scholarly journals Mixing state of refractory black carbon in fog and haze at rural sites in winter on the North China Plain

2021 ◽  
Vol 21 (23) ◽  
pp. 17631-17648
Author(s):  
Yuting Zhang ◽  
Hang Liu ◽  
Shandong Lei ◽  
Wanyun Xu ◽  
Yu Tian ◽  
...  
Keyword(s):  
Mass Fraction ◽  
North China Plain ◽  
North China ◽  
Meteorological Conditions ◽  
Absorption Enhancement ◽  
Mixing State ◽  
The North ◽  
The North China Plain ◽  
Median Diameter ◽  
Rural Sites

Abstract. The variability of the mixing state of refractory black carbon aerosol (rBC) and the corresponding complicated light absorption capacity imposes great uncertainty for its climate forcing assessment. In this study, field observations using a single-particle soot photometer (SP2) were conducted to investigate the mixing state of rBC under different meteorological conditions at a rural site on the North China Plain. The results showed that the hourly mass concentration of rBC during the observation periods was 2.6±1.5 µg m−3 on average, with a moderate increase (3.1±0.9) during fog episodes. The mass-equivalent size distribution of rBC exhibited an approximately lognormal distribution with a mass median diameter (MMD) of 213 nm. We found that the count median diameter (CMD) of rBC particles during snowfall episodes was larger than that before snowfall, and the number of rBC particles with Dc<121 nm were reduced by 28.4 % after snow. This may indicate that rBC-containing particles with small core sizes (Dc) were much more effectively removed by snow with light snow intensity (0.23 mm h−1). Based on the Mie scattering theory simulation, the relative and absolute coating thicknesses of rBC-containing particles were estimated to be ∼1.6 and ∼52 nm for the rBC core with a mass-equivalent diameter (Dc) of 170 to 190 nm, respectively, which indicates that most of the rBC-containing particles were thinly coated. Furthermore, a moderate light absorption enhancement (Eabs=1.3) and relatively low absorption cross section (MAC = 5.5 m2 g−1) at 880 nm were observed at the Gucheng (GC) site in winter compared with other typical rural sites. The relationship between the microphysical properties of rBC and meteorological conditions was also studied. Relatively warm and high-RH environments (RH>50 %, -4∘C<T<4∘C) were more favorable to rBC aging than dry and cold environments (RH<60 %, T<-8∘C). And the increase in ambient RH at the same temperature favors rBC aging. An increasing mass fraction of secondary inorganic aerosols (SIAs; especially sulfate and nitrate) and a decreasing mass fraction of organic aerosols in the environment support the formation of thick coatings by rBC. The RH dependence of absorption enhancement (Eabs) was likely caused by the relative coating thickness (RCT) as supported by the gradual increase in the mass concentration and mass fraction of secondary components as a function of RH in the ambient air. The mass fractions of aqueous-phase formation of secondary components had a limited effect on Eabs under a high-RH environment. The measured rBC concentrations and the mixing state of rBC in different meteorological environments will be useful for evaluating the radiative forcing of rBC in regional climate models.

scholarly journals Mixing state of refractory black carbon in fog and haze at rural sites in winter on the North China Plain

2021 ◽  
Author(s):  
Yuting Zhang ◽  
Hang Liu ◽  
Shandong Lei ◽  
Wanyun Xu ◽  
Yu Tian ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
North China Plain ◽  
North China ◽  
Meteorological Conditions ◽  
Mixing State ◽  
The North ◽  
The North China Plain ◽  
Median Diameter ◽  
Rural Sites

