THE EFFECTS OF EDTA ON METAL SOLUBILIZATION IN RIVER SEDIMENT WATER SYSTEMS/

Ethylenediaminetetraacetic acid (EDTA), widely used in chelant formula tions for applications to sequester metal ions in solution, has been d etected in some environmental waters. Concern has arisen that EDTA, be cause of its high binding constants with metals, may solubilize metals from sediments in river systems. To address this issue, the effects o f EDTA on metal solubilization were examined in a river sediment/water system. Microcosms prepared with authentic Rouge River, Detroit, MI, sediment and water were amended with a range of EDTA concentrations an d shaken in the dark at 23 degrees C for 28 d. Metal concentrations we re determined by inductively coupled plasma-optical emission spectrosc opy (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS ). In the presence of EDTA, 28 d were required for equilibration of di ssolved metal species with sediments. Higher levels of trace metals we re solubilized by EDTA under oxidizing vs. reducing conditions. Statis tically determined (alpha = 0.05) no observed effects levels (NOELs) f or metal solubilization by EDTA were generated for the trace metals Ni , Co, Cu, Zn, Cd, Fe, and Pb. These NOELs were 0.4, 0.6, 1.0, 1.0, 3.0 , 3.0, and 8.0 mu M EDTA, respectively. On a stoichiometric basis, the se NOELs were at least fivefold higher than the background level of ED TA present in the river water sample used in this study, indicating th at EDTA did not contribute to trace metal solubilization in this syste m. These results suggest that environmental concentrations of EDTA typ ically found in river systems for which the subject river is represent ative, are unlikely to contribute to trace metal solubilization from s ediments.