribution of biochar nitrogen in the biomass–biochar–plant system is still unclear. To provide clarity, the 15 N tracer method was utilised to study the distribution of biochar nitrogen in the biochar both before and after its addition to the soil. The results can be summarised as follows. 1) The retention rate of 15 N in biochar decreases from 45.23% to 20.09% with increasing pyrolysis temperature from 400 to 800 °C in a CO 2 atmosphere. 2) The retention rate of 15 N in biochar prepared in a CO 2 atmosphere is higher than that prepared in a N 2 atmosphere when the pyrolysis temperature is below 600 °C. 3) Not only can biochar N slowly facilitate the adsorption of N by plants but the addition of biochar to the soil can also promote the supply of soil nitrogen to the plant; in contrast, the direct return of wheat straw biomass to the soil inhibits the absorption of soil N by plants. 4) In addition, the distribution of nitrogen was clarified; that is, when biochar was prepared by the pyrolysis of wheat straw at 400 °C in a CO 2 atmosphere, the biochar retained 45.23% N, and after the addition of this biochar to the soil, 39.99% of N was conserved in the biochar residue, 4.55% was released into the soil, and 0.69% was contained in the wheat after growth for 31 days. Therefore, this study very clearly shows the distribution of nitrogen in the biomass–biochar-plant system. [ABSTRACT FROM AUTHOR]

Adding biochar to Zn-contaminated soil can immobilize excess Zn and promote plant biomass growth. This was seen previously over the course of a 180-day planted pot trial involving two types of biochar (cattle manure, CM, and grain husk, GH) in a Zn-contaminated soil. Both biochars alleviated Zn-induced phytotoxicity to Ficus by immobilizing Zn and reducing its uptake by the plant, but to different extents. The aim of the current study was to delve into the in-soil mechanisms involved in biochar-mediated Zn immobilization. Biochar particles were excavated from the pot soils. Fresh and aged biochar particles were examined by high-resolution scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), field-emission electron probe micro-analyzer (EPMA), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The physical and chemical properties of the biochars had changed over the 180 days. SEM-EDS and EPMA indicated that organo-mineral micro-agglomerates had formed on biochar surfaces and in pores. Some of the Zn immobilized by the biochars was bound in the organo-mineral complexes of these agglomerates. XPS and FTIR showed that the complexes had a high concentration of oxygenated functional groups which facilitated Zn binding and encapsulation. The micro-agglomerates were similar in structure and composition to those observed on biochars having resided for much longer times in soils, or having been subjected to accelerated aging. Overall, Zn immobilization by the CM biochar was greater than by the GH biochar, due to its higher alkalinity, higher concentration of available negatively charged groups, and greater accretion of organo-mineral layers. These findings are suggestive that biochar-assisted phytorestoration of heavy metal-contaminated soils can be optimized through selection of biochar having such traits. It is hypothesized that metals may be continually taken up in such micro-agglomerates, since they continue to form over the lifetime of the biochar in the soil. [ABSTRACT FROM AUTHOR]

The effects of aging on biochar (BC) properties, composition and carbon sequestration are still under debate. This study aimed at illustrating the qualitative alterations of five different BCs aged during a 24-month field experiment located in Southwest Spain. To determine the recalcitrance of each BC, physical fragmentation test, scanning electron microscopy, 13 C NMR spectroscopy and CO 2 -respiration experiments were performed. The physical fragmentation values of all types of BC increased significantly over time at field conditions. FESEM examinations of aged BCs showed collapsed structures and the presence of entrapped soil material and microbial mats into the BC pores. The 13 C NMR spectroscopy demonstrated an increase of the relative abundance of O -alkyl C and alkyl C at expenses of aromatic-C in aged BCs. The C losses of all BCs ranged from 27% to 11% of the initial C. In contrast, the nitrogen (N) content of wood-derived BCs significantly increased probably due to the sorption of nitrogen containing compounds into these highly-porous weathered chars. With the exception of that for the sewage sludge-BC, the pH of all aged BCs decreased from > 9 to the soil pH, indicating a short lasting of the liming effect caused by BC addition. The respiration experiment revealed that BC recalcitrance was much lower than expected and, within the range of decades. Only wood-derived BCs significantly increased the mean residence time of the slow C pool of the Cambisol by factors between 3.4 and 7.7. Mediterranean climate conditions and the characteristics of the Cambisol used probably accelerated the microbial degradation of BCs. [ABSTRACT FROM AUTHOR]

In recent years, biochar has been extensively studied as a sorbent for immobilizing contaminants and minimizing their bioavailability in soils. Few studies have been conducted to evaluate the interactions between biochar and compost in soils and their impact on degradation of organic contaminants. In the present study, soils with high organic carbon content (HOC) and low organic carbon content (LOC) were spiked with 100 mg·kg − 1 di-(2-ethylhexyl) phthalate (DEHP) amended with biochar derived from dead pigs, bamboo, and composted sheep manure. The soils were thereafter incubated for 112 days at 25 °C and periodically sampled for monitoring DEHP concentrations. Degradation of DEHP was described by a logistic model. Results showed that the initial degradation rates were slow, but accelerated after 14 days of incubation. The DEHP degradation rates were higher in the HOC soils than in the LOC soils over the incubation period. The half-lives of DEHP were shorter in the LOC soils treated with pig biochar, and bamboo/pig biochar plus compost than in the untreated soil. However, there was no significant difference in the half-lives of DEHP in the HOC control and treated soils. The differential effects of soil amendments on DEHP degradation between LOC and HOC soils could be explained by the properties of the organic amendments, soil pH and the organic carbon contents of the soils. [ABSTRACT FROM AUTHOR]

