College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, PR China.
J Environ Manage. 2018 Apr 15;212:115-120. doi: 10.1016/j.jenvman.2018.01.079. Epub 2018 Feb 8.
The fate of hydrophobic organic contaminants (HOCs) in soil-earthworm systems is an important foundation for soil pollution risk assessment and pollution control. Equilibrium partitioning is considered to be the main mechanism by which HOCs enter earthworms and, as such, a mechanistic model has been developed to estimate the earthworm-water partition coefficients (K). In the present study, the adsorption of phenanthrene (PHE) by earthworm tissue was investigated to evaluate the validity of the mechanistic models. Results revealed that K derived from the mechanistic model (346.90) was lower than that derived from the sorption experiments (410.76), indicating that apart from lipid fractions, other components in earthworms, such as protein fractions, might also play an important role in the adsorption of HOCs by earthworm. Besides, the difference between the mechanistic model for earthworm and partition-limited model used for plants are few, indicating that uptake and accumulation mechanisms of HOCs by earthworms and plants are highly consistent internally and are, essentially actually identical. It is also suggested that environmental fate of HOCs in soil-soil biota systems is dominated by their high hydrophobicity. Based on these conclusions, an improved mechanistic model for predicting the uptake of organic contaminants by earthworms has been proposed, which needs to be further evaluated. Furthermore, the feasibility of using vermiaccumulation in vermiremediation of soil contaminated by HOCs was discussed. The adsorption of PHE by earthworm sub-organism fractions (pre-clitellum, clitellum and post-clitellum) and tissue fractions (body wall and gut) were also investigated to interpret the distribution pattern of HOCs in earthworms. At the sub-organism level, the adsorption capacity of PHE by different regions of the earthworm followed the order: post-clitellum > clitellum > pre-clitellum, meaning the distribution of PHE along the earthworm contributes not only to their chemical composition but also to the life activity of earthworms such as circular system. At the tissue level, the gut showed greater affinity with PHE than that of the body wall indicating that the distribution of PHE is mainly due to chemical components at the tissue levels. These results might provide additional understanding of the fate of HOCs in soil-earthworm systems.
土壤-蚯蚓系统中疏水性有机污染物（HOCs）的命运是土壤污染风险评估和污染控制的重要基础。平衡分配被认为是 HOCs 进入蚯蚓的主要机制，因此，已经开发了一种机制模型来估计蚯蚓-水分配系数（K）。在本研究中，通过研究菲（PHE）在蚯蚓组织中的吸附来评估机制模型的有效性。结果表明，从机制模型得出的 K（346.90）低于从吸附实验得出的 K（410.76），表明除了脂质部分外，蚯蚓中的其他成分，如蛋白质部分，也可能在 HOCs 的吸附中发挥重要作用。此外，蚯蚓的机制模型与用于植物的分配限制模型之间的差异很小，这表明 HOCs 被蚯蚓和植物吸收和积累的机制在内部高度一致，本质上实际上是相同的。这也表明，HOCs 在土壤-土壤生物群系系统中的环境命运主要由其高疏水性决定。基于这些结论，提出了一种改进的预测蚯蚓吸收有机污染物的机制模型，该模型需要进一步评估。此外，还讨论了利用蚯蚓在 HOCs 污染土壤中的积累来进行生物修复的可行性。还研究了 PHE 在蚯蚓亚生物体部分（前生殖带、生殖带和后生殖带）和组织部分（体壁和肠道）中的吸附，以解释 HOCs 在蚯蚓中的分布模式。在亚生物体水平上，不同区域的蚯蚓对 PHE 的吸附能力依次为：后生殖带>生殖带>前生殖带，这意味着 PHE 在蚯蚓中的分布不仅与其化学成分有关，还与蚯蚓的循环系统等生命活动有关。在组织水平上，肠道对 PHE 的亲和力大于体壁，表明 PHE 的分布主要是由于组织水平上的化学组成。这些结果可能为更好地了解 HOCs 在土壤-蚯蚓系统中的命运提供了更多的认识。
