EVALUATION OF INFILTRATION-BASED GREEN INFRASTRUCTURE GEOCHEMICAL RESPONSE TO SEASONAL CHANGES IN PITTSBURGH, PA AND IMPLICATIONS FOR CHEMICAL FLUX

By 2030, urban land cover is projected to increase by 180% globally and the UN predicts that about 60% of the world’s population will live in urban areas. Urbanization dramatically alters local hydrology, generating hazards such as flooding and landslides and increases metal contamination from traffic and industrial emissions. Infiltration-based green infrastructure is designed to capture storm water runoff and reroute it into surrounding soils and groundwater thus reducing surface runoff. While some research has studied the impacts of road salt pollution, little is known about the patterns of dissolved metal concentrations that occur within these structures and resultant impacts to roadside environments. This work uses changes in dissolved metal concentrations within the infiltration trenches and local groundwater to evaluate trench function and measure dissolved metal transport from the trench systems. Several interesting patterns emerged: 1) The relatively slow infiltration rates increase with the onset of the growing season and decrease again during the winter on an annual basis. 2) The Ca/Sr ratio measured in the trenches changes seasonally, suggesting a transition in water dominant sources from road runoff in the summer to groundwater in the winter. These results are previously undocumented in roadside infiltration trenches, and will clarify the geochemical and hydrological impacts of infiltration based systems.