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

Residues of antibiotic pharmaceutical compounds (APCs) found in the environ ment are suspected to be translocated into the food chain End to provoke th e formation of resistant microorganisms. However, the behavior of APCs in s oils is largely unknown. In the present study batch experiments were carrie d 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 concentra tion of organic carbon (C-org 1.6 and 2.4%) and composition of soil organic matter (SOM). APCs in soil extracts were analyzed by high performance liqu id chromatography. The KF values of the Freundlich isotherm for SPY were 2. 2 (1.6% C-org) and 5.5 (2.4% C-org). The K-oc values were 101 and 308. The different K-oc values indicated that not only the quantity but also the com position of SOM affected the SPY adsorption. Adsorption of SPY was substant ially higher in moist than in air-dry soil. ABA, consisting of a carboxyl g roup instead of the sulfonamide group substituted with a N-heterocycle, was much less adsorbed than SPY (K-F 0.2). From this it was concluded that the N-heterocycle significantly contributed to the adsorption of SPY.