Abstract. The variability of the mixing state of refractory black carbon aerosol (rBC) and the corresponding complicated light absorption capacity impose great uncertainty for its climate forcing assessment. In this study, field observations using a single particle soot photometer (SP2) were conducted to investigate the mixing state of rBC under different meteorological conditions at a rural site on the North China Plain. The results showed that the hourly mass concentration of rBC during the observation periods was 2.6 ± 1.5 µg m−3 on average with a moderate increase (3.1 ± 0.9) during fog episodes. The mass–equivalent size distribution of rBC exhibited an approximately lognormal distribution with a mass median diameter (MMD) of 213 nm. We found that the count median diameter (CMD) of rBC particles during snowfall episodes was obviously larger than that before–snowfall, indicating that smaller rBC–containing particles were much more effectively removed by snowfall. The droplet collision and Wegener–Bergeron–Findeisen (WBF) processes are possible explanations. Based on the Mie–scattering theory simulation, the relative and absolute coating thicknesses of rBC–containing particles were estimated to be 1.6 and ~52 nm for the rBC core with a mass–equivalent diameter (Dc) of 170–190 nm, respectively, indicating that the most of rBC–containing particles were thinly coated. Furthermore, moderate light absorption enhancement (Eabs = 1.3) and relatively low absorption cross–section (MAC = 5.5 m2/g) at 880 nm were observed at the GC site in winter compared with other typical rural sites. The relationships between the microphysical properties of rBC and meteorological conditions were also studied. We found that the coatings of rBC–containing particles increase only when both ambient RH and secondary components increase at the same time, with the thickest coating during fog events and the thinnest on clean days. And −4 ~ 0 °C may be the most suitable temperature range for coating formation of rBC in this study. The sulfate formation from aqueous–phases reactions may have a limited contribution to Eabs under high RH conditions (RH > 80 %). The enhancement of Eabs of rBC–containing particles was strongly related to an increase in the mass fraction of nitrate instead of organics at appropriate temperature conditions.

Characteristics of biological particulate matters at urban and rural sites in the North China Plain

2019 ◽  
Vol 253 ◽  
pp. 569-577 ◽  
Author(s):  
Fangxia Shen ◽  
Yunhao Zheng ◽  
Mutong Niu ◽  
Feng Zhou ◽  
Yan Wu ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Particulate Matters ◽  
The North ◽  
The North China Plain ◽  
Rural Sites

scholarly journals Influence of biomass burning on mixing state of sub-micron aerosol particles in the North China Plain

2017 ◽  
Vol 164 ◽  
pp. 259-269 ◽  
Author(s):  
Simonas Kecorius ◽  
Nan Ma ◽  
Monique Teich ◽  
Dominik van Pinxteren ◽  
Shenglan Zhang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
North China Plain ◽  
North China ◽  
Aerosol Particles ◽  
Mixing State ◽  
The North ◽  
The North China Plain

scholarly journals Aerosol hygroscopicity derived from size-segregated chemical composition and its parameterization in the North China Plain

2014 ◽  
Vol 14 (5) ◽  
pp. 2525-2539 ◽  
Author(s):  
H. J. Liu ◽  
C. S. Zhao ◽  
B. Nekat ◽  
N. Ma ◽  
A. Wiedensohler ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Ultrafine Particles ◽  
Mass Fraction ◽  
North China Plain ◽  
North China ◽  
The North ◽  
The North China Plain ◽  
Mass Fractions ◽  
Particulate Mass ◽  
Aerosol Hygroscopicity

Abstract. Hygroscopic growth of aerosol particles is of significant importance in quantifying the aerosol radiative effect in the atmosphere. In this study, hygroscopic properties of ambient particles are investigated based on particle chemical composition at a suburban site in the North China Plain during the HaChi campaign (Haze in China) in summer 2009. The size-segregated aerosol particulate mass concentration as well as the particle components such as inorganic ions, organic carbon and water-soluble organic carbon (WSOC) are identified from aerosol particle samples collected with a ten-stage impactor. An iterative algorithm is developed to evaluate the hygroscopicity parameter κ from the measured chemical composition of particles. During the HaChi summer campaign, almost half of the mass concentration of particles between 150 nm and 1 μm is contributed by inorganic species. Organic matter (OM) is abundant in ultrafine particles, and 77% of the particulate mass with diameter (Dp) of around 30 nm is composed of OM. A large fraction of coarse particle mass is undetermined and is assumed to be insoluble mineral dust and liquid water. The campaign's average size distribution of κ values shows three distinct modes: a less hygroscopic mode (Dp < 150 nm) with κ slightly above 0.2, a highly hygroscopic mode (150 nm < Dp < 1 μm) with κ greater than 0.3 and a nearly hydrophobic mode (Dp > 1 μm) with κ of about 0.1. The peak of the κ curve appears around 450 nm with a maximum value of 0.35. The derived κ values are consistent with results measured with a high humidity tandem differential mobility analyzer within the size range of 50–250 nm. Inorganics are the predominant species contributing to particle hygroscopicity, especially for particles between 150 nm and 1 μm. For example, NH4NO3, H2SO4, NH4HSO4 and (NH4)2SO4 account for nearly 90% of κ for particles of around 900 nm. For ultrafine particles, WSOC plays a critical role in particle hygroscopicity due to the predominant mass fraction of OM in ultrafine particles. WSOC for particles of around 30 nm contribute 52% of κ. Aerosol hygroscopicity is related to synoptic transport patterns. When southerly wind dominates, particles are more hygroscopic; when northerly wind dominates, particles are less hygroscopic. Aerosol hygroscopicity also has a diurnal variation, which can be explained by the diurnal evolution of planetary boundary layer, photochemical aging processes during daytime and enhanced black carbon emission at night. κ is highly correlated with mass fractions of SO42−, NO3− and NH4+ for all sampled particles as well as with the mass fraction of WSOC for particles of less than 100 nm. A parameterization scheme for κ is developed using mass fractions of SO42−, NO3−, NH4+ and WSOC due to their high correlations with κ, and κ calculated from the parameterization agrees well with κ derived from the particle's chemical composition. Further analysis shows that the parameterization scheme is applicable to other aerosol studies in China.

