Mercury Isotope Study of Sources and Exposure Pathways of Methylmercury in Estuarine Food Webs in the Northeastern U.S.

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• 作者：Sae Yun Kwon ; Joel D. Blum ; Celia Y. Chen ; Dustin E. Meattey ; Robert P. Mason
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：September 2, 2014
• 年：2014
• 卷：48
• 期：17
• 页码：10089-10097
• 全文大小：313K
• ISSN：1520-5851

文摘

We measured mercury (Hg) isotope ratios in sediments and various estuarine organisms (green crab, blue mussel, killifish, eider) to investigate methylmercury (MMHg) sources and exposure pathways in five Northeast coast (U.S.) estuaries. The mass independent Hg isotopic compositions (MIF; 螖¹⁹⁹Hg) of the sediments were linearly correlated with the sediment 1/Hg concentrations (螖¹⁹⁹Hg: r² = 0.77, p < 0.05), but the mass dependent isotope compositions (MDF; 未²⁰²Hg) were not (r² = 0.26, p = 0.16), reflecting inputs of anthropogenic Hg sources with varying 未²⁰²Hg. The estuarine organisms all display positive 螖¹⁹⁹Hg values (0.21 to 0.98 鈥? indicating that MMHg is photodegraded to varying degrees (5鈥?2%) prior to entry into the food web. The 未²⁰²Hg and 螖¹⁹⁹Hg values of most organisms can be explained by a mixture of MMHg and inorganic Hg from sediments. At one contaminated site mussels have anomalously high 未²⁰²Hg, indicating exposure to a second pool of MMHg, compared to sediment, crabs and fish. Eiders have similar 螖¹⁹⁹Hg as killifish but much higher 未²⁰²Hg, suggesting that there is an internal fractionation of 未²⁰²Hg in birds. Our study shows that Hg isotopes can be used to identify multiple anthropogenic inorganic Hg and MMHg sources and determine the degree of photodegradation of MMHg in estuarine food webs.