Air Mass Pathways Research Articles

Classifying moisture sources associated with snowfall in the mountains of Lesotho

An average of eight snowfall events occur each year in the eastern Lesotho Highlands. These snowfall events are typically associated with cut-off low (CoLs) systems and mid-latitude cyclones. However, the moisture sources of the snowfall are unclassified and unclear. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, an air mass back trajectory model, has been used to evaluate moisture source waters locally in southern Africa and internationally in China and Europe. This study uses HYSPLIT to determine the source moisture of snow in Lesotho. A list of all 82 snowfall events in Lesotho spanning 2017 to 2022 was compiled using the Snow Report SA Instagram page, including the date and location of snowfall. A 72-hour back trajectory for each snowfall event was initiated for both Afriski and the whole of Lesotho. This amounts to models of moisture source trajectories for 28 and 82 snowfall days, respectively. These air mass pathways are classified according to their frequency per snowfall event, per month in the snow season, per year and for the full period. From this, associated moisture source regions and dominant air mass trajectories were identified. This study reports that the air mass trajectories associated with Afriski and Lesotho as a whole are very similar. The most common pathway of air mass trajectories transporting snow-bearing moisture to Lesotho was an inland trajectory from the northern regions of southern Africa. This pathway makes up 16.6% of all trajectories reported and is associated with the Angola Low, the Congo Air Boundary and the St. Helena High Pressure.

Global atmospheric monitoring of radionuclides and noble gases: Insights into the interhemispheric transport of anthropogenic emissions

The radioactivity measurements registered in the aftermath of the Fukushima accident by the International Monitoring System (IMS) network provide evidence of North-to-South air mass transport. On a smaller scale, similar evidence is also provided by the episodic releases of both radioactive particles and noble gas from civil nuclear facilities. These anthropogenic releases are collected by the stations of the IMS radionuclide (RN) network during normal routine operations.Atmospheric transport modelling (ATM) calculations enable identification of possible source areas of these radionuclide detections. It is demonstrated that the IMS stations located in the band between the Equator and the Tropic of Capricorn can occasionally be influenced by anthropogenic radioactive emissions from facilities located in the Northern Hemisphere. North-to-South air mass transport is however a rather rare – but observed – phenomenon. It is more frequently observed between January and April.ATM backward simulations show that the actual pathways of air masses depend on the prevailing wind direction and vary from station to station. In most cases air masses need less than 14 days (which is the maximum number of days for ATM operational backward simulations at the CTBTO) to be transported from the emission source and go across the Equator. However, for more isolated IMS stations, strongly influenced by trade winds like RN51 (Kavieng, Papua New Guinea) or RN26 (Nadi, Fiji), it can be demonstrated that this operational criterion is often not adapted as transport of air masses from release to collection points can be much longer. It is therefore recommended that the ATM backward simulations performed at the CTBTO are extended to at least 21 days in routine operations.

Seasonal variation of mercury in cloud water at a mountaintop in subtropical Hong Kong: Influences of transboundary transport and sea-salt aerosol

Understanding the distribution and controlling factors of mercury (Hg) speciation in cloud water is crucial for predicting the fate of atmospheric Hg and assessing the environmental impacts of Hg in cloud water. In this study, we collected 85 cloud water samples during autumn and spring at a mountaintop (957 m a.s.l.) in Hong Kong, China. The concentrations of total Hg (THg) in cloud water varied from 3.6 to 225.3 ng L−1, with volume-weighted mean values of 32.1 ng L−1 in autumn and 24.4 ng L−1 in spring. Due to the strong acidic condition of the cloud water, dissolved Hg (DHg) contributed to two-thirds of THg, with Hg complexes by dissolved organic matter (DOM) and chloride being the predominant species of DHg according to chemical equilibrium modeling simulations. Moreover, the levels of Hg-DOM were significantly higher in autumn cloud water compared to spring, and the latter contained more Hg(II)-halide complexes. These differences could be attributed to the different air mass pathways and their emission sources. By combining backward trajectories and Positive Matrix Factorization (PMF) models, we found that air masses originating from the inland Pearl River Delta region, which were only present in autumn cloud water and strongly influenced by stationary coal combustion, were responsible for the highest concentrations of THg, DHg, particulate Hg (PHg) and Hg-DOM. Additionally, air masses originating from regions in China-Indochina Peninsula were only found in spring samples and were significantly influenced by stationary coal combustion, industrial and biogenic sources, contributing to elevated proportions of methylmercury (MeHg) and PHg. In contrast, marine air masses mainly from the western Pacific Ocean contributed to high levels of Hg(II)-halide complexes, especially in spring cloud water. The dissolution and conversion of Hg from sea salt aerosols played a significant role in the enhanced DHg levels observed during cloud processing.

