Toxicity and Mobilization of Metals and Metal Mixtures

本研究的目标是开发预测单个金属的毒性和动员的模型 以及沉积物中的金属混合物这些预测对于评估与以下因素相关的风险至关重要： 污染的沉积物在超级基金网站。在过去的超级基金基础研究项目中，我们开发了 沉积物中个别金属镉、铜、镍、铅和锌毒性的评估方法 酸挥发性硫化物（AVS）。我们建议开发一个模型，预测沉积物中金属的毒性 很少或没有AVS。这就需要预测沉积物金属在其他重要沉积物中的分配情况。 沉积物相-沉积物有机碳，如果供应充足，然后是其他相（如铁 氢氧化物），这是重要的好氧层的沉积物。我们还建议开发下一个 生成用于预测沉积物中金属活动的模型，其中明确包括 动员机制。我们打算直接模拟金属硫化物氧化的机制， 将它们与沉积物中锰和铁的循环联系起来。我们已经包括了这样一个机制 在本项目中涉及Fe（II）促进的砷氧化。我们建议将这项工作扩大到 金属硫化物的氧化。 我们的具体目标是： 1.对于阳离子金属，扩展沉积物生物配体模型（BLM），使其能够预测 通过考虑金属和主要离子与有机物的竞争性相互作用， 碳、（含水）氧化物表面、粘土和底栖生物的吸收点。 2.对于沉积物中形成不溶性金属硫化物的金属（Cd、Cu、Ni、Pb、Zn）， 金属硫化物的氧化及其对金属活动中夹杂物的溶解参数的依赖性 模型 3.对于砷，研究沉积物中存在的无机和有机配体的影响， Fe（II）催化的亚砷酸盐氧化的速率和最终从砷的活化速率 沉积物 4.对于铬，研究天然有机物对铬（III）氧化速率的影响 沉积物中的锰氧化物，以及随后释放的铬（VI）到孔隙水和 上覆水 5.对于以上讨论的金属，为了构建一个综合模型， 和毒性机制，以及氧化还原敏感物种的季节性循环模型，包括 沉积物中的氧、有机质、铁、锰和硫。

The goal of this research is to develop models for predicting the toxicity and mobilization of individual metals and metal mixtures in sediments. These predictions are critical in evaluating the risk associated with contaminated sediments at Superfund sites. In past Superfund basic research projects, we have developed methods of assessing the toxicity of individual metals - Cd, Cu, Ni, Pb and Zn - for sediments with excess acid volatile sulfides (AVS). We propose to develop a model that predicts the toxicity of metals in sediments with little or no AVS. This requires a prediction of the partitioning of sediment metals to the other important sediment phases - sediment organic carbon if it is in sufficient supply, and then the other phases (e.g. iron oxyhydroxides) that are important in the aerobic layer of sediments. We also propose to develop the next generation of models for the prediction of mobilization of metals from sediments that explicitly include the mechanisms of mobilization. We intend to model the mechanisms of metal sulfide oxidation directly and to relate them to the cycles of manganese and iron in sediments. We have included such a mechanism nvolving the Fe(ll)-facilitated oxidation of arsenic in our present project. We propose to extend this work to the oxidation of metal sulfides. Our specific aims are: 1. For cationic metals, to extend the sediment Biotic Ligand Model (BLM) so that it can predict the toxicity of metals and metal mixtures by considering competitive interactions of metals and major ions to the organic carbon, (hydrous) oxide surfaces, clays and to uptake sites on benthic organisms. 2. For metals that form insoluble metal sulfides in sediments (Cd, Cu, Ni, Pb, Zn), to determine the rates of metal sulfide oxidation and their dependence on solution parameters for inclusion in metal mobilization models. 3. For arsenic, to investigate the effects of inorganic and organic ligands present in sediments that affect the rate of Fe(ll)-catalyzed oxidation of arsenite and ultimately the rates of arsenic mobilization from sediments. 4. For chromium, to investigate the effect of natural organic matter on the rates of chromium(lll) oxidation by manganese oxide in sediments, and the subsequent release of chromium(VI) to the pore water and the overlying water. 5. For the metals discussed above, to construct an integrated model that combines the metal mobilization and toxicity mechanisms, together with a model of the seasonal cycling of redox-sensitive species including oxygen, organic matter, iron, manganese and sulfur in sediments.