Ethanol and Methanolin South Korea and China: Evidencefor Large Anthropogenic Emissions Missing from Current Inventories

Observations during the KORUS-AQ, MAPS-Seoul, and APHH-Beijing field campaigns of 2015–2017 reveal high concentrations of ethanol and methanol in urban air over South Korea and China, with median concentrations of 2–4 ppb for ethanol and 12–18 ppb for methanol. Simulations with the GEOS-Chem model show that these values cannot be captured by current emission inventories. They could originate from volatile chemical products (VCPs). Fitting observed ethanol concentrations with GEOS-Chem would imply per capita VCP emissions 2.4 times higher in South Korea and 1.5 times higher in China than in the U.S. The strong ethanol–methanol correlation suggests a major methanol component in VCP emissions, unlike in the U.S. where methanol use is largely banned. Including these emissions in GEOS-Chem increases the level of surface ozone over South Korea and China by 1–3 ppb. KORUS-AQ aircraft profiles also indicate a high free tropospheric methanol background of 3.2 ppb, which appears to be of terrestrial biospheric origin but cannot be reproduced by GEOS-Chem.