Unraveling how Fe-Mn modified biochar mitigates sulfamonomethoxine in soil water: The activated biodegradation and hydroxyl radicals formation.

This study indicated that the application of a novel Fe-Mn modified rice straw biochar (Fe/Mn-RS) as soil amendment facilitated the removal of sulfamonomethoxine (SMM) in soil water microcosms, primarily via activating degradation mechanism rather than adsorption. The similar enhancement on SMM removal did not occur using rice straw biochar (RS). Comparison of Fe/Mn-RS with RS showed that Fe/Mn-RS gains new physic-chemical properties such as abundant oxygenated C-centered persistent free radicals (PFRs). In the Fe/Mn-RS microcosms, the degradation contributed 79.5-83.8% of the total SMM removal, which was 1.28-1.70 times higher than that in the RS microcosms. Incubation experiments using sterilized and non-sterilized microcosms further revealed that Fe/Mn-RS triggered both the biodegradation and abiotic degradation of SMM. For abiotic degradation of SMM, the abundant •OH generation, induced by Fe/Mn-RS, was demonstrated to be the major contributor, according to EPR spectroscopy and free radical quenching experiments. Fenton-like bio-reaction occurred in this process where Fe (Ⅲ), Mn (Ⅲ) and Mn (Ⅳ) gained electrons, resulting in oxidative hydroxylation of SMM. This work provides new insights into the impacts of biochar on the fates of antibiotics in soil water and a potential solution for preventing antibiotic residues in agricultural soil becoming a non-point source pollutant.

A novel Fe-PTFE magnetic composite prepared by ball milling for the efficient degradation of imidacloprid: Insights into interaction mechanisms based on ultrasonic piezoelectric catalysis.

In this study, a novel magnetic poly (tetrafluoroethylene, PTFE) (Fe@PTFE) piezoelectric catalytic material was successfully prepared by a simple ball milling treatment. The prepared piezoelectric catalytic material Fe@PTFE exhibited excellent catalytic performance under the activation of ultrasonic (US) and realized the efficient degradation of imidacloprid (IMI) at low concentrations in an aqueous environment. It was demonstrated by various characterization methods that Fe0 was successfully loaded onto PTFE particles (1-15 µm) by ball milling. The US/Fe@PTFE system exhibited superior IMI degradation efficiency (99 %) and degradation rate (7.81× 10-2 min-1) under ultrasonic polarization with high efficiences of IMI degradation after five cycles. In addition, the system maintained excellent removal efficiencies in the real water matrixes. The mechanism study demonstrated that Fe@PTFE generated a variety of reactive oxygen species (•OH, 1O2 and O2•-) and H2O2 under the irradiation of US, and the production of H2O2 provided the conditions for the continuation of the Fenton-like reaction. Furthermore, the presence of O2•- in the system enhanced the recycling efficiency of Fe(III) and Fe(II), which further enhanced the degradation efficiency of the Fenton-like process. This study provides a novel perspective on a PTFE-based ultrasonic piezoelectric catalytic system for the efficient removal of organic pollutants in the environmental field.

Ball milling-assisted preparation of sludge biochar as a novel periodate activator for nonradical degradation of sulfamethoxazole: Insight into the mechanism of enhanced electron transfer.

The non-radical pathway of periodate (PI) activation for the removal of persistent organic contaminants has received increasing attention due to its higher stability and oxidative advantages. In this study, the degradation of sulfamethoxazole (SMX) by ball mill treated magnetic sludge biochar (BM-MSBC) through activation of PI by electron transfer mechanism was reported. Experimental and characterization results showed that the ball milling treatment resulted in a better pore and defect structure, which also significantly enhanced the electron transfer capacity of the sludge biochar. The BM-MSBC/PI system exhibited notable dependence of activator concentration and initial pH, while the effect of PI concentration was not significant. The coexisting substances (common anions and natural organic matters) hardly affect the degradation of SMX in the BM-MSBC/PI system. The phytotoxicity experiments suggested that the treatment of BM-MSBC/PI system could significantly reduce the biological toxicity of SMX solution. This study provides a novel, economical, and facile modification method for the application of sludge biochar in advanced oxidation processes.

