Size Changes of Asian Dust Particles with Respect to Their Sea Salt and Sulfate Contents

Daizhou Zhang,Yasunobu Iwasaka 한국기상학회 2006 한국기상학회 학술대회 논문집 Vol.2006 No.-

Wet Deposition Fluxes of Ions Contributed by Cyclone-, Stationary Front- and Typhoon-associated Rains at the Southwestern Japan Coast

Satoshi Toyonaga,Daizhou Zhang 한국대기환경학회 2016 Asian Journal of Atmospheric Environment (AJAE) Vol.10 No.2

Wet deposition fluxes of ions at a coastal site in southwestern Japan in the period 1996-2003 were investigated to quantify the respective contributions of cyclone-, stationary front- and typhoon-associated rains. On average, the deposition fluxes of terrigenous- origin ions, nss-SO4 2-, NO3 -, NH4 + and nss-Ca2+ were 37.6±7.3, 16.3±4.2, 19.0±3.4 and 9.6±4.8 meq m-2 yr-1, and those of Na+ and Cl-, the major ions in sea water, were 97.0±38.2 and 115.2±48.2 meq m-2 yr-1, respectively. Cyclone-associated rain constituted more than 50% of the fluxes of the terrigenous ions in almost all years. Stationary frontassociated rain also contributed significantly, although the contribution was lower than the contribution by Cyclone-associated rain in almost all years. In particular, the wet deposition flux of nitrogen compounds of NO3 - and NH4 +, which are important nutrients for micro-bioactivities in sea surface water, was dominated by cyclone-associated rain. Due to the extreme abundance of Na+ and Cl- in the rainwater of typhoons, the fluxes of Na+ and Cl- were contributed substantially by typhoons in years with typhoons’ passage although cyclones were still the largest contributor to the fluxes. These results indicate the dominance of cyclones in the wet deposition to the East China Sea areas and the necessity to take rain types into account for a more accurate elucidation of the temporal and spatial variation of the wet deposition.

Thermal and Hygroscopic Properties of Indoor Particulate Matter Collected on an Underground Subway Platform

마창진,이경빈,Daizhou Zhang,Mariko Yamamoto,김신도 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.3

In order to clarify the thermal and hygroscopic properties of indoor particulate matter (PM) in a semiclosed subway space, which is critically important for understanding of the distinctive particle formation processes as well as the assessment of their health effects, the size-resolved PMs (i.e., PM2.5 and PM10-2.5) were intensively collected on the platform of Miasageori station on the Seoul Subway Line-4. The elemental concentrations in soluble and insoluble fractions were determined by PIXE from the bulkily pretreated PM2.5. The thermal and hygroscopic characteristics of individual particles were investigated via a combination of the unique pretreatment techniques (i.e., the high-temperature rapid thermal process and the water dialysis) and SEM-EDX analysis. Iron and calcium were unequaled in insoluble and soluble PM2.5 fractions, respectively, with overwhelming concentration. The SEM-EDX’s elemental net-counts for the pre- and post-pyrolyzed PMs newly suggest that magnesium and several elements (i.e., silica, aluminum, and calcium) may be readily involved in the newly generated subway fine PM by a high-temperature thermal processing when trains are breaking and starting. Through the water dialysis technique, it turned out that calcium has meaningful amount of water soluble fraction. Furthermore, the concentrations of the counter-ions associated with the calcium in subway PM10-2.5 were theoretically estimated.

Monthly Characteristics of Rainwater Chemistry at a Coastal Site in Southwestern Japan

Toyonaga, Satoshi,Zhang, Daizhou Korean Society for Atmospheric Environment 2017 Asian Journal of Atmospheric Environment (AJAE) Vol.10 No.2

Monthly characteristics of rainwater chemistry at a coastal site in southwestern Japan were examined based on an eight year record. In the period November-May when rain was mainly caused by cyclones, the monthly mean concentrations of $nss-{SO_4}^{2-}$, ${NO_3}^-$, ${NH_4}^+$, $nss-Ca^{2+}$, $Na^+$ and $Cl^-$ over the eight years were 25.1-57.8, 9.9-25.0, 11.3-31.4, 5.5-18.7, 24.2-154.9 and $30.0-178.5{\mu}eq\;L^{-1}$, respectively. In June and July when rain was mainly caused by stationary fronts, i.e. Meiyu fronts, the concentrations were 14.4-20.7, 7.2-9.5, 7.7-12.9, 4.1-6.8, 21.7-33.6 and $26.4-40.5{\mu}eq\;L^{-1}$, respectively. In August and September when typhoons contributed substantial rainfall, the respective concentrations of $Na^+$ and $Cl^-$ were as high as 97.7-105.3 and $116.8-122.9{\mu}eq\;L^{-1}$, while the concentrations of other ions were low. These results indicate a large variation of monthly rainwater chemistry, which is basically dependent on the synoptic weather patterns causing rain. From later autumn to early spring, rain contains ions in high concentration and large variation ranges. In the Meiyu season, rain contains less ions which vary in a range much smaller than that in later autumnearly spring. In summer and autumn, the concentrations are low, except $Na^+$ and $Cl^-$ which can be large due to typhoons' contribution.

