Abstract

Constructed wetlands are used extensively to mitigate surface runoff. While wetland treatment for nitrogen (N) has been comprehensively studied, a knowledge gap remains regarding the implications of other contaminants (e.g., pesticides, pharmaceuticals) on nitrate-N (NO3-N) removal. This study sought to fill that gap by determining the impact imidacloprid, caffeine, perfluorooctane sulfonic acid (PFOS), atrazine, glyphosate, and sulfate (SO42−) have on NO3-N removal rates. The contaminants were determined based on their occurrence across Kentucky surface waters in urban (imidacloprid, caffeine, and PFOS) and rural (atrazine, glyphosate, and SO42−) environments. Two constructed wetland designs, floating treatment wetlands (FTWs), and free-water surface wetlands (FWSs), were evaluated along with planted and un-planted controls, equating to 24 mesocosms. Individual contaminants in both designs inhibited the rate of NO3-N removal, while the presence of the contaminants in their mixtures decreased N removal rates in FWSs compared to FTWs. However, by the end of each trial, 72–99 % of the NO3-N was removed despite the wetland design or the presence of contaminant(s). The FWSs outperformed the FTWs earlier in the growing season (May–June) when the water temperatures were colder, while the FTWs outperformed the FWSs when the plants reached maturity (July–September). Both FTWs and FWSs observed significant removal of contaminants with 28–89 %, 63–70 %, >90 %, and >92 % removal for PFOS, caffeine, glyphosate, and atrazine, respectively. Limited removal of SO42− was observed (≤57.9 %). These findings improve our understanding of water treatment for contaminant mixtures and their impact on NO3-N removal, guiding treatment wetland design and placement.

Document Type

Article

Publication Date

2025

Notes/Citation Information

0301-4797/© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jenvman.2025.125518

Funding Information

This project was supported by a National Science Foundation Grant No. 2042761, National Science Foundation Grant No. 1922695, the U.S. Geological Survey and the Kentucky Water Research Institute under Grant No. G21AP10631, United States Hatch multistate capacity funding grant (W-4045), and UK-CARES P30 ES026529. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NSF, USGS, USDA, or NIEHS. Mention of trade names or commercial products in this publication is solely to provide specific information and does not imply recommendation or endorsement by the U.S. Government. The USDA is an equal opportunity provider and employer.

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