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For six weeks in the summer of 2016 scientists from the United States and the Republic of Korea intensively studied air pollution over the Korean peninsula. Their mission: to diagnose the complex causes of the country's poor air quality and in so doing lay the groundwork for next-generation pollution monitoring from space that both nations plan to launch in the next few years.
Initial scientific results from the joint NASA-Korean field campaign released this week identified several strategies to reduce ozone and particulate matter levels in the Seoul metropolitan area and rural sections of the country. Seoul is one of the world's five most-populated urban areas.
Scientists from NASA and South Korea's National Institute of Environmental Research (NIER) presented findings from the Korea-United States Air Quality study (KORUS-AQ) to representatives of the Ministry of Environment at a scientific briefing in Seoul. The analysis will inform South Korean policymakers developing air quality strategies and identifying specific emission sources.
The 2016 KORUS-AQ field experiment targeted May and June, a time of year when local sources of pollution typically dominate South Korea's air quality. During these months pollution from East Asia and China travels less frequently over the Korean peninsula due to weather conditions. The scientists collected data from space, sea, land, and air. Airborne sampling was accomplished using two instrumented aircraft from NASA and one from Hanseo University, Seosan.
Reducing ozone pollution and harmful fine particles in the air could be achieved by cutting emissions of nitrogen oxides and volatile organic compounds, the study found. Ozone at ground level is formed by chemical reactions between these gases in the presence of sunlight.
These same gases also played a dominant role in the chemical formation of fine particulate matter, accounting for roughly half of the observed concentration. Overall, more than three-quarters of the particulate matter measured during the study was formed by secondary chemical reactions rather than being directly emitted from smokestacks or tailpipes.
"It's an encouraging result to see there is a clear overlap in the sources that need to be targeted to improve both fine particle and ozone pollution," said James Crawford, lead U.S. KORUS-AQ scientist from NASA's Langley Research Center in Hampton, Virginia.
Emissions from cars and trucks are one of the major sources of nitrogen oxides, according to the study, and industrial solvents, particularly toluene, were identified as the dominant volatile organic compounds contributing to the formation of ozone and particulate matter.
Key sets of detailed measurements collected during KORUS-AQ of air chemistry and pollution over Seoul, from the surface to a height of 28,000 feet, are also being analyzed by NASA and Korean scientists working on new space missions that will for the first time measure air pollution hourly from geostationary orbit more than 22,000 miles away.
These Earth-observing satellites will use reflected sunlight to detect certain pollutants throughout the atmosphere reaching miles above the surface. Determining how much of a target pollutant is at ground level where people live and breathe is a continuing challenge. Analysis of the KORUS-AQ data sets will help scientists learn how to better tease out these details from space.
NASA and South Korea are both preparing air quality satellite missions for launch to geostationary orbits within the next five years. First will be the NIER Geostationary Environment Monitoring Spectrometer (GEMS), followed by NASA's Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument. TEMPO will make accurate hourly daytime measurements of tropospheric pollutants - ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, and aerosols - over the United States, Canada and Mexico. GEMS will provide similar data over East Asia.
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