A Detection of Airborne Particles Carrying Viable Bacteria in an Urban Atmosphere of Japan

Kazutaka Hara,Daizhou Zhang,Maromu Yamada,Hiromi Matsusaki,Koji Arizono 한국대기환경학회 2011 Asian Journal of Atmospheric Environment (AJAE) Vol.5 No.3

Viable bacteria on water-insoluble airborne particles were detected in the urban atmosphere of Kumamoto (134^ㅇ45′E, 32^ㅇ28′N), Japan, in autumn 2008. Airborne particles were collected onto film-covered Cu meshes under clear weather conditions. The samples were stained by fluorescent stains, and then viewed and photographed with an epifluorescent microscope. Non-biological and bacterial parts in particles larger than 0.8 μm were distinguished by their morphologies,fluorescent colors and fluorescent intensities. Bacterial viable statuses were discriminated according to cell membrane damage. In total, 2681 particles were investigated and it was found that 78 airborne particles were associated with bacteria. Viable bacteria were identified on 48 particles. A few particles carried multiple viable bacteria. These results provide the evidence that airborne particles act as carriers of viable bacteria in the atmosphere.

Wet Deposition Fluxes of Ions Contributed by Cyclone-, Stationary Front- and Typhoon-associated Rains at the Southwestern Japan Coast

Toyonaga, Satoshi,Zhang, Daizhou Korean Society for Atmospheric Environment 2016 Asian Journal of Atmospheric Environment (AJAE) Vol.10 No.2

Wet deposition fluxes of ions at a coastal site in southwestern Japan in the period 1996-2003 were investigated to quantify the respective contributions of cyclone-, stationary front- and typhoon-associated rains. On average, the deposition fluxes of terrigenous-origin ions, nss-$SO_4{^{2-}}$, $NO_3{^-}$, $NH_4{^+}$ and nss-$Ca^{2+}$ were $37.6{\pm}7.3$, $16.3{\pm}4.2$, $19.0{\pm}3.4$ and $9.6{\pm}4.8meq\;m^{-2}yr^{-1}$, and those of $Na^+$ and $Cl^-$, the major ions in sea water, were $97.0{\pm}38.2$ and $115.2{\pm}48.2meq\;m^{-2}yr^{-1}$, respectively. Cyclone-associated rain constituted more than 50% of the fluxes of the terrigenous ions in almost all years. Stationary front-associated rain also contributed significantly, although the contribution was lower than the contribution by Cyclone-associated rain in almost all years. In particular, the wet deposition flux of nitrogen compounds of $NO_3{^-}$ and $NH_4{^+}$, which are important nutrients for micro-bioactivities in sea surface water, was dominated by cyclone-associated rain. Due to the extreme abundance of $Na^+$ and $Cl^-$ in the rainwater of typhoons, the fluxes of $Na^+$ and $Cl^-$ were contributed substantially by typhoons in years with typhoons' passage although cyclones were still the largest contributor to the fluxes. These results indicate the dominance of cyclones in the wet deposition to the East China Sea areas and the necessity to take rain types into account for a more accurate elucidation of the temporal and spatial variation of the wet deposition.

A Detection of Airborne Particles Carrying Viable Bacteria in an Urban Atmosphere of Japan

Hara, Kazutaka,Zhang, Daizhou,Yamada, Maromu,Matsusaki, Hiromi,Arizono, Koji Korean Society for Atmospheric Environment 2011 Asian Journal of Atmospheric Environment (AJAE) Vol.5 No.3

Viable bacteria on water-insoluble airborne particles were detected in the urban atmosphere of Kumamoto ($134^{\circ}45'E$, $32^{\circ}28'N$), Japan, in autumn 2008. Airborne particles were collected onto film-covered Cu meshes under clear weather conditions. The samples were stained by fluorescent stains, and then viewed and photographed with an epifluorescent microscope. Non-biological and bacterial parts in particles larger than 0.8 ${\mu}m$ were distinguished by their morphologies, fluorescent colors and fluorescent intensities. Bacterial viable statuses were discriminated according to cell membrane damage. In total, 2681 particles were investigated and it was found that 78 airborne particles were associated with bacteria. Viable bacteria were identified on 48 particles. A few particles carried multiple viable bacteria. These results provide the evidence that airborne particles act as carriers of viable bacteria in the atmosphere.

