Phosphorus Retention in a Newly Constructed Wetland Receiving Agricultural Tile Drainage Water

Abstract

One measure used in Sweden to mitigate eutrophication of waters is the construction of small wetlands (free water surface wetland for phosphorus retention [P wetlands]) to trap particulate phosphorus (PP) transported in ditches and streams. Th is study evaluated P retention dynamics in a newly constructed P wetland serving a 26-ha agricultural catchment with clay soil. Flow-proportional composite water samples were collected at the wetland inlet and outlet over 2 yr (2010)(2011) and analyzed for total P (TP), dissolved P (DP), particulate P (PP), and total suspended solids (TSS). Both winters had unusually long periods of snow accumulation, and additional time-proportional water samples were frequently collected during snowmelt. Infl ow TP and DP concentrations varied greatly (0.02-1.09 mg L −1 ) during the sampling period. During snowmelt in 2010, there was a daily oscillation in P concentration and water fl ow in line with air temperature variations. Outfl ow P concentrations were generally lower than infl ow concentrations, with net P losses observed only in August and December 2010. On an annual basis, the wetland acted as a net P sink, with mean specifi c retention of 69 kg TP, 17 kg DP, and 30 t TSS ha −1 yr −1 , corresponding to a reduction in losses of 0.22 kg TP ha −1 yr −1 from the agricultural catchment. Relative retention was high (36% TP, 9% DP, and 36% TSS), indicating that small constructed wetlands (0.3% of catchment area) can substantially reduce P loads from agricultural clay soils with moderately undulating topography.

Phosphorus and particle retention in constructed wetlands—A catchment comparison

“…In the ICECREAM model, different P fraction concentrations (both dissolved and particulate P) are calculated and the proportion of dissolved P (DP) varied from 21% in Eks to 44% in Wig. In Ber, the mean modeled DP concentration accounted for 39% of TP, which is in accordance with results from a water quality study presented by Kynkäänniemi et al (2013). Their results showed that on an annual basis, DP constituted approximately one third of TP.…”

“…Two of the wetlands, Ber and Ski, were both designed with a shallow section covered with emergent plants following an open water inlet section. Ber consisted of a 1 m deep sedimentation pond followed by a 0.3 m deep section with emergent plants (Kynkäänniemi et al, 2013). In Ski, the shallow (0.2-0.3 m) section was placed between two deeper (approximately 1.2 m) sections (Fig.…”

Phosphate Removal from Agricultural Tile Drainage with Iron Enhanced Sand

“…Dividing the volume treated (27, Overall, the performance of the IESF in this study (63.9% phosphate and 66.3% total phosphorus load reduction) is comparable to other agricultural treatment practices and studies of IESFs. The IESF captures more phosphorus than constructed wetlands, for both total phosphorus (2-44%, [10][11][12][13][14]) and phosphate (9%, [12]), though the data falls within the upper range reported for a study of 17 intensively studied constructed wetlands (TP = 1-88%; DRP = −19 to 89%, [15]). Laboratory experiments of IESFs in previous studies found an average of 88% phosphate capture with a total treated depth of 200 m [18].…”

Legacy Nutrient Dynamics at the Watershed Scale: Principles, Modeling, and Implications

“…Sediments having high Al, Fe, and organic matter contents are favor of accumulating legacy P pools since flooding promotes the P adsorption by created noncrystalline forms of Fe, Al, and organic matter (Ardón et al, 2010). In terms of geographical location, standing waters that located closer to the source (e.g., croplands and wastewater discharge) can more substantially retain nutrients (Kynk€ a€ anniemi et al, 2013). In shallow and productive waters, P accumulation rate can be enhanced by increasing of dissolved oxygen at the sediment surface in response to fluctuating water levels and vegetation growth cycles (e.g., summer) or by receiving Fe and Al loads from entered runoff (Reddy and DeLaune, 2008).…”