Secondary aerosol formation alters CCN activity in the North China Plain

2021 ◽  
Author(s):  
Jiangchuan Tao ◽  
Ye Kuang ◽  
Nan Ma ◽  
Juan Hong ◽  
Yele Sun ◽  
...  
Keyword(s):  
Particle Size ◽  
North China Plain ◽  
North China ◽  
Particle Mass ◽  
Mixing State ◽  
Particle Size Range ◽  
The North ◽  
The North China Plain ◽  
Aerosol Mixing State ◽  
Ccn Activity

&lt;p&gt;The formation of secondary aerosols (SA, including secondary organic and inorganic aerosols, SOA and SIA) were the dominant sources of aerosol particles in the North China Plain and can result in significant variations of particle size distribution (PNSD) and hygroscopicity. Earlier studies have shown that the mechanism of SA formation can be affected by relative humidity (RH), and thus has different influences on the aerosol hygroscopicity and PNSD under different RH conditions. Based on the measurements of size-resolved particle activation ratio (SPAR), hygroscopicity distribution (GF-PDF), PM&lt;sub&gt;2.5&lt;/sub&gt; chemical composition, PNSD, meteorology and gaseous pollutants in a recent field campaign McFAN (Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain) conducted at Gucheng site from November 16&lt;sup&gt;th&lt;/sup&gt; to December 16&lt;sup&gt;th&lt;/sup&gt; in 2018, the influences of SA formation on CCN activity and CCN number concentration (N&lt;sub&gt;CCN&lt;/sub&gt;) calculation at super-saturation of 0.05% under different RH conditions were studied. Measurements showed that during daytime, SA formation could lead to a significant increase in N&lt;sub&gt;CCN&lt;/sub&gt; and a strong diurnal variation in CCN activity. During periods with daytime minimum RH exceeding 50% (high RH conditions), SA formation significantly contributed to the particle mass/size changes in wide particle size range of 150 nm to 1000 nm, and led to an increase of N&lt;sub&gt;CCN&lt;/sub&gt; in particle size range of 200 nm to 300 nm, while increases in particle mass concentration mainly occurred within particle sizes larger than 300nm. During periods with daytime minimum RH below 30% in (low RH conditions), SA formation mainly contributed to the particle mass/size and N&lt;sub&gt;CCN&lt;/sub&gt; changes in particle sizes smaller than 300 nm. As a result, under the same amount SA formation induced mass increase, the increase of N&lt;sub&gt;CCN&lt;/sub&gt; was weaker under high RH conditions, while stronger under low RH conditions. Moreover, the diurnal variations of aerosol mixing state (inferred from CCN measurements) due to SA formation was different under different RH conditions. If the variations of the aerosol mixing state were not considered, estimations of N&lt;sub&gt;CCN&lt;/sub&gt; would bear significant deviations. By applying aerosol mixing state estimated by number fraction of hygroscopic particles from measurements of particle hygroscopicity or mass fraction of SA from measurements of particle chemical compositions, N&lt;sub&gt;CCN&lt;/sub&gt; calculation can be largely improved with relative deviation within 30%. This study improves the understanding of the impact of SA formation on CCN activity and N&lt;sub&gt;CCN&lt;/sub&gt; calculation, which is of great significance for improving parameterization of SA formation in aerosol models and CCN calculation in climate models.&lt;/p&gt;