Seasonal Characteristics of Long-Range Transport and Potential Associated Sources of Particulate Matter (Pm<sub>10</sub>) Pollution at the Station Elk, Poland, on 2021-2022 Data

The current study aimed to determine the potential sources of distant emissions of PM10 particles that significantly affect PM10 levels at a given site in southeastern Baltic. The EEA Air Quality Monitoring Station in Elk City, northeastern Poland, was selected for this study. This station is located approximately 50 km from the border of the Russian exclave (Kaliningrad Region). In this study, the NOAA HYSPLIT_4 trajectory model, potential source contribution function (PSCF), and concentration-weight trajectory (CWT) were employed to investigate the origin of the measured PM10 mass at a receptor site. PSCF and CWT utilize back-trajectory analysis and Lagrangian particle dispersion simulations to reconstruct the advection pathways of air masses arriving at the site. These reconstructed retroplumes provide detailed information regarding the geographic locations traversed by polluted air masses on their way to the receptor. By integrating trajectory information with concurrent pollutant concentration data, the PSCF and CWT enable the identification of potential source regions and quantification of their impact on the observed atmospheric levels. From January 1, 2021, to December 31, 2022, at 200 m the 72h backward trajectories of air masses entering the receptor point were calculated and categorized by clustering them into 5-4-4-5 clusters. Subsequently, the PM10 levels at the Elk site associated with each air mass cluster were examined during the observation period. The seasonal variation in PM10 was generally characterized by a peak in winter and minimum values in summer. PM10 was lower during warmer periods, particularly during summer, and significantly, higher concentrations were observed during colder periods. Cluster analyses showed that airflow followed a seasonal pattern, with different results obtained in different seasons. According to the PSCF and CWT results, in winter and spring, the receptor site was influenced more by long-range PM10 pollution, particularly from heavily industrialized areas in Central-Eastern Europe. In contrast, in summer and autumn, the receptor site was less influenced by long-range pollution. The findings demonstrate that the seasonal distributions of PM10 source areas obtained using these two methods generally share similar characteristics, suggesting the credibility and accuracy of the analytical results.

Investigating the spatio-temporal pattern of PM2.5 concentrations in Jiangsu Province, China

PM2.5 is a typical air pollutant which has harmful health effects worldwide, particularly in the developing countries such as China due to significant air pollution. The objectives of this study were to investigate the spatio-temporal pattern of PM2.5 concentration in Jiangsu Province, China. The data were collected from 72 monitoring stations between 2018-21 and the HYSPLIT model was used to study the transport pathways of air masses. According to the obtained results, the concentration of PM2.5 was obvious during the study duration. The results show that the concentration of PM2.5 was constantly decreased from 2018 to 2021, while the level of PM2.5 was higher in winter and lower in summer in Jiangsu. The backward trajectory analysis revealed that the trajectories were originated from the Siberia, Russia and passed thorough Mongolia and northwestern parts of China then reached at the study spot. These air masses played a significant role in aerosol pathway and affect the air quality of Jiangsu.

Trajectory-geospatial approach using HYSPLIT Model in determining air pollution sources at Pasir Gudang industrial areas

