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Cadmium (Cd) contamination in paddy soils means that the rice produced there may be unsafe for human consumption. A hydroponic study was conducted to enrich rice seedlings with zinc (Zn) or manganese (Mn), and the uptake and transport characteristics of Cd in these Zn- and Mn-rich seedlings were subsequently investigated using a greenhouse pot trial. The results showed that hydroponic cultivation in 10–50 µmol L–1 Zn (ZnSO4·7H2O) or 50–250 µmol L–1 Mn (MnSO4·H2O) for 30 d had no significant impact on rice growth, while the accumulation of Zn and Mn was 7.31–18.5 and 25.4–47.7 times higher, respectively, than in the control (no Zn or Mn addition). The accumulation of Cd in the Zn- and Mn-rich rice plants was 26.3%–38.6% and 34.4%–44.5% lower than that in the control, respectively, and the translocation factors of Cd from roots to shoots also decreased by 23.3%–41.3% and 25.3%–37.0%, respectively, after transplanting to Cd-contaminated soils. Furthermore, the relative expression levels of OsIRT1 (Oryza sativa iron-regulated transporter 1) were downregulated by 40.1%–59.3% and 16.0%–25.9%, respectively, in the Zn- and Mn-rich seedling roots. This downregulation may indicate a possible mechanism contributing to the reductions in Cd absorption. Field experiments confirmed that the Zn- and Mn-rich seedlings produced brown rice (unpolished rice grains) with significantly decreased concentrations of Cd (34.2%–44.4%). This study provides an innovative method for reducing the food safety risks from rice grown on slightly to moderately Cd-contaminated paddy soils.

Three Ni-Al2O3 catalysts were prepared, in planetary ball-milling machine, by the mechanochemical method with Al(NO3)3·9H2O as the aluminum precursor, (NH4)2CO3 as the precipitant, and Ni(NO3)2·6H2O, NiCl2·6H2O, and Ni(CH3COO)2·4H2O as nickel precursors (the corresponding catalysts were labeled as Ni-NO, Ni-Cl, and Ni-Ac). The prepared catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), and N2 adsorption–desorption technologies, and CO methanation performance evaluation was carried out for the catalysts. Results showed that the catalyst with Ni(NO3)2·6H2O as the precursor presented good Ni dispersibility and a small Ni grain size of 6.80 nm. CO conversion, CH4 selectivity, and yield of the catalyst were as high as 78.8, 87.9, and 69.8%, respectively. Carbon deposition analysis from temperature-programmed hydrogenation (TPH) characterization showed that the H2 consumption peak area of the three samples followed the order: Ni-NO (2886.66 au) < Ni-Cl (4389.97 au) < Ni-Ac (5721.65 au), indicating that the Ni-NO catalyst showed higher resistance to carbon deposition, which might be due to its small Ni grain size.

Simultaneous imaging, diagnosis, and therapy can offer an effective strategy for cancer treatment. However, the complex probe design, poor drug release efficiency, and multidrug resistance remain tremendous challenges to cancer treatment. Here, a novel one-two-three system is built for enhanced imaging and detection of miRNA-21 (miR-21) overexpressed in cancer cell and chemogene therapy. The system consists of dual-mode DNA robot nanoprobes assembled by two types of hairpin DNAs and three-way branch DNAs modified on gold nanoparticles, with intercalating anticancer drugs (doxorubicin), into DNA duplex GC base pairs. In the system, via intracellular ATP-accelerated cyclic reaction triggered by miR-21, fluorescence and SERS signals were alternated with DNA structure switch, and the precise SERS detection of miRNA and fluorescence imaging oriented "on-demand" release of two types of anticancer drugs (anti-miR-21 and Dox) are achieved. Thus, "one-two-three" means one kind of miR-21-triggered endogenous substance accelerated cyclic reaction, two modes of signal switch, and three functions including enhanced imaging, detection, and comprehensive treatment. The one-two-three system has some notable merits. First, ATP as an endogenous substance promotes DNA structure switching and accelerates the cyclic reaction. Second, the treatment with a dual-mode signal switch is more reliable and accurate and can provide more abundant information than a single-mode treatment platform. Thus, the imaging and detection of intracellular miRNA and effective comprehensive therapy are realized. In vivo results indicate that the system can provide new insights and strategies for diagnosis and therapy.

MicroRNAs (miRNAs) play important roles in biological processes. Designing a sensitive, selective, and rapid method of miRNA detection is crucial for biological research. Here, with a reciprocal signal amplification (RSA) probe, this work established a novel surface-enhanced Raman scattering (SERS)-microfluidic approach for the quantitative analysis of miRNA. First, via a DNAzyme self-assemble cycle reaction, two types of SERS signals produce amplified reciprocal changes. The sum of the absolute signal value is first adopted for the quantitative analysis of miRNA, which results in an enhanced response and a reduced blank value. Furthermore, the assay is integrated in an electric drive microfluidic mixing reactor that enables physical mixing and enriching of the reactants for more rapid and enhanced detection sensitivity. The protocol owns the merits of the SERS technology, amplified reciprocal signals, and a microfluidic chip, with a detection limit of 2.92 fM for miR-141 in 40 min. In addition, successful determination of miRNA in a variety of cells proved the practicability of the assay. Compared with the reported strategies for miRNA analysis, this work avoids a complex and time-consuming procedure and enhances the sensitivity and specificity. The method opens a promising way for biomolecular chip detection and research.

Coagulation dysfunction in critically ill patients with coronavirus disease 2019 (COVID-19) has not been well described, and the efficacy of anticoagulant therapy is unclear. In this study, we retrospectively reviewed 75 fatal COVID-19 cases who were admitted to the intensive care unit at Jinyintan Hospital (Wuhan, China). The median age of the cases was 67 (62–74) years, and 47 (62.7%) were male. Fifty patients (66.7%) were diagnosed with disseminated intra-vascular coagulation. Approximately 90% of patients had elevated D-dimer and fibrinogen degradation products, which decreased continuously after anticoagulant treatment and was accompanied by elevated albumin (all P

Understanding the mercury (Hg) methylation process is important for the management of paddy soils contaminated by Hg. In this work, samples of eighteen paddy soils with varying soil properties were spiked with inorganic Hg and subjected to a 90 d flooding period. Soil pH and redox potential (Eh) were measured in situ at intervals, and soils were sampled for the analysis of methylmercury (MeHg). The Hg methylation efficiency increased with flooding time and reached a relatively steady state at 30 d of incubation, ranging from 0.08% to 2.52%, and was significantly correlated with the in situ soil pH and Eh. The Elovich equation could adequately describe the kinetic production of MeHg. MeHg production was well predicted by the in situ soil pH and Eh of flooded soils, in addition to the organic matter content of air-dried soil samples and flooding time. The two predictive models explained 78% and 68% of the variability of the Hg methylation efficiency. The results suggested that the methylation of inorganic Hg in paddy soils after flooding can be predicted as a function of routinely measured soil properties and flooding time, a correlation that can be utilized to improve understanding of the extent of Hg methylation and the management of Hg-contaminated paddy soils.

Manganese (Mn) has the potential to reduce cadmium (Cd) uptake by rice; however, the efficiency depends on its soil availability. Therefore, this study designed a slow-release Mn fertilizer by employing a polyacrylate coating. Pot trials were conducted to study the effects of coated-Mn and uncoated-Mn alone or in combination with lime on the dynamics of soil dissolved-Mn and available Cd, and the transportation of Mn and Cd within rice. The results showed that coated-Mn declined the release of Mn until the 7th day of application; however, it consistently supplied more dissolved-Mn than uncoated-Mn. As a result, coated-Mn induced a greater Cd reduction (45.8%) in brown rice than uncoated-Mn (9.7%). The total Cd of rice and its proportion in brown rice were greatly reduced by coated-Mn, indicating the inhibition of root uptake and interior transport of Cd. Additionally, lime addition prominently increased the soil pH and decreased the CaCl2-extractable Cd (90.1-93.9%). However, since lime reduced the soil dissolved-Mn, downregulated the OsHMA3 expression and upregulated the OsNramp5 expression, brown rice Cd was reduced by only 43.0%. The combined addition of lime and coated-Mn alleviated the liming effect on soil Mn and gene expression in roots, thereby reducing brown rice Cd by 71.5%.

The expression of microRNAs (miRNAs) is critical in gene regulation and has been counted into disease diagnosis marks. Precise imaging and quantification of miRNAs could afford the important information for clinical diagnosis. Here, two smart binary star ratio (BSR) probes were designed and constructed, and miRNA triggered the connection of the binary star probes and the reciprocal changes of dual signals in living cells. This multifunctional probe integrates fluorescence and surface enhanced Raman scattering (SERS) imaging, with enzyme-free numerator signal amplification for dual-mode imaging and dual-signal quantitative analysis of miRNA. First, compared with the single-mode ratio imaging method, using fluorescence-SERS complementary ratio imaging, this probe enables more accurate imaging contrast for direct visualization signal changes in living cells. Multiscale information about the dynamic behavior of miRNA and the probe is acquired. Next, via SERS reverse signal ratio response and a novel enzyme-free numerator signal amplification, the amplified signal and reduced black value were achieved in the quantification of miRNA. More importantly, BSR probes showed good stability in cells and were successfully used for accurate tracing and quantification of miR-203 from MCF-7 cells. Therefore, the reported BSR probe is a potential tool for the reliable monitoring of biomolecule dynamics in living cells.

The application time and soil pH are key to manganese (Mn) bioavailability, which may influence Mn effects on cadmium (Cd) accumulation in rice. Accordingly, this study investigated the effects of Mn application at different stages, alone or with basal liming, on Cd accumulation in rice through pot and field experiments. The results showed that basal Mn application maximally elevated soil dissolved Mn, and increasing Mn accumulation in rice by 140%-367% compared to the control. Additionally, basal or tillering applications had better effects on enhancing iron manganese plaque (IMP) and inhibiting CaCl2-extractable Cd than later applications. Therefore, basal and tillering Mn reduced brown rice Cd by 24.6% and 18.9% compared to the control, respectively. Liming reduced CaCl2-extractable Cd by 83.3% compared to the control but inhibited soil dissolved Mn (25.8%-76.6%) and IMP (28.9%-29.7%), resulting in only a 41.7% reduction in brown rice Cd. Liming combined with tillering Mn maximally reduced brown rice Cd by 67.4%, structural equation modeling revealed CaCl2-extractable Cd and manganese plaque played the greatest positive and negative roles, respectively. Therefore, basal liming and tillering application of Mn is most effective at reducing rice Cd through inhibition of Cd bioavailability and alleviation of IMP reduction.

Understanding the arsenic (As) aging process is important for predicting the environmental behavior of exogenous As in paddy soils. In this work, samples of sixteen paddy soils with various soil properties were spiked with two concentrations (30 and 100 mg kg−1) of arsenate and subjected to a 360 day-long incubation under continuous flooding condition. Soil available As extracted by 0.05 M NH4H2PO4 was monitored through the aging process. Results showed that the available As%, the percentage of remaining available As in aged soils to added total As, fell from 44.2% to 41.9% on the 1st day to 22.0% and 23.0% on the 115th day for the low and high As spiked soils, respectively, then it remained basically unchanged after the 115th day. The pseudo-second order equation could adequately describe the aging kinetics of exogenous As in paddy soils. There was no significant difference in As aging parameters between the two spiked concentrations. Contents of soil free Al and Mn oxides, clay and cation exchange capacity strongly affected the aging rate of exogenous As. An empirical model, incorporating soil pH, cation exchange capacity, Olsen-P and flooding time, was developed to predict well the change of soil available As% during aging process (R2 = 0.711). The model could be potentially utilized to manage As-contaminated paddy fields and normalize ecotoxicity and bioaccumulation datasets in attempt to derive more widely applicable soil environmental quality criteria for As.

Background: Dilated cardiomyopathy (DCM) is considered as the most common form of non-ischemic cardiomyopathy with a high mortality worldwide. Cytoskeleton protein Cypher plays an important role in maintaining cardiac function. Genetic studies in human and animal models revealed that Cypher is involved in the development of DCM. However, the underlying molecular mechanism is not fully understood. Accumulating evidences suggest that apoptosis in myocytes may contribute to DCM. Thus, the purpose of this study is to define whether lack of Cypher in cardiomyocytes can elevate apoptosis signaling and lead to DCM eventually. Methods and Results: Cypher-siRNA sufficiently inhibited Cypher expression in cardiomyocytes. TUNEL-positive cardiomyocytes were increased in both Cypher knockdown neonatal rat cardiomyocytes and Cypher knockout mice hearts, which were rare in the control group. Flow cytometry further confirmed that downregulation of Cypher significantly increased myocytes apoptosis in vitro. Cell counting kit-8 assay revealed that Cypher knockdown in H9c2 cells significantly reduced cell viability. Cypher knockdown was found to increase cleaved caspase-3 expression and suppress p21, ratio of bcl-2 to Bax. Cypher-deficiency induced apoptosis was linked to downregulation of Akt activation and elevated p-p38 MAPK accumulation. Pharmacological activation of Akt with SC79 attenuated apoptosis with enhanced phosphorylation of Akt and reduced p-p38 MAPK and Bax expression. Conclusions: Downregulation of Cypher participates in the promotion of cardiomyocytes apoptosis through inhibiting Akt dependent pathway and enhancing p38 MAPK phosphorylation. These findings may provide a new potential therapeutic strategy for the treatment of DCM.

The toxicity of low-level arsenic (As)-contaminated soil is not well understood. An integrated proteomic and metabolomic approach combined with morphological examination was used to investigate the potential biological toxicity of As-contaminated soil based on an exposure experiment with the earthworm Eisenia fetida. The results showed that the earthworm hindgut accumulated high As concentrations resulting in injury to the intestinal epithelia, chloragogenous tissues and coelom tissues. Furthermore, As-contaminated soil induced a significant increase in betaine levels and a decrease in dimethylglycine and myo-inositol levels in the earthworms, suggesting that the osmoregulatory metabolism of the earthworms may have been disturbed. The significantly altered levels of asparagine and dimethylglycine were proposed as potential biomarkers of As-contaminated soil. The upregulation of soluble calcium-binding proteins and profilin, the downregulation of sodium/potassium-transporting ATPase, and the proteins changes identified by gene ontology enrichment analysis confirmed that the earthworms suffered from osmotic stress. In addition, the significant changes in glycine-tRNA ligase activity and coelomic tissue injury revealed that As accumulation may disturb the earthworm immune system. This work provided new insight into the proteomic and metabolic toxicity of low-level As-contaminated soil ecosystems in earthworms, extended our knowledge of dual omics and highlighted the mechanisms underlying toxicity.

The inhibition of cadmium (Cd) absorption by selenium (Se) in rice may be associated with iron plaque (IP) formation, but the driving mechanisms are still unclear. This study investigated the effects of Se on the growth, oxidative toxicity, radial oxygen loss (ROL), IP formation, and Cd absorption of rice exposed to Cd. The results of this study showed that Cd stress elevated the levels of O2 – and H2O2 and depressed superoxide dismutase (SOD) and catalase (CAT) activities. The maximum ROL and IP were reduced by 43.3 % and 74.5 %, respectively. However, Se alleviated Cd toxicity by stimulating SOD and CAT activities by scavenging O2 – and H2O2 and enhancing the ROL profiles. Under culture conditions without Fe2+, Se had no impact on the total Cd levels in rice (TCd). However, with the addition of Fe2+, TCd was significantly reduced by 23.3 % due to the enhancement of IP formation by Se. These results indicated that Se can reduce Cd accumulation in rice in the presence of Fe2+ treatments. However, Se just alleviated Cd toxicity in the absence of Fe2+ treatments. The enhancement of ROL was a potential reason for the elevated IP formation induced by Se.

The application of selenite to soil has increasingly been used to produce Se-enriched food. This study investigated the biofortification characteristics of Se in rice after application of selenite to soil at different growth stages. The results showed that the application of Se during booting stage resulted in the highest concentration of Se in brown rice due to the highest upward translocation of Se. More than 90% of Se in the brown rice was organic species, with selenomethionine predominated. The proportion of selenomethionine in the brown rice decreased with the delay in application time. The rice grown in the acidic soil had higher Se concentrations than in the neutral soil. With increasing soil Cd level, Se accumulation and the proportion of Se-methylselenocysteine in the brown rice were reduced. This study provides a theoretical basis for the production of Se-enriched rice in clean soil or slightly to moderately Cd-contaminated soil.

Chemical immobilization is a practical approach to remediate heavy metal contamination in agricultural soils. However, the potential remobilization risks of immobilized metals are a major environmental concern, especially in acid rain zones. In the present study, changes in the immobilization efficiency of several amendments as affected by simulated soil acidification were investigated to evaluate the immobilization remediation stability of several amendments on two cadmium (Cd) contaminated soils. Amendments (hydrated lime, hydroxyapatite and biochar) effectively immobilized Cd, except for organic fertilizer, and their immobilizations were strongly decreased by the simulated soil acidification. The ratio of changes in CaCl2-extractable Cd: pH (△CaCl2-Cd/△pH) can represent the Cd remobilization risk of different amended soils. Hydroxyapatite and biochar had a stronger durable immobilizing effect than did hydrated lime, particularly in soil with a lower pH buffering capacity, which was further confirmed by the Cd concentration and accumulation in lettuce. These results can be attributed to that hydroxyapatite and biochar transformed greater proportions of exchangeable Cd to other more stable fractions than lime. After 48 weeks of incubation, in soil with a lower pH buffering capacity, the immobilization efficiencies of lime, hydroxyapatite, biochar and organic fertilizer in the deionized water group (pH 6.5) were 71.7%, 52.7%, 38.6% and 23.9%, respectively, and changed to 19.1%, 33.6%, 26.5% and 5.0%, respectively, in the simulated acid rain group (pH 2.5). The present study provides a simple method to preliminarily estimate the immobilization efficiency of amendments and predict their stability in acid rain regions before large-scale field application. In addition, hydrated lime is recommended to be combined with other acid-stable amendments (such as hydroxyapatite or biochar) to remediate heavy metal-contaminated agricultural soils in acid precipitation zones.

Soil cadmium (Cd) contamination has become a serious problem in China. This study was conducted to test the effects of basal application of hydrated lime and iron fertilizer alone or together and topdressing of iron fertilizer at the tillering stage alone or coupled with basal application of hydrated lime, on reducing the accumulation of Cd in brown rice grown in an acidic paddy field slightly contaminated with Cd. The results showed that Cd in brown rice (BR-Cd) was dependent on not only the pH increase and CaCl2-extractable Cd reduction in the soil due to lime amendment but also Cd sequestration by the iron plaque on root surfaces. However, lime significantly decreased the amounts of Fe and Cd in the iron plaque on the surface of rice root. Topdressing of ferrous sulfate at the tillering stage resulted in the highest Fe and Cd sequestration in the iron plaque. Compared with the control (0.71 mg kg−1 BR-Cd), the basal application of lime and ferrous sulfate alone or together reduced BR-Cd by 45.8%, 18.3%, and 53.1%, respectively; topdressing of ferrous sulfate alone reduced BR-Cd by 23.6%, and topdressing of ferrous sulfate at the tillering stage coupled with basal application of lime yielded the lowest BR-Cd level with a 74.6% reduction. This result was further confirmed by field experiments at two sites in the following year.

Mercury is a globally distributed toxicant to aquatic animals and mammals. However, the potential risks of environmental relevant mercury in terrestrial systems remain largely unclear. The metabolic profiles of the earthworm Eisenia fetida after exposure to soil contaminated with mercury at 0.77 ± 0.09 mg/kg for 2 weeks were investigated using a two-dimensional nuclear magnetic resonance-based (1H-13C NMR) metabolomics approach. The results revealed that traditional endpoints (e.g., mortality and weight loss) did not differ significantly after exposure. Although histological examination showed sub-lethal toxicity in the intestine as a result of soil ingestion, the underlying mechanisms were unclear. Metabolite profiles revealed significant decreases in glutamine and 2-hexyl-5-ethyl-3-furansulfonate in the exposed group and remarkable increases in glycine, alanine, glutamate, scyllo-inositol, t-methylhistidine and myo-inositol. More importantly, metabolic network analysis revealed that low mercury in the soil disrupted osmoregulation, amino acid and energy metabolisms in earthworms. A metabolic net link and schematic diagram of mercury-induced responses were proposed to predict earthworm responses after exposure to mercury at environmental relevant concentrations. These results improved the current understanding of the potential toxicity of low mercury in terrestrial systems.

The inhibitory effect of selenium (Se) on cadmium accumulation in brown rice (BR-Cd) is controversial, which may be related to the Se application time. The optimum Se application time for reducing the BR-Cd is investigated. A pot experiment was conducted to examine the changes in the dynamics of iron plaque on root surface and Cd accumulation in rice as Se was applied at different growth stages to two Cd-contaminated soils, and explore its mechanisms. Field trials were conducted to verify the results. Iron plaque formed mainly at the middle stage (tillering to booting stage) of rice and then decreased at the mature stage. Se application at the seeding, tillering, and booting stages reduced the BR-Cd by 10.6–18.4%, 14.9–23.7%, and 10.8–20.9% in the neutral soil, 18.3–32.4%, 40.3–63.0%, and 22.7–40.6% in the acid soil, respectively. Two field trials demonstrated that tillering application of Se caused significant reductions (27.1–35.1%) of BR-Cd. Tillering stage is optimal for Se application to reduce BR-Cd, mainly because tillering application of Se causes the maximum amount iron plaque at the booting stage, maximumly inhibit Cd uptake by the root; meanwhile, the transport of Cd from the root to brown rice is inhibited.

Cadmium (Cd) is an environmental toxicant with high rates of soil-plant transfer. It is essential to establish an accurate soil threshold for the implementation of soil management practices. This study takes root vegetable as an example to derive soil thresholds for Cd based on the food quality standard as well as health risk assessment using species sensitivity distribution (SSD). A soil type-specific bioconcentration factor (BCF, ratio of Cd concentration in plant to that in soil) generated from soil with a proper Cd concentration gradient was calculated and applied in the derivation of soil thresholds instead of a generic BCF value to minimize the uncertainty. The sensitivity variations of twelve root vegetable cultivars for accumulating soil Cd and the empirical soil-plant transfer model were investigated and developed in greenhouse experiments. After normalization, the hazardous concentrations from the fifth percentile of the distribution based on added Cd (HC5add) were calculated from the SSD curves fitted by Burr Type III distribution. The derived soil thresholds were presented as continuous or scenario criteria depending on the combination of soil pH and organic carbon content. The soil thresholds based on food quality standard were on average 0.7-fold of those based on health risk assessment, and were further validated to be reliable using independent data from field survey and published articles. The results suggested that deriving soil thresholds for Cd using SSD method is robust and also applicable to other crops as well as other trace elements that have the potential to cause health risk issues.

