Relative Humidity-Dependent HTDMA Measurements of Ambient Aerosols at the HKUST Supersite in Hong Kong, Chinaстатья из журнала
Аннотация: The hygroscopic tandem differential mobility analyzer (HTDMA) has been frequently used to measure the hygroscopic properties of atmospheric aerosols at a fixed high relative humidity (RH) of about 90%. To evaluate if such measurements could be used to determine the hygroscopicity of aerosols at lower RH, simultaneous hygroscopic growth factor (GF) and size-resolved composition measurements were made with an HTDMA and a high-resolution aerosol mass spectrometer (HR-AMS), respectively, at a coastal site in Hong Kong from January to June and in August 2012. A total of 58 cycles of dehydration (decreasing RH) and hydration (increasing RH) of 100 nm and 200 nm particles with organic-to-inorganic mass ratio ranging from 0.19 to 1.97 were measured at RH = 10–93%. The Kappa (κ) equation developed by Petters and Kreidenweis in the year 2007 was used to determine (i) κ at individual RHs (κRH) and (ii) best-fit κ covering the range of RHs measured (κf) for the more-hygroscopic (MH) mode, which describes more than 80% of the particles in each cycle, during dehydration. Overall, κ at 90% RH or above (κ>90) fell between 0.18 and 0.48, and was within 15% of κf in 83% of the datasets. Regression analysis between κ>90 or κf and AMS mass fractions showed that κ was positively correlated with sulfate but negatively correlated with organic and nitrate. In most cases, κRH increased as RH decreased and the average increase in κ was 45% from 90% RH to 40% RH, but these differences yielded insignificant changes in the GF-RH curves. The Zdanovskii-Stokes-Robinson (ZSR) estimated κ were mostly within 20% of κ>90 and κf. GF predictions using the empirical correlation of κ with AMS mass fractions or the ZSR estimated κ were within 10% of additional measurements and hence κ>90 is useful for predicting GF at lower RHs.Copyright 2015 American Association for Aerosol Research
Год издания: 2015
Издательство: Taylor & Francis
Источник: Aerosol Science and Technology
Ключевые слова: Atmospheric chemistry and aerosols, Air Quality and Health Impacts, Atmospheric aerosols and clouds
Открытый доступ: bronze
Том: 49
Выпуск: 8
Страницы: 643–654