Size-resolved surface active substances of atmospheric aerosol: reconsideration of the impact on cloud droplet formation

Kroflič, Ana; Frka, Sanja; Martin, Simmel; Heike, Wex; Irena, Grgić (2018) Size-resolved surface active substances of atmospheric aerosol: reconsideration of the impact on cloud droplet formation. Environmental Science and Technology, 52 (16). pp. 9179-9187. ISSN 0013-936X

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Abstract

Our current understanding of the importance of surface-active substances (SAS) on atmospheric aerosol cloud-forming efficiency is limited, as explicit data on the content of size-resolved ambient aerosol SAS, which are responsible for lowering the surface tension (σ) of activating droplets, are not available. We report on the first data comprising seasonal variability of size-segregated SAS concentrations in ambient aerosol particulate matter (PM). To assess the impact of SAS distribution within PM on cloud droplet activation and growth, a concept of surfactant activity was adopted and a parametrization developed ; i.e., surfactant activity factor (SAF) was defined, which allowed translation of experimental data for use in cloud parcel modeling. The results show that SAS-induced σ depression during cloud activation may affect droplet number ( Nd) as much as a 2-fold increase in particle number, whereas by considering also the size distribution of particulate SAS, Nd may increase for another 10%. This study underscores the importance of size-resolved SAS perspective on cloud activation, as data typically obtained from aqueous extracts of PM2.5 and PM10 may result in misleading conclusions about droplet growth due to large mass fractions of supermicron particles with SAS deficit and little or no influence on CCN and Nd.

Item Type:	Article
Additional Information:	We thank the Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia (UL FCCT), for permission to install the Berner impactor in the faculty area. We acknowledge Dr. Bojan Sarac from UL FCCT for access to the tensiometer and Dr. Janja Tursic from the Environment Agency of the Republic of Slovenia, Ljubljana, for providing PM<INF>10</INF> samples and performing WSOC analyses. We gratefully acknowledge Dr. Hartmut Herrmann from TROPOS for enabling this international collaboration and Dr. Frank Stratmann from TROPOS for a fruitful discussion. We acknowledge financial support from the European Union Seventh Framework Programme (FP7 2007-2013), Marie Curie FP7-PEOPLE-2011-COFUND (GA No. 291823) through the NEWFELPRO project (Contract No. 47), and the Slovenian Research Agency (Research Core Funding No. P1-0034).
Uncontrolled Keywords:	Surfactants ; Atmospheric aerosols ; CNN ; Size-segregated ; Electrochemistry
Subjects:	NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Analytic Chemistry NATURAL SCIENCES > Interdisciplinary Natural Sciences > Environmental Science NATURAL SCIENCES > Interdisciplinary Natural Sciences > Radiation Science
Divisions:	Division for Marine and Enviromental Research
Projects:	Project title Project leader Project code Project type Chemical nature of size segregated water soluble organic aerosols and their nitro-aromatic constituents (FP7-PEOPLE-2011-COFUND, GA 47) UNSPECIFIED UNSPECIFIED UNSPECIFIED
Depositing User:	Sanja Frka Milosavljević
Date Deposited:	03 Dec 2019 12:41
URI:	http://fulir.irb.hr/id/eprint/5120
DOI:	10.1021/acs.est.8b02381

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