Industrial air pollutants emissions can be hazardous to human health and the environment. This study aims to determine the source of air pollution exposure in Malaysia's busiest industrial area, Pasir Gudang by using the trajectory-geospatial approach. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to determine the pathway of air backwards-trajectory. While the geospatial analysis for air pollution sources identification in Pasir Gudang was conducted using Geographic Information System (GIS). Three days of air mass backwards-trajectories were successfully obtained, where the dominant air mass pathways direction came from West Sumatra, Indonesia, influenced by the Southwest monsoon wind. The air mass backwards-trajectories also show there are influenced by nearby factories' emissions. From the geospatial buffer analysis, about 17 to 60 factories were identified to be possible sources of air pollution exposure since the location of factories are within a 1 km buffer zone of six affected schools in Pasir Gudang. The meteorological factors that influence the flow of high emissions of air masses pollutant from nearby factories have worsened the exposure level of air pollution until impacted the health of school’s students. From the findings, a standard of procedure (SOP) for air pollution source identification using a trajectory-geospatial approach has been developed as a guideline for all the stakeholders involved and essential in understanding better strategies in monitoring and mitigating industrial air pollution, particularly in Pasir Gudang as the buffer zones required by the authorities are not actively functioning to mitigate the air pollution exposures. Keywords: Air pollution, buffer zones, HYSPLIT, industrial area, Pasir Gudang, trajectory-geospatial approach

Ozone pollution in the plate and logistics capital of China: Insight into the formation, source apportionment, and regional transport

As the logistics and plate capital of China, the sources and regional transport of O3 in Linyi are different from those in other cities because of the significant differences in industrial structure and geographical location. Twenty-five ozone pollution episodes (OPEs, 52 days) were identified in 2021, with a daily maximum 8-h moving average O3 concentration (O3-MDA8) of 184.5 ± 22.5 μg/m3. Oxygenated volatile organic compounds (OVOCs) and aromatics were the dominant contributors to ozone formation potential (OFP), with contributions of approximately 23.5–52.7% and 20.0–40.8%, respectively, followed by alkenes, alkanes, and alkynes. Formaldehyde, an OVOC with high concentrations emitted from the plate industry and vehicles, contributed the most to OFP (22.7 ± 5.5%), although formaldehyde concentrations only accounted for 9.4 ± 2.7% of the total non-methane hydrocarbon (NMHC) concentrations. The source apportionment results indicated that the plate industry was the dominant O3 contributor (27.0%), followed by other sources (21.6%), vehicle-related sources (18.0%), solvent use (16.9%), liquefied petroleum gas (LPG)/natural gas (NG) (8.8%), and combustion sources (7.7%). Therefore, there is an urgent need to control the plating industry in Linyi to mitigate O3 pollution. The backward trajectory, potential source contribution function (PSCF), and concentration weighted trajectory (CWT) models were used to identify the air mass pathways and potential source areas of air pollutants during the OPEs. O3 pollution was predominantly affected by air masses that originated from eastern and local regions, while trajectories from the south contained the highest O3 concentrations (207.0 μg/m3). The potential source area was from east and south Linyi during the OPEs. Therefore, it is critical to implement regional joint prevention and control measures to lower O3 concentrations.

Impact of international Maritime Organization 2020 sulfur content regulations on port air quality at international hub port

In this study, various characteristics of port air quality that are affected by harbor activities, including ship emissions, were assessed at an international hub port (Busan port) and other major ports in South Korea from November 2017 to December 2020. We conducted an in-depth analysis of aerosol characteristics to investigate the impact of ship emissions, harbor activities, and emission control measures (reinforced limits of sulfur content in fuel oil, from 3.5% to 0.5% mass fraction) on the air quality around the Busan port, South Korea. Our results demonstrate that the impact of ship emissions on port air quality varied significantly according to chemical species. The largest impact on port air quality from ship emissions and air mass pathways (e.g., port wind sector) was confirmed by significantly higher concentrations of SO2 at the port. Our results of regression discontinuity design, a quasi-experimental impact evaluation method, revealed that the implementation of reinforced regulations (i.e., International Maritime Organization 2020 policy) significantly reduced SO2 and NH4+ concentrations at the Busan port, but did not affect the concentrations of PM2.5 and NO2.

