Adsorption of the antibiotic pharmaceutical compound sulfapyridine by a long-term differently fertilized loess Chernozem

Residues of antibiotic pharmaceutical compounds (APCs) found in the environment are suspected to be translocated into the food chain and to provoke the formation of resistant microorganisms. However, the behavior of APCs in soils is largely unknown. In the present study batch experiments were carried out with sulfapyridine (SPY) and p-aminobenzoic acid (ABA) amended to two loess Chernozem samples. Due to different fertilization in the course of a long-term field experiment samples differed substantially in the concentration of organic carbon (Corg 1.6 and 2.4%) and composition of soil organic matter (SOM). APCs in soil extracts were analyzed by high performance liquid chromatography. The KF values of the Freundlich isotherm for SPY were 2.2 (1.6% Corg) and 5.5 (2.4% Corg). The Koc values were 101 and 308. The different Koc values indicated that not only the quantity but also the composition of SOM affected the SPY adsorption. Adsorption of SPY was substantially higher in moist than in air-dry soil. ABA, consisting of a carboxyl group instead of the sulfonamide group substituted with a N-heterocycle, was much less adsorbed than SPY (KF 0.2). From this it was concluded that the N-heterocycle significantly contributed to the adsorption of SPY.