The pungent gas contributes to fine airborne particulate pollution, which endangers human health when inhaled and absorbed in the bloodstream. 

A recent study led by scientists at NASA’s Jet Propulsion Laboratory in Southern California and the nonprofit Aerospace Corporation shows how high-resolution maps of ground-level ammonia plumes can be generated with airborne sensors, highlighting a way to better track the gas. A key chemical ingredient of fine particulate matter — tiny particles in the air known to be harmful when inhaled — ammonia can be released through agricultural activities such as livestock farming and geothermal power generation as well as natural geothermal processes. Because it’s not systematically monitored, many sources of the pungent gas go undetected.  

Published in Atmospheric Chemistry and Physics in October, the study focuses on a series of 2023 research flights that covered the Imperial Valley to the southeast of the Salton Sea in inland Southern California, as well as the Eastern Coachella Valley to its northwest. Prior satellite-based research has identified the Imperial Valley as a prolific source of gaseous ammonia. In the study, scientists employed an airborne sensor capable of resolving ammonia plumes with enough detail to track their origins: Aerospace Corporation’s Mako instrument is an imaging spectrometer that observes long-wave infrared light emitted by areas of Earth’s surface and atmosphere 6 feet (2 meters) across. 

Using the instrument, which can detect ammonia’s chemical signature by the infrared light it absorbs, the authors found elevated levels of the gas near several sources, including agricultural fields, livestock feedlots, geothermal plants, and geothermal vents. Measurements in parts of the Imperial Valley were 2½ to eight times higher than in Coachella Valley’s Mecca community, which had ammonia concentrations closer to background levels. 

Though not toxic on its own in low concentrations, ammonia is a precursor to particulate matter, also known as aerosol or particle pollution. It reacts with other gases to form solid ammonium salt particles small enough to penetrate the bloodstream from the lungs. Particles under 2.5 micrometers in diameter — also known as PM2.5 — are associated with elevated rates of asthma, lung cancer, and cardiovascular disease, among other negative health outcomes. 

“Historically, more attention has focused on primary sources of PM2.5, such as auto emissions. But with significant reductions in those emissions and increasingly stringent air quality standards, there is growing interest in understanding secondary sources that form particles in the air from precursor gases,” said Sina Hasheminassab, lead author of the paper and a research scientist at JPL. “As an important precursor to PM2.5, ammonia plays a key role, but its emissions are poorly characterized and undermonitored.” 

Rising ammonia 

Previous satellite-based studies have shown rising levels of atmospheric ammonia, both globally and in the continental United States. That research revealed broad trends, but with spatial resolution on the order of tens of miles, the measurements were only sufficient to identify variation over areas of hundreds of square miles or more. 

The chemical behavior of ammonia also poses a particular monitoring challenge: Once emitted, it only stays in the atmosphere for hours before reacting with other compounds. In contrast, carbon dioxide can remain in the air for centuries. 

Planes and satellites can provide an overview of sources and the geographic distribution of emissions at a given moment. Although satellites offer wider and more recurrent coverage, airborne instruments, being closer to the source, produce higher-resolution data and can focus on specific locations at designated times.  

Those proved to be the right capabilities for the recent study. Researchers flew Mako over the Imperial and Eastern Coachella valleys on the mornings and afternoons of March 28 and Sept. 25, 2023, and took concurrent measurements on the ground with both a fixed monitoring station in Mecca operated by the South Coast Air Quality Management District (AQMD) and a mobile spectrometer developed at the University of California, Riverside. 

“The goal was to show that this technique was capable of delivering data with the required accuracy that aerosol scientists and potentially even air quality regulatory bodies could use to improve the air quality in those regions,” said David Tratt, a senior scientist at Aerospace Corporation and coauthor of the paper. “We ended up with maps that identify multiple sources of ammonia, and we were able to track the plumes from their sources and observe them coalescing into larger clouds.” 

Distinct plumes 

During the flights, the team collected data over the southeastern coast of the Salton Sea, which straddles Riverside and Imperial counties. There, Mako revealed small plumes coming from geothermal fumaroles venting superheated water and steam that react with nitrogen-bearing compounds in the soil, releasing ammonia. 

Farther to the southeast, the results showed several geothermal power plants emitting ammonia, primarily from their cooling towers, as part of their normal operations. 

