Citation:

Benish, S., J. Bash, K. Foley, S. Napelenok, C. Hogrefe, AND L. Linker. Modeling of Nitrogen and Sulfur Deposition in the Chesapeake Watershed and Tidal Bay: Trends and Sources. CMAS, Virtual, NC, November 01 - 05, 2021.

Impact/Purpose:

Using CMAQv5.3.2 simulations from EPA’s Air QUAlity TimE Series (EQUATES) project, we assess trends in total inorganic nitrogen and sulfur wet and dry deposition from 2002 to 2017. Special attention will be placed on the Chesapeake watershed and tidal Bay, a region that receives about a third of its annual nitrogen load from atmospheric deposition. By precipitation and bias adjusting the wet deposition fields, we demonstrate improvements in measurement-model agreement. The Integrated Source Apportionment Method (ISAM) in CMAQ will be used to quantify the contribution from emissions and source regions to nutrient loading within the Chesapeake Bay Watershed.

Description:

Excess deposition of atmospheric nitrogen compounds can have harmful effects on vulnerable aquatic and terrestrial ecosystems. Chemical transport models, such as the Community Multiscale Air Quality (CMAQ) model, can simulate atmospheric deposition of compounds not routinely measured, such as organic nitrogen, as well as provide information about deposition in locations without measurements, like over complex terrain or over water bodies. Multiyear simulations from the EPA’s Air QUAlity TimE Series (EQUATES) project provide a consistent modeling framework using CMAQv5.3.2 to provide stakeholders and partners with key information necessary for ecological evaluations and nutrient assessments. In this presentation, we assess trends of total inorganic nitrogen and sulfur from 2002-2017 in nine climatically consistent regions within the contiguous United States. We focus specifically on the Chesapeake watershed and tidal Bay, an area naturally sensitive to atmospheric nutrient deposition due to its geography and home to over 18 million residents. We present precipitation and bias adjustment of wet deposition fields to demonstrate improvements in modeling wet deposition compared to the National Atmospheric Deposition Program’s (NADP) National Trends Network (NTN) wet deposition measurements and show how annual total nitrogen and sulfur budgets change over time and spatially. By applying the Integrated Source Apportionment Method (ISAM) in CMAQ to the Chesapeake Bay airshed, we identify key source regions and emission sectors to quantify their contribution to nutrient loading, one of the first ISAM applications for deposition. Preliminary results suggest mobile sources are responsible for ~24% of the total oxidized nitrogen deposition and non-poultry manure contributes ~17% to the total reduced nitrogen deposition in Winter 2016 throughout the Chesapeake Bay Watershed.

Record Details: