文摘
The sorption behavior of diuron, imidacloprid, and thiacloprid was investigated using 22 soils collectedin triplicate from temperate environments in Australia and tropical environments in Australia and thePhilippines. Within the temperate environment in Australia, the soils were selected from a range ofland uses. The average KOC values (L/kg) for imidacloprid were 326, 322, and 336; for thiacloprid,the values were 915, 743, and 842; and for diuron, the values were 579, 536, and 618 for the Ord(tropical), Mt. Lofty (temperate), and Philippines (tropical) soils, respectively. For all soils, the sorptioncoefficients decreased in the following order: thiacloprid > diuron > imidacloprid. There were nosignificant differences in sorption behavior between the tropical soils from the Philippines and thetemperate soils from Australia. Sorption was also not significantly related with soil characteristics,namely, organic carbon (OC) content, clay content, and pH, for any of the three chemicals studied.When the data were sorted into separate land uses, the sorption of all three chemicals was highlycorrelated (P < 0.001) with OC for the rice soils from the Philippines. Sorption coefficients for allthree chemicals were highly correlated with OC in temperate, native soils only when one extremevalue was removed. The relationships between sorption of all three chemicals and OC in temperate,pasture soils were best described by a polynomial. Sorption coefficients for imidacloprid and thiaclopriddetermined in the temperate pasture soils remained fairly consistent as the OC content increasedfrom 3.3 to 5.3%, indicating that, although the total OC in the pasture soils was increasing, thecomponent of OC involved with sorption of these two compounds may have been remaining constant.This study demonstrated that the origin of the soils (i.e., temperate vs tropical) had no significanteffect on the sorption behavior, but in some cases, land use significantly affected the sorption behaviorof the three pesticides studied. The impact of land use on the nature of soil OC will be furtherinvestigated by NMR analysis.Keywords: Pesticide fate and behavior; soil organic carbon; landuse; diuron; imidacloprid; thiacloprid