NUTRIENT CONTAMINATION FROM NON-POINT SOURCES: DISSOLVED NITRATE AND AMMONIUM IN SURFACE AND SUBSURFACE WATERS AT EKU MEADOWBROOK FARM, MADISON COUNTY, KENTUCKY
Nitrate was the dominant dissolved nitrogen species whereas ammonium was often absent in water samples. Nitrate levels were typically <2 mg/L N- N- NO3 with the largest values between 7.0 and 14.3 mg/L. Springs and some runoff samples had higher nitrate values. Ammonium generally ranged between 0.0 and 0.5 mg/L N- NH4 with concentration spikes between 2.0 and 4.3 mg/L, but from no consistent source.
Dissolved nitrogen concentration values responded to rainfall. Generally, nitrate concentrations increased more than ammonium concentrations during wetter periods. Spring samples maintained higher nitrogen concentrations regardless of different rainfall conditions.
Lastly, nitrate contamination was significantly lower than composite national values from streams draining agricultural lands, whereas ammonium was about equal to the median national average. Median nitrate concentration was ~1.8 mg/L N- NO3 compared to the national value of ~2.8 mg/L, whereas the value for pristine streams is 0.24 mg/L N- NO3 (Dubrovsky et al., 2010). Median ammonium values from both data sets are ~0.1 mg/L N- NH4; the national value from pristine streams is ~0.025 mg/L N.