Air Mass Transport Patterns Research Articles

Long-Range Atmospheric Mercury Transport from Across East Asia to a Suburban Coastal Area in Southern Vietnam.

Exports of atmospheric mercury (Hg) from continental East Asia, a major Hg emitter in the globe, have been reported by several studies in neighboring countries such as Japan and Korea. Nonetheless, studies concerning this topic in Southeast Asia (SEA) countries are still limited. Accordingly, gaseous elemental mercury (GEM) has been measured from Can Thanh High School (CTHS), a suburban coastal site in southern Vietnam to study its characterization and discover the evidence of Hg trans-boundary transport from regional sources (e.g., East Asia). Data collected in July, August, and October 2022 were used in this study, and the overall GEM concentration was 1.61 ± 0.32 ng m-3. The GEM levels were higher in October than in July and August, potentially due to the discrepancy in air mass transport patterns induced by tropical monsoon and source origins of Hg. MERRA-2, backward trajectories, and CALIPSO images revealed the trans-boundary air pollution from continental East Asia to southern Vietnam, evidenced by significantly elevated (> 30%) atmospheric Hg concentrations as well as other air pollutants when the plume arrived at CTHS. Furthermore, our results also imply that atmospheric Hg exported from East Asia could influence large areas in SEA, suggesting the need for more studies in various SEA countries in the upcoming future. This study illustrated the influence of regional Hg emissions on local atmospheric Hg pollution and provided data to improve knowledge of the Hg biogeochemical cycle in SEA.

Understanding ozone episodes during the TRACER-AQ campaign in Houston, Texas: The role of transport and ozone production sensitivity to precursors

This study investigated transport pathways and photochemical formation responsible for ozone exceedances during the September 2021 deployment of the Tracking Aerosol Convection Interactions ExpeRiment/Air Quality (TRACER-AQ) campaign in Houston, Texas. We focused on two ozone episodes, September 6th–September 11th (“Episode 1”) and September 23rd–September 26th (“Episode 2”), when the maximum daily eight-hour average (MDA8) ozone at surface monitors exceeded 70 ppbv. Long-range transport patterns of air masses during these episodes were from the central/northern US. High-resolution (4 km resolution) trajectory analysis with FLEXible PARTicle (FLEXPART) dispersion model revealed local recirculation of air masses and the accumulation of pollutants across Houston contribute to the ozone exceedances. Comprehensive Air Quality Model with extensions (CAMx) driven by 1.33-km resolution meteorology from the Weather Research and Forecast (WRF) tool simulated elevated ozone production rates during ozone episodes across the Houston metropolitan area, with ozone production hotspots mostly over Houston city and industrial districts of the Houston Ship Channel (HSC). The regional increase in ozone production rates was due to the transport of VOC-rich air masses (via northerly flows) that brought ozone precursors to the region, which ultimately caused a transition in the ozone formation tendency from generally VOC-limited to NOx-limited conditions. However, the city of Houston and the HSC remained in a VOC-limited regime because of local NOx emissions that, to some extent, preponderated the impact of transported VOCs. While approximately 37 % of the elevated ozone production was attributed to local photochemistry, the remaining ∼63 % increase in ozone production was due to the transported ozone to the region during episodes, bringing ozone to the Houston region and contributing to ozone exceedances. The outcomes of this study illustrated the synergy between transport and ozone production, both long-range and local scale, which resulted in ozone exceedances in Houston.

Long-term trend of wintertime precipitation chemistry at a remote islet site influenced by anthropogenic emissions from continental East Asia

