Kentaro Murano

Aerosol composition at Cheju Island, Korea

The seasonal variation in chemical composition of aerosols measured at Cheju Island, Korea, is presented and discussed. Daily tape filters have been obtained for the three year period analyzed, March 1992 through February 1995. The annual average non-sea-salt sulfate and nitrate mass concentrations of aerosols measured at Cheju, are 7.2 μg/m3 and 1.2 μg/m3, respectively; while calcium and potassium are present in nearly equal amounts of ∼0.5 μg/m3, and ammonium averages 1.3 μg/m3. The annual mean mass ratios are SO42−/NO3− = 6.2, NH4+/SO42− = 0.2, Ca2+/Na+ = 0.3, and NH4+/NO3− = 1.1. Each species is found to follow a seasonal cycle, with sulfate, nitrate, ammonium, potassium, and calcium all showing higher values in the spring. In contrast, chlorine concentrations are 10% lower in the spring. Aerosol enrichment factors relative to the composition of seawater and crustal material from the dust-source regions in central China reveal that the aerosol measured at Cheju is enriched in sulfate, nitrate, and ammonium, but is deficient in chlorine (relative to seawater). The data from the daily tape filters are also compared with those from weekly Hi-Vol filters located at the same site and other measurements in the region.

Influence of continental outflow events on the aerosol composition at Cheju Island, South Korea

The chemical composition of aerosols measured at Cheju Island, Korea, over the 3-year period March 1992 to February 1995 are presented and discussed, with a particular emphasis on the Pacific Exploratory Mission in the Western Pacific (PEM-West B) time period. Cheju Island is under the influence of continental outflow conditions nearly 70% of the year, and as a result the aerosol loading of sea salt as well as continental aerosol components is high. The 3-year mean values derived from the daily tape filters are non-sea-salt (nss) SO22− = 6.8 μg/m3, NO3− = 1.2 μg/m3, Cl− = 1.9 μg/m3, Na+ = 1.7 μg/m3, Ca2+ = 0.5 μg/m3, NH4+ = 1.3 μg/m3, Mg2+ = 0.3 μg/m3, and K+ = 0.4 μg/m3. Sea-salt components show peak values in winter, while calcium, nitrate, potassium, and to a lesser extent, sulfate and ammonium, show higher values in the spring, and all species exhibit a pronounced minimum in summer. Trajectory and principal component analysis show that elevated levels of primary aerosols (both sea salt and soil-derived) occur with strong wind conditions associated with winter and spring, and high concentrations of non-sea-salt components are most strongly associated with springtime continental outflow events. During the PEM-West B period, nitrate and calcium are found to be ∼60% higher than the annual mean, sea-salt components ∼30% higher, and sulfate ∼10% higher. The aerosol data are combined with gaseous SO2 concentrations, precipitation chemistry data and companion aerosol measurements taken at the same site, to provide further insights into the aerosol composition at Cheju. At Cheju, sulfate and ammonium are found mostly in the fine fraction (∼80 to 90%), while calcium and nitrate reside in the coarse size fraction. Sulfate and nitrate are not associated with the primary aerosols, but rather become associated with the aerosol during the long-range transport process.

Long‐range transport of ozone in the East Asian Pacific rim region

Measurements of surface ozone were conducted at three remote island sites in the East Asian Pacific rim region during the Pacific Exploratory Mission-West (A) campaign period in September–October, 1991. The ozone concentrations observed at the three measurement stations at Oki and Okinawa, Japan, and Kenting, Taiwan, had similar ranges varying between 6–63, 8–58, and 4–65 ppb, respectively, except for one event of short-range transport of polluted air at Kenting. Day-to-day variations have been analyzed by using backward air parcel trajectories on isentropic surfaces. The results showed that continental air masses which originated from northwestern Asia and passed through the high anthropogenic emission region of East Asia contained the highest concentration of ozone, 30–60 ppb with an average of 43–45 ppb at the three stations. In contrast, the lowest concentrations were observed for air parcels originating from the mid-Pacific and transported without mixing with the continental outflow. These parcels contained 5–20 ppb of ozone with the average of 11, 15, and 9 ppb at Oki, Okinawa, and Kenting, respectively. The air parcels from the South China Sea contained 22 and 18 ppb of ozone at Okinawa and Kenting, respectively, which were higher than those from mid-Pacific. Continental air mass from the north-northeast to Oki containing 35–40 ppb ozone with the average of 37 ppb was recognized as continental “background.” The high ozone concentrations in the northwesterly continental outflow exceeding the background was ascribed to photochemical buildup in the planetary boundary layer.

