Sorption of selected pharmaceuticals on river benthic biofilms formed on artificial substrata

Abstract

The dissolved organic and inorganic contaminants in rivers, lakes and seas are distributed among the aquatic phase, biota, sediments and biofilms formed on different artificial and natural substrata. Since the biofilms play an important role in the food web of aquatic ecosystems, it is necessary to clarify what kind of contaminants are bounded to these biological surfaces. In this study the concentration of eight pharmaceuticals (carbamazepine, ciprofloxacin, clarithromycin, diclofenac, metoprolol, sitagliptin, sulfamethoxazole and tetracycline) was determined in the Danube water at Budapest (Hungary) and in the biofilms formed on glass and polycarbonate substrata during a six weeks long growing period at the same sampling site. The target compounds were extracted from the dried biofilms by microwave (MW) assisted hot water treatment, however, the recovery of tetracycline was extremely low, indicating damage and loss of this constituent caused by MW treatment. The concentrations of the other seven pharmaceuticals were determined by LC-MS following the solid phase extraction of analytes. Clarithromycin, ciprofloxacin, diclofenac, metoprolol and sitagliptin were detectable in the biofilms due to biological uptake and electrostatic-mediated adsorption on the negatively charged biofilms, however, carbamazepine and sulfamethoxazole with neutral charge were not detected. The bioaccumulation factors of biofilms grown on glass or polycarbonate substrata changed between 175 and 614 and 148–314 L/kg, respectively, and increased in order of diclofenac < sitagliptin < clarithromycin < ciprofloxacin < metoprolol. These values are about 2–3 orders of magnitude lower than the published data for different metal cations which form chemical complexes or chelates with carboxyl and hydroxyl groups of extracellular polymer matrix. Due to the higher amount of adsorbed pharmaceuticals and the higher biodiversity of diatom species in the biofilms formed on glass substrata, compared to polycarbonate, as artificial substrata the glass carrier plates can be recommended for biofilm studies.