Evans, Hunter R., 2017. Nutrient contamination from non-point sources: Dissolved phosphate in surface and subsurface waters at EKU Meadowbrook Farm, Madison County, Kentucky. Undergraduate Thesis, Department of Geosciences, Eastern Kentucky University. May 2017.
Farms are non-point sources for nutrient contaminants that drain into waterways and contribute to eutrophication and other environmental problems. EKU’s Meadowbrook Farm raises both crops and livestock, contributing dissolved phosphorus in the form of orthophosphate (PO43-) to surface and subsurface waters, eventually flowing into Muddy Creek, a tributary of the Kentucky River. We sampled springs, surface water from the farm, tile drains, and Muddy Creek waters from May through August 2016. One to two days after sampling, we measured orthophosphate concentration using the established colorimetric, ascorbic acid method and a UV-VIS spectrophotometer with general accuracy and precision of ~0.1 mg/L (ppm).
Phosphate concentrations are generally low when compared to nitrate ranging from 0 to 0.1 mg/L P-PO4 with higher concentrations of 0.5 to 2.7 mg/L P-PO4 occurring sporadically. With some exceptions, we saw little difference in phosphate concentration between different sample sources whether spring water, water from subsurface drains, surface waters flowing over the Farm, or Muddy Creek waters. Overall patterns of phosphate concentration were similar whether sampling during periods with little or no rainfall, or periods following rain events. However, one sub-watershed draining the Farm had increased levels of phosphate on 24 May (up to 2.7 mg/L P-PO4), and on 24 June (0.5 mg/L P-PO4), immediately following a significant rain event.
Overall, Farm and Muddy Creek waters had lower median dissolved orthophosphate (0.02 mg/L P-PO4) than runoff from agricultural areas nationally (0.15 mg/L P-PO4). Subsurface water from springs had a median level of phosphate (0.04 mg/L P-PO4) higher as compared to springs nationally (<0.01 mg/L P-PO4).