Production and migration of methylmercury in water-level-fluctuating zone of the Three Gorges Reservoir, China: Dual roles of flooding-tolerant perennial herb
Production and migration of methylmercury in water-level-fluctuating zone of the Three Gorges Reservoir, China: Dual roles of flooding-tolerant perennial herb
复制标题
三峡水库消落带甲基汞的产生和迁移：耐涝多年生草本植物的双重作用
DOI：
10.1016/j.jhazmat.2019.120962
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发表时间：
2020
影响因子：
13.6
通讯作者：
Wang Dingyong
中科院分区：
文献类型：
--
作者：
Yin Deliang;Wang Yongmin;Xiang Yuping;Xu Qinqin;Xie Qing;Zhang Cheng;Liu Jiang;Wang Dingyong
消落带是一个普遍存在的有利于汞甲基化的水陆交错带。耐淹植物的演替在改变水湖湖区景观的同时，也带来了一个新的问题，即耐淹植物是否会增加水湖湖区甲基汞的产生，增加对水环境的危害。狗牙根（Cynodon dactylon（L.）以三峡库区消落带中的优势多年生草本植物-虎尾兰（Pers）为研究对象，通过野外观测和稳定同位素示踪实验，研究了虎尾兰在三峡库区消落带甲基汞产生和迁移过程中的作用。结果表明，狗牙根种植区土壤/沉积物中甲基汞含量和汞甲基化率均升高，表明狗牙根的生长可显著增加土壤/沉积物中甲基汞的产生。然而，在三峡库区洪水期间，沉积物中的甲基汞向水体的迁移受到了限制，在植被覆盖区，沉积物中的甲基汞在沉积物和孔隙水之间的分配系数明显较高（p< 0.05），释放通量较低，这表明狗牙根的存在反而可能降低了水体中的甲基汞水平。然而，值得注意的是，由狗牙根引起的土壤/沉积物中甲基汞的升高可能对底栖生物以及TGR食物链构成潜在风险。
Water-level-fluctuating zone (WLFZ) is a prevalent water-land ecotone favorable for mercury (Hg) methylation. The succession of flooding tolerance plants in WLFZ gradually changes the landscape, and also brings a new question worth understanding whether these plants would enhance methylmercury (MeHg) production in WLFZ and increase risks to the aquatic environment. Given bermudagrass (Cynodon dactylon (L). Pers) as the dominant perennial herb with high flooding-tolerance in WLFZ of the Three Gorges Reservoir (TGR), we conducted a comprehensive study to investigate its roles in the production and migration of MeHg in WLFZ by field observations and stable isotope tracer experiments. Results showed that both elevated MeHg levels and Hg methylation rates appeared in soil/sediment in bermudagrass growing area, implying that the growth of bermudagrass could significantly enhance MeHg production. However, MeHg migration from sediment to water was restricted during the flooding period of the TGR, as obviously higher partitioning coefficients of MeHg between the sediment and porewater (p< 0.05) and lower MeHg release fluxes were observed in vegetated area, indicating that the presence of bermudagrass instead probably decreased the water MeHg level. Whereas, it is noteworthy that elevated MeHg in soil/sediment induced by the bermudagrass could pose potential risks to the benthos and further to the TGR food chain.