School of Environmental Science & Engineering, Tianjin University, Tianjin, 300350, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
School of Environmental Science & Engineering, Tianjin University, Tianjin, 300350, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Pollut. 2021 Oct 1;286:117290. doi: 10.1016/j.envpol.2021.117290. Epub 2021 May 3.
Biochar amendment has the potential to reduce methylmercury (MeHg) uptake by rice grains in soil-rice ecosystem. Considering that sulfur can strongly bind Hg and thus reduce its bioavailability, S-modified biochar has been used to immobilize Hg in soils. However, whether natural S-enriched biochar can further reduce Hg and MeHg phytoavailability remains unknown. Moreover, the rhizosphere is one of the most important microbial hotspots regulating the pollutant dynamics in terrestrial ecosystems. Therefore, it is of greater practical significance to examine the impact of biochar amendment on MeHg production and phytoavailability in the rhizosphere versus nonrhizosphere. Here, by conducting a pot experiment, we evaluated the efficacy of biochar derived from sulfur-enriched oilseed rape straw to reduce MeHg accumulation in rice. The results demonstrated that: (1) biochar-induced enhancement of chloride ion and sulfate levels in the overlying water and pore water facilitate microbial methylation of Hg and thus MeHg production in rhizosphere soil. (2) biochar amendment increased rhizosphere soil sulfur content and humic acid-like substances, strengthening MeHg binding to soil, and thus reducing grain MeHg levels by 47%-75%. Our results highlight the necessity to applying natural sulfur-rich biochar accompanied with exogenous sulfur to further reduce MeHg phytoavailability.
生物炭改良有可能减少土壤-水稻生态系统中大米对甲基汞（MeHg）的吸收。考虑到硫可以强烈结合汞，从而降低其生物利用度，因此已使用 S 改性生物炭来固定土壤中的汞。然而，天然富硫生物炭是否可以进一步降低汞和 MeHg 的植物可利用性尚不清楚。此外，根际是调节陆地生态系统中污染物动态的最重要的微生物热点之一。因此，研究生物炭改良对根际和非根际中 MeHg 产生和植物可利用性的影响具有更大的实际意义。在这里，通过进行盆栽实验，我们评估了源自富硫油菜秸秆的生物炭降低水稻中 MeHg 积累的效果。结果表明：（1）生物炭诱导的上覆水和孔隙水中氯离子和硫酸盐水平的增强促进了 Hg 的微生物甲基化，从而导致根际土壤中 MeHg 的产生。（2）生物炭改良增加了根际土壤的硫含量和腐殖酸类物质，增强了 MeHg 与土壤的结合，从而使稻谷中的 MeHg 水平降低了 47%-75%。我们的研究结果强调了有必要应用天然富硫生物炭和外加硫来进一步降低 MeHg 的植物可利用性。
