Aging of methabenzthiazuron, imidacloprid, and N,N-dimethylsulfamide in silty soils and effects on sorption and dissipation

作者：Dalkmann Philipp^*; Menke Ulrich; Schaefer Dieter; Keppler Juergen; Paetzold Stefan

来源：Environmental Toxicology and Chemistry, 2012, 31(3): 556-565.

DOI：10.1002/etc.1734

• Kinetic sorption
• Time-dependent sorption
• Aged sorption
• Pesticide
• Soil heterogeneity

Differences in soil properties can influence the fate of plant protection agents in the environment. The present study aims to investigate the sorption behavior and related aging processes of imidacloprid (IMI; insecticide), methabenzthiazuron (MBT; herbicide), and N,N-dimethylsulfamide (DMSA; degradate of the fungicide tolylfluanid) in six soils of silty texture but otherwise varying properties. The sorption behavior of these 14C-labeled compounds exhibiting different physicochemical properties was characterized by applying a three-step sequential extraction procedure. After 119d, MBT revealed strongest sorption (K%26apos;tot 47.4200.4?L/kg), followed by IMI (K%26apos;tot 11.730.6?L/kg), and DMSA with K%26apos;tot close to zero. Aged sorption factors (AFs) were calculated to characterize aging processes over time exhibiting a 2.63.5-fold (IMI), a 1.84.5-fold (MBT), and no (DMSA) increase of sorbed amounts within 84d. Sorption and aging varied widely in the group of silty soils, which differed with respect to organic matter content, C/N-ratio, and microbial soil parameters. The time-dependent increase of adsorption of MBT and IMI was more pronounced in those soils that had a lower organic carbon and low microbial biomass content. Concomitantly, MBT and IMI degradation decelerated, presumably because of aged sorption at inner binding sites leading to a lower accessibility. In contrast, in the soils with a higher organic carbon content a strong initial (but later still reversible) sorption of MBT and IMI, occurring presumably at outer surface sites, reduced the extent of time-dependent diffusion toward inner binding sites. Environ. Toxicol. Chem. 2012;31:556565.

• 出版日期2012-3