Prediction of soil copper phytotoxicity to barley root elongation by an EDTA extraction method

Dose-response (toxicity) relationships explain how the response changes with exposure doses. However, the results of tests or observations are commonly based on total concentrations of contaminants in environments, not the exposure dose that causes toxicity. In the present study, the copper (Cu) phytotoxicity to barley root elongation was studied in 17 representative Chinese soils. Also, the EDTA-extractable Cu concentration was used to evaluate the extractability of Cu in soils. The results showed that the concentrations of EDTA-extractable Cu accounted for 89.6-91.2 % of total added Cu in soils and that soil pH, organic carbon content (OC) and cation exchange capacity (CEC) could explain over 85 % of the variance in Cu phytotoxicity thresholds based on EDTA-extractable concentration. The integrated relationship of EDTA-extractable Cu doses, toxicity, and soil properties was firstly derived quantitatively. The EDTA-extractable Cu plus soil properties can explain more than 90 % of the variance in the toxicity response of barley root elongation. The new integrated model based on dose-toxicity-soil properties will provide an approach for risk assessment of contaminated soils with different Cu sources to avoid the overestimation of the risk based on total Cu concentrations in soils, and to develop a reasonable remediation strategy for Cu contaminated soils.