Measurements of NO, NO y , CO and O3 and estimation of the ozone production rate at Oki Island, Japan, during PEM‐West

Measurements of NO, NOy, CO, and O3 were conducted at Oki Island, 65 km west of the Japanese mainland during September–October 1991. The results show that the Oki Island site is relatively clean with mean (and median) CO and NOy concentrations of 137 (130) ppbv and 713 (505) pptv, respectively. These relatively low concentrations reflect the frequent occurrence of windsfrom the less populated regions to the north during this campaign. During several periods, elevated CO, NOy, and O3 concentrations were associated with transport of pollutants from Japan and Korea. CO and NOy are significantly correlated in the entire data set, reflecting the overall influence of anthropogenic emissions. Mean CO and NOy concentrations show small diurnal cycles with a maximum in the morning and early evening hours. Hourly mean O3 concentrations exhibit a diurnal cycle of amplitude 3.5 parts per billion by volume, with a maximum in the early afternoon attributed to photochemical O3 production. The source of this afternoon O3 enhancement is analyzed using regression analysis of O3 and NOy and of O3 and CO. Both NOy and CO are significantly correlated with O3 during the daytime but are poorly or insignificantly correlated with O3 at night, indicating that upwind photochemistry operating within the previous ∼1 day was responsible for the observed afternoon O3 enhancement. The NOy-O3 regression analysis indicates formation of ∼9 O3 molecules per NOy molecule reaching Oki Island. The mean and median midday NO concentrations of 55 and 23 parts per trillion by volume, respectively, were sufficient to support net production of O3. Using the results of these measurements and prior modeling studies (Lin et al., 1988), we estimate a “lifetime-averaged” O3 production efficiency of 10 molecules O3 per NOx molecule. Combined with estimated East Asian NOx emissions for 1987, this indicates an annual O3 production of 1.0 × 1014 g O from photochemistry which is approximately 2 times the annual stratospheric flux in this region. This value must be considered as a rough estimate but is probably accurate to within a factor of 2.

Characterization of atmospheric air pollutants at two sites in northern Kyushu, Japan - Chemical form, and chemical reaction

Airborne gaseous and particulate matter in winter was measured over for 37 days in January and December 1997 at 2 sampling sites in northern Kyushu, Japan. One sampling site, Goto Island (an isolated island in the East China Sea), was about 200 km southwest of the other sampling site, Dazaifu city. In winter, acidic sulfates generated over the East Asian continent were transported to northwest Kyushu, to places such as Goto Island and the inland Kyushu area, and high sulfate concentrations were observed at the 2 sampling sites when strong NW winds blew. Acidity around Goto was mainly influenced by particulate NH4HSO4. The concentrations of NH3 at Goto Island were lower than at Dazaifu city. The difference in NH3 levels at the 2 sampling sites plays an important role in the chemical forms and sizes of the particulate matter. Nitrates at Goto Island were mostly present as NaNO3 and Ca(NO3)2 in coarse-size particles. During the process of long-range transport of air pollutants from the Asian continent to Goto, gaseous HNO3 was produced by a photochemical reactions of nitrogen oxides in the atmosphere, and particulate NaNO3 and gaseous HCl were formed by a chlorine-loss reaction between NaCl and gaseous HNO3. When strong NW winds blew, acidic sulfates together with some of the NaNO3 and/or Ca(NO3)2 and some of gaseous HCl and HNO3, which exist in the sea to the west of Kyushu and Goto Island, were transported to inland Kyushu such as Dazaifu city. During the process of transport, most of the acidic sulfates and acidic gases were mixed with regional air pollutants such as chlorides and nitrates existing around Dazaifu city, and neutralized forming (NH4)2SO4, NH4Cl and NH4NO3 in an environment of excess NH3. Therefore, the main chemical forms of NO3− at Dazaifu city varied day-by-day from fine-sized NH4NO3 to coarse-sized NaNO3 and/or Ca(NO3)2. The appearance of NO3− in coarse-size particles at Dazaifu city was due to the transport of NO3− from around the sea to the west of Kyushu.

Long‐range transport of ozone, carbon monoxide, and acidic trace gases at Oki Island, Japan, during PEM‐WEST B/PEACAMPOT B campaign

Ground based measurements of ozone, CO, HNO3 SO2, HCl, and formic acid were carried out at Oki, a remote island site in the Sea of Japan, during Feburuary 26 to March 16, 1994, as the Pacific Exploratory Mission in the Western Pacific/Perturbation by East Asian Continental Air Mass to the Pacific Oceanic Troposphere (PEM-West B/PEACAMPOT B) campaign. According to trajectory analysis, the air mass reaching Oki was classified into four groups: northerly, northwesterly, west-northwesterly, and westerly flows. Clear dependence of gas concentrations on flow direction of air mass was found for all species studied. Lowest concentrations were observed in the northerly airflow originating from the Bering Sea. The mean concentrations of ozone and CO in northerly flow were 37.6±1.9 and 151±1 ppbv, respectively. The mean values of HNO3, SO2, HCl, and formic acid in the northerly flow were 34±10, 41±5, 107±23, and 54±81 pptv, respectively. The highest concentrations of all species were observed in the westerly flow passing through a lower boundary layer over the Yellow Sea and South Korean Peninsula. The mean concentrations of ozone and CO in the westerly flow were 45.9±4.0 and 292±44 ppbv, respectively. The mean values of HNO3, SO2, HCl, and formic acid in the westerly flow were 137±37, 2075±1307, 515±214, and 264±183 pptv, respectively. Clear seasonal variation of the “background” concentrations of ozone and CO were identified by comparison with the data from the PEM-West A/PEACAMPOT A campaign conducted in the fall. In contrast to other species, strong diurnal variation of formic acid with a daytime maximum was observed. The possibility of photochemical formation of formic acid from HCHO and the HO2 radical is discussed.

