Ethanol and Methanol in South Korea and China: Evidence for 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.