Source-specific sewage pollution detection in urban river waters using pharmaceuticals and personal care products as molecular indicators

Source-specific elucidation of domestic sewage pollution caused by various effluent sources in an urban river water, as conducted for this study, demands knowledge of the relation between concentrations of pharmaceuticals and personal care products (PPCPs) as molecular indicators (caffeine, carbamazepine, triclosan) and water quality concentrations of total nitrogen (T-N) and total phosphorous (T-P). River water and wastewater samples from the Asahikawa River Basin in northern Japan were analyzed using derivatization-gas chromatography/mass spectrometry. Caffeine, used as an indicator of domestic sewage in the Asahikawa River Basin, was more ubiquitous than either carbamazepine or triclosan (92–100 %). Its concentration was higher than any target compound used to assess the basin: <4.4–370 ng/L for caffeine, <0.6–3.9 ng/L for carbamazepine, and <1.1–13 ng/L for triclosan. Higher caffeine concentrations detected in wastewater effluents and the strongly positive mutual linear correlation between caffeine and T-N or T-P (R2 > 0.759) reflect the contribution of septic tank system effluents to the lower Asahikawa River Basin. Results of relative molecular indicators in combination with different molecular indicators (caffeine/carbamazepine and triclosan/carbamazepine) and cluster analysis better reflect the contribution of sewage than results obtained using concentrations of respective molecular indicators and cluster analysis. Relative molecular indicators used with water quality parameters (e.g., caffeine/T-N ratio) in this study provide results more clearly, relatively, and quantitatively than results obtained using molecular indicators alone. Moreover, the caffeine/T-N ratio reflects variations of caffeine flux from effluent sources. These results suggest strongly relative molecular indicators are also useful indicators, reflecting differences in spatial contributions of domestic sources for PPCPs in urban areas.