In order to probe the seasonal variation, formation mechanisms as well as geographical origins of fine particles and its chemical components in two cities (Zhengzhou, ZZ and Xinxiang, XX) in Central ...Plains Urban Agglomeration, daily PM2.5 aerosol samples were collected for four consecutive seasons during 2017–2018. The annual average concentrations of PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm) were calculated at 70.5 ± 50.8 and 69.0 ± 46.3 μg m−3 at ZZ and XX, respectively. Daily ambient PM2.5 concentrations ranged from 18.2 to 303.0 μg m−3, among which >81% of the total sampling days exceeded the National Ambient Air Quality Standard of China (NAAQS, 35 μg m−3 as an annual average). Additionally, concentrations of PM2.5 and its major chemical components were seasonally dependent, usually with the highest mass concentration in winter. Compared with previous studies, higher NO3−/SO42− were observed in this study depicted that air pollution caused by motor vehicle exhaust cannot be ignored. OC concentration was higher at ZZ than XX during sampling campaign likely partially caused by larger number of motor vehicles, chemical pesticide and solvent used in ZZ. Both homogeneous and heterogeneous reactions played an important role in the formation of nitrate, while heterogeneous reactions dominated the formation of sulfate. We also found a faster increase in nitrate than in sulfate during the evolution of haze. The characteristics of long-range transportation of PM2.5 and its major chemical components and gaseous precursors were observed at both sites through back trajectories and WPSCF analysis, suggesting the complexity of air pollution and the multi-influence among cities.
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•Seasonal variation characteristics of PM2.5 and its chemical components are explored.•A faster increase in nitrate than in sulfate during the evolution of haze periods.•Severe pollution in winter has alleviated obviously compared with previous years.•Discrepancies of individual compositions of PM2.5 at both sites are significant.•Long-range transportation of PM2.5 is observed at both sites with WPSCF analysis.
Carbonaceous constituents have various adverse impacts on human health, visibility, and climate change. Although comprehensive studies on the characteristics of carbonaceous constituents have been ...conducted recently, systematic studies covering both the mass characteristics and light-absorption properties of carbonaceous constituents on a regional scale in China are quite limited. In this study, current seasonal measurements of organic carbon (OC) and elemental carbon (EC) in PM2.5 were investigated during autumn and winter (1–30 October 2017 and December 18, 2017 to January 17, 2018) in six selected cities located at the eastern foot of the Taihang Mountains: Beijing, Baoding, Shijiazhuang, Handan, Xinxiang, and Zhengzhou. Seasonal variations were similar when Beijing was excluded. The lowest concentrations of OC (18.33 ± 9.39 μg/m3) and EC (7.66 ± 5.64 μg/m3) were observed in Xinxiang (autumn) and Beijing (winter), respectively, while the highest concentrations of OC (38.43 ± 62.10 μg/m3) and EC (12.24 ± 24.67 μg/m3) occurred in Baoding during winter mainly due to elevated fuel combustion for space heating. The results of the potential source contribution function (PSCF) analysis suggested that border zones between several provinces in North China should be highlighted in order to strengthen pollution control. Moreover, by separating the optical properties of brown carbon from those of black carbon, we were able to estimate the contributions of brown carbon to the PM2.5 total light-absorption coefficient. The results show that the brown carbon absorption coefficient (at 405 nm) in winter at six sites accounted for 21.2%, 33.3%, 34.7%, 39.1%, 48.6%, and 23.3% of the PM2.5 light absorption, which are values that are comparable to the contribution of black carbon in Xinxiang. These results provide a more comprehensive understanding of carbonaceous constituents on a regional scale.
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•Significant seasonal variations of PM2.5 and its carbonaceous components were observed.•Seasonal variations of OC/EC and brown carbon highly relied on fuel used for heating.•Beijing showed the opposite seasonal characteristics compared with other cities.•Light absorption of brown carbon was comparable to black carbon in Xinxiang winter.
Natural sources, such as soil and wind-erosion dust (SWD), biomass open burning (BOB), sea salt spray (SSAS) and biogenic source (BIO), are major contributors to atmospheric emissions of trace ...elements (TEs) globally. In this study, we used a comprehensive approach to account for area-, production- and biofuel consumption-based emission factor calculation methods, and thus developed an integrated high-resolution emission inventory for 15 types of TEs (As, B, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn) originated from natural sources in China for the year 2015. The results show that national emissions of TEs in 2015 range from 7.45 tons (Hg) to 1, 400 tons (Zn) except for the extremely high emissions of Mn (10, 677 tons). SWD and BIO are identified as the top two source contributors, accounting for approximately 67.7% and 26.1% of the total emissions, respectively. Absolute emissions of TEs from natural sources are high in the Xinjiang, Inner Mongolia and Tibet autonomous regions with large areas of bare soil and desert. However, emission intensity of TEs per unit area in the Southern provinces of China is higher than those in Northern China and Southwestern China, with the Yunnan and Sichuan provinces displaying the highest emission intensity. Our results suggest that controlling SWD can play a significant role in reducing fugitive particulate matter and the associated emissions of TEs from natural sources in China; and desertification control is particularly critical in the Northwest provinces where the majority of deserts are located.
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•Emission of Mn (10, 677t) from natural sources ranks 1st in 15 trace elements in China.•Emissions of other elements in 2015 range from 7.45 tons (Hg) to 1, 400 tons (Zn).•Soil & wind-erosion dust and biogenic are identified as the two biggest contributors.•Soil & wind-erosion dust shared over 95% of total emission of Cr, Co, As, Mn and V.•Emission intensity per unit land is higher in Southern than that in Northern provinces.
The Hazardous air pollutants (HAPs) released from increasing municipal solid waste incineration (MSWI) plants have drawn great concerns in China. However, a full picture of their emission ...characteristics is still urgently needed, especially after the implementation of stricter emission limits on MSWI. In this study, a comprehensive historical emission inventory of HAPs emitted from MSWI plants in China during the period of 2006–2017 was dedicatedly established by integrating with detailed plant-level activity data and renewed localized emission factors. Overall, HAPs emissions initially increased with years, then peaked or slowed increase in the year 2014, but leveled off after 2016 due to the gradually and fully implementing of newly revised national emission standard (GB18485–2014) applied to mainland China and much stricter local standards for several provinces and cities. It was estimated that totally 50,716 tons (t) of NOx, 13,026 t of CO, 7988 t of SO2, 4399 t of PM, 1943 t of HCl, 9916 kg of Pb, 5901 kg of Mn, 4805 kg of Cu, 3574 kg of Cr, 3329 kg of Ni, 2154 kg of Hg, 1168 kg of Cd, 862 kg of As, 409 kg of Co, 216 kg of Sb, 13 kg of Tl, and 19 g toxic equivalent quantity of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans were emitted from 337 MSWI plants scattered in 30 provinces of mainland China in 2017, respectively. HAPs emissions were heavily concentrated in developed coastal provinces and cities. Scenario analysis highlighted the importance of continuous improvement and upgrade on advanced air pollution control devices and MSWI management to meet the future ultra-low emission limits and minimize the harmful impacts of HAPs on atmospheric environment and public health.
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•A refined inventory of HAPs from MSW incineration in China 2017 was established.•Temporal variations of HAPs emissions showed significant changes in 2014–2016.•HAPs emissions were mainly concentrated in developed and coastal provinces.•Scenario analysis highlighted continuous improvement on HAPs control technology.
To explore high-resolution temporal variation characteristics of atmospheric metal elements concentration and more accurate pollution sources apportionment, online monitoring of metal elements in ...PM2.5 with 1-h time resolution was conducted in Beijing from August 22, 2018 to August 21, 2019. Concentration of 18 elements varied between detection limit (ranging from 0.1 to 100 ng/m3) and nearly 25 μg/m3. Si, Fe, Ca, K and Al represented major elements and accounted for 93.47% of total concentration during the study period. Compared with previous studies, airborne metal pollution in Beijing has improved significantly which thanks to strict comprehensive control measures under the Clean Air Action Plan since 2013. Almost all elements present higher concentrations on weekdays than weekends, while concentrations of elements associated with dust sources during holidays are higher than those in working days after the morning peak, and there is almost no concentration difference in the evening peak period. Soil and dust, vehicle non-exhaust emissions, biomass, industrial processes and fuel combustion were apportioned as main sources of atmospheric metal pollution, accounting for 63.6%, 18.4%, 16.8%, 1.0% and 0.18%, respectively. Furthermore, main occurrence season of metal pollution is judged by characteristic radar chart of varied metal elements proposed for the first time in this study, for example, fuel combustion type pollution mainly occurs in winter and spring. Results of 72-h backward trajectory analysis of air masses showed that, except for local emissions, atmospheric metal pollution in Beijing is also affected by regional transport from Inner Mongolia, Hebei, the Bohai Sea and Heilongjiang.
