Toxic Effects of CO2 Leakage from Geological Storage on Earthworms

CO2 capture and storage (CCS) is currently recognized as an effective measure to reduce carbon dioxide emissions in the world. However, the CO2 stored underground has the risk of leakage because of various unstable factors, posing a threat to the soil environment and soil ecosystem. In this study, Eisenia fetida was selected as the research object. By simulating the effects of high concentration of CO2 on the morphology and physiological changes of earthworms, the toxic effects of high concentration of CO2 on the earthworms caused by CCS leakage were explored. The results showed that the high concentration of CO2 in the soil caused earthworms to have external morphological changes such as clitellum swelling, tail beading and tail breaking; skin and setae were damaged and epidermis was wrinkled. With the increase of CO2 concentration and the extension of exposure time, the mortality rate of earthworms increased continuously. The median lethal concentrations of 7 d and 14 d for high concentration CO2 soil were 26.39% and 17.78%, respectively, and the lysosomal membrane neutral red retention time (NRRT) of granulocytes decreased. Therefore, earthworms are expected to be used as indicators of CO2 leakage, and NRRT can be used as a sensitive biomarker for CO2 leakage.