Uptake of Water-Soluble Gas-Phase Oxidation Products Drives Organic Particulate Pollution in Beijing
Abstract
Despite recent decreases in heavy haze pollution events in Chinese urban areas, the national and world health organization air quality standards are still exceeded. Observations from monitoring networks show a stronger decrease of aerosols directly emitted to the atmosphere relative to secondary organic aerosol (SOA) generated from oxidation processes. Here, a comprehensive set of online, state of the art analytical measurement techniques were used during wintertime 2016 near Beijing in order to measure the chemical composition and sources of particulate and gas-phase components.
During haze episodes SOA dominated the organic mass (55-80%) indicating active oxidation processes during winter conditions. Fast particle phase-state transition from semi-solid to liquid was triggered by the increase of aerosol liquid water content, and increased significantly the particle mass in pollution episodes. This transition resulted in the effective uptake of water-soluble gas phase compounds, and was sufficient to explain the increase in SOA mass. Photo-chemical characterization of the air mass showed that small gas-phase aldehydes and acids namely, formaldehyde, acetaldehyde, glycolaldehyde, formic and acetic acid, partitioned efficiently to the particle-phase and explained a significant fraction (15 to 25%) of the rapid increase in organic mass in the particle-phase. The enhanced presence of aldehydes and acids during haze events can affect human health due to their carcinogenic nature. Future mitigation strategies to reduce non-methane volatile organic compound emissions, in particular, emissions related to industry and transportation, in order to effectively reduce organic particulate pollution in Beijing should be considered.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA166...04G
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3355 Regional modeling;
- ATMOSPHERIC PROCESSES