We studied the role of biochar in improving soil fertility for maize production. The effects of biochar on the alleviation of three potential physical-chemical soil limitations for maize growth were investigated, i.e. water stress, nutrient stress and acid stress. Experiments involved soils with two dosages of biochar (0.5% and 2% w:w), as well as ones without biochar, in combination with four different dosages of NPK fertilizer, water and lime. Biochar was produced from the invasive shrubby weed Eupatorium adenophorum using flame curtain kilns. This is the first study to alleviate one by one the water stress, nutrient stress and acid stress in order to investigate the mechanisms of biochar effects on soil fertility. Biochar addition increased soil moisture, potassium (K) and plant available phosphorous (P-AL), which all showed significant positive relationship ( p < 0.001) with above ground biomass of maize. However, biochar was much more effective at abundant soil watering (+ 311% biomass) than at water-starved conditions (+ 67% biomass), indicating that biochar did increase soil moisture, but that this was not the main reason for the positive biomass growth effects. Biochar addition did have a stronger effect under nutrient-stressed conditions (+ 363%) than under abundant nutrient application (+ 132%). Biochar amendment increased soil pH, but liming and pH had no effect on maize dry biomass, so acidity stress alleviation was not the mechanism of biochar effects on soil fertility. In conclusion, the alleviation of nutrient stress was the probably the main factor contributing to the increased maize biomass production upon biochar addition to this moderately acidic Inceptisol. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the importance of the nutrient status of biochar and soils prior to its inclusion in particular agricultural systems. Pre-treatment of nutrient-reactive biochar, where nutrients are loaded into pores and onto surfaces, gives improved yield outcomes compared to untreated biochar. In this study we have used a wide selection of spectroscopic and microscopic techniques to investigate the mechanisms of nutrient retention in a high temperature wood biochar, which had negative effects on Chenopodium quinoa above ground biomass yield when applied to the system without prior nutrient loading, but positive effects when applied after composting. We have compared non-composted biochar (BC) with composted biochar (BCC) to elucidate the differences which may have led to these results. The results of our investigation provide evidence for a complex series of reactions during composting, where dissolved nutrients are first taken up into biochar pores along a concentration gradient and through capillary action, followed by surface sorption and retention processes which block biochar pores and result in deposition of a nutrient-rich organomineral (plaque) layer. The lack of such pretreatment in the BC samples would render it reactive towards nutrients in a soil-fertilizer system, making it a competitor for, rather than provider of, nutrients for plant growth. [ABSTRACT FROM AUTHOR]

Little is known regarding how biochars' feedstock and pyrolysis temperature affect soil function and plant growth. To address this gap in knowledge, 12 biochars (walnut shells, corn cobs, corn straws, and rice straws were separately pyrolyzed at 250, 400, and 600 °C for 4 h) were applied to soil from an indigenous coking site with application rate of 2.5% (w/w) in a pot experiment to determine the impact of biochar types on macro-nutrients (total and available N, P, and K) and ryegrass growth in the soil from an indigenous coking site. Generally, the total N, P, and K in the soil was not significantly different from that of the control group. However, biochars decreased the available N from 21.76 mg·kg − 1 for the control to 14.96 mg·kg − 1 . Corn straw and rice straw biochars increased the available P from 2.14 mg·kg − 1 for the control to 28.35 mg·kg − 1 , specifically at higher pyrolysis temperature, while walnut shell and corn cob biochars had little influence on it regardless of pyrolysis temperature. Biochars increased the available K from 173.58 mg·kg − 1 for the control to 355.64 mg·kg − 1 , varying as their feedstocks of corn cob > rice straw > corn straw > walnut shell and increasing with the increase of pyrolysis temperature. Correlation analysis suggests that it is responsible for the competition of soluble cations from biochars with K for adsorption sites on the soil surface. Biochars increased the ryegrass biomass from 0.07 g·pot − 1 for the control to 0.16 g·pot − 1 , with the generally most effective stimulation by biochars produced at 400 °C. Ryegrass biomass had obviously positive correlation with available K, indicating its essential role in the growth of ryegrass in the studied soil. [ABSTRACT FROM AUTHOR]

Biochar has been recognized as an efficient soil amendment for cadmium remediation in recent years. In the present study, biochar was prepared using walnut shell, and it was incubated in Cd(NO 3 ) 2 and kaolin for 15 days. Different chemical forms of cadmium in kaolin and biochar were determined, and the stability of biochar was evaluated by R 50 using TGA analysis. It was found that walnut shell derived biochar could reduce the mobility of cadmium. After incubation, the R 50, biochar value increased from 61.31% to 69.57%–72.24%, indicating that the stability of biochar was improved. The mechanisms that initiated improvements in biochar stability were investigated by XPS, XRD and SEM-EDS analysis. The result showed that the enhanced biochar stability is likely due to physical isolation and the formation of precipitates and complexes, formed on the surface or interior of the biochar. The results suggested that walnut shell-derived biochar can be used as a cadmium sorbent for soil remediation. [ABSTRACT FROM AUTHOR]

The use of biochar for the removal of heavy metals from water has environmental benefits. In order to elucidate the potential application of highly functionalized biochar for the removal of Pb(II) in aqueous solution, maple wood biochar was oxidized using hydrogen peroxide. The pH values of oxidized biochar ranged from 8.1 to 3.7, with one set being adjusted to a pH of 7 as a comparison. It was found that oxidizing the biochars increased their Pb(II) adsorption capacity if the pH remained below 6 (strong oxidation), but decreased their Pb(II) adsorption ability above pH 6 (weak oxidation). After adjusting the pH of oxidized biochar to pH 7, the Pb(II) adsorption capacity further increased two to sixfold for oxidized biochars originally at pH 3.7–6. The adsorption characteristics of Pb(II) were well described by the Langmuir equation. Adsorption of Pb(II) was not fully reversible in water. Less than 6% of Pb(II) desorbed in water in two consecutive steps than was previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 0.1 M NaNO 3 increased from 0.7% to 32.7% of Pb(II) undesorbed by both preceding water extractions with increasing oxidation, for biochars with a pH below 7. Unextractable Pb(II) was lower at low oxidation but increased to 99.0% of initially adsorbed amounts at low pH, which indicated that the adsorption of Pb(II) on oxidized biochar is pH independent. [ABSTRACT FROM AUTHOR]