[Effects of biochar combined with nitrification/urease inhibitors on soil active nitrogen emissions from subtropical paddy soils]. / ç”Ÿç‰©ç‚­é æ–½ç¡åŒ–/è„²é ¶æŠ‘åˆ¶å‰‚å¯¹äºšçƒ­å¸¦æ°´ç¨»åœŸæ´»æ€§æ°®æ°”ä½“æŽ’æ”¾çš„å½±å“.

We examined the effects of biochar and urease inhibitors/nitrification inhibitors on nitrification process, ammonia and N2O emission in subtropical soil, and determined the best combination of biochar with nitrification and urease inhibitors. This work could provide a theoretical basis for the mitigation of the negative environmental risk caused by reactive nitrogen gas in the application of nitrogen fertilizer. A indoor aerobic culture test was conducted with seven treatments [urea+biochar (NB), urea+nitrification inhibitor (N+NI), urea+urease inhibitor (N+UI), urea+nitrification inhibitor+urease inhibitor (N+NIUI), urea+nitrification inhibitor+biochar (NB+NI), urea+urease inhibitor+biochar (NB+UI), urea+nitrification inhibitor+urease inhibitor+biochar (NB+NIUI)] and urea (N) as the control. The dynamics of soil inorganic nitrogen content, N2O emission and the volatility of ammonia volatilization were observed under combined application of biochar with urease inhibitor (NBPT)/nitrification inhibitor (DMPP). The results showed that:1)Compared to the control (5.11 mg N·kg-1·d-1) during the incubation period, NB treatment significantly increased therate constant of nitrification by 33.9%, and N+NI treatment significantly reduced the nitrification rate constant by 22.9%. NB treatment significantly increased the abundance of ammonia oxidizing bacteria (AOB) by 56.0%. 2) Compared with N treatment, N+NI and NB+NI treatments signi-ficantly enhanced the cumulative emission of NH3 by 49%. The N+UI treatment reduced the cumulative loss of NH3. The inhibition effect of NB+UI treatment was more significant. 3) The emission rate of N2O was highest in the first 10 days after fertilization. The N2O emission under NB treatment was the earliest, and that of N treatment was the highest (5.87 µg·kg-1·h-1). The combined application of DMPP and NBPT performed the best in reducing soil N2O emission. We estimated global warming potential (GWP) of the direct N2O and indirect N2O (NH3) emissions. Compared with N treatments, N+NI and NB+NI treatments increased the GWP by 34.8% and 40.9%, respectively. While the NB and NB+UI treatments significantly reduced the GWP by 45.9% and 60.5%, the combination of biochar and urease inhibitor had the best effect on reduction of GWP of soil active nitrogen emissions.

Clay-hydrochar composites return to cadmium contaminated paddy soil: Reduced Cd accumulation in rice seed and affected soil microbiome.

Excess cadmium (Cd) in rice precipitated by Cd contamination in paddy soils is a global human health threat and rational response is urgently needed. In this study, attapulgite-modified hydrochar (CA) and the montmorillonite-modified hydrochar (CM) were utilized in Cd-contaminated paddy soils at 0.5% (w/w) and 1% (w/w) application rates to investigate the effects of these clay-hydrochar composites on rice growth and soil Cd availability. The results show that the utility of CA and CM resulted in a significant increase in rice yield, especially at 1% application rate, which extended rice yield by 46.7-50.0% compared to 0.5% application rate. This is related to the Cd fixation and nutrient sequestration of the acidic functional groups on the surface of CA and CM. Additionally, CA-1% and CM-1% reduced the Cd concentration in rice seeds by 26.9-28.1% relative to the control. Notably, CA-1% showed the capacity to passivate Cd at the early stage of rice transplanting, lowering the proportion of Cd in the ion exchange state by 41.6% compared to the control, and this passivation effect persisted until the late stage of transplanted rice. The soil microbial community consequences showed that CA and CM did not significantly change the horizontal composition of the soil bacterial phylum and species diversity, indicating that CA and CM had excessive soil microbial adaptability. Moreover, results of correlation and Canonical Correspondence Analysis confirm that microbial genera responded significantly to the soil Cd morphologies, revealing the importance of CA and CM in the remediation of Cd-contaminated soils by influencing microorganisms. Our findings provide clay-hydrochar composites as a low-cost approach to effectively mitigate soil Cd contamination and improve the security and quality of rice.

