Scattered coal is the largest source of ambient volatile organic compounds during the heating season in Beijing

Abstract

Abstract. We identified scattered coal burning as the largest contributor to ambient volatile organic compounds (VOCs), exceeding traffic-related emissions, during the heating season (the cold season when fossil fuel is burned for residential heating) in Beijing prior to the rigorous emission limitations enacted in 2017. However, scattered coal is underestimated in emission inventories generally because the activity data are incompletely recorded in official energy statistics. Results of positive matrix factorization (PMF) models confirmed that coal burning was the largest contributor to VOC mixing ratios prior to the emission limitations of 2017, and a reduction in scattered coal combustion, especially in the rural residential sector, was the primary factor in the observed decrease in ambient VOCs and secondary organic aerosol (SOA) formation potential in urban Beijing after 2017. Scattered coal burning was included in a corrected emission inventory, and we obtained comparable results between this corrected inventory and PMF analysis particularly for the non-control period. However, a refined source subclassification showed that passenger car exhaust, petrochemical manufacturing, gas stations, traffic evaporation, traffic equipment manufacturing, painting, and electronics manufacturing are also contributors to ambient VOCs. These sources should focus on future emission reduction strategies and targets in Beijing. Moreover, in other regions with scattered coal-based heating, scattered coal burning is still the key factor to improve the air quality in winter.

Important Role of NO3 Radical to Nitrate Formation Aloft in Urban Beijing: Insights from Triple Oxygen Isotopes Measured at the Tower

“…Although some studies showed that N 2 O 5 heterogeneous processes on a high Cl – aerosol surface might be important pathways to nitrate formation, ,, this reaction would also result in a higher ClNO 2 yield and thus decrease the nitrate aerosol formation . Thus, the high nitrate concentration in the winter was mainly due to the active NO 3 + HC reaction on the basis of higher concentrations of volatile organic compounds (VOCs) via additional fossil fuel emissions. , Our results highlighted that the nocturnal chemistry (NO 3 radical chemistry, NO 3 + HC and N 2 O 5 + H 2 O/Cl – ) dominated nitrate production during the winter, while the OH/H 2 O + NO 2 pathway and nighttime pathways contributed equally to nitrate formation during the summer. Recent studies have pointed out that NO 3 + HC and N 2 O 5 hydrolyses were major formation mechanisms of nitrate production and were much greater in cold seasons on the basis of oxygen isotope observations.…”

“…17 Thus, the high nitrate concentration in the winter was mainly due to the active NO 3 + HC reaction on the basis of higher concentrations of volatile organic compounds (VOCs) via additional fossil fuel emissions. 38,66 Our results highlighted that the nocturnal chemistry (NO 3 radical chemistry, NO Interestingly, different vertical patterns of the reactions and nocturnal pathways were found during the distinct sampling periods. In the wintertime, the OH/H 2 O + NO 2 fractions at 8 m (41%) and 120 m (36%) were significantly higher than that at 260 m (20%), which might be attributed to higher NO 2 emissions at the ground surface.…”

Assessment of strict autumn-winter emission controls on air quality in the Beijing-Tianjin-Hebei region

“…Emission inventory estimates of NMVOCs are subject to large uncertainties, mainly due to poorly quantified industrial emissions (Li et al, 2017) and lack of reliable data for scattered areal sources such as residential coal burning (Li et al, 2019c;Peng et al, 2019;Shi et al, 2020). We find though that modelled CO is relatively unaffected by NMVOCs emissions.…”

Spatial and temporal variations of CO<sub>2</sub> mole fractions observed at Beijing, Xianghe and Xinglong in North China

“…The decrease of CO 2 in March 2019 is highly related to the temperature increase. As the heating is officially stopped in the middle of March, the anthropogenic emissions are much reduced (Shi et al, 2020). In April and May, the LAI increases monthly means of CO2 together with the 1σ standard deviation at BJ L1, XH L1 and XL between June 2018 and February 2020.…”