Project 5: Geochemical Processes Affecting Temporal Variablitity in Soil

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天然组成部分。因此，它们具有不同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操作定义的测试，这些测试模拟了人体消化系统中土壤中金属的释放。该提案的一个目标是能够从地球化学角度界定金属的生物可获得性，而不是以操作上界定的提取方法为基础。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相结合的方式进行测试，以确定随着时间的推移而增加金属生物利用度的过程和随着时间的推移而减少金属生物利用度的过程之间的相互作用。通过这些实验，我们将测试通过口服摄入的金属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性来预测。 这项研究将弥合地质学和毒理学之间目前的差距。目前的风险评估方法可以确定土壤中的金属是否可能产生风险，但不能确定为什么。我们的目的是表明，通过结合适量的地球化学分析，我们可以大大提高土壤中金属的风险评估，显示为什么有些土壤施加风险，而其他土壤具有类似的金属水平不施加风险。此外，通过对金属时间循环的类似适度理解，我们可以证明土壤中金属的生物可及性不是时不变的。有了这些知识，风险评估可以主动了解当前和未来风险的性质。

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.