Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Environ Geochem Health. 2022 Dec;44(12):4405-4422. doi: 10.1007/s10653-022-01205-z. Epub 2022 Jan 28.
Mercury (Hg) is extremely poisonous and can be absorbed through touch, inhalation, or consumption. In the living environment, Hg in contaminated sediment can be transferred into grass by the direct absorption through the roots or shoots. The intake of Hg due to Hg emissions may pose a threat to living bodies especially to human beings. The present study aims to provide a novel insight about total mercury (THg) and methyl mercury (MeHg) in a riparian grass (Cynodon dactylon (L).Pers) and sediments during the discharging phase (summertime at 145 m water level) in Three Gorges Reservoir (TGR-China); where C. dactylon is a dominant perennial herb in the riparian zone. Yet, the potential risk of Hg contamination in the riparian ecosystem is not thoroughly assessed in the dam regulated reservoir. This study was conducted in the riparian zones of the reservoir formed by a mega dam (Three Gorge Dam) which regulates the water levels during the summer and winter period in the TGR. Our results showed that riparian sediments were acting as a sink for THg and MeHg. Insignificant correlation of THg and MeHg was found between the amphiphyte C. dactylon and its surrounding sediments in the TGR. Bioconcentration factors values for MeHg were found higher than 1 in all study locations in the riparian zones in TGR, which could be due to action of certain bacteria/purely chemical-based methylation on inorganic form of Hg. Additionally, translocation factor indices also highlighted that the amphiphyte C. dactylon was MeHg accumulator in riparian zones. These results suggested that since riparian sediment was found acting as the sink for THg and MeHg during discharging phase, MeHg contamination in the amphiphyte C. dactylon in riparian zones was not caused by the riparian sediments but by other factors, for instance, the anthropogenic activities in the TGR. Finally, this study leads to conclude that amphiphyte C. dactylon can be used as biomonitoring agent for Hg pollution in the TGR.
汞（Hg）是一种剧毒物质，可通过触摸、吸入或摄入而被人体吸收。在生活环境中，受污染沉积物中的汞可通过植物的根系或茎叶直接吸收而转移到草中。由于汞排放而摄入的汞可能对生物体，尤其是人类构成威胁。本研究旨在为三峡水库（中国）放水期（夏季 145 米水位时）滨岸草（Cynodon dactylon（L.）Pers）和沉积物中的总汞（THg）和甲基汞（MeHg）提供新的见解；C. dactylon 是滨岸带的一种主要多年生草本植物。然而，大坝调节水库中滨岸生态系统汞污染的潜在风险尚未得到充分评估。本研究在三峡大坝形成的滨岸带进行，该大坝在夏季和冬季调节水库水位。我们的研究结果表明，滨岸沉积物是 THg 和 MeHg 的汇。在三峡水库中，我们发现水生植物 C. dactylon 与其周围沉积物之间的 THg 和 MeHg 相关性不显著。在三峡滨岸带所有研究地点，MeHg 的生物浓缩因子值均高于 1，这可能是由于某些细菌/纯粹的化学甲基化作用将无机汞形式转化为甲基汞。此外，迁移因子指数也突出表明，滨岸带的水生植物 C. dactylon 是 MeHg 的积累者。这些结果表明，由于在放水期滨岸沉积物对 THg 和 MeHg 起吸收作用，滨岸带水生植物 C. dactylon 中的 MeHg 污染不是由滨岸沉积物引起的，而是由其他因素引起的，例如三峡的人为活动。最后，本研究得出结论，水生植物 C. dactylon 可作为三峡水库 Hg 污染的生物监测剂。
