Effects of single and combined exposures to copper and benzotriazole on Eisenia fetida

- Survey of the behavioral toxicity and acute toxicity of BTR contamination in Eisenia fetida.
- Antagonistic effects of combined BTR and Cu exposure on earthworms are demonstrated.
- BTR can increase the solid-liquid distribution coefficient of Cu.
- BTR results in reduced earthworm mortality due to the decrease of the Cu2+ activities in soil solution.

Benzotriazole (BTR), an emerging class of environmental pollutant, is widely used in industrial applications and household dishwashing agents. Despite the reported toxicity of BTR to aquatic organisms, little is known about its effects on terrestrial invertebrates. Copper (Cu) accumulates in agricultural soils receiving urban waste products, fertilizers, fungicides, and urban sewage. In this study, two different types of bioassays (acute toxicity test and behavioral toxicity test) were performed to evaluate the toxicity of Cu and BTR, both singly and together, on the earthworm (Eisenia fetida) in artificial soil. The results of avoidance behaviour tests showed that the EC50,48 h values for Cu and BTR were 1.47 and 0.46 mmol kg−1, respectively. The results of the acute toxicity tests showed that the LC50,7 d and LC50,14 d of Cu in earthworms were 9.19 and 5.28 mmol kg−1, respectively, and the LC50,7 d and LC50,14 d of BTR were 2.43 and 1.76 mmol kg−1, respectively. Toxicity analysis demonstrated that the binary BTR and Cu mixture had predominantly antagonistic effects on the avoidance behaviour and survival of earthworms. The Cu2+ activities and mortality of earthworms decreased significantly with increasing concentrations of BTR, while the solid-liquid distribution coefficient of Cu increased. These results indicated that the presence of BTR can reduce the toxicity as well as the bioavailability of Cu in soil with both BTR and Cu.

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