Impact of Dissolved Organic Matter on the Desorption and Mineralization Rates of Naphthalene

Abstract

The persistence of organic contaminants in plant-soil systems will be largely determined by the basic processes controlling bioavailability: desorption and biodegradation. Both processes can be affected by the presence of and variations in dissolved organic matter (DOM). To evaluate potential effects of DOM in surface soil remediation systems, the kinetics of naphthalene desorption from soil and mineralization in soil solution in the presence of DOM were studied in completely mixed batch reactors (CMBRs). Three different DOM solutions were studied. These were obtained from water extraction of two different soils (muck-highly organic and alfalfa field-agricultural) and a third prepared by reconstituting a fulvic acid reference standard purchased commercially. Neither the desorption rate nor equilibrium partitioning of naphthalene was affected by the presence of varying DOM solutions. The effect on mineralization was evaluated based on an evaluation of a first-order rate constant produced by nonlinear regression of data fitted to a 14CO2 production model. For the muck DOM solution, alfalfa DOM solution, and 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 apparent in this data, the impact of DOM on the mechanisms of desorption and biodegradation in a plant -soil environment may be important for other contaminant/organism/soil combinations. With the increased interest in phytoremediation and land farming as means of treating organic contaminants, further investigation of such interactions may be warranted.