Predicting copper toxicity to different earthworm species using a multicomponent Freundlich model.

Area of Science:

• Environmental Toxicology
• Soil Science
• Ecotoxicology

Background:

• Copper (Cu) toxicity to soil invertebrates varies significantly across different soil types.
• Predicting Cu toxicity requires understanding bioavailability, influenced by soil properties and water chemistry.
• Existing models often struggle to account for the complex interactions affecting Cu toxicity in diverse soil environments.

Purpose of the Study:

• To develop robust bioavailability models for predicting Cu toxicity in earthworms (Lumbricus rubellus, Aporrectodea longa, Eisenia fetida).
• To identify key soil porewater factors influencing Cu toxicity and establish their relationship with toxicity endpoints.
• To assess the applicability of developed models for different earthworm species and other soil organisms.

Main Methods:

• Utilized a multicomponent Freundlich model to link Cu toxicity (LC50s) to free Cu(2+) activity and protective cations in soil porewater.
• Investigated the influence of soil properties, particularly pH and various cations (K+, Ca2+, Na+, Mg2+), on Cu toxicity.
• Validated the predictive models using external datasets, including data from other soil organisms and endpoints.

Main Results:

• LC50s of Cu varied substantially between soils and species, with Eisenia fetida being the least sensitive.
• Soil pH was identified as a significant protective factor against Cu toxicity, while other cations showed no significant effect.
• The Freundlich-type model incorporating free Cu(2+) activity and pH explained high percentages of variation in Cu toxicity (84-96%) across species.

Conclusions:

• Developed bioavailability models accurately predict Cu toxicity in earthworms based on free Cu(2+) activity and soil pH.
• The models demonstrate excellent predictive power and can be extrapolated to other earthworm species.
• The Freundlich-type model offers a promising tool for predicting toxicity in various soil invertebrates and plants, enhancing ecological risk assessment.