Fate, dissipation, and mass balance of antipsychotic pharmaceuticals in outdoor aquatic mesocosms

This work describes the fate of amitriptyline, bupropion, carbamazepine, citalopram, clozapine, duloxetine, fluoxetine, lamotrigine, and venlafaxine using outdoor aquatic mesocosms. Water-sediment and water-gravel tanks were treated with a single amendment of the nine psychoactive pharmaceuticals and tracked in water and sediment over 272 days. Behaviour of the target chemicals followed three general fate profiles: 1) amitriptyline, bupropion, clozapine, and duloxetine dissipated rapidly with t1/2 < 2 day, and with minimal sorption); 2) carbamazepine and lamotrigine exhibited slower dissipation, with t1/2 > 10 day and minimal sorption; and 3) citalopram, fluoxetine, and venlafaxine exhibited rapid dissipation in the water column (t1/2 < 4 day) but significant sorption to sediments. Transformation products for clozapine (m/z 343.1315), duloxetine (m/z 312.1053), and venlafaxine (m/z 264.1955) were tentatively identified, semi-quantified, and included in the mass balance calculations. Duloxetine TP312 was the only product that contributed significantly to the overall mass balance, accounting for nearly 100% of the duloxetine inventory between 8 and 24 hr, before starting to dissipate. These results show that while fate mechanisms are broadly consistent among lab, mesocosm, and field studies, half-lives can vary markedly as a function of study design, and simplified systems, such as single-compartment beaker studies, can influence conclusions regarding chemical fate. This study adds to the growing body of literature describing the environmental behaviour of this important pharmaceutical class and highlights the value of outdoor mesocosm systems for generating chemical fate data.