Measurement of air-surface exchange of speciated nitrogen and sulfur compounds in a coastal environment

Greg Beachley1, John T. Walker2, Ian Rumsey3, Mike Larsen4, Joseph Niehaus5 and Monica Mullis6

Ecosystem exposure and vulnerability to atmospheric deposition of nitrogen and sulfur compounds is assessed by the United States Environmental Protection Agency’s (U.S. EPA’s) primary regulatory tool, the Community Multiscale Air Quality Model (CMAQ). Observational datasets are required for the development of the dry deposition algorithms used in CMAQ. These deposition datasets are influenced by local environmental conditions such as meteorology, atmospheric chemistry, and surface conditions. There is a paucity of direct deposition datasets in coastal environments, which often have different environmental conditions than inland locations.

This study builds on the previous work of Rumsey and Walker, 2016 to deploy the Monitor for AeRosols and GAses (MARGA) to directly measure hourly fluxes of gases (NH3, HNO3, HNO2, and SO2) and aerosols (NH4+, NO3-, and SO42-) above a grassy field. The MARGA on-line ion-chromatography analyzer was deployed in the same setup with two samplers at 4-m and 1-m to directly measure concentration gradients over a grassy field in a coastal environment near Charleston, South Carolina from mid-May through June 2017. The multi-species concentration gradient measurements are used in conjunction with the micrometeorological aerodynamic gradient method to determine air-surface exchange fluxes for each species to further characterize dry nitrogen and sulfur deposition processes in a coastal environment and assess how they differ from inland deposition processes. This communication highlights preliminary results for species concentration gradients and meteorological data measured this summer.

 

1US EPA, beachley.gregory@epa.gov
2US EPA, walker.johnt@epa.gov
3US EPA, rumsey.ian@epa.gov
4College of Charleston, larsenml@cofc.edu
5College of Charleston, jdniehau@cofc.edu
6College of Charleston, mullis@g.cofc.edu