Soil cadmium (Cd) contamination in China has become a serious concern due to its high toxicity to human health through food chains. A pot experiment was conducted to investigate the effects of hydrated lime (L), hydroxyapatite (H) and organic fertilizer (F) alone or in combination to remedy a mild (DY) and a moderate (YX) Cd contaminated agricultural soil under rice-wheat rotation. Results showed that crops grain yield and Cd concentration, soil pH, CaCl2 extractable Cd and Cd speciation were markedly affected by the amendments. In both cropping seasons, hydrated lime and hydroxyapatite significantly immobilized soil Cd, and hydroxyapatite, organic fertilizer significantly increased grain yield. Hydrated lime mainly increased soil carbonates bound Cd fractions resulted from 16.7% to 36.2% and from 16.8% to 28.3%, and hydroxyapatite increased Fe/Mn oxides Cd fractions from 19.3% to 33.4% and from 31.4% to 42.1% in the DY and YX soils, respectively; while organic fertilizer slightly increased soil exchangeable and organic matter bound Cd fractions. Besides, combined amendments contain alkaline materials and organic materials have the potential to decrease grain Cd and increase grain yield simultaneously. Therefore, in view of the effects of amendments on grain yield and Cd concentration, the cost as well as the potential benefits expected, combined amendments like hydrated lime + organic fertilizer, hydrated lime + hydroxyapatite + organic fertilizer are recommended in practical application. Mechanisms of Cd immobilization affected by amendments are mainly attributed to the changes in soil Cd availability and crops root uptake rather than internal translocation in plants.

The precise determination and characterization of soil acidity was the basis for a robust and realistic assessment of many biogeochemical processes. Samples of twenty paddy soils with varying soil properties were subjected to a successive flooding and drainage period in this work. The soil pH was measured in situ at intervals, and soil samples were collected after each pH measurement during drainage for an analysis of the moisture content. During the flooding period, the pH for soils with an initial pH 6.5, the pH first decreased and then increased to approximately 7.0. The changes were reversed during the drainage period, as the pH of acidic soils decreased linearly with the decreasing soil moisture content, while neutral-to-alkaline soils showed the opposite pattern. The developed predictive models indicated that the initial soil pH, cation exchange capacity, content of organic matter and flooding or drainage time were the main factors that controlled the change of soil pH after flooding and drainage. The models explained 82% and 67% of the soil pH variability after flooding and drainage, respectively. The predictive model of the soil pH change after flooding was further validated and was found to be reliable on the basis of a number of independent data points for which the predicted soil pH after flooding was within the 95% prediction intervals of the observations. The results suggested that the soil pH, which was determined in the laboratory using air-dried samples, could be corrected to the in situ pH through the developed predictive models.

Phenolic acids can enhance the mycotoxin production and activities of hydrolytic enzymes related to pathogenicity of soilborne fungus Fusarium oxysporum. However, characteristics of phenolic acid-degrading bacteria have not been investigated. The objectives of this study were to isolate and characterize bacteria capable of growth on benzoic and vanillic acids as the sole carbon source in the peanut rhizosphere. Twenty-four bacteria were isolated, and the identification based on 16S rRNA gene sequencing revealed that pre-exposure to phenolic acids before sowing shifted the dominant culturable bacterial degraders from Arthrobacter to Burkholderia stabilis-like isolates. Both Arthrobacter and B. stabilis-like isolates catalysed the aromatic ring cleavage via the ortho pathway, and Arthrobacter isolates did not exhibit higher C12O enzyme activity than B. stabilis-like isolates. The culture filtrate of Fusarium sp. ACCC36194 caused a strong inhibition of Arthrobacter growth but not B. stabilis-like isolates. Additionally, Arthrobacter isolates responded differently to the culture filtrates of B. stabilis-like isolates. The Arthrobacter isolates produced higher indole acetic acid (IAA) levels than B. stabilis-like isolates, but B. stabilis-like isolates were also able to produce siderophores, solubilize mineral phosphate, and exert an antagonistic activity against peanut root rot pathogen Fusarium sp. ACCC36194. Results indicate that phenolic acids can shift their dominant culturable bacterial degraders from Arthrobacter to Burkholderia species in the peanut rhizosphere, and microbial interactions might lead to the reduction of culturable Arthrobacter. Furthermore, increasing bacterial populations metabolizing phenolic acids in monoculture fields might be a control strategy for soilborne diseases caused by Fusarium spp.

Concentrations of heavy metals (Cu, Zn, Pb and Cd) were measured in leaves of twelve plant species from seven different locations in Shanghai, China. Unwashed and washed new and old leaves were considered, and the correlations among the heavy metal concentrations in soils and in plant leaves and deposited by the atmosphere were analyzed. In addition, scanning electron microscopy (SEM) was used to determine the stomatal density and structure of the leaves. The background site (Chenshan Botanical Garden) had lower mean metal concentrations than the other sites. The highest Cu contents were found in Nerium indicum and Platanus acerifolia , the highest Zn content was found in Pittosporum tobira , and the highest Pb and Cd contents were found in Cedrus deodara . The lowest heavy metal contents were found in Ginkgo biloba , potentially because Platanus acerifolia and Pittosporum tobira leaves have higher densities of stomata than on Ginkgo biloba leaves (according to SEM results). However, Magnolia grandiflora had the highest metal accumulation index (MAI) (4.27), and Cedrus deodara had the lowest MAI (1.53). When comparing the heavy metal contents in the washed leaf samples with the unwashed leaf samples, Nerium indicum captured more rare-earth elements (determined using the capture rate (CR)), including Cu (92.7%) and Zn (36.9%). Magnolia grandiflora had higher CR values for Pb (63.4%) and Cd (49.1%), and Cedrus deodara had lower CR values for Cu (0), Zn (8.90%), Pb (5.93%) and Cd (2.97%). In addition, the Cu, Zn, Pb and Cd in plant needles potentially originate from the soil, and the Cu, Zn, Pb and Cd in the leaves of broad-leaved plants potentially originate from bulk atmospheric deposition. This hypothesis is supported by the relationship between the heavy metal concentrations in the soils and the washed new and old leaves. In addition, the concentration factor (CF) of heavy metals supported this model.

A plot experiment was conducted to understand the response of the soil bacterial community to manure application rates and the relationship between the composition of bacterial community and soil chemical properties. The experiment involved gradients of manure combined with chemical fertilizer in red soils from granite, red sandstone and red clay between 2013 and 2015. The soil bacterial community composition was significantly affected by different manure rates. The relative abundances of Burkholderiaceae, Micrococcaceae and Streptomycetaceae were higher at low manure rates (1.75 to 3.5 t·ha−1·yr.−1), whereas the relative abundance of Xanthomonadaceae was higher at high manure rates (7 to 28 t·ha−1·yr.−1). Manure application increased the bacterial abundance but decreased the diversity when its rates were higher than 7, 14 and 14 t·ha−1·yr.−1 in soils from granite, red sandstone and red clay, respectively. Redundancy analysis revealed that soils from different parent materials had different bacterial communities with soil pH and available phosphorus (AP) being determinant factors. The peanut yields exhibited significantly positive correlations with the bacterial diversity in soil, implying the importance of bacterial diversity for soil productivity. Soil AP was correlated with bacterial diversity by parabolic equations and probably AP may be an indicator of declining bacterial diversity at high manure rates. The critical value were 39.71, 65.75 and 90.16 mg·kg−1 in soils from granite, red sandstone and red clay, respectively. This study suggests the importance of maintaining soil bacterial diversity under moderate and balanced applications of manure.

