ABSTRACT
The fate of the 3 formerly widely used herbicides 2,4,5-T, atrazine, and DNOC in a shallow anaerobic aquifer was investigated by use of diffusive emitters capable of releasing reasonably stable concentrations of each herbicide along with a tracer (HTO). Degradation of 2,4,5-T and atrazine could not be detected within a residence time of ~9 days. In contrast, DNOC was below detection limit after ~3.6 days showing rapid abiotic degradation. The degradation pathway is assumed to be reduction of nitro groups. In comparison, results from batch laboratory experiments revealed slow microbial degradation (half-life ~200 d) of 2,4,5-T in sediment taken from the upper part of the experiment depth. Atrazine was found to be persistent in the laboratory experiments also. DNOC was below detection limit after 50 d. The results demonstrate the ability of the system to detect rapid degradation, whereas detection of slow degradation requires identification of degradation products.