Influence of size and mixing state on the wet scavenging of black carbon aerosol in the North China Plain

2020 ◽  
Author(s):  
Xihao Pan ◽  
Nan Ma ◽  
Yaqing Zhou ◽  
Shaowen Zhu ◽  
Long Peng ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Mixing State ◽  
Radiation Fog ◽  
The North ◽  
The North China Plain ◽  
Positive Direct ◽  
Scavenging Efficiency

&lt;p&gt;Black carbon (BC) is the most important light-absorbing species in the atmosphere and has a strong positive direct radiative forcing. In-cloud scavenging is the major way to wash out BC from the atmosphere. Understanding the connection between its physico-chemical properties and scavenging efficiency is therefore a key to evaluate its lifetime, atmospheric burden and spatial distribution. During an intensive field campaign conducted in the North China Plain in 2019, a ground-based counterflow virtual impactor was utilized to separate fog droplets in radiation fog events. BC mass and mixing state of fog droplet residues were online measured with a single particle soot photometer (SP2). In a strong radiation fog event with visibility of about 50 m, more than 20% fog droplets are found to contain a BC core. BC scavenging efficiency is found to be strongly determined by its diameter and mixing state. Driven by different mechanisms, higher scavenging efficiencies up to 10% are observed for larger and smaller BC particles, and the minimum efficiency is found at BC diameter of 120 nm. For large core (&gt;120 nm) BC-containing particles, the scavenging efficiency increases significantly with coating thickness (CT), from about 10% for CT&lt;100 nm to 80% for CT&gt;300 nm. Chemical composition may also be a key parameter influencing the scavenging of BC. Based on the observation of 3 fog events, parameterizations of BC scavenging efficiency are also given in this study.&lt;/p&gt;

Mass-based mixing state of black carbon measured by a tandem CPMA-SP2 system in wintertime in the North China Plain

2020 ◽  
Author(s):  
Shaowen Zhu ◽  
Nan Ma ◽  
Xihao Pan ◽  
Wenlin Dong ◽  
Jiangchuan Tao ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Data Retrieval ◽  
Particle Mass ◽  
Radiative Properties ◽  
Mass Analyzer ◽  
Mixing State ◽  
The North ◽  
The North China Plain

&lt;p&gt;Black carbon (BC) is the most important light absorbing component in the atmosphere and has significant impacts on the climate, environment and public health. Its effects depend not only on its spatial-temporal distribution, but also on its physico-chemical characteristics. Mixing state is one of the most important properties of BC and strongly determines its hygroscopicity and radiative properties. During an intensive field campaign conducted in the North China Plain in winter 2018, mass-based mixing state of BC-containing particles were online measured with a Centrifugal Particle Mass Analyzer and Single Particle Soot Photometer (CPMA-SP2) tandem system. This technique directly provides the mass ratio of non-refractory coating matter to BC core (M&lt;sub&gt;R&lt;/sub&gt;) in individual particles and does not require to assume the density, morphology and refractive index of BC core and coating in data retrieval, therefore has lower uncertainly compared with leading-edge fit technique. In our measurement, the mean number fraction of uncoated (M&lt;sub&gt;R&lt;/sub&gt;=0), thin coated (0&lt;M&lt;sub&gt;R&lt;/sub&gt;&lt;3) and thick coated (M&lt;sub&gt;R&lt;/sub&gt;&amp;#8805;3) BC-containing particle during the campaign were respectively ~10%, ~35% and ~55%, indicating the strong aging process of BC-containing particle in the North China Plain. The median value of M&lt;sub&gt;R&lt;/sub&gt; was much higher in polluted days than clean days, for example, the median value of M&lt;sub&gt;R&lt;/sub&gt; with a particle mass of 8.56 fg (~220 nm in diameter) for polluted and clean days were ~3.2 and ~1.6, respectively. The mixing state of BC-containing particles obtained by different methods were also compared and evaluated.&lt;/p&gt;

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