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Open AccessArticle

Effects of Water Depth and Phosphorus Availability on Nitrogen Removal in Agricultural Wetlands

1
Rydberg Laboratory for Applied Sciences, Halmstad University, 301 18 Halmstad, Sweden
2
School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215000, China
*
Author to whom correspondence should be addressed.
Water 2019, 11(12), 2626; https://doi.org/10.3390/w11122626
Received: 29 October 2019 / Revised: 27 November 2019 / Accepted: 10 December 2019 / Published: 13 December 2019
Excess nitrogen (N) from agricultural runoff is a cause of pollution in aquatic ecosystems. Created free water surface (FWS) wetlands can be used as buffering systems to lower the impacts of nutrients from agricultural runoff. The purpose of this paper was to evaluate critical factors for N removal in FWS wetlands receiving high nitrate (NO3) loads from agriculture. The study was performed in 12 experimental FWS wetlands in southern Sweden, receiving drainage water from an agricultural field area. The effects of water depth (mean depth of 0.4 m and 0.6 m, respectively) and phosphorus (P) availability (with or without additional P load) were investigated from July to October. The experiment was performed in a two-way design, with three wetlands of each combination of depth and P availability. The effects of P availability on the removal of NO3 and total N were strongly significant, with higher absolute N removal rates per wetland area (g m−2 day−1) as well as temperature-adjusted first-order area-based removal rate coefficients (Kat) in wetlands with external P addition compared to wetlands with no addition. Further, higher N removal in deep compared to shallow wetlands was indicated by statistically significant differences in Kat. The results show that low P availability may limit N removal in wetlands receiving agricultural drainage water. Furthermore, the results support that not only wetland area but also wetland volume may be important for N removal. The results have implications for the planning, location, and design of created wetlands in agricultural areas. View Full-Text
Keywords: free water surface wetlands; agricultural runoff; nitrogen removal; water depth; phosphorus free water surface wetlands; agricultural runoff; nitrogen removal; water depth; phosphorus
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MDPI and ACS Style

Song, X.; Ehde, P.M.; Weisner, S.E.B. Effects of Water Depth and Phosphorus Availability on Nitrogen Removal in Agricultural Wetlands. Water 2019, 11, 2626.

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