PORE WATER GEOCHEMISTRY VARIABILITY ACROSS A BACKWATER WETLAND IN A MIXED-USE APPALACHIAN WATERSHED

Wetlands have the capacity to mitigate nutrient runoff. The Fourpole Creek watershed, adjacent to the Ohio River, is impacted by nutrient pollution from urban and agricultural land cover. To assess this impact, pore water chemistry was evaluated for elemental and isotopic tracers in the perirheic (surface water mixing) and hyporheic (ground water mixing) zones. Pore and surface water samples were collected preceding, during, and following a backwater flood pulse. The MHE Push-Point sampling method was used to collect pore water samples at 12 and 24 inches below the sediment water interface; rhizons were used to collect pore water samples at the sediment-water interface, and at 3 and 6 inches depth. Total dissolved solids, salinity, temperature, pH, and dissolved oxygen were measured with a YSI Multi-Parameter meter. Additionally, analyses were conducted for major elemental concentrations, nitrate (NO₃^-), ammonium (NH₄⁺), dissolved inorganic carbon, and dissolved organic carbon. Finally, carbon and nitrogen isotopic ratios (d¹³C and d ¹⁵N) will be analyzed on sediment cores and pore waters. Preliminary results show changes in pH downstream, potentially reflecting a decline in the conversion of NH₄⁺ to NO₃^-.