Line 33: | Line 33: | ||
==Ratios of dissolved to total phosphorus in runoff== | ==Ratios of dissolved to total phosphorus in runoff== | ||
Another consideration is the fraction or percent of total phosphorus in runoff that is in dissolved form. A more complete discussion of this [https://stormwater.pca.state.mn.us/index.php?title=Event_mean_concentrations_of_total_and_dissolved_phosphorus_in_stormwater_runoff#Ratios_of_particulate_to_dissolved_phosphorus is found here], including literature references. The data on phosphorus fractionation is limited, but the following general statements can be made. | Another consideration is the fraction or percent of total phosphorus in runoff that is in dissolved form. A more complete discussion of this [https://stormwater.pca.state.mn.us/index.php?title=Event_mean_concentrations_of_total_and_dissolved_phosphorus_in_stormwater_runoff#Ratios_of_particulate_to_dissolved_phosphorus is found here], including literature references. The data on phosphorus fractionation is limited, but the following general statements can be made. | ||
− | *Dissolved phosphorus in urban runoff in Minnesota typically ranges from 25 to 50 percent of total phosphorus in runoff. | + | *Urban runoff |
− | *The percent of phosphorus in dissolved form increases when phosphorus contributions from organic sources increase. For example, areas with higher tree canopy cover have a higher percent of dissolved phosphorus in runoff than areas with low canopy cover. | + | **Dissolved phosphorus in urban runoff in Minnesota typically ranges from 25 to 50 percent of total phosphorus in runoff. |
− | *Orthophosphate typically comprises about 60 to 80 percent of the dissolved phosphorus fraction. | + | **The percent of phosphorus in dissolved form increases when phosphorus contributions from organic sources increase. For example, areas with higher tree canopy cover have a higher percent of dissolved phosphorus in runoff than areas with low canopy cover. |
− | *The percent of total phosphorus that is in dissolved form varies seasonally. Dissolved phosphorus comprises a higher fraction of total phosphorus when organic inputs are freshest, such as spring fruit drop from trees and during leaf drop in fall. | + | **Orthophosphate typically comprises about 60 to 80 percent of the dissolved phosphorus fraction. |
+ | **The percent of total phosphorus that is in dissolved form varies seasonally. Dissolved phosphorus comprises a higher fraction of total phosphorus when organic inputs are freshest, such as spring fruit drop from trees and during leaf drop in fall. | ||
+ | *Agricultural runoff - for a good discussion of phosphorus in agricultural systems, [https://www.frontiersin.org/articles/10.3389/feart.2018.00135/full link here]. | ||
+ | **Fertilizer and manure have highly soluble forms of phosphorus | ||
+ | **Soluble phosphorus is slowly released from soil. However, if there are phosphorus inputs from fertilizer, soil will behave as a sink. | ||
+ | **An important distinction from urban systems is that water has the opportunity to infiltrate in agricultural systems, while phosphorus delivered directly to connected impervious surfaces cannot be captured in soil. | ||
+ | **Another important distinction between urban and agricultural systems is that infiltrated water in tile-drained systems may be captured by tiles and delivered directly to surface waters. Underdrained practices in urban areas may behave similarly, though the water from an underdrain is typically delivered back to the stormwater conveyance system. | ||
==Sources of dissolved phosphorus in runoff== | ==Sources of dissolved phosphorus in runoff== |
This page provides a discussion of dissolved phosphorus in stormwater runoff, its sources, and strategies for managing dissolved phosphorus. While the focus is on urban runoff, the basic principles are applicable to agricultural runoff.
Phosphorus in water is often classified as dissolved (soluble) or particulate (attached to or a component of particulate matter) phosphorus. This nomenclature is somewhat ambiguous, however, as dissolved phosphorus consists of multiple forms of phosphorus, including phosphorus attached to other materials.
References for phosphorus forms and testing includes the following.
Dissolved phosphorus is considered to be more bioavailable than particulate forms of phosphorus. Below is a summary of some studies on bioavailability of phosphorus.
There are insufficient data to support recommended event mean concentrations (emcs) of dissolved phosphorus for different land uses. The following table provides a summary of data we felt is appropriate for selecting an emc for dissolved phosphorus. The table does not include data for runoff from agricultural systems. Agricultural runoff is not the focus of this manual and the dynamics of phosphorus transport in agricultural systems are likely to vary widely with soil, crop, season, and phosphorus inputs. See the discussions below on dissolved phosphorus fractions in runoff and management strategies.
Summary of dissolved phosphorus event mean concentrations from various studies. There is inadequate information to provide recommended emcs for different land uses.
