|GHANE, EHSAN - University Of Minnesota|
|RANAIVOSON, ANDRY - University Of Minnesota|
|ROSEN, CARL - University Of Minnesota|
|MONCRIEF, JOHN - University Of Minnesota|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2016
Publication Date: 12/8/2016
Citation: Ghane, E., Ranaivoson, A.Z., Feyereisen, G.W., Rosen, C.J., Moncrief, J.F. 2016. Comparison of contaminant transport in agricultural drainage water and urban stormwater runoff. PLoS One. PLoS ONE 11(12):e0167834. doi:10.1371/journal.pone.0167834.
Interpretive Summary: Water quality of surface water bodies can be affected by transport of contaminants from both agricultural and urban landscapes. The main objective of this study was to quantify and compare transport of nitrogen, phosphorus, and sediment from agricultural farmland and city stormwater runoff in and near Willmar, Minnesota. Flow rates and contaminants were measured from city stormwater runoff and from subsurface tile drainage from fields that were 1) fertilized and 2) unfertilized. On a per area basis, the city stormwater transported more ammonium, sediment, and total phosphorus, but less nitrate than the fertilized field. Even though the unfertilized field had no fertilizer applied for 2 years prior to or during the 7-year study period, nitrate losses were about 60% as much as for the fertilized field. When the contaminant losses per unit area were multiplied by the urban and agricultural areas in the study watershed, losses of ammonium and sediment were greater for the city stormwater while losses of nitrate and total phosphorus were greater for the agricultural watershed.
Technical Abstract: Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts including hypoxia and harmful algal blooms. The main objective of this long-term study was to quantify and compare contaminant transport from a subsurface-drained farm to that of an urban landscape. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields, namely, Unfertilized and Fertilized Fields. Results showed that the City Stormwater transported significantly greater loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly smaller. Nitrate load transport from the Unfertilized Field was 59.8% as much as that of the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load for the City Stormwater, a 1.07% increase in nitrate load for the Fertilized Field, and a 1.12% increase in TP load for the Fertilized Field. This indicates increase in concentration with rise in flow depth, revealing that concentration variation was a significant factor influencing dynamics of load transport. Regression analysis further showed that hydrology also played a dominant role in the dynamics of load transport, stressing the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, best management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target from both.