Water quality monitoring of five karst springs within a pastureland in southwest Polk County, Missouri

The fractured nature of karst terrain makes these areas highly susceptible to contamination. Besides aquifer contamination, impaired karst springs can negatively impact the aquatic habitat of their receiving streams. Five springs of a shallow karst aquifer in southwest Polk County, Missouri, and their receiving stream were selected to construct a baseline of water quality data, using nitrate (NO (sub 3) ) as indicator. The main land use in the study area is cattle farming. Water samples were collected during a 12-month period and analyzed for pH, turbidity, Ca, Mg, HCO (sub 3) , Cl, SO (sub 4) , and NO (sub 3) . Results show that each spring had its own range of values. NO (sub 3) and Cl values were below contamination levels and only in a few instances exceeded threshold levels reported for karst areas (NO (sub 3) -N<3 mg/L; Cl<13 mg/L), implying that the number of cattle per acre is maintained at a sustainable level and leaking from the Springfield Plateau aquifer to the underlying Ozark aquifer poses a minor threat. Interestingly, NO (sub 3) and Cl did not correlate despite their common source, suggesting that they undergo different chemical and microbiological processes along their path. The yearly nitrate export from the Little Sac River was estimated as 286.8 Mg, and the maximum N load was observed in March. Monitoring of springs and streams is recommended for this environmentally fragile area.