Plants, particularly their leaves, play an important role in filtering both gas-phase and particle-phase polycyclic aromatic hydrocarbons (PAHs). However, many studies have focused on the accumulation and adsorption functions of plant leaves, possibly underestimating the effects that plants have on air quality. Therefore, eight tree species from different locations in Shanghai were selected to assess PAH filtering (via adsorption and capture) using washed and unwashed plant leaves. The differences in the total PAH contents in the washed leaves were constant for the different species across the different sampling sites. The PAH levels decreased in the following order: industrial areas > traffic areas > urban areas > background area. The PAH compositions in the different plant leaves were dominated by fluorene (Fle), phenanthrene (Phe), anthracene (Ant), chrysene (Chr), fluoranthene (Flu), and pyrene (Pyr); notably, Phe accounted for 49.4-76.7% of the total PAHs. By comparing the PAH contents in the washed leaves with the PAH contents in the unwashed leaves, Pittosporum tobira (P. tobira), Ginkgo biloba (G. biloba), and Platanus acerifolia (P. acerifolia) were found to be efficient species for adsorbing PAHs, while Osmanthus fragrans (O. fragrans), Magnolia grandiflora (M. grandiflora), and Prunus cerasifera Ehrh. (P. cerasifera Ehrh.) were efficient species for capturing PAHs. The efficiencies of the plant leaves for the removal of PAHs from air occurred in the order of low molecular weight > medium molecular weight > high molecular weight PAHs.

As potent allelochemicals, phenolic acids are believed to be associated with soilborne diseases, and can influence plant-microbe interactions. Benzoic acid (BA) is one major phenolic acid found in peanut (Arachis hypogaea) root exudates. The objectives of this study were to estimate the BA degradation in the soil and its effects on soil bacterial and fungal communities and to detect the specific taxa responding to BA amendment. BA degradation was investigated by monitoring the BA retained in the soil using high-performance liquid chromatography (HPLC) and the CO2 production rate using gas chromatography (GC). The abundance and diversity of the bacterial and fungal communities were investigated by quantitative real-time PCR (qPCR) and Illumina MiSeq sequencing. The results showed that the BA concentration decreased significantly with an increased rate of CO2 production during the first 36 h after amendment, implying that the BA in the soil was quickly metabolized by the microbes. Quantitative PCR analysis further detected a significant increase in soil bacterial and fungal abundances in response to BA addition, but a reduced bacteria-to-fungi ratio. As a result of BA amendment, the relative abundance of Fusarium, Bionectria and Trichoderma was markedly increased, whereas Metarhizium was reduced. Moreover, BA (0.1 mmol L−1) promoted the mycelial growth, sporulation capacity and conidial germination of the peanut root rot pathogen Fusarium sp. in vitro. Among bacteria, the relative abundance of Betaproteobacteria was significantly increased in response to BA treatment, whereas the relative abundances of AD3 and Actinobacteria were reduced. A deeper taxonomic analysis of the Betaproteobacteria taxa showed a great increase in the abundance of the genus Burkholderia, from 0.71% to 10.12%, in response to BA amendment. Constructing clone libraries with the partial 16S rRNA genes of Burkholderia further demonstrated that BA amendment had modified the Burkholderia species composition. Our results highlight that the effects of BA in the soil are reflected by changes in populations of soil microbes and suggest that the response of specific microbes such as Fusarium and Burkholderia to BA might be associated with the development of soilborne diseases in monocultures.

1 H NMR-based metabolomics was used to profile the time-dependent metabolic responses of earthworms (Eisenia fetida) that were exposed to low-Pb-contaminated-soil (L-Pb-CS) for 28 days using an indoor culture. Earthworms were gathered after days 1, 7, 14, 21 and 28 of the exposure. The earthworm extracts were then analyzed using 500 MHz nuclear magnetic resonance. Spectrum interpretation, statistical analysis and plotting were performed using the “R” software. The metabolic trajectories, histopathological examination, Pb accumulation, survival rate and mean weights of the earthworms were evaluated to investigate and explain the possible mechanism of action. The results showed that the Pb concentrations of earthworms in the Pb exposure groups increased with longer exposure times. Pb treated groups showed varying degrees of histopathological damage. The metabolic response trajectories in the Pb treated groups were of a similar type but differed in the magnitudes of metabolite responses, which suggested that the responses of the Pb1 and Pb2 groups may involve the same metabolic mechanism. Earthworms may produce a toxic response on days 1–14, whereas a detoxification strategy was initiated during days 14–28 to adapt to the L-Pb-CS, as indicated by the negative maximum distance of metabolic trajectories. Specifically, the most serious damage in the histopathology examination and the most extreme values of metabolites were observed on the 14th day. The metabolic changes involved the amino acid, membrane, and energy metabolism of earthworms. Myo-inositol, 2-hexyl-5-ethyl-3-furansulfonate (HEFS), scyllo-inositol, succinate, alanine and maltose were found to be potential biomarkers for exposure to the L-Pb-CS. This study demonstrated that 1H NMR-based metabolomics along with metal accumulation and histological detection provide a reliable approach for interpreting time-dependent metabolic mechanisms in earthworms.

Sorption and desorption processes control the bioavailability of heavy metals in the environment. Soil incubation and batch experiments were conducted to evaluate the effects of soil amendments on sorption, and desorption of Cu2+ and Cd2+ in a contaminated acidic paddy soil. The study showed that limestone and silicon fertilizer increased Cu2+ and Cd2+ sorption 2.43- and 1.13-fold, which was higher than calcium magnesium phosphate, Chinese milk vetch, pig manure, and peat. The Freundlich equation fitted sorption of Cu2+ and Cd2+ better than the Langmuir and Temkin equations. High desorption percentages of sorbed Cu2+ (mean of 67.1%) and Cd2+ (mean of 78.2%) were observed from the contaminated soil. Limestone and silicon fertilizer significantly decreased the desorption percentage of sorbed Cu2+ to 11.4 and 40.0%, respectively, and significantly decreased the desorption percentage of sorbed Cd2+ to 42.5 and 61.0%, respectively. However, the other four amendments did not show significant impact. Increasing soil pH significantly increased contents of sorbed Cu2+ and Cd2+, and negatively influenced desorption of sorbed Cu2+ and Cd2+. Application of amendments changed Cu and Cd fractions in soils, which might affect the sorption and desorption of Cu2+ and Cd2+. The effects of soil amendments on sorption and desorption of heavy metals may be useful for predication of their remedy efficiency to heavy metal contamination.

The influence of manure application rate on the structure of the soil fungal community was investigated in a three-year plot experiment using high-throughput sequencing. In addition, soil environmental factor driving the variation of fungal community structure was explored by redundancy analysis of soil chemical properties. Pig manure at low rates of 1.75 or 3.5 t·ha−1 yr−1 or at high rates of 7, 14 or 28 t·ha−1 yr−1 in combination with chemical fertilizer was applied to red soils from three parent materials: granite (GR-soil), red sandstone (RS-soil) and red clay (RC-soil). The results indicated a higher fungal disease index of root rot in GR-soil than that in RS-soil or RC-soil, and higher manure application rates greatly decreased the incidence of peanut disease in GR-soil. The abundances of the most fungi at the order level, the number of OTUs (operational taxonomic units) and the diversity of the fungal community all sharply decreased with increasing manure application rate, and more significant decreases occurred especially at the low manure rates. Redundancy analysis and curve fitting revealed that the diversity of the fungal community was correlated with the increase in soil available phosphorus, exhibiting a striking exponential relationship with available phosphorus. It is suggested that producers should consider an appropriate manure rate as one tool for disease suppression due to its good impact in some soils. More research should probably be done to define what soil factors might play a role in determining when manure applications may have the disease suppressive impact.

