Abstract
“Clean Heating” (CH) was promoted in 2017 in north China. Nevertheless, CH impacts on PM2.5 chemical components, sources, and health risks in small cities remain unclear. A field measurement was taken at an urban site within the central Beijing-Tianjin-Hebei (BTH) region covering the pre-heating season (PHS) and heating season (HS) in the winter of 2019. PM2.5 concentrations (in µg m–3) increased from 69.1 in the PHS to 129 in the HS, reflecting the impacts of heating activities. Water-soluble ions dominated in terms of PM2.5, accounting for 32.0% in the PHS and 42.3% in the HS, respectively. On average, SO42– and NO3– (in µg m–3) were found to be markedly enhanced from 3.54 and 11.1 in the PHS to 13.1 and 23.2 in the HS, especially in the case of SO42–, reflecting the increased usage of coal/natural gas. Meanwhile, the ratios of NO3–/SO42– dropped from 2.75 in the PHS to 2.08 in the HS, implying drastic SO42– emissions from coal combustion used for heating. This may have been associated with the re-burning of coal for heating despite the “coal banning” law. Total carcinogenic risks (CRs) posed by inhalation of heavy metals increased from 6.61 × 10–6 in children and 2.64 × 10–5 in adults in the PHS to 8.23 × 10–6 and 3.29 × 10–5 in the HS. In contrast, the non-CRs for children and adults decreased in the HS due to a reduction in Ba of 85.5% in the HS. A total of seven sources, including fugitive dust (FD), vehicle exhaust (VE), coal combustion (CC), secondary inorganic aerosol (SIA), industrial emissions (IE), glass production (GP), and biomass burning (BB), were identified using a PMF model. The GP fraction decreased from 29.6% in the PHS to 2.59% in the HS due to strict emission control, which concurred with the decrease in Ba. The CC contribution increased significantly from 2.42% to 16.9%, indicating the CC was still serious in HS. Furthermore, the elevated BB share in the HS suggested that biomass was still being used as heating fuel.
Highlights
The Beijing-Tianjin-Hebei (BTH) region, the center of the North China Plain, has suffered from severe pollution due to fine particulate matter (PM2.5, an aerodynamic diameter less than or equal to 2.5 μm), especially in the heating season (Cheng et al, 2019; Zhai et al, 2019; Li et al, 2020a, b, 2021a, b)
As high as 91.1% of sampling days showed a daily PM2.5 value of more than 75 μg m–3 assigned as Chinese National Ambient Air Quality Standard Grade II
A previous study reported that PM2.5 decreased by 71.2% in 2017 as compared with 2016 in Baoding City due to the “Coal to Gas” (CTG) policy in 2017 (Si et al, 2021)
Summary
The Beijing-Tianjin-Hebei (BTH) region, the center of the North China Plain, has suffered from severe pollution due to fine particulate matter (PM2.5, an aerodynamic diameter less than or equal to 2.5 μm), especially in the heating season (Cheng et al, 2019; Zhai et al, 2019; Li et al, 2020a, b, 2021a, b). Aerosol and Air Quality Research | https://aaqr.org (Li et al, 2020a, b; Wang et al, 2021) To mitigate this crisis in the BTH, the Chinese government issued an “Atmospheric Pollution Prevention Plan” (Clean Air Action) in 2013, which was aimed toward markedly reducing PM2.5 by 25% by 2017 (Chen et al, 2019). Airborne pollutant transport between neighboring cities resulted in high PM2.5 levels in Beijing, and regional integration has proven to be one of main solutions to mitigate this crisis (Chen et al, 2019). A “2 + 26” strategy covering Beijing, Tianjin, and 26 other cities acting as an “air pollution transmission channel” in four neighboring northern provinces (Hebei, Henan, Shandong, and Shanxi) was promoted by the Ministry of Ecology and Environment to further improve the air quality in Beijing and the BTH region during heating season (Chen et al, 2019)
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