Nutrient contamination from non-point sources: Dissolved phosphate in surface and subsurface waters at EKU Meadowbrook Farm, Madison County, Kentucky

Farms are non-point sources for nutrient contaminants that drain into watersheds and contribute to eutrophication and other environmental problems. EKU’s Meadowbrook Farm raises both crops and livestock, causing dissolved phosphorus in the form of orthophosphate (PO43-) from fertilizer and animal manure to enter surface and subsurface waters, eventually flowing into Muddy Creek, a tributary of the Kentucky River. We sampled surface water, springs, and water from French drains that emanate from the farm, and also sampled Muddy Creek waters from May through August 2016. Typically, 1 to 2 days after sampling, we colorimetrically measured dissolved orthophosphate concentration using the established ascorbic acid method with general accuracy and precision of ~0.1 mg/L. Phosphate values measured from the farm are usually low compared to other nutrient and national phosphate data. Phosphate concentrations generally range from 0 to 0.2 mg/L P-PO4 with higher concentrations of 0.5 to 2.7 mg/L P-PO4 occurring sporadically. Phosphate concentrations are proportionately lower than nitrate values. Except for spring waters, we saw little difference in phosphate concentration between different sample sources. A major sub-watershed typically had increased levels of phosphate, especially on 24 May (2.7 mg/L P-PO4). Overall patterns of phosphate concentration were similar whether sampling during periods with little or no rainfall, or when following rain events. An exception occurred on 24 June, when the sub-watershed had a value of 0.5 mg/L immediately following a rain event. The median value of orthophosphate from Farm surface waters was 0.02 mg/L P-PO4; nationally the level is ~0.1 mg/L P-PO4.https://encompass.eku.edu/swps_undergraduategallery/1111/thumbnail.jp