Dr. Herndon is a principal research scientist in the Center for Atmospheric and Environmental Chemistry. Since joining Aerodyne in 1999, his research interests have involved using laboratory and field instruments together with modeling studies to further the elucidation of atmospheric processes.He is the author or co-author of over 40 archival publications atmospheric science and physical chemistry.
Aerodyne Mobile Laboratory
Research and commercial instruments are installed into the Mobile Laboratory to collect data while in motion for plume characterization, area mapping or portable deployment for photochemistry and transport experiments.
Instruments on the Mobile Laboratory
New York City – 2000/2001 & 2009
In the 2000/2001 campaign, the mobile laboratory was directed to chase Metro Transit Authority (MTA) and other passenger bus vehicles over their normal routes and perform emissions characterization. The study was hosted by the site at Queens College. In 2009, the mobile laboratory revisited New York and characterized the combined emissions from the "line source" represented by the highways and examined the impact of these emissions on ambient aerosol loadings as function of distance from the highway.
Mexico City – 2002, 2003, 2006
In Mexico City, the mobile laboratory was used to collect on-road 'mixed fleet' emissions as well as perform dedicated emissions 'chase' sampling for different vehicle types. When not operated on road, the mobile laboatory was used as a portable platform for both gaseous and particulate ambient pollutant measurements. Forecast meteorology was used to position the mobile laboratory at the sites where ozone production was anticipated to be the largest. These campaigns observed a clear and dramatic association of photochemical ozone with urban photochemical secondary organic aerosol production.
Mexicali – 2005
In Mexicali, several fixed point emission sources were characterized, including feed lots, power plant plumes and the emissions from street side food vendors. On road vehicle exhaust emissions were also characterized. Additionally, the mobile laboratory conducted experiments to compare ambient concentration measurements with data from other stations.
APEX and AAFEX – 2004 – present
The APEX and AAFEX campaigns have used the mobile labotory to significantly advance the understanding of aircraft emissions. The work has produced a refined understanding of primary soot, primary condensable organic and sulfate aerosol particulate matter including the processes important in the initial atmospheric dilution of aircraft engine exhaust. This research has also quantified the emissions performance benefits from using alternative fuels in aircraft engines. This work has greatly informed domestic policy and world wide commercial engine emissions certification practices.
The Airport Cooperative Research Program (ACRP) 02-03a, has determined how the aircraft engine emissions of hazardous air pollutants (HAPs) vary with engine state and ambient temperature. This work produced a simple model to quantify HAP emissions inventory estimates under real world conditions. This model allows airport environmental planners to quantify the emissions benefit from proposed changes in airort operational behavior at airports.
The ACRP project 02-17 is underway to characterize the effective particulate emissions from non-engine aircraft sources, such as auxiliary power units, abraded tire (from touchdown smoke) and brake wear.