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In recent years, the "coal to electricity" project (CTEP) using clean energy instead of coal for heating has been implemented by Beijing government to cope with air pollution. However, VOC pollution after CTEP was rarely studied in suburbs of Beijing. To fill this exigency, 116 volatile organic compounds (VOCs) were observed during nonheating (P1) and heating (P2) periods in suburban Beijing. The results showed that the total of VOCs (TVOCs) was positively correlated with PM2.5, PM10, NO2, CO, and SO2 but negatively correlated with O3 and wind speed. The average TVOCs concentration was 19.43 ± 12.41 ppbv in P1 and 16.25 ± 8.01 ppbv in P2. Aromatics and oxygenated VOCs (OVOCs) were the main contributors to ozone formation potential (OFP). Seven sources of VOCs identified by the positive matrix factorization (PMF) model were industrial source, coal combustion, fuel evaporation, gasoline vehicle exhaust, diesel vehicle exhaust, background and biogenic sources, and solvent usage. The contribution of coal combustion to VOCs increased significantly during P2, whereas industrial sources, fuel evaporation, and solvent usage exhibited opposite trends. The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) were used to analyze the source distributions. The results showed that VOC pollution was caused mainly by air mass from southern Hebei during P1 but by local emissions during P2. Therefore, although the contribution of coal combustion after heating increased, TVOCs concentration during P2 was lower than that during P1. Chronic noncarcinogenic risks of all selected VOC species were below the safe level, while the carcinogenic risks of most selected VOC species were above the acceptable risk level, especially for tetrachloromethane and 1,2-dichloroethane. The cancer risks posed by gasoline vehicle emissions, industrial enterprises, and coal combustion should be paid more attention. [ABSTRACT FROM AUTHOR]

Atmospheric volatile organic compounds (VOCs) were observed by an on-line gas chromatography-flame ionization detector monitoring system from November 2016 to August 2017 in Beijing. The average concentrations were winter (40.27 ± 25.25 μg/m3) > autumn (34.25 ± 19.90 µg/m3) > summer (32.53 ± 17.39 µg/m3) > spring (24.72 ± 17.22 µg/m3). Although benzene (15.70%), propane (11.02%), ethane (9.32%) and n -butane (6.77%) were the most abundant species, ethylene (14.07%) and propene (11.20%) were the key reactive species to ozone formation potential (OFP), and benzene, toluene, ethylbenzene, m -xylene + p- xylene and o -xylene (54.13%) were the most reactive species to secondary organic aerosol formation potential (SOAFP). The diurnal and seasonal variations indicated that diesel vehicle emission during early morning, gasoline vehicle emission at the traffic rush hours and coal burning during the heating period might be important sources. Five major sources were further identified by positive matrix factorization (PMF). The vehicle exhaust (gasoline exhaust and diesel exhaust) was found to be contributed most to atmospheric VOCs, with 43.59%, 41.91%, 50.45% and 43.91%, respectively in spring, summer, autumn and winter; while solvent usage contributed least, with 11.10%, 7.13%, 14.00% and 19.87%, respectively. Biogenic emission sources (13.11%) were only identified in summer. However, both vehicle exhaust and solvent usage were identified to be the key sources considering contributions to the OFP and SOAFP. Besides, the contributions of combustion during heating period and gasoline evaporation source during warm seasons to OFP and SOAFP should not be overlooked. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Submerged combustion technology is a novel technology for natural gas pipeline heating. The core of the technology lies in the design of the heat exchanger. The design method of submerged combustion heat exchanger is introduced in this paper. The 200 kW submerged combustion heat exchanger is designed and put into use during the heating period of a gate station in Beijing. The measured data were used to calculate heat transfer coefficient of the convection inside and outside the tube, and the actual comprehensive heat transfer coefficient under rated design conditions was obtained through data fitting calculation, and then the comprehensive heat transfer coefficient of the design was modified. The calculation results showed that the modified comprehensive heat transfer coefficient of the design was 1. 56. Through actual heat transfer coefficient of convection outside tube calculated by maximum velocity of water bath outside the tube, fitting for the relation between the power and the maximum velocity of water bath, using of heating equipment in the 120 kW and stable operation of the measured data validation, water bath maximum velocity calculation error rate is 6.67%. This method can provide a reference for the same type of submerged combustion heat exchanger design. [ABSTRACT FROM AUTHOR]

The prohibition of open straw burning and clean energy transitions, implemented in the last 10 years, resulted in remarkable reductions in ambient biomass burning pollution in Beijing. Here, we present the reduction of biomass burning molecular tracer (i.e., levoglucosan) concentrations using year-long filter sample results collected in Beijing respectively during 2010–2011 and 2017–2018. The annual mean concentrations (95% CI) of levoglucosan during 2010–2011 and 2017–2018 were 0.34 (0.29–0.38) μg m−3 and 0.11 (0.09–0.13) μg m−3, respectively, with a 67% decrease. Compared to 2011, the two traditional open biomass burning episodes in early summer and during the fall post-harvest season disappeared in 2018. Meanwhile, the intensity and duration of biomass burning episodes during the heating season in 2017–2018 was much weaker and shorter than that in 2010–2011. Our results indicate that the implemented clean air action plans were effective in reducing open biomass burning, but the control of biofuel combustion activities during the heating season remains a major challenge in China. • Two traditional open biomass burning episodes in the harvest season disappeared. • The improvement in biomass burning pollution was dominated by emission abatements. • Clean air action plans were effective in reducing open straw burning emissions. • The control of biomass combustion activities in the heating season remains a major challenge. [ABSTRACT FROM AUTHOR]

