Interaction of naphthalene derivatives with soil: an experimental and theoretical case study

This study provides insight into the relevance of the chemical functional groups of soil organic matter (aromatic, paraffinic, O‐alkyl, carboxyl and carbonyl carbon), as determined by CPMAS ¹³C NMR, on adsorption processes. Batch adsorption experiments with eight naphthalene derivatives were conducted with soils from a long‐term field experiment and model sorbents. Although the adsorption of some derivatives was mainly affected by the paraffinic organic carbon content in soil, the relation between the C‐distribution and adsorption was complex. This casts doubt on the use of such NMR data to estimate sorption behaviour. Additionally, sorption experiments were performed with six model sorbents representing typical soil components. Considerable adsorption of naphthalene derivatives was observed for montmorillonite and lignin; the smallest values were for kaolinite and cellulose. A quantum chemical approach was used to calculate a local polarity parameter as a molecular property of the naphthalene derivatives. This parameter was correlated with the logarithm of the adsorption coefficients, logK_d. Here, clear trends were observed for three of the model sorbents (kaolinite, montmorillonite and lignin).