溴代阻燃剂在高泥沙河流中分布特征及吸附解吸机制研究

Hexabromocyclododecanes (HBCDs) are one kind of widely used, and one of the most representative brominated flame retardants (BFRs). HBCDs are ubiquitous organic contaminants which are characteristic with persistence in the environment, long-range transport, and high toxicity to organisms, drawing extensive attention in the international community. However, traditional adsorption experiments adopted to explore the adsorption and desorption behaviors of HBCDs are quiet impotent for revealing the adsorption-desorption mechanism and micro-migration mechanism of HBCDs in complex river system, especially in the high sediment river. In this study, the downstream of Weihe River (high sediment) was chosen as the research area and HBCDs were selected as the target contaminants. Through the analysis of water samples, suspended particulate matter and sediments samples, the occurrence, temporal and spatial distribution characteristics of HBCDs in high sediment river will be prospectively revealed. Based on the results of adsorption experiment, combining with FT-IR and μ-XRF microstructure characterization by using synchrotron radiation (SR) as the light source, the adsorption-desorption process of HBCDs on suspended particulate matter and sediment will be studied, exploring the adsorption-desorption mechanism and isomer selective enrichment mechanism of HBCDs in suspended particulate matter and sediment. The outcomes of this project are of scientific significance for deeply understanding the migration, transformation and final destiny of HBCDs in the complex river system, and will potentially supply theory guideline for the water quality risk assessment.

六溴环十二烷(HBCDs)是一类广泛应用、最具代表性的溴代阻燃剂之一，普遍存在于各类环境介质，具有环境持久性、生物毒性和长距离迁移性，受到了研究者的高度关注。目前对水体中HBCDs吸附解吸的研究主要依赖传统吸附实验方法，难以揭示复杂高泥沙河流中HBCDs在不同介质中的吸附解吸机制。本课题拟以渭河下游(高泥沙)为研究区，以HBCDs为目标物，通过水样、悬浮颗粒物、沉积物样品分析，揭示高泥沙河流中HBCDs赋存状态和时空分布特征。基于宏观吸附实验，结合同步辐射(SR)为光源的FT-IR与μ-XRF微观结构表征，研究悬浮颗粒物、沉积物中HBCDs吸附解吸过程，深入探索HBCDs在悬浮颗粒物和沉积物中的吸附解吸机制及异构体选择性富集机制。本课题的完成对于深刻解析复杂河流水体中HBCDs的迁移转化及归趋具有重要科学意义，为水质安全风险评价提供理论依据。

项目以渭河沉积物对HBCDs的阻滞作用为研究对象，在调研HBCDs赋存规律的基础上，研究了沉积物对HBCDs的吸附规律，分析了腐殖酸、离子强度及pH变化对吸附的影响；通过扫描电镜及SR-FTIR手段表征探讨了吸附机理，获得以下主要结论：.1. 研究区沉积物中HBCDs的检出率为91.2%，浓度范围分别为nd-4.04 ng/g，残留量空间差异较大，在中心城市附近及HBCDs含量较高，说明点源污染是渭河HBCDs的主要来源。渭水沉积物中HBCDs含量整体处于低生态风险水平。.2. 渭河沉积物中HBCDs中以α-HBCD的含量最高，其次是γ-HBCD，β-HBCD含量最低。这与商品HBCDs的组成差异较大，其主要原因是在β-HBCD和γ-HBCD能够通过生物转化作用转化为α-HBCD，且β-HBCD和γ-HBCD更易被生物降解，α-HBCD的半衰期更长。.3. 沉积物中HBCDs的吸附是一个快速吸附过程，为自发吸热反应，以物理吸附为主。HBCDs的吸附随pH值和腐殖酸浓度的增大先增加后降低，分别在pH=8及腐殖酸浓度25mg/L时吸附量达到最大；离子强度的增大对HBCDs的吸附有抑制作用。.4. 运用SEM及SR-FTIR对沉积物中HBCDs的吸附进行了表征，进一步说明HCBDs在沉积物中的吸附是以物理吸附为主的过程。