Long‐range transport of SO_x and dust in East Asia during the PEM B Experiment

Abstract

Abstract. The transport of SO2 and surfate in East Asia (including eastern China, Korea, and Japan) during the period of March 1 through March 14, 1994, is studied using a three-dimensional regional-scale atmospheric chemistry model. This period corresponds to that in which the Pacific Exploratory Mission in the Western Pacific Ocean (PEM-West B) was being conducted around Japan. During this period, characterized by the passage of cold fronts and relatively dry conditions, the anthropogenic sulfur emitted from the source regions in East Asia is transported out into the central Pacific Ocean. The sulfur transport is largely limited to the lower 4 km of the atmosphere, with the maximum flux occurring in the 30 ø to 40øN latitude band containing the bulk of the anthropogenic emissions. The interactions between the sulfur cycle and mineral aerosol are also included in the analysis. It is found that the chemical conversion of SO2 to sulfate in the presence of mineral aerosol may be a significant process during this time period, and may contribute from 20% to 40% of the total sulfate production. Sulfur dioxide arising from volcanic sources in Japan is also discussed.

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

“…However, the total sulfate inside the dust cloud increased by less than 2% because decreases in fine sulfate essentially compensated increases in coarse sulfate. Previous model studies have suggested that dust could increase the local sulfate mass burden by 10-100% downwind of E. Asia (Bauer and Koch, 2005;Dentener et al, 1996;Song and Carmichael, 2001;Xiao et al, 1997). These studies also predicted that up to 70% of sulfate was present at coarse sizes over the Yellow Sea and Sea of Japan, at dust concentrations over an order of magnitude lower than observed in ACE-Asia.…”

“…Approximately 10-30% of the sulfate mass was observed at super-micron sizes in flights 6, 7 and 8 of the ACE-Asia experiment. Most of the ACEAsia observations were made at dust concentrations of 100-1000 µg m −3 , which are a factor 10-100 greater than simulated by Dentener et al (1996), Xiao et al (1997) and Song and Carmichael (2001). These studies did not consider surface saturation effects when modeling heterogeneous reactions between SO 2 and dust, which allowed SO 2 to be continually oxidized to sulfate on the dust surface.…”

“…Dentener et al (1996) estimated that the presence of dust increased sulfate mass concentrations by 10-20% across the Yellow Sea and Sea of Japan. Xiao et al (1997) predicted that dust caused an increase in the sulfate mass concentration of over 40% in the PEM West B campaign, leading to a coarse sulfate fraction of 70% across the east coast of China. Song and Carmichael (2001) performed a similar study to Xiao et al (1997) and simulated a 40% increase in sulfate, and a coarse sulfate fraction of 30-60% in a dust plume over the Yellow Sea.…”

“…Xiao et al (1997) predicted that dust caused an increase in the sulfate mass concentration of over 40% in the PEM West B campaign, leading to a coarse sulfate fraction of 70% across the east coast of China. Song and Carmichael (2001) performed a similar study to Xiao et al (1997) and simulated a 40% increase in sulfate, and a coarse sulfate fraction of 30-60% in a dust plume over the Yellow Sea. Approximately 10-30% of the sulfate mass was observed at super-micron sizes in flights 6, 7 and 8 of the ACE-Asia experiment.…”

“…During transport, the dust can become internally mixed with other chemical species through condensation, coagulation, surface chemical reactions, and aqueous phase chemical reactions in cloud drops containing dust (cloud processing). 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.…”