In this study, the trends and factors influencing wintertime precipitation chemistry at a remote site downwind of continental East Asia were investigated. A total of 336 precipitation samples were collected from 2005 to 2019 at Pengjia Islet, a site ~56 km north of the main island of Taiwan. Overall, the samples had a volume-weighted mean pH of 4.81 (ranging from 3.03 to 7.00), with 74% of samples considered as acid rain (pH < 5). PMF analysis of the samples identified sea-salt, anthropogenic emissions, and dust as sources of major ions in precipitation. Anthropogenic emissions were mostly associated with polluted air from East Asia. Four major air mass transport pathways to Pengjia Islet were identified, in which 87% originated from northern China (i.e. polluted air masses) with a relatively low pH and high ionic concentrations compared to the remaining samples. Wintertime pH values associated with the most common trajectory from China significantly increased at a rate of +1.7% yr−1 (p < 0.01) from 2005 to 2019, similar to those observed at other sites in East Asia in the previous two decades. The increasing pH trend in this study was attributed to the decrease in nss-SO42- concentrations and an increase in Ca2+ concentrations, of which the former aligns with the decrease in nss-SO42- at sites in China caused by the decline of SO2 emissions. The increase of Ca2+ concentrations is supported by the increase of coarse mode aerosol mass concentrations transported to northern Taiwan in winter. By splitting the dataset into two periods (i.e. 2005-2011 and 2012–2019), we found a close relationship between the changes in air-quality control in China and trends in precipitation chemistry at Pengjia Islet, including a consistently decreasing nss-SO42-/NO3− ratio in rainwater. Such a finding has important implications for the effectiveness of air pollution control policies on the regional scale. Additionally, changes in regional transport patterns of air masses might also contribute to the changes in precipitation chemistry at Pengjia Islet.

Large seasonal and interannual variations of biogenic sulfur compounds in the Arctic atmosphere (Svalbard; 78.9° N, 11.9° E)

Abstract. Seasonal to interannual variations in the concentrations of sulfur aerosols (&lt; 2.5 µm in diameter; non sea-salt sulfate: NSS-SO42-; anthropogenic sulfate: Anth-SO42-; biogenic sulfate: Bio-SO42-; methanesulfonic acid: MSA) in the Arctic atmosphere were investigated using measurements of the chemical composition of aerosols collected at Ny-Ålesund, Svalbard (78.9∘ N, 11.9∘ E) from 2015 to 2019. In all measurement years the concentration of NSS-SO42- was highest during the pre-bloom period and rapidly decreased towards summer. During the pre-bloom period we found a strong correlation between NSS-SO42- (sum of Anth-SO42- and Bio-SO42-) and Anth-SO42-. This was because more than 50 % of the NSS-SO42- measured during this period was Anth-SO42-, which originated in northern Europe and was subsequently transported to the Arctic in Arctic haze. Unexpected increases in the concentration of Bio-SO42- aerosols (an oxidation product of dimethylsulfide: DMS) were occasionally found during the pre-bloom period. These probably originated in regions to the south (the North Atlantic Ocean and the Norwegian Sea) rather than in ocean areas in the proximity of Ny-Ålesund. Another oxidation product of DMS is MSA, and the ratio of MSA to Bio-SO42- is extensively used to estimate the total amount of DMS-derived aerosol particles in remote marine environments. The concentration of MSA during the pre-bloom period remained low, primarily because of the greater loss of MSA relative to Bio-SO42- and the suppression of condensation of gaseous MSA onto particles already present in air masses being transported northwards from distant ocean source regions (existing particles). In addition, the low light intensity during the pre-bloom period resulted in a low concentration of photochemically activated oxidant species including OH radicals and BrO; these conditions favored the oxidation pathway of DMS to Bio-SO42- rather than to MSA, which acted to lower the MSA concentration at Ny-Ålesund. The concentration of MSA peaked in May or June and was positively correlated with phytoplankton biomass in the Greenland and Barents seas around Svalbard. As a result, the mean ratio of MSA to the DMS-derived aerosols was low (0.09 ± 0.07) in the pre-bloom period but high (0.32 ± 0.15) in the bloom and post-bloom periods. There was large interannual variability in the ratio of MSA to Bio-SO42- (i.e., 0.24 ± 0.11 in 2017, 0.40 ± 0.14 in 2018, and 0.36 ± 0.14 in 2019) during the bloom and post-bloom periods. This was probably associated with changes in the chemical properties of existing particles, biological activities surrounding the observation site, and air mass transport patterns. Our results indicate that MSA is not a conservative tracer for predicting DMS-derived particles, and the contribution of MSA to the growth of newly formed particles may be much larger during the bloom and post-bloom periods than during the pre-bloom period.

