Seasonal variations of anhydrosugars in PM_2.5 in the Pearl River Delta Region, China

Abstract

Anhydrosugars including levoglucosan and mannosan are the most effective organic tracers for biomass burning aerosol in the atmosphere. In this study, to investigate the contribution of biomass burning emissions to the aerosol burden in the Pearl River Delta (PRD) region, China, 24-hour integrated PM_2.5 samples were collected simultaneously at four locations, (i) Guangzhou (GZ), (ii) Zhaoqing (ZQ) in Guangdong province, (iii) Hok Tsui (HT) and (iv) Hong Kong Polytechnic University (PU) in Hong Kong, in four seasons between 2006 and 2007. Levoglucosan and mannosan, together with water-soluble inorganic ions and water-soluble organic carbon (WSOC), were determined to elucidate the seasonal and spatial variations in biomass burning contributions. The concentrations of levoglucosan and mannosan were on average 82.4±123 and 5.8±8.6 ng m⁻³, respectively. The WSOC concentrations ranged from 0.2 to 9.4 µg m⁻³, with an average of 2.1±1.6 µg m⁻³. The relative contributions of biomass burning emissions to OC were 33% in QZ, 12% in GZ, 4% at PU and 5% at HT, respectively, estimated by the measured levoglucosan to organic carbon ratio (LG/OC) relative to literature-derived LG/OC values. The contributions from biomass burning emissions were in general 1.7–2.8 times higher in winter than those in other seasons. Further, it was inferred from diagnostic tracer ratios that a significant fraction of biomass burning emissions was derived from burning of hard wood and likely also from field burning of agricultural residues, such as rice straw, in the PRD region. Our results highlight the contributions from biomass/biofuel burning activities on the regional aerosol budget in South China.

• fine aerosol
• biomass burning
• WSOC
• levoglucosan
• Pearl River Delta

5. Acknowledgements

This study is partly supported by the Chinese Academy of Sciences (KZCX2-YW-BR-10), the Research Grants Council of Hong Kong (PolyU5197/05E), National Natural Science Foundation of China (41105083), Guangdong Natural Science Foundation (S2011040005259 and S2012010009824) and supported by the open fund of State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS (SKLLQG0808 and SKLLQG0902).