Sorption of the herbicides alachlor, atrazine, dicamba, hexazinone, imazethapyr, metsulfuron‐methyl, nicosulfuron, simazine and sulfometuron‐methyl was characterized on six Brazilian soils, using the batch equilibration method. In general, weak acid herbicides (dicamba, imazethapyr, metsulfuron‐methyl, nicosulfuron and sulfometuron‐methyl) were the least sorbed, whereas weak bases such as triazines and nonionic herbicides (alachlor) were the most sorbed. TheKdvalues found showed a significant correlation with soil organic carbon content (OC) for all herbicides except imazethapyr and nicosulfuron.Kocvalues showed a smaller variation among soils thanKd. To estimate the leaching potential,Kocand the ground‐water ubiquity score (GUS) were used to calculate half‐lives (t1/2) that would rank these herbicides as leachers or non‐leachers. Comparison of calculated values to published values fort1/2demonstrated that sulfonylureas and hexazinone are leachers in all soils, alachlor is transitional, and atrazine, simazine and dicamba are leachers or transitional, depending on soil type. Results discussed in this paper provide background to prioritize herbicides or chemical groups that should be evaluated in field conditions with regard to their leaching potential to ground‐water in tropical soils.
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Oliveira et al. (2001) studied this question.
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