Reactive Transport Modeling of Subaqueous Sediment Caps and Implications for the Long-Term Fate of Arsenic, Mercury, and Methylmercury.
Reactive Transport Modeling of Subaqueous Sediment Caps and Implications for the Long-Term Fate of Arsenic, Mercury, and Methylmercury.
复制标题
水下沉积物盖的反应输运模型及其对砷、汞和甲基汞长期命运的影响。
DOI：
10.1007/s10498-012-9165-4
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发表时间：
2012
影响因子：
1.6
通讯作者：
O'Day,PeggyA
中科院分区：
文献类型：
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作者：
Bessinger,BradA;Vlassopoulos,Dimitri;Serrano,Susana;O'Day,PeggyA
建立了一个包含一整套平衡和动力学化学反应的一维化学反应输运模型，模拟了砷和汞在水下沉积物盖中的归趋和输运。模型模拟（50年）进行了淡水和河口的情况下，厌氧孔隙水和扩散或扩散加0.1米/年向上平流通量通过帽。生物栖息地层在顶部0.15米的上限模拟与添加有机碳。对于砷，硫酸盐还原条件的产生限制了可用于吸附的氧化铁相的形成。因此，当进水浓度高且吸附能力不足时，水下沉积物盖对于减轻污染物砷迁移可能相对无效。对于汞，硫酸盐还原促进沉淀的metacinnabar（HgS）的栖息地层以下，并在整个沉积物-水界面的相关通量低。因此，盖层厚度是一个关键的设计参数，可以通过调整来控制硫化汞沉淀的沉积物-水界面以下的深度。最高溶解甲基汞浓度发生在河口环境中的栖息地层平流孔隙水的条件下，但最高的沉积物浓度预计会发生在淡水环境中，由于吸附沉积物有机质。特定地点的反应性输运模拟是一个强大的工具，用于确定主要控制沉积物和孔隙水污染物砷和汞的浓度，结果从物理条件和生物介导的化学反应之间的耦合。
A 1-D biogeochemical reactive transport model with a full set of equilibrium and kinetic biogeochemical reactions was developed to simulate the fate and transport of arsenic and mercury in subaqueous sediment caps. Model simulations (50 years) were performed for freshwater and estuarine scenarios with an anaerobic porewater and either a diffusion-only or a diffusion plus 0.1-m/year upward advective flux through the cap. A biological habitat layer in the top 0.15 m of the cap was simulated with the addition of organic carbon. For arsenic, the generation of sulfate-reducing conditions limits the formation of iron oxide phases available for adsorption. As a result, subaqueous sediment caps may be relatively ineffective for mitigating contaminant arsenic migration when influent concentrations are high and sorption capacity is insufficient. For mercury, sulfate reduction promotes the precipitation of metacinnabar (HgS) below the habitat layer, and associated fluxes across the sediment–water interface are low. As such, cap thickness is a key design parameter that can be adjusted to control the depth below the sediment–water interface at which mercury sulfide precipitates. The highest dissolved methylmercury concentrations occur in the habitat layer in estuarine environments under conditions of advecting porewater, but the highest sediment concentrations are predicted to occur in freshwater environments due to sorption on sediment organic matter. Site-specific reactive transport simulations are a powerful tool for identifying the major controls on sediment- and porewater-contaminant arsenic and mercury concentrations that result from coupling between physical conditions and biologically mediated chemical reactions.