Major ions in urban streams: a look at concentrations over time and across land cover

Abstract

Major ions in urban streams remain understudied, despite the connections between ion concentrations and stream ecosystem health. The concentrations and variability of major ions were characterized for streams in the Maryland Piedmont with impervious surface cover (ISC) ranging from 0–21%. The five study watersheds have similar bedrock geology and thus would have similar major ion chemistry in the absence of ISC and urbanization. Water samples have been collected weekly since 1998 in the watersheds as part of the Baltimore Ecosystem Study (BES). Anion concentrations measured by BES for these weekly samples and cation concentrations from 100-200 samples per stream measured at TU were used to analyze the effects of ISC and temporal trends for major ions. Overall, ion concentrations become more elevated and more variable as the percentage of ISC in a watershed increases. Additionally, major ion concentrations for watersheds with ≥1% ISC rose substantially from 1998–2014.