You are here:
Human-accelerated weathering increases salinization, major ions, and alkalinization in fresh water across land use
Citation:
Kaushal, S., S. Duan, T. Doody, S. Haq, R. Smith, T. Newcomer Johnson, K. Delany Newcomb, J. Gorman, N. Bowman, P. Mayer, K. Wood, K. Belt, AND W. Sack. Human-accelerated weathering increases salinization, major ions, and alkalinization in fresh water across land use. APPLIED GEOCHEMISTRY. Elsevier Science Ltd, New York, NY, 83:121-135, (2017).
Impact/Purpose:
Recent events in Flint, MI, for example, emphasize the critical importance of understanding the impact on water quality water of geologic weathering and subsequent decay of urban and drinking water infrastructure. Our study shows that such geochemical process have led to long-term increasing trends in weathering products including alkalinity, hardness, calcium (Ca), magnesium (Mg), and sodium (Na) in the drinking water supply of Baltimore, Maryland, USA. We explored mechanisms driving these long-term trends and analyzed longitudinal concentrations of weathering products in Baltimore streams, using both laboratory experiments and field monitoring. Major ions (DIC, Ca, Mg, Na, Si) and pH were significantly elevated in agricultural and urbanized streams and increased significantly with impervious surface cover and distance downstream. Human-accelerated weathering, anthropogenic salt inputs, and organic matter oxidation significantly increased major ions, salinization, and alkalinization in fresh water, all of which can have major impacts on aquatic biota and drinking water quality due to flux of toxic metals and corrosion of piped infrastructure. Our study demonstrates the need for monitoring geochemical weathering processes to assess water quality risks. This study was not done a priori under an existing RAP task but parallels the focus of SSWR 4.03 - Science to Improve Nutrient Management Practices, Metrics of Benefits, Accountability and Communication
Description:
Human land use increases transport of dissolved inorganic carbon and major ions in watersheds due to the combination of easily weathered materials in watersheds and anthropogenic inputs. Here, we show that dissolved inorganic carbon (DIC), alkalinity, and major ions are significantly elevated in streams draining agricultural and urbanized watersheds compared with minimally disturbed watersheds. Firstly, we documented long-term increasing trends in weathering products including alkalinity, hardness, calcium (Ca), magnesium (Mg), and sodium (Na) in the drinking water supply of Baltimore, Maryland, USA. Secondly, we analyzed concentrations of weathering products across a land-use gradient at the Baltimore Long-Term Ecological Research (LTER) site to explore drivers of these long-term trends. Thirdly, we analyzed longitudinal concentrations of weathering products in Baltimore LTER streams to better understand downstream impacts. Finally, we investigated the potential for weathering of impervious surfaces to influence water quality in these watersheds using both laboratory experiments and monitoring at storm drain outlets. We found that concentrations of weathering products and major ions (including DIC, Ca, Mg, Na, Si) and pH were significantly elevated in agricultural and urbanized streams and increased significantly with impervious surface cover and distance downstream. Laboratory experiments showed potential to increase pH and DIC concentrations in stream water due to weathering of impervious surfaces. Monitoring at urban storm drain outlets showed DIC concentrations over 10-fold greater than forest reference streams. Interestingly, high concentrations of DIC and pH were also observed downstream of urban stormwater management wetlands likely due to organic matter oxidation as an additional DIC source. Human-accelerated weathering, anthropogenic salt inputs, and organic matter oxidation significantly increase major ions and alkalinization in fresh water. Increased salinization and alkalinization of fresh water across land use can have major impacts on aquatic life, toxic metals, corrosion of piped infrastructure, and drinking water quality.