Farther southeast still, the researchers spotted ammonia emissions, a byproduct of animal waste, from cattle farms in the Imperial Valley. During the March 28 flight, a plume from the largest facility in the study area measured up to 1.7 miles (2.8 kilometers) wide and extended up to 4.8 miles (7.7 kilometers) downwind of the source.

‘Very large puzzle’ 

As part of the study, AQMD’s Mecca monitoring station recorded seasonal changes in ammonia concentrations. Given the few sources in the area, the researchers surmised that winds during certain months tend to blow the gas from Imperial Valley to the Coachella Valley. 

The study underscores the benefits of detailed spatial information about ammonia emissions, and it partly informed the agency’s decision in July to expand its ammonia-monitoring network and extend the life of the Mecca station. 

As a precursor to PM2.5, ammonia is “one piece of a very large puzzle” that, for Coachella Valley residents, includes vehicle emissions, desert dust, and agricultural activities, said Payam Pakbin, manager of the Advanced Monitoring Technologies Unit at AQMD and a paper coauthor. 

“These communities want to know the contributions of these sources to the air quality they’re experiencing,” he added. “Findings like these help our agency better prioritize which sources require the most attention and ultimately guide our focus toward those that are the highest priority for achieving emission reductions in this community.” 

News Media Contacts

Andrew Wang / Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 626-840-4291
andrew.wang@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

2025-129

Magic is in the air. No wait… MAGEQ is in the air, featuring scientists from NASA centers across the country who teamed up with the National Oceanic and Atmospheric Administration (NOAA), the University of Maryland Baltimore County, and several other university and government partners and collaborators.

This summer, six planes collectively flew more than 400 hours over the mid-Atlantic United States with a goal of gathering data on a range of objectives, including air quality, forestry, and fire management.

This was part of an effort called MAGEQ, short for Mid-Atlantic Gas Emissions Quantification. Rather than one mission, MAGEQ consists of several individual missions across more than a dozen organizations and agencies, along with university students. Over the course of around six weeks, aircraft flew over cities, wetlands, farms, and coal mining areas.

“Each aircraft team is comprised of highly skilled and motivated people who understand how to fly their particular plane to achieve the science they want,” said Glenn Wolfe, research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and project lead for MAGEQ. “The complexity comes in identifying how each platform can complement or supplement the others.”

Coordinating flights required both advanced planning and flexibility to get the best outcome. Weather proved to be a primary challenge for the team, as members worked around cloudy days, wind, and storms to ensure safe flights.

The six aircraft had different objectives and requirements. For example, some carried instruments that needed to fly high to simulate a satellite’s view of the atmosphere and the Earth’s surface and could not measure through clouds. Others were equipped with instruments that directly measured the air particles and could work under the clouds, provided there was no rain.

Despite weather challenges, flight teams worked together to coordinate as many multi-aircraft flight days as possible, meeting the overall objective of the MAGEQ campaign.

“It’s been inspiring to see how everybody worked together,” said Lesley Ott, research meteorologist and lead carbon cycle modeler for NASA’s Global Modeling and Assimilation Office at NASA Goddard. “By collecting data together, not only can we do a better job as scientists in having more complete understanding, we can also do a better job making usable data sets that meets the needs of different stakeholders.”

State resource managers in North Carolina and Virginia, for example, could benefit from this data as they monitor the health of wetlands, which provide resilience to storms, absorb carbon from the atmosphere and support local tourist industries. The data could also help operators at energy-producing facilities detect methane leaks or equipment failures quickly. Faster detection could speed up intervention and minimize waste, as well as lessen environmental impacts. Stakeholders were an integral part of the planning process, Ott said. They made suggestions about measurement sites and data needs that informed the flight planning.

Scientists will also use the measurements to verify satellite data from both public and commercial data providers. Satellites like the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument collect similar data. Scientists can compare the airborne and satellite data to get a more complete picture of the atmosphere. They also will use MAGEQ data to evaluate atmospheric chemistry modeling from the Goddard Earth Observing System (GEOS) model, which connects atmospheric, oceanic, and land data to help create a more comprehensive picture of Earth science.

“Every aircraft does something different and contributes a different type of data,” said Steve Brown, leader of the tropospheric chemistry and atmospheric remote sensing programs at the NOAA Chemical Sciences Laboratory in Boulder, Colorado. “We’re going to have a lot of work to do at the end of this to put all these data sets together, but we will make the best use of all these measurements.”

By Erica McNamee

NASA’s Goddard Space Flight Center, Greenbelt, Md.