Low fertility limits crop production on acidic soils dominating much of the humid tropics. Biochar may be used as a soil enhancer, but little consensus exists on its effect on crop yield. Here we use a controlled, replicated and long-term field study in Sumatra, Indonesia, to investigate the longevity and mechanism of the effects of two contrasting biochars (produced from rice husk and cacao shell, and applied at dosages of 5 and 15 t ha −1 ) on maize production in a highly acidic Ultisol (pH KCl 3.6). Compared to rice husk biochar, cacao shell biochar exhibited a higher pH (9.8 vs. 8.4), CEC (197 vs. 20 cmol c kg −1 ) and acid neutralizing capacity (217 vs. 45 cmol c kg −1 ) and thus had a greater liming potential. Crop yield effects of cacao shell biochar (15 t ha −1 ) were also much stronger than those of rice husk biochar, and could be related to more favorable Ca/Al ratios in response to cacao shell biochar (1.0 to 1.5) compared to rice husk biochar (0.3 to 0.6) and nonamended plots (0.15 to 0.6). The maize yield obtained with the cacao shell biochar peaked in season 2, continued to have a good effect in seasons 3–4, and faded in season 5. The yield effect of the rice husk biochar was less pronounced and already faded from season 2 onwards. Crop yields were correlated with the pH-related parameters Ca/Al ratio, base saturation and exchangeable K. The positive effects of cocoa shell biochar on crop yield in this Ultisol were at least in part related to alleviation of soil acidity. The fading effectiveness after multiple growth seasons, possibly due to leaching of the biochar-associated alkalinity, indicates that 15 t ha −1 of cocoa shell biochar needs to be applied approximately every third season in order to maintain positive effects on yield. [ABSTRACT FROM AUTHOR]

Upon addition to or otherwise entering soils and waters, biochar particles inevitably interact with natural mineral nanoparticles (NPs). We explored the impacts of two biochars made from charring peanut shells at 300 and 600 °C (P300 and P600) on the characteristics of soil NPs extracted from brown soil and laterite soil. The dispersion or sedimentation of montmorillonite (Mon), kaolinite (Kao), goethite (Goe), and hematite (Hem) in the aquatic phase were investigated in the presence of P300 and P600 or their nano samples (NP300 and NP600). P300 and P600 increased the organic C fraction in the soil NPs extracted from brown soil, and decreased the amount of Fe-associated NPs. However, no significant influence was observed in the organic C and mineral phases of laterite soil NPs by P300 and P600. Goe and Hem were slightly adsorbed to P300 at pH 6.5, while Goe or Hem homoaggregates formed and settled onto P600. NP300 and NP600 significantly reduced the dispersion of Goe and Hem in the aquatic environment via heteroaggregation, but there was no interaction between NP300 or NP600 and Mon or Kao. These findings are helpful for understanding the interaction between natural minerals and biochars, and the potential fate and ecological services of biochar-mineral complexes in soil and water. [ABSTRACT FROM AUTHOR]

Biochars with different Al contents (i.e., 5, 10, 15, and 20 wt%) were prepared to evaluate their adsorption capacities for nitrate (NO 3 − ) and phosphate (PO 4 3− ) from eutrophic water. Several techniques, including N 2 adsorption–desorption, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectrometry, were applied to characterize the physical–chemical properties of the biochars. We found that the NO 3 − and PO 4 3− adsorptions significantly improved on the Al-modified biochars because of their multifunctional and surface charge properties. In single-solute adsorption, 15 Al/BC and 20 Al/BC exhibited optimal NO 3 − and PO 4 3− adsorption capacities, respectively. In bi-solute coadsorption, the PO 4 3− adsorption on the biochar was less affected with the coexistence of NO 3 − , whereas the coexistence of PO 4 3− had a significant impact on the NO 3 − adsorption. The optimal solution pH for NO 3 − adsorption was 6, and pH < 6 was advantageous to PO 4 3− adsorption. In the kinetic study, the pseudo-second-order model could describe the NO 3 − and PO 4 3− adsorptions on biochar well, indicating that chemical adsorption was the main adsorption mechanism. The Langmuir–Freundlich model agreed well with the NO 3 − and PO 4 3− adsorptions on the biochars, and the maximum adsorption capacities for NO 3 − and PO 4 3− reached 89.58 mg/g and 57.49 mg/g, respectively. Therefore, the Al-modified biochar was a good choice for the remediation of eutrophic water. [ABSTRACT FROM AUTHOR]

In order to enhance the adsorption capacity of cadmium (Cd) ion from aqueous solution, the rice straw-derived biochar (BC800) was modified by a mixture of HNO 3 and H 2 O 2 (MHH) with equal volume. Several elemental, chemical and structural characterization methods were used to determine the characteristics of biochars. Batch adsorption experiments were carried out concerning the influences of contact time, initial pH value, and initial concentration. The results indicated that the modified biochar (BCM) was more effective in removing Cd 2+ from water than BC800. For 550 mg L −1 Cd 2+ concentration solution, the adsorption capacity of 93.2 mg g −1 was observed for BCM, which was much higher than that of BC800 (69.3 mg g −1 ). The BCM had a significant increase of acidic functional groups with a rate of 101.6% and the component carboxyl, lacton and phenol groups increased by 124.1%, 29.3% and 111.3% respectively, while the specific surface area increased about 22.0%, compared with BC800. The pseudo-second-order model provided high correlation coefficients for BCM, speculating chemisorption of the Cd 2+ onto biochars. Therefore, the rice straw-based biochar treated by MHH is considered to be an efficient adsorbent for Cd 2+ removal from aqueous solution, especially for high concentrations of cadmium solution. [ABSTRACT FROM AUTHOR]

Biochar was applied during the bioleaching of heavy metals (HMs) from swine manure (SM), in an attempt to accelerate the HMs removal rates and to reduce the losses of nutrient elements (nitrogen and phosphorus). Results showed that the addition of biochar (5 g L −1 ) could not only significantly shorten the leaching time of HMs (Cu, Zn, Mn and Cd) from 10 (control) to 7 days with a high solubilization efficiency of 90%, but also decrease the total nitrogen loss efficiency by 42.7% from 180.3 (control) to 103.3 mg L −1 in the leachate. In addition, biochar addition facilitated Fe 2+ oxidation rate, achieving much better pH and ORP conditions. Electronic conductivity and adsorption properties of biochar with changed microbial community probably contributed a lot to the enhanced HMs solubilization and reduced nitrogen loss during bioleaching. Although the addition of biochar only slightly reduced the total amount of phosphorus loss, the bioavailable phosphorus in SM after bioleaching was markedly increased by 13.7%. [ABSTRACT FROM AUTHOR]

