DEGRADATION OF THE HERBICIDE MECOPROP IN AN AEROBIC AQUIFER DETERMINED BY LABORATORY BATCH STUDIES

The potential of a shallow aerobic aquifer to degrade the herbicide Mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) was evaluated in the laboratory using groundwater and sediment suspension batches. Mecoprop was added to the batches to obtain concentrations of 65, 140, 400 and 1400-mu-g/l. Mecoprop was degraded at 10-degrees-C at all concentration levels during the 200 days experimental period. Acclimation periods varied from 20 to 110 days. Initial degradation of approximately 50 % of the added Mecoprop was followed by a second lag period. In most batches, complete degradation was observed after the second lag period. The natural degradation potential for mecoprop varied among locations within a distance of few metres and was affected by different mecoprop concentrations. The observed stepwise degradation was supposedly due to different populations or different microbial mechanisms involved in the degradation of the two stereo-chemical forms of Mecoprop.