Water/sediment & model & criteria for arsenic & chrome

该项目有两个目的：为建立砷和铬的沉积物质量标准奠定化学基础；建立水柱-沉积物去向和迁移耦合模型。目前，分别有113个和142个超级基金站点将水中沉积物中的砷和铬列为污染物。因此，至关重要的是要有可靠的方法来确定金属对环境和人类健康构成风险的沉积物浓度。目前可用的方法是基于总砷和总铬的浓度，忽略了已知不能预测毒性的生物利用度。我们打算使用EPA目前正在使用的平衡分配(EQP)模型来生成这些标准。这种方法包括：第一，确定调节孔隙水浓度的一个或多个固相；第三，确定沉淀物结合金属的再活化(和未来暴露)的可能性。对于水柱动物及其人类消费者来说，金属从沉积物释放到上覆水的程度，以及发生反向过程的程度，是全面分析这些金属对环境和人类健康构成的风险的关键组成部分。我们打算首先开发沉积物模型，然后再开发砷和铬的水柱-沉积物耦合模型。沉积物模型的目的是计算金属从沉积物到孔隙水的通量，并最终到达上覆水。这种释放在很大程度上取决于还原的固相金属物种的氧化速度。一旦判定沉积物对环境或人类健康构成威胁，就有必要预测沉积物和上覆水中未来的暴露浓度，并评估补救行动的效果。这一步骤需要使用数学模型来描述运输和化学/生化反应的综合影响。我们打算构建这些模型，并将它们应用于文献中提供的数据集。

This project has two purposes: to develop the chemical basis for establishing sediment quality criteria for arsenic and chromium for arsenic and chromium; and to construct coupled water column-sediment fate and transport models. Arsenic and chromium in aquatic sediments are currently listed as contaminants at 113 and 142 Superfund sites, respectively. It is of critical importance, therefore, to have reliable methods for determining the sediment concentrations at which the metals pose an environmental and human health risk. Currently available methods are based on the concentration of total arsenic and chromium that ignore bioavailability that are known not to be predictive of toxicity. We intend to use the Equilibrium Partitioning (EqP) model, that is currently being used by EPA, in order to generate these criteria. This approach involves first: determining the solid phase or phases that regulate pore water concentrations; and third: determining the potential for remobilization (and future exposure) of sediment bound metal. For water column animals and their human consumers, the extent to which metals are released from sediments to the overlying water, and the extent to which the reverse process occurs, are critical components in a comprehensive analysis of the risk environmental and human health posed by these metals. We intend to develop sediment models first and then coupled water column-sediment models for arsenic and chromium. The purpose of the sediment model is to computer the flux of metal from the sediment to pore water, and ultimately, to the overlying water. This release is determined in large measure by the rate of oxidation of the reduced solid phase metal species. Once sediments are judged to pose an environmental or human health risk, it is necessary to project future exposure concentrations in the sediments and overlying water and to evaluate the efficacy of remedial actions. This step requires the use of mathematical models to described the combined effects of transport and chemical/biochemical reactions. We intend to construct these models and to apply them to data sets that are available in the literature.