An equilibrium passive sampler based on polyoxymethylene (POM) was used to determine the freely dissolved concentrations (C free ) of fipronil and ethiprole. The sorption equilibrium times of fipronil and ethiprole in POM were 14.2 d and 24.0 d, respectively. The POM-water partitioning coefficients (logK POM-water ) were 2.6 for fipronil and 1.4 for ethiprole. The method was further used to evaluate the sorption behavior of biochars which produced by pyrolysis of Magnolia wood ( Magnolia denudata ) at 300 °C, 500 °C and 700 °C. The amounts of target compounds adsorbed increased with increasing pyrolysis temperature of the biochars. Biochars characterized by a low polarity index had better sorption capacity for the target compounds. The additions of biochars to sediment were effective in reducing C free , and the enhancement was found to be more pronounced with high biochar content. C free in sediment with more organic matter was significantly higher after biochar addition. Increasing the sediment-biochar contact time from 7 to 30 d resulted in an increase in sorption of the compounds. We conclude that Magnolia wood biochar effectively reduces the content of freely dissolved fipronil and ethiprole content in sediment. [ABSTRACT FROM AUTHOR]

A batch experiment was conducted to examine the effects of biochar on the behaviour of soil-borne arsenic and metals that were mobilized by three low-molecular-weight organic acids. In the presence of citric acid, oxalic acid and malic acid at a molar concentration of 0.01 M, the surface of biochar was protonated, which disfavours adsorption of the cationic metals released from the soil by organic acid-driven mobilization. In contrast, the oxyanionic As species were re-immobilized by the protonated biochar effectively. Biochar could also immobilize oxyanionic Cr species but not cationic Cr species. The addition of biochar increased the level of metals in the solution due to the release of the biochar-borne metals under attack by LMWOAs via cation exchange. Biochar could also have the potential to enhance reductive dissolution of iron and manganese oxides in the soil, leading to enhanced release of trace elements bound to these oxides. The findings obtained from this study have implications for evaluating the role of biochar in immobilizing trace elements in rhizosphere. Adsorption of cationic heavy metals on biochar in the presence of LMWOAs is unlikely to be a mechanism responsible for the impeded uptake of heavy metals by plants growing in heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

The physicochemical properties and adsorption capacities of yak manure biochar (SP350-YMB) and modified yak manure biochar by H 2 O 2 (AC-YMB) were investigated. Results showed the oxygen content and the carboxyl group content of manure biochar increased by 63.4% and 101%, and the ash content decreased 42% after modification, respectively. Compared to SP350-YMB, the adsorption capacities of heavy metal ions (Pb 2+ , Cu 2+ , Cd 2+ and Zn 2+ ) were enhanced by AC-YMB in single-metal and multi-metal solutions. The maximum adsorption capacity of Pb 2+ increased from 76.41 mg g −1 by SP350-YMB to 169.57 mg g −1 by AC-YMB based on Langmuir-Freundlich model in single-metal solutions. Pseudo-first and Pseudo-second-order model were used to predict the Pb 2+ adsorption kinetics by AC-YMB. H 2 O 2 modification reduced ash content and increased carboxyl content resulting in the major mechanism of heavy metal sorption shifting from precipitation with carbonate/phosphate to complexation with carboxyl. Results from this study indicated that H 2 O 2 modified biochar could act as effective surface sorbent to remove heavy metals, but its ability to remove multi-metal ions needs to be carefully evaluated on an individual basis. [ABSTRACT FROM AUTHOR]

Although a meta-analysis on biochar's effects on N 2 O emission reported an overall reduction in N 2 O emission by adding biochar to the soils, there are still variations in the changes in N 2 O emission, especially from field results. The objectives of this study are 1) to compare the effects of biochar addition on N 2 O emission between three agricultural upland field experiments, where soil water status was dry favoring nitrification and 2) to identify main factors explaining biochar's variable effects on N 2 O emission. Three field experiments were conducted: Exp A in the cultivated grassland treated with rice husk biochar at 2 ton ha −1  + urea (CHAR) and with urea only (CON); Exp B in the cabbage field with CHAR and CON treatments; and Exp C in the pepper field with CHAR, CON, and CHAR + DCD (dicyandiamide, nitrification inhibitor) treatments. In Exp A and C, cumulative N 2 O emissions significantly increased by 82.5% and 55.8% in the CHAR than CON treatments, respectively, while in Exp B, there was no difference in cumulative N 2 O emission between the CHAR and CON. Based on results from using nitrification inhibitor and soil % water filled pore space (WFPS), we assumed that the main N 2 O production mechanism was nitrification. Our results suggest that soil water status right after urea application is the primary determinant of different effects of biochar on N 2 O emission in addition to soil C status and biochar's adsorption. Principal component analysis using the 25 compiled data also supported our results. This study identified the specific field conditions under which biochar could have stimulating effects on N 2 O emission. Mitigation potential of biochar application should be reconsidered if biochar and urea were amended to dry soils with low C contents. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine changes in the physicochemical properties and toxicity of soil amended with sewage sludge (10 t dw /ha) or sewage sludge (10 t dw /ha) with biochar addition (2.5, 5 or 10% of sewage sludge). The study was carried out as a field experiment over a period of 18 months. Samples for analysis were taken at the beginning of the experiment as well as after 6, 12 and 18 months. The study investigated toxicity of the unamended soil, sewage sludge-amended soil and sewage sludge-amended soil with biochar addition towards Folsomia candida (collembolan test) and Lepidium sativum (Phytotoxkit F). Moreover, toxicity of aqueous extracts obtained from the tested soils towards Vibrio fischeri (Microtox®) and Lepidium sativum (elongation test) was determined. The study showed that addition of biochar to the sewage sludge and soil reduced leaching of nutrients (mainly phosphorus and potassium) from the amended soil. Biochar significantly reduced sewage sludge toxicity, exhibiting a stimulating effect on the tested organisms. The stimulating effect of biochar addition to the sewage sludge persisted throughout the entire experiment. Apart from the remediatory character of biochar, this is also evidence of its fertilizing character. In the tests with L . sativum (leachates and solid phase) and V . fischeri (leachates), increasing the rate of biochar in the sewage sludge increased root growth stimulation ( L . sativum ) and bacteria luminescence ( V . fischeri ). However, increasing biochar rate decreased F . candida reproduction stimulation, which could have been an effect of reduced nutrient bioavailability due to the biochar. [ABSTRACT FROM AUTHOR]