Bioaerosols on the atmospheric super highway: An example of long distance transport of Alternaria spores from the Pannonian Plain to Poland

Alternaria spores are pathogenic to agricultural crops, and the longest and the most severe sporulation seasons are predominantly recorded in rural areas, e.g. the Pannonian Plain (PP) in South-Central Europe. In Poland (Central Europe), airborne Alternaria spore concentrations peak between July and August. In this study, we test the hypothesis that the PP is the source of Alternaria spores recorded in Poland after the main sporulation season (September–October).Airborne Alternaria spores (2005–2019) were collected using volumetric Hirst spore traps located in 38 locations along the potential pathways of air masses, i.e. from Serbia, Romania and Hungary, through the Czech Republic, Slovakia and Ukraine, to Northern Poland. Three potential episodes of Long Distance Transport (LDT) were selected and characterized in detail, including the analysis of Alternaria spore data, back trajectory analysis, dispersal modelling, and description of local weather and mesoscale synoptic conditions.During selected episodes, increases in Alternaria spore concentrations in Poznań were recorded at unusual times that deviated from the typical diurnal pattern, i.e. at night or during morning hours. Alternaria spore concentrations on the PP were very high (>1000 spores/m3) at that time. The presence of non-local Ambrosia pollen, common to the PP, were also observed in the air. Air mass trajectory analysis and dispersal modelling showed that the northwest part of the PP, north of the Transdanubian Mountains, was the potential source area of Alternaria spores.Our results show that Alternaria spores are transported over long distances from the PP to Poland. These spores may markedly increase local exposure to Alternaria spores in the receptor area and pose a risk to both human and plant health. Alternaria spores followed the same atmospheric route as previously described LDT ragweed pollen, revealing the existence of an atmospheric super highway that transports bioaerosols from the south to the north of Europe.

Variations in characteristics and transport pathways of PM2.5 during heavy pollution episodes in 2013–2019 in Jinan, a central city in the north China Plain

The characteristics and transport pathways of air masses vary during heavy pollution episodes (HPEs). Three categories of HPEs have been defined: HPE Ι, II, and III, corresponding to HPE durations of 1, 2, and at least 3 days, respectively. Sixty HPEs were investigated in this study. The number of HPEs decreased from 2013 to 2017 and then increased from 2017 to 2019, dominated by emission reductions and meteorological conditions. The average and maximum PM2.5 (i.e., aerodynamic diameter of <2.5 μm) concentrations during those HPEs in 2019 decreased by 5.6%–11.8% and 11.9%–38.5%, respectively, compared with those in 2013. The longer the duration of an HPE, the higher the PM2.5 concentration. Secondary inorganic aerosol concentrations and their contents in PM2.5 during HPE Ⅲ were found to be higher than those during HPEs Ι and Ⅱ, as secondary transformations of precursor gases are more intense during long-term HPEs. The dominant trajectories of airflow arriving in Jinan originated from the southern and southeastern regions during HPEs, realized using the Hybrid Single Particle Lagrangian Integrated Trajectory. The trajectories from the north and west of Jinan contained the highest PM2.5 concentrations of 323.3–432.1 μg/m3 during HPE Ⅲ, although these trajectories only contributed 5.6%–11.1% of the total dominant transport pathways, while those in trajectories from the northwest were highest during HPEs Ι and Ⅱ. The highest contributions of air masses from short distances were found during HPE Ⅲ, of 77.8%, while they were only 65.6% and 47.8% during HPEs Ι and II, respectively. More attention should be given to transport pathways within the short distance from Jinan. Therefore, enhancing regional cooperation in Jinan and surrounding regions (particularly in the south, southeast, northwest, west, and north) is critical for improving air quality in the North China Plain.

Causes of increased pollen exposure during Saharan-Sahel dust intrusions

Airborne particulate matter such as mineral dust comes mainly from natural sources, and the African regions of Sahara and Sahel originate large amounts of the aerosols dispersed worldwide. There is little knowledge about the influence of dust episodes on airborne pollen concentrations, and although the centre and southeast of the Iberian Peninsula are frequently affected by dust intrusions, until now, no specific works have analysed the effect of these episodes on airborne pollen concentrations in these areas. The aims of this study were to analyse the simultaneous occurrence of airborne pollen peaks and Saharan-Sahel dust intrusions in the central and south-eastern Iberian Peninsula, and to study the weather conditions – air mass pathways and conditions of air temperature, relative humidity and atmospheric pressure – that influence the airborne pollen concentrations during dust episodes. The results showed that the rise in airborne pollen concentrations during dust episodes is apparent in inland Iberian areas, although not in coastal areas in the southeast where pollen concentrations are even observed to decrease, coinciding with prevailing easterly winds from the sea. Total pollen concentrations and specific pollen types such as Olea, Poaceae and Quercus showed an increase in the central Iberian Peninsula during dust episodes when two meteorological phenomena concur: 1) prevailing winds from extensive areas of major wind-pollinated pollen sources over a medium or short distance (mainly from western and southwestern areas); and 2) optimal meteorological conditions that favour pollen release and dispersal into the atmosphere (mainly high temperatures and subsequently low humidity in central areas). Both conditions often occur during the Saharan-Sahel dust intrusions in the centre. Maximum pollen peaks are therefore most likely to occur during dust episodes in the central Iberian Peninsula, thus dramatically increasing the risk of outbreaks of pollinosis and other respiratory diseases in the population.