“Military Parade Blue Skies” in Beijing: Decisive Influence of Meteorological Factors on Transport Channel and Atmospheric Pollutant Concentration Level

The severity of high atmospheric pollution has been a major social problem in northern China. To improve the air quality in the Beijing–Tianjin–Hebei (BTH) region and guarantee a suitable environment during the military parade and other celebrating activities for the 70th anniversary of the victory for anti-Fascist Warcraft in the year 2015, a series of strict air quality control policies were carried out. To analyze the reduction extents of PM2.5 and organic matter components during the control period and to examine the meteorological conditions in this region and their decisive influence on the air quality, PM2.5 samples were collected and the Lagrangian particle dispersion model FLEXPART was performed to calculate potential source locations within the BTH region. PM2.5, organic carbon (OC), elementary carbon (EC), and three species types were specifically analyzed. Although the results showed that PM2.5, OC, and EC reduced by 64.55%, 48.74%, and 60.75% during the control period, the air mass transport patterns showed great difference at certain periods, which altered the dominant transport direction of air mass and the potential source region of pollutants and organic matters. This alteration completely changed major atmospheric pollutants sources contribution and caused huge concentration changes. Parallel cases also showed that meteorological conditions could avoid massive atmospheric transported from a major emission source region to a receptor site. The meteorological conditions changed the main contribution source region in control and non-control periods and proved the air quality control measures were less necessary in some southern Hebei cities during special events periods.

Uncertainties of Simulated Aerosol Direct Radiative Effect Induced by Aerosol Chemical Components: A Measurement‐Based Perspective From Urban‐Forest Transition Region in East China

AbstractDifference and uncertainty of the aerosol radiative effects were quantified using the Santa Barbara DISORT Atmospheric Radiative Transfer model and multiple aerosol observation data sets from urban‐forest transition region. The secondary transformed carbonaceous aerosol components and biogenic secondary organic aerosol (BSOA) tracers have dominated over all other components (with a higher concentration in wet season) in terms of its impact on the aerosol radiative forcing (ARF). The averaged organic carbon (OC) and BSOA tracers increased from 13.3 ± 4.99 μg/m3, 29.5 ± 10.7 ng m−3 to 17.3 ± 4.47 μg/m3, 78.7 ± 43.7 ng m−3 in the dry and wet seasons, respectively. The corresponding root mean square errors of single scattering albedo and radiative forcing at the top of the atmosphere have increased by 8.4% and 16.9%. From the dry season to the wet season, the drastically aerosol composition and types variations caused the aerosol radiation effect reverse from cooling to heating. The increase in carbonaceous aerosols and BSOA transformed by forests in the wet season weakened the cooling effects. Driven by multiple factors, such as meteorological conditions, emission sources, and the mixed state of particulate matters, the transport patterns of air masses exhibit completely opposite effects to the ARF. Affected by the source location, wet deposition rate and components residence time, the uncertainty of ARF caused by long‐distance transport of aerosols is 68% higher than that of local aerosol situations under the condition of similar aerosol composition distributions. At similar transport distances, stronger aerosol secondary transformation increases the uncertainty of ARF by 20%.

Source attribution of air pollution using a generalized additive model and particle trajectory clusters.