A novel sorbent made from biochar modified with an amorphous Mn oxide (AMOchar) was compared with pure biochar, pure AMO, AMO + biochar mixtures and biochar + birnessite composite for the removal of various metal(loid)s from aqueous solutions using adsorption and solid-state analyses. In comparison with the pristine biochar, both Mn oxide-biochar composites were able to remove significantly greater quantities of various metal(loid)s from the aqueous solutions, especially at a ratio 2:1 (AMO:biochar). The AMOchar proved most efficient, removing almost 99, 91 and 51% of Pb, As and Cd, respectively. Additionally, AMOchar and AMO + biochar mixture exhibited reduced Mn leaching, compared to pure AMO. Therefore, it is concluded that the synthesis of AMO and biochar is able to produce a double acting sorbent (‘dorbent’) of enhanced efficiency, compared with the individual deployment of their component materials. [ABSTRACT FROM AUTHOR]

Soil salinization and sodification are two commonly occurring major threats to soil productivity in arable croplands. Salt-affected soils are found in > 100 countries, and their distribution is extensive and widespread in arid and semi-arid regions of the world. In order to meet the challenges of global food security, it is imperative to bring barren salt-affected soils under cultivation. Various inorganic and organic amendments are used to reclaim the salt-affected lands. The selection of a sustainable ameliorant is largely determined by the site-specific geographical and soil physicochemical parameters. Recently, biochar (solid carbonaceous residue, produced under oxygen-free or oxygen-limited conditions at temperatures ranging from 300 to 1000 °C) has attracted considerable attention as a soil amendment. An emerging pool of knowledge shows that biochar addition is effective in improving physical, chemical and biological properties of salt-affected soils. However, some studies have also found an increase in soil salinity and sodicity with biochar application at high rates. Further, the high cost associated with production of biochar and high application rates remains a significant challenge to its widespread use in areas affected by salinity and sodicity. Moreover, there is relatively limited information on the long-term behavior of salt-affected soils subjected to biochar applications. The main objective of the present paper was to review, analyze and discuss the recent studies investigating a role of biochar in improving soil properties and plant growth in salt-affected soils. This review emphasizes that using biochar as an organic amendment for sustainable and profitable use of salt-affected soils would not be practicable as long as low-cost methods for the production of biochar are not devised. [ABSTRACT FROM AUTHOR]

As a new soil amendment, biochar has become an environmentally friendly material. The application of biochar is one of the most promising management practice to improve soil quality. Using a reclaimed soil from a coal mine subsidence area, the plat soil cultivation experiment in this study investigated the effects of biochar application at varying rates on soil properties, the abundance and composition of soil denitrifier communities. Biochar application significantly increased the crop yield which might be associated with the increased level of cation exchange capacity (CEC), total nitrogen (N), ammonium-N, available phosphorus (P) and potassium (K) in soil. In combination with N fertilizer, the abundance of both nirK and nirS genes significantly increased only at biochar application rate of 4% compared with the nil-biochar treatment. Biochar application significantly increased the community diversity of nirK gene, while not for nirS gene. Redundancy analysis showed that the level of nitrate-N (NO 3 − -N), available P, and pH in soil significantly affected community structure of nirK gene, while the nirS community composition was only affected by soil NO 3 − -N level. Our results indicate that biochar application to the reclaimed soil in coal mine subsidence area could influence the abundance and diversity of soil denitrifiers and improve soil nutrients thus crop yield. [ABSTRACT FROM AUTHOR]

This work addresses the effect of biochar amendment to soil on contaminant sorption, bioavailability, and ecotoxicity. A distinction between positive primary amendment effects caused by reduced toxicity resulting from contaminant sorption, and negative secondary amendment effects of the biochars themselves was seen. Two biochars (one from high technology and one from low technology production processes) representing real world biochars were tested for the adsorption of pyrene, polychlorinated biphenyl (PCB) 52), and dichlorodiphenyldichloroethylene ( p , p′- DDE). Sorption by both biochars was similar, both for compounds in single and mixed isotherms, in the presence and absence of soil. p , p′- DDE natively contaminated and spiked soils were amended with biochar (0, 1, 5, and 10%) and bioavailability, operationally defined bioaccessibility and ecotoxicity were assessed using polyethylene (PE), polymeric resin (XAD) and Folsomia candida , respectively. At the highest biochar dose (10%), bioavailability and bioaccessibility decreased by > 37% and > 41%, respectively, compared to unamended soils. Mortality of F. candida was not observed at any biochar dose, while reproductive effects were dose dependent. F. candida benefited from the reduction of p , p′- DDE bioavailability upon 1% and 5% biochar addition to contaminated soils while at 10% dose, these positive effects were nullified by biochar-induced toxicity. p , p′- DDE toxicity corrected for such secondary effects was predicted well by both PE uptake and XAD extraction. [ABSTRACT FROM AUTHOR]

