Persistence of trifluralin in soil of oilseed rape fields in Western Greece

The persistence of trifluralin, a herbicide exhibiting persistent organic pollutant properties, was investigated in a clay loam (CL) type soil under conventional tillage of oilseed rape and in bare soil. Trifluralin residues were determined with high performance liquid chromatography (HPLC) with diode array detection (DAD) after extraction with acetonitrile using sonication. Trifluralin dissipation was followed for a time period of 150 days and it was characterised by a relative fast initial loss followed by slow dissipation. More rapid loss within the plots of conventional cultivation in comparison to bare soil was observed. The half-life of trifluralin calculated from first-order kinetics dissipation ranged from 53.3 to 56.8 days in the plots with oilseed rape while in bare soil it ranged from 67.9 to 71.4 days. One month after application a considerable loss of about 30% was observed in all fields. Two months later a loss of 40% was observed in bare soil and 60% in the plots cultivated with oilseed rape, indicating the role of crop in the dissipation of trifluralin. Sixteen to 23 per cent of the initial applied trifluralin still remained in soil 150 days after application.