The Effect of the Organic Matter Composition on POP Accumulation in Soil
2012
Tremolada, Paolo | Guazzoni, Niccolò | Smillovich, Luisa | Moia, Fabio | Comolli, Roberto
The effect of different humic fractions on polychlorinated biphenyl (PCB) contamination in soils was tested in the field by means of 53 soil samples from a high-altitude grassland plateau in the Italian Alps. Three humic fractions (humin, humic acids, and fulvic acids) were characterized in parallel by quantifying 12 PCB congeners to establish a direct relationship between PCB levels and humic fraction concentrations. Humin (the most hydrophobic fraction) appears to be the most closely correlated with the amount of PCBs in soil (R ²â=â0.83), while fulvic acid shows the lowest correlation (R ²â=â0.49). The idea of preferential sorption of hydrophobic compounds in the humin fraction is discussed, and the humin carbon content (f âᵤâáµ¢âC) is proposed as an improved parameter for evaluating the potential for POP accumulation in soils, replacing total organic carbon (f âc). Congener studies revealed that penta- and hexa-substituted-CBs show the optimal combination of physicochemical properties for equilibrating with the humin content in soil. Moreover, f âᵤâáµ¢âC/f âc is conceptually equivalent to the empirical coefficients used in predictive K ââ equations. In our samples, the f âᵤâáµ¢âC/f âc was 0.55, a value in between the empirical coefficients proposed in the literature. In predictive equations, the use of f âᵤâáµ¢âC instead f âc avoids the necessity of using an empirical parameter for a ‘generic’ condition by introducing an experimental parameter (f âᵤâáµ¢âC) that takes into account local conditions (organic matter composition).
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