Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 544, Issue -, Pages 661-669Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2015.11.164
Keywords
Water-soluble matter; Hygroscopicity; Bay of Bengal; H-TDMA; Indo-Gangetic plain; Dicarboxylic acids
Categories
Funding
- Japan Society for the Promotion of Science (JSPS) [24221001]
- JSPS fellowship
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Hygroscopic properties of water-soluble matter (WSM) extracted from fine-mode aerosols (PM2.5) in the marine atmospheric boundary layer of the Bay of Bengal (BoB) have been investigated during a cruise from 27th December 2008 to 30th January 2009. Hygroscopic growth factors were measured on particles generated from the WSM using an H-TDMA system with an initial dry size of 100 nm in the range of 5-95% relative humidity (RH). The measured hygroscopic growth of WSM at 90% RH, g(90%)(WSM), were ranged from 1.11 to 1.74 (mean: 1.43 +/- 0.19) over the northern BoB and 1.12 to 1.38 (mean: 1.25 +/- 0.09) over the southern BoB. A key finding is that distinct hygroscopic growth factors are associated with the air masses from the Indo-Gangetic plains (IGP), which are clearly distinguishable from those associated with air masses from Southeast Asia (SEA). We found higher (lower) g(90%) WSM over the northern (southern) BoB, which were associated with an IGP (SEA) air masses, probably due the formation of high hygroscopic salts such as (NH4)(2)SO4. On the other hand, biomass burning influenced SEA air masses confer the low hygroscopic salts such as K2SO4, MgSO4, and organic salts over the southern BoB. Interestingly, mass fractions of water-soluble organic matter (WSOM) showed negative and positive correlations with g(90%) WSM over the northern and southern BoB, respectively, suggesting that the mixing state of organic and inorganic fractions could play a major role on the g(90%) WSM over the BoB. Further, WSOM/SO42- mass ratios suggest that SO42- dominates the g(90%)(WSM) over the northern BoB whereas WSOM fractions were important over the southern BoB. The present study also suggests that aging process could significantly alter the hygroscopic growth of aerosol particles over the BoB, especially over the southern BoB. (C) 2015 Elsevier B.V. All rights reserved.
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