Speciated hourly measurements of fine aerosols were made for more than two years at an urban, an industrial and a port site in Busan, Korea. A Generalized Additive Model (GAM) was designed to deconvolve factors contributing to the pollutant concentrations at multiple scales. The model yields estimates of source contributions to pollution by separately identifying the signals in the time series due to meteorology, vertical mixing, horizontal wind transport and temporal variations such as diurnal, weekly, seasonal and annual trends. The GAM model was expanded to include FLEXPART back trajectory clusters generated using fuzzy c-means clustering. This made it possible to quantify the impact of long-range transport using the Trajectory Cluster Contribution Function (TCCF). TCCF provides a development of methods such as Concentration Field Analysis and Potential Source Contribution Function by providing numerical estimates of concentration changes associated with different air mass transport patterns while accounting for possible confounding factors from meteorology. The GAM simulations identified the importance of local transport for primary pollutants and long-range transport from China for secondary pollutants. Local factors accounted for up to 72% of the variance in concentrations of NO2 and elemental carbon whereas large-scale/seasonal factors accounted for up to 56% of PM2.5 and 80% of inorganic species. The algorithm further identified the importance of the weekend effect and the holiday effect at the different sites in Busan. The residual from the analysis was used to estimate the impact of the COVID-19 pandemic. The signature of the pandemic was different between the pollutants as well as from site to site. The model was able to distinguish small impacts from local pollutants at the residential site; short-lived acute impacts from industrial changes; and longer-term changes due to the early pandemic response in China.

Links between airborne microbiome, meteorology, and chemical composition in northwestern Turkey

The composition of atmospheric aerosols is dynamic and influenced by their emission sources, organic and inorganic composition, transport pathways, chemical and physical processes, microorganisms' content and more. Characterization of such factors can improve the ability to evaluate air quality and health risks under different atmospheric scenarios. Here we investigate the microbial composition of the atmospheric particulate matter (<10 μm; PM10), sampled in Bolu, Turkey, and the linkage to the chemical composition changes, and different environmental factors. We show distinct differences between aerosol composition of different sources and air-mass transport patterns, sampled in July–August 2017 and in February 2018. The summer samples had a typical northern component air mass trajectories and higher local wind speed. They were characterized by high PM10 levels, marine and mineral dust tracers and high relative abundance of Ascomycota, suggesting long-range transport of the particles from remote sources. In contrast, samples collected in February were characterized by a dominant contribution of southern air masses, and low wind speed. They had low PM10 values, higher relative abundance of antibiotic resistance genes and anthropogenic ions related to local industries and farming, suggesting a dominance of local sources. With the microbiome analyses reported here for the first time for this region, we show good agreement between airborne microbial composition, aerosol mass load, chemistry, and meteorology. These results allow better air quality evaluation and prediction capabilities.

Primary sources control the variability of aerosol optical properties in the Antarctic Peninsula

Aerosol particle optical properties were measured continuously between years 2013–2015 at the Marambio station in the Antarctic Peninsula. Annual cycles of particle scattering and absorption were studied and explained using measured particle chemical composition and the analysis of air mass transport patterns. The particle scattering was found elevated during the winter but the absorption did not show any clear annual cycle. The aerosol single scattering albedo at nm was on average 0.96 0.10, with a median of 0.99. Aerosol scattering Ångström exponent increased during summer, indicating an increasing fraction of fine mode particles. The aerosol was mainly composed of sea salt, sulphate and crustal soil minerals, and most of the particle mass were in the coarse mode. Both the particle absorption and scattering were increased during high wind speeds. This was explained by the dominance of the primary marine sea-spray and wind-blown soil dust sources. In contrast, the back-trajectory analysis suggested that long-range transport has only a minor role as a source of absorbing aerosol at the peninsula.

A sub-decadal trend in diacids in atmospheric aerosols in eastern Asia

Abstract. Change in secondary organic aerosols (SOAs) has been predicted to be highly uncertain in the future atmosphere in Asia. To better quantify the SOA change, we examine the sub-decadal (2001–2008) trend in major surrogate compounds (C2–C10 diacids) of SOA in atmospheric aerosols from Gosan site on Cheju Island, South Korea. The Gosan site is influenced by pollution outflows from eastern Asia. The molecular distributions of diacids were characterized by the predominance of oxalic (C2) acid followed by malonic (C3) and succinic (C4) acids in each year. The seasonal variations in diacids in each year were characterized by the highest concentrations of saturated diacids in spring and unsaturated diacids in winter. The consistent molecular distributions and seasonal variations along with significantly similar air mass transport patterns are indicative of similar pollution sources for diacids in eastern Asia on a sub-decadal scale. However, the intensity of the pollution sources has increased as evidenced by the increases in major diacids at the rate of 3.9–47.4 % per year, particularly in April. The temporal variations in atmospheric tracer compounds (carbon monoxide, levoglucosan, 2-methyltetrols, pinic acid, glyoxylic acid, glyoxal and methylglyoxal) suggest that the increases in diacids are due to enhanced precursor emissions associated with more anthropogenic than biogenic activities followed by the compounds' chemical processing in the atmosphere. The trends in diacids contrast with the reported decreases in sulfate, nitrate and ammonium in recent years in eastern Asia. This study demonstrates that recent pollution control strategies in eastern Asia were not able to decrease organic acidic species in the atmosphere. The increases in water-soluble organic acid fraction could modify the aerosol organic composition and its sensitivity to climate relevant physical properties.

