沉积物砷在底栖动物肠道中的生物地球化学过程及生物有效性评价方法研究

Most of the estuarine sediments in China have been contaminated by arsenic to different degrees. The speciation and geochemical processes of arsenic affect its toxicity greatly to benthic organisms. This proposed research will use modern structural analysis methods to determine the speciation of arsenic in the sediment before and after it is ingested by the benthic animals. We will focus on the adsorption, desorption, release and other behaviors of arsenic at the sediment-gut fluid interface to explore the geochemical processes of sedimentary arsenic in the gut of benthic animals. We will further examine the impacts of environmental and biotic factors in the gut on this process. After understanding the key constituent of gut fluid responding for the release of arsenic from sediment during digestive process, we will explore other optional parameters of the in vitro extraction method to evaluate the bioavailability of sediment-associated arsenic to benthic animals. This novel marriage of physiology with modern structural analysis methods in geochemistry will help better understand the biogeochemical cycle of arsenic in the aquatic ecosystem. The results of this proposal have the potential to provide a reliable in vitro extraction method for evaluating the bioavailability of arsenic in estuarine sediments.

我国各海湾河口的沉积物均受到不同程度的砷污染。砷在沉积物中的赋存形态及生物地球化学过程极大的影响着砷对水生生态系统的毒害效应。本项目拟以锦州湾沉积物及典型底栖动物为研究对象，应用同步辐射装置等现代结构分析手段考察沉积物砷被底栖动物摄入前后的赋存形态；结合体外实验与生物实验，从简单至复杂体系逐步深入研究砷在沉积物－肠液界面的吸附、解吸、释放等地球化学过程机理，重点考察肠道环境因素以及生物因素的影响；明确肠液中对砷的释放起到关键性作用的组分，确定体外浸提法评价沉积物砷的生物有效性的合适条件。项目的预期研究目标为，阐明沉积物砷在底栖动物肠道内的地球化学过程的微观机理、确定底栖动物的摄食行为对沉积物砷的赋存形态的影响、初步建立沉积物砷在底栖动物肠道内的生物有效性的体外评价方法。项目的成功实施对于研究与评价海湾河口沉积物砷的环境归宿及生物有效性具有重要的理论和实际意义。

本项目以锦州湾沉积物及典型底栖动物方格星虫（Sipunculus nudus）为研究对象，通过体外实验的方式，从简单至复杂体系逐步深入的研究了砷在沉积物-肠液体系中的吸附、解吸、释放过程及机理，明确了肠液中对砷的释放起关键性作用的组分，初步运用体外浸提法对沉积物中金属的生物有效性进行了评价。.研究主要发现：① 表面活性组分不仅对于沉积物中砷具有较强的释放作用，还可以显著的促进溶解性有机组分（蛋白质和氨基酸）对于砷的释放；② 与大分子的溶解性肠液蛋白相比，肠液小分子组分（包括自由态氨基酸和表面活性组分）对于砷的释放具有更为重要的作用；③ 沉积物中的砷在肠道内的释放可能是络合与基质还原共同作用的结果。.上述研究结果进一步认清了砷的生物地球化学循环过程中的影响因素，对于研究与评价沉积物砷的生物有效性具有一定的理论和实际意义。