Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC

Abstract

Abstract. Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 µm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1-5 µg m −3 as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 µm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and were nominally anti-correlated with the increases in the number concentrations of coarse particles. The ion chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Suspension of dust with deposited organic material and scavenging of organic materials by dust near anthropogenic sources are suggested, and if any secondary organic aerosol (SOA) was formed during transport from Asian source regions across the Pacific it was princiCorrespondence to: W. R. Leaitch (Richard.Leaitch@ec.gc.ca) pally associated with the coarse particles. An average of profiles indicates that trans-Pacific transport between 2 and 5 km during this period increased ozone by about 10 ppbv and fine particle sulphate by 0.2-0.5 µg m −3 . The mean sizes of the fine particles in the sulphate plumes were larger when dust particles were present and smaller when the fine particle organic mass concentration was larger and dust was absent. The coarse particles of dust act to accumulate sulphate, nitrate and organic material in larger particles, diminishing the role of these compounds in indirect radiative forcing, but potentially enhancing their roles in direct radiative forcing.

Evolution of aerosol chemistry in Xi'an, inland China, during the dust storm period of 2013 – Part 1: Sources, chemical forms and formation mechanisms of nitrate and sulfate

“…The Gobi desert of northern China and Mongolia and the Taklamakan desert of western China are the major source regions of East Asian dust (McNaughton et al, 2009;Mochida et al, 2007). Modeling results indicate that around 100−460 Tg yr −1 of dust is emitted annually from the East Asia source regions (Laurent et al, 2006) and transported eastwardly, exerting a significant impact on the atmosphere over the downwind regions, including eastern coastal China (Arimoto et al, 2006;Kim et al, 2004;Li et al, 2014;Li and Shao, 2009;Sun et al, 2010;, Korea (Geng et al, 2014;Song et al, 2013;Sullivian et al, 2007), Japan (Takahashi et al, 2011;Tobo et al, 2010;Uno et al, 2009) and western North America (Huebert et al, 2003;Leaitch et al, 2009;McNaughton et al, 2009;Parrington et al, 1983;Singh et al, 2009). A recent study found that dust from the Sahara and Asia is transported over the Pacific Ocean and increases the snow precipitation in mountainous areas of Nevada, USA (Creamean et al, 2013).…”

Trans-Pacific transport of reactive nitrogen and ozone to Canada during spring

“…The C-130 appears to have flown through the same plume during both its descent (magenta marker) and ascent (cyan marker). Finally, the Cessna flight on May 5 encountered an airmass with elevated ozone between 3 km and 4 km coincident with a sulphate aerosol plume (Leaitch et al, 2009).…”

“…The DC-8 and C-130 flew varied flight paths over a large domain, relying on chemical forecasts to identify potentially interesting airmasses. As described by Leaitch et al (2009), the Cessna flew regular vertical profiles over the nearby ground measurement station at Whistler Peak to facilitate the interpretation of the measurements, to provide context for the Whistler summit station, and to accomodate the shorter range of the Cessna. Singh et al (2009) describe the instrumentation on all three aircraft platforms.…”

Organic functional groups in aerosol particles from burning and non-burning forest emissions at a high-elevation mountain site

“…Measurements in the free troposphere (FT) can provide information regarding background concentrations (e.g., Nyeki et al, 1998) and detect pollutants transported over long distances (e.g., Leaitch et al, 2009), and yet multi-seasonal records of high-altitude measurements of organic aerosol composition in the FT are sparse. Researchers at one monitoring station, Jungfraujoch, located in the Swiss Alps (∼3500 m a.s.l.…”