Absence of 14co2 evolution from 14C-labelled EDTA and DTPA and the sediment/water partition ratio

A freshwater sediment putatively contaminated with ethylenediamine tetraacetic acid (EDTA) and its metal complexes was used to examine the biodegradation and the sediment/water partition of 14C-labelled ethylenediamine tetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA). The Fe complexes were examined and experiments were carried out at 22°C in darkness. The substrates had partition coefficients (KOC) of 3.35 and 5.65 1 kg−1 organic carbon respectively, and there was no evidence for biodegradation of either substrate by the indigenous organisms in the absence of additional carbon or nitrogen substrates during incubation for 40d. It was concluded that (i) in this sample, aerobic microbial processes did not play a significant role in degrading either EDTA (Fe) or DTPA (Fe) to CO2 and (ii) on account of the limited extent to which these compounds partition into the sediment phase, anaerobic biodegradation would be of restricted significance. Experiments with 14C-labelled benzoate showed that concentrations of inorganic nutrients in the sediment were unlikely to limit biodegradation of EDTA or DTPA to 14CO2, and that sorption of benzoate and putatively EDTA and DTPA to bacteria in the sediment phase was minimal.