Study on the Accumulation and Localization of Hg by Eisenia foetida

Mercury is highly toxic, and soil contamination with mercury may pose a significant threat to soil organisms, such as earthworms. Eisenia foetida exhibits the ability to bioaccumulate mercury. This study examined the bioaccumulation process and release patterns of mercury in earthworms exposed to varying concentrations (1, 2, 4, 8, 16, 24, 32, and 64 mg·kg^-1) of mercury. Samples were collected at intervals of 2, 4, 8, 16, 24, 32, 48, 64, and 96 days. The results show that, under mercury exposure concentrations of 1-8 mg·kg^-1, the bioaccumulation factor (enrichment coefficient) ranged from 1.69 to 2.95, with the highest concentration of 18.93 mg·kg^-1. At higher exposure levels (16-64 mg·kg^-1), the enrichment coefficient ranged from 5.21 to 7.62, with the maximum concentration reaching 476.33 mg·kg^-1. The rate of mercury accumulation in earthworms was rapid during the initial 0 to 8 days of the experiment, slowed thereafter, and stabilized after 90 days. The mercury primarily accumulated in the posterior segments of the earthworm body, specifically beyond the 25th node. Following the release phase in clean soil, the mercury content in the earthworms decreased over time and stabilized after 64 days. These findings offer valuable insights for developing safe and cost-effective methods for the remediation of mercury-contaminated soils, providing foundational data for the restoration of heavy metal-contaminated environments.