The Geospatial Monitoring of Air Pollution (GMAP) and its Role in Addressing Critical Scientific Knowledge Gaps in Air Quality and Source Emissions

Justin Coughlin1, Marta Fuoco2 and Scott Hamilton3

The U.S. EPA Geospatial Mapping of Air Pollution (GMAP) project has been utilized to determine stationary sources’ influence on surrounding air quality.  The mobile GMAP platform allows for air quality monitoring at ~1 sec resolution coupled with mobile 2D anemometer measurements (vehicle speed corrected) and real-time GPS coordinates.  Additionally, stationary measurements are able to be conducted to determine source apportionment influences on monitor readings.  Currently, the GMAP system is equipped with a cavity ring-down spectroscopy (CRDS) that is able to measure hydrogen sulfide (H2S) and methane (CH4) and a multi-pass UV optical spectrometer that can measure benzene-toluene-ethylbenzene-xylene (BTEX), sulfur dioxide (SO2), oxides of nitrogen (NOx), ozone (O3), formaldehyde, and styrene.  During stationary measurements, a 3D anemometer is also attached to provide 3D wind measurements used to determine emissions flux estimates from ground level emission sources.

The GMAP platform has primarily been utilized to assess air quality impacts near facilities such as landfills, wastewater treatment centers, oil and gas processes, and paper mills.  With the importance of ammonia (NH3) as a precursor in particulate matter (PM) formation and the growing regulatory interest of decreasing NH3 emissions to limit PM pollution in the U.S., the mobile geospatial measurement systems may be useful in both quantifying emission rates and assessing plume size and variability, helping to fulfill critical knowledge gaps of NH3 emissions and their role in regional PM concentrations.  CRDS instruments are able to measure air pollutants at a high degree of accuracy and precision with a relatively low residence time.  NH3-measuring instrumentation is being explored as a possible addition to the GMAP system.


1US EPA Region 5,
2US EPA Region 5,
3US EPA Region 5,