Chemical Composition and Light Absorption of PM2.5 Observed at Two Sites near a Busy Road during Summer and Winter

To examine the difference in the major chemical composition of fine particulate matter (PM2.5) between two roadway sites, 24 h integrated PM2.5 samples were simultaneously collected both 15 m (Buk-Ku District Office (BKO) site) and 150 m (Chonnam National University campus (CNU) site) away from busy roads during the summer and winter periods; these samples were taken to determine the concentrations of organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), and water-soluble inorganic species. In addition, the real-time aerosol light absorption coefficients (Abs) were measured using a dual-spot seven-wavelength aethalometer at the CNU site to evaluate the influence of traffic and biomass burning (BB) emissions on the concentrations of organic aerosol particles. The hourly NO2 concentration was also observed at an air pollution monitoring network that is about 2 km away from the CNU site. During summer, 24 h PM2.5 concentrations (PM2.5 episode) which exceeded the Korean PM2.5 standard (35 μg/m3) were linked to increases in organic matter (OM) and SO42− concentrations that accounted for on average 35–41% and 26–30%, respectively, of the PM2.5 at the two sites. The increased SO42− concentration was most likely attributable to the inflow of long-range transported aerosols, rather than local production, as demonstrated by both the MODIS (Moderate Resolution Imaging Spectroradiometer) images and transport pathways of air masses reaching the sites. On the other hand, the OM, WSOC, and EC concentrations were directly attributable to traffic emissions at the sampling sites, as supported by the tight correlation between the OC and EC. A small difference between the absorption Ångström exponent (AAE) values calculated at wavelengths of 370–950 nm (AAE370–950nm) and 370–520 nm (AAE370–520nm), and the poor correlation of absorption coefficient by brown carbon (BrC) at 370 nm (AbsBrC370nm) with K+ (R2 = 0.00) also suggest a significant contribution of traffic emissions to OM. However, the wintertime PM2.5 episode was strongly related to the enhanced OM and NO3− concentrations, which contributed 26–28% and 22–23% of the PM2.5 concentration, respectively. It is interesting to note that there were two distinct OC/EC ratios in winter: a lower OC/EC (~3.0), which indicates a significant contribution of traffic emissions to the OC and EC, and a higher OC/EC (~6.5), which suggests an additional influence of BB emissions as well as traffic emissions at the sites. Strong correlations between the OC and EC (R2 = 0.72–0.83) and the enhanced AAE370–520nm values compared to the AAE370–950nm support that BB emissions were also an important contributor to the wintertime OM concentrations as well as traffic emissions at the two sites. A good correlation between the gaseous NO2 and NO3− and meteorological conditions (e.g., low wind speed and high relative humidity) suggest that the heterogeneous oxidation of NO2 on moist particles could be an important contributor to wintertime particulate NO3− formation at the sites. The OC concentrations during summer and winter were higher at the BKO site, with a higher traffic flow and a shorter distance from the roadway than at the CNU site. However, there were slight differences in the concentrations of secondary inorganic species (NO3−, SO42−, and NH4+) between the sites during summer and winter.

