Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts

Cation Chemistry in Baltimore Streams
Mehta, Amar
Co-Authors: Amar Mehta, Daniel Bain, Ken Belt, Peter Groffman, Sujay Kaushal, Rich Pouyat
Abstract: Urban streams are degraded by a variety of physical and chemical factors including impervious surfaces, sewer cross-connections, and multiple chemical contaminants. Ecological studies sometimes ignore water chemistry beyond macronutrients, a strategy that can miss important stoichiometric clues. We subsampled the BES water archive of biweekly stream samples and examined a suite of elemental concentrations (e.g., Na, K, Mg, Ca, Si, and S) using the ICP-AES at the University of Pittsburgh. These chemical tracers provide additional constraints, improving our understanding of solute source and basin hydrology. They are also indicative of many processes including chemical weathering of bedrock, human inputs to surface waters, and the role and retention of atmospheric inputs in urban watersheds. Analysis of this data identifies interesting and important trends in stream water chemistry. For example, while we expect chemical weathering to be high in "agricultural" basins from constant disturbance of the soil profile, weathering indicators are also elevated in some of our most impermeable basins (e.g. Dead Run). In addition, major cation trends seem to mirror nutrient concentration trends, suggesting important inputs of major cations from sanitary sewer/stream cross-connections. While most base cations are certainly not limiting nutrients, constant disruption of base cation cycles will have ecosystem consequences.