Long-term evolution of carbonaceous aerosols in PM2.5 during over a decade of atmospheric pollution outbreaks and control in polluted central China

Zhangsen Dong; Xiao Li; Zhe Dong; Fangcheng Su; Shenbo Wang; Luqi Shang; Zihan Kong; Shanshan Wang

doi:10.1016/j.scitotenv.2024.173089

Long-term evolution of carbonaceous aerosols in PM_2.5 during over a decade of atmospheric pollution outbreaks and control in polluted central China

Sci Total Environ. 2024 May 9:173089. doi: 10.1016/j.scitotenv.2024.173089. Online ahead of print.

Authors

Zhangsen Dong¹, Xiao Li², Zhe Dong³, Fangcheng Su², Shenbo Wang², Luqi Shang¹, Zihan Kong², Shanshan Wang²

Affiliations

¹ College of Chemistry, Zhengzhou University, Zhengzhou 450001, China; Institute of Environmental Sciences, Zhengzhou University, Zhengzhou 450001, China.
² School of Ecology and Environment, Zhengzhou University, Zhengzhou 450001, China; Institute of Environmental Sciences, Zhengzhou University, Zhengzhou 450001, China.
³ College of Chemistry, Zhengzhou University, Zhengzhou 450001, China; Institute of Environmental Sciences, Zhengzhou University, Zhengzhou 450001, China. Electronic address: ZheDong92@outlook.com.

PMID: 38734089
DOI: 10.1016/j.scitotenv.2024.173089

Abstract

Against the backdrop of an uncertain evolution of carbonaceous aerosols in polluted areas over the long term amid air pollution control measures, this 11-year study (2011-2021) investigated fine particulate matter (PM_2.5) and carbonaceous components in polluted central China. Organic carbon (OC) and elemental carbon (EC) averaged 16.5 and 3.4 μg/m³, constituting 16 and 3 % of PM_2.5 mass. Carbonaceous aerosols dominated PM_2.5 (35 and 27 %) during periods of excellent and good air quality, while polluted days witnessed other components as dominants, with a significant decrease in primary organic aerosols and increased secondary pollution. From 2011 to 2021, OC and EC decreased by 53 and 76 %, displaying a high-value oscillation phase (2011-2015) and a low-value fluctuation phase (post-2016). A substantial reduction in high OC and EC concentrations in 2016 marked a milestone in significant air quality improvement attributed to effective control measures, especially targeting OC and EC, evident from their decreased proportion in PM_2.5. Primary OC (POC) in winter exhibited the most pronounced reduction (8 % per year), and the seasonal disparities in PM_2.5 and carbonaceous components were reduced, showcasing the effectiveness of control measures. Contrary to the more pronounced reduction of EC, which decreased in proportion to PM_2.5, secondary OC (SOC) in PM_2.5 exhibited an increasing trend. Along with rising OC/EC, SOC/OC, and SOC/EC ratios, this indicates a growing prominence of secondary pollution compared to the decrease in primary pollution. SOC shows an increasing trend with NO₂ rise (r = 0.53), without O₃ promoting SOC. Positive correlations of SOC with SO₂, CO (r = 0.41, 0.59), also highlight their influence on atmospheric conditions, oxidative capacity, and chemical reactions, indirectly impacting SOC formation. The implementation of precise precursor emission reduction measures holds the key to future efforts in mitigating SOC pollution and reducing PM_2.5 concentrations, thereby contributing to improved air quality.

Keywords: Air quality; Carbonaceous aerosols; Long-term variations; Pollution reduction; Secondary organic aerosols.