Background

1. Variation of Nitrates and Calcium in a Karst Spring, Nolte, PA Old water Young water Terefe Mazengia, Laura Toran, Jennifer Tancredi and Szilvia Mathe-Puckey Temple University Dept of Geology Why does Ca vary more than NO3 and other ions? Conclusions • Nitrate increased after the growing season ended. Evidence of diffuse recharge • Calcium was variable. Evidence of mixing different sources of water • Other ions remained constant while calcium varied. Evidence that mixing is probably young conduit with young matrix water (not old/young) • BOTH DAILY AND SEASONAL MONITORING ARE NEEDED TO IDENTIFY FLOW VARIATIONS Problem NO3 variation Effect of rainfall on Ca Methods • Conductivity and water level for 18 months • ISCO samples collected once a day in Oct/Nov 2003 and Jan/Feb 2004 • Bi-monthly samples & pH measurement during site visits • Samples analyzed on ion chromatograph What does geochemical variation in spring discharge tell us about sources of recharge? • HYPOTHESIS 1 • “Old” water may be young too, only slightly older from the matrix • Influenced by calcite equilibrium in the matrix • HYPOTHESIS 2 • Calcite ppt in the conduits controls the Ca concentration • Matrix has less influence Background • Nolte Spring is a former water supply, closed due to high turbidity • It discharges from two 10 cm diameter conduits in carbonate rock (Epler Fm) • Approximately 25 L/s • Land use in the area is agricultural ISCO Samplers Nitrate increased after the growing season ended, when plant uptake was decreased Calcite undersaturated except during 2002 drought Storms may mix old matrix water and young conduit water Sensors in spring mouth Support from Hydrologic Sciences Program of the National Science Foundation is gratefully acknowledged Location, Well House Calcite appears in discharge sediment, probably precipitated further back in conduit Seasonal PCO2 variation shows variation in mixing and recharge through soil zone Ion Chromatograph