Increase in Aerosol Black Carbon in the 2000s over Ny-Ålesund in the Summer

Abstract To investigate the concentrations, sources, and temporal variations of atmospheric black carbon (BC) in the summer Arctic, routine ground-level observations of BC by optical absorption were made in the summer from 2005 to 2008 at the Chinese Arctic “Yellow River” Station (78°55′N, 11°56′E) at Ny-Ålesund on the island of Spitsbergen in the Svalbard Archipelago. Methods of the ensemble empirical-mode decomposition analysis and back-trajectory analysis were employed to assess temporal variation embedded in the BC datasets and airmass transport patterns. The 10th-percentile and median values of BC concentrations were 7.2 and 14.6 ng m−3, respectively, and hourly average BC concentrations ranged from 2.5 to 54.6 ng m−3. A gradual increase was found by 4 ng m−3 a−1. This increase was not seen in the Zeppelin Station and it seemed to contrast with the prevalent conception of generally decreasing BC concentration since 1989 in the Arctic. Factors responsible for this increase such as changes in emissions and atmospheric transport were taken into consideration. The result indicated that BC from local emissions was mostly responsible for the observed increase from 2005 to 2008. BC temporal variation in the summer was controlled by the atmospheric circulation, which presented a significant 6–14-day variation and coherent with 1–3- and 2–5-day and longer cycle variation. Although the atmospheric circulation changes from 2005 to 2008, there was not a marked trend in long-range transportation of BC. This study suggested that local emissions might have significant implication for the regional radiative energy balance at Ny-Ålesund.

Atmospheric black carbon and sulfate concentrations in Northeast Greenland

Abstract. Measurements of equivalent black carbon (EBC) in aerosols at the high Arctic field site Villum Research Station (VRS) at Station Nord in North Greenland showed a seasonal variation in EBC concentrations with a maximum in winter and spring at ground level. Average measured concentrations were about 0.067 ± 0.071 for the winter and 0.011 ± 0.009 for the summer period. These data were obtained using a multi-angle absorption photometer (MAAP). A similar seasonal pattern was found for sulfate concentrations with a maximum level during winter and spring analyzed by ion chromatography. Here, measured average concentrations were about 0.485 ± 0.397 for the winter and 0.112 ± 0.072 for the summer period. A correlation between EBC and sulfate concentrations was observed over the years 2011 to 2013 stating a correlation coefficient of R2 = 0.72. This finding gives the hint that most likely transport of primary emitted BC particles to the Arctic was accompanied by aging of the aerosols through condensational processes. BC and sulfate are known to have only partly similar sources with respect to their transport pathways when reaching the high Arctic. Aging processes may have led to the formation of secondary inorganic matter and further transport of BC particles as cloud processing and further washout of particles is less likely based on the typically observed transport patterns of air masses arriving at VRS. Additionally, concentrations of EC (elemental carbon) based on a thermo-optical method were determined and compared to EBC measurements. EBC measurements were generally higher, but a correlation between EC and EBC resulted in a correlation coefficient of R2 = 0.64. Model estimates of the climate forcing due to BC in the Arctic are based on contributions of long-range transported BC during spring and summer. The measured concentrations were here compared with model results obtained by the Danish Eulerian Hemispheric Model, DEHM. Good agreement between measured and modeled concentrations of both EBC/BC and sulfate was observed. Also, the correlation between BC and sulfate concentrations was confirmed based on the model results observed over the years 2011 to 2013 stating a correlation coefficient of R2 = 0.74. The dominant source is found to be combustion of fossil fuel with biomass burning as a minor, albeit significant source.