Chemical composition of rainwater collected from 2006 to 2009 in Mexico City and at a rural site at Morelos State, south central Mexico

The objective of the study was to evaluate the chemical composition of rainwater in urban and suburban areas of central Mexico to identify the possible sources of rainwater contamination. The rainwater was collected at Universidad Nacional Autónoma de Mexico, Campus Ciudad Universitaria (CU), in the southern part of Mexico City at 2200 meters above sea level (m a.s.l.). CU has many green areas with high to moderate traffic densities where air quality presents serious problems of pollution by particulate matter. The other sampling site is a forested rural area (Tlalnepantla), State of Morelos, Mexico, a suburban area 86 km to the south of Mexico City. A total of 145 rainwater samples were collected in the rain period from 2006 to 2009. The ions analyzed were the following: SO42-, NO3-, Cl-, HCO3-, Na+, K+, Ca2+, Mg2+, NH4+ and H+. Ammonium was the most abundant cation in both sites and is one of those responsible for the neutralization of acidic compounds in the atmosphere. The relative abundance of the inorganic anions present in the rainwater was in the following order: SO42- &gt; NO3- &gt; Cl-, for the alkaline metals the order was Ca2+ &gt;Mg2+ &gt; Na+ &gt; K+ and Ca2+ &gt;Mg2+ &gt;K+ &gt;Na+ for CU and Morelos, respectively. A correlation analysis shows a strong positive correlation among the ions, indicating that the most important source was anthropogenic. Air mass back trajectories were associated with the SO42-, Ca2+, Mg2+, NH4+ and H+ concentrations observed on each rainy day. Four factors were used in the statistic analysis and was weighted within each factor. Weights greater than 0.5 are considered to be significant components of each factor. The four factors explain 84.7 % of the total variance of all of the data for CU and 66.9 % for Morelos. All of these factors were associated with all of the analyzed ions. Air pollutant back trajectories were used to understand atmospheric transport and to identify the origins and pathways of air masses influencing the concentrations of the measured ions in rainwater.

Investigating the regional contributions to air pollution in Beijing: a dispersion modelling study using CO as a tracer

Abstract. The rapid urbanization and industrialization of northern China in recent decades has resulted in poor air quality in major cities like Beijing. Transport of air pollution plays a key role in determining the relative influence of local emissions and regional contributions to observed air pollution. In this paper, dispersion modelling (Numerical Atmospheric Modelling Environment, NAME model) is used with emission inventories and in situ ground measurement data to track the pathways of air masses arriving in Beijing. The percentage of time the air masses spent over specific regions during their travel to Beijing is used to assess the effects of regional meteorology on carbon monoxide (CO), a good tracer of anthropogenic emissions. The NAME model is used with the MEIC (Multi-resolution Emission Inventory for China) emission inventories to determine the amount of pollution that is transported to Beijing from the immediate surrounding areas and regions further away. This approach captures the magnitude and variability of CO over Beijing and reveals that CO is strongly driven by transport processes. This study provides a more detailed understanding of relative contributions to air pollution in Beijing under different regional airflow conditions. Approximately 45 % over a 4-year average (2013–2016) of the total CO pollution that affects Beijing is transported from other regions, and about half of this contribution comes from beyond the Hebei and Tianjin regions that immediately surround Beijing. The industrial sector is the dominant emission source from the surrounding regions and contributes over 20 % of the total CO in Beijing. Finally, using PM2.5 to determine high-pollution days, three pollution classification types of pollution were identified and used to analyse the APHH winter campaign and the 4-year period. The results can inform targeted control measures to be implemented by Beijing and the surrounding provinces to tackle air quality problems that affect Beijing and China.

Anomaly-based synoptic analysis on the Heavy Rain Event of July 2018 in Japan

The Heavy Rain Event of July 2018 caused huge social impact and economic losses in Japan. In this study, the anomaly-based synoptic analysis is applied to identify the features and structures of the anomalous synoptic systems during the event period. Results show that the heavy rainfall occurred along the trough of anomalous geopotential height (GPH) and the shear line of anomalous winds at the low troposphere. The anomalous synoptic analysis, by removing the temporal climatology from the total variables, can directly reflect the large-scale features of the event, which includes the actual position of the Baiu front, the pathway of anomalous moist air masses associated with anomalous synoptic systems such as the anomalies of Okhotsk cold high and the Northwest Pacific subtropical high. Meanwhile, the opposite signs between 200 and 850 hPa GPH anomalies, which matches observed rainfall records well, could be a good indicator of the potential heavy rain period. The product of the ensemble prediction systems from the European Centre for Medium-Range Weather Forecasts is able to predict such potential anomalous signals of the Heavy Rain Event for 4–5 days in advance.

