Key Takeaways & Executive Findings
- •• • K+ and Mg2+ concentrations increased by 15.89 and 20.08 times, respectively, on Lunar New Year's Eve, serving as core water-soluble ion tracers for fireworks emissions, enabling precise source apportionment in urban air quality management. • • Inorganic elements Ba and Sr exhibited growth multiples of 127.72 and 121.26 on Lunar New Year's Eve, respectively, matching metal colorant compositions in fireworks, providing unambiguous chemical fingerprints for pollution tracing. • • Fireworks contributed 20.3% to PM2.5 on Lunar New Year's Eve, with PM2.5 concentrations reaching 4.4 times non-setting-off levels, highlighting the need for targeted emission control measures during peak periods. • • During the fifth day period, secondary conversion ions (SO4^2-, NO3^-) showed increased contribution, with NH4+ strongly correlated with SO4^2- and NO3^- (R^2 ≥ 0.85), confirming ammonium salt formation and secondary organic aerosol (OC/EC > 15) mechanisms, essential for understanding atmospheric chemical evolution.
Abstract
To address the significant increase in fine particulate matter (PM2.5) and its chemical component concentrations caused by the concentrated setting-off of fireworks and firecrackers during the Spring Festival in Yancheng City, this study introduced the Bayesian-optimized XGBoost model (BO-XGBoost) based on PM2.5, particulate component, and meteorological observation data. The model simulated non-setting-off baseline concentrations using meteorological factors as independent variables, enabling quantitative assessment of setting-off contributions. Results showed that the concentrated setting-off exerted significantly differentiated effects on various pollutants. Among water-soluble ions, K+ and Mg2+ were core characteristic tracers, with concentrations reaching 15.89 and 20.08 times baseline levels on Lunar New Year's Eve, directly reflecting high-intensity emissions. Secondary conversion ions such as SO4^2- and NO3^- showed sustained high contributions on both Lunar New Year's Eve and the fifth day of the first lunar month, reflecting cumulative effects of atmospheric chemical transformation. Among inorganic elements, K, Ba, and Sr were core characteristic tracers, with concentrations showing explosive growth on Lunar New Year's Eve, serving as direct fingerprints of fireworks. Elements such as Pb and Mn were also significantly affected, reflecting direct heavy metal emissions. Temporal comparisons indicated that emission intensity on Lunar New Year's Eve was significantly higher than on the fifth day, with increased proportional contribution of secondary conversion processes on the fifth day. The study achieved accurate quantification of setting-off contributions through a data-driven model, clarifying pollution fingerprint characteristics and temporal differentiation patterns, providing scientific basis for air quality management and policy optimization during the Spring Festival.
1. Introduction
Concentrated fireworks and firecrackers setting-off during the Spring Festival induces acute PM2.5 pollution episodes, yet conventional source apportionment methods often fail to isolate the contribution from meteorological confounding. Existing approaches, such as chemical mass balance or positive matrix factorization, require extensive precursor profiles and are limited in capturing nonlinear interactions between emissions and atmospheric processes. This study addresses the bottleneck by employing a Bayesian-optimized XGBoost model, which leverages meteorological variables to simulate non-setting-off baseline concentrations, thereby enabling robust quantification of setting-off contributions without relying on exhaustive emission inventories.
The experimental protocol integrates PM2.5 chemical composition data and meteorological observations, allowing for the identification of characteristic tracers (e.g., K+, Mg2+, Ba, Sr) and the assessment of secondary transformation effects. By comparing Lunar New Year's Eve and the fifth day, the model reveals temporal differentiation in emission intensity and secondary formation, providing actionable insights for policy optimization. This data-driven approach overcomes the limitations of traditional methods, offering a scalable framework for evaluating episodic emission impacts in urban environments.
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YI Zhaojun, WANG Shuai, WANG Yuehua, ZHAO Youzheng, XIAN Yue, WEI Ting, ZHU Wenda (2026). Evaluation on Impact of Spring Festival Fireworks and Firecrackers Setting-off on Yancheng City Based on a Bayesian-Optimized XGBoost Model. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202608021
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Frequently Asked Questions
How does the BO-XGBoost model handle meteorological confounding when estimating fireworks contribution to PM2.5?
The model uses meteorological factors as independent variables to simulate the non-setting-off baseline PM2.5 concentration. By comparing actual concentrations to this baseline, the contribution from fireworks is isolated. This approach effectively controls for meteorological variability, as demonstrated by the model's ability to capture the 20.3% contribution on Lunar New Year's Eve.
What are the key chemical tracers for fireworks emissions and their quantitative significance?
K+ and Mg2+ are core water-soluble ion tracers, with concentration increases of 15.89 and 20.08 times, respectively, on Lunar New Year's Eve. Inorganic elements K, Ba, and Sr are also critical, with Ba and Sr showing growth multiples of 127.72 and 121.26, respectively. These tracers provide unambiguous fingerprints for source identification.
How does the model differentiate between primary emissions and secondary formation during different periods?
The model compares contributions on Lunar New Year's Eve (high primary emissions) and the fifth day (lower emissions but higher secondary transformation). On the fifth day, the contribution of secondary ions like SO4^2- and NO3^- increases, indicating atmospheric chemical processing. This is supported by strong correlations (R^2 ≥ 0.85) between NH4+ and these ions, confirming ammonium salt formation.
What are the implications of the OC/EC ratio > 15 observed during fireworks periods?
An OC/EC ratio exceeding 15 indicates significant secondary organic aerosol (SOA) formation from volatile organic compounds released during fireworks. This suggests that photochemical reactions play a crucial role in enhancing PM2.5 toxicity and mass, which should be considered in air quality management strategies.
How scalable is the BO-XGBoost approach for other cities or events?
The methodology is data-driven and requires only PM2.5 composition and meteorological data, which are commonly available from monitoring networks. The model's flexibility allows adaptation to different geographical and meteorological conditions, making it a scalable tool for assessing episodic emission impacts in various urban settings.
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