Biochar application to soil has been proposed for soil carbon sequestration and global warming mitigation. While recent studies have demonstrated that soil pH was a main factor affecting soil microbial community and stability of biochar, little information is available for the microbiome across different soil pH and the subsequently CO 2 emission. To investigate soil microbial response and CO 2 emission of biochar across different pH levels, comparative incubation studies on CO 2 emission, degradation of biochar, and microbial communities in a ferralsol (pH 5.19) and a phaeozems (pH 7.81) with 4 biochar addition rates (0.5%, 1.0%, 2.0%, 5.0%) were conducted. Biochar induced higher CO 2 emission in acidic ferralsol, largely due to the higher biochar degradation, while the more drastic negative priming effect (PE) of SOC resulted in decreased total CO 2 emission in alkaline phaeozems. The higher bacteria diversity, especially the enrichment of copiotrophic bacteria such as Bacteroidetes , Gemmatimonadetes , and decrease of oligotrophic bacteria such as Acidobacteria , were responsible for the increased CO 2 emission and initial positive PE of SOC in ferralsol, whereas biochar did not change the relative abundances of most bacteria at phylum level in phaeozems. The relative abundances of other bacterial taxa (i.e. Actinobacteria , Anaerolineae ) known to degrade aromatic compounds were also elevated in both soils. Soil pH was considered to be the dominant factor to affect CO 2 emission by increasing the bioavailability of organic carbon and abundance of copiotrophic bacteria after biochar addition in ferralsol. However, the decreased bioavailability of SOC via adsorption of biochar resulted in higher abundance of oligotrophic bacteria in phaeozems, leading to the decrease in CO 2 emission. [ABSTRACT FROM AUTHOR]

Particle size of biochar may strongly affect the kinetics of hydrophobic organic compound (HOC) sorption. However, challenges exist in characterizing the effect of biochar particle size on the sorption kinetics because of the wide size range of biochar. The present study suggests a novel method to determine a representative value that can be used to show the dependence of HOC sorption kinetics to biochar particle size on the basis of an intra-particle diffusion model. Biochars derived from three different feedstocks are ground and sieved to obtain three daughter products each having different size distributions. Phenanthrene sorption kinetics to the biochars are well described by the intra-particle diffusion model with significantly greater sorption rates observed for finer grained biochars. The time to reach 95% of equilibrium for phenanthrene sorption to biochar is reduced from 4.6–17.9 days for the original biochars to < 1–4.6 days for the powdered biochars with < 125 μm in size. A moderate linear correlation is found between the inverse square of the representative biochar particle radius obtained using particle size distribution analysis and the apparent phenanthrene sorption rates determined by the sorption kinetics experiments and normalized to account for the variation of the sorption rate-determining factors other than the biochar particle radius. The results suggest that the representative biochar particle radius reasonably describes the dependence of HOC sorption rates on biochar particle size. [ABSTRACT FROM AUTHOR]

Landfilling of food waste due to its low recycling rate is raising serious concerns because of associated soil and water contamination, and emission of methane and other greenhouse gases during the degradation process. This paper explores feasibility of using biochar derived from mixed food waste (FWBC), rice waste (RWBC) and wood waste (mixed wood saw dust, MWBC) as carbon sequestering additive in mortar. RWBC is prepared from boiled plain rice, while FWBC is prepared from combination of rice, meat, and vegetables in fixed proportion. Carbon content in FWBC, RWBC and MWBC were found to be 71%, 66% and 87% by weight respectively. Results show that addition of 1–2 wt% of FWBC and RWBC in mortar results in similar mechanical strength as control mix (without biochar). 1 wt% of FWBC led to 40% and 35% reduction in water penetration and sorptivity respectively, indicating higher impermeability of mortar. Biochar from mixed wood saw dust performed better in terms of mechanical and permeability properties. Increase in compressive strength and tensile strength by up to 20% was recorded, while depth of water penetration and sorptivity was reduced by about 60% and 38% respectively compared to control. Both FWBC and MWBC were found to act as reinforcement to mortar paste, which resulted in higher ductility than control at failure under flexure. This study suggests that biochar from food waste and mixed wood saw dust has the potential to be successfully deployed as additive in cement mortar, which would also promote waste recycling, and sequester high volume carbon in civil infrastructure. [ABSTRACT FROM AUTHOR]

Biochar (BC) is gaining attention as a soil amendment that can remediate metal polluted soils. The simultaneous effects of BC on copper (Cu) mobility, microbial activities in soil using metallophytes have scarcely been addressed. The objective of this study was to evaluate the effects of biochar BCs on Cu immobilization and over soil microbial communities in a Cu-contaminated soil evaluated over a two-year trial. A Cu-contaminated soil (338 mg kg − 1 ) was incubated with chicken manure biochar (CMB) or oat hull biochar (OHB) at rates of 1 and 5% w/w. Metallophyte Oenothera picensis was grown over one season (six months). The above process was repeated for 3 more consecutive seasons using the same soils. The BCs increased the soil pH and decreased the Cu exchangeable fraction Cu by 5 and 10 times (for OHB and CMB, respectively) by increasing the Cu bound in organic matter and residual fractions, and its effects were consistent across all seasons evaluated. BCs provided favorable habitat for microorganisms that was evident in increased microbial activity. The DHA activity was increased in all BC treatments, reaching a maximum of 7 and 6 times higher than control soils in CMB and OHB. Similar results were observed in microbial respiration, which increased 53% in OHB and 61% in CMB with respect to control. The BCs produced changes in microbial communities in all seasons evaluated. The fungal and bacterial richness were increased by CMB and OHB treatments; however, no clear effects were observed in the microbial diversity estimators. The physiochemical and microbiological effects produced by BC result in an increase of plant biomass production, which was on average 3 times higher than control treatments. However, despite being a metallophyte, O. picensis did not uptake Cu efficiently. Root and shoot Cu concentrations decreased or changed insignificantly in most BC treatments. [ABSTRACT FROM AUTHOR]

During the past decade, biochar has attracted immense scientific interest for agricultural and environmental applications. A broad range of biochars with advantageous properties (e.g., high surface area, flexible architecture, and high porosity) has been developed for pollution abatement. Nevertheless, biochar suffers from certain drawbacks (e.g., limited sorption capacity for anions and poor mechanical properties) that limit their practical applicability. This review focuses on recent advancements in biochar technology, especially with respect to its technical aspects, the variables associated with removing phosphates from water, and the challenges for such abatement. The attention paid to the specific remediation of phosphate from water using biochar is limited (n = 1114 – Scopus) compared to the application of biochar to other common water pollutants (n = 3998 – Scopus). The subject warrants immediate rigorous research because of the undesirable effects of excess phosphate in water bodies. This review will thus facilitate the construction of a roadmap for further developments and the expansion of this challenging area of research. [ABSTRACT FROM AUTHOR]

