Backward Air Mass Trajectories Research Articles

Molecular characterization of organic aerosols over the Tibetan Plateau: Spatiotemporal variations, sources, and potential implications

Organic aerosols have profound and far-reaching influences on the Earth's climate, ecosystems, environmental quality, and public health. Elucidating the precise composition and sources of these aerosols over the Tibetan Plateau, a region highly sensitive to climate change and vulnerable to ecosystems, is critically important. Sixteen organic molecular tracers in aerosols were quantified using solvent extraction-BSTFA derivatization, and GC/MS analysis at six sites over the Tibetan Plateau during 2014 and 2016. Average total tracer concentration was 32.5 ± 20.1 ng m−3. The highest levels of biomass burning tracers (anhydrosugars and aromatic acids) were found at southeastern Tibetan Plateau site Yulong (20.8 ± 21.3 ng m−3) followed by the western site Ngari (13.3 ± 10.6 ng m−3). Biomass burning tracers decreased from southern sites like Everest (9.50 ± 10.5 ng m−3) to northern aeras such as Laohugou (2.59 ± 2.19 ng m−3). Biomass burning tracers peaked in non-monsoon seasons while primary saccharides and sugar alcohols predominated during monsoon months. Using tracer-based methods, biomass burning contributed 0.4%–8.4% of organic carbon over the plateau, with higher non-monsoon contributions (3.6% ± 3.7%). Backward air mass trajectories and fire spots indicated South Asian biomass burning impacts on organic aerosols at western, southern, and southeastern Tibetan Plateau sites, particularly in non-monsoon periods. Fungal spores and plant debris comprised 0.6%–6.3% and 0.3%–1.2% of organic carbon respectively, with higher monsoon contributions (4.2% ± 4.7%) of fungal spores. Secondary organic carbon was estimated to contribute substantially (45.5%–73.5%) over the plateau but requires further investigation. These results provide insights into pollution mitigation and the assessments of climate and ecology changes for the Tibetan Plateau.

Study on O3 Variations in Nanjing and the Surrounding Source Analysis

To understand the transport patterns and major sources of ozone (O3) in Nanjing, this study carried out the 48-hour backward trajectories of air masses in Nanjing from March 2021 to March 2022, based on the HYSPLIT backward trajectory model driven by GDAS global reanalysis data. The primary transmission routes and putative source locations of O3 pollution in Nanjing were determined through the integration of trajectory clustering analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) analysis with meteorological data and O3 concentration data. The results showed that the high O3 concentrations and exceedance rates in Nanjing were in late spring and early summer, with the highest in June. The diurnal variation of O3 concentrations in all seasons exhibited a single peak with a maximum from 13:00 to 16:00. The southeasterly flow passing through Zhenjiang, Changzhou, Wuxi, Suzhou, and Shanghai dominated the O3 pollution in Nanjing. The PSCF and CWT presented a high consistency of O3 potential sources in Nanjing. Zhenjiang, Ma’anshan, Changzhou, Wuxi, Suzhou, and Huzhou were identified as the main potential source regions of O3 pollution in Nanjing. This study provides accurate theoretical references for regional joint prevention and control of O3 pollution in Nanjing.

Temporal Variation and Potential Sources of Water-Soluble Inorganic Ions in PM2.5 in Two Sites of Mexico City

This study presents the characterization and source apportionment of water-soluble inorganic ions (WSII), contained in particulate matter with an aerodynamic diameter equal to or less than 2.5 μm (PM2.5), performed using the positive matrix factorization model (PMF). PM2.5 were collected in Mexico City from two sites: at Merced (MER), which is a residential location with commercial activities, and at Metropolitan Autonomous University (UAM), which is located in an industrial area. The monitoring campaign was carried out across three seasons named Hot Dry (HD) (March–June), Rain (RA) (July–October), and Cold Dry (CD) (November-February). PM2.5 concentration behavior in both sites was similar, following the order: CD > HD > RA. The UAM site exhibited higher concentrations of PM2.5, of the five cations (Na+, Mg2+, Ca2+, K+ and NH4+), and of the four anions (Cl−, SO42−, NO3− and PO43−) than MER, since the UAM site is surrounded by several industrial zones. PM2.5 average concentrations for UAM and MER were 28.4 ± 11.2 and 20.7 ± 8.4 μg m−3, respectively. The ratio of cation equivalent to anion equivalent (CE/AC) showed that aerosol pH is acidic, which was confirmed by direct pH measurements. The sulfur oxidation rate (SOR) was 20 times larger than the nitrogen oxidation rate (NOR). Additionally, SO42− was the most abundant ion during the whole year, especially during the CD season with 5.13 ± 2.5 μg m−3 and 4.9 ± 3.6 μg m−3 for UAM and MER, respectively, when solar radiation displayed a high intensity. On the opposite side, the conversion of NO2 to NO3−, respectively, was low. The air mass backward trajectories were modeled using the National Oceanic and Atmospheric Administration (NOAA-HYSPLIT), which allowed us to know that differences in the mass trajectories during the days with higher concentrations were due to an effect of air recirculation, which favored PM2.5 accumulation and resuspension. On the other hand, on the days with less PM2.5, good air dispersion was observed. The main sources identified with the PMF model were secondary aerosol, vehicular, industrial crustal, and biomass burning for UAM, while for MER they were vehicular, secondary aerosol, and crustal.