Quantifying the contribution of long-range transport to particulate matter (PM) mass loadings at a suburban site in the north-western Indo-Gangetic Plain (NW-IGP)

Abstract. Many sites in the densely populated Indo-Gangetic Plain (IGP) frequently exceed the national ambient air quality standard (NAAQS) of 100 μg m−3 for 24 h average PM10 and 60 μg m−3 for 24 h average PM2.5 mass loadings, exposing residents to hazardous levels of particulate matter (PM) throughout the year. We quantify the contribution of long-range transport to elevated PM levels and the number of exceedance events through a back-trajectory climatology analysis of air masses arriving at the IISER Mohali Atmospheric Chemistry facility (30.667° N, 76.729° E; 310 m a.m.s.l.) for the period August 2011–June 2013. Air masses arriving at the receptor site were classified into six clusters, which represent synoptic-scale air-mass transport patterns. Long-range transport from the west leads to significant enhancements in the average fine- and coarse-mode PM mass loadings during all seasons. The contribution of long-range transport from the west and south-west (source regions: Arabia, Thar Desert, Middle East and Afghanistan) to coarse-mode PM varied between 9 and 57 % of the total PM10–2.5 mass. Local pollution episodes (wind speed &lt; 1 m s−1) contributed to enhanced PM2.5 mass loadings during both the winter and summer seasons and to enhanced coarse-mode PM only during the winter season. South-easterly air masses (source region: eastern IGP) were associated with significantly lower fine- and coarse-mode PM mass loadings during all seasons. The fraction of days in each season during which the PM mass loadings exceeded the national ambient air quality standard was controlled by long-range transport to a much lesser degree. For the local cluster, which represents regional air masses (source region: NW-IGP), the fraction of days during which the national ambient air quality standard (NAAQS) of 60 μg m−3 for 24 h average PM2.5 was exceeded varied between 36 % of the days associated with this synoptic-scale transport during the monsoon, and 95 % during post-monsoon and winter seasons; the fraction of days during which the NAAQS of 100 μg m−3 for the 24 h average PM10 was exceeded, varied between 48 % during the monsoon and 98 % during the post-monsoon season. Long-range transport was responsible for both, bringing air masses with a significantly lower fraction of exceedance days from the eastern IGP and air masses with a moderate increase in the fraction of exceedance days from the west (source regions: Arabia, Thar Desert, Middle East and Afghanistan). In order to bring PM mass loadings into compliance with the NAAQS and to reduce the number of exceedance days, mitigation of regional combustion sources in the NW-IGP needs to be given highest priority.

Comparison of Spheroidal Carbonaceous Particle Data with Modelled Atmospheric Black Carbon Concentration and Deposition and Air Mass Sources in Northern Europe, 1850–2010

Spheroidal carbonaceous particles (SCP) are a well-defined fraction of black carbon (BC), produced only by the incomplete combustion of fossil fuels such as coal and oil. Their past concentrations have been studied using environmental archives, but, additionally, historical trends of BC concentration and deposition can be estimated by modelling. These models are based on BC emission inventories, but actual measurements of BC concentration and deposition play an essential role in their evaluation and validation. We use the chemistry transport model OsloCTM2 to model historical time series of BC concentration and deposition from energy and industrial sources and compare these to sedimentary measurements of SCPs obtained from lake sediments in Northern Europe from 1850 to 2010. To determine the origin of SCPs we generated back trajectories of air masses to the study sites. Generally, trends of SCP deposition and modelled results agree reasonably well, showing rapidly increasing values from 1950, to a peak in 1980, and a decrease towards the present. Empirical SCP data show differences in deposition magnitude between the sites that are not captured by the model but which may be explained by different air mass transport patterns. The results highlight the need for numerous observational records to reliably validate model results.

