Sulfadimethoxine and sulfaguanidine: Their sorption potential on natural soils Anna Białk-Bielin ´ ska a,⇑ , Joanna Maszkowska a , Wojciech Mrozik b , Agata Bielawska a , Marta Kołodziejska a , Richard Palavinskas c , Piotr Stepnowski a , Jolanta Kumirska a a Department of Environmental Analysis, Faculty of Chemistry, University of Gdan ´sk, ul. Sobieskiego 18, 80-952 Gdan ´sk, Poland b Medical University of Gdan ´sk, Department of Inorganic Chemistry, Al. Gen. J. Hallera 107, 80-416 Gdan ´sk, Poland c Federal Institute for Risk Assessment BfR, Thielallee 88-92, D-14195 Berlin, Germany article info Article history: Received 1 September 2011 Received in revised form 12 November 2011 Accepted 18 November 2011 Available online 23 December 2011 Keywords: Sulfonamides Sulfadimethoxine Sulfaguanidine Soil Sorption Natural environment abstract Sulfonamides (SAs) are one of the oldest groups of veterinary chemotherapeutic agents. As these com- pounds are not completely metabolized in animals, a high proportion of the native form is excreted in feces and urine. They are therefore released either directly to the environment in aquacultures and by grazing animals, or indirectly during the application of manure or slurry. Once released into the environ- ment, SAs become distributed among various environmental compartments and may be transported to surface or ground waters. The physicochemical properties of SAs, dosage and nature of the matrix are the factors mainly responsible for their distribution in the natural environment. Although these rather polar compounds have been in use for over half a century, knowledge of their fate and behavior in soil ecosystems is still limited. Therefore, in this work we have determined the sorption potential of sulfadi- methoxine and sulfaguanidine on various natural soils. The influence on sorption of external factors, such as ionic strength and pH, were also determined. The sorption coefficients (K d ) obtained for the sulfona- mides investigated were quite low (from 0.20 to 381.17 mL g À1 for sulfadimethoxine and from 0.39 to 35.09 mL g À1 for sulfaguanidine), which indicated that these substances are highly mobile and have the potential to run off into surface waters and/or infiltrate ground water. Moreover, the sorption of these pharmaceuticals was found to be influenced by OC, soil solution pH and ionic strength, with higher K d values for soils of higher OC and lower K d values with increasing pH and ionic strength. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Sulfonamides are among the most commonly consumed veter- inary antibiotics in the EU (García-Galán et al., 2009): they are used in agriculture to prevent disease and to treat illness in livestock. Following their administration, substantial quantities may be ex- creted as the parent compounds and/or metabolites and leak into the environment while animals are grazing or during the spreading of manure. Moreover, during the storage of manure, the excreted acetyl conjugates can be cleaved back to the parent compound (Sukul and Spiteller, 2006). Therefore, once released into the envi- ronment, SAs are distributed among different environmental com- partments and can be transported to surface and ground waters. They can also enter the food chain and impact on natural environ- ment and human health. The physicochemical properties, applied dosage and the nature of the environmental components with which they interact govern the whole process. However, knowl- edge of the behavior and fate of these rather polar pollutants in soil ecosystems is still limited. Previous studies revealed that these compounds are present in soils and manure in concentrations of up to 15 lg kg À1 of soil and 20 mg kg À1 of liquid manure (Sukul and Spiteller, 2006). As soil is the most exposed to pollution by these substances, the degree to which they disperse in this matrix needs to be assessed. It is also important to determine the mobility of these substances in soils with different physicochemical properties in order to gain a better understanding of the general risk accompanying the entry of sul- fonamides into surface and ground waters, and thus to assess the scale of threats to the environment and human health. Such studies are necessary as far as the ecotoxicological potential of sulfona- mides is concerned. Our recent studies have shown that these com- pounds can pose a real risk to aquatic organisms, especially to higher plants like duckweed Lemna minor and algae (Białk-Bielin ´ ska et al., 2011). It is therefore of the utmost importance to evaluate their sorption potential and to determine their behavior and fate in the soil environment. Although SAs have been the subject of many investigations, to date only a few studies have focused on the behavior and fate in soils of these rather polar pharmaceuticals. Moreover, most studies have dealt with sulfadiazine (Thiele-Bruhn et al., 2004; Burkhardt et al., 2005; Stoob et al., 2007; Sukul et al., 2008; Schauss et al., 0045-6535/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2011.11.058 ⇑ Corresponding author. Tel.: +48 58 5235448. E-mail address: abialk@chem.univ.gda.pl (A. Białk-Bielin ´ ska). Chemosphere 86 (2012) 1059–1065 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere