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Urban streams and rivers have chronic bacteria contamination in the United States, coming from multiple sources, following a variety of flowpaths to the waterway, and with differing downstream fates. Bacteria from human sewage, estimated through measures of Escherichia coli, pose the highest risk to human health. We analyzed four years of E. coli monitoring by community science groups to look for spatial and temporal drivers of E. coli densities in watersheds in the urban core of metro Atlanta, GA, with a wide range of racial and economic diversity as well as persistent patterns of segregation and racialized inequality. These watersheds are spaces of environmental injustice, with disproportionate impacts for lower-wealth and predominantly Black communities from flooding, soil contamination, and air pollution. While there were minimal differences in E. coli between watersheds with different Black and white populations, individual sites could be identified as hot and cold spots of contamination. Storm events increased E. coli at most sites, indicating a combination of runoff and sediment-sorbed E. coli explains about 50% of the temporal variability in E. coli densities. Long-term median E. coli levels were not strongly correlated to land cover or socio-demographic characteristics of the contributing watershed, but E. coli variability was lower in less densely urbanized areas. Temporal and spatial distributions of E. coli are controlled by complex interactions between sources and hydrologic transport that vary across watersheds. While direct correlations to racial demographics were not observed, the interactions between sewage as one environmental harm and the many others (air quality, soil quality, prison-industrial complex, etc.) present in minority and low-income urban communities emphasize the oversized burden environmental justice communities carry. 

Major ion geochemistry and isotopes of nitrate for the Tapestry beaver pond in Atlanta, GA. Samples were collected from the surface from June 2019-March 2020 and from the hyporheic zone from June-August 2019. Logger data (DO and specific conductance at 10 minute intervals) were also collected from June-August 2019. Isotopes of nitrate (d15N and d18O) were measured for a subset of June-August 2019 surface and hyporheic samples. Data were used in the paper "Urban beaver dam shows hyporheic exchange helps mediate high nutrient groundwater and a high productivity pond"