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•Content of 18 metals in PM2.5 of Beijing with 1-h resolution for 1 year is gained.•Higher concentrations of metal elements are observed during weekdays than weekends.•K concentration in Beijing shows an order of winter > autumn > spring ≫ summer.•Soil and dust are identified as predominate source of metal elements in PM2.5.•Radar chart of metal elements is used for the first time to discern pollution type.
Temporal variations and source apportionment of metals are presented based on 1-h time resolution monitoring of metal elements in PM2.5 in Beijing from August 22, 2018 to August 21, 2019.
Toxic trace elements (TEs) can pose serious risks to ecosystems and human health. However, a comprehensive understanding of atmospheric emission inventories for several concerning TEs has not yet ...been developed. In this study, we systematically reviewed the status and progress of existing research in developing atmospheric emission inventories of TEs focusing on global, regional, and sectoral scales. Multiple studies have strengthened our understanding of the global emission of TEs, despite attention being mainly focused on Hg and source classification in different studies showing large discrepancies. In contrast to those of developed countries and regions, the officially published emission inventory is still lacking in developing countries, despite the fact that studies on evaluating the emissions of TEs on a national scale or one specific source category have been numerous in recent years. Additionally, emissions of TEs emitted from waste incineration and traffic-related sources have produced growing concern with worldwide rapid urbanization. Although several studies attempt to estimate the emissions of TEs based on PM emissions and its source-specific chemical profiles, the emission factor approach is still the universal method. We call for more extensive and in-depth studies to establish a precise localization national emission inventory of TEs based on adequate field measurements and comprehensive investigation to reduce uncertainty.
With the implementation of the Air Pollution Prevention and Control Action Plan (APPCAP) since 2013, significant declines in pollutants concentrations have achieved in nationwide of China. However, ...as one of the major coal-production bases and intensive energy-consuming provinces in China, Shanxi has still been suffering from severe air quality problems in recent years. In this study, by combining a detailed bottom-up emission inventory and the weather research and forecasting (WRF) model/comprehensive air quality model with extensions (CAMx) model, the evolution of pollutant concentrations, source apportionment, and migration potentials from 2012 to 2015 in Shanxi are investigated. Estimated primary air pollutants emission declined significantly during 2012–2015. Compared with 2012, the simulated concentrations of PM2.5, PM10, SO2 and NO2 in January of 2015 are reduced by 24.7%, 24.1%, 23.0% and 18.0%, respectively. In contrast, heavy contaminated areas have shown negligible variations, which are highly concentrated in Taiyuan, Linfen, Jincheng, Changzhi, Lvliang, Yangquan and Jinzhong cities. In terms of contribution by source categories, the other industries and residential sources are identified as the most significant local contributors for PM2.5 and PM10, while SO2 and NO2 are mainly emitted by other industries and power plants. Scenarios analysis of 50% emission mitigation suggests that the emission reduction measures are generally more effective in summer than in winter. Moreover, the mitigation potential for each city varies from each other. These results indicate that more appropriate seasonal-specific emission reduction measures in each prefecture-level city should be implemented to further improve regional air quality and thus better protect public health.
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•The first overall estimation of air pollution evolution in Shanxi is presented.•Spatial-temporal pollution characteristics are investigated by WRF-CAMx model.•Heavy contaminated areas have shown negligible variations from 2012 to 2015.•Industries, residential, and power plants are main local pollution contributors.•Mitigation potential for each city varies each other and more effective in summer.
To avoid the spread of COVID-19, China implemented strict prevention and control measures, resulting in dramatic variations in urban and regional air quality. With the complex effect from long-term ...emission mitigation and meteorology variation, an accurate evaluation of the net effect from lockdown on air quality changes has not been fully quantified. Here, we combined machine learning algorithm and Theil–Sen regression technique to eliminate meteorological and long-term trends effects on air pollutant concentrations and precisely detect concentrations changes those ascribed to lockdown measures in North China. Our results showed that, compared to the same period in 2015–2019, the adverse meteorology during the lockdown period (January 25th to March 15th) in early 2020 increased PM2.5 concentration in North China by 9.8 %, while the reduction of anthropogenic emissions led to a 32.2 % drop. Stagnant meteorological conditions have a more significant impact on the ground-level air quality in the Beijing-Tianjin-Hebei Region than that in Shanxi and Shandong provinces. After further striping out the effect of long-term emission reduction trend, the lockdown-derived NO2, PM2.5, and O3 shown variety change trend, and at −30.8 %, −27.6 %, and +10.0 %, respectively. Air pollutant changes during the lockdown could be overestimated up to 2-fold without accounting for the influences of meteorology and long-term trends. Further, with pollution reduction during the lockdown period, it would avoid 15,807 premature deaths in 40 cities. If with no deteriorate meteorological condition, the total avoided premature should increase by 1146.
