Development of Stable Isotope Based Methods to Predict Bioavailability of Hydroph

说明（由申请者提供）：人类接触沉积物携带的污染物与沉积物中的化学品浓度没有直接关系，而是受生物可利用浓度或生物利用度的控制。补救措施，如疏浚，砂盖，吸附剂修正，甚至监测自然恢复（MNR）都可能影响沉积物污染物的生物利用度不同于散装沉积物化学浓度。特别是，生物利用度是更好地评估人类通过食用受污染地区的鱼类而接触到诸如滴滴涕、多氯联苯、多环芳烃和二恶英等疏水性有机污染物的关键。然而，目前用于确定沉积物HOC生物利用度的方法受到特定方法的限制。用于估计生物可利用性的部分提取技术总是受到所选提取剂类型和提取条件的影响。被动采样器，包括固相微萃取（SPME），必须在可能需要数月才能达到的平衡条件下使用。在这个项目中，我们利用稳定同位素标记的HOC化合物和GC-MS系统的广泛可用性，在两个新的应用，旨在大大提高生物利用度测量的效率和准确性。第一种方法使用同位素交换（或稀释）的概念，类似于对微量元素所做的，以获得可交换浓度作为生物可及浓度的近似值。事实上，大多数HOC是高度稳定的，这使它们具有保守的品质，因此非常适合这种应用。在第二种方法中，我们将稳定的同位素标记的HOCs与SPME通过使用标记的HOCs作为性能参考化合物，使SPME可以在非平衡条件下使用短的采样时间。同位素交换法可用于非原位评价，而稳定同位素- SPME法可用于非原位和原位测量。我们将开展系统的研究来证明基本假设，开发和优化使用加标沉积物的方法，并通过使用常见鱼类猎物的广泛生物累积测定来验证方法（多毛类蠕虫）和沉积物喂养的鱼（加州大比目鱼），然后在洛杉矶海岸外的帕洛斯弗迪斯大陆架超级基金现场应用非原位和原位测量DDTs和PCBs的生物利用度的方法洛杉矶已经进行了试点修复试验，并计划在2012年进行砂盖。在本项目结束时，我们希望产生一系列经过严格测试的方法，这些方法可以很容易地用于沉积物修复场地的非原位或原位监测，以评估修复作业的有效性并预测人类暴露潜力的变化。 公共卫生相关性：人类接触沉积物携带的污染物，如滴滴涕、多氯联苯、多环芳烃和二恶英，与大量沉积物中的化学品浓度没有直接关系，而是受生物利用度的控制。在这个项目中，我们利用稳定同位素标记的HOC化合物和GC-MS系统的广泛可用性，在两个新的应用，旨在大大提高生物利用度测量的效率和准确性。这些方法可以很容易地用于沉积物补救地点的非现场或现场监测，以评估补救行动的有效性，并更好地预测人类接触可能性的变化。

DESCRIPTION (provided by applicant): Human exposure to sediment-borne contaminants is not directly related to chemical concentrations in the bulk sediment, but is instead controlled by the bioavailable concentration or bioavailability. Remediation practices, such as dredging, sand capping, sorbent amendment, and even monitored natural recovery (MNR) may all affect the bioavailability of sediment contaminants differently than the bulk sediment chemical concentration. In particular, bioavailability is a key to better assessing human exposure to hydrophobic organic contaminants (HOCs) such as DDT, PCBs, PAHs and dioxins through consumption of fish from contaminated areas. However, current methods for determining sediment HOC bioavailability suffer from method-specific limitations. Partial extraction techniques to estimate bioaccessibility are invariably influenced by types of extractants and extraction conditions selected. Passive samplers, including solid phase microextraction (SPME), must be used under equilibrium conditions that may take months to reach. In this project we exploit the wide availability of stable isotope labeled HOC compounds and GC-MS systems in two novel applications aiming to greatly improve the efficiency and accuracy of bioavailability measurement. The first approach uses the concept of isotope exchange (or dilution), similar to what has been done for trace elements, to derive the exchangeable concentration as an approximation of bioaccessible concentration. The fact that most HOCs are highly stable lends them the quality of being conservative and thus ideal for such an application. In the second approach, we incorporate stable isotope labeled HOCs with SPME by using the labeled HOCs as performance reference compounds so that SPME may be used under non-equilibrium conditions with short sampling time. The isotope exchange approach may be applied to ex situ assessment while the stable isotope- SPME method may be used for both ex situ and in situ measurements. We will carry out systematic studies to prove the underlying assumptions, develop and optimize the methods using spiked sediments, validate the methods through extensive bioaccumulation assays using a common fish prey (polychaete worm) and a deposit-feeding fish (California halibut), and then apply the methods for ex situ and in situ measurement of bioavailability of DDTs and PCBs at the Palos Verdes Shelf Superfund site off the coast of Los Angeles that has undergone pilot remediation trials and is scheduled for sand capping in 2012. At the end of this project, we expect to produce a range of rigorously tested methods that may be easily adopted for ex situ or in situ monitoring of sediment remediation sites to evaluate the effectiveness of remediation operations and predict changes in human exposure potential. PUBLIC HEALTH RELEVANCE: Human exposure to sediment-borne contaminants such as DDT, PCBs, PAHs and dioxins is not directly related to chemical concentrations in the bulk sediment, but is instead controlled by bioavailability. In this project we exploit the wide availability of stable isotope labeled HOC compounds and GC-MS systems in two novel applications aiming to greatly improve the efficiency and accuracy of bioavailability measurement. These methods may be easily adopted for ex situ or in situ monitoring of sediment remediation sites to evaluate the effectiveness of remediation operations and better predict changes in human exposure potential.