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

<p>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<sub>R</sub>) 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<sub>R</sub>=0), thin coated (0<M<sub>R</sub><3) and thick coated (M<sub>R</sub>≥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<sub>R</sub> was much higher in polluted days than clean days, for example, the median value of M<sub>R</sub> 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.</p>

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

<p>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<sub>2.5</sub> 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<sup>th</sup> to December 16<sup>th</sup> in 2018, the influences of SA formation on CCN activity and CCN number concentration (N<sub>CCN</sub>) 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<sub>CCN</sub> 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<sub>CCN</sub> 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<sub>CCN</sub> changes in particle sizes smaller than 300 nm. As a result, under the same amount SA formation induced mass increase, the increase of N<sub>CCN</sub> 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<sub>CCN</sub> 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<sub>CCN</sub> 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<sub>CCN</sub> calculation, which is of great significance for improving parameterization of SA formation in aerosol models and CCN calculation in climate models.</p>

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

<p>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 (>120 nm) BC-containing particles, the scavenging efficiency increases significantly with coating thickness (CT), from about 10% for CT<100 nm to 80% for CT>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.</p>

scholarly journals Measurement report: Source and mixing state of black carbon aerosol in the North China Plain: implications for radiative effect

2020 ◽  
Vol 20 (23) ◽  
pp. 15427-15442
Author(s):  
Qiyuan Wang ◽  
Li Li ◽  
Jiamao Zhou ◽  
Jianhuai Ye ◽  
Wenting Dai ◽  
...  
Keyword(s):  
Air Quality ◽  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiative Effect ◽  
Mixing State ◽  
The North ◽  
The North China Plain

Abstract. Establishment of the sources and mixing state of black carbon (BC) aerosol is essential for assessing its impact on air quality and climatic effects. A winter campaign (December 2017–January 2018) was performed in the North China Plain (NCP) to evaluate the sources, coating composition, and radiative effects of BC under the background of emission reduction. Results showed that the sources of liquid fossil fuels (i.e., traffic emissions) and solid fuels (i.e., biomass and coal burning) contributed 69 % and 31 % to the total equivalent BC (eBC) mass, respectively. These values were arrived at by using a combination of multi-wavelength optical approach with the source-based aerosol absorption Ångström exponent values. The air quality model indicated that local emissions were the dominant contributors to BC at the measurement site. However, regional emissions from NCP were a critical factor for high BC pollution. A single-particle aerosol mass spectrometer identified six classes of elemental carbon (EC)-containing particles. They included EC coated by organic carbon and sulfate (52 % of total EC-containing particles); EC coated by Na and K (24 %); EC coated by K, sulfate, and nitrate (17 %); EC associated with biomass burning (6 %); pure-EC (1 %); and others (1 %). Different BC sources exhibited distinct impacts on the EC-containing particles. A radiative transfer model showed that the amount of detected eBC can produce an atmospheric direct radiative effect of +18.0 W m−2 and a heating rate of 0.5 K d−1. This study shows that reductions of solid fuel combustion-related BC may be an effective way of mitigating regional warming in the NCP.

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.

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
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