Variations of surface ozone concentration across the Klang Valley, Malaysia

Hourly air quality data covering the period 2004–2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August. Analysis of daily variations in surface O3 and the precursors – NO, NO2, CO, NMHC and UVb, indicate that the surface O3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NOx, particularly through tritration processes. Although results from our study suggested that NMHCs may influence the maximum O3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O3 around the Klang Valley. HYSPLIT back trajectories (−72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O3 in the study area. Results show that 47% of the high O3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast.

Observation of the Movement of the Precipitation by Using Tritium Tracer

Tracer techniques have proven to be one of the most powerful tools to characterize the movement of air mass and pollutant transport in hydrological systems. In order to clarify the behavior of low-level tritium in the rain water, we have employed the measuring method of tritium applying a distillation process and an electrolytic enrichment process. The activity of tritium (T specific activity) in the obtained water was measured by liquid scintillation counter. This procedure was applied to bulk precipitation, imitative ground infiltrated precipitation and short term precipitation collected in Niigata City. Moreover, we investigated the concentrations of cations (Na+, K+, Ca2+, and Mg2+) in the precipitation to associate with air mass transport patterns arriving at the place. From the above mentioned, next matters have been clarified:(1) T specific activity in precipitation was found to have a strong dependence on location and season. (2) The chemical components in precipitation during typhoon have notable character of marine air mass. (3) Associated ions in monthly precipitation showed seasonal variation, in fact, the seasonal variation of Ca2+ and tritium were very similar. (4) Backward trajectory analysis method is useful for the analysis of the behavior of T specific activity and several ions in short-term precipitation.

2006-2008년 봄철 부산 지역 PM10과 PM2.5의 질량농도 및 금속성분의 화학적 특성

본 연구에서는 2006년부터 2008년까지 3년간 봄철에 <TEX>$PM_{10}$</TEX>과 <TEX>$PM_{2.5}$</TEX>를 채취하여 질량농도와 금속원소의 화학적 특성, 기상인자와의 관계 분석, 황사 및 비황사시의 미세먼지 특성 그리고 이동경로에 따른 농도의 특성을 고찰하였다. 연구기간동안의 <TEX>$PM_{10}$</TEX>, <TEX>$PM_{2.5}$</TEX>, <TEX>$PM_{10-2.5}$</TEX>평균농도는 각각 <TEX>$126.2{\pm}89.8$</TEX>, <TEX>$85.5{\pm}41.6$</TEX>, <TEX>$40.7{\pm}54.9{\mu}g/m^3$</TEX>이었으며 <TEX>$PM_{2.5}/PM_{10}$</TEX> 및 <TEX>$PM_{10-2.5}/PM_{2.5}$</TEX> 비는 각각 0.70, 0.48이었다. 우리나라의 북서쪽인 북경을 포함한 지역과 서쪽인 상해를 포함한 지역에서 공기덩어리가 이류 할 때 가장 높은 미세먼지농도를 나타내었다. Twenty-four hour integrated <TEX>$PM_{10}$</TEX> and <TEX>$PM_{2.5}$</TEX> samples were measured during springtime (March, April, and May) in Busan for three years from 2006 to 2008, and mass concentrations and metallic elements of measurement were analyzed to investigate temporal, spatial, chemical characteristics of the mass concentration and metallic elements in association with meteorological conditions including Asian Dust (AD) vs. non Asian Dust (NAD) seasons, and other air mass transport patterns. The result showed that <TEX>$PM_{10}$</TEX>, <TEX>$PM_{2.5}$</TEX> and <TEX>$PM_{10-2.5}$</TEX> concentrations were on average of <TEX>$126.2{\pm}89.8$</TEX>, <TEX>$85.5{\pm}41.6$</TEX>, and <TEX>$40.7{\pm}54.9{\mu}g/m^3$</TEX>, respectively, and the <TEX>$PM_{2.5}/PM_{10}$</TEX> and <TEX>$PM_{10-2.5}/PM_{2.5}$</TEX> ratios were 0.70 and 0.48, respectively. The highest concentrations of PM were observed when air parcels were originated from both northwest sector covering Beijing and west sector including Shanghai areas.

