scholarly journals Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity

2012 ◽  
Vol 12 (2) ◽  
pp. 4755-4796 ◽  
Author(s):  
U. Makkonen ◽  
A. Virkkula ◽  
J. Mäntykenttä ◽  
H. Hakola ◽  
P. Keronen ◽  
...  
Keyword(s):  
Particle Number ◽  
Road Traffic ◽  
Large Fraction ◽  
Inorganic Ions ◽  
Urban Site ◽  
Vehicle Exhaust ◽  
Gas Phases ◽  
Aerosol Acidity ◽  
Inorganic Aerosol ◽  
Online Monitor

Abstract. Concentrations of 5 gases (HCl, HNO3, HONO, NH3, SO2) and 8 major inorganic ions in particles (Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, Ca2+) were measured with an online monitor MARGA 2S in two size ranges, Dp < 2.5 μm and Dp < 10 μm, in Helsinki, Finland from November 2009 to May 2010. The results were compared with filter sampling, mass concentrations obtained from particle number size distributions, and a conventional SO2 monitor. The MARGA yielded lower concentrations than those analyzed from the filter samples for most ions. Linear regression yielded MARGA vs. filter slopes of 0.68, 0.89, 0.84, 0.52, 0.88, 0.17, 2.88, and 3.04 for Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, and Ca2+, respectively, and 0.90 for the MARGA vs. SO2 monitor. There were clear seasonal cycles in the concentrations of the nitrogen-containing gases: the median concentrations of HNO3, HONO, and NH3 were 0.09 ppb, 0.37 ppb, and 0.01 ppb in winter, respectively, and 0.15, 0.15, and 0.14 in spring, respectively. The gas-phase fraction of nitrogen decreased roughly with decreasing temperature so that in the coldest period from January to February the median contribution was 28% but in April to May 53%. There were also large fractionation variations that temperature alone cannot explain. HONO correlated well with NOx but a large fraction of the HONO-to-NOx ratios were larger than published ratios in a road traffic tunnel suggesting that a large amount of HONO had other sources than vehicle exhaust. Aerosol acidity was estimated by calculating ion equivalent ratios. The sources of acidic aerosols were studied with trajectory statistics that showed that continental aerosol is mainly neutralized and marine aerosol acidic.

scholarly journals Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity

2012 ◽  
Vol 12 (12) ◽  
pp. 5617-5631 ◽  
Author(s):  
U. Makkonen ◽  
A. Virkkula ◽  
J. Mäntykenttä ◽  
H. Hakola ◽  
P. Keronen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Road Traffic ◽  
Large Fraction ◽  
Inorganic Ions ◽  
Urban Site ◽  
Vehicle Exhaust ◽  
Gas Phases ◽  
Aerosol Acidity ◽  
Data Points ◽  
Online Monitor

Abstract. Concentrations of 5 gases (HCl, HNO3, HONO, NH3, SO2) and 8 major inorganic ions in particles (Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, Ca2+) were measured with an online monitor MARGA 2S in two size ranges, Dp <2.5 μm and Dp < 10 μm, in Helsinki, Finland from November 2009 to May 2010. The results were compared with filter sampling, mass concentrations obtained from particle number size distributions, and a conventional SO2 monitor. The MARGA yielded lower concentrations than those analyzed from the filter samples for most ions. Linear regression yielded the following MARGA vs. filter slopes: 0.72 for Cl−, 0.90 for NO3−, 0.85 for SO42−, 0.91 for NH4+ , 0.49 for Na+, 3.0 for Mg2+, and 3.0 for Ca2+ and 0.90 for the MARGA vs. SO2 monitor. For K+ there were not enough data points to calculate a statistically significant linear regression. There were clear seasonal cycles in the concentrations of the nitrogen-containing gases: the median concentrations of HNO3, HONO, and NH3 were 0.09 ppb, 0.37 ppb, and 0.01 ppb in winter, respectively, and 0.15, 0.15, and 0.14 in spring, respectively. The gas-phase fraction of nitrogen decreased roughly with decreasing temperature, so that in the coldest period from January to February the median contribution was 28% but in April to May was 53%. There were also large fractionation variations that temperature alone cannot explain. HONO correlated well with NOx but a large fraction of the HONO-to-NOx ratios were larger than published ratios in a road traffic tunnel, suggesting that a large amount of HONO had other sources than vehicle exhaust. Aerosol acidity was estimated by calculating ion equivalent ratios. The sources of acidic aerosols were studied with trajectory statistics that showed that continental aerosol is mainly neutralized and marine aerosol acidic.

