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Behaviour of metamitron and hydroxy-chlorothalonil in low-humic sandy soils
Authors:Leo J T van der Pas  Arriënne M Matser  Jos J T I Boesten  Minze Leistra
Abstract:The behaviour of the herbicide metamitron and of the main transformation product, hydroxy-chlorothalonil (HTI), of the fungicide chlorothalonil was studied to assess the risk of leaching from low-humic sandy soil. The adsorption of metamitron corresponded to a Kom value of about 60 dm3 kg?1 (moderate adsorption). The half-life of metamitron in soil at 15 °C was only three days, presumably due to adaptation of the micro-organisms. In the autumn, the residue of metamitron in the soil profiles corresponded to less than 1% of the cumulative dosage. The half-life of chlorothalonil at 15 °C was about 12 days and about 45% of it was transformed to HTI. The adsorption of HTI to the soils corresponded to a Kom value of 260 dm3 kg?1. The incubation study (15 °C) showed the transformation of HTI in the soils to be very slow. The amounts of HTI remaining in the soil profiles in the autumn corresponded to 4 and 16% of the cumulative dosage of chlorothalonil. In winter, the HTI residue decreased by 40% relative to the autumn level. Occasionally, HTI could be detected in the upper ground-water level (at a depth of about 1 m), at an average concentration of 0.1 to 0.2 µg dm?3. © 1999 Society of Chemical Industry
Keywords:herbicide  pesticide  chlorothalonil  adsorption  transformation  leaching  ground-water  chemical analysis
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