Organic micropollutants in water and sediment from Lake Mälaren, Sweden

Abstract

The occurrence and distribution of 111 organic micropollutants (OMPs) were evaluated in water and sediment samples from Lake Mälaren, Sweden, using a liquid chromatography-tandem mass spectrometry method. The partitioning of contaminants between lake compartments was estimated using solid water distribution coefficients (Kd) and organic carbon-water partitioning coefficients (KOC). In total, 30 and 24 OMPs were detected in lake water and sediment, respectively. Concentrations ranged from low ng/L to 89 ng/L (lamotrigine) in lake water and from low ng/g dry weight (dw) to 28 ng/g dw (citalopram) in sediment. Carbamazepine, lamotrigine, caffeine, and tolyltriazole were the dominant compounds in Lake Mälaren samples (both water and sediment). Seventeen OMPs were detected in both water and sediment samples, including carbamazepine, DEET, tolyltriazole, bicalutamide, caffeine, lamotrigine, and cetirizine. Log Kd values varied between 0.84 for lamotrigine and 4.4 for citalopram, while log KOC values varied between 2.1 for lamotrigine and 5.9 for citalopram. These results indicate that sorption to sediment plays a minor role in removal of all OMPs analyzed in the aqueous phase except for citalopram and cetirizine, which showed high sorption potential. The environmental risks of OMPs were assessed based on the RQ values. The worst-case scenario for environmental risk assessment was conducted using the maximum measured environment concentration. For most of the target OMPs, including tolyltriazole, bicalutamide, fexofenadine, oxazepam, cetirizine, and diclofenac, the RQ values were below 0.01, indicating low or no risk to lake ecosystems.