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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - EastAsiaAerosol (Sources and atmospheric processing of carbonaceous aerosol in East Asia)

Teaser

Summary

The overarching aim of this project is to assess the sources and atmospheric processing of East Asian aerosols between regions and different carbon fractions as well as seasonal variation. East Asia suffers from air pollution during winter with associated public health impacts. However, achieving mitigating goals remains a challenge in part due to large uncertainties concerning the contributions from different emission sources and complex atmospheric processes. Carbonaceous aerosols, including elemental carbon (EC) and organic carbon (OC), water-soluble and water insoluble organic carbon (WSOC & WIOC) are important components of the atmospheric particulate matter, affecting air quality and climate. However, the sources of carbonaceous aerosol in different components, as well as its composition and optical properties of organic carbon in this area, are still only poorly investigated and there are key gaps in current understanding. In this project, we firstly conducted dual-carbon isotope constrained source apportionment of EC, OC, WSOC, as well as WIOC in a large scale region, including Northern China Plain (Beijing & Tianjin, BTH), Yangtze River Delta (YRD; China), Korea Climate Observatory at Gosan (KCOG; South Korea) during January 2014. Second, we have conducted light-absorption of carbonaceous aerosol includes WSOC and BC for the January 2014 campaigns. Third, with an aim to uncover the seasonal trends of emission sources of carbonaceous aerosol in E. Asia, we performed a seasonal observation of BC and its sources at four key hotspot emission regions in China: BTH, YRD, PRD, and Sichuan basin.

The important for society: Fossil combustion Emission was identified as a key target to combat aerosol pollution. Our examinations demonstrate that the contribution of coal combustion in BTH region were larger than liquid fossil and biomass burning combined in Winter, highlighting that cutting coal burning and improving its burning efficiency should be the top priority for efforts to fight EC and also OC emissions. Reducing aerosol emissions by reduction and replacement of high-emitting end-use coal-fired combustion processes with cleaner energy across various sectors or by using cleaner residential stoves for space heating and cooking instead of ones with uncontrolled and inefficient combustion of coal will limit global warming, benefiting both the climate and air quality. In parallel, controlling emissions from liquid-fossil-fueled vehicles should be another priority in Beijing and Shanghai megacities. Eliminating emissions from biomass burning (e.g., heating, open fires of crop residue) could be an efficient strategy in all regions.

Work performed

Period works:
We firstly did Î´13C/âˆ†14C-diagnosed sources of BC, OC, WSOC, and WIOC in January 2014 campaign. Second, we have conducted light-absorption of carbonaceous aerosol includes WSOC and BC in January 2014 campaign, including BTH, YRD, KCOG, PRD, and SC, with aim to explore how the fossil sources influence light-absorbing aerosols. Third, with an aim to uncover the seasonal trends of emission sources of carbonaceous aerosol in E. Asia, we performed a four-season observation of BC and its sources at four key hotspot emission regions in China: BTH, YRD, PRD, and SC basin.

From the first study, we found that fossil sources (>50%) dominated the BC at all sites with most stemming from coal combustion, except for Shanghai, where liquid fossil sources were the largest. This study highlights high fossil contributions for all carbonaceous aerosol sub-compartments in East Asia, and suggests different transformations for different classes of carbonaceous aerosols.

The second study, the light-absorbing values were higher than the previous observations. The average fraction of total direct absorbance by WSOC relative to EC accounts for âˆ¼11 Â± 5% over E. Asia. Our result suggest the large fossil combustion may contribute to the regional climate change and earth surface energy budget.

Our third study of seasonal BC sources at four key economic zones of China, highest BC concentrations appeared during winter at BTH, YRD, and PRD, while observed loadings were also very high in the other seasons, e.g., spring at SC, fall at PRD, and summer at YRD. The fraction coal combustion of BTH-BC is much higher than YRD-BC, PRD-BC, and SC-BC. Conversely, liquid fossil combustion dominates in YRD, PDR, and SC, and less at BTH. For the seasonal BC aerosol, the seasonal variations in carbon isotope signature at BTH, PRD, and SC indicate seasonally shifting emissions between different sources. Whereas the clusters of isotope signature at YRD shows that BC sources stem from similar energy shares between seasons.

Publications/Manuscripts:

1. Fang, W. Z.; Andersson, A.; Zheng, M.; Lee, M.; Holmstrand, H.; Kim, S-W.; Du, K.; Gustafsson, Ã–. Divergent Evolution of Carbonaceous Aerosols during Dispersal of East Asian Haze. (Scientific Reports, 2017, 7: 10422, DOI:10.1038/s41598-017-10766-4)
2. Yu, K. Y.; Du, K.; incl. Fang, W. Z.; Gustafson, Ã–. et al. Characterizing and Sourcing Ambient PM2.5 over Key Emission Regions in China III: Carbon Isotope Apportionment and EC tracer method. (accepted by Atmos. Environ)
3. Fang, W. Z.; Andersson, A.; Zheng, M.; Lee, M.; Kim, S-W.; Du, K.; Gustafsson, Ã–. Sunlight-absorption Properties of Black and Brown Carbon Aerosols during January 2014 East Asian Haze. (Manuscript prepared to submit to Atmospheric Chemistry & Physics, 2018)
4. Fang, W. Z.; Du, K.; Andersson, A.; Cho, C-Y.; Kim, S-W.; & Gustafsson, Ã–. Seasonal-regional sources of black carbon aerosol in East, South, West, and North China. (under review with Journal of Geophysical Research-Atmospheres, 2018)

conference poster:
Fang, W. Z.; Andersson, A.; Zheng, M.; Lee, M.; Kim, S-W.; Du, K.; Gustafsson, Ã–. Radiocarbon-based source apportionment of organic, elemental, water-soluble organic carbon aerosols and light absorption of water-soluble organic carbon aerosols in the East Asia, 2016 AGU Fall Meeting, San Francisco, California

Final results

Our results provides a credible scientific underpinning for efficient mitigation actions toward efficiently reducing anthropogenic aerosol emissions for both the public and policymakers. This research would be instrumental in making the link to targeting efficient mitigation for the emission of aerosols, still much needed for improving human health and reducing anthropogenic climate forcing over E. Asia. BC is the most important light-absorbing component of aerosols, exerting a positive radiative forcing rivalling that of CO2 on the global climate, but with significantly larger uncertainty. Knowledge about the sources of carbonaceous aerosol components from this study facilitate an improved estimate of aerosol-induced climate and health impacts, and a regionally-seasonally-tailored mitigation strategy for different areas during different seasons in East Asia.