Chemical components of PM2.5 in different seasons in Harbin, China--颗粒学报PARTICUOLOGY

Yu, Q., Liu, J., Zhong, Y., Cao, X., Wang, Y., & Cheng, Y. (2023). Chemical components of PM2.5 in different seasons in Harbin, China. Particuology, 76, 113-121. https://doi.org/10.1016/j.partic.2022.08.002

Chemical components of PM_2.5 in different seasons in Harbin, China

Qinqin Yu, Jiumeng Liu, Yingjie Zhong, Xubing Cao, Yulong Wang, Yuan Cheng ^*

State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China

10.1016/j.partic.2022.08.002

Volume 76, May 2023, Pages 113-121

Received 18 April 2022, Revised 30 July 2022, Accepted 1 August 2022, Available online 18 August 2022, Version of Record 22 September 2022.

E-mail: ycheng@hit.edu.cn

Highlights

• The NO₃⁻/SO₄²⁻ ratios were lower in winter.

• Secondary formation associated with RH made dominant contribution to organic matter in winter.

• Biomass burning related to open agricultural fires was essential for organic matter in fall and spring.

Abstract

The seasonal characteristics of fine particulate matter (PM_2.5) were investigated from October 2020 to April 2021 (spreading fall, winter and spring) in Harbin, a city located in northeast China. The mass concentrations of PM_2.5 in winter were significantly higher than those in fall and spring. Moreover, our results indicated that various aerosol species had obvious seasonality. The proportions of secondary components were higher in winter than other two seasons. In contrast, the ratios of nitrate to sulfate (NO₃⁻/SO₄²⁻) showed lower levels in winter, which was because both the ratios of nitrogen dioxide to sulfur dioxide (NO₂/SO₂) and the ratios of nitrogen oxidation ratio to sulfur oxidation ratio (NOR/SOR) exhibited lower values in winter than in fall and spring. With PM_2.5 increased, the NO₃⁻/SO₄²⁻ ratios showed increasing trends in all three seasons, which was mainly attributed to the increase of NOR/SOR ratios in fall and spring, and the increase of both NO₂/SO₂ and NOR/SOR ratios in winter. This result highlighted that nitrate was more important than sulfate as a driver for the growth of PM_2.5 during the period of heavy air pollution. Additionally, the sources of organic aerosol (OA) in different seasons were also distinctly different. Overall, the sum of biomass burning OA (BBOA) and secondary OA (SOA) contributed >70% of OA in three seasons. The fractional contributions of BBOA to total OA, notably, exhibited higher levels in fall and spring, because of intensive open agricultural fires. The SOA fractions in OA were larger in winter, likely due to higher relative humidity which facilitated the secondary formation. A large increase in the proportions of BBOA was observed during polluted days in fall and spring compared to clean days. In comparison, during heavily-polluted periods, secondary formation made a dominant contribution to organic matter in winter.

Graphical abstract

Keywords

PM_2.5; Seasonal characteristics; Sulfate; Nitrate; Biomass burning; Secondary formation

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