Soil type-dependent effects of earthworm activity on antimony bioavailability in Chinese agricultural soils

With the acceleration of global industrialization, antimony (Sb) pollution poses an increasing threat to ecosystems and human health, and the issue of Sb contamination is gaining attention. In this study, the impact of earthworm activity on Sb bioavailability in various agricultural soils and the influencing factors were evaluated. Soil samples were collected from diverse regions in China and assessed for Sb bioavailability through chemical extractions and earthworm avoidance and growth tests. The primary objectives were to determine how earthworm activity affects Sb bioavailability and to understand the intrinsic influence of soil properties on earthworm behavior and growth. The results revealed that earthworm activity significantly reduced the pH in acidic and neutral soils, increasing Sb bioavailability, whereas alkaline and calcareous soils exhibited minimal changes in pH, leading to reduced or variable Sb mobility. Soil properties-particularly pH and organic matter-critically influenced earthworm behavior (e.g., avoidance responses) and growth inhibition. A clear interspecific difference in sensitivity to Sb contamination was detected, with the epigeic Eisenia fetida being more sensitive than the anecic Pheretima guillemi. These findings underscore the role of earthworms as "bioengineers" in modulating Sb environmental behavior through pH-driven processes. This study highlights the necessity of integrating soil-specific properties (e.g., pH and organic matter) and ecological differences among earthworm species to increase the accuracy of Sb risk assessments in contaminated agricultural environments.