Atmospheric transport of water-soluble ions (NO 3−, NH 4+ and nss-SO 42−) to the southern East Sea (Sea of Japan)

Atmospheric deposition of different types of aerosols over the southern East Sea has received little attention in terms of seawater biogeochemistry. We investigated the concentrations of water-soluble ions (NO 3 −, NH 4 + and nss-SO 4 2−) in the aerosols associated with air mass transport patterns arriving at the east coast of Korea, adjacent to the southern East Sea, in order to determine source regions affecting chemical composition of aerosols and to assess the atmospheric pathway as a significant controlling mechanism of the biogeochemistry in this marginal sea. Concentrations of certain elements (Al, Na, Ca, V, Zn and Pb) together with the water-soluble ions were measured in the aerosol samples ( n = 34) collected during the period March 2002–February 2003. The geometric mean concentrations of the water-soluble ions were NO 3 − 2.98 (0.56–16.22), NH 4 + 1.42 (0.37–6.73) and nss-SO 4 2− 2.47 (0.17–17.35) μg m − 3 . The backward trajectories revealed that air masses passing slowly over eastern China contributed more to increases in the concentrations of water-soluble ions than those associated with fast-moving northwesterly and maritime winds. Therefore, the correlation between the NH 4 + and NO 3 + concentrations increased, suggesting that gas-phase NH 3 and HNO 3 was forming fine-mode NH 4NO 3. The atmospheric N input accounted for ∼ 10% of new production over the southern East Sea on an annual scale, while it accounted for over ∼ 25% of new production during the water column stratification seasons (summer and early fall).

Distant source contributions to PM 10 profile evaluated by SOM based cluster analysis of air mass trajectory sets

This paper evaluates the effects of long-range transport patterns of air masses to the regional PM profile in a megacity, Istanbul, Turkey. Five-day hourly backward trajectories were obtained by the HYSPLIT model for selected episodic events in 2008. Self Organizing Maps (SOM), a very powerful classification tool, was used to cluster these trajectories. In total, eight cluster groups were obtained. All of the clusters were evaluated with respect to inhalable particulate matter (PM 10) concentrations observed in Istanbul for the arrival times of the trajectories. Istanbul is generally under the effect of trajectories in three clusters (1, 2 and 4) (52% of all pre-selected episodic events), which have higher mean concentration values than the mean value of all the samples. These clusters typically make significant PM contributions to Istanbul's air quality. PM loadings of the trajectories in these clusters were attributed to massive anthropogenic activity over all of Europe and southwestern air flow most likely carrying PM 10 atmospheric particles originating from the Saharan Desert and other global dust generation regions located in the northern part of Africa.

Ground-level ozone in the Pearl River Delta region: Analysis of data from a recently established regional air quality monitoring network

The ambient air quality monitoring data of 2006 and 2007 from a recently established Pearl River Delta (PRD) regional air quality monitoring network are analyzed to investigate the characteristics of ground-level ozone in the region. Four sites covering urban, suburban, rural and coastal areas are selected as representatives for detailed analysis in this paper. The results show that there are distinct seasonal and diurnal cycles in ground-level ozone across the PRD region. Low ozone concentrations are generally observed in summer, while high O 3 levels are typically found in autumn. The O 3 diurnal variations in the urban areas are larger than those at the rural sites. The O 3 concentrations showed no statistically significant difference between weekend and weekdays in contrast to the findings in many other urban areas in the world. The average ozone concentrations are lower in urban areas compared to the sites outside urban centers. Back trajectories are used to show the major air-mass transport patterns and to examine the changes in ozone from the respective upwind sites to a site in the center of the PRD (Wanqingsha). The results show higher average ozone concentrations at the upwind sites in the continental and coastal air masses, but higher 1 h-max O 3 concentrations (by 8–16 ppbv) at the center PRD site under each of air-mass category, suggesting that the ozone pollution in the PRD region exhibits both regional and super-regional characteristics.