Abstract. Recent ground networks and satellite remotesensing observations have provided useful data related to spatial and vertical distributions of mineral dust particles in the atmosphere. However, measurements of temporal variations and spatial distributions of mineral dust deposition fluxes are limited in terms of their duration, location, and processes of deposition. To ascertain temporal variations and spatial distributions of mineral dust deposition using wet and dry processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) in Japan during October 2008-December 2010 using automatic wet and dry separating samplers. Mineral dust weights in water-insoluble residue were estimated from Fe contents measured using an X-ray fluorescence analyser. Wet and dry deposition fluxes of mineral dusts were both high in spring and low in summer, showing similar seasonal variations to frequency of aeolian dust events (Kosa) in Japan. For wet deposition, highest and lowest annual dust fluxes were found at Toyama (9.6 g m −2 yr −1 ) and at Cape Hedo (1.7 g m −2 yr −1 ) as average values in 2009 and 2010. Higher wet deposition fluxes were observed at Toyama and Tottori, where frequent precipitation (> 60 % days per month) was observed during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and Cape Hedo, the highest and lowest annual dust fluxes were found respectively at Fukuoka (5.2 g m −2 yr −1 ) and at Cape Hedo (2.0 g m −2 yr −1 ) as average values in 2009 and 2010. The average ratio of wet and dry deposition fluxes was the highest at Toyama (3.3) and the lowest at Hedo (0.82), showing a larger contribution of the dry process at western sites, probably because of the distance from desert source regions and because of the effectiveness of the wet process in the dusty season.Size distributions of refractory dust particles were obtained using four-stage filtration: > 20, > 10, > 5, and > 1 µm diameter. Weight fractions of the sum of > 20 µ m and 10-20 µm (giant fraction) were higher than 50 % for most of the event samples. Irrespective of the deposition type, the giant dust fractions generally decreased with increasing distance from the source area, suggesting the selective depletion of larger giant particles during atmospheric transport. Based on temporal variations of PM c (2.5 < D < 10 µm), ground-based lidar, backward air trajectories, and vertical profiles of potential temperatures, transport processes of dust particles are discussed for events with high-deposition and low-deposition flux with high PM c . Low dry dust depositions with high PM c concentrations were observed under stronger (5 K km −1

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To ascertain the temporal and spatial distribution of mineral dust deposition by wet processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) during October 2008−January 2010 using automatic wet-dry separating samplers. Mineral dust weights in water-insoluble residue mixed with pollen were estimated from Fe contents measured using an X-ray fluorescence analyzer. Highest and lowest annual dust fluxes were found respectively at Toyama (8.7 g m −2 yr ) in 2009, although their annual levels of precipitation were almost equal (ca. 2300 mm). Wet deposition flux was high in spring and low in summer. Simultaneous wet deposition events were observed five times among the sites, but these events were limited to regional scale. Based on the spatial distribution of dust represented as a mosaic of true color images from MODIS/Terra and vertical distributions of dust concentration from lidar observations, a high wet-dust-deposition event occurring in mid-March at Toyama was attributed to a combination of high dust concentration in the atmosphere during precipitation. Higher wet dust deposition at Toyama and Tottori was ascribed to frequent precipitation during the dusty season. IntroductionAeolian dust particles derived from arid regions are an important component of atmospheric aerosols. Dust particles are reportedly important for the accumulation of deep-sea sediment (Prospero 1981) and for their effects on the earth's radiation budget (Tegen et al. 1996;Tanaka et al. 2007). In Japan, visibilityreducing dust events have been observed frequently during spring (Arao et al. 2003).Processes of dust particle removal from the atmosphere to the earth surface are divisible into wet and dry processes, respectively occurring with and without precipitation. High dust deposition flux with precipitation was reported for the North Pacific region when both rainfall and high atmospheric dust concentrations coincide (Uematsu et al. 1985). The vertical distribution of dust concentration in snow at Mt. Tateyama, central Japan was explained by temporal variation of dust concentrations in the atmosphere (Osada et al. 2004). Results of that study implied the importance of a combination between snowfall and high dust concentration in the atmosphere to form thick dirty-snow layers. Furthermore, sporadic "red snow" events have been observed occasionally in northern Japan, causing remarkably high wet dust deposition of about 15 g m −2 during a two-day event at Shishiku near Kanazawa (Tsunogai et al. 1972), which was more than twice the 10-year average of total dust deposition onto snow at Mt. Tateyama during winter−spring (Osada et al. 2007).Dust input is a critical source of dissolved iron for phytoplankton growth in some ocean regions (Jickells et al. 2005). According to their review, 30−95% of total input of Fe to the ocean is attributable to wet deposition. Recently, the importance of wet dust deposition events was also suggested for initiating early spring blooms in the nort...