Proper protocols for assessing the remediation effectiveness of contaminated soils are an important part of remediation projects. In the present study, the residual immobilization effectiveness of hydrated lime (L), hydroxyapatite (H), biochar (B) and organic fertilizer (F) alone and in combination was assessed by Eisenia fetida. The results showed that the application of amendments had no significant effect on the death rate and average fresh weight loss of earthworms. The earthworm Cd concentration increased with prolonged exposure time, however, the significant immobilization efficacy of amendments observed on the 7th day nearly disappeared after 28 days of exposure. The immobilization efficiencies, estimated by the earthworms internal Cd concentration, of L, H and B on the 7th day were 38.6%, 37.8% and 20.7%, respectively. These values decreased to 4.9%, 19.8% and 15.1%, respectively, on the 28th day. The detoxification effect of amendments was confirmed by the Cd subcellular fractionation in earthworms with lower proportions of Cd distributed in the metal-sensitive fractions in L, H and B treatments. The level of oxidative stress response of earthworms increased with exposure duration and amendments alleviated the oxidative damage induced by Cd to the earthworms. In addition, the pH and CaCl2–Cd in soils were both increased due to earthworm life activities and gut-related ingestion. In summary, the assessment of immobilization effectiveness of heavy metal-contaminated soils using Eisenia fetida was time-dependent. The immobilization efficacy of L and H performed better than B and F on the 7th day, while H and B performed better than L and F on the 28th day. Accordingly, the short-term earthworm exposure experiment (7 days) was recommended to be an alternative approach to time-consuming plant bioassays in assessment of reduced phytoavailability in chemical immobilization remediation. But the impact of earthworms on the immobilization effect of amendments needs to be considered in practical remediation.

Biochar is a stable carbon rich by-product synthesized through pyrolysis of plant and animal based biomass, and nano-biochar material has gained increasing attention due to its unique properties for environmental applications. In the present study, a simple cost-effective method for the synthesis of biochar nanoparticles through hydrothermally using agricultural residuals and by-products was developed. Both soybean straw and cattle manure were selected as the feedstock to produce the bulk-biochar. The synthesis procedure involved the digestion of the bulk-biochar with concentrated nitric acid and sulfuric acid in a high pressure condition using a hydrothermal reactor. The suspension was isolated using vacuum filtration with 0.22-μm membrane followed by drying at 65 °C in an oven. Scanning electron microscopy results revealed that both of the biochars had a well-developed porous structure following pyrolysis. Both transmission electron microscopy and the dynamic light scattering results of the hydrothermally treated biochar indicated that the soybean straw and cattle manure biochar nanodots had an average of 5-nm and 4-nm in size, respectively. Overall two raw materials produced 8.5–10% biochar nanodots. The present method presents a simple, quick and cost-effective method for synthesis of biochar nanodots. The method provided a useful tool discovering the applicability biochar nanodots for environmental applications. • Nano-biochar formation from bulk-biochar using hydrothermal reactor • Evaluate nano-biochar's environmental fate and behavior in soil and water • Synthesize multifunctional adsorbent using nano-biochar as primary material, Graphical abstract Image, graphical abstract

The fate of polycyclic aromatic hydrocarbons (PAHs) determines their potential risk in soil, which may be directly affected by abiotic conditions and indirectly through the changes in decomposer communities. In comparison, the indirect effects on the fate remain largely elusive. In this study, the fate of phenanthrene and benzo[a]pyrene and the corresponding bacterial changes were investigated in three contaminated farmland soils using a 14C tracer method and Miseq sequencing. The results showed that most benzo[a]pyrene was consistently extractable with dichloromethane (DCM) after the 60-day incubation (60.4%–78.2%), while phenanthrene was mainly mineralized to CO2 during the 30-day incubation (40.4%–58.7%). Soils from Guangzhou (GZ) showed a different distribution pattern of 14C-PAHs exemplified by low mineralization and disparate bound residue formation. The PAH fate in the Shenyang (SY) and Nanjing (NJ) soils were similar to each other than to that in the GZ soil. The fate in the GZ soil seemed to be linked to the distinct edaphic properties, such as organic matter content, however soil microbial community could have influenced the distribution pattern of PAHs. This potential role of microorganisms was reflected by the unique changes in the copy numbers of Gram positive RHDα gene, and by the distinct shifts in bacterial community composition during the incubation. A quite different shift in bacterial communities was found in the GZ microcosms which may influence PAH mineralization and non-extractable residue (NER) formation.

Cadmium (Cd) contamination in paddy fields has received extensive attention throughout the world, especially in China. In this study, treatments of a lime application with or without zinc sulfate as basal fertilizer, a basal or tillering application of zinc sulfate, and basal stabilization using lime combined with a tillering application of zinc sulfate were designed in a field trial to investigate their contributions to the uptake and translocation of Cd in rice plants. The results showed that basal stabilization using lime significantly decreased brown rice Cd by 42%; the CaCl2-extractable Cd in the soil was decreased by 46–51%, but the phytoavailability of Zn in the soil was also inhibited. The basal or tillering application of zinc sulfate significantly inhibited the upward transport of Cd (from the root to the shoot) while having no significant impact on CaCl2-extractable Cd; consequently, the concentration of Cd in the brown rice was reduced by only 17–25%. Compared with the lime application alone, the basal application of lime together with zinc sulfate did not further reduce the Cd in brown rice. However, basal stabilization using lime combined with the tillering application of zinc decreased the Cd in brown rice by 73%, which was attributed to the reduced CaCl2-extractable Cd and the competitive effect of Zn on Cd, in which the inhibition of the upward transport of Cd inside the root played an important role. Two field verification tests conducted during the next year also demonstrated that this combined method significantly decreased the level of Cd in brown rice.

Reliable empirical models describing lead (Pb) transfer in soil-plant systems are needed to improve soil environmental quality standards. A greenhouse experiment was conducted to develop soil-plant transfer models to predict Pb concentrations in carrot (Daucus carota L.). Soil thresholds for food safety were then derived inversely using the prediction model in view of the maximum allowable limit for Pb in food. The 2 most important soil properties that influenced carrot Pb uptake factor (ratio of Pb concentration in carrot to that in soil) were soil pH and cation exchange capacity (CEC), as revealed by path analysis. Stepwise multiple linear regression models were based on soil properties and the pseudo total (aqua regia) or extractable (0.01 M CaCl2 and 0.005 M diethylenetriamine pentaacetic acid) soil Pb concentrations. Carrot Pb contents were best explained by the pseudo total soil Pb concentrations in combination with soil pH and CEC, with the percentage of variation explained being up to 93%. The derived soil thresholds based on added Pb (total soil Pb with the geogenic background part subtracted) have the advantage of better applicability to soils with high natural background Pb levels. Validation of the thresholds against data from field trials and literature studies indicated that the proposed thresholds are reasonable and reliable.

To characterize the potential toxicity of low Pb- and Cd-contaminated arable soils, earthworms were exposed to Pb contaminated ferrosol, cambosol or Cd contaminated ferrosol for two weeks. Polar metabolites of earthworms were detected by nuclear magnetic resonance. Data were then analyzed with principal component analysis followed by orthogonal signal correction-partial least squares-discriminant analysis and univariate analysis to determine possible mechanisms for the changes in metabolites. The survival rates, metal concentrations and bioaccumulation factor (BAF) of the earthworms were also measured and calculated as auxiliary data. The results showed that the metabolite profiles were highly similar in Pb-contaminated ferrosol and cambosol (R2 = 0.76, p

A pot experiment was conducted to investigate the effects of selenium (Se) and hydrated lime (Lime), applied alone or simultaneously (Se+Lime), on growth and cadmium (Cd) uptake and translocation in rice seedlings grown in an acid soil with three levels of Cd (slight, mild, and moderate contamination). In the soil with 0.41 mg kg−1 Cd (slight Cd contamination), Se addition alone significantly decreased Cd accumulation in the root and shoot by 35.3 and 40.1%, respectively, but this tendency weakened when Cd level in the soil increased. However, Se+Lime treatment effectively reduced Cd accumulation in rice seedlings in the soil with higher Cd levels. The results also showed that Se application alone strongly increased Cd concentration in the iron plaque under slight Cd contamination, which was suggested as the main reason underlying the inhibition of Cd accumulation in rice seedlings. Se+Lime treatment also increased the ability of the iron plaques to restrict Cd uptake by rice seedlings across all Cd levels and dramatically decreased the available Cd concentration in the soil. These results suggest that Se application alone would be useful in the soil with low levels of Cd, and the effect would be enhanced when Se application is combined with hydrated lime at higher Cd levels.

