Xing Ying, Wang Jianxu, Kinder Christoph E S, Yang Xing, Slaný Michal, Wang Bing, Song Hocheol, Shaheen Sabry M, Leinweber Peter, Rinklebe Jörg
School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550002, PR China; University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany.
University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550082, PR China.
Environ Int. 2022 Oct;168:107484. doi: 10.1016/j.envint.2022.107484. Epub 2022 Aug 24.
Biochar amendment to paddy soils was promising to mitigate mercury (Hg) accumulation in rice; thus, it was applied to reduce human Hg exposure via rice consumption. However, how biochar affects Hg mobilization and MeHg formation in soil under changed redox potential (E) conditions remained unknown. Here, we explored the change of dissolved total Hg (DTHg) and dissolved MeHg (DMeHg), and their controlling biogeochemical factors in a soil with(out) biochar amendment under changing E conditions using biogeochemical microcosm. Biochar amendment resulted in a widen E range (-300 to 400 mV) compared to the control (-250 to 350 mV), demonstrating that biochar promoted reduction-oxidization reactions in soil. Biochar amendment enhanced Hg mobilization by mediating reductive dissolution of Fe/Mn (hydr)oxides. Thus, the increased Hg availability promoted MeHg formation in the soils. Biochar amendment changed the soil organic matter (SOM) composition. Positive correlations between the relative abundance of LIPID (lipids, alkanes/alkenes), ALKYL (alkylaromatics), and suberin and MeHg concentrations indicate that these SOM groups might be related to MeHg formation. Biochar enhanced the releasing and methylation of Hg by promoting the mobilization of Fe(oxyhydr)oxides and alternation of carbon chemistry under dynamic E conditions. There is an unexpected environmental risk associated with biochar application to paddy soils under dynamic E condition, and one should be aware this risk when applying biochar aiming to minimize human Hg exposure health risks via rice consumption.
向稻田土壤中添加生物炭有望减轻水稻中的汞（Hg）积累；因此，它被用于减少通过食用大米而导致的人体汞暴露。然而，在氧化还原电位（E）条件变化的情况下，生物炭如何影响土壤中汞的迁移和甲基汞的形成仍不清楚。在这里，我们使用生物地球化学微观模型，探讨了在氧化还原电位变化的条件下，添加（或未添加）生物炭的土壤中溶解态总汞（DTHg）和溶解态甲基汞（DMeHg）的变化及其控制生物地球化学因素。与对照（-250至350 mV）相比，添加生物炭导致氧化还原电位范围变宽（-300至400 mV），这表明生物炭促进了土壤中的氧化还原反应。添加生物炭通过介导铁/锰（氢）氧化物的还原溶解来增强汞的迁移。因此，汞有效性的增加促进了土壤中甲基汞的形成。添加生物炭改变了土壤有机质（SOM）的组成。脂质（LIPID，包括脂质、烷烃/烯烃）、烷基芳烃（ALKYL）和木栓质的相对丰度与甲基汞浓度之间的正相关表明，这些土壤有机质组分可能与甲基汞的形成有关。在动态氧化还原电位条件下，生物炭通过促进铁（氢）氧化物的迁移和碳化学的改变，增强了汞的释放和甲基化。在动态氧化还原电位条件下，向稻田土壤中施用生物炭存在意想不到的环境风险，在为尽量减少通过食用大米导致的人体汞暴露健康风险而施用生物炭时，人们应意识到这一风险。