Data of temporal variations and spatial distributions of mineral dust deposition fluxes are very limited in terms of duration, location, and processes of deposition. To ascertain temporal variations and spatial distributions of mineral dust deposition by wet and dry processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) in Japan during October 2008–December 2010 using automatic wet and dry separating samplers. Mineral dust weights in water-insoluble residue were estimated from Fe contents measured using an X-ray fluorescence analyzer. For wet deposition, highest and lowest annual dust fluxes were found at Toyama (9.6 g m⁻² yr⁻¹) and at Cape Hedo (1.7 g m⁻² yr⁻¹) as average values in 2009 and 2010. Higher wet deposition fluxes were observed at Toyama and Tottori, where frequent precipitation (>60% days per month) was observed during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and Cape Hedo, the highest and lowest annual dust fluxes were found respectively at Fukuoka (5.2 g m⁻² yr⁻¹) and at Cape Hedo (2.0 g m⁻² yr⁻¹) as average values in 2009 and 2010.

Although the seasonal tendency of the monthly dry deposition amount roughly resembled that of monthly days of Kosa dust events, the monthly amount of dry deposition was not proportional to monthly days of the events. Comparison of dry deposition fluxes with vertical distribution of dust particles deduced from Lidar data and coarse particle concentrations suggested that the maximum dust layer height or thickness is an important factor for controlling the dry deposition amount after long-range transport of dust particles. Size distributions of refractory dust particles were obtained using four-stage filtration: >20, >10, >5, and >1 μm diameter. Weight fractions of the sum of >20 μm and 10–20 μm (giant fraction) were higher than 50% for most of the event samples. Irrespective of the deposition type, the giant dust fractions were decreasing generally with increasing distance from the source area, suggesting the selective depletion of larger giant particles during atmospheric transport. Because giant dust particles are an important mass fraction of dust accumulation, especially in the north Pacific where is known as a high-nutrient, low-chlorophyll (HNLC) region, the transport height of giant dust particles is an important factor for studying dust budgets in the atmosphere and their role in biogeochemical cycles

To examine transportation and oxidation states of sulfur compounds from China to Japan, the SO 2 concentration in the atmosphere and the nss-SO 4 2-concentration and selenium (Se) concentration in aerosols were observed at four sites in western Japan. High SO 2 concentrations in the atmosphere and the nss-SO 4 2-concentration and Se concentration in aerosols were found when the air mass passed through the planetary boundary layer (PBL) over large cities or industrial areas in China during winter with winds from the northwest. A bibliographic survey of Se and S concentrations in aerosols over eastern Asia during 1991Asia during -2004 revealed that the average Se and S concentrations in aerosols at seven sites of urban or industrial areas in China were, respectively, 15.7 ng/m 3 and 7.4 μg/m 3 . The S concentration and Se concentration in aerosols in China were, respectively, about 3 times and 10-20 times higher than those of Korea and Japan. The Se/S ratios of aerosols in China were higher (avg. 2.5 × 10 -3 ) than that of Korea (avg. 0.6 × 10 -3 ) or Japan (avg. 0.7 × 10 -3 ). The SO 2 conversion rate was ascertained as 0.1% h -1 to 1.5% h -1 using the Se(sum)/S ratio technique, when the air mass passed over large combustion sources in China and later reached Japan. The Se/S (or its reverse) technique provides useful information to ascertain the SO 2 to SO 4 2-conversion rate.

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