scholarly journals Spatial and seasonal variability of PM<sub>2.5</sub> acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols

2012 ◽  
Vol 12 (3) ◽  
pp. 1377-1395 ◽  
Author(s):  
K. He ◽  
Q. Zhao ◽  
Y. Ma ◽  
F. Duan ◽  
F. Yang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Temporal Variations ◽  
Early Summer ◽  
Heterogeneous Reactions ◽  
Rural Site ◽  
Urban Site ◽  
Simultaneous Increase ◽  
Northwestern Pacific ◽  
Inorganic Aerosols ◽  
Aerosol Acidity

Abstract. Aerosol acidity is one of the most important parameters influencing atmospheric chemistry and physics. Based on continuous field observations from January 2005 to May 2006 and thermodynamic modeling, we investigated the spatial and seasonal variations in PM2.5 acidity in two megacities in China, Beijing and Chongqing. Spatially, PM2.5 was generally more acidic in Chongqing than in Beijing, but a reverse spatial pattern was found within the two cities, with more acidic PM2.5 at the urban site in Beijing whereas the rural site in Chongqing. Ionic compositions of PM2.5 revealed that it was the higher concentrations of NO3− at the urban site in Beijing and the lower concentrations of Ca2+ within the rural site in Chongqing that made their PM2.5 more acidic. Temporally, PM2.5 was more acidic in summer and fall than in winter, while in the spring of 2006, the acidity of PM2.5 was higher in Beijing but lower in Chongqing than that in 2005. These were attributed to the more efficient formation of nitrate relative to sulfate as a result of the influence of Asian desert dust in 2006 in Beijing and the greater wet deposition of ammonium compared to sulfate and nitrate in 2005 in Chongqing. Furthermore, simultaneous increase of PM2.5 acidity was observed from spring to early summer of 2005 in both cities. This synoptic-scale evolution of PM2.5 acidity was accompanied by the changes in air masses origins, which were influenced by the movements of a subtropical high over the northwestern Pacific in early summer. Finally, the correlations between [NO3−]/[SO42−] and [NH4+]/[SO42−] suggests that under conditions of high aerosol acidity, heterogeneous reactions became one of the major pathways for the formation of nitrate at both cities. These findings provided new insights in our understanding of the spatial and temporal variations in aerosol acidity in Beijing and Chongqing, as well as those reported in other cities in China.

scholarly journals Continental anthropogenic primary particle number emissions

2016 ◽  
Vol 16 (11) ◽  
pp. 6823-6840 ◽  
Author(s):  
Pauli Paasonen ◽  
Kaarle Kupiainen ◽  
Zbigniew Klimont ◽  
Antoon Visschedijk ◽  
Hugo A. C. Denier van der Gon ◽  
...  
Keyword(s):  
Particle Number ◽  
Road Traffic ◽  
Agricultural Waste ◽  
Coke Production ◽  
Strong Increase ◽  
Size Distributions ◽  
Adverse Health Effects ◽  
Carbon Particles ◽  
First Results ◽  
Aerosol Cloud Interactions

