CEE Seminar: Factoring Stream Turbulence into Global Assessments of Nitrogen Pollution
Professor of Environmental Engineering
Department of Civil and Environmental Engineering
Department of Chemical Engineering and Materials Science
University of California, Irvine
Abstract: The discharge of excess nitrogen to streams and rivers poses an existential threat to both humans and ecosystems. A seminal study of headwater streams across the U.S. (the second Lotic Intersite Nitrogen eXperiment or LINX II study) concluded that in-stream removal of nitrate is controlled primarily by stream chemistry and biology, and only weakly by stream physics. A reanalysis of these data reveals that stream physics (in particular, turbulent mass transfer across the concentration boundary layer above the streambed) imposes a previously unrecognized upper limit on the rate nitrate is removed from streams. The upper limit closely approximates measured nitrate removal rates in streams with low concentrations of this pollutant, a discovery that should inform stream restoration designs and efforts to assess the effects of nitrogen pollution on receiving water quality and the global nitrogen cycle.
Bio: Stanley Grant is a professor in the Departments of Civil and Environmental Engineering (primary) and Chemical Engineering and Materials Science (courtesy) at UC Irvine, and beginning August 2018 in the Civil and Environmental Engineering Department at Virginia Tech. He received his bachelor's degree with distinction in geology from Stanford University in 1985; and his master's degree and doctorate in environmental engineering science (with a minor in applied biology) in 1989 and 1992, respectively, from Caltech. His professional interests include human and ecosystem water security, coastal and drinking water quality, and environmental fate and transport modeling. Grant is the principal investigator and director of two center grants focused on urban water sustainability, including a $4.9M grant from the National Science Foundation Partnerships for International Research and Education (NSF-PIRE) program, and a $1.9M multicampus research award from the University of California Office of the President (UCOP).