Seasonal Variation in the Redox Zones and Biogeochemical Processes within the Constructed Wetland

This research investigation focuses on the vertical distribution of dissolved inorganic species in the pore-water affected by redox processes and seasonal changes within a small constructed wetland located at the Wright-Patterson Air Force Base. This is a follow up study to an earlier investigation (Lach, 2004) at this site in 2003. Water samples were collected from influent, effluent and three layers of the constructed wetland through a network of nested piezometers in the vertical flow wetland from June 2005 to June 2006. Onsite analysis of temperature, pH and conductivity were carried out onsite. Major anions and cations were measured by ion chromatography and ferrous iron was analyzed by spectrophotometer. In addition, the alkalinity titration was conducted. The results of this research indicate a strong likelihood of anaerobic processes such as nitrate, Fe(III) and sulfate reduction in lower and middle layers of the constructed wetland, and a potential for oxidative processes within the upper layer of the wetland. The efficiency of this system in reducing or oxidizing redox-sensitive species(electron acceptors) is affected by factors including temperature, vegetation and availability of electron donors