The ecotoxicity of benzo[a]pyrene (BaP) to soil microorganisms was evaluated using the following microbial indicators: soil microbial biomass, respiration, nitrification, and Shannon index. Two soil types, udic ferrosols and aquic cambisols, were amended with 0 mg/kg, 1 mg/kg, 10 mg/kg, 100 mg/kg, 500 mg/kg, or 1000 mg/kg BaP; incubated at 25 °C; and tested on days 28, 60, and 180. The Shannon index was extremely insensitive to BaP. Microbial biomass and respiration could not be classified as sensitive indicators because of their relatively high 10% effect concentration (EC10) values. Nitrification was the most sensitive indicator in both soils and could be the preferred microbial indicator for testing the ecotoxicity of BaP. Higher toxicity of BaP was exhibited in udic ferrosols than in aquic cambisols, and the ecotoxicity of BaP decreased with incubation time. Extending the 28-d incubation time, which is suggested in the International Organization for Standardization and Organisation for Economic Co-operation and Development guidelines, to 60 d was recommended for future microbial toxicity tests of BaP. On day 28, the EC10 values for microbial biomass, respiration, and nitrification were 71 mg/kg, 43 mg/kg, and 3.4 mg/kg in aquic cambisols and 51 mg/kg, 22 mg/kg, and 1.3 mg/kg in udic ferrosols, respectively. On day 60, these values were 106 mg/kg, 59 mg/kg, and 19 mg/kg in aquic cambisols and 77 mg/kg, 40 mg/kg, and 6.9 mg/kg in udic ferrosols. These values could be used in combination to derive ecotoxicological soil screening levels of BaP. Environ Toxicol Chem 2014; 33:1930–1936. © 2014 SETAC

Soil-plant transfer models are needed to predict levels of mercury (Hg) in vegetables when evaluating food chain risks of Hg contamination in agricultural soils. A total of 21 soils covering a wide range of soil properties were spiked with HgCl2 to investigate the transfer characteristics of Hg from soil to carrot in a greenhouse experiment. The major controlling factors and prediction models were identified and developed using path analysis and stepwise multiple linear regression analysis. Carrot Hg concentration was positively correlated with soil total Hg concentration (R 2 = 0.54, P

At present, soil quality standards used for agriculture do not fully consider the influence of soil properties on cadmium (Cd) uptake by crops. This study aimed to develop prediction models for Cd transfer from a wide range of Chinese soils to carrot (Daucus carota L.) using soil properties and the total or available soil Cd content. Path analysis showed soil pH and organic carbon (OC) content were the two most significant properties exhibiting direct effects on Cd uptake factor (ratio of Cd concentration in carrot to that in soil). Stepwise multiple linear regression analysis also showed that total soil Cd, pH, and OC were significant variables contributing to carrot Cd concentration, explaining 90% of the variance across the 21 soils. Soil thresholds for carrot (cultivar New Kuroda) cropping based on added or total Cd were then derived from the food safety standard and were presented as continuous or scenario criteria.

The hilly red soil region of subtropical China is a major rice producing area, where over-exploitation and non-agricultural uses of paddy soils have decreased soil quality and rice productivity. Our objectives were to develop and evaluate a soil quality assessment protocol for Yujiang County in Jiangxi Province. A variety of soil samples, representing the spatial homogeneity in 114 paddy fields, were collected and analyzed for several chemical and physical properties. Pearson correlation analysis between rice yield and the various soil properties was used to identify potential soil quality indicators. Principal component analysis (PCA) was then used to group the indicators into appropriate soil quality factors. A minimum data set (MDS) including soil organic matter, available nitrogen, available phosphorus, slowly available potassium and sand content accounted for 77.9% of the quality variation among soils. A soil quality index (SQI) was calculated using the Integrated Quality Index (IQI) equation. Significant correlation between the SQI and rice yield indicated the index had high biological significance for Jiangxi province and other paddy areas with similar soils.

Excessive pig manure application probably degrades arable soil quality in some intensive pig farming areas. The responses of the nematode community to dosages of pig manure were investigated in Ferric Acrisols under 3-season peanut monoculture. Varying dosages of manure (1.75, 3.5, 7, 14 and 28 t·ha−1·yr−1) in combination with chemical fertilizer were applied to field plots, and chemical fertilizer alone was also applied as a control. With increasing manure application, the abundance of bacterivores and omnivores-predators increased, the abundance of plant parasites decreased, and fungivores abundance exhibited hump-shaped variation. Simpson diversity index and plant parasite index/maturity index of the nematode communities increased to a maximum level at a manure application rate of 3.5 t·ha−1·yr−1 and then sharply decreased. The changes in the soil nematode community were further determined to be correlated with chemical properties; available phosphorus had the strongest quadratic correlation with the two indices, implying that available phosphorus had a better indicative effect than other soil properties to nematode community. Available phosphorus in soil was deduced from 49 to 64 mg·kg−1 with the best nematode communities. Our results emphasized the importance of regular applications of manure in agriculture field to balance nematode diversity and build healthy agro-ecosystems.

The bulk deposition of both PAHs and metals is a significant, mounting issue for the urban ecological environment. However, studies generally performed on these pollutants have focused on the regions surrounding a pollution source; thus, it most likely overestimated pollutants in the cities. Therefore, 72 atmospheric bulk deposition samples were collected from six sites located along a transect from the suburbs to the city center in Shanghai over a 1-year period (February 1, 2012 to January 31, 2013). The seasonal variation, spatial distribution, and sources of multiple metals (Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Pb, K, Na, and Mg) and 16 polycyclic aromatic hydrocarbon (PAH) compounds were determined. The results indicated that the annual average rate of dust deposition in Shanghai was 43,100 ± 54,800 mg/m2/year. There were significant or high enrichments of Cu, Zn, Cd, and Pb, and higher depositional fluxes were observed for Zn, Pb, and Cd in the Huangpu district and for Cu in the Minhang district. The deposition fluxes of the PAHs exhibited the following order: urban fringe zone > city center > rural zone (background site). However, unlike in northern Chinese cities, the high-molecular-weight PAHs accounted for most of the PAHs. Furthermore, there were higher depositional fluxes of PAHs in March, July, and October. Overall, the factors influencing urban air quality may include construction, fossil fuel combustion, the abrasion of tires and brake linings (directly related to traffic), the corrosion of galvanized protection barriers, and increasing population density.

