TEFLUTHRIN SORPTION TO MINERAL PARTICLES - ROLE OF PARTICLE ORGANIC COATINGS

The sorption of tefluthrin was studied on ''pure'' clay minerals and t hose that had been coated with aquatic humic substances over a mass pe rcent carbon range of 0.02 to 2.15. Tefluthrin sorption onto humic-coa ted minerals was significantly greater than on to the clean minerals a nd increased with increasing quantities of sorbed humic substances. Hu mic acid, the most aromatic coating, was the strongest sorbent, follow ed by fulvic acid, hydrophilic macromolecular acid and natural coating s on estuarine suspended particles. This shows the significant impact of humic coatings on the sorptive capacity of mineral particles. The s orption was linear, also consistent with the operation of a partition process. The partition coefficient normalised to organic carbon (K-oc) after deduction of the contribution from the clean mineral, ranged fr om 120000 to 770000 and was highest for the most aromatic humic acid f raction.