In this study, biochar, a carbonaceous solid material produced from three different waste sources (poultry litter, rice husk and pulp and paper mill sludge) was utilized to replace cement content up to 1% of total volume and the effect of individual biochar mixed with cement on the mechanical properties of concrete was investigated through different characterization techniques. A total of 168 samples were prepared for mechanical testing of biochar added concrete composites. The results showed that pulp and paper mill sludge biochar at 0.1% replacement of total volume resulted in compressive strength close to the control specimen than the rest of the biochar added composites. However, rice husk biochar at 0.1% slightly improved the splitting tensile strength with pulp and papermill sludge biochar produced comparable values. Biochar significantly improved the flexural strength of concrete in which poultry litter and rice husk biochar at 0.1% produced optimum results with 20% increment than control specimens. Based on the findings, we conclude that biochar has the potential to improve the concrete properties while replacing the cement in minor fractions in conventional concrete applications. [ABSTRACT FROM AUTHOR]

To enhance the effectiveness of polyvinyl alcohol (PVA) coated fertilizers, a novel slow-release fertilizer was developed using biochar and waterborne copolymer of PVA and polyvinylpyrrolidone (PVP) as coating materials. The effects of botanical origins and doses of biochar as well as copolymer concentrations on biochar-copolymer structures and properties were investigated. Our results indicated that the water absorbency of blend films differing in biochar origins showed different responses to these three factors. Generally, biochar decreased water absorbency of copolymer with an increased degradability, and contributed to improving the slow-release property of coated urea. In particular, rice biochar-based copolymer (S5 film) had less hydrophilic OH bonds and encapsulated urea granules more compactly and densely. The urea particles coated with rice biochar-based copolymer (S5 film) exhibited an excellent release behavior of 65.28% nutrient leaching on the 22th day. Therefore, this work has demonstrated the potential of biochar-based copolymer from different botanical biochar for improving the effectiveness of fertilizers. [ABSTRACT FROM AUTHOR]

This paper investigates the ability of the phosphoric acid functionalized Prunus armeniaca stones biochar (AsPhA) prepared by thermochemical activation to remove lead (Pb 2 + ), cadmium (Cd 2 + ), nickel (Ni 2 + ), naproxen and chlorophenols from aqueous wastes. The engineered biochar was characterized using the Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy and Brunauer, Emmett and Teller technique. The batch studies were performed by varying the initial pH of the solution (2–9), adsorbent dosage (0.2–10 g L − 1 ), contact time (5–60 min), temperature (22, 32 and 42 °C) and initial adsorbate concentration (5–500 mg L − 1 ). With the optimal process conditions, the adsorption efficiency was over 95% (100 mg L − 1 ). The results were fitted with three kinetic and three equilibrium theoretical adsorption models. The adsorption process has good correlation with pseudo-second-order reaction kinetics. Adsorption mechanism was found to be controlled by pore, film and particle diffusion, throughout the entire adsorption period. The monolayer adsorption capacities were found to be 179.476, 105.844 and 78.798 mg g − 1 for Pb 2 + , Cd 2 + and Ni 2 + , respectively. Thermodynamic parameters such as Gibbs energy, enthalpy and entropy were also calculated. Additionally, preliminary results indicated a strong affinity of the biochar for selected organic micropollutants: naproxen and chlorophenols. Based on desorption study results, biochar was successfully regenerated in 3 cycles with diluted phosphoric acid produced as a waste stream during washing of the biochar after thermochemical activation. The experimental results were applied in a two-stage completely stirred tank reactor design. Cost estimation of AsPhA production substantiated its cost effectiveness and adsorption costs of selected pollutants were 5 times lower than with the commercial activated carbons. Based on the low-cost and high capacity, engineered biochar can be used as a highly efficient eco-friendly adsorbent for removal of heavy metal and organic micropollutants from wastewaters systems. [ABSTRACT FROM AUTHOR]

Nitrogen (N) losses through gaseous emission of ammonia (NH 3 ) and nitrous oxide (N 2 O) can contribute to both economic loss and environmental degradation. This study examined the effect of biochar and a chemical nitrification inhibitor, dicyandiamide (DCD), on N transformation and N losses via gaseous emission of NH 3 and N 2 O from agricultural soils treated with a range of organic and inorganic N sources. The addition of DCD reduced N 2 O emission from both organic and inorganic N sources treated soils by 75%, but increased ammonium (NH 4 + ) concentration and subsequently induced high NH 3 emission from the soils. In contrast, the addition of biochar reduced both N 2 O and NH 3 emissions from organic and inorganic N sources treated soils by 23% and 43%, respectively. The effectiveness of biochar and DCD in reducing NH 3 volatilization and N 2 O emission depends on the nature of the N sources and their initial mineral N concentration. The study demonstrated that biochar can be used to mitigate N losses resulting from NH 3 volatilization and N 2 O emission. [ABSTRACT FROM AUTHOR]

The surplus of exogenous and endogenous phosphate in submerged paddy fields could increase the risk of algal blooms, the photosynthesis of which might further influence the redox processes of iron. This work investigated the effects of biochar on photosynthetic microorganism growth and iron redox under different phosphate (P) levels to understand the dynamics of P and thereby control non-point source pollution by biochar addition. Paddy soils were incubated anaerobically with phosphate and biochar addition under controlled illumination conditions to determine the variation in chlorophyll a ( Chl a ), ferrous iron [Fe(II)], soil pH and water-soluble phosphate (W-P) with incubation time. Biochar addition significantly inhibited the photosynthetic microorganism growth, with Chl a decreased by 4.74–15.78 mg·g − 1 when compared with the control. Fe(III) reduction was significantly stimulated in response to biochar addition, while Fe(II) oxidation was inhibited because of the suppression of photosynthetic microorganism growth. The enhanced Fe(III) reduction and suppressed Fe(II) oxidation decreased the P solubility in the tested soils. These findings provide a cost-effective approach for inhibiting photosynthetic microorganism growth in paddy field and valuable insight into the effect of iron cycling on P retention for further management of eutrophication from exogenous and endogenous P loading. [ABSTRACT FROM AUTHOR]