The role of ferrous iron in the phosphorus cycle of an aquatic ecosystem is poorly understood because of a lack of suitable methods to quantitatively evaluate ferrous iron phosphorus (FIP) phases. Using sediments sampled from Fubao Bay of Dianchi Lake in China, a novel extraction method for FIP using 2,2'-bipyridine was explored. Total phosphorus and iron in the sediments ranged from 1.0 to 5.0 mg/g (dry weight) and 28.5 to 90.6 mg/g, respectively. Organic content (as indicated by loss on ignition or LOI) and iron(II) ranged from 3.1 to 27.0% and 26.5 to 64.9 mg/g, respectively. The dissolution dynamics of FIP extraction with a low solid/liquid ratio (1: 25) indicated that a single application of 0.2% 2,2'-bipyridine extracted both iron(II) (Fe(II)) and phosphorus (as PO43-) in sediments with different organic contents with low efficiency. The extraction efficiency of Fe(II) was improved by alteration of the solid/liquid ratio, but the effect was limited. However, addition of a 1:1000 solid/liquid ratio of 0.5 M potassium chloride to a 0.2% 2,2'-bipyridine solution significantly accelerated extraction of FIP with the release of Fe(II) and phosphorus toward equilibrium at approximately 150 hours. Further investigation demonstrated that 2,2'-bipyridine exhibited a higher selectivity in distinguishing FIP from phosphorus bound to ferric (Fe(III)) oxides or precipitated by calcium (Ca2+). Air-drying sediments significantly decreased the amount of extracted FIP, which indicates that fresh, wet sediment should be used in this type of FIP extraction. Based on experimental results using the proposed extraction protocol, (1) FIP in sediments of Fubao Bay had a predominant status in the lake sediment and accounted for 23.4 to 39.8% of total phosphorus, and (2) Fe(II)(FIP) released in the extraction is directly proportional to phosphorus(FIP) (Fe(II)(FIP) = 2.84 x P-FIP + 0.0007; R-2 = 0.97) with an average molar ratio of Fe(II)(FIP)/P-FIP of 2.7. This study shows that FIP extraction with 2,2'-bipyridine is a robust method for releasing ferrous iron associated with phosphorus. Further, the high percentage of FIP in total phosphorus (40%) measured in the study site using this extraction method suggests that FIP might have been often underestimated in previous studies. Water Environ. Res., 84 2037 (2012).

To evaluate the external and internal morphological differences of roots that might influence rice root radial oxygen loss (ROL) and the corresponding rhizosphere nitrification activity, growth characteristics and nitrogen nutrition of rice. The root ROL and rhizosphere oxygen profile were determined using a miniaturised Clark-type oxygen microelectrode system, and the rhizosphere nitrification activity was studied with a short-term nitrification activity assay. The rice biomass, nitrogen accumulation and nitrogen use efficiency (NUE) of ZH (high yield) were significantly higher than those of HS (low yield). The root biomass, number, diameter and porosity of ZH were also much greater than those of HS. The inner and surface oxygen concentrations of the root of ZH were significantly higher than those of HS. The order of paddy soil oxygen penetration depth was ZH > HS > CK, and the order of the oxygen concentrations detected in the water layer and rhizosphere soil was the same. The rhizosphere nitrification activity and nitrate concentration of ZH were significantly higher than those of HS. More porous and thicker roots improved the individual root ROL, and more adventitious root numbers enhanced the entire plant ROL and correspondingly improved the rhizosphere nitrification activity, which might influence the growth and nitrogen nutrition of rice.

Manganese (Mn) uptake capacities of water hyacinth (Eichhornia crassipes (Mart.) Solms, water lettuce (Pistia stratiotes L.) and slligator alternenthera (Alternanthera philoxeroides) were investigated with four Mn levels: 0(control), 50, 200, 400 mg/L. With increased Mn exposure, the tested plants showed similar responses with a decrease in relative growth rate and an increase in plant Mn concentrations. Comparatively, water lettuce had the significantly higher total Mn concentrations, shoots enrichment factor and translocation factor at all Mn-treated treatments and the much greater total Mn removal at concentrations of 200 and 400 mg/L Mn. In most cases, Mn pollution significantly decreased Mg concentrations for all three plants. Concomitantly, increment trends of Fe, Cu and Zn concentrations were observed for water lettuce with the increasing external Mn concentrations, which could partly contribute to its higher Mn concentrations. The results indicated that water lettuce have standout potentials as a phytoremediation plant for Mn contaminated waters.

Oxidation–reduction properties of surface sediments are tightly associated with the geochemistry of substances, and reducing organic substances (ROS) from hydrophytes residues may play an important role in these processes. In this study, composition, dynamics, and properties of ROS from anaerobic decomposition of Eichhornia crassipes (Mart.) Solms, Potamogenton crispus Linn, Vallisneria natans (Lour.) Hara, Lemna trisulca Linn and Microcystis flos-aquae (Wittr) Kirch were investigated using differential pulse voltammetry (DPV). The type of hydrophytes determined both the reducibility and composition of ROS. At the peak time of ROS production, the anaerobic decomposition of M. flos-aquae produced 6 types of ROS, among which 3 belonged to strongly reducing organic substance (SROS), whereas there were only 3–4 types of ROS from the other hydrophytes, 2 of them exhibiting strong reducibility. The order of potential of hydrophytes to produce ROS was estimated to be: M. flos-aquae > E. crassipes > L. trisulca > P. crispus ≈ V. natans, based on the summation of SROS and weakly reducing organic substances (WROS). The dynamic pattern of SROS production was greatly different from WROS. The total SROS appeared periodic fluctuation with reducibility gradually weakening with incubation time, whereas the total WROS increased with incubation time. Reducibility of ROS from hydrophytes was readily affected by acid, base and ligands, suggesting that their properties were related to these aspects. In addition to the reducibility, we believe that more attention should be paid to the other behaviors of ROS in surface sediments.

Strongly reducing organic substances (SROS) and iron oxides exist widely in soils and sediments and have been implicated in many soil and sediment processes. In the present work, the sorptive interaction between goethite and SROS derived from anaerobic decomposition of green manures was investigated by differential pulse voltammetry (DPV). Both green manures, Astragaltus sinicus (Astragalus) and Vicia varia (Vicia) were chosen to be anaerobically decomposed by the mixed microorganisms isolated from paddy soils for 30 d to prepare different SROS. Goethite used in experiments was synthesized in laboratory. The anaerobic incubation solutions from green manures at different incubation time were arranged to react with goethite, in which SROS concentration and Fe(II) species were analyzed. The anaerobic decomposition of Astragalus generally produced SROS more in amount but weaker in reducibility than that of Vicia in the same incubation time. The available SROS from Astragalus that could interact with goethite was 0.69 +/- 0.04, 0.84 +/- 0.04 and 1.09 +/- 0.03 cmol kg(-1) as incubated for 10, 15 and 30 d, respectively, for Vicia, it was 0.12 +/- 0.03, 0.46 +/- 0.02 and 0.70 +/- 0.02 cmol kg(-1). One of the fates of SROS as they interacted with goethite was oxidation. The amounts of oxidizable SROS from Astragalus decreased over increasing incubation time from 0.51 +/- 0.05 cmol kg(-1) at day 10 to 0.39 +/- 0.04 cmol kg(-1) at day 30, but for Vicia, it increased with the highest reaching to 0.58 +/- 0.04 cmol kg(-1) at day 30. Another fate of these substances was sorption by goethite. The SROS from Astragalus were sorbed more readily than those from Vicia, and closely depended upon the incubation time, whereas for those from Vicia, the corresponding values were remarkably less and apparently unchangeable with incubation time. The extent of goethite dissolution induced by the anaerobic solution from Vicia was greater than that from Astragalus, showing its higher reactivity. (c) 2008 Published by Elsevier Ltd.

The effects of seven amendments on the distribution and accumulation of copper and cadmium in a soil–rice system were investigated using a pot experiment. Results showed that application of limestone, calcium magnesium phosphate (Ca–Mg–P fertilizer), calcium silicate (silicon fertilizer), Chinese milk vetch, pig manure, and peat significantly decreased the concentrations of Cu and Cd in rice roots by 24.8–75.3% and 9.7–49.9%, respectively. However, no significant difference was observed between zinc sulfate (zinc fertilizer) and the control treatment. The concentrations of Cu and Cd in different parts of rice followed the order: root > straw > grain, and all amendments restrained the transfer of Cu and Cd from rice root to stem. Copper and Cd concentrations in rice stems at the tillering stage were the highest, and then decreased from the tillering stage to the heading stage. However, they increased again at the ripening stage. The results also showed that application of amendments changed Cu and Cd solubility in soil and decreased their bioavailability, which resulted in the reduction of Cu and Cd uptake by rice. Significant correlations between the concentrations of Cu and Cd in soil solutions and in rice stems were found. The result demonstrated that limestone has the best efficiency among all the amendments used in reducing Cu and Cd contamination to rice production.