title: 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. This 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. Inflow TP and DP concentrations varied greatly (0.02-1.09 mg L) during the sampling period. During snowmelt in 2010, there was a daily oscillation in P concentration and water flow in line with air temperature variations. Outflow P concentrations were generally lower than inflow 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 specific retention of 69 kg TP, 17 kg DP, and 30 t TSS ha yr, corresponding to a reduction in losses of 0.22 kg TP ha yr 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.
authors.forename: Pia
authors.initials: P
authors.lastname: Kynkäänniemi
authors.forename: Barbro
authors.initials: B
authors.lastname: Ulén
authors.forename: Gunnar
authors.initials: G
authors.lastname: Torstensson
authors.forename: Karin S
authors.initials: KS
authors.lastname: Tonderski
mesh_terms: D000383:Agriculture; D004322:Drainage; D010758:Phosphorus; D014867:Water; D014872:Water Movements; D053833:Wetlands
chemical_list: D014867:Water; D010758:Phosphorus