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Volume 15, issue 4
Atmos. Chem. Phys., 15, 1995–2008, 2015
https://doi.org/10.5194/acp-15-1995-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 15, 1995–2008, 2015
https://doi.org/10.5194/acp-15-1995-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Feb 2015

Research article | 24 Feb 2015

Sources of humic-like substances in the Pearl River Delta, China: positive matrix factorization analysis of PM2.5 major components and source markers

B. Y. Kuang1, P. Lin*,1, X. H. H. Huang2, and J. Z. Yu2,1 B. Y. Kuang et al.
  • 1Department of Chemistry, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
  • 2Institute of Environment, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
  • *now at: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, 99532, USA

Abstract. Humic-like substances (HULIS), the hydrophobic part of water-soluble organic carbon (WSOC), account for a significant fraction of PM2.5 mass. Their source studies are so far largely qualitative. In this study, HULIS and WSOC were determined in 100 PM2.5 samples collected in 2009 at an urban site (Guangzhou) and a suburban site (Nansha) in the Pearl River Delta in South China. The annual average concentration of HULIS was 4.83 and 4.71 μg m−3, constituting 8.5 and 10.2% of the PM2.5 mass, while HULIS-C (the carbon component of HULIS) contributed 48 and 57% of WSOC at the two sites, respectively. HULIS were found to correlate with biomass burning (BB) tracers (i.e., levoglucosan and K) and secondary species (e.g., SO42− and NH4+), suggesting its association with BB emissions and secondary formation processes. Sources of HULIS were investigated using positive matrix factorization analysis of PM2.5 chemical composition data, including major components and source markers. In addition to secondary formation process and BB emissions, residual oil combustion related to shipping was identified for the first time as a significant source of HULIS. Secondary formation process contributed the most, accounting for 49–82% of ambient HULIS at the two sites in different seasons. BB emissions contributed a seasonal average of 8–28%, with more contributions observed in the winter months (November–February) due to crop residue burning during harvest season. Residual oil combustion was revealed to be an important source at the suburban site in summer (44% of HULIS-C) due to its proximity to one of the ports and the shipping lane in the region. Vehicle emissions were found to contribute little to HULIS, but had contributions to the hydrophilic WSOC fraction. The contrast in contributions from different combustion sources to HULIS and hydrophilic WSOC suggests that primary sources of HULIS are linked to inefficient combustion. This source analysis suggests further study of HULIS be focused on secondary formation process and source characteristics of HULIS from BB and residual oil combustion.

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Humic-like substances (HULIS), the hydrophobic part of water soluble organic material, account for ~10% of PM2.5 mass in the Pearl River Delta, China. Source analysis using PM2.5 chemical composition data revealed that secondary formation process, biomass burning, and residual oil combustion from shipping as significant sources of HULIS. Vehicle emissions contributed little to HULIS. Primary sources of HULIS appeared to be linked to inefficient combustion.
Humic-like substances (HULIS), the hydrophobic part of water soluble organic material, account...
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