Persistence of 14C-labeled atrazine and its residues in a field lysimeter soil after 22 years

Twenty-two years after the last application of ring-14C-labeled atrazine at customary rate (1.7 kg ha-1) on an agriculturally used outdoor lysimeter, atrazine is still detectable by means of accelerated solvent extraction and LC-MS/MS analysis. Extractions of the 0-10 cm soil layer yielded 60% of the residual 14C-activity. The extracts contained atrazine (1.0 μg kg-1) and 2-hydroxy-atrazine (42.5 μg kg-1). Extractions of the material of the lowest layer 55-60 cm consisting of fine gravel yielded 93% of residual 14C-activity, of which 3.4 μg kg-1 was detected as atrazine and 17.7 μg kg-1 was 2-hydroxy-atrazine. The detection of atrazine in the lowest layer was of almost four times higher mass than in the upper soil layer. These findings highlight the fact that atrazine is unexpectedly persistent in soil. The overall persistence of atrazine in the environment might represent a potential risk for successive groundwater contamination by leaching even after 22 years of environmental exposure. - Atrazine and its metabolite 2-hydroxy-atrazine are still present in soil after long-term aging.