Exploring the Importance of Aging in Contaminant Bioavailability and Remediation

描述（由申请人提供）：人类接触许多环境污染物，如滴滴涕及其代谢物（DDTs）、多氯联苯、多环芳烃和二恶英，主要通过食物链转移和生物放大作用发生。由于它们对天然有机物的亲和力， 这些污染物主要分布在土壤或沉积物中。最初的营养转移涉及沉积物或土壤生物的吸收，这决定了 污染现场的最终人类健康风险。一个经常被忽视的事实是，大多数超级基金场地的污染是历史事件的结果，这些场地的污染物在同一介质中存在多年或数十年，这是一个地球化学过程，被称为老化。老化通常导致较低的污染物生物利用度，即，减少进入食物链的可能性。然而，目前，人们对老化效应缺乏很好的了解，其价值在当前的风险评估和修复实践中没有得到利用或开发。在本项目中，我们将首先开发一种方法来测量DDTs和PCBs在野外老化沉积物中的老化效应，通过量化它们的相对生物有效性。我们将使用同步生物累积试验来验证该方法。然后，我们将应用该方法收集的沉积物样品作为深度（反映沉积在不同的历史时期）和空间位置（反映不同的沉积物性质）在帕洛斯弗迪斯（PV）货架超级基金网站关闭洛杉矶海岸的函数。PV陆架沉积物含有高水平（高达200毫克/千克）的滴滴涕（特别是p，p '-DDE）和多氯联苯，其沉积时间可追溯到60年前。相关分析将揭示年龄与生物有效性之间的关系，并阐明沉积物性质的影响。衰老引起的生物利用度变化将被纳入营养食物链模型，以改善对生态受体和人类的危害估计。黑碳吸附剂（例如，活性炭、木炭、生物炭）越来越多地用于补救，因为它们能立即消除土壤或沉积物中的HOCs。我们会进一步进行长期的实验室培养实验，以了解这类改性对污染物老化或永久封存的影响。通过该项目，我们将全面了解老化效应及其在调节污染物生物利用度方面的作用，并抓住其应用机会，以改善风险评估和缓解。

DESCRIPTION (provided by applicant): Human exposure to many environmental contaminants such as DDT and metabolites (DDTs), PCBs, PAHs, and dioxins occurs primarily through food chain transfer and biomagnification. Due to their affinity for natural organic matter, these contaminants are distributed predominantly in the soil or sediment compartment. The initial trophic transfer involves uptake by sediment or soil-dwelling organisms, which dictates the ultimate human health risk of a contamination site. An often-neglected fact is that contamination at most Superfund sites is a result of historical events, and that contaminants at these sites have resided in the same media for many years or decades, a biogeochemical process loosely termed aging. Aging generally leads to lower contaminant bioavailability, i.e., a reduced potential for entering the food chain. However, at present, there lacks a good understanding of aging effects and its value is not used or exploited in current risk assessment and remediation practices. In this project, we will first develop a method to measure aging effects of DDTs and PCBs in field-aged sediments by quantifying their relative bioavailability. We will use concurrent bioaccumulation tests to validate the method. We will then apply the method to sediment samples collected as a function of depth (reflecting deposition at different historical times) and spatial location (reflecting different sediment properties) at the Palos Verdes (PV) Shelf Superfund site off the Los Angeles coast. The PV Shelf sediments contain high levels (up to 200 mg/kg) of DDTs (especially p,p'-DDE) and PCBs deposited from as far back as 60 years ago. Correlation analysis will reveal the relationship between age and bioavailability, and elucidate the influence of sediment properties. The aging-induced bioavailability changes will be incorporated into trophic food chain models to improve the estimation of hazards to ecological receptors and humans. Black carbon sorbents (e.g., activated carbon, charcoal, biochar) are increasingly used in remediation, as they immediately immobilize HOCs in soil or sediment. We will further carry out long-term laboratory incubation experiments to understand the effect of such amendment on contaminant aging or permanent sequestration. Through this project, we will obtain a holistic understanding of aging effects and its role in regulating contaminant bioavailability, and capture opportunities for their application to achieve improved risk assessment and mitigation.