The gaseous and particulate matter was collected on each filter with a filter-pack method (see Fig. 3; Murano, 1986; Shimohara and Murano, 1997).Each three stage- and one stage-filter holder was set in each global sampler equipment (Goto: Shibata Co. Ltd. and Dazaifu: Osaka Dylec Co. Ltd.). Tetrafluoroethylene filter (PTFE filter; pore size 0.45 um, 47 mm in diameter), cellulose-fiber filter impregnated with K₂CO₃ aqueous solution and quartz-fiber filter impregnated with H₃PO₄ aqueous solution were placed sequentially in the three-stage filter holder in an air inlet. Polyamide filter (pore size 0.4µm, 47 mm in diameter) was placed in the one-stage filter holder. At Dazaifu-city, PTFE filter, polyamide filter, cellulose-fiber filter impregnated with K₂CO₃ aqueous solution and quartz-fiber filter impregnated with H₃PO₄ aqueous solution were placed sequentially in the four-stage filter holder. Sampling at Goto Island and Dazaifu-city was conducted for 6- and 12-h period, respectively, at a flow rate of 15 l/min.Each sampling term at two sites was from 0900 JST to 1500 JST, from 1500 JST to 2100 JST, from 2100 JST to 0300 JST the next day and from 0300 JST to 0900 JST. After sampling and extraction (Murano, 1986; Shimohara and Murano, 1997), water-soluble cations and anions of the particulate matter except for NH₄⁺ extracted from the filters, were quantified by ion chromatography (Dionex Co. Ltd., DX-AQ).

The quantification of gaseous HNO₃using the three- and one-stage filter holders was made as follows. The concentrations of gaseous HNO₃ are able to calculate from the difference of concentrations of NO₃^- contained in both the PTFE and polyamide filters, because NO₃^- in the atmosphere is captured on the PTFE filter, and both NO₃^- and gaseous HNO₃ are captured on the polyamide filter. There is no need to calculate for gaseous HNO₃ on the four-stage filter holder, because polyamide filter is placed after the PTFE filter. NH₄⁺ captured on the PTFE and the quartz-fiber filters were determined by the colorimetric method. NH₄⁺ in the extraction of the quartz-fiber filter impregnated with H₃PO₄ aqueous solution was calculated to be NH₃. Sulfur dioxide is quantified by the extractions of the cellulose-fiber filter impregnated with K₂CO₃ aqueous solution.

A nitrocellulose filter, 47 mm in diameter, was put on a glass plate (50*50*4 mm). The filter was slightly dissolved and was stuck on the glass plate by exposure to acetone vapor for 30 min. The filter was then strengthened by adding a thin film of vacuum-evaporated carbon. This pre-treated film was cut into pieces of about 3*3 mm with a scalpel. A flat polyurethane sponge was dipped about a half in depth in an acetone solution in a glass vessel. Then, 200-mesh grids of 3-mm in diameter for transmission electron microscope were placed on the sponge. The pieces of film were promptly laid on each grid. The thin film on the grid was then exposed to acetone vapor for 1-h.Since only the nitrocellulose was dissolved by the acetone vapor, the carbon thin film remained on the grid (hereafter referred to as "carbon film") (Shimohara and Murano, 1997).After drying the carbon films, metal calcium (6 mg) was vapor-deposited onto some carbon films under vacuum. The calcium thin film was covered on the carbon film (hereafter referred to as "calcium film").

Figure 6 showsa reaction scheme of particles collected onto the thin films and reagents. After capturing the particles onto carbon film, the carbon film was covered with nitron and sodium tetraphenylborate vapor-deposited. Therefore, particles and reagents are slightly dissolved with each other under the atmosphere of n-octyl alcohol vapor, and form coagulated compounds. For example, nitron reagent reacts with NO₃^- corrected onto the carbon film. Needle-like and/or roundly coagulated insoluble compounds are caused on the film. Sodium tetraphenylborate reagent reacts with NH₄⁺ corrected onto the carbon film, and an observable homocentric spots consisted an ultra-minute coagulation are caused on the film (Mamane and Pena, 1978; Mamane and Pueschel, 1980).In the case of collection of NH₄NO₃ onto the film, the needle and/or roundly coagulated insoluble compounds are appeared within the homocentric spots. The particulate NaNO₃ and/or Ca(NO₃)₂ without NH₄⁺ cause only the needle and/or roundly coagulated insoluble compounds on Nt-Tet film. Ammonium sulfate, NH₄HSO₄ and NH₄Cl without NO₃^- caused only the homocentric spots on Nt-Tet film. Therefore, the characteristic spots caused by the collection of NH₄NO₃ can be differentiated from the other NO₃^- such as NaNO₃ and/or Ca(NO₃)₂ etc. (Ayers, 1978; Mamane et al., 1980; Bigg et al. 1974).

Tables 1, 2 and 3 show the average concentrations of gases and particulate matter at two sampling sites in the periods of January 1997, December 1997 and February 1999.Figures 8(1), 8(2), 9(1), 9(2), 10(1) and 10(2) show the variations of gaseous and particulate matter through out the periods. Figure 11 shows the variations of nss-SO₄^2- concentrations at Goto Island and Dazaifu-city in the period of January 1997.The variation of nss-SO₄^2- concentrations at Goto Island was well corresponded to at Dazaifu-city. Figure 12 shows the mean nano-equivalent concentrations of each component at two sampling sites in the period of January 1997. Presence of free nss-SO₄^2- without combined NH₄⁺ is confirmed.

Tables 4- 6 show the size distribution of each component of particulate matter at Goto sampling site and Tables 7-9 show the size distribution at Dazaifu sampling site in the periods of January 1997, December 1997 and February 1999, respectively. Figures 13-18 show the size distributions of individual ion components in particulate matter, observation at Goto Island and Dazaifu-city. Acidic components were found in fine size mode (below 2.1um) in both sites.

Figures 19-21 show the size distribution of H⁺ in the particulate matter at two sampling site. Figures 22-24 show the transmission electron microphotographs of three types of Nt-Tet, calcium and AgNO₃ films. The microphotographs show the sampling results performed at 1500 JST on 13 January 1997 at two sampling sites. The needle-like particles (see Fig. 22) formed by the reaction between NO₃^- particles and nitron reagent were observed around the rounded particles at two sampling sites. In contrast, a number of mixing spots with homocentric spots involving the needle-like insoluble compounds were observed only at Dazaifu-city. Homocentric spots are the results of reaction between NH₄⁺ and sodium tetraphenylborate reagent.It was concluded that the NO₃^- at Goto Island hardly contains NH₄⁺, and NO₃^- at Dazaifu-city was combined with NH₄⁺, and present as NH₄NO₃.

The non-perfect homocentric spots on thin calcium film were observed at Goto Island as a result of the reaction between the moisture of hygroscopic particles and calcium reagent (see Fig. 23).The spots caused on calcium film reflect the presence of highly hygroscopic particles in the atmosphere. The spots observed on the film sampled at Goto Island were not homocentric form but infinite form. On the other hand, there was no spot at all at Dazaifu-city.

The characteristic spots of AgCl component formed by the reaction between nss-Cl^- and AgNO₃ were observed at Dazaifu-city (see Fig. 24). Although such a spot was present in Dazaifu-city sample, it was not observed at all at Goto Island.