污水补给河流沉积物有机质对取代多环芳烃（SPAHs）转化和扩散的驱动机理

Substituted polycyclic aromatic hydrocarbons (SPAHs) could cause directly genetic mutation comparing to their corresponding parent PAHs. However, little is known about their occurrence, behavior, source and fate of SPAHs in the aquatic environment, mainly due to the complexity in oxygen consumption, organic matter mineralization, and the production of SPAHs from the complex-polluted riverine sediments. Financially supported by the previous NSFC funding (21547009), a new extraction device without further purification was invented for PAHs and SPAHs, then using the Elite-17MS chromatographic column, the method for the simultaneously detection of 16 priority PAHs and 13 SPAHs was accomplished. We also designed a new passive sampler based on the equilibrium theory for the qualification the flux of free dissolved SPAHs from the sediment-water interface. In our field investigation, we found an unexpected high level of PAHs in anaerobic circumstance of the sediment-water interface, and the produced SPAHs tend to release to the overlying water. Then it was hypothesized that the dissolved organic carbon would increase with the anaerobic mineralization of organic matter, which would increase, in turn, the concentration of both PAHs and SPAHs, causing the release to the overlying water and poisoning the benthonic organism. This project aims to quantification the production and the flux of SPAHs by the combination of deuterium and 13C labeled PAHs, then further explore the coupling relationship of the organic matter mineralization pathway and the concentration of free dissolved PAHs and SPAHs, and study the change of toxicity and bioavailability of PAHs during the process of SPAHs production.

取代多环芳烃（SPAHs）较其母体具有更高的直接致突变性。污水补给河流沉积物中PAHs本底高，且有机质矿化和PAHs转化高度耦合，机理过程较为复杂。依托上一基金项目，本研究团队研发了沉积物/水SPAHs及其母体的快速且无需净化的前处理设备/方法，并发现污补河流沉积物-水界面的厌氧环境有利于SPAHs的生成，并向水中扩散。我们推测污补河流厌氧环境下，沉积物中有机质矿化产生的溶解性有机质将导致沉积物孔隙水自由溶解态PAHs和SPAHs累积而往上覆水释放，这一过程可能对底栖生物产生毒害效应。本项目利用氘代和13C稳定性同位素，揭示污补河流沉积物-水界面SPAHs生成过程、扩散通量及关键影响因素，探讨有机质降解途径和产物对孔隙水中自由溶解态SPAHs生成的影响，分析河流沉积物中存量PAHs转化过程的生物有效性变化及对底栖生物的毒害效应。项目研究成果将丰富沉积物中PAHs的环境地球化学行为认识。

取代多环芳烃（SPAHs）较其母体具有更高的直接致突变性。污水补给河流沉积物中PAHs本底高，且有机质矿化和PAHs转化高度耦合，机理过程较为复杂。我们推测污补河流厌氧环境下，沉积物中有机质矿化产生的溶解性有机质将导致沉积物孔隙水自由溶解态PAHs和SPAHs累积而往上覆水释放，这一过程可能对底栖生物产生毒害效应。本项目首先完成PAHs及取代物（SPAHs）在低密度聚乙烯（LDPE）膜吸附参数测定，确定了被动采样装置采样参数为40d，完成了海河流域子牙河水系平原段沉积物毒害污染物分布特征调查及风险评价，发现子牙河平原段表层沉积物ΣPAHs总含量在3372- 92949 μg/kg之间，平均含量达16626 μg/kg。其含量在空间上差异明显，上游水系中含量远高于下游河流，其生态风险等级总体较高，须引起重视；进而构建了基于FT-ICR-MS的沉积物孔隙水DOM分子组成分析方法并解析了不同溶氧梯度下的有机质组成，主要由木质素类、单宁类及脂肪族类构成的，并存在多肽及芳烃类物质。界面溶氧的变化会显著影响DOM的主体构成相同，导致CHOS类化合物构成的脂肪族有显著降低。随着DOM的矿化，其构成主体没有发生改变，主要由木质素类、单宁类及脂肪族类构成的，但碳水化合物类检出量增加。有机质厌氧降解显著提高了界面PAHs及SPAHs通量；最后选择底栖无脊椎动物摇蚊和青海弧菌，建立了沉积物和孔隙水的生物毒性测试方法，分析了不同溶氧梯度下界面PAHs及SPAHs通量，发现由于DOM厌氧降解，导致超过50%点位表现出高风险，特别是子牙河及沿海区域，表明DOM矿化改变了沉积物中SPAHs的生物可利用性，导致沉积物生物毒性增大。项目上述相关研究成果发表学术论文14篇，其中第一标注论文7篇。通过该项目的研究，丰富了污补河流沉积物中PAHs的环境地球化学行为认识。