The incorporation of biochar into soil has been proposed as a strategy for enhancing soil fertility and crop productivity. However, there is limited information regarding the responses of soil respiration and the C, N and P cycles to the addition of apple branch biochar at different rates to soil with different levels of N. A 108-day incubation experiment was conducted to investigate the effects of the rate of biochar addition (0, 1, 2 and 4% by mass) on soil respiration and nutrients and the activities of enzymes involved in C, N and P cycling under two levels of N. Our results showed that the application of apple branch biochar at rates of 2% and 4% increased the C-mineralization rate, while biochar amendment at 1% decreased the C-mineralization rate, regardless of the N level. The soil organic C and microbial biomass C and P contents increased as the rate of biochar addition was increased to 2%. The biochar had negative effects on β-glucosidase, N -acetyl-β-glucosaminidase and urease activity in N-poor soil but exerted a positive effect on all of these factors in N-rich soil. Alkaline phosphatase activity increased with an increase in the rate of biochar addition, but the available P contents after all biochar addition treatments were lower than those obtained in the treatments without biochar. Biochar application at rates of 2% and 4% reduced the soil nitrate content, particularly in N-rich soil. Thus, apple branch biochar has the potential to sequester C and improve soil fertility, but the responses of soil C mineralization and nutrient cycling depend on the rate of addition and soil N levels. [ABSTRACT FROM AUTHOR]

The aim of this study was to reveal the mechanisms on how biochar reduces bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in tuberous vegetables. Corn straw-derived biochar pyrolyzed at 300 °C (CB300) or bamboo-derived biochar pyrolyzed at 700 °C (BB700) was amended into PAH-contaminated soil planted with carrot ( Daucus carota L.). After 150 days, 2% CB300 or 2% BB700 amendments significantly reduced the bioaccumulation of PAHs in carrot root ( p < 0.05), especially for high-molecular-weight PAHs. In the non-rhizosphere, either CB300 or BB700 suppressed PAH dissipation and decreased the bioavailability via adsorption processes. Compared to the control, the total concentration of PAHs in the rhizosphere was higher in the 2% BB700 treatment but the bioavailable concentration was lower. This indicates that BB700 decreased the bioavailability of PAHs primarily via immobilization (adsorption processes). By contrast, the total and bioavailable PAH concentrations were both lower in the 2% CB300 treatment than those in the control. The abundance of bacteria such as Arthrobacter and Flavobacterium and the total number of genes playing important roles in microbial PAH degradation processes increased significantly ( p < 0.05), which were likely responsible for the rapid dissipation of PAHs in the 2% CB300 treatment in the rhizosphere. These results indicate that CB300 decreased the PAH bioavailability primarily via increasing degradation of PAHs by indigenous microorganisms. The two biochars both showed better effectiveness at reducing the bioavailability of high-molecular-weight PAHs than the low-molecular-weight PAHs in the rhizosphere. Therefore, the mechanisms on how biochar reduces the PAH uptake into carrot are dependent on the type of biochar (e.g., pyrolysis temperature and feedstock) and root presence. [ABSTRACT FROM AUTHOR]

Biochar samples produced from rice straw by pyrolysis at different temperatures (400 °C and 800 °C) and under different atmospheres (N 2 and CO 2 ) were applied to lettuce growth in a ‘preparation-application’ system. The conversion of potassium in the prepared biochar and the effect of the temperature used for pyrolysis on the bioavailability of potassium in the biochar were investigated. Root samples from lettuce plants grown with and without application of biochar were assayed by X-ray photoelectron spectroscopy (XPS). The optimal conditions for preparation of biochar to achieve the maximum bioavailability of potassium (i.e. for returning biochar to soil) were thus determined. Complex-K, a stable speciation of potassium in rice straw, was transformed into potassium sulfate, potassium nitrate, potassium nitrite, and potassium chloride after oxygen-limited pyrolysis. The aforementioned ionic-state potassium species can be directly absorbed and used by plants. Decomposition of the stable speciation of potassium during the pyrolysis process was more effective at higher temperature, whereas the pyrolysis atmosphere (CO 2 and N 2 ) had little effect on the quality of the biochar. Based on the potassium speciation in the biochar, the preparation cost, and the plant growth and rigor after the application of returning biochar to soil, 400 °C and CO 2 atmosphere were the most appropriate conditions for preparation of biochar. [ABSTRACT FROM AUTHOR]

The study investigates the role of biochar and/or compost in mitigating the toxic effects of pyrene in soils using reproduction of nematodes and porewater concentration as measures of pyrene toxicity and bioavailability, respectively. Two soils were spiked with increasing levels of pyrene to achieve a concentration-response relationship for the reproduction of Caenorhabditis elegans . The observed EC50 values (pyrene concentration causing 50% inhibition of reproduction) were 14 mg/kg and 31 mg/kg (dry mass) for these soils, corresponding to equilibrium porewater concentrations of 37 μg/L and 47 μg/L, respectively. Differences in organic carbon content were not sufficient to explain the variability in toxicity between the different soils. Soils causing a significant inhibition of reproduction were further amended with 10%-compost, 5%-biochar, or both, and the effects on reproduction and porewater concentration determined. Combined addition of compost and biochar was identified as the most effective strategy in reducing pyrene concentration in soil porewater, which was also partly reflected in soil toxicity. However, porewater concentrations predicted only 52% of pyrene toxicity to nematodes, pointing to particle-bound or dietary exposure pathways. Capsule: Amending pyrene-spiked soil with biochar and compost effectively reduced pyrene porewater concentrations and toxicity to nematodes, which were significantly related. [ABSTRACT FROM AUTHOR]