【摘要】 大气汞沉降是汞从排放源进入地表系统最主要的迁移途径,利用汞同位素追踪汞在大气中的迁移转化规律及潜在来源对研究汞的生物地球化学循环具有重要意义.本研究于2012—2013年对厦门市小坪、坂头、鼓浪屿和洪文站点降水中总汞（THg）浓度和汞同位素的变化特征进行了研究.结果表明,厦门降水中THg浓度为1.0～59.4 ng·L^-1,大气THg湿沉降量为13.1μg·m^-2·a^-1.厦门冷、暖季降水中THg浓度相当,但由于暖季丰沛的降水量,导致暖季THg的湿沉降量约为冷季的2.5倍.降水样品中均表现出负的偶数汞同位素质量分馏(δ²⁰²Hg,-2.2‰～-1.5‰)、正的奇数汞同位素非质量分馏(Δ¹⁹⁹Hg,0.08‰～0.22‰),以及轻微偏正的偶数汞同位素非质量分馏(Δ²⁰⁰Hg,0.01‰～0.07‰).厦门降水中奇数汞同位素非质量分馏是大气汞液相光致还原反应的结果.偶数汞同位素非质量分馏不明显与其处于较低的纬度有关.厦门降水中δ²⁰²Hg接近于厦门当地及贵州燃煤烟气中的δ²⁰²Hg值,表明厦门降水中汞可能受到本地或传输过来的燃煤排放的影响.更多还原

【Abstract】 Atmospheric mercury（Hg） deposition is the predominant pathway of mercury transferring from emission sources to terrestrial ecosystems.Tracing the transport and transformation of Hg in the atmosphere and the potential sources of atmospheric Hg with mercury isotope signature is of great significance for the research on the biogeochemical cycle of Hg.To investigate the characteristics of total mercury（THg） and Hg isotopic composition in precipitation in a coastal city, the precipitation samples were collected simultaneously at Xiaoping, Bantou, Hongwen, and Gulangyu sites in Xiamen, China during 2012—2013 in this study.The concentrations of THg in precipitation samples were in the range of 1.0～59.4 ng·L^-1, and wet deposition flux was 13.1 μg·m^-2·a^-1.The concentration of THg in precipitations in warm season was comparable to that in cold season.The wet deposition flux of THg in warm season was 2.5 times higher than that in cold season due to the abundant precipitation amount.All precipitation samples displayed negative mass-dependent fractionation of even isotopes(δ²⁰²Hg,-2.2‰～-1.5‰), positive mass-independent fractionation of odd isotopes(Δ¹⁹⁹Hg, 0.08‰～0.22‰), and slightly positive mass-independent fractionation of even isotopes(Δ²⁰⁰Hg, 0.01‰～0.07‰).These results suggested that photoreduction in droplets induced odd Hg isotope anomalies, while little mass-independent fractionation of even Hg isotopes in Xiamen was probably related to low latitude.The δ²⁰²Hg of precipitation samples was close to that of coal-burning flue gas in Xiamen and Guizhou, which indicated that Hg in precipitation might be affected by both local emission of coal-fired plant and transportation of coal combustion emission.更多还原