二恶英类化合物在粘土矿物表面的天然形成机理

二恶英类化合物是毒性最大的一类有机污染物，传统理论认为二恶英是在污染过程中产生的，然而近些年的研究发现二恶英在环境中广泛存在，并呈现出天然形成的特征。我们过去的研究证明二恶英能在粘土矿物表面在常温、常压条件下形成，然而对这一过程分子机理的研究还不够深入，对反应中间产物的环境行为研究还基本处于空白。本项目计划应用多种微观光谱表征手段，结合宏观实验与理论计算，系统研究矿物表面特征、环境条件以及前导物分子的化学结构对土壤和大气颗粒物中二恶英类物质形成的影响以及反应中间产物的转化规律。加强二恶英类化合物天然形成机理的研究对合理解释二恶英在环境中分布和形态的不平衡性，准确评估环境容量、制订环境质量标准、生态风险评价以及开展相应的污染控制等具有重要的理论和实践指导意义。

Dioxin-like compouds are the most toxic contaminants in the environment. Traditionally, these chemicals are considered as the by-product generated from human activities. However, recent studies have reported high levels of dioxins in pristine soils and pre-industrial clay deposits, with a typical congener profile characterized by the predominance of octachlorodibenzodioxin and low levels of polychlorinated dibenzofurans, which does not match any known anthropogenic source. Our previous studies have provided the first direct evidence that dioxin can be formed on clay mineral surface under environmental relevant conditions. But at this stage, the underlying mechanism for natural formation of dioxin-like compounds needs further investigation, and the environmental fate of the reaction by-products, e.g. predioxin are still not clear. In this study, laboratory experiments, state-the-art molecular-scale techniques, and theoretical calculations will be combined to systematically investigate the effect of mineral surface properties, environmental conditions and chemical structure of precursor molecules on natural formation of dioxin-like compounds on soil mineral surface and atmospheric particles. The objective of the proposed research is to rationalize the unique dioxin profiles found in natural system, and this study will be important for environmental risk assessment, establishment of environmental standard and prevention of environmental pollution.