Novel maricultural-solid-waste derived biochar for removing eutrophic nutrients and enrofloxacin: Property, mechanism, and application assessment.

Land-based seawater aquaculture accompanied by high stocking density usually involves producing excess eutrophic nutrients, residual baits, excrement, and antibiotics. Because of limited technology and salinity, proper and efficient treatment of these wastes is still an unsolved issue. In this study, the feasibility of maricultural fish residual bait and excrement-derived biochar as water pollutant remover and saline-alkaline soil amendment were firstly assessed. The biochar was pyrolyzed at 300, 500, 700, 800, 900 â„ƒ (marked as BC300, BC500, BC700, BC800, BC900) and modified by zirconium or iron (BC700-Zr or BC700-Fe). BC700-Zr had the highest specific surface area. BC700-Zr and BC700-Fe exhibited higher nitrogen removal efficiency. The biochars exhibited nitrogen and phosphate desorption, while we observed no obvious phosphate desorption in BC700-Zr or BC700-Fe. Adsorption kinetics analysis indicated that adsorption processes of nitrate, nitrite and enrofloxacin were consistent with pseudo-second-order model, while ammonium and phosphate adsorption processes fitted pseudo-first-order model better. The biochar showed nitrogen and phosphate nutrients release effects, indicating potential application in saline-alkaline soil improvement. Multi-linear regression analysis indicated that nitrogen release was closely related to biochar nitrogen content, pH and average pore width. Phosphate release was inversely related to pH and positively related to average pore width.

Biochar mitigated more N-related global warming potential in rice season than that in wheat season: An investigation from ten-year biochar-amended rice-wheat cropping system of China.

Rice-wheat cropping system (RWCS), the major rice-based cropping system, constitutes a significant source of N-related greenhouse gas (GHG) emission due to the unique wet-dry alternation process. Biochar is often highlighted as a potential solution for reducing fertilizer N losses, hence, understanding its effects on Ngr emissions (mainly NH3 and N2O) under wet-dry conditions is critical to inform strategies for GHG mitigation. This study investigated the responses of NH3 and N2O emissions to biochar amendments during rice and wheat seasons based on in situ measurements under ten-year successive straw biochar application in RWCS. Our results indicated that 43.7% and 89.9% of N2O and NH3 emissions were emitted during rice season and 56.3% and 10.1% during wheat season, respectively. Long-term biochar amendment was found to play significant role in mitigating NH3 emissions (38.6-43.9%), which could be attributed to the disappearance of liming effect of aged-biochar on flooding water and decreased NH4+ concentrations in the soil. However, considerable variation of N2O emissions were observed in RWCS. Biochar showed a significant decreasing effect on the net global warming potential related to N2O and NH3 emissions (GWPN) in rice season (16.1-89.6%), and slight increased tendency in wheat season (1.43-13.1%) primarily due to its positive effects on N2O emission. Biochar amendment mainly BC22.5, significantly increased above-ground yields by 9.22% in rice season. Thus, it is a low carbon-producing and sustainable crop management method that can support crop production, C sequestration, and GHG mitigation in rice season under RWCS from the viewpoint of the Ngr mitigation. Our results suggest that emission patterns of N2O and NH3 varied with wet-dry alternation under the disturbance of long-term biochar amendment in RWCS; moreover, long-term biochar application exhibited significant potential for mitigating soil Ngr losses in rice season for RWCS.

Adsorption of Cr(VI) from aqueous solutions using novel activated carbon spheres derived from glucose and sodium dodecylbenzene sulfonate.