Abstract. Atmospheric aerosol particle number concentrations impact our climate and health in ways different from those of aerosol mass concentrations. However, the global, current and future anthropogenic particle number emissions and their size distributions are so far poorly known. In this article, we present the implementation of particle number emission factors and the related size distributions in the GAINS (Greenhouse Gas–Air Pollution Interactions and Synergies) model. This implementation allows for global estimates of particle number emissions under different future scenarios, consistent with emissions of other pollutants and greenhouse gases. In addition to determining the general particulate number emissions, we also describe a method to estimate the number size distributions of the emitted black carbon particles. The first results show that the sources dominating the particle number emissions are different to those dominating the mass emissions. The major global number source is road traffic, followed by residential combustion of biofuels and coal (especially in China, India and Africa), coke production (Russia and China), and industrial combustion and processes. The size distributions of emitted particles differ across the world, depending on the main sources: in regions dominated by traffic and industry, the number size distribution of emissions peaks in diameters range from 20 to 50 nm, whereas in regions with intensive biofuel combustion and/or agricultural waste burning, the emissions of particles with diameters around 100 nm are dominant. In the baseline (current legislation) scenario, the particle number emissions in Europe, Northern and Southern Americas, Australia, and China decrease until 2030, whereas especially for India, a strong increase is estimated. The results of this study provide input for modelling of the future changes in aerosol–cloud interactions as well as particle number related adverse health effects, e.g. in response to tightening emission regulations. However, there are significant uncertainties in these current emission estimates and the key actions for decreasing the uncertainties are pointed out.

Air pollution in an urban street canyon: Novel insights from highly resolved traffic information and meteorology

2021 ◽  
Author(s):  
Laura Ehrnsperger ◽  
Otto Klemm
Keyword(s):  
Air Pollution ◽  
Temporal Dynamics ◽  
Road Traffic ◽  
Ambient Air ◽  
Ambient Air Pollution ◽  
Traffic Information ◽  
Pollutant Emission ◽  
Urban Site ◽  
Gasoline Vehicles ◽  
Agricultural Areas

&lt;p&gt;Ambient air pollution caused by fine particulate matter (PM) and trace gases is a pressing topic as it affects the vast majority of the world's population, especially in densely populated urban environments. The main sources of ambient air pollution in cities are road traffic, industries and domestic heating. Alongside nitrogen oxides (NO&lt;sub&gt;x&lt;/sub&gt;) and PM, ammonia (NH&lt;sub&gt;3&lt;/sub&gt;) is also a relevant air pollutant due to its role as a precursor of particulate ammonium (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;). To examine the temporal patterns and sources of air pollutants, this study used fast-response air quality measurements in combination with highly resolved traffic information in M&amp;#252;nster, NW Germany. The temporal dynamics of NO&lt;sub&gt;x&lt;/sub&gt; and the particle number concentration (PN&lt;sub&gt;10&lt;/sub&gt;) were similar to the diurnal and weekly courses of the traffic density. On very short timescales, the real-world peak ratios of NO&lt;sub&gt;x&lt;/sub&gt; and PM&amp;#160;&amp;#8804;&amp;#160;10&amp;#160;&amp;#181;m diameter (PM&lt;sub&gt;10&lt;/sub&gt;) exceeded the predicted pollutant emission ratios of the Handbook for Emission Factors for Road Transport (HBEFA) by a factor of 6.4 and 2.0, respectively. A relative importance model revealed that light-duty vehicles (LDVs) are the major relative contributor to PN&lt;sub&gt;10&lt;/sub&gt; (38&amp;#160;%) despite their low abundance (4&amp;#160;%) in the local vehicle fleet.&amp;#160; Diesel and gasoline vehicles contributed similarly to the concentrations of PM&lt;sub&gt;10&lt;/sub&gt; and PN&lt;sub&gt;10&lt;/sub&gt;, while the impact of gasoline vehicles on the PM&lt;sub&gt;1&lt;/sub&gt; concentration was greater than that of diesel vehicles by a factor of 4.4. The most recent emission class Euro&amp;#160;6 had the highest influence on PM&lt;sub&gt;10&lt;/sub&gt;. Meteorological parameters explained a large portion of the variations in PM&lt;sub&gt;10&lt;/sub&gt; and PM&lt;sub&gt;1&lt;/sub&gt;, while meteorology had only a minor influence on PN&lt;sub&gt;10&lt;/sub&gt;. We also studied the short-term temporal dynamics of urban NH&lt;sub&gt;3 &lt;/sub&gt;concentrations, the role of road traffic and agriculture as NH&lt;sub&gt;3&lt;/sub&gt; sources and the importance of ammonia for secondary particle formation (SPF). The NH&lt;sub&gt;3&lt;/sub&gt; mixing ratio was rather high (mean:&amp;#160;17&amp;#160;ppb) compared to other urban areas and showed distinct diurnal maxima around 10 a.m. and 9&amp;#160;p.m. The main source for ammonia in M&amp;#252;nster was agriculture, but road traffic also contributed through local emissions from vehicle catalysts. NH&lt;sub&gt;3&lt;/sub&gt; from surrounding agricultural areas accumulated in the nocturnal boundary layer and contributed to SPF in the city center. The size-resolved chemical composition of inorganic ions in PM&lt;sub&gt;10&lt;/sub&gt; was dominated by NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; (8.7&amp;#160;&amp;#181;g&amp;#160;m&lt;sup&gt;-3&lt;/sup&gt;), followed by NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; (3.9&amp;#160;&amp;#181;g&amp;#160;m&lt;sup&gt;-3&lt;/sup&gt;), SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; (1.6&amp;#160;&amp;#181;g&amp;#160;m&lt;sup&gt;-3&lt;/sup&gt;) and Cl&lt;sup&gt;-&lt;/sup&gt; (1.3&amp;#160;&amp;#181;g&amp;#160;m&lt;sup&gt;-3&lt;/sup&gt;). Particles in the accumulation range (diameter: 0.1&amp;#160;&amp;#8211;&amp;#160;1&amp;#160;&amp;#181;m) showed the highest inorganic ion concentrations. The ammonium neutralization index J (111&amp;#160;%) indicated an excess of NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; leading to mostly alkaline PM. High ammonia emissions from surrounding agricultural areas combined with large amounts of NO&lt;sub&gt;x&lt;/sub&gt; from road traffic play a crucial role for SPF in M&amp;#252;nster. Our results further indicate that replacing fossil-fuelled LDVs with electrical vehicles would greatly reduce the PN&lt;sub&gt;10&lt;/sub&gt; concentrations at this urban site.&lt;/p&gt;

