Secondary organic aerosol (SOA) contributes a significant fraction to aerosol mass and toxicity.Low-volatility organic vapors are critical intermediates connecting the oxidation of volatile organic compounds (VOCs) to SOA formation. However, the direct measurement of intermediate vapors poses a great challenge, further compounded by the difficulty of linking them to specific precursors from a cocktail of complex emission sources in the vast urbanized areas. Here, we present coordinated measurements of low-volatility oxidation products, termed oxygenated organic molecules (OOMs) in three most urbanized regions in China. With a newly-developed analysis methodology, we are able to assign these OOMs to their likely precursors and ultimately connect SOA formation to various VOCs. At all measurement locations, we find similar OOM
Intermediate volatility organic compound (IVOC) emissions from a large cargo vessel were characterized under realworld operating conditions using an on-board measurement system. Test ship fuel-based emission factors (EFs) of total IVOCs were determined for two fuel types and seven operating conditions. The average total IVOC EF was 1003 ± 581 mg•kg-fuel −1 , approximately 0.76 and 0.29 times the EFs of primary organic aerosol (POA) emissions from low-sulfur fuel (LSF, 0.38 wt % S) and high-sulfur fuel (HSF, 1.12 wt % S), respectively. The average total IVOC EF from LSF was 2.4 times that from HSF. The average IVOC EF under low engine load (15%) was 0.5−1.6 times higher than those under 36%−74% loads. An unresolved complex mixture (UCM) contributed 86.1 ± 1.9% of the total IVOC emissions. Ship secondary organic aerosol (SOA) production was estimated to be 546.5 ± 284.1 mg•kg-fuel −1 ; IVOCs contributed 98.9 ± 0.9% of the produced SOA on average. Fuel type was the dominant determinant of ship IVOC emissions, IVOC volatility distributions, and SOA production. The ship emitted more IVOC mass, produced higher proportions of volatile organic components, and produced more SOA mass when fueled with LSF than when fueled with HSF. When reducing ship POA emissions, more attention should be paid to commensurate control of ship SOA formation potential.
During the COVID-19 lockdown period (from January 23 to February 29, 2020), ambient
PM
2.5
concentrations in the Yangtze River Delta (YRD) region were observed
to be much lower, while the maximum daily 8 h average (MDA8) O
3
concentrations became much higher compared to those before the lockdown (from January 1
to 22, 2020). Here, we show that emission reduction is the major driving force for the
PM
2.5
change, contributing to a PM
2.5
decrease by 37% to 55% in
the four YRD major cities (i.e., Shanghai, Hangzhou, Nanjing, and Hefei), but the MDA8
O
3
increase is driven by both emission reduction (29%–52%) and
variation in meteorological conditions (17%– 49%). Among all pollutants,
reduction in emissions mainly of primary PM contributes to a PM
2.5
decrease
by 28% to 46%, and NOx emission reduction contributes 7% to 10%. Although NOx emission
reduction dominates the MDA8 O
3
increase (38%–59%), volatile organic
compounds (VOCs) emission reduction lead to a 5% to 9% MDA8 O
3
decrease.
Increased O
3
promotes secondary aerosol formation and partially offsets the
decrease of PM
2.5
caused by the primary PM emission reductions. The results
demonstrate that more coordinated air pollution control strategies are needed in
YRD.
China has >400 ports, is home to 7 of 10 biggest ports in the world and its waterway infrastructure construction has been accelerating over the past years. But the increasing number of ports and ships means increasing emissions, and in turn, increasing impact on local and regional air pollution. This paper presents an overview of the broad field of ship emissions in China and their atmospheric impacts, including topics of ship engine emissions and control, ship emission factors and their measurements, developing of ship emission inventories, shipping and port emissions of the main shipping areas in China, and quantitative contribution of shipping emissions to the local and regional air pollution. There have been an increasing number of studies published on all the above aspects, yet, this review identified some critical research gaps, filling of which is necessary for better control of ship emissions, and for lowering their impacts. In particular, there are very few studies on inland ports and river ships, and there are few national scale ship emission inventories available for China. While advanced method to estimate ship emission based on ship AIS activities makes it now possible to develop high spatial- and temporal-resolution emission inventories, the ship emission factors used in Chinese studies have been based mainly on foreign measurements. Further, the contribution of ship emissions to air pollution in coastal cities, the dispersion of pollution plumes emitted by ships, or the chemical evolution process along the transmission path, have so far not been systematically studied in China.
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