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Article

Effectiveness of a Natural Headwater Wetland for Reducing Agricultural Nitrogen Loads

1
Department of Geography, University of Tartu, 51014 Tartu, Estonia
2
National Institute ofWater and Atmospheric Research Limited, P.O. Box 11 115, Hamilton 3251, New Zealand
*
Author to whom correspondence should be addressed.
Water 2018, 10(3), 287; https://doi.org/10.3390/w10030287
Received: 10 February 2018 / Revised: 2 March 2018 / Accepted: 2 March 2018 / Published: 8 March 2018
(This article belongs to the Special Issue Wetlands for the Treatment of Agricultural Drainage Water)
Natural wetlands can play a key role in controlling non-point source pollution, but quantifying their capacity to reduce contaminant loads is often challenging due to diffuse and variable inflows. The nitrogen removal performance of a small natural headwater wetland in a pastoral agricultural catchment in Waikato, New Zealand was assessed over a two-year period (2011–2013). Flow and water quality samples were collected at the wetland upper and lower locations, and piezometers sampled inside and outside the wetland. A simple dynamic model operating on an hourly time step was used to assess wetland removal performance for key N species. Hourly measurements of inflow, outflow, rainfall and Penman-Monteith evapotranspiration estimates were used to calculate dynamic water balance for the wetland. A dynamic N mass balance was calculated for each N component by coupling influent concentrations to the dynamic water balance and applying a first order areal removal coefficient (k20) adjusted to the ambient temperature. Flow and water quality monitoring showed that wetland was mainly groundwater fed. The concentrations of oxidised nitrogen (NOx-N, Total Organic Nitrogen (TON) and Total-N (TN) were lower at the outlet of the wetland regardless of flow conditions or seasonality, even during winter storms. The model estimation showed that the wetland could reduce net NOx-N, NH4-N, TON and TN loads by 76%, 73%, 26% and 57%, respectively. View Full-Text
Keywords: wetland attenuation; nitrogen; nutrient removal; denitrification; modelling; agricultural pollution wetland attenuation; nitrogen; nutrient removal; denitrification; modelling; agricultural pollution
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MDPI and ACS Style

Uuemaa, E.; Palliser, C.C.; Hughes, A.O.; Tanner, C.C. Effectiveness of a Natural Headwater Wetland for Reducing Agricultural Nitrogen Loads. Water 2018, 10, 287. https://doi.org/10.3390/w10030287

AMA Style

Uuemaa E, Palliser CC, Hughes AO, Tanner CC. Effectiveness of a Natural Headwater Wetland for Reducing Agricultural Nitrogen Loads. Water. 2018; 10(3):287. https://doi.org/10.3390/w10030287

Chicago/Turabian Style

Uuemaa, Evelyn, Chris C. Palliser, Andrew O. Hughes, and Chris C. Tanner 2018. "Effectiveness of a Natural Headwater Wetland for Reducing Agricultural Nitrogen Loads" Water 10, no. 3: 287. https://doi.org/10.3390/w10030287

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