Diurnal variations in the hygroscopic growth cycles of ambient aerosol populations

Abstract

[1] During August and September of 2002, a relative humidity (RH) scanning tandem differential mobility analyzer system was used to measure the deliquescence/ crystallization properties of ambient aerosol populations in southeast Texas. During August, sampling was conducted at a rural site on the Texas A&M campus in College Station, and in September, sampling was conducted at an urban site near the Houston ship channel. Measurements from both sites indicate that there are cyclical changes in the composition of the soluble fraction of the aerosol, which are not strongly linked to the local aerosol source. The observations show that as temperature increases and RH decreases, the hysteresis loop describing the RH dependence of aerosol hygroscopic growth collapses. On the basis of results from other studies that have shown the dominant ions present in aerosols in this region to be ammonium and sulfate, it is proposed that this collapse is due to a decrease in the ammonium to sulfate ratio in the aerosol particles, which coincides with increasing temperature and decreasing RH. This cyclical change in aerosol acidity may influence secondary organic aerosol production and may exaggerate the impact of the aerosol on human health. The compositional changes also result in a daily cycle in crystallization RH that is in phase with that of the ambient RH, which reduces the probability that hygroscopic particles will crystallize in the afternoon when the ambient RH is a minimum.

Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth

“…For example, the abrupt phase transitions of inorganic salts sometimes observed in the atmosphere (e.g., Santarpia et al, 2005) clearly cannot be described by this smooth function (nor by the γ parameterization). More complex, multi-parameter descriptions of aerosol deliquescence and efflorescence (e.g., Kotchenruther et al, 1999;Mikhailov et al, 2013;Zieger et al, 2011) are underconstrained by our three-point f (RH) deliquescence measurement.…”

“…In general, particles composed primarily of organic material and dust are less hygroscopic Petters and Kreidenweis, 2007;Zieger et al, 2015), while those that are predominantly inorganic take up water more readily (e.g., Petters and Kreidenweis, 2007;Quinn et al, 2005). Particles may exhibit sharp phase transitions as they deliquesce, as well as hysteresis as they effloresce, especially for inorganic compositions (e.g., Santarpia et al, 2005;Tang, 1996;Zieger et al, 2014). Particles dominated by organic compounds are more likely to present more gradual hygroscopic growth with increasing RH without evident phase transition behavior (e.g., Carrico et al, 2005;Zieger et al, 2015).…”

“…This analysis focuses on midday and afternoon data collected when the planetary boundary layer was fully developed because, (1) prior to daytime atmospheric mixing, aerosols may be chemically diverse and externally mixed, leading to complex hygroscopic growth patterns that are hard to characterize (Santarpia et al, 2005); (2) we wish to develop an understanding of aerosol hygroscopicity that is regionally representative, and the well-developed, cloudtopped boundary layer structure examined here is typical of the southeastern US in summertime (Warren et al, 1986); and (3) most of the airborne data were taken in the late morning and afternoon in fair weather. We describe the observed variability in aerosol composition, size distribution, and hygroscopicity characteristics in this environment and evaluate the suitability of κ-Köhler and Mie theories to represent f (RH).…”

Relative Humidity-Dependent HTDMA Measurements of Ambient Aerosols at the HKUST Supersite in Hong Kong, China

“…Unfortunately, most of the previous field studies were conducted under a fixed RH condition. There is a lack of complete growth/evaporation measurements to fully characterize the hysteresis behavior of ambient aerosols (Santarpia et al 2005). A description of GF in an RH cycle with chemical parameters would also help improve the accuracy of model predictions.…”

Observational study of influence of aerosol hygroscopic growth on scattering coefficient over rural area near Beijing mega-city

“…Another methodology, taking advantage of H-TDMA (Hygroscopicity-Tandem Differential Mobility Analyzer) to measure alteration of aerosol size distribution after particle hygroscopic growth has been detailed described in many studies (Chen et al, 2003;Carrico et al, 2005;Santarpia et al, 2005;Herich et al, 2008). Diameter hygroscopic growth, (referred as GF D ) was investigated for diverse aerosol types, including urban pollutant (Chen et al, 2003;Ferron et al, 2005;Gysel et al, 2007), rural (Ferron et al, 2005;Aklilu et al, 2006), Biogenically dominated (Rissler et al, 2004) and Remote Marine aerosols (Berg et al, 1998;Zhou et al, 2001) as well as "pure" substances such as laboratory generated inorganics (Gysel et al, 2002), fresh mineral dust (Vlasenko et al, 2005), biomass burning exhausts (Pagels et al, 2003), humic-like substances (Dinar et al, 2007) and organic acids (Wise et al, 2003), etc.…”