Quantifying the Seasonal Variation of Environmental Pharmaceutical Residues

Pharmaceutical substances, among other contaminants drained from wastewater treatment process and entered into aqueous environments, exhibit significant seasonal dependencies in their environmental concentrations. Although measurement data on removal of pharmaceutical residues in wastewater treatment plants and their degradation in the environment thereafter are readily available, the complexity and uniqueness of the sampling scenarios makes general numerical estimation of these phenomena difficult. To gain quantitative insight on the mass balances of environmental pharmaceutical residues and their seasonal variations, measurement data of four pharmaceuticals were collected from the literature and an effort was undertaken to uniform them and parametrise them with as few variables as feasible. Temperature was found to be a commonly available parameter with a marked trendsetting effect, and the prospect of using it to characterise the variation was examined. Ways to reliably assess the effects of dilution and other advective phenomena on the measured concentrations were explored, and a simple method for using cross-comparisons of different pharmaceuticals to this end is presented. A corresponding fugacity model scenario was also constructed to provide a computational baseline for the mass balance.