[Effects of Long-term Biochar Addition on Denitrification N2O Emissions from Bacteria and Fungi in Paddy Soil].

Denitrification driven by bacteria and fungi is the main source of nitrous oxide （N2O） emissions from paddy soil. It is generally believed that biochar reduces N2O emissions by influencing the bacterial denitrification process, but the relevant mechanism of its impact on fungal denitrification is still unclear. In this study, the long-term straw carbonization returning experimental field in Changshu Agricultural Ecological Experimental Base of the Chinese Academy of Sciences was taken as the object. Through indoor anaerobic culture and molecular biology technology, the relative contributions of bacteria and fungi to denitrifying N2O production in paddy soil and the related microorganism mechanism were studied under different long-term biochar application amounts （blank, 2.25 t·hm-2, and 22.5 t·hm-2, respectively, expressed by BC0, BC1, and BC10）. The results showed that compared with that in BC0, biochar treatment significantly reduced N2O emission rate, denitrification potential, and cumulative N2O emissions, and the contribution of bacterial denitrification was greater than that of fungal denitrification in all three treatments. Among them, the relative contribution rate of bacterial denitrification in BC10 （62.9%） was significantly increased compared to BC0 （50.8%）, whereas the relative contribution rate of fungal denitrification in BC10 （37.1%） was significantly lower than that in BC0 （49.2%）. The application of biochar significantly increased the abundance of bacterial denitrification functional genes （nirK, nirS, and nosZ） but reduced the abundance of fungal nirK genes. The contribution rate of fungal denitrification was significantly positively correlated with the N2O emission rate and negatively correlated with soil pH, TN, SOM, and DOC. Biochar may have inhibited the growth of denitrifying fungi by increasing pH and carbon and nitrogen content, reducing the abundance of related functional genes, thereby weakening the reduction ability of NO to N2O during fungal denitrification process. This significantly reduces the contribution rate of N2O production during the fungal denitrification process and the denitrification N2O emissions from paddy soil. This study helps to broaden our understanding of the denitrification process in paddy soil and provides a theoretical basis for further regulating fungal denitrification N2O emissions.

[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.

[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.

Improved lead removal from aqueous solution using novel porous bentonite - and calcite-biochar composite.

Biochar-mineral (bentonite/calcite) composite (BC-CM) prepared at different temperatures were tested under varied conditions for effective removal of lead (Pb) from aqueous solution. With increasing pyrolysis temperature, increased surface area, pore volume, bentonite decomposition and less or no decomposition of calcite occurred. Bentonite-biochar (BCS) and calcite-biochar (CCS) prepared at 700 °C were found most suitable for efficient removal of Pb (99.9%). Bentonite and calcite acted as catalyst and contributed to changes in yield, pH, texture, functional groups, minerals and carbonization that facilitated efficient Pb removal by BCS 700 and CCS 700. Pb concentration, pH, dose of BCS and CCS, and contact time were further optimized using response surface methodology (RSM) for maximizing removal percentage (R%) of Pb and adsorption capacity (qt). Both BCS 700 and CCS 700 showed similar effects (positive/negative) of factors on R% and qt. Under optimized conditions, 0.21 g of BCS 700 effectively removed 99.2% of 431 mg/L in 3.6 h at solution pH of 4.2, while 0.07 g CCS 700 removed 97.06% of 232 mg/L in 3.5 h at 5.5 pH. Removal of Pb onto both BCS and CCS was by monolayer adsorption with maximum adsorption capacity of 500 mg/g. Rapid Pb removal was observed within 2 h of contact time (CCS 700 > BCS 700) and equilibrium was achieved within 10 h. BCS 700 followed first order and CCS 700 followed second order kinetic model. Electrostatic attraction between Pb ions and mineral groups present in BCS 700 and CCS 700 also played important role in Pb removal. This study clearly demonstrated that composite of biochar with bentonite or calcite under optimized conditions significantly improved Pb removal and adsorption capacity that can be further utilized for larger scale applications.

[Effects of biochar addition on enzyme activity and fertility in paddy soil after six years]. / 施用生物炭6å¹´åŽå¯¹ç¨»ç”°åœŸå£¤é ¶æ´»æ€§åŠè‚¥åŠ›çš„å½±å“.

A field experiment was conducted to examine the effects on soil fertility and enzyme activities in paddy field after six years of one-split rice straw-derived biochar [0 (BC0), 7.5(BC1), 15(BC2), 22.5(BC3) t·hm-2] and rice straw (3.75 t·hm-2, STR) application. The results showed that soil organic carbon, available phosphorus and rapidly available potassium concentrations significantly increased, by 34.6%, 12.4% and 26.2%, respectively. Soil pH and soil bulk density were significantly reduced, but total nitrogen content had no significant difference compared with BC0. Biochar addition significantly increased the activities of soil urease and acid phosphatase. The soil fluorescein diacetate (FDA hydrolase) and arylsulfatase activity were inhibited to varying degrees. Among them, BC2 treatment increased soil urease activity by 36.5%. The soil acid phosphatase activity increased with the increases of biochar application rate, which was positively correlated with soil available phosphorus concentration. FDA hydrolase and urease activity had positive correlation with soil available potassium content, while soil acid phosphatase and arylsulfatase activity had positive correlation with soil bulk density. After six years, soil dehydrogenase and polyphenol oxidase activity significantly increased by 48.8% and 27.5%, respectively, while catalase activity significantly decreased when compared with control BC0. STR treatment increased activities of soil urease, FDA hydrolase, dehydrogenase, acid phosphatase and arylsulfatase significantly, while decreased the catalase and polyphenol oxidase activities by 23.4% and 15.9%, respectively.

