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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Methylmercury production in a Chesapeake Bay salt marsh
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Methylmercury production in a Chesapeake Bay salt marsh

机译：切萨皮克湾盐沼中的甲基汞生产

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In a detailed study of the biogeochemical factors affecting the methylation of mercury in a Chesapeake Bay salt marsh, we examined relationships between mercury methylation and numerous variables, including sulfate reduction rates, organic carbon mineralization rates, iron and sulfur chemistry, and the character of dissolved organic matter (DOM). Our data show that salt marshes are important sites of de novo methylmercury (MeHg) production in coastal ecosystems. Some of the controls on MeHg production that have been well-described in other ecosystems also impacted MeHg production in this salt marsh, specifically the effect of sulfide accumulation on mercury bioavailability. We observed some novel biogeochemical relationships with Hg(II)-methylation and MeHg accumulation, particularly the positive association of Hg(II)-methylation with zones of microbial iron reduction. On the basis of this relationship, we suggest caution in wetland and groundwater remediation approaches involving iron additions. Aqueous phase Hg complexation appeared to be the dominant control on Hg bioavailability across the marsh sites examined, rather than Hg partitioning behavior. A detailed examination of DOM character in the marsh suggested a strong positive association between Hg(II)-methylation rate constants and increasing DOM molecular weight. Overall, our results indicate that net MeHg production is controlled by a balance between microbial activity and geochemical effects on mercury bioavailability, but that a significant zone of MeHg production can persist in near surface salt marsh soils. Production of MeHg in coastal marshes may negatively impact ecosystems via export to adjacent estuaries or through direct bioaccumulation in birds, fish and amphibians that feed in these highly productive ecosystems.
机译：在影响切萨皮克湾盐沼中汞甲基化的生物地球化学因素的详细研究中，我们研究了汞甲基化与众多变量之间的关系，这些变量包括硫酸盐还原率，有机碳矿化率，铁和硫的化学性质以及溶解特性有机物（DOM）。我们的数据表明，盐沼是沿海生态系统中从头生产甲基汞（MeHg）的重要场所。其他生态系统中已充分描述的一些MeHg生产控制措施也影响了该盐沼的MeHg生产，特别是硫化物积累对汞生物利用度的影响。我们观察到了一些与Hg（II）-甲基化和MeHg积累的新型生物地球化学关系，尤其是Hg（II）-甲基化与微生物铁还原区的正相关。基于这种关系，我们建议在涉及添加铁的湿地和地下水修复方法中保持谨慎。水相汞的络合似乎是整个沼泽地汞生物利用度的主要控制因素，而不是汞分配行为。沼泽中DOM特性的详细检查表明，Hg（II）甲基化速率常数与DOM分子量增加之间有很强的正相关性。总体而言，我们的结果表明，甲基汞的净生产受微生物活性和地球化学对汞生物利用度的影响之间的平衡所控制，但甲基汞生产的重要区域可以持续存在于近地表盐沼土壤中。通过向邻近河口出口或通过以这些高生产力生态系统为食的鸟类，鱼类和两栖动物的直接生物蓄积，沿海沼泽中的甲基汞产量可能对生态系统产生负面影响。

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