Monthly Characteristics of Rainwater Chemistry at a Coastal Site in Southwestern Japan

Satoshi Toyonaga,Daizhou Zhang 한국대기환경학회 2017 Asian Journal of Atmospheric Environment (AJAE) Vol.11 No.2

Monthly characteristics of rainwater chemistry at a coastal site in southwestern Japan were examined based on an eight year record. In the period November- May when rain was mainly caused by cyclones, the monthly mean concentrations of nss-SO4 2-, NO3 -, NH4 +, nss-Ca2+, Na+ and Cl- over the eight years were 25.1-57.8, 9.9-25.0, 11.3-31.4, 5.5-18.7, 24.2-154.9 and 30.0-178.5 μeq L-1, respectively. In June and July when rain was mainly caused by stationary fronts, i.e. Meiyu fronts, the concentrations were 14.4-20.7, 7.2-9.5, 7.7-12.9, 4.1-6.8, 21.7- 33.6 and 26.4-40.5 μeq L-1, respectively. In August and September when typhoons contributed substantial rainfall, the respective concentrations of Na+ and Cl- were as high as 97.7-105.3 and 116.8-122.9 μeq L-1, while the concentrations of other ions were low. These results indicate a large variation of monthly rainwater chemistry, which is basically dependent on the synoptic weather patterns causing rain. From later autumn to early spring, rain contains ions in high concentration and large variation ranges. In the Meiyu season, rain contains less ions which vary in a range much smaller than that in later autumnearly spring. In summer and autumn, the concentrations are low, except Na+ and Cl- which can be large due to typhoons’ contribution.

Episodic Particulate Sulfate and Sulfur Dioxide on the Southwestern Japan Coast in March and April 2010

Tetsuji Nagatani,Maromu Yamada,Tomoko Kojima,Daizhou Zhang 한국대기환경학회 2012 Asian Journal of Atmospheric Environment (AJAE) Vol.6 No.1

Particulate sulfate in PM2.5, sulfur dioxide (SO2) and size-segregated aerosol particle number concentrations were measured at a site (32° 9′N, 129° 59′E) on the southwestern Japan coast from 5 March to 10April, 2010. Results show frequent episodic increases of sulfate and SO2. Compared to the average concentration of sulfate 4.4±2.7 μg m-3 in the whole observation period, episodic sulfate reached 10.5-20.1 μg m-3. The variation of sulfate always synchronized with aerosol particles in the size range of 0.1-0.5 μm,indicating the episodic sulfate was a consequence of the increase of the sub-micron particles. SO2 did not have remarkable increase in any episodes of sulfate increase. During the passage of low pressure systems which loaded Asian dust in postfrontal air, concentrated sulfate appeared right behind the front but before dust arrival, suggesting the dominance of dustfree particulate sulfate. Weather and backward trajectory analyses revealed that air parcels with high sulfate passed eastern and northeastern China or Korean peninsula before arriving at the site. In contrast,those with high SO2 passed an active volcano,Mt. Sakurajima, about 100 km in the south, suggesting the SO2 was more likely from the volcanic emission. The ratio of sulfate to total sulfur compounds (SO42-)/(SO42-+SO2) was 0.31-0.89 in continentally originated air while was 0.25-0.43 in the air having passed the volcano, showing more efficient conversions of SO2 to sulfate in the air from the continent. The close dependence of the conversion on humidity in the continentally originated air was confirmed. Particulate sulfate in PM2.5, sulfur dioxide (SO2) and size-segregated aerosol particle number concentrations were measured at a site (32° 9′N, 129° 59′E) on the southwestern Japan coast from 5 March to 10April, 2010. Results show frequent episodic increases of sulfate and SO2. Compared to the average concentration of sulfate 4.4±2.7 μg m-3 in the whole observation period, episodic sulfate reached 10.5-20.1 μg m-3. The variation of sulfate always synchronized with aerosol particles in the size range of 0.1-0.5 μm,indicating the episodic sulfate was a consequence of the increase of the sub-micron particles. SO2 did not have remarkable increase in any episodes of sulfate increase. During the passage of low pressure systems which loaded Asian dust in postfrontal air, concentrated sulfate appeared right behind the front but before dust arrival, suggesting the dominance of dustfree particulate sulfate. Weather and backward trajectory analyses revealed that air parcels with high sulfate passed eastern and northeastern China or Korean peninsula before arriving at the site. In contrast,those with high SO2 passed an active volcano,Mt. Sakurajima, about 100 km in the south, suggesting the SO2 was more likely from the volcanic emission. The ratio of sulfate to total sulfur compounds (SO42-)/(SO42-+SO2) was 0.31-0.89 in continentally originated air while was 0.25-0.43 in the air having passed the volcano, showing more efficient conversions of SO2 to sulfate in the air from the continent. The close dependence of the conversion on humidity in the continentally originated air was confirmed.