Earthworm Toxicity Test for the Monitoring Arsenic and Heavy Metal-Containing Mine Tailings

Earthworm toxicity tests were carried out to evaluate the toxicity of tailings from three abandoned mine sites in Korea. Chemical analysis was employed to check the feasibility of this test in determining remediation priorities. Mortality of earthworms was found in Nakdong and Myoungbong mine tailings and the highest mortality was detected in the Nakdong mine tailings, indicating that these tailings were highly contaminated. The average weight changes of earthworms varied significantly among the three mine tailings, and lowest observable-effect concentration (LOEC) values for Myoungbong and Nakdong were 20 and 2.5% of the tailings portion, respectively. We concluded that Nakdong mine tailings were the most toxic to earthworms, and that the Nakdong site needs remediation. The results of chemical analysis confirmed that Nakdong mine tailings were highly contaminated with arsenic (As) and heavy metals, and that Myoungbong tailings were less contaminated. A remediation priority was determined on the basis of both the chemical analysis and ecotoxicological test, and both analyses yielded the same remediation priority as represented by the order Nakdong, Myoungbong, and Duckum. Moreover, the relationship between As concentration and the average weight of earthworms was significant, indicating that the simple earthworm toxicity test could be used as a screening tool in determining remediation priority or evaluating risk assessment.