Use of Chiral Tracers to Determine Cycling of POPs in Stream Ecosystems

CBET-0828699Lee，Cindy M.Clemson University使用手性示踪剂测定河流生态系统中POPs的循环尽管几十年来，许多持久性有机污染物(POPs)的制造和使用已经被禁止，如多氯联苯(PCbs)和二氯二苯基三氯乙烷(DDT)，但由于持续的身体负担被认为对人类健康有害，许多美国水生系统都有鱼类建议。环境科学家和工程师提出并研究了各种假说，如持续投入或无效的补救方法，但对持久性有机污染物在生态系统中的循环，特别是生物群的作用，仍缺乏充分的了解。使用手性持久性有机污染物为研究食物网提供了一种创新的技术。有19种手性多氯联苯同系物，这是由于围绕联苯键的有限旋转使它们不对称。生成的阿托异构体或对映体具有相同的化学和物理性质，如溶解度和挥发性，但在不对称环境中可能具有不同的反应速率。因此，生物转化可以导致一种对映体比另一种对映体更加丰富。由于技术的最新发展，这种浓缩可以用对映体分数(EF)通过层析来测量。我们建议利用多氯联苯的手性分析来更好地了解它们在溪流生态系统中通过食物网的移动。结合手性、同种特定和稳定的同位素分析将阐明重要的问题，如从受污染的沉积物转移到基础资源，如附生生物(生物膜)和腐烂的叶子，这些资源作为无脊椎动物的食物来源，而无脊椎动物反过来又是鱼类的猎物。我们给出的初步数据显示了手性分析的实用性。为了验证手性分析提供重要洞察力的工作假设，我们将在一条被多氯联苯(PCB)污染的河流中进行实地工作，并在三年内进行实验室研究。实地研究(始于第一年)包括对两年(2003-2004年)收集的样本进行手性和手性分析，并有针对性地收集一套全面的沉积物样本。实验室研究(于第二年开始)将是一项基于现场结果的受控喂养研究。该结果可应用于其他手性持久性有机污染物(例如。滴滴涕、氯丹、毒杀芬)以及许多新出现的令人关切的杀虫剂和药品。我们对持久性有机污染物从受污染的沉积物迁移到鱼类的各种途径的了解在很大程度上是不完整的，这是人类接触持久性有机污染物的主要途径。减少风险战略将受益于从这项工作中获得的基本知识。这些知识还将通过改善对复杂食物网的理解来推进生态学的基本概念。该项目将资助两名研究生。他们将从克莱姆森大学和环境保护局之间的合作中受益，这将扩大他们的研究机会视角。克莱姆森以招收和留住代表不足的群体的学生而闻名。外联活动将包括向参与超级基金和研究场地NRDA进程的公民团体介绍情况。一名中学教师将通过补充参与这项研究。

CBET- 0828699Lee, Cindy M.Clemson UniversityUse of Chiral Tracers to Determine Cycling of POPs in Stream EcosystemsAlthough the manufacture and use of many persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) have been banned for decades, many US aquatic systems have fish advisories due to continuing body burdens considered dangerous to human health. Environmental scientists and engineers have proposed and investigated various hypotheses such as continuing inputs or ineffective remediation methods, yet there is still an inadequate understanding of the cycling of POPs in ecosystems, especially the role of biota. Using POPs that are chiral offers an innovative technique for the studying food webs. There are 19 chiral PCBs congeners due to restricted rotation around the biphenyl bond that makes them asymmetric. The resulting atropisomers or enantiomers have the same chemical and physical properties such as solubility and volatility but can have different reaction rates in asymmetric environments. Therefore, biotransformation can result in one enantiomer enriched over the other. The enrichment can be measured as the enantiomeric fraction (EF) by chromatography due to recent developments in technology. We propose to exploit chiral analysis of PCBs to improve understanding of their movement through food webs in a stream ecosystem. The combination of chiral, congener specific and stable isotope analyses will elucidate important questions such as the transfer from contaminated sediment to basal resources such as periphyton (biofilm) and decaying leaves, which serve as food sources for invertebrates, which in turn are prey for fish. We present preliminary data that shows the utility of chiral analysis. To test the working hypothesis that chiral analysis provides significant insight we will conduct field work in a river contaminated with polychlorinated biphenyls (PCBs) and a laboratory study over a three year period. The field study (initiated in Year 1) consists of achiral and chiral analysis of extracts from samples collected over two years (2003-2004) and the targeted collection of a comprehensive set of sediment samples. The laboratory study (initiated in Year 2) will be a controlled feeding study based on the field results.The results can be applied to other POPS which are chiral (eg. DDT, chlordane, toxaphene) as well as many pesticides and pharmaceuticals that are of emerging concern. Our understanding is largely incomplete of the various pathways for POPs as they move from contaminated sediment to fish, which are a major pathway for human exposure to POPs. Risk reduction strategies would benefit from the fundamental knowledge gained from this work. The knowledge will also advance fundamental concepts in ecology through improved understanding of complex food webs. Two graduate students will be supported by the project. They will benefit from the collaboration between Clemson University and the EPA that will expand their perspective of research opportunities. Clemson has a reputation for recruiting and retaining students from under-represented groups. Outreach will include presentations to citizen groups involved in the Superfund and NRDA processes for the study site. A middle school teacher will participate in the research through a supplement.