Sorption and Degradation of Selected Pharmaceuticals in Controlled Laboratory Column Experiments

Pharmaceutically active compounds have increasingly been detected in groundwater worldwide. Despite constituting a major risk for ecosystems and human health, their fate in the environment has still not been thoroughly investigated. This study characterizes the transport behavior of five selected pharmaceutically active compounds (antipyrine, atenolol, caffeine, carbamazepine and sulfamethoxazole) in two sediments (coarse quartzsand and sandy loam) using column experiments with long-term injection of spiked groundwater accompanied by monitoring of microbial activity in the columns. Transport parameters were estimated using an analytical reactive transport model. When five selected compounds were injected simultaneously, transport behavior of antipyrine, carbamazepine and the antibiotic sulfamethoxazole were similar to the conservative tracer in both sediments and under varying redox conditions. During the entire duration of the experiments of about two months no degradation was observed, thus showing the low potential for natural attenuation. Atenolol and caffeine were subject to retardation which was significantly stronger in the sandy loam sediment compared to the coarse quartzsand. This was attributed to higher contents in clay and organic carbon in sandy loam. Biodegradation of caffeine was observed in three out of four non-sterilized settings after an adaption period of 120 to 420 hours and was dependent on the presence of dissolved oxygen. Atenolol was biologically degraded in the coarse quartzsand while the type of degradation remained unclear in the sandy loam sediment. The identification of biodegradation processes was supported by monitoring of intracellular adenosine triphosphate (ATP_itc) as a measure for microbial activity. ATP_itc was present in varying concentrations in all sediments with higher concentrations when degradation of pharmaceuticals, especially caffeine, was observed. When only caffeine and sulfamethoxazole were injected simultaneously, sulfamethoxazole was degraded while caffeine was not. The latter seems to be influenced by low concentrations in dissolved oxygen rather than the presence of the antibiotic sulfamethoxazole. Results of these experiments emphasize the impact of sediment type and redox conditions on pharmaceutical transport as well as the effect of combination and variety of pharmaceuticals that are released together into the environment.