Exploring the Importance of Aging in Contaminant Bioavailability and Remediation

描述(申请人提供)：人类接触到许多环境污染物，如滴滴涕和代谢物、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。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 污染场地的最终人类健康风险。一个经常被忽视的事实是，大多数超级基金遗址的污染是历史事件的结果，这些遗址的污染物已经在同一介质中停留了多年或数十年，这是一种生物地球化学过程，大致上被称为老化。老化通常会导致污染物的生物利用度降低，即进入食物链的可能性降低。然而，目前人们对老化效应的认识还不够深入，其价值在目前的风险评估和补救实践中还没有得到充分的利用和开发。在这个项目中，我们将首先开发一种方法来测量野外老化沉积物中DDT和PCbs的老化效应，方法是量化它们的相对生物利用度。我们将使用并发生物累积测试来验证该方法。然后，我们将把这种方法应用于在洛杉矶海岸外的Palos Verdes(PV)Shelf Superfund站点收集的沉积物样本，作为深度(反映不同历史时期的沉积)和空间位置(反映不同的沉积物属性)的函数。光伏陆架沉积物含有高水平(高达200毫克/公斤)的滴滴涕(尤其是p，p‘-DDE)和早在60年前沉积的多氯联苯。相关分析将揭示年龄和生物有效性之间的关系，并阐明沉积物性质的影响。老化引起的生物利用度变化将被纳入营养食物链模型，以改进对生态受体和人类危害的估计。黑碳吸附剂(例如，活性碳、木炭、生物炭)越来越多地被用于修复，因为它们可以立即固定土壤或沉积物中的HOC。我们将进一步进行长期的实验室培养实验，以了解这种修改对污染物老化或永久隔离的影响。通过这个项目，我们将全面了解老化效应及其在调节污染物生物有效性方面的作用，并抓住机会应用它们，以实现更好的风险评估和缓解。

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.