Project 5: Geochemical Processes Affecting Temporal Variablitity in Soil

对环境中有毒重金属的研究具有挑战性，因为金属是我们环境的自然组成部分。因此，它们有独特的生物地球化学循环，控制着它们的流动性、命运和毒性。不了解这些生物地球化学循环将导致无法充分评估不利影响。目前通过口服摄入途径对金属进行风险评估的技术是基于可操作定义的测试，这些测试模拟了金属从土壤中释放到人体消化系统中。本提案的目标是能够在地球化学术语中定义金属的生物可及性，而不是基于操作上定义的提取方法。这些目标将通过对金属污染土壤和采矿废物进行实验室和现场研究来检验，以确定随着时间推移增加金属生物利用度的过程和随着时间推移减少金属生物利用度的过程的相互作用。通过这些实验，我们将测试金属通过口服摄入的生物可及性是否可以从金属的潜在形态和土壤本身的特征来预测。

The study of toxic heavy metals in the environment is challenging because metals are a natural component of our environment. As such, they have distinct biogeochemical cycles that govern their mobility, fate, and toxicity. A failure to understand these biogeochemical cycles will lead to a failure to adequately assess adverse impacts. Current risk assessment techniques for metals via the oral ingestion route are based on operationally defined tests which mimic the release of metals from soil in the human digestive system. A goal of this proposal is to be able to define the bioaccessibility of metals in geochemical terms, not based on operationally defined extraction methods. These goals will be tested through a combination of laboratory and in situ studies of metal-contaminated soils and mining wastes to characterize the interplay of processes that increase metal bioavailability over time and those that decrease metal bioavailability over time. Through these experiments, we will test whether the bioaccessibility of metals through oral ingestion can be predicted from the underlying speciation of metals and the characteristics of the soil itself. This study will bridge the current gap between geology and toxicology. Current risk assessment methods can determine if metals in a soil may exert risk, but not why. It is our intent to show that through the incorporation of a modest amount of geochemical analysis, we can greatly improve risk assessment for metals in soils by showing why some soils exert risk while other soils with similar levels of metals do not exert risk. In addition, with a similarly modest understanding of the temporal cycling of metals, we can show that bioaccessibility of metals in soils is not time invariant. With this knowledge, risk assessment can be proactive in understanding the nature of both current and future risks.