Nevertheless, They Persisted: Can Hyporheic Zones Increase the Persistence of Estrogens in Streams?. Issue 6 (22nd June 2021)

• Record Type: Journal Article
• Authors: Cheng, Frederick Y.; Preisendanz, Heather E.; Mashtare, Michael L.; Lee, Linda S.; Basu, Nandita B.
• Is Part Of: Water resources research. Volume 57:Issue 6(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-22
• Subjects: agricultural legacies -- contaminant fate -- emerging contaminants -- estrogen -- hyporheic zone; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR028518
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: The presence of estrogens has been linked to adverse ecological effects in surface waters downstream of agricultural and domestic wastewater sources. While laboratory studies suggest that these estrogens should not persist because of fast degradation rates, elevated concentrations in surface waters impacted by agricultural activities are commonly observed. Using a combination of measured data and a stream‐hyporheic zone (HZ) model applied to a 100 km reach in a tile‐drained catchment, we show that the HZ can increase the persistence of estrogens. Field data reveal high concentrations of sorbed estrogens in sediments and elevated in‐stream concentrations during low‐flow summer months, suggesting that the HZ acts as a source of estrogens when transport into the streams is minimal. Model results provide further insight into the underlying mechanisms that enable sustained estrogen concentrations in streams, with the HZ acting as a source of dissolved estrogens for 95% of the year. We show that stream water interactions with the HZ may lead to overall suppression of degradation processes and an increase in the persistence of estrogens. Results suggest that when the model considered exchange in the HZ, approximately 28%–49% of estrogen mass remained in the stream ecosystem, while all estrogen mass was degraded in a 100‐km reach in the model without the HZ. The remaining mass increased with increasing estrogen sorption coefficient, and this would potentially increase the lag time for lowering estrogen concentrations in surface water bodies even when inputs have ceased. Our findings highlight the importance of including HZ dynamics in estrogen transport models. Plain Language Summary: Steroidal hormones are commonly found in manure and are frequently detected in agricultural streams. There is an increased interest in the fate of these hormones in the aquatic environment as prolonged exposure to these compounds at trace‐level concentrations can cause severe impacts in sensitive aquatic species, including fish. An outstanding question is why hormones are so common in streams when lab studies suggest that they should break down quickly, on the order of hours to days. Through field data analysis and model simulations, we show that the physical and chemical interactions within the streambed increase the persistence of hormones in the stream. Our model shows that the streambed is a storage or "sink" for hormones when stream water concentrations of hormones are high whereas under low stream water concentrations, the streambed behaves as a "source" by releasing the hormones back into the stream water. The streambed increases the amount of time that the hormones stay in the stream because light helps in hormone degradation, and this is reduced in the streambed. Our study highlights the need to consider this streambed interaction in models because ignoring this "source‐sink" behavior can lead to underestimations of where and for how long hormones remain in streams. Key Points: Hyporheic zone (HZ) acts as a persistent source of estrogens for 95% of the year and a sink only during high flow events (5% of year) Estrogen sorption in the HZ inhibits photodegradation, and thus increases its persistence in the stream ecosystem Increasing estrogen sorption increases persistence and leads to higher lag times in water quality improvement after inputs have ceased