Hygroscopic growth and CCN activity of HULIS from different environments

Abstract

.[1] Humic-like substances (HULIS) constitute a significant fraction of aerosol particles in different environments. Studies of the role of HULIS in hygroscopic growth and cloud condensation nuclei (CCN) activity of aerosol particles are scarce, and results differ significantly. In this work the hygroscopic growth and CCN activity of water extracts (WE) and HULIS extracted from particulate matter (PM) collected at a polluted urban site (Copenhagen, Denmark), a rural site (Melpitz, Germany) and the remote site Storm Peak Laboratory (Colorado, USA) were investigated. Measurements of inorganic ions, elemental carbon, organic carbon and water soluble organic carbon (WSOC) within the PM confirmed that the sources of aerosol particles most likely differed for the three samples. The hygroscopic properties of the filtered WE were characterized by hygroscopicity parameters for subsaturated conditions (k GF ) of 0.25, 0.41 and 0.22, and for supersaturated conditions k CCN were 0.23, 0.29 and 0.22 respectively for the urban, rural and remote WE samples. The measured hygroscopic growth and CCN activity were almost identical for the three HULIS samples and could be well represented by k GF = 0.07 and k CCN = 0.08-0.10 respectively. Small amounts of inorganic ions were present in the HULIS samples so the actual values for pure HULIS are expected to be slightly lower (k GF * = 0.04-0.06 and k CCN * = 0.07-0.08). The HULIS samples are thus less hygroscopic compared to most previous studies. To aid direct comparison of hygroscopic properties of HULIS from different studies, we recommend that the fraction of inorganic species in the HULIS samples always is measured and reported.Citation: Kristensen, T. B., et al. (2012), Hygroscopic growth and CCN activity of HULIS from different environments,

Temporal variations of the abundance and optical properties of water soluble Humic-Like Substances (HULIS) in PM2.5 at Guangzhou, China

“…These contributions were comparable to data (15-29%) obtained for polluted rural and urban sites (Baduel et al, 2010;Duarte et al, 2007;Salma et al, 2007Salma et al, , 2008, but were slightly smaller than the observations (30-45%) for the rural, biomass burning, and continental background aerosol samples (Kristensen et al, 2012;Lin et al, 2010b;Park et al, 2012Salma et al, 2010). These contributions of HULIS undoubtedly indicate the importance of HULIS in controlling pollution from organic aerosols.…”

Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the western North Atlantic

“…Kristensen et al (2012) reported average κ CCN values of ∼ 0.08 for large fractions of ambient water-soluble organic particulate matter in different environments. If such a κ CCN value is assumed for the organic species in the present study, then an internally mixed volume fraction of organic matter at the order of ∼ 50 % in the diameter range ∼ 50-200 nm could explain the observations, if it is assumed that the remainder of the PM in that size range is dominated by sulfate species.…”

Chemical and hygroscopic properties of aerosol organics at Storm Peak Laboratory

“…In general, there is significant variation in reported hygroscopicities of HULIS as reviewed by Kristensen et al . [].…”

“…Additionally, a parallel study of hygroscopic growth and CCN activity of HULIS from filters collected immediately after this campaign is presented in Kristensen et al . [].…”