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2640746 
Journal Article 
Simultaneous HTDMA and HR-ToF-AMS measurements at the HKUST Supersite in Hong Kong in 2011 
Yeung, MC; Lee, BP; Li, YJie; Chan, CK 
2014 
Yes 
Journal of Geophysical Research: Atmospheres
ISSN: 2169-897X
EISSN: 2169-8996 
119 
16 
9864-9883 
WOS:000341994000017 
This paper presents the results of simultaneous aerosol hygroscopicity and composition measurements using a Humidified Tandem Differential Mobility Analyzer (HTDMA) and an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) at the HKUST Supersite, located at a coastal suburban site in Hong Kong. Growth factors (GFs) at 90% relative humidity and the size-resolved composition of ambient aerosols at dry electrical mobility diameters of 75, 100, 150, and 200 nm were measured in May, September, and November 2011. Bimodal GF distributions with a dominant more hygroscopic (MH) mode and a small fraction of the nonhygroscopic or less hygroscopic mode (number fraction < 0.2) were observed throughout the study. The average MH mode GF (1.44-1.52) over the second half of September was significantly lower than that in other periods (1.53-1.64) due to the high organic loading under the influence of the continental airstream. The average ensemble mean growth factor (GF*) of maritime aerosols was higher (1.53-1.59) than that of continental aerosols (1.45-1.48). Closure between the aerosol hygroscopicity and chemical composition was also evaluated. Over 90% of measured data and predictions based on Extended Aerosol Inorganics Model with a constant GF of the organic fraction (GF(org)) of 1.18 are within 10% closure. Approximations for GF(org) using the fraction of m/z 44 in organic mass spectra, the oxygen-to-carbon atomic ratio, and PMF-resolved organic factors from HR-ToF-AMS measurements did not yield better closure results, likely because of the overall dominance of sulfate over the whole study period. Finally, GF(org) of 1 to 1.5 (with kappa(org) up to 0.29) was found to best fit the additional water content unexplained by the inorganic species.