土壤中多氯联苯的生物有效性及其影响机制研究

摘要

多氯联苯(PCBs)属于环境中广泛存在的持久性有机污染物(POPs),威胁生态系统安全与人体健康.为评价典型土壤中PCBs的生态风险,揭示其生物有效性以及影响生物有效性的分子机制将具有重要科学意义.本文以赤子爱胜蚓(Eisenia fetida)为土壤模式生物,模拟土壤中6种典型PCBs化合物(PCB-18、PCB-20、PCB-28、PCB-101、PCB-105、PCB-114)的富集动力学过程,并分析了蚯蚓吸收累积对土壤中PCBs总量的影响.结果表明,对于PCB-18、PCB-20和PCB-28,蚯蚓富集15天能够达到动力学过程的近平衡状态,而PCB-101、PCB-105和PCB-114则在30天达到近平衡状态,这可能是由于分子体积增大致使PCBs自由穿越生物膜并为生物体有机脂相富集的过程受到一定程度的限制,吸收速率变慢.PCBs生物有效性与典型分子性质(α、Kow)之间高度线性相关,从微观层面上揭示了影响生物有效性的分子机制,进一步表明PCBs分子体积、分子极化率及其疏水作用是影响生物有效性的主要因子,为典型土壤中PCBs污染物的生态风险预测与评价提供科学依据.%As an important group of persistent organic pollutants (POPs),polychlorinated biphenyls (PCBs) are ubiquitously detected in the environment and greatly threaten the eco-systematic security and human health.To evaluate the risks of PCBs in typical soil matrices,it is of significance to characterize the bioavailability and the relevant molecular mechanism of PCBs.In this paper,Eiseniafetida was used to simulate the accumulation kinetics of six representative PCB congeners,i.e.PCB-18,PCB-20,PCB-28,PCB-101,PCB-105 and PCB-114 in soil,and the effects of earthworm accumulation on the total amount of PCBs in soil was also analyzed.The results showed that 15 d was enough for PCB-18,PCB-20 and PCB-28 congeners to access the near-equilibrium state of whole accumulation kinetics process,while the demanded time was about 30 d for PCB-101,PCB-105 and PCB-114 congeners.The extension of equilibrium time of PCBs with higher chlorination may be attributed to the larger molecular volume of them,so that the free transfer throuth membrane and lipid accumulation was limited,and accordingly the velocity of uptakes decreased.The high linear correlation between the bioavailability and typical molecular properties (a,Kow) of PCBs implicated the influential molecular mechanism on bioavailability from the microcosmic aspects.The molecular volume,polarizability and corresponding hydrophobic interaction were further indicated to be the main effective factors.The study would provide scientific guidelines for the ecological risk prediction and assessment of PCBs in soil.