The US Environmental Protection Agency (EPA), National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), Southern Company, and the Electric Power Research Institute (EPRI) are together contributing more than $20 million in research funding to support the SouthEast Atmosphere Study (SAS). EPA is also contributing staff scientists to work as part of this effort.
SAS involves dozens of other domestic and international research institutions, and is one of the largest North American air quality and climate studies in decades. It is a collaboration that brings together resources and facilities from NSF, NOAA, EPA, and EPRI.
SAS is the “umbrella” for a set of other projects: NOMADSS (Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks); SOAS (Southern Oxidant & Aerosol Study); NAAMEX (North American Airborne Mercury Experiment); TROPHONO (TROPospheric HONO); and SENEX (Southeast Nexus). SAS’s main purpose is to ensure that the objectives of the individual projects are coordinated.
The field phase for the SAS began 1 June 2013 and runs through 15 July 2013 and is generally focused in the southeastern United States. All airborne platforms (i.e., NSF/NCAR C-130, NOAA WP-3D, Purdue Duchess, and Stonybrook Long-EZ) and ground based facilities (i.e., Centreville and Alabama Aquatic Biodiversity Center (AABC), Alabama; Look Rock, Tennessee; and Research Triangle Park (RTP), North Carolina) are involved in the SAS.
NOMADSS integrates three proposed studies: the Southern Oxidant and Aerosol Study (SOAS), the North American Airborne Mercury Experiment (NAAMEX), and the TROPospheric HONO (TROPHONO). The field campaigns for the three are being merged on the C-130 platform.
SOAS objectives include the direct quantification of VOC, ozone and NOx surface fluxes and the reconciliation of differences with “blank-down” emission estimates. It seeks a better understanding of HOx/NOx/ozone/organics/aerosol distributions, sources and sinks.
The primary goals for NAAMEX are to: (1) constrain emissions of mercury from major source regions in the United States, and (2) quantify the distribution and chemical transformations of speciated mercury (Hg) in the troposphere.
These goals will be fully met in the merged project. The merger represents a significant opportunity to conduct detailed sampling in the most concentrated Hg source region in North America as well as flights into the middle and upper troposphere where models suggest a significant source of oxidized Hg. The NOMADSS payload includes the key NAAMEX measurements, plus fast VOC measurements that will help in source identification. The data on HONO will provide an additional constraint on oxidation processes, which are poorly understood for Hg.
The objectives for TROPHONO are: (1) to establish HONO (nitrous acid, an important daytime radical) distribution and budget in various air masses (continental and oceanic background air masses, and urban/industrial plumes) in the troposphere; (2) to collect bulk aerosol samples for laboratory photochemical experiments to measure photolysis rate constant of particulate nitrate leading to HONO and NOx productions; (3) to quantify p-NO3 as a daytime HONO source and a re-NOx-ification pathway in the troposphere; (4) to examine HONO production from photo-enhanced heterogeneous NOx reactions in urban/industrial plumes; and (5) to investigate HONO dark formation/nighttime accumulation and morning-hour photolytic decay in the PBL (planetary boundary layer, the lowest part of the atmosphere) and in the FT (free troposphere, the upper part of the troposphere).
The SENEX project goal is to use the NOAA P-3 aircraft to (1) to sample air masses that contain a different mixture of emissions (urban, power plant, forest), (2) to follow these air masses as they are transported and chemically transformed in the atmosphere, and (3) to measure the vertical distribution of trace gases and aerosol in the atmosphere, in order to answer five specific science questions:
What are the emissions of aerosol, aerosol precursors and greenhouse gases in the SE US?
What is the composition and distribution of aerosol in the SE US?
What are the formation mechanisms of secondary species (ozone, sulfate and organics) in the SE US?
Which deposition processes are critical for determining atmospheric concentrations of aerosol, ozone and NOy?
What are the climate-relevant properties of aerosol in the SE US?
EPA is providing more than $4.3 million in grants to 13 institutions as part of SAS. Researchers will have access to NOAA and NSF resources such as aircraft and towers to capture information about organic aerosols at multiple heights in the air and on the ground at the same time.
The Southeastern Aerosol Research and Characterization (SEARCH) Network, a collection of air quality monitoring stations throughout the southeastern United States developed by EPRI and Southern Company will be collecting ground measurements, and providing access to current and historical air quality data and analyses. The researchers will use the collected data, and high quality models built from this data, to address emerging air pollution issues.