Affiliation: | a Department of Policy Analysis and Department of Environmental Science, National Environmental Research Institute, P.O. Box 358, DK-4000, Roskilde, Denmark b Office of Chemicals, Danish Environmental Protection Agency, Strandgade 29, DK-1401, Copenhagen-K, Denmark c Department of Chemistry and Microbiology, National Environmental Research Institute, DK-4000, Roskilde, Denmark d Department of Environment, Technology and Social Studies, Roskilde University, DK-4000, Roskilde, Denmark e Department of Atmospheric Chemistry, National Environmental Research Institute, DK-4000, Roskilde, Denmark f Department of Life Science and Chemistry, Roskilde University, DK-4000, Roskilde, Denmark |
Abstract: | The sorption of the pyrethroid, esfenvalerate, to the dissolved and/or dispersed fraction of eight different natural humic compounds has been investigated. The dissolved organic matters (DOMs) included in this study originate from ground water, soil pore water, and surface waters. Sorption was modelled at DOM concentration levels where equilibrium partitioning of esfenvalerate between DOM and the aqueous bulk phase prevails. The inherent characteristics of the eight different humic materials, quantified in the preceding paper by Thomsen et al. (2002, this issue (PII: S0045-6535(02)00335-1)), have been used as explanatory variables for modelling this equilibrium partitioning. Using a reverse QSAR approach based on by projection-into-latent-structure regression (PLS-R) inherent sorbent properties determining for the sorption affinity of esfenvalerate to DOM were analysed. For all humic substances a decrease in the DOM-normalised equilibrium-partitioning coefficient, KDOM, with increasing concentration of DOM was observed. Significant variations in KDOM values, as function of the inherent characteristics of the individual humic substances, were found at DOM concentrations of 75 and 100 ppm, respectively. The latter is a strong indication of variations in sorption mechanisms of esfenvalerate to DOM of varying inherent properties. Groupings in the principal property space quantifying DOMs may indicate that separate models are needed for quantifying the equilibrium partitioning to different classes of DOM. |