Water Resources Research Act Program

Details for Project ID 2019MD129B

Why is sulfate elevated in (sub)urban watersheds? Fingerprinting sources of sulfate in forested, suburban, and urban streams

Institute: Maryland
Year Established: 2019 Start Date: 2019-03-01 End Date: 2020-02-28
Total Federal Funds: $6,895 Total Non-Federal Funds: $13,796

Principal Investigators: Maya Gomes

Abstract: Sulfate concentrations in suburban and urban streams are elevated relative to forested streams in Maryland. Historically, the majority of the excess sulfate in stream water in the mid-Atlantic came from atmospheric deposition, which caused stream water acidification. Regulations on sulfur dioxide emissions from power plants put in place ~30 years ago have reduced rates of atmospheric sulfate deposition. However, the decrease in sulfate levels in streams in unglaciated regions is less than would be expected due to decreased atmospheric deposition. In Maryland, (sub)urban streams with high sulfate are not substantially more acidic than streams with lower sulfate concentrations, implying that atmospheric deposition is not the source of sulfate in these streams. We hypothesize that local anthropogenic inputs of sulfate from road salt, soil treatments, septic systems, or concrete weathering are causing elevated sulfate levels in the (sub)urban streams. In order to evaluate how [SO42-] influence stream acidity and nutrient loading in Maryland, we need to understand the sources and transport of sulfate. Here, we propose to use sulfate sulfur and oxygen isotope signatures to fingerprint the sources of sulfate to forested, suburban, and urban streams and conduct soil leaching experiments to determine how sulfate sorbed to soil contributes to stream water sulfate during baseflow conditions and storm events. The isotope data will allow us to determine why sulfate concentrations are elevated in (sub)urban streams and how excess sulfate from (sub)urban sources influences stream acidification and nutrient levels. The results of this work will be shared with scientists, engineers, and technicians in water resources fields via presentations at the Annual Meeting of the Maryland Water Monitoring Council and other professional meetings and publications in peer-reviewed journals in order to improve our knowledge of how inputs of sulfate from different sources affect water quality.