Temporal Variations of 7Be and 210Pb Activity Concentrations in the Atmosphere and Aerosol Deposition Velocity in Shenzhen, South China

Naturally occurring beryllium-7 (7Be) and lead-210 (210Pb) serve as powerful tracers in atmospheric studies. In this study, 7Be and 210Pb were simultaneously measured in atmospheric aerosols and deposition samples for an entire year (from January to December 2017) in Shenzhen, South China. The activity concentrations of the airborne 7Be and 210Pb ranged from 0.33 to 9.42 mBq m–3 (averaging 3.23 mBq m–3) and from 0.59 to 4.72 mBq m–3 (averaging 1.58 mBq m–3), respectively, and were observed to be high during the winter but low during the summer. Moreover, the relatively high 210Pb concentration was probably due to the elevated level of radon in this region’s soil. The deposition fluxes of the 7Be and 210Pb were found to range from 0.25 to 3.04 Bq m–2 day–1 (averaging 1.57 Bq m–2 day–1) and from 0.34 to 1.31 Bq m–2 day–1 (averaging 0.73 Bq m–2 day–1), respectively. The temporal trends of these fluxes were largely influenced by rainfall and the origin and pathway of air masses, as well as by atmospheric circulation. Based on their concentrations in the aerosols and their deposition fluxes, the average deposition velocities of 7Be and 210Pb were calculated to be 0.83 and 0.62 cm s–1, respectively. The deposition velocities of both radionuclides correlated well with the amount of rainfall, indicating that precipitation plays a crucial role in removing 7Be and 210Pb from the air. The activity size distributions of these nuclides combined with the characteristic meteorological conditions in this region resulted in high deposition velocities during summer and low ones during winter.

Retrieval of optical and microphysical properties of transported Saharan dust over Athens and Granada based on multi-wavelength Raman lidar measurements: Study of the mixing processes

In this paper we extract the aerosol microphysical properties for a collection of mineral dust cases measured by multi-wavelength depolarization Raman lidar systems located at the National Technical University of Athens (NTUA, Athens, Greece) and the Andalusian Institute for Earth System Research (IISTA-CEAMA, Granada, Spain). The lidar-based retrievals were carried out with the Spheroidal Inversion eXperiments software tool (SphInX) developed at the University of Potsdam (Germany). The software uses regularized inversion of a two-dimensional enhancement of the Mie model based on the spheroid-particle approximation with the aspect ratio determining the particle shape. The selection of the cases was based on the transport time from the source regions to the measuring sites. The aerosol optical depth as measured by AERONET ranged from 0.27 to 0.54 (at 500 nm) depending on the intensity of each event. Our analysis showed the hourly mean particle linear depolarization ratio and particle lidar ratio values at 532 nm ranging from 11 to 34% and from 42 to 79 sr respectively, depending on the mixing status, the corresponding air mass pathways and their transport time. Cases with shorter transport time showed good agreement in terms of the optical and SphInX-retrieved microphysical properties between Athens and Granada providing a complex refractive index value equal to 1.4 + 0.004i. On the other hand, the results for cases with higher transport time deviated from the aforementioned ones as well as from each other, providing, in particular, an imaginary part of the refractive index ranging from 0.002 to 0.005. Reconstructions of two-dimensional shape-size distributions for each selected layer showed that the dominant effective particle shape was prolate with diverse spherical contributions. The retrieved volume concentrations reflect overall the intensity of the episodes.

New particle formation events observed at King Sejong Station, Antarctic Peninsula – Part 1: Physical characteristics and contribution to cloud condensation nuclei