scholarly journals Continental anthropogenic primary particle number emissions

2016 ◽  
Author(s):  
P. Paasonen ◽  
K. Kupiainen ◽  
Z. Klimont ◽  
A. Visshedijk ◽  
H. A. C. Denier van der Gon ◽  
...  
Keyword(s):  
Particle Number ◽  
Road Traffic ◽  
Agricultural Waste ◽  
Coke Production ◽  
Strong Increase ◽  
Size Distributions ◽  
Adverse Health Effects ◽  
First Results ◽  
Particulate Number ◽  
Aerosol Cloud Interactions

Abstract. Atmospheric aerosol particle number concentrations impact our climate and health in ways different from those of aerosol mass concentrations. However, the global, current and future, anthropogenic particle number emissions and their size distributions are so far poorly known. In this article, we present the implementation of particle number emission factors and the related size distributions in the GAINS model. This implementation allows for global estimates of particle number emissions under different future scenarios, consistent with emissions of other pollutants and greenhouse gases. In addition to determining the general particulate number emissions, we also describe a method to estimate the number size distributions of the emitted black carbon. The first results show that the sources dominating the particle number emissions are different to those dominating the mass emissions. The major global number source is road traffic, followed by residential combustion of biofuels and coal (especially in China, India and Africa), coke production (Russia and China), and industrial combustion and processes. The size distributions of emitted particles differ across the world, depending on the main sources: in regions dominated by traffic and industry, the number size distribution of emissions peaks in diameters range from 20 to 50 nm, whereas in regions with intensive biofuel combustion and/or agricultural waste burning, the emissions of particles with diameters around 100 nm are dominant. In the baseline (current legislation) scenario, the particle number emissions in Europe, Northern and Southern Americas, Australia, and China decrease until 2030, whereas especially for India, a strong increase is estimated. The results of this study provide input for modelling of the future changes in aerosol-cloud interactions as well as particle number related adverse health effects, e.g., in response to tightening emission regulations. However, there are significant uncertainties in these current emission estimates and the key actions for decreasing the uncertainties are pointed out.