[Stability of biochar and the mechanisms underlying its response to mineral modification: A review.] / ç”Ÿç‰©ç‚­çš„ç¨³å®šæ€§åŠå ¶å¯¹çŸ¿ç‰©æ”¹æ€§çš„å“åº”æœºåˆ¶ç ”ç©¶è¿›å±•.

Biochar, with high degree of carbon stability, is considered as a kind of carbon sequestration material that can effectively alleviate the greenhouse effect. It is of great significance for carbon sequestration and mitigation to develop biochar with high carbon retention and stability. Mineral modification can regulate the stability of biochar. However, the relevant research has not received enough attention, and the underlying mechanism is not very clear. Firstly, the evaluation indices of biochar stability were summarized, mainly including H/C atomic ratio, O/C atomic ratio, coefficient of stability R50, volatile-matter content, thermal weight loss rate of carbon, carbon (chemical) oxidation loss rate, and cumulative CO2 emission of microbial mineralization. Then, based on the analysis of impact factors of biochar stability (such as raw material type, carbonization condition, external environment, etc.), we reviewed research progress about the effects of mineral modification on biochar stability. Furthermore, possible mechanisms of both enhancement and weakening effects on biochar stability were put forward. Enhancement is mainly due to the effects of physical barrier of minerals and the organic mineral complex formed by the interaction of mineral and biochar. While weakening effect is mainly due to special mineral composition, such as the Fe-bearing mineral composition, which promotes the thermal decomposition of biochar at high temperature. Finally, future research directions were proposed, in order to promote the development of carbon sequestration technology of biochar and provide technical support and theoretical basis for obtaining more stable biochar.

[Cadmium adsorption by biochar prepared from pyrolysis of silk waste at different temperatures]. / 不同炭化温度制备的蚕丝被废弃物生物炭对重金属Cd2+的吸附性能.

In this study, biochars (BC300, BC500 and BC700) were produced from silk waste through pyrolysis under oxygen-limited condition at 300, 500 and 700 ℃, respectively. The physicochemical properties of biochar were detected by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and specific surface area analyzer. The Cd2+ adsorption capacities of biochars were investigated. Results showed that BET surface area, pH, and ash were increased with the increases of pyrolysis temperature. SEM images showed that the surfaces of biochars were rough and irregular. XRD and FT-IR results showed that all the silk waste biochars obtained at different temperatures contained calcite. pH had limited influence on the removal efficiency of biochar for Cd2+. Langmuir isotherm fitted the experimental data quite well. The Langmuir monolayer adsorption capacity of BC300, BC500, and BC700 were 25.61, 52.41, and 91.07 mg·g-1, respectively. The adsorption of Cd2+ onto the biochars obeyed a pseudo second-order kinetic model, with the BC700 showing the best removal efficiency. Further-more, the effects of the ionic strength and coexisting cations on Cd2+ removal were investigated. The results showed that the removal of Cd2+ was decreased with the increases of NaCl. Among the coexisting cations, the removal of Cd2+ was decreased by Ca2+ and Mg2+, while K+ had limited effect on the removal of Cd2+. In conclusion, the biochar derived from silk waste pyrolysis is a potential attractive adsorbent for the removal of Cd2+ from water.

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.

[Priming effect of biochar on the minerialization of native soil organic carbon and the mechanisms: A review.] / ç”Ÿç‰©ç‚­å¯¹åœŸå£¤æœ‰æœºç¢³çŸ¿åŒ–çš„æ¿€å‘æ•ˆåº”åŠå ¶æœºç†ç ”ç©¶è¿›å±•.

In recent years, studies on carbon sequestration of biochar in soil has been in spotlight owing to the specific characteristics of biochar such as strong carbon stability and well developed pore structure. However, whether biochar will ultimately increase soil carbon storage or promote soil carbon emissions when applied into the soil? This question remains controversial in current academic circles. Further research is required on priming effect of biochar on mineralization of native soil organic carbon and its mechanisms. Based on the analysis of biochar characteristics, such as its carbon composition and stability, pore structure and surface morphology, research progress on the priming effect of biochar on the decomposition of native soil organic carbon was reviewed in this paper. Furthermore, possible mechanisms of both positive and negative priming effect, that is promoting and suppressing the mineralization, were put forward. Positive priming effect is mainly due to the promotion of soil microbial activity caused by biochar, the preferential mineralization of easily decomposed components in biochar, and the co-metabolism of soil microbes. While negative priming effect is mainly based on the encapsulation and adsorption protection of soil organic matter due to the internal pore structure and the external surface of biochar. Other potential reasons for negative priming effect can be the stabilization resulted from the formation of organic-inorganic complex promoted by biochar in the soil, and the inhibition of activity of soil microbes and its enzymes by biochar. Finally, future research directions were proposed in order to provide theoretical basis for the application of biochar in soil carbon sequestration.

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.

[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.