基于稳定同位素稀释法和固相微萃取研究水环境中微塑料结合态HOCs的生物有效性

Studies on the impacts of microplastics (MPs) on the bioavailability of high toxic hydrophobic organic compounds (HOCs) in aquatic environment are very important and significant to evaluate the environmental risks of MPs. Using stable isotope dilution method (stable-IDM) and negligible depletion solid-phase microextraction (nd-SPME) as cores and biouptake and toxic effects on aquatic organisms (especially fish) as main body, also considering the environmental relevance of MPs (types and concentrations, using standard methods to prepare MPs), we will investigate the effects of environmentally relevant primary microbeads (MPBs) and secondary microplastic fibres (MFs) on the bioavailability of HOCs. The following three aspects of research will be conducted. (I) Effects of MPs on the chemical availability of HOCs. Using nd-SMPE to determine freely dissolved concentrations (Cfree) of HOCs in MPs system and Cfree as indicator of chemical availability, effects of several parameters, such as properties, size and concentrations of MPs as well as environmental factors (dissolved organic matter, salty, pH), on the chemical availability of HOCs will be studied and the mechanisms will be elucidated. (II) Effects of MPs on the bioavailability of HOCs. Effects of exposure pathways (exposure via food, via water and sequence of exposure) and aging of MPs-HOCs on biouptake and depuration of HOCs in aquatic organisms will be investigated; basing on Cfree, biouptake and toxic effects of HOCs, as well as MPs distributions in biota, bioavailability mechanisms of MPs-associated HOCs will be investigated. (III) Quantification of bioavailability of MPs-associated HOCs. Stable-IDM will be developed for quantifying bioaccessibility of HOCs in MPs systems (exchangeable fraction of HOCs in MPs systems); bioavailability of MPs-associated HOCs will be quantified by combining stable-IDM with nd-SPME.

微塑料（MPs）对水环境中疏水性有机污染物（HOCs）的生物有效性的影响研究对科学评价MPs的环境风险至关重要。本项目以微耗损固相微萃取（nd-SPME）和稳定同位素稀释法（stable-IDM）为核心，以水生物生物吸收和毒性效应为主体；考虑MPs的环境相关性，结合MPs制备技术，研究环境相关的一级微珠和二级微纤维对HOCs生物有效性的影响及机制，具体如下：（1）基于nd-SPME测定MPs体系中HOCs的自由溶解态浓度(Cfree)，以Cfree表征化学有效性；考察MPs性质、尺寸及环境因素等对HOCs化学有效性的影响及机制。（2）研究不同暴露方式（食物相、水相、顺序）和老化对HOCs生物吸收和排出的影响；基于Cfree、生物累积、毒性效应和MPs在生物体中的分布，研究MPs结合态HOCs的生物有效性及机制。（3）发展stable-IDM以定量表征MPs结合态HOCs的生物有效性。

微塑料（MPs）对水环境中高毒性疏水性有机污染物（HOCs）的生物有效性的影响研究对于科学评价MPs的水环境风险至关重要。本项目结合微耗损固相微萃取（nd-SPME）和稳定同位素稀释法（stable-IDM）以及水生物吸收，研究了环境相关的MPs（紫外光老化改性、DOM 共存）对HOCs生物有效性的影响及机制。主要研究成果如下：（1）化学有效性影响及机制: 结果表明，在自然环境中修饰MP将改变HOC的有效性.（a）UV改性的PE MPs表现出比原始MPs更高的表面含氧基团含量、比表面积和孔体积。PAHs与MPs作用疏水性起主要作用。与原始MP的结果相比，UV老化增强了PAHs在MP上的吸附（logK 3.71-4.98）。MP对PAHs的吸附主要基于分配机制，但是由于氢键和π-π相互作用，在UV-EMP中也可能发生吸附机理。（b）MPs、DOM和两者复合基质能降低极性HOCs的化学有效性，基质与极性HOCs以疏水相互作用和π-π、氢键、范德华力等多种作用力结合；纳米级PS降低极性HOCs化学有效性的能力最强，与纳米PS的比表面积大小正相关；复合基质降低极性HOCs化学有效性的能力较弱，因基质之间发生优先的交互作用导致吸附位点减少。（2）生物有有效性影响及机制：黄腐酸、纳米级PS或两者复合基质存在时，降低了HOCs的生物有效性。降低的程度复合基质 < 纳米级PS，且与纳米PS的比表面积大小正相关。生物累积因子的计算结果表明，自由溶解态浓度更真实反映HOCs的生物有效性。（3）MPs体系中稳定同位素稀释法的应用：成功建立了适用于PS溶液体系中极性HOCs的可交换结合态浓度的稳定同位素稀释法，结合态组分对卡马西平生物有效性的贡献可忽略不计，预示着结合态分数的对生物有效性的贡献程度依赖于物质的理化性质。本研究将为真实水环境中MPs的生态环境风险评价提供了理论基础和技术支持。