LIVESTOCK GRAZING IMPACTS ON PHOSPHORUS IN A CARBONATE SPRING

Authors: Boyer, Douglas; ALLOUSH, GHIATH - VIRGINIA TECH

Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/6/2002
Publication Date: 11/3/2002
Citation: BOYER, D.G., ALLOUSH, G.A. LIVESTOCK GRAZING IMPACTS ON PHOSPHORUS IN A CARBONATE SPRING. AMERICAN WATER RESOURCES ASSOCIATION CONFERENCE PROCEEDINGS. 2002. Abstract Proceedings, p. 273.

Interpretive Summary:

Technical Abstract: Dissolved phosphorus loads in Appalachian River basins are directly related to the amount of land drained by carbonate aquifers. Typically, carbonate aquifers in Appalachia are characterized by a high secondary permeability associated with solutionally enlarged fractures and joints in the soluble bedrock. A quick and direct link exists between the surface and aquifer. Total and dissolved phosphorus concentrations were measured during base flow and storm events at a carbonate spring draining a beef cow grazed agricultural karst basin in southeastern West Virginia. Total P (TP) was determined on unfiltered samples digested with sulfuric and nitric acids. Dissolved reactive P (MRP) was determined on filtered (0.45 µm) samples. Total particulate or sediment P (TPp) was calculated as the difference between TP and MRP. MRP dominated the phosphorus load during base flow periods. TPp was nearly non-existent in base flow. During storms with sediment loads TPp dominated. Mean TP concentration during base flow periods was equal to MRP concentration (0.26 mg L-1) and TPp was negligible. Two storms in February and March 2000 demonstrate differences in fractionation of P associated with sediment loads. The February 2000 storm was characterized by a high sediment load and a peak flow of 56 m3 min-1. The March 2000 storm was characterized by a low sediment load and a peak flow of 42 m3 min-1. TPp (0.54 mg L-1) accounted for 70% of TP (0.77 mg L-1) and MRP (0.23 mg L-1) accounted for 30% of TP during peak flow of the February storm. At the peak of the March storm TPp (0.02 mg L-1) accounted for 11% of TP (0.19 mg L-1) and MRP (0.17 mg L-1) accounted for 89% of TP. Clearly sediment load is a significant factor in differentiation of P at the carbonate spring. However, it is not clear whether sediments in the spring flow were derived directly from the surface, from deeper soil layers adjacent to bedrock fractures and conduits, or from sediment stored within the karst aquifer. Management strategies to control P bound to particulates will depend on knowledge about the sources of sediments at the spring.