BETA-HCH MOBILIZATION IN POLLUTED WETLAND SOILS AS INFLUENCED BY DISSOLVED ORGANIC-MATTER

The beta isomer of 1,2,3,4,5,6-hexachlorocyclohexane (beta-HCH) which is formed during synthesis of the pesticide lindane shows high mobilit y in polluted soils despite its low water solubility. Therefore, we st udied the correlation between the quantity and quality of dissolved or ganic matter (DOM) and the mobilization and transport of beta-HCH in t wo soil profiles used as grassland and in incubation experiments. From our results we conclude that beta-HCH was mobilized and transported t o deeper soil horizons probably by coupling between beta-HCH and DOM. The interaction of beta-HCH with DOM as indicated by the measured high partition coefficient between beta-HCH and DOM (logK(DOC) = 4.39) was much higher than would be expected from the physicochemical propertie s of beta 4-HCH. As suggested from synchronous fluorescence spectrosco py data, the capacity of DOM to bind beta-HCH increases as the more ex tended aromatic regions of DOM are accessible in the aqueous extracts. The addition of lime and fresh organic matter to the grassland soils did not affect the measured coupling between beta-HCH and DOM. Long dr ying periods increased the coupling up to 9.9 mu g beta-HCH per mg DOC . Water-logging destroyed the binding between DOM and beta-HCH despite increasing DOC contents. Our main conclusion is that qualitative diff erences in DOM due to changed environmental conditions can drastically change the coupling of hydrophobic organic pollutants to DOM and grea tly affect pollutant mobilization and translocation. (C) 1997 Elsevier Science B.V.