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首页> 外文会议>The Sixth Symposium on Environmental Toxicology and Risk Assessment was Presented in Orlando, FL on 15-18 April, 1996. >The influence of floodplains on mercury availability
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The influence of floodplains on mercury availability

机译：洪泛区对汞供应的影响

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The floodplains of the german river Elbe affect the mercury distribution in the river system in two different ways: they act both as a medium-term sink and as a long-term source. The large amounts of mercury deposited onto the floodplains during annual floodings are first effectively fixed in the soils, rendering them basically unavailable. Sequential extraction experiments reveal that only a small fraction of the mercury (< 3 percent) is present in available forms, whereas the vast majority is associated with humic substances or present in sulfidic binding forms. After deposition, a small fraction of the total mercury is gradually remobilized into the aqueous phase bound passively to water-soluble humic acids. the availability of mercury in these complexes is still low, since environmental influences such as changes in pH or redox potential and competition with other cations do not cause any mercury liberation. In the next step, reactions in the aqueous phase lead to the formation of the highly available volatile species Hg~0 and dimethylmercury (DMM). Their evaporation gives rise to a strong mercury flux from the floodplains into the atmosphere. Preliminary mass balances indicate that the majority of the deposited mercury stays bound in the floodplain soils, while small amounts are emitted back into the river's ecosystem. Atmospheric emission is more important as a remobilization pathway than aquatic export.
机译：德国易北河的洪泛区以两种不同的方式影响河流系统中的汞分布：它们既充当中期汇和长期源头。每年洪水期间沉积在泛滥平原上的大量汞首先被有效地固定在土壤中，从而使其基本不可用。连续萃取实验表明，只有一小部分汞（<3％）以可用形式存在，而绝大多数与腐殖质相关或以硫键结合形式存在。沉积后，总汞中的一小部分逐渐重新固定到与水溶性腐殖酸被动结合的水相中。这些配位化合物中汞的利用率仍然很低，因为诸如pH值或氧化还原电位的变化以及与其他阳离子的竞争等环境影响不会导致任何汞的释放。在下一步中，水相中的反应导致形成高度可用的挥发性物质Hg-0和二甲基汞（DMM）。它们的蒸发引起从洪泛区到大气的强烈汞通量。初步的质量平衡表明，大部分沉积的汞保持在洪泛区土壤中的结合力，而少量汞又被排放回河流的生态系统。大气排放作为一种复员途径比水生出口更为重要。

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