Impact of dissolved organic matter on the desorption and mineralization rates of naphthalene

The persistence of organic contaminants in plant-soil systems will be large ly determined by the basic processes controlling bioavailability: desorptio n and biodegradation. Both processes can be affected by the presence of and variations in dissolved organic matter (DOM). To evaluate potential effect s of DOM in surface soil remediation systems the kinetics of naphthalene de sorption from soil and mineralization in soil solution in the presence of D OM were studied in completely mixed batch reactors (CMBRs). Three different DOM solutions were studied. These were obtained from water extraction of t wo different soils (muck-highly organic and alfalfa field-agricultural) and a third prepared by reconstituting a fulvic acid reference standard purcha sed commercially. Neither the desorption rate nor equilibrium partitioning of naphthalene was affected by the presence of varying DOM solutions. The e ffect on mineralization was evaluated based on an evaluation of a first-ord er rate constant produced by nonlinear regression of data fitted to a (CO2) -C-14 production model. For the muck DOM solution, alfalfa DOM solution, an d fulvic acid DOM solution, first-order rate constants were 0.0474, 0.0657 0.0422 min(-1), respectively. Using uncertainty analysis, these differences were found not to be significant at a 90% confidence level. Although not a pparent in this data, the impact of DOM on the mechanisms of desorption and biodegradation in a plant-soil environment may be important for other cont aminant/organism/soil combinations. With the increased interest in phytorem ediation and land farming as means of treating organic contaminants, furthe r investigation of such interactions may be warranted.