Inputs and seasonal removal of pharmaceuticals in the estuarine Garonne River

•53 pharmaceuticals were screened in the estuarine Garonne River during 18 months.•10 kg of the 30 most detected pharmaceuticals entered daily the estuary from the Garonne River.•Pharmaceutical concentrations decreased with tidal intrusion and high river flows.•The influence of urban effluent discharges was observed nearby Bordeaux city.•Degradation of the most labile pharmaceuticals was enhanced during low flow periods.

Pharmaceuticals were screened in the estuarine Garonne River to investigate the role of estuaries as passive or active transfer compartments in the removal of these compounds. Monthly monitoring of 53 pharmaceuticals from various therapeutic classes at 6 sampling points over 18 months showed that most compounds were frequently detected with median concentrations in the low ng L− 1 range. Saline intrusion was responsible of an overall dilution but an enrichment from the treated urban effluents of Bordeaux city was also observed with increases resulting from this input being compound dependent. An average cumulated load of 10 kg of the monitored pharmaceuticals was found to enter the estuary daily from the catchment area. After normalization to the persistent marker carbamazepine, a large majority of the compounds were found to exhibit in-stream attenuation during summer while this removal was enhanced farther down the estuary, indicating a likely effect of residence time, temperature and suspended solid concentration on the stability of the pharmaceuticals.