Laboratory for Agricultural Wastes Treatment and Recycling, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing, Jiangsu, 210014, People's Republic of China.
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, Fujian, 361021, People's Republic of China.
Environ Pollut. 2017 Jan;220(Pt A):514-522. doi: 10.1016/j.envpol.2016.09.095. Epub 2016 Oct 6.
Previous studies have shown that biochar enhances microbial reduction of iron (Fe) oxyhydroxide under anaerobic incubation. However, there is a lack of data on its influence on arsenic (As) release from As-contaminated paddy soils. In this study, paddy soil slurries (120 mg As kg) were incubated under anaerobic conditions for 60 days with and without the addition of biochar (3%, w/w) prepared from rice straw at 500 °C. Arsenic release, Fe reduction, and As fractionation were determined at 1, 10, 20, 30, and 60 d, while Illumina sequencing and real-time PCR were used to characterize changes in soil microbial community structure and As transformation function genes. During the first month of incubation, As released into soil solution increased sharply from 27.9 and 55.9 to 486 and 630 μg kg in unamended and biochar amended slurries, with inorganic trivalent As (As) being the dominant specie (52.7-91.0% of total As). Compared to unamended slurries, biochar addition increased As and ferrous ion (Fe) concentrations in soil solution but decreased soil As concentration in the amorphous Fe/Al oxide fraction (F3). Difference in released As between biochar and unamended treatments (ΔAs) increased with incubation time, showing strong linear relationships (R = 0.23-0.33) with ΔFe and ΔF3, confirming increased As release due to enhanced Fe reduction. Biochar addition increased the abundance of Fe reducing bacteria such as Clostridum (27.3% vs. 22.7%), Bacillus (3.34% vs. 2.39%), and Caloramator (4.46% vs. 3.88%). In addition, copy numbers in biochar amended slurries of respiratory As reducing (arrA) and detoxifying reducing genes (arsC) increased 19.0 and 1.70 fold, suggesting microbial reduction of pentavalent As (As) adsorbed on Fe oxides to As, further contributing to increased As release.
先前的研究表明，生物炭在厌氧孵育条件下可增强微生物对铁（Fe）氢氧化物的还原。然而，有关其对砷（As）污染稻田土壤中砷释放影响的数据却十分有限。本研究采用稻草在 500°C 下制备的 3%（w/w）生物炭，在厌氧条件下对含 120 mg As kg-1 的稻田土壤泥浆进行 60 天的孵育实验，研究其对砷释放的影响。在 1、10、20、30 和 60 d 时，测定砷释放、铁还原和砷形态分布，采用 Illumina 测序和实时 PCR 技术来描述土壤微生物群落结构和砷转化功能基因的变化。在孵育的第一个月，未添加和添加生物炭的泥浆中，土壤溶液中的砷分别从 27.9 和 55.9 μg kg-1 急剧增加到 486 和 630 μg kg-1，无机三价砷（As）是主要形态（占总砷的 52.7-91.0%）。与未添加泥浆相比，生物炭的添加增加了土壤溶液中的砷和亚铁离子（Fe）浓度，但降低了无定形铁/铝氧化物（F3）中的土壤砷浓度。生物炭和未添加处理之间释放的砷的差异（ΔAs）随孵育时间的增加而增加，与 ΔFe 和 ΔF3 呈强线性关系（R=0.23-0.33），这证实了由于铁还原增强而导致的砷释放增加。生物炭的添加增加了产铁还原细菌的丰度，如梭菌（27.3%比 22.7%）、芽孢杆菌（3.34%比 2.39%）和喜热菌（4.46%比 3.88%）。此外，在添加生物炭的泥浆中，呼吸砷还原（arrA）和解毒还原基因（arsC）的拷贝数分别增加了 19.0 倍和 1.70 倍，表明五价砷（As）被吸附在铁氧化物上的微生物还原为 As，这进一步导致了砷的释放增加。
