Exploitation of the Diffusive Gradient Technique for Measuring the Mobility of Persistent Organic Pollutants in Soils

The diffusion gradients in thin-films (DGT) technique has been developed and extensively investigated in the last two decades to measure heavy metal labile flux from solid to solution phase. Only recently this technique was applied to persistent organic pollutants and a novel organic diffusive prove (ODP) was described for measuring the mobility of naphthalene in the solid phase of soils. The objective of this study was to calibrate ODP for measuring also Phenol and Benzene. The diffusion coefficients of thees aromatic molecules were investigated at different temperatures, pH and salinity. Then the measure of the mass accumulated by the probe was used to assess the resupply of pollutant from solid phase to pore water in samples of top soils collected in the tar-distilling department of a coke-chemical enterprises. Traditional procedures of pollutant characterization in soil were performed in parallel. The dynamic sampling, implemented by the organic diffusive probe, points out the different response of the soils to pollutant depletion. The ODP measures in fact depends from the complex equilibrium between sorption/desorption and depletion/resupply and not to the total amount of pollutant in solid phase.