Contamination characteristics in runoff fractions from a nuclear facility in São Paulo, Brazil

Abstract

Stormwater runoff may act as a nonpoint source of pollution and, in urban environments, contributes to the degradation of aquatic ecosystem quality. In this study, we examined the influence of runoff characteristics on the export of total solids and total metals, as well as pH and conductivity responses during rainfall events. In 2017 and 2018, 12 rain events were monitored at four sampling stations in a parking lot located at the Nuclear and Energy Research Institute (IPEN/CNEN) in São Paulo, Brazil. A four-chamber integrated collector allowed the sequential and temporal assessment of runoff evolution. The runoff composition followed the order: Ca > K > Mg > Si > Al > Fe > Na > Zn > Mn > Sr > Ti > Mo > V > Cu > B > Pb > Ni > Ce > Sb > Cr > La > U > Th > Cd. Total solids, Al, and Fe concentrations exceeded Brazilian water quality standards. Principal component analysis identified elemental clusters associated with facility activities, soil, traffic, and atmospheric deposition sources. Our results show that runoff characteristics can be differentiated according to pollutant sources. Seasonal variation, rainfall intensity, air masses of oceanic or continental origin, spatial distribution within the monitoring area, and the intensity of the first flush must be considered to disentangle elemental clusters and pollution source contributions. During winter, continental air masses were associated with higher concentrations of heavy metals in surface runoff. Spatial variations without seasonal influence were observed for U, Th, La, and Ce.