Numerical study of the atmospheric input of anthropogenic total nitrate to the marginal seas in the western North Pacific region

[1] Atmospheric input of anthropogenic total nitrate to marginal seas in the western North Pacific region was simulated using a regional chemical transport model over East Asia based on year-to-year emission estimates during 1980-2003. Seasonal cycles and concentration levels of gas and aerosol were examined using observation data from various studies. The model simulated total nitrate deposition over the East China Sea (ECS) as 140 GgN/yr, which is the same order of the annual river discharge from the Yangtze River. The ratio of dry and wet deposition over ECS was obtained as approximately 6: 4. Total nitrate deposition over ECS corresponds to 3.2% (N base) of total NO x emission in China. The total deposition at present is three times larger than that of 1980, corresponding with increased NO x emissions.

Aircraft survey of the secondary photochemical pollutants covering the Tokyo metropolitan area

To investigate the photochemical smog formation mechanism over the Kanto Plain, a series of aircraft measurements was conducted from 8 to 12 August 1978 covering the Tokyo Metropolitan area. Various flight patterns were designed to provide appropriate data for determining both the horizontal and vertical pollutant profile. It was found that there is a relationship between the pollutant concentration and the local weather pattern, in particular, the sea-land breeze. 9 August was typical of a sea-land breeze day. In the morning, the sea breeze front formed near the shore, gradually moving inland. The concentration pattern showed two peak regions with the sea breeze front as the dividing line. Using trajectory analysis, it was found that the high concentration zone in the land breeze area is caused by pollutants trapped overnight, and the high concentration zone in the sea breeze region is caused by fresh pollutants. On 12 August 1978, high photochemical smog was observed in the southern part of the Kanto Plain (south of the Tokyo Metropolitan area) caused by just such a complex wind structure. The easterly wind replaced the morning land breeze (northerly wind) during the afternoon. This resulted in a low O3 concentration zone where the clean easterly wind had penetrated into the northern Kanto region. South of this clean zone, a high O3 concentration zone stretched from Tokyo to the Yokohama area. These results show the importance of the long-time transportation of polluted air masses and the complex wind field structure in understanding the behaviour of photochemical smog in this area.

Transport of perfluoroalkyl substances (PFAS) from an arctic glacier to downstream locations: implications for sources.

Perfluoroalkyl substances (PFAS) have been globally detected in various environmental matrices, yet their fate and transport to the Arctic is still unclear, especially for the European Arctic. In this study, concentrations of 17 PFAS were quantified in two ice cores (n=26), surface snow (n=9) and surface water samples (n=14) collected along a spatial gradient in Svalbard, Norway. Concentrations of selected ions (Na(+), SO4(2-), etc.) were also determined for tracing the origins and sources of PFAS. Perfluorobutanoate (PFBA), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) were the dominant compounds found in ice core samples. Taking PFOA, PFNA and perfluorooctane-sulfonate (PFOS) as examples, higher concentrations were detected in the middle layers of the ice cores representing the period of 1997-2000. Lower concentrations of C8-C12 perfluorocarboxylates (PFCAs) were detected in comparison with concentrations measured previously in an ice core from the Canadian Arctic, indicating that contamination levels in the European Arctic are lower. Average PFAS concentrations were found to be lower in surface snow and melted glacier water samples, while increased concentrations were observed in river water downstream near the coastal area. Perfluorohexanesulfonate (PFHxS) was detected in the downstream locations, but not in the glacier, suggesting existence of local sources of this compound. Long-range atmospheric transport of PFAS was the major deposition pathway for the glaciers, while local sources (e.g., skiing activities) were identified in the downstream locations.

Transport of Atmospheric Pollutants from East Asia

Air-borne measurements of air pollutants transported from northeast Asia to Japan and the Pacific Ocean were carried out three times from 1996 to 1999 over the seas between Japan and Asian Continent. Those campaigns were named PEACAMPOT II under auspices of the IGAC/APARE program. A transport pattern of a highly polluted air mass from central China was found. Such air mass was driven by the quick movement of low pressure traveling from Taiwan area to the northeast of Japan. This finding supported well the results of modeling studies for long-range transport of atmospheric pollutants from East Asia.