scholarly journals Characteristics of PM2.5 Chemical Compositions and Their Effect on Atmospheric Visibility in Urban Beijing, China during the Heating Season

2018 ◽  
Vol 15 (9) ◽  
pp. 1924 ◽  
Author(s):  
Xing Li ◽  
Shanshan Li ◽  
Qiulin Xiong ◽  
Xingchuan Yang ◽  
Mengxi Qi ◽  
...  
Keyword(s):  
Fine Particles ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Motor Vehicles ◽  
Urban Site ◽  
Chemical Compositions ◽  
Heating Season ◽  
Atmospheric Visibility ◽  
Visibility Impairment ◽  
Mass Concentrations

Beijing, which is the capital of China, suffers from severe Fine Particles (PM2.5) pollution during the heating season. In order to take measures to control the PM2.5 pollution and improve the atmospheric environmental quality, daily PM2.5 samples were collected at an urban site from 15 November to 31 December 2016, characteristics of PM2.5 chemical compositions and their effect on atmospheric visibility were analyzed. It was found that the daily average mass concentrations of PM2.5 ranged from 7.64 to 383.00 μg m−3, with an average concentration of 114.17 μg m−3. On average, the Organic Carbon (OC) and Elemental Carbon (EC) contributed 21.39% and 5.21% to PM2.5, respectively. Secondary inorganic ions (SNA: SO42− + NO3− + NH4+) dominated the Water-Soluble Inorganic Ions (WSIIs) and they accounted for 47.09% of PM2.5. The mass concentrations of NH4+, NO3− and SO42− during the highly polluted period were 8.08, 8.88 and 6.85 times greater, respectively, than during the clean period, which contributed most to the serious PM2.5 pollution through the secondary transformation of NO2, SO2 and NH3. During the highly polluted period, NH4NO3 contributed most to the reconstruction extinction coefficient (b′ext), accounting for 35.7%, followed by (NH4)2SO4 (34.44%) and Organic Matter (OM: 15.24%). The acidity of PM2.5 in Beijing was weakly acid. Acidity of PM2.5 and relatively high humidity could aggravate PM2.5 pollution and visibility impairment by promoting the generation of secondary aerosol. Local motor vehicles contributed the most to NO3−, OC, and visibility impairment in urban Beijing. Other sources of pollution in the area surrounding urban Beijing, including coal burning, agricultural sources, and industrial sources in the Hebei, Shandong, and Henan provinces, released large amounts of SO2, NH3, and NO2. These, which were transformed into SO42−, NH4+, and NO3− during the transmission process, respectively, and had a great impact on atmospheric visibility impairment.

scholarly journals Chemical Composition and Source Apportionment of PM2.5 in Urban Areas of Xiangtan, Central South China

2019 ◽  
Vol 16 (4) ◽  
pp. 539 ◽  
Author(s):  
Xiaoyao Ma ◽  
Zhenghui Xiao ◽  
Lizhi He ◽  
Zongbo Shi ◽  
Yunjiang Cao ◽  
...  
Keyword(s):  
Source Apportionment ◽  
South China ◽  
Urban Areas ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Total Carbon ◽  
Anthropogenic Sources ◽  
Vehicle Exhaust ◽  
Industrial Emissions ◽  
Wind Speeds

Xiangtan, South China, is characterized by year-round high relative humidity and very low wind speeds. To assess levels of PM2.5, daily samples were collected from 2016 to 2017 at two urban sites. The mass concentrations of PM2.5 were in the range of 30–217 µg/m3, with the highest concentrations in winter and the lowest in spring. Major water-soluble ions (WSIIs) and total carbon (TC) accounted for 58–59% and 21–24% of the PM2.5 mass, respectively. Secondary inorganic ions (SO42−, NO3−, and NH4+) dominated the WSIIs and accounted for 73% and 74% at the two sites. The concentrations of K, Fe, Al, Sb, Ca, Zn, Mg, Pb, Ba, As, and Mn in the PM2.5 at the two sites were higher than 40 ng/m3, and decreased in the order of winter > autumn > spring. Enrichment factor analysis indicates that Co, Cu, Zn, As, Se, Cd, Sb, Tl, and Pb mainly originates from anthropogenic sources. Source apportionment analysis showed that secondary inorganic aerosols, vehicle exhaust, coal combustion and secondary aerosols, fugitive dust, industrial emissions, steel industry are the major sources of PM2.5, contributing 25–27%, 21–22%, 19–21%, 16–18%, 6–9%, and 8–9% to PM2.5 mass.

