alpha-naphthol sorption as regulated by structure and composition of organic substances in soils and sediments

Humic acids (HAs) from major horizons of a Gleyed Black Chernozem and a set of soil and sediment samples were examined to understand the influence of the structure and composition of organic substances on sorption of organic pollutants. Solid state C-13 cross-polarized/magic angle spinning (CP/MAS) NMR results indicated that the aromaticity of HAs increased with soil depth. The aromaticity of organic substances in bulk soils and sediments varied with the degree of geological diagenesis. Sorption experiments showed a linear relationship between the carbon normalized partition coefficient (K-oc) of alpha-naphthol and the aromaticity of HAs and non-extracted organic substances in whole soils and sediments. The K-oc values of alpha-napthol had a log-linear relationship with the atomic mass ratio (N+O)/C of the organic substances in soils and sediments. Correlation analysis for the literature data further revealed that the compositional and structural properties of organic substances were related, suggesting possibilities of predicting K-oc with either compositional or structural parameters. Measured K-oc values demonstrated considerable deviations from those calculated with prediction models using K-oc. The prediction models may not be accurate because they do not account for the compositional and structural differences in organic substances of sorbents.