Fate of ¹⁴C-Labeled Soybean and Corn Pesticides in Tropical Soils of Brazil under Laboratory Conditions

Abstract

The dissipation rate of seven currently used soybean and corn pesticides in two tropical soils (Ustox and Psamments) of Brazil was studied in a laboratory incubation experiment. Dissipation half-lives of pesticides ranged between 2 (monocrotofos) and 90 days (endosulfan-beta). The contrasting clay contents of the studied tropical soils (130 versus 470 g of clay kg(-1) of soil) did not influence the dissipation dynamics of pesticides substantially. Mineralization to CO(2) was high [up to 78% of the applied radioactivity (AR)] for the studied organophosphorus compounds and deltamethrin, which also formed considerable amounts of bound residues (>20% of AR) during the 80 days of incubation. The highest portion of nonextractable residues was found for alachlor and simazine (55-60% of AR). In contrast, the nonpolar trifluralin and endosulfan formed only small amounts of bound residues (mostly <20% of AR) but showed the highest dissipation half-lives (>14 days) in the studied soils, also due to a low mineralization rate. When endosulfan-sulfate, as the main metabolite of endosulfan, was considered, the half-life time of endosulfan compounds (sum of -alpha, -beta, and -sulfate) was enhanced to >160 days in both soils. In comparison with the laboratory experiments, dissipation half-life times of chlorpyrifos, endosulfan-alpha, and trifluralin were shortened by a factor of 10-30 in field trials with the same soils, which was related to the volatilization potential of pesticides from soils.

Fate in the Environment and Long-Range Atmospheric Transport of the Organophosphorus Insecticide, Chlorpyrifos and Its Oxon

“…The DT 50dis was reported to range from <2 to 120, with mean and geometric means of 32 and 22 d, respectively (SI Table 3); most values were in the range of 7-30 d (Table 6). Comparison of rates of dissipation of CPY from soils from Brazil under laboratory conditions suggested a tenfold greater rate of dissipation in the field than in the laboratory (Laabs et al 2002).…”

Quaternary ammonium compounds in soil: implications for antibiotic resistance development

“…The remaining part may be reversibly sequestered in soil if not even forming irreversibly bound residues, as, e.g. shown for antibiotics (Förster et al 2008;Zarfl et al 2009) and a range of pesticides (Calderbank 1989;Laabs et al 2002).…”

Implications of differences between temperate and tropical freshwater ecosystems for the ecological risk assessment of pesticides

“…2); (2) inclusion of pesticide residues adsorbed to (high concentrations of) suspended matter, i.e., algae and other particles, in combination with low organic content of the sediment and hence a smaller ''disappearance'' to this compartment (Lahr et al 2000;Daam et al 2008); (3) differences in prevailing pH regime (Zulkifli et al 1983;Lahr et al 2000;Mehetre et al 2003); (4) influence of dimensions of the (model) ecosystem, e.g., depth (Laabs et al 2007;Daam et al 2008). Although Laabs et al (2007) did not observe a faster dissipation of the pesticides mentioned above in the tropical aqueous environment, Laabs et al (2002) demonstrated substantial fate differences between tropical and temperate soils. This finding was indicated to be possibly due to greater temperature differences in soils than in aquatic environments and/or caused by a more enhanced volatilization of pesticides from soils than from water surfaces (Laabs et al 2007).…”