scholarly journals Ion-molecule interactions enable unexpected phase transitions in organic-inorganic aerosol

2020 ◽  
Vol 6 (47) ◽  
pp. eabb5643 ◽  
Author(s):  
David S. Richards ◽  
Kristin L. Trobaugh ◽  
Josefina Hajek-Herrera ◽  
Chelsea L. Price ◽  
Craig S. Sheldon ◽  
...  
Keyword(s):  
Air Quality ◽  
Inorganic Ions ◽  
Climate Projections ◽  
Atmospheric Models ◽  
Inorganic Aerosols ◽  
Low Mass ◽  
Inorganic Aerosol ◽  
Semi Solid ◽  
Molecule Interactions ◽  
Inorganic Fraction

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) and divalent inorganic ions. This supramolecular, ion-molecule effect can drastically influence the phase and physical properties of organic-inorganic aerosol and suggests that aerosol may be (semi)solid under more conditions than currently predicted. These observations, thus, have implications for air quality and climate that are not fully represented in atmospheric models.

scholarly journals Exploring wintertime regional haze in Northeast China: role of coal and biomass burning

2020 ◽  
Author(s):  
Jian Zhang ◽  
Lei Liu ◽  
Liang Xu ◽  
Qiuhan Lin ◽  
Hujia Zhao ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Northeast China ◽  
Climate Models ◽  
Inorganic Ions ◽  
Heterogeneous Reactions ◽  
Urban Site ◽  
Particle Analysis ◽  
Aerosol Formation ◽  
Mountain Site ◽  
Regional Haze

Abstract. As one of the intense anthropogenic emission regions across the relatively high latitude (> 40° N) areas on the Earth, Northeast China faces serious problem on regional haze during long winter with half a year. Aerosols in polluted haze in Northeast China are poorly understood compared with the haze in other regions of China such as North China Plain. Here, we for the first time integrated bulk chemical measurements with single particle analysis from transmission electron microscopy (TEM), nanoscale secondary ion mass spectrometer (NanoSIMS), and atomic force microscopy (AFM) to obtain morphology, size, composition, aging process, and sources of aerosol particles collected during two contrasting regional haze events (Haze-I and Haze-II) at an urban site and a mountain site in Northeast China, and further investigated the causes of regional haze formation. Haze-I evolved from moderate (average PM2.5: 76–108 μg/m3) to heavy pollution (151–154 μg/m3), with the dominant PM2.5 component changing from organic matter (OM) (39–45 μg/m3) to secondary inorganic ions (94–101 μg/m3). Similarly, TEM observations showed that S-OM particles elevated from 29 % to 60 % by number at urban site and 64 % to 74 % at mountain site and 75–96 % of Haze-I particles included primary OM. Change of wind direction induced that Haze-I rapidly turned into Haze-II (185–223 μg/m3) with the predominant OM (98–133 μg/m3) and unexpectedly high K+ (3.8 μg/m3). TEM also showed that K-OM particles increased from 4–5 % by number to 50–52 %. Our study revealed a contrasting formation mechanism of these two haze events: Haze-I was induced by accumulation of primary OM emitted from residential coal burning and further deteriorated by secondary aerosol formation via heterogeneous reactions; Haze-II was caused by long-range transport of agricultural biomass burning emissions. Moreover, we found that 75–97 % of haze particles contained tarballs, but only 4–23 % contained black carbon and its concentrations were low at 2.7–4.3 μg/m3. The results highlight that abundant tarballs are important light-absorbing brown carbon in Northeast China during winter haze and further considered in climate models.

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