Atmospheric fine particulate pollution has been a dramatically environmental concern in all seasons in the megacity Beijing in recent years. A long-term real-time monitoring campaign of non-refractory submicron aerosol (NR-PM 1) at a southeastern urban site in Beijing from July 13, 2017 to May 26, 2018 using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) was carried out to investigate the characteristics and evolution processes of NR-PM 1 and its potential source effects. The annual average concentration of NR-PM 1 during the entire study period was 40.8 μg/m3, lower than that of NR-PM 1 from July 2011 to June 2012, and its seasonal variation presented the order of autumn and spring > winter > summer. The average concentration of organic species Org in the entire study was 15.1 μg/m3 and accounted for 37% of NR-PM 1 , being consistently a significant component of NR-PM 1 in the four seasons. The average concentrations of SO 4 2− and NO 3 − were 8.6 and 11.1 μg/m3, respectively, accounting for 21% and 27% of NR-PM 1 , and NO 3 − and its contribution to NR-PM 1 exceeded those of SO 4 2−, suggesting that secondary nitrate became a more dramatic pollutant. Note that SO 4 2− in summer accounted for 27% of NR-PM 1 , higher than those in the other seasons, indicating that secondary sulfate formation was greatly important in summer, however, NO 3 − in summer accounted for 22% of NR-PM 1 , lower than those in the other seasons, more likely due to relatively high temperature in summer being favorable for dissociation of nitrate. NH 4 + and Cl− species presented lower mass concentrations and mass fractions, and the seasonal variation of NH 4 + was similar to NO 3 −, yet Cl− presented a typical seasonal change related to intense fossil fuel combustion during the heating period in winter and biomass burning in autumn with an order of winter > autumn > spring > summer. All aerosol species exhibited different diurnal cycles, of which Org presented a bimodal mode, SO 4 2− and Cl− showed a flatter diurnal pattern, however, NO 3 − and NH 4 + displayed more similar single-peak patterns. The conversion of SO 2 to SO 4 2− presented an obvious seasonal variation with summer > autumn > spring > winter driven by different factors. The conversion of NO 2 to NO 3 − also showed a significant seasonal change characterized by autumn > summer and spring > winter controlled by different factors. Relative humidity, temperature and wind speed during the study period were significant meteorological elements influencing NR-PM 1 and its species, and heavy haze pollution episodes largely occurred under high relative humidity and low wind speed. High potential source regions influencing NR-PM 1 pollution in Beijing in all seasons presented dramatically distributions related to wind directions. • The mean loadings of all NR-PM 1 species in the entire study followed the order of Org > NO 3 − > SO 4 2− > NH 4 + > Cl−. • All NR-PM 1 species obviously presented different seasonal variations. • RH and NH 3 could promote the conversions of SO 2 to SO 4 2− and NO 2 to NO 3 −in all seasons. • High potential source regions influencing Beijing NR-PM 1 showed distinct distributions related to wind directions. [ABSTRACT FROM AUTHOR]

• Pb-rich particles were mainly in the forms of PbO, PbCl 2 and Pb(NO 3) 2 in Beijing. • Pb-rich particles were mainly produced by coal combustion during heating period. • This is the first report of atmospheric processes producing toxic Pb(NO 3) 2 in China. • Increasing toxicity of Pb-rich particles may have negative environmental effects. A single particle aerosol mass spectrometry (SPAMS) was deployed to investigate the mixing state and chemical processing of Pb-rich particles in suburban Beijing. Based on a large dataset of mass spectra, Pb-rich particles were classified into Pb-O-Cl-N-S (55%), Pb-N (17%), Pb-N-S (15%), and Pb-EC (7%). Residual coal combustion, industrial activities, and meteorological conditions were identified as main factors regulating the variations of Pb-rich particles in the atmosphere. The highest abundance of the Pb-rich particles was observed during heating period (HP) primarily due to the increase in coal usage. Pb in Pb-O-Cl-N-S type was identified in forms of PbO, PbCl 2, and Pb(NO 3) 2. Dominantly presented in the form of Pb(NO 3) 2 , Pb-N type represented the completely transformed Pb-rich particles from PbO/PbCl 2 by atmospheric processes. It is found that PbCl 2 and PbO could be transformed to Pb(NO 3) 2 , highly dependent on the amount of NO 2 and RH. Significant enhancement of nitrate in Pb-O-Cl-N-S particles was observed when the RH was greater than 60%, emphasizing the importance of heterogeneous hydrolysis of N 2 O 5 on the formation of Pb(NO 3) 2. Compared with non-carcinogenic PbCl 2 /PbO and insoluble PbO, soluble and carcinogenic Pb(NO 3) 2 produced by atmospheric processes may significantly enhance negative effects of Pb-rich particles on human health and the ecosystem. [ABSTRACT FROM AUTHOR]