Occurrence and Spatiotemporal Dynamics of Pharmaceuticals
in a Temperate-Region Wastewater Effluent-Dominated Stream: Variable
Inputs and Differential Attenuation Yield Evolving Complex Exposure
Mixtures
posted on 2020-10-06, 19:11authored byHui Zhi, Dana W. Kolpin, Rebecca D. Klaper, Luke R. Iwanowicz, Shannon M. Meppelink, Gregory H. LeFevre
Effluent-dominated streams are becoming
increasingly common in
temperate regions and generate complex pharmaceutical mixture exposure
conditions that may impact aquatic organisms via drug–drug
interactions. Here, we quantified spatiotemporal pharmaceutical exposure
concentrations and composition mixture dynamics during baseflow conditions
at four sites in a temperate-region effluent-dominated stream (upstream,
at, and progressively downstream from effluent discharge). Samples
were analyzed monthly for 1 year for 109 pharmaceuticals/degradates
using a comprehensive U.S. Geological Survey analytical method and
biweekly for 2 years focused on 14 most common pharmaceuticals/degradates.
We observed a strong chemical gradient with pharmaceuticals only sporadically
detected upstream from the effluent. Seventy-four individual pharmaceuticals/degradates
were detected, spanning 5 orders of magnitude from 0.28 to 13 500
ng/L, with 38 compounds detected in >50% of samples. “Biweekly”
compounds represented 77 ± 8% of the overall pharmaceutical concentration.
The antidiabetic drug metformin consistently had the highest concentration
with limited in-stream attenuation. The antihistamine drug fexofenadine
inputs were greater during warm- than cool-season conditions but also
attenuated faster. Differential attenuation of individual pharmaceuticals
(i.e., high = citalopram; low = metformin) contributed to complex
mixture evolution along the stream reach. This research demonstrates
that variable inputs over multiple years and differential in-stream
attenuation of individual compounds generate evolving complex mixture
exposure conditions for biota, with implications for interactive effects.