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CCN closure study: Effects of aerosol chemical composition and mixing state

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TLDR
In this article, the effects of chemical composition (bulk and size resolved) and mixing state (internal and external) on CCN activity of aerosols were investigated during the winter season in Kanpur.
Abstract
This study presents a detailed cloud condensation nuclei (CCN) closure study that investigates the effects of chemical composition (bulk and size resolved) and mixing state (internal and external) on CCN activity of aerosols. Measurements of the chemical composition, aerosol size distribution, total number concentration, and CCN concentration at supersaturation (SS = 0.2–1.0%) were performed during the winter season in Kanpur, India. Among the two cases considered here, better closure results are obtained for case 1 (low total aerosol loading, 49.54 ± 26.42 μg m−3, and high O:C ratio, 0.61 ± 0.07) compared to case 2 (high total aerosol loading, 101.05 ± 18.73 μg m−3, and low O:C ratio, 0.42 ± 0.06), with a maximum reduction of 3–81% in CCN overprediction for all depleted SS values (0.18–0.60%). Including the assumption that less volatile oxidized organic aerosols represent the soluble organic fraction reduced the overprediction to at most 40% and 129% in the internal and external mixing scenarios, respectively. At higher depleted SS values (0.34–0.60%), size-resolved chemical composition with an internal mixing state performed well in CCN closure among all organic solubility scenarios. However, at a lower depleted SS value (0.18%), closure is found to be more sensitive to both the chemical composition and mixing state of aerosols. At higher SS values, information on the solubility of organics and size-resolved chemical composition is required for accurate CCN predictions, whereas at lower SS values, information on the mixing state in addition to the solubility of organics and size-resolved chemical composition is required. Overall, κtotal values are observed to be independent of the O:C ratio [κtotal = (0.36 ± 0.01) × O:C − (0.03 ± 0.01)] in the range of 0.2<O:C<0.81, which indicates that the variation in the chemical composition of aerosols is not well represented by the changes in the O:C ratio alone.

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Citations
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Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

TL;DR: In this article, the mean hygroscopicity parameters (κs) of 50, 100, 150, 200, and 250 nm particles were respectively 0.16, 0.19, p.07 and 0.10, showing an increasing trend with increasing particle size.
Journal ArticleDOI

A review of aerosol chemistry in Asia: insights from aerosol mass spectrometer measurements

TL;DR: Aerosol composition varied largely in different regions, but was overall dominated by organic aerosols (OA, 32-75%), especially in south and southeast Asia due to the impact of biomass burning, and secondary OA was a ubiquitous and dominant aerosol component in all regions.
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Real-time measurements of ambient aerosols in a polluted Indian city: Sources, characteristics, and processing of organic aerosols during foggy and nonfoggy periods

TL;DR: In this article, a detailed time-resolved chemical characterization of ambient nonrefractory submicron aerosols (NR-PM1) was conducted for the first time in India.
References
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Journal ArticleDOI

First Surface Measurement of Cloud Condensation Nuclei over Kanpur, IGP: Role of Long Range Transport

TL;DR: In this paper, a large number of days in each season of the year 2008 and 2009 at Kanpur, North India were measured for cloud condensation nuclei (N CCN, number concentration at 0.38% average depleted supersaturation, SS) and submicron aerosol (N CN), using a Droplet Measurement Technology (MMT) and Scanning Mobility Particle Sizer (TSI) respectively.
Journal ArticleDOI

Inter-seasonal variability in size-resolved CCN properties at Kanpur, India

TL;DR: In this paper, the authors present properties of size-resolved cloud condensation nuclei (CCN) over the central Indo-Gangetic Basin (IGB) station, Kanpur, India.
Journal ArticleDOI

CCN closure results from Indian Continental Tropical Convergence Zone (CTCZ) aircraft experiment

TL;DR: The results of CCN closure improved significantly (overprediction improved by 37.5% and 34.6% for Pantnagar and Gaya, respectively) with the assumption of internally mixed aerosols composed of ammonium sulfate and insoluble organics as mentioned in this paper.
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