No abstract

No abstract

No abstract

The metabolites of pesticides can contaminate groundwater and pose a risk to human health when this water is used for drinking. This paper reports the results of a laboratory study on aldicarb and its main metabolites, aldicarb sulfone and aldicarb sulfoxide. Aldicarb and its metabolites showed Koc values (6-31) which were lower than that of atrazine (55), indicating that they are very mobile in soil. They are less persistent than atrazine (DT50 = 25 days), with DT50 values from less than 1 day and up to 12 days. Aldicarb behaved as a non-leacher, whereas its metabolites clearly showed the characteristics of leachers. Aged residue leaching experiments showed that aldicarb can occur at high concentrations in the leachate, together with its two metabolites. The leachate composition depends on the incubation time of the parent compound. Aldicarb and its metabolites can form various mixtures in groundwater on the basis of the time elapsing between the application of the insecticide and the first significant rainfall. This study confirms the characteristics of contaminants of aldicarb and especially its metabolites, as reported in the literature.

Degradation studies in soil of the insecticides aldicarb and carbofuran and their metabolites (aldicarb sulfoxide, aldicarb sulfone; 3-ketocarbofuran and 3-hydroxycarbofuran) were carried out using laboratory systems under controlled conditions (temperature, water content, light). The insecticides were added to soil samples and subsamples of the soil were analyzed at different times to assess both the bacterial abundance and the concentration of the different chemicals. The epifluorescence direct count method was applied to the subsamples to estimate microorganism numbers (N=g soil). Untreated samples of soil were used as controls for evaluating the effects of the application of the insecticides on microbial abundance. Subsamples treated with the pesticides were analyzed using HPLC and the DT 50 s of the different compounds studied were calculated.The DT 50 values show that neither the parent compounds nor the transformation products have a high persistence in soil and there is a general increase in the concentration of microorganisms as the pesticides diminish.