Cr(VI) is a common wastewater pollutant. Various adsorbents including carbon-based materials are used for the removal of Cr(VI) owing to their high adsorption capacity. Chemical activation is an effective method to increase the specific surface area of adsorbents and, thus, further improve their adsorption capacity. However, research on the adsorption and removal of Cr(VI) from aqueous solutions by chemically activated carbon spheres is limited. Here, glucose and sodium dodecylbenzene sulfonate were used to produce carbon spheres (CSs) via hydrothermal synthesis. Activated carbon spheres (ACSs) were then derived using KOH. The adsorption of Cr(VI) in solution by CS and ACS was investigated through batch experiments. The results indicate that the specific surface area of the ACS was 1491.21 m2 g-1, which was much higher than that of the CS. The adsorption kinetics of the sorbent was consistent with the pseudo-second-order kinetic model and the adsorption isotherm followed the Langmuir model. This indicated that the adsorption process of the ACS with respect to Cr(VI) was mainly via single molecular layer adsorption and chemisorption. In a 200 mg L-1 Cr(VI) solution, the maximum amount of Cr(VI) adsorbed by the ACS was 230.15 mg g-1, and some of these adsorbed Cr(VI) were reduced to Cr(III). These results show that ACSs have strong potential for application in the removal of Cr(VI) from aqueous solutions.

[Effects of biochar on ammonia volatilization from farmland soil: A review.] / ç”Ÿç‰©ç‚­å¯¹å†œç”°åœŸå£¤æ°¨æŒ¥å‘çš„å½±å“æœºåˆ¶ç ”ç©¶è¿›å±•.

Reducing soil ammonia volatilization is one of the key ways to reduce soil nitrogen loss and improve nitrogen utilization efficiency in farmlands. Biochar has unique physico-chemical pro-perties, which can change soil physical and chemical properties, affect soil nitrogen cycle, and affect ammonia volatilization in farmland soil. Firstly, we reviewed the ammonia volatilization process and its influencing factors (climatic condition, soil environment, and fertilization management, etc.) in paddy fields and upland fields. Then, research progress on the impacts of biochar on ammonia volatilization from farmland ecosystem was reviewed. Furthermore, the mechanisms underlying the responses of ammonia volatilization to biochar intervention were discussed from the aspects of physical adsorption, gas-liquid equilibrium, and biochemical progress regulation. The reduction of soil ammonia volatilization is mainly based on the adsorption of soil NH4+ and NH3 by oxygen-containing functional groups on the surface of biochar and the promotion of soil nitrification. How-ever, the increases of soil ammonia volatilization are mainly related to the increases of soil pH, air permeability, activities of microorganisms related with soil organic nitrogen mineralization. Finally, the research direction of reducing soil ammonia volatilization and improving nitrogen utilization efficiency by biochar was prospected.

Impact of biochar amendment in agricultural soils on the sorption, desorption, and degradation of pesticides: A review.

Extensive and inefficient use of pesticides over the last several decades resulted in serious soil and water contamination by imposing severe toxic effects on living organisms. Soil remediation using environment-friendly amendments to counteract the presence of pesticides in soil seems to be one suitable approach to solve this problem. Biochar has emerged as a promising material for adsorbing and thus decreasing the bioavailability of pesticides in polluted soils, due to its high porosity, surface area, pH, abundant functional groups, and highly aromatic structure, mainly depending on the feedstock and pyrolysis temperature. However, biochar effects and mechanisms on the sorption and desorption of pesticides in the soil are poorly understood. Either high or low pyrolysis temperature has both positive and negative effects on sorption of pesticides in soil, one by larger surface area and the other by a large number of functional groups. Therefore, a clear understanding of these effects and mechanisms are necessary to engineer biochar production with desirable properties. This review critically evaluates the role of biochar in sorption, desorption, and degradation of pesticides in the soil, along with dominant properties of biochar including porosity and surface area, pH, surface functional groups, carbon content and aromatic structure, and mineralogical composition. Moreover, an insight into future research directions has been provided by evaluating the bioavailability of pesticide residues in the soil, effect of other contaminants on pesticide removal by biochar in soils, effect of pesticide properties on its behavior in biochar-amended soils, combined effect of biochar and soil microorganisms on pesticide degradation, and large-scale application of biochar in agricultural soils for multifunction.

