Lessons Learned from a Pilot Study of the Relationship Between Rainfall and Levels of Contaminants in Water Bodies Adjacent to Superfund Sites on Long Island, New York, USA

Rainfall and groundwater fluctuations may influence the migration or dilution of contaminants from US Superfund sites. This pilot study was designed to provide empirical data on relationships between rainfall and contaminant concentrations in water near Superfund sites. Four Superfund sites on Long Island, New York were selected to represent a range of contaminant profiles and hydrogeologic conditions. Baseline samples were collected in December 2022, with subsequent samples obtained following major storms and seasonally through September 2023. Samples were collected on 11–24 different days across the sites and measured for metals and 1,4-dioxane. Overall, we observed few consistent associations between rainfall and contaminant concentrations across sites. Two trends, however, were noted: (1) At Gowanus Canal, a surface water site, there was a negative association between rainfall and contaminant concentrations using same-day or prior-day rainfall; and (2) in a treatment well near Lawrence Aviation, negative associations were observed between prior month’s rainfall and contaminant concentrations. Rainfall appeared to dilute contaminant concentrations at two of the four Superfund sites. Given the increased frequency and intensity of extreme rainfall events, it is important to continue probing links between rainfall and contaminants near Superfund sites.