Sorption and desorption of benzo[a]pyrene by soils of the coastal zone of Taganrog Bay, Russia

In a model experiment, the sorption–desorption of benzo(a)pyrene (BaP), the most hazardous representative of PAHs was studied by samples of ordinary carbonate chernozem, alluvial meadow saturated and alluvial meadow saturated layered soils taken from different horizons. BaP desorption was studied using water-soluble organic matter (WOM) isolated from the same soils. It was shown that the Dubinin–Radushkevich model best describes the adsorption isotherms in comparison with the Langmuir, Freundlich and Henry models. This indicates a predominantly multilayer nature of adsorption and volumetric filling of the micropores of the studied soils with BaP. The isotherms of BaP desorption from the saturated soils by WOM solutions have a shape close to linear or parabolic. The strength of the bond of sorbed BaP in humus soil horizons is higher that in mineral ones and naturally decreases with a decrease in the content of organic matter. It was found that the sorption capacity of soils with respect to BaP decreases in the following series: ordinary carbonate chernozem > alluvial meadow saturated > alluvial meadow saturated layered. At the same time, the degree of desorption by soil increases with an decrease in the content of organic carbon in it and with an increase in the initial concentration of the pollutant in the solution during the soil saturation.