ADSORPTION, MOBILITY, AND FILTRATION OF METOLACHLOR IN CONTAINER MEDIA

Adsorption, mobility, and filtration ability of organic media toward m etolachlor were evaluated in a series of laboratory experiments, Exper imental variables included media type, metolachlor concentration, and equilibration time, Adsorption isotherms were determined by applying t he log form of the Freundlich equation, Mobility was evaluated using g lass columns filled with media, which were then surface spiked with me tolachlor and then leached daily for 10 consecutive days, Feat, pine b ark, combinations of these two media and a mixture of pine bark and sa nd adsorbed >90% of the C-14 metolachlor, Freundlich sorption coeffici ents were 10.9, 18.2, 13.4, 14.2, and 11.0 for pine bark, peat, 5 pine bark : 1 peat, 3 pine bark : 1 peat, and 5 pine bark : 1 sand, respec tively, In a timed exposure experiment using bark, minimum metolachlor adsorption (57%) was at 90 seconds and maximum adsorption (82%) requi red at least 1440 minutes, In column leaching studies, data for all me dia indicate that metolachlor is relatively immobile through these sub strates. An initial pulse of metolachlor (<1.0 mu g . liter(-1)) was d etected with each medium up to the third wetting event with a subseque nt decline (>0.5 mu g . liter(-1) for each medium) in the metolachlor recovered. Filtration efficiency of commercially formulated metolachlo r from water passed through different lengths of pine bark filled filt ers was 0%, 17%, 20%, 22%, 23%, and 29% for filters 4, 20, 12, 8, 16, and 24 cm in length, respectively, These results support the contentio n that such filtration would be effective provided the residence time of water within the filter was sufficient for adsorption of the contam inant by the media to occur.