Redox Structures of Humic Acids Derived From Different Sediments and Their Effects on Microbial Reduction Reactions.

Herein, we investigated the chemical, electrochemical, and spectroscopic characteristics of humic acids (HAs) extracted from sediments of different origin [Ling Qiao river, Xi Xi wetland, Qi Zhen lake (QZ), and Hu Zhou pond in Zhejiang province, China], paying particular attention to their role in the enhancement of nitrate and FeOOH reduction. Notably, the highest C/N ratio (16.16), O/C ratio (1.89), and Fe content (11.57 g kg-1 sample) were observed for HAs extracted from QZ sediment. Cyclic voltammetry analyses confirmed that all HAs contained redox-active groups and exhibited redox potentials between -0.36 and -0.28 V vs. the standard hydrogen electrode. All HAs showed similar Fourier transform infrared spectra with variable absorption intensity, the spectra verified the presence of aromatic C=C, C-H, and C=O of quinone ketones group in HAs. Electron spin resonance suggested that quinone moieties within HAs are the redox-active centers. All HAs promoted the microbial reduction of nitrate and amorphous FeOOH by Shewanella oneidensis strain MR-1, achieving high nitrate reduction extents of 79-98.4%, compared to the biotic and abiotic control values of 29.6 and 0.006%, respectively. The corresponding extents of Fe(II) production equaled 43.25-60.5%, exceeding those of biotic and abiotic controls (28.5 and 0.005%, respectively). In addition to the highest C/N, O/C ratio, and Fe content, HA extracted from QZ sediment also exhibited the highest nitrate and FeOOH reduction performances. Although the proportion of organic redox-active carbon is small, the potential electron-mediating ability is not ignorable. HAs are redox active for enhancing microbial reduction of nitrate and amorphous FeOOH regardless of the location or texture of parent sediments, implying their great potential for acting as redox mediator in enhancing multiple microbial reduction, thereby affecting various biogeochemical processes (i.e., iron cycle, nitrogen cycle, etc.) as well as in situ remediation in anaerobic environment.

Sulfur-modified rice husk biochar: A green method for the remediation of mercury contaminated soil.

Mercury (Hg) contamination of surface soils has increased by ~86Giga grams due to anthropogenic activities. There is an urgent need to find new, effective and preferably 'green' remediation technologies to protect human health and the environment. Sulfur-modification of sorbents can greatly enhance Hg sorption capacity - by forming low solubility HgS (cinnabar). However, S-modified sorbents are not considered suitable for soil remediation due to the economic cost and secondary environmental impacts of sorbents such as granulated activated carbon (GAC), and the toxicity of S-modifiers such as thiol compounds. It was previously found that if biochar is used as an alternative to GAC then the overall environmental impact can be significantly reduced. However, due to a lack of experimental evidence, the practicality of S-modified biochar remains uncertain. The present study was undertaken to provide a proof-of-concept for the 'green' remediation of Hg contaminated soils with rice husk biochar modified with non-toxic elemental S. It was found that the S modification process increased the biochar S content from 0.2% to 13.04% via surface deposition or volume pore filling. This increased the biochar's Hg2+ adsorptive capacity (Qmax) by ~73%, to 67.11mg/g. To assess the performance of S-modified rice husk biochar for soil remediation it was applied to a high 1000mg/kg Hg2+ contaminated soil. Treatment dosages of 1%, 2% and 5% (dry wt.) were found to reduce freely available Hg in TCLP (toxicity characterization leaching procedure) leachates by 95.4%, 97.4% and 99.3%, respectively, compared to untreated soil. In comparison, unmodified rice husk biochar reduced Hg concentrations by 94.9%, 94.9% and 95.2% when applied at the same treatment dosage rates, respectively. This study has revealed that S-modified rice husk biochar has potential to stabilize Hg as a 'green' method for the remediation of contaminated soils.