Abstract. The physical characteristics of aerosol particles during particle bursts observed at King Sejong Station in the Antarctic Peninsula from March 2009 to December 2016 were analyzed. This study focuses on the seasonal variation in parameters related to particle formation such as the occurrence, formation rate (FR) and growth rate (GR), condensation sink (CS) and source rate of condensable vapor. The number concentrations during new particle formation (NPF) events varied from 1707 to 83 120 cm−3, with an average of 20 649 ± 9290 cm−3, and the duration of the NPF events ranged from 0.6 to 14.4 h, with a mean of 4.6±1.5 h. The NPF event dominantly occurred during austral summer period (∼72 %). The measured mean values of FR and GR of the aerosol particles were 2.79±1.05 cm−3 s−1 and 0.68±0.27 nm h−1, respectively, showing enhanced rates in the summer season. The mean value of FR at King Sejong Station was higher than that at other sites in Antarctica, at 0.002–0.3 cm−3 s−1, while those of growth rates were relatively similar to the results observed by previous studies, at 0.4–4.3 nm h−1. The derived average values of CS and source rate of condensable vapor were (6.04±2.74)×10-3 s−1 and (5.19±3.51)×104 cm−3 s−1, respectively. The contribution of particle formation to cloud condensation nuclei (CCN) concentration was also investigated. The CCN concentration during the NPF period increased by approximately 11 % compared with the background concentration. In addition, the effects of the origin and pathway of air masses on the characteristics of aerosol particles during a NPF event were determined. The FRs were similar regardless of the origin and pathway, whereas the GRs of particles originating from the Antarctic Peninsula and the Bellingshausen Sea, at 0.77±0.25 and 0.76±0.30 nm h−1, respectively, were higher than those of particles originating from the Weddell Sea (0.41±0.15 nm h−1).

Investigation of the source, morphology, and trace elements associated with atmospheric PM10 and human health risks due to inhalation of carcinogenic elements at Dehradun, an Indo-Himalayan city

To study the physical and chemical properties of atmospheric particulate matter over Dehradun city located along the foothills of the Himalayas, both in situ and satellite-based observations were utilized in the present research. Ambient respirable suspended particles denoted by PM10 (atmospheric particulate matter having an aerodynamic diameter of ≤ 10 µm) was measured during 2016–2017. The morphology and elemental characteristics of PM10 was studied through scanning electron microscopy (SEM) and SEM-energy-dispersive X-ray spectroscopy, respectively. The 24-h mean ± standard deviation of PM10 was observed to be 158.6 ± 33.4 µg/m3, which is more than 2 times the permissible limit of World Health Organization (50 µg/m3). Microscopic analysis revealed particles with irregular, porous, rounded, flaky, chain and branched structures indicating various types such as tar balls, soot, crystalline and biogenic particles. The frequently found particle types were investigated for the atomic percentage contribution, which revealed vehicular exhaust, industrial emission, biomass burning, and crustal/dust re-suspension as the chief source of PM10. To delineate the source and transport pathway of air masses converging over the city, 24-h air mass back trajectories were associated with MODerate resolution Imaging Spectroradiometer derived fire spots, geographical location of cement manufacturing and thermal power plants in the vicinity of monitoring site. Excess cancer risk due to inhalation of Lead particles (mean = 0.159 µg/m3) associated with PM10 was 0.16 × 10−6, which is well below the safe limit (1 × 10−6) framed by the United States Environment Protection Agency.

Source apportionment and health risk assessment of organic constituents in fine ambient aerosols (PM2.5): A complete year study over National Capital Region of India

Fine ambient aerosols (PM2.5) levels in the atmosphere are continuously worsening over Delhi and National Capital Region (NCR) of India. Complete source profiles are required to be assessed for implementation of proper mitigation measures over the NCR. In this study, emission sources of PM2.5 are reported for the NCR of India for samples collected during December 2016 to December 2017 at three sampling sites in Delhi, Uttar Pradesh and Haryana. Organic constituents (n-alkanes, isoprenoid hydrocarbons, polycyclic aromatic hydrocarbons, phthalates, levoglucosan and n-alkanoic acids) in PM2.5 were measured to apportion the sources over the study area. Source apportionment of PM2.5 was performed using organic constituents by Positive Matrix Factorization (PMF) and Principal Component Analysis (PCA). Health risk associated with organic pollutants [PAHs and carcinogen BEHP bis(2-ethylhexyl) phthalate] demonstrated the threat of PM2.5 exposure via inhalation. Transport pathways of air masses were evaluated using 3-day backward trajectories and observed that some air masses originated from local sources along with long-range transport which influenced the PAHs concentration during most of the study period over the NCR. PMF and PCA resulted in the five major emission sources [vehicular emissions (32.2%), biomass burning (30%), cooking emissions (16.8%), plastic burning (13.4%), mixed sources (7.6%) including biogenic and industrial emissions] for PM2.5 over the sampling sites. The present study reveals that transport sector is a major source to be targeted to reduce the vehicular emissions and consequent health risks associated with organic pollutants especially PAHs.