SPATIAL CHARACTERIZATION OF HYDROGEOCHEMISTRY WITHIN A CONSTRUCTED FEN, GREENE COUNTY, OHIO

An artificial fen environment was constructed near the municipality of Beavercreek, Ohio, The constructed wetland environment utilizes local ground-water flow patterns to maintain a high degree of water saturat ion. Chemical reactions driven by the activity of plant roots and soil microorganisms affect the spatial distribution and magnitude of hydro geochemical parameters, including alkalinity, pH, redox potential, and concentrations of Ca+2, Mg+2, total iron, NO3-, and SO4-2. The purpos e of this study is to investigate the chemical interactions between we tland plants and ground water by means of characterizing the spatial v ariation in hydrogeochemical parameters, Nested piezometers within the artificial fen are used to monitor ground-water chemistry within, and immediately adjacent to, the rhizosphere of cultivated plant species, The major reactions at the site include oxidation of organic matter b y Fe(OH)(3) and dissolution of carbonate minerals driven by high CO2 p roduction in the root zone, The relationship between alkalinity and di ssolved concentrations of Ca+2 and Mg+2 suggests that organic anions c ould also be major alkalinity contributors, Redox potential is buffere d by the reduction of Fe(OH)(3) and is typically maintained in the ran ge of 100-200 mV. This buffering effect prevents the formation of sulf ide and methane commonly found in similar wetland environments, This f inding suggests that methane production associated with rice cultivati on can be prevented by the addition of Fe(OH)(3) to rice fields.