Simultaneous removal of Sb(iii) and Cd(ii) in water by adsorption onto a MnFe2O4-biochar nanocomposite.

In this study, a jacobsite-biochar nanocomposite (MnFe2O4-BC) was fabricated and used to simultaneously remove Sb(iii) and Cd(ii) from water via adsorption. The MnFe2O4-BC nanocomposite was prepared via a co-precipitation method and analyzed using various techniques. The results confirm the successful decoration of the biochar surface with MnFe2O4 nanoparticles. The maximum Sb(iii) removal efficiency was found to be higher from bi-solute solutions containing Cd(ii) than from single-solute systems, suggesting that the presence of Cd(ii) enhances the removal of Sb(iii). The Langmuir isotherm model describes well Sb(iii) and Cd(ii) removal via adsorption onto the MnFe2O4-BC nanocomposite. The maximum adsorption capacities are 237.53 and 181.49 mg g-1 for Sb(iii) and Cd(ii), respectively, in a bi-solute system. Thus, the prepared MnFe2O4-BC nanocomposite is demonstrated to be a potential adsorbent for simultaneously removing Sb(iii) and Cd(ii) ions from aqueous solutions.

Bio- and hydrochars from rice straw and pig manure: Inter-comparison.

Conversion of rice straw (RS) and pig manure (PM) into chars is a promising disposal/recycling option. Herein, pyrolysis and hydrothermal carbonization were used to produce bio- and hydrochars from RS and PM, affording lower biochar (300-700°C) and hydrochar (180-300°C) yields at higher temperatures within the specified range. The C contents and C/N ratios of RS chars were higher than those of PM ones, with the opposite trend observed for yield and ash content. C and ash contents increased with increasing temperature, whereas H/C, O/C, and (O+N)/C ratios decreased. The lower H/C ratio of biochars compared to that of hydrochars indicated greater stability of the former. KCl was the main inorganic fraction in RS biochars, whereas quartz was dominant in PM biochars, and albite in PM hydrochars. Thus, RS is more suitable for carbon sequestration, while PM is more suitable for use as a soil amendment substrate.

Revealing the characteristics of a novel bioflocculant and its flocculation performance in Microcystis aeruginosa removal.

In the present work, a novel bioflocculant, EPS-1, was prepared and used to flocculate the kaolin suspension and Microcystis aeruginosa. We focused on the characteristics and flocculation performance of EPS-1, especially with regard to its protein components. An important attribute of EPS-1 was its protein content, with 18 protein types identified that occupied a total content of 31.70% in the EPS-1. Moreover, the flocculating activity of these protein components was estimated to be no less than 33.93%. Additionally, polysaccharides that occupied 57.12% of the total EPS-1 content consisted of four monosaccharides: maltose, D-xylose, mannose, and D-fructose. In addition, carbonyl, amino, and hydroxyl groups were identified as the main functional groups. Three main elements, namely C1s, N1s, and O1s, were present in EPS-1 with relative atomic percentages of 62.63%, 24.91%, and 10.5%, respectively. Zeta potential analysis indicated that charge neutralization contributed to kaolin flocculation, but was not involved in M. aeruginosa flocculation. The flocculation conditions of EPS-1 were optimized, and the maximum flocculating efficiencies were 93.34% within 2 min for kaolin suspension and 87.98% within 10 min for M. aeruginosa. These results suggest that EPS-1 could be an alternative to chemical flocculants for treating wastewaters and cyanobacterium-polluted freshwater.

Effects of water management practices on residue decomposition and degradation of Cry1Ac protein from crop-wild Bt rice hybrids and parental lines during winter fallow season.