Link to this table
Study | Land cover/land use | Range (mg/L) | Mean | Median | Number of samples |
---|---|---|---|---|---|
Dallas-Fort Worth1 | Commercial | 0.01-0.47 | 0.09 | 0.06 | 42 |
Dallas-Fort Worth | Industrial | 0.03-0.45 | 0.14 | 0.09 | 63 |
Dallas-Fort Worth | Residential | 0.04-0.84 | 0.25 | 0.21 | 77 |
Forth Worth2 | Transportation | 0.11 | 28 | ||
Twin Cities3 | Mixed | 0.01-1.4 | 0.2 | 0.15 | 147 |
Madison4 | Medium density residential | 0.52 | 0.61 | 25 | |
Madison4 | Medium density residential | 0.4 | 0.14 | 25 | |
Madison4 | Medium density residential | 0.14 | 0.04 | 25 | |
Madison4 | Medium density residential | 0.05 | 0.03 | 25 | |
Madison4 | Medium density residential | 0.04 | 0.02 | 25 | |
Madison4 | Medium density residential | 0.03 | 0.02 | 25 | |
Madison4 | Medium density residential | 0.04 | 0.02 | 25 | |
Madison4 | Medium density residential | 1.54 | 0.81 | 25 | |
Madison4 | Medium density residential | 0.12 | 0.08 | 25 | |
Madison4 | Medium density residential | 0.11 | 0.07 | 25 | |
Madison4 | Medium density residential | 0.11 | 0.07 | 25 | |
US EPA Nurp Study5 | Residential | 0.143 | |||
US EPA Nurp Study5 | Mixed | 0.056 | |||
US EPA Nurp Study5 | Commercial | 0.08 | |||
US EPA Nurp Study5 | Open | 0.026 | |||
New York6 | Residential | 0.20 | 738 | ||
New York6 | Commercial | 0.18 | 323 | ||
New York6 | Industrial | 0.16 | 325 | ||
New York6 | Open | 0.16 | 44 | ||
Capitol Region Watershed District7 | Mixed | 0.020 - 0.888 | 0.073 | 0.052 | 89 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.565 | 0.108 | 0.087 | 120 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.506 | 0.074 | 0.059 | 112 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.361 | 0.073 | 0.053 | 121 |
Capitol Region Watershed District7 | Mixed | 0.005 -- 0.182 | 0.019 | 0.012 | 195 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.758 | 0.102 | 0.072 | 69 |
Capitol Region Watershed District7 | Mixed | 0.020 - 1.10 | 0.072 | 0.053 | 115 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.60 | 0.099 | 0.057 | 113 |
Capitol Region Watershed District7 | Mixed | 0.020 - 0.499 | 0.071 | 0.046 | 138 |
1Urban Stormwater Quality, Event-Mean Concentrations, and Estimates of Stormwater Pollutant Loads, Dallas-Fort Worth Area, Texas. 1992–93 Stanley Baldys III, T.H. Raines, B.L. Mansfield, and J.T. Sandlin U.S. Geological Survey Water-Resources Investigations Report 98–4158.
2Computed and Estimated Pollutant Loads, West Fork Trinity River, Fort Worth, Texas, 1997. United States Geological survey. Water Resources Investigations Report 01–4253
3Brezonik and stadelman. 2002. Analysis and predictive models of stormwater runoff volumes, loads, and pollutant concentrations from watersheds in the Twin Cities metropolitan area, Minnesota, USA. Water Research Volume 36, Issue 7, Pages 1743-1757
457.Waschbusch, R.J., W.R. Selbig, and R.T. Bannerman. 1999. Sources of phosphorus and street dirt from Two Urban Residential Basins in Madison, Wisconsin, 1994-95. USGS Water-Resources Investigation Report 99-4021
5U.S. EPA. Results of the Nationwide Urban Runoff Program. 1983. Volume I: Final Report. PB84-185552
6New York State Department of Environmental Conservation. August 2003. Stormwater Management Design Manual. Chapter 5 - Acceptable Stormwater Management Practices.
7Outfall monitoring data for Villa Park, Trout Brook East, Trout Brook West, Trout Brook Outlet, St. Anthony, Phalen Creek, Como 3, Como 7, and East Kittsendale
Another consideration is the fraction or percent of total phosphorus in runoff that is in dissolved form. A more complete discussion of this is found here, including literature references. The data on phosphorus fractionation is limited, but the following general statements can be made.
Effectiveness of stormwater BMPs in treating dissolved phosphorus (DP) | ||
BMP | Effectiveness | Comment |
Infiltration practices | Effective | DP may be transported to groundwater, but this generally represents a low risk to aquatic environments |
Biofiltration (includes tree trenches) | Ineffective | Some DP removal occurs through plant uptake but phosphorus is typically released from the media |
Enhanced biofiltration | Effective | In properly designed and maintained systems, iron, aluminum, and calcium adsorb DP |
Swales designed for filtration | Ineffective | Addition of engineered media with a low phosphorus concentration may enhance removal through infiltration and biological uptake |
Constructed ponds | Limited | Some biological uptake may occur, but as sediment builds in ponds, DP release may occur |
Constructed wetlands | Limited | Some biological uptake and immobilization in sediment may occur |
Green roofs | Ineffective | Typically leach DP from engineered media during the first several years after construction |
Street sweeping | Effective | Most effective when done at times when coarse organic particles (e.g. from leaves) are targted |
Pollution prevention | Effective | Focus on organic sources (e.g. yard debris), animal waste, detergents, fertilizer |