Quantify changes in ambient PM2.5 and three heavy metal components before and after relocation of a steel plant using interrupted time series analysis
- VernacularTitle:应用中断时间序列分析法评估炼钢厂迁出前后周边大气PM2.5及其部分重金属浓度变化
- Author:
Shaofeng SUI
1
;
Xianbiao SHEN
2
;
Yangyang REN
1
;
Zhen YUAN
2
;
Fengchan HAN
1
;
Cheng YANG
2
Author Information
- Publication Type:Investigation
- Keywords: particulate matter; heavy metal; urban environmental transformation; interrupted time series; air pollution
- From: Journal of Environmental and Occupational Medicine 2025;42(12):1491-1496
- CountryChina
- Language:Chinese
-
Abstract:
Background Industrial emissions are a well-established major source of urban fine particulate matter (PM2.5) and associated heavy metals. To improve local air quality, Shanghai No. 1 Iron and Steel Plant in Baoshan District was entirely relocated, with all production lines successively shut down in 2018. Objective To evaluate the trends in PM2.5 and three heavy metal concentrations - chromium (Cr), mercury (Hg), and thallium (Tl) —in the local atmosphere pre- and post- relocation of the steel plant. Methods Taking the steel plant relocation in 2019 as the intervention cutoff point, this study was divided into two phases: pre-intervention (January 2017 to December 2018) and post-intervention (January 2019 to December 2021). Monthly mean pollutant concentrations were used to construct an interrupted time series (ITS) model, followed by segmented linear regression to assess the pre- and post-intervention trends in ambient PM2.5 and three heavy metals surrounding thesteel plant. Results The ITS regression analysis revealed that the change in PM2.5 concentration (b2) after the intervention was −7.16 μg·m−3, while the changes in Cr, Hg, and Tl concentrations (b2) were −0.46, −0.03, and −0.06 ng·m−3, respectively. Prior to the intervention, PM2.5 mass concentrations exhibited a temporal decline with a slope of b1 = –0.69 (P<0.05); seasonal adjustment further strengthened the overall significance of the model. Before the intervention, the concentration of Cr increased over time, with a slope of b1=0.12 (P<0.05). After the intervention, the concentration of Cr showed a gradual downward trend over time, with a slope (b1 + b3) of −0.04, and significant seasonal variations were observed. The concentration of Hg decreased over time before the intervention, with a slope of b1=−
0.0029 (P<0.05). After the intervention, the slope was −0.0003 , showing a further slow decline in Hg concentration over time. However, no significant seasonal trend was observed for Hg. The mass concentration of Tl decreased after the intervention, and the difference before and after the intervention was statistically significant (P<0.05). PM2.5, Cr, and Tl better fit to the seasonal model, whereas Hg showed a better fit to the non-seasonal model. Conclusion The steel plant relocation intervention has markedly improved local air quality.
