Sorption of atenolol, sulfamethoxazole and carbamazepine onto soil aggregates from the illuvial horizon of the Haplic Luvisol on loess

The leakage of pharmaceuticals present in soils towards groundwater is largely controlled by sorption of those compounds in soils. In some soils, soil aggregates are covered by coatings, which may have considerably different composition in comparison to that in an inner part of the aggregates. The aim of this study was to evaluate the sorption of three pharmaceuticals, which were applied in single or all compounds solutions, onto soil samples taken from the Bt horizon of a Haplic Luvisol. Analyses were performed on three types of disturbed soil samples: (1) entire aggregates, (2) aggregates from which coatings were removed, and (3) clay-organic coatings. Sorption of atenolol onto material from coatings was slightly higher than that onto material from the inner parts of the aggregates. On the other hand, sorption of sulfamethoxazole onto material from the coatings was lower than that from the aggregate interior. Both associates with a dominant fraction of clay particles (that are mostly negatively charged) in the coatings in comparison to soil composition in interiors and thus larger cation exchange capacity, which increased sorption of the positively charged atenolol and decreased sorption of the negatively charged sulfamethoxazole. Sorption of carbamazepine, which was in neutral form, did not substantially differ. The sorption of all three compounds did not decrease due to the competition between these compounds for the same sorption sites when applied simultaneously. Atenolol sorption was similar for both applications. Sorption of sulfamethoxazole increased when applied in solution with the other two compounds in comparison to its negligible sorption measured for the single compound solution likely due to sorption of the positively charged molecules of atenolol onto the negatively charged surface of soil components and reduction of repulsion between the soil components and the negatively charged molecules of sulfamethoxazole. Carbamazepine sorption also increased probably due to ionization of molecules due to dipole - induced dipole interaction between non-polar and polar molecules in solution.