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•Meteorological conditions have a positive contribution of about 9.8 % to PM2.5 in North China.•The deweathered air pollutants concentration decreased significantly from 2015 to 2019, especially for SO2.•Air pollutant changes during the lockdown could be overestimated 2-fold by using raw observation data.•There is still much room for PM2.5 pollution control in cities in Shanxi Province.•The total avoided premature deaths would increase by 1146 if the meteorological condition remains unchanged.
Volatile organic compounds (VOCs) are major precursors of ozone (O3) and secondary organic aerosols (SOA), which degrade air quality and pose a serious risk to human health and ecological systems. ...Previous studies on the emission characteristics of VOCs have predominantly focused on petrochemical and solvent-using sources, while localized studies on the cement industry are scarce in China. Field measurements for four cement plants were carried out in this study to investigate the emission levels, source profiles, and secondary pollutant generation potential of 98 VOCs species emitted from rotary and shaft kilns in China. Furthermore, a species-differentiated VOCs emission inventory was compiled for the Chinese cement industry in 2019. The results demonstrated that the mass concentration of VOCs emitted from shaft kiln was more than 20-fold higher than that emitted from rotary kilns, and the alkanes was the dominant species (56%) in shaft kilns, while oxygenated VOCs (OVOCs) and halocarbons were the main species in rotary kilns. Moreover, alkenes & alkyne were the dominant contributors to ozone formation potential (OFP) in shaft kilns, whereas alkenes & alkyne and OVOCs were comparable and prominent contributors in rotary kilns. In contrast, secondary organic aerosol potential (SOAP) for the two types of kilns was dominated by aromatics. In 2019, approximately 18.18 kt VOCs were emitted from cement production and were found to be largely concentrated in the southeast and central provinces of China. Considering the influence on environmental conditions, high OFP-contributing species in cement kilns are suggested to be a priority in the pollution mitigation of O3. This study provides a new, comprehensive, and reasonable cognition of the current VOCs emissions from both rotary and shaft kilns in China, which will aid in a better understanding of VOCs emission characteristics and guide future policy-making.
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•Oxygenated VOCs (32%) and halocarbons (28%) are the main species in rotary kilns.•Alkanes is the dominant species (56%) in shaft kilns.•VOCs emission factors of the shaft and rotary kilns are 0.32 and 0.01 g/kg-clinker.•About 18.18 kt VOCs emissions were emitted from cement kilns in China in 2019.•Emissions are highly concentrated in the central and southeast provinces of China.
Cement manufacturing is a major contributor to ambient particulate matter (PM) pollution in China, threatening urban and regional air quality improvement. Here, we tested the typical outlets (kiln ...tail, kiln head, and coal mill) in one shaft kiln and three rotary kilns to investigate the mass concentrations, size distributions, and chemical compositions of size-segregated PM. Results show that the concentrations of PM in most samples are lower than the strict local emission standards (10 mg/Nm3). We show that the characteristic chemical compositions in PM for most tested outlets are Ca and Ca2+, while for shaft kiln are K, S, K+, and SO42−, and organic carbon. Elemental carbon accounts for a relatively high proportion of PM emitted from coal mills. Meanwhile, unstable and abnormal operating conditions and variations on feed coal compositions will cause high levels of NH4+ and Cl− in PM from the kiln tail/head. Besides, the emission factors (EFs) of PM2.5, PM10, and PM after air pollution control devices for typical outlets of cement plants are calculated, which fall in ranges of 0.16–2.48, 1.49–18.46, and 3.32–35.35 g/(t of clinker), respectively. It suggests that mass emission characteristics, source profiles, and EFs of PM have changed notably as emission standards become more stringent. We believe the newly detailed size-segregated PM EFs and chemical profiles will help update and compile the refined emission inventory for current cement production in China.
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•The PM from kiln tail, kiln head, and coal mill of shaft/rotary kilns is studied.•Most stack PM concentrations are <10 mg/Nm3, with low PM2.5 in PM (3–9%).•Chemical profiles of size-segregated PM from shaft and rotary kilns are different.•EFs of PM2.5, PM10, and PM are 0.2–2.5, 1.5–18.5, and 3.3–35.4 g/t of clinker.•Source profiles/EFs of PM help to reflect current pollution levels of Chinese CPs.
