Evidence for hygroscopic mineral dust particles from the Intercontinental Transport and Chemical Transformation Experiment

Abstract

[1] Two collocated, eight-stage rotating drum impactors were deployed at Trinidad Head (California) during the spring of 2002 as part of the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) experiment. One of the samplers operated at ambient relative humidity while the other was operated at a relative humidity of 55%. The impaction substrates from these samplers were analyzed using synchrotron X-ray fluorescence (SXRF) to provide continuous measurements of the size-resolved aerosol elemental composition with 3-hour time resolution. The aerosol elemental composition data identified three significant mineral dust episodes near the beginning of the time series. The backward air mass trajectory calculations from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and the PM 10 to PM 2.5 elemental mass ratios are consistent with the long-range transport of mineral dust from Asian sources. The data from the paired ambient relative humidity and low-relative-humidity samplers show that the aluminum, silicon, and iron elemental mass distributions are a function of relative humidity. In each case, the elemental mass distributions shifted toward smaller sizes as the relative humidity was reduced. This behavior indicates that the mineral dust transported from Asia to the west coast of the United States is somewhat hygroscopic upon its arrival. The hygroscopic nature of the aged mineral dust should increase its ability to nucleate cloud droplets (i.e., act as cloud condensation nuclei). Measurements of transported Asian mineral dust made at a high-elevation mountain site in Oregon (i.e., Crater Lake National Park) during the spring of 2002 show a strong correlation between the silicon and sulfur elemental mass concentrations. The ratio of calcium to sulfur makes it unlikely that this coarse sulfur is derived from gypsum (i.e., CaSO 4 ). Instead, it indicates that the coarse mineral dust most likely accumulates sulfate coatings either near the source region or during transport across the Pacific Ocean.

A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network

“…Slope, intercept and correlation coefficient values of the linear fits can be found in Table 4. been shown to increase particle hygroscopicity (Perry et al, 2004;Furutani et al, 2008). Chilbolton, being a continental background site representative of the regional aerosol properties, also belongs to this group; however, the N CCN concentrations at this location may be underestimated due to the aerosol not being dried prior to entering the CCNC (Whitehead et al, 2014).…”

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

“…Hand and Malm (2006) indicated that the scattering coefficients of (NH 4 ) 2 SO 4 and (NH 4 )HSO 4 aerosols could be enhanced by a factor of three when relative humidity is over 85%. Dust particles, dominant in coarse mode, are mostly insoluble with f (RH=80%) smaller than 1.1 (Li-Jones et al, 1998), but they could also be hygroscopic when coated by sulfate or other soluble inorganic aerosols during transportation (Perry et al, 2004;Shi et al, 2007). During the period of Aerosol Characterization Experiment (ACE-Asia), dust particle's hygroscopic factor of f (RH=80%)=1.25 was observed in Ron Brown cruise (Carrico et al, 2003), and even as high as 2.0 in Korea (Kim et al, 2006).…”

The impact of dust on sulfate aerosol, CN and CCN during an East Asian dust storm

“…Observations show that secondary aerosol species such as sulfate and nitrate often exist as surface coatings on Asian dust as a result of these processes (Mori et al, 2003;Ooki and Uematsu, 2005;Perry et al, 2004;Tang et al, 2004a, b;Trochkine et al, 2003;Xiao et al, 1997;Zhang et al, 2000;Sullivan et al, 2007;Matsuki et al, 2005a, b). The presence of this material can enhance the solubility of dust particles, increasing their ability to act as cloud drop or ice immersion nuclei (Perry et al, 2004), and can increase the bioavailability of iron, which enhances the fertilisation of marine phytoplankton (Jickells et al, 2005;Meskhidze et al, 2003Meskhidze et al, , 2005. A further consequence of the uptake of secondary aerosol material, considered in this study, is that existing aerosol could be affected by dust via reduced concentrations of aerosol precursor gases, thereby influencing existing particle concentrations and even cloud condensation nuclei by reduced growth and new particle formation.…”