The accurate assessment of bioavailability for copper in biosolids after its long-term application in soil is one of the key questions regarding its eco-environmental risk assessment and modifying of current soil environmental quality threshold. A procedure for determining L and E-values of Cu using ⁶⁵Cu isotopic dilution technology has been successfully developed and applied using rye grass and earthworms, the effect of pH on the L and E-values of Cu in the soils was also investigated in this study. The results indicated that the L-values determined with rye grass were nearly equal to E-values measured in soils and a good convergence of L- and E-values was observed (regression R²＝0.98), the percentage of L-values determined with ryegrass plants of different pH treatments ranged from 15.9% to 21.6% and the measured L and E-values of Cu increased with the decreasing pH in soils|however, the L-values determined with earthworms were generally less than the E-values measured in the soils and the earthworms gut which indicating that the activities of worms increase the exchangeable pool of Cu in soil. The strong influence of soil pH on Cu bioavailability and toxicity found in this study indicated that control of soil pH is a critical factor in minimising the environmental risk of Cu from soil to food chain and ecosystem health.

Key words: ⁶⁵Cu, isotopic dilution technology, E-value, L-value, bioavailability