Mercury Isotopes Link Mercury in San Francisco Bay Forage Fish to Surface Sediments
Mercury Isotopes Link Mercury in San Francisco Bay Forage Fish to Surface Sediments
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DOI：
10.1021/es103053y
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发表时间：
2011-02-15
影响因子：
11.4
通讯作者：
Greenfield, Ben K.
中科院分区：
文献类型：
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作者：
Gehrke, Gretchen E.;Blum, Joel D.;Greenfield, Ben K.
要全面评估水生生态系统中的汞暴露情况，就必须确定生物可获得性汞的来源。本研究评估了整个旧金山弗朗西斯科湾（SF湾）的饲料鱼和表层沉积物中的汞之间的关系，并评估了影响汞纳入水生食物网的过程。我们测量了两种近岸鱼类的汞稳定同位素组成，并将其与先前报道的共位潮间带表层沉积物分析进行了比较。鱼类三角洲的Hg-202值（质量相关分馏）表现出明显的空间梯度内SF湾，范围从0.60千分之南部到-0.25千分之北部。鱼类三角洲的Hg-202值始终比沉积物三角洲的Hg-202值高出0.73千分之一（+/- 0.16千分之一，1 SD）。SF湾鱼类和沉积物三角洲Hg-202值相关性良好（r（2）= 0.83），表明沉积物是近岸水生食物网Hg的主要来源。鱼类三角洲的Hg-199值（与质量无关的分馏）范围为0.46 ‰至1.55 ‰，与沉积物值无关，得出的Delta Hg-199/Delta Hg-201比值为1.26（+/- 0.01，1 SD; r（2）= 0.99）。这种不依赖于质量的分馏与甲基汞在进入食物网之前在每个地点不同程度的光降解是一致的。
Identification of sources of biologically accessible Hg is necessary to fully evaluate Hg exposure in aquatic ecosystems. This study assesses the relationship between Hg in forage fish and Hg in surface sediments throughout San Francisco Bay (SF Bay) and evaluates processes influencing the incorporation of Hg into the aquatic food web. We measured the Hg stable isotope compositions of two nearshore fish species and compared them with previously reported analyses of colocated intertidal surface sediments. Fish delta Hg-202 values (mass-dependent fractionation) demonstrated a distinct spatial gradient within SF Bay that ranged from 0.60 parts per thousand in the south to -0.25 parts per thousand in the north. Fish delta Hg-202 values were consistently higher than sediment delta Hg-202 values by 0.73 parts per thousand (+/- 0.16 parts per thousand, 1SD). Fish and sediment delta Hg-202 values in SF Bay proper were well correlated (r(2) = 0.83), suggesting that sediment is a primary source of Hg to the nearshore aquatic food web. Fish Delta Hg-199 values (mass-independent fractionation) ranged from 0.46 parts per thousand to 1.55 parts per thousand, did not correlate with sediment values, and yielded a Delta Hg-199/Delta Hg-201 ratio of 1.26 (+/- 0.01, 1SD; r(2) = 0.99). This mass-independent fractionation is consistent with photodegradation of MeHg to varying degrees at each site prior to incorporation into the food web.