Rice is the staple diet of over half of the world's population and Bacillus thuringiensis (Bt) rice expressing insecticidal Cry proteins is ready for deployment. An assessment of the potential impact of Bt rice on the soil ecosystem under varied field management practices is urgently required. We used litter bags to assess the residue (leaves, stems and roots) decomposition dynamics of two transgenic rice lines (Kefeng6 and Kefeng8) containing stacked genes from Bt and sck (a modified CpTI gene encoding a cowpea trypsin inhibitor) (Bt/CpTI), a non-transgenic rice near-isoline (Minghui86), wild rice (Oryza rufipogon) and crop-wild Bt rice hybrid under contrasting conditions (drainage or continuous flooding) in the field. No significant difference was detected in the remaining mass, total C and total N among cultivars under aerobic conditions, whereas significant differences in the remaining mass and total C were detected between Kefeng6 and Kefeng8 and Minghui86 under the flooded condition. A higher decomposition rate constant (km) was measured under the flooded condition compared with the aerobic condition for leaf residues, whereas the reverse was observed for root residues. The enzyme-linked immunosorbent assay (ELISA), which was used to monitor the changes in the Cry1Ac protein in Bt rice residues, indicated that (1) the degradation of the Cry1Ac protein under both conditions best fit first-order kinetics, and the predicted DT50 (50% degradation time) of the Cry1Ac protein ranged from 3.6 to 32.5 days; (2) the Cry1Ac protein in the residue degraded relatively faster under aerobic conditions; and (3) by the end of the study (~154 days), the protein was present at a low concentration in the remaining residues under both conditions. The degradation rate constant was negatively correlated with the initial carbon content and positively correlated with the initial Cry1Ac protein concentration, but it was only correlated with the mass decomposition rate constants under the flooded condition. No Cry1Ac protein was detected in the soils surrounding the buried residue. Our results did not reveal any evidence that the stacked genes (Bt/CpTI) or the presence of the Cry1Ac protein influenced the decomposition dynamics of the rice residues. Furthermore, our results suggested that field drainage after residue incorporation would promote Cry1Ac protein degradation.

[Effects of biochar on soil nutrients leaching and potential mechanisms: A review].

Controlling soil nutrient leaching in farmland ecosystems has been a hotspot in the research field of agricultural environment. Biochar has its unique physical and chemical properties, playing a significant role in enhancing soil carbon storage, improving soil quality and increasing crop yield. As a kind of new exogenous material, biochar has the potential in impacting soil nutrient cycling directly or indirectly, and has profound influences on soil nutrient leaching. This paper analyzed the intrinsic factors affecting how biochar affects soil nutrient leaching, such as the physical and chemical properties of biochar, and the interaction between biochar and soil organisms. Then the latest literatures regarding the external factors, including biochar application rates, soil types, depth of soil layer, fertilization conditions and temporal dynamics, through which biochar influences soil nutrient (especially nitrogen and phosphorus) leaching were reviewed. On that basis, four related action mechanisms were clarified, including direct adsorption of nutrients by biochar due to its micropore structure or surface charge, influencing nutrient leaching through increasing soil water- holding capacity, influencing nutrient cycling through the interaction with soil microbes, and preferential transport of absorbed nutrients by fine biochar particles. At last future research directions for better understanding the interactions between biochar and nutrient leaching in the soil were proposed.

[Effects of biochar application on greenhouse gas emission from paddy soil and its physical and chemical properties].

A field experiment was conducted to investigate the effects of rice straw returning and rice straw biochar and life rubbish biochar application on the greenhouse gas (CH4, CO2 and N2O) emission from paddy soil, its physical and chemical properties, and rice grain yield. Compared with rice straw returning, applying rice straw biochar decreased the cumulative CH4 and N2O emissions from paddy soil significantly by 64.2% - 78.5% and 16.3% - 18.4%, respectively. Whether planting rice or not, the cumulative N2O emission from paddy soil under the applications of rice straw biochar and life rubbish biochar was decreased significantly, compared with that without biochar amendment. Under the condition of no rice planting, applying life rubbish biochar reduced the cumulative CO2 emission significantly by 25.3%. Rice straw biochar was superior to life rubbish biochar in improving soil pH and available potassium content. Both rice straw biochar and life rubbish biochar could increase the soil organic carbon content significantly, but had less effects on the soil bulk density, total nitrogen and available phosphorus contents, cation exchange capacity (CEC), and grain yield. It was suggested that compared with rice straw returning, straw biochar was more effective in improving rice grain yield.