Assessment of vertical characterization and potential sources of aerosols in different altitude layers: Combined application of MAX-DOAS observation and the 3D-CWT model

Vertical distribution is essential for understanding the regional transport sources of pollutants accumulated at different altitudes. We investigate aerosol extinction coefficient (AEC) profiles based on ground-based multi-Axis differential optical absorption spectroscopy measurements from August 2020 to June 2021 in Ningbo, East China. AEC vertical structures can be classified into three groups: decreasing with height (51.2%), well-mixed (2.4%), and inverse structures (46.4%), which can be explained by long-range transport, the planetary boundary layer heigh, and temperature inversion. Except in the winter, the vertical profile of the AEC typically extends to higher altitudes, which suggests the accumulation, secondary formation, or long-range transport of aerosols at higher altitudes. The three-dimensional concentration weighted trajectory (3D-CWT) model is utilized to elucidate not only altitudinal atmospheric layers in which aerosol transport occurs, but also the potential source areas of aerosols at multiple air mass arrival altitudes. The 3D-CWT model results indicate the long-range transport of aerosols, mainly through backward air mass trajectories within layers 1 (0–500 m) and 2 (500–1000 m). The potential source areas of aerosols at lower altitudes are mainly distributed in the North China Plain. At air mass arrival altitudes exceeding 600 m, the sources likely to affect aerosols in Ningbo are both land-sourced and marine-sourced (including the East China Sea, Yellow Sea, and the marginal sea between Korea and Japan) air flows. At different air mass arrival altitudes, the estimated contributions of long-range transport to aerosols are approximately 6% (200 m), 11% (600 m), and 18% (1000 m). Our findings provide a scientific basis for revealing different aerosol vertical structures and assessing long-range transport contributions in coastal urban areas.

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.

Anthropogenic and Biogenic Sources Drive the Molecular Fingerprints and Atmospheric Processing of Water‐Soluble Organic Aerosols at a Tropical Hill Station in the Western Ghats of India

AbstractThe widespread presence of organic aerosols (OA) in the atmosphere and their dominant role in climate forcing are increasingly recognized. Measurements from the high‐altitude region provide insights into the natural processes and long‐range transport of aerosols. We studied water‐soluble organic compounds in PM1.1 during January‐March 2020 and February‐April 2021 at Ponmudi (8.8°N and 77.1°E), a tropical hill station (960 m a.s.l.) located on the Western Ghats of India. The 5‐day backward trajectories of air masses presented that continental and marine sources impacted the site during the campaign, and thus we classified samples as mixed and marine air masses. Their molecular fingerprints revealed the prevalence of oxalic acid (C2), followed by terephthalic acid in mixed air mass and malonic (C3) or succinic (C4) acid in maritime air mass aerosol samples. This feature and the phthalic to azelaic acid ratio, as well as the C3 to C4 and fumaric to maleic acid ratios, evidenced that water‐soluble OA were of anthropogenic origin and less photochemically aged in mixed air mass samples, whereas they derived from biogenic sources and more photochemical aging in marine air mass samples. However, we found their comparable contributions in water‐soluble organic carbon under mixed and marine air masses. Linear correlations between C2 relative abundance and its ratios with the precursor compounds implied that the oxidation of precursors to oxalic acid occurs during atmospheric transport. The results revealed that the input of anthropogenic and biogenic precursors followed by atmospheric processing controlled the burden of water‐soluble OA across the Western Ghats.

Effects of stubble burning and firecrackers on the air quality of Delhi.

Every year at the onset of winter season (October-November), crop residue/parali/stubble burning starts in Punjab and Haryana, leading to heavy air pollution in Delhi, and adversely affecting human and environmental health. During this time, the combination of unfavourable meteorological conditions, additional emissions from stubble burning, and firework activities in this area causes the air quality to furtherdeteriorate. In this study, we have attempted to understand the influence of parali and firecracker incidents on air pollutants' variability over Delhi during the last three years (2020 to 2022). For this purpose, daily average particulate matter and gaseous pollutants data were fetched from the Central Pollution Control Board (CPCB), and daily total fire counts and fire radiative power (FRP) data were retrieved from NASA's Fire Information for Resource Management System (FIRMS). A bigger area of severe burning is suggested by higher FRP values and higher fire counts in the middle of November in all the years considered. Three years satellite-based FIRMS data over Punjab and Haryana show the highest number of active fire counts in 2021 (n = 80,505) followed by 2020 (n = 75,428), and 2022 (n = 49,194). More than 90% parali burning incidents were observed in Punjab state only despite the considerable variability in numbers among the years. The significant effect of parali burning was seen on pollutant concentration variability. As the number of fire count increases or decreases in Punjab and Haryana, there is a corresponding increase or decrease in the particulate matter concentration with a time lag of few days (1 to 2days). The trend in backward air mass trajectories suggests that the variable response time of pollutants' concentration is due to local and distant sources with different air mass speeds. Our estimates suggest that stubble burning contributes 50-75% increment in PM2.5 and 40 to 45% increase in PM10 concentration between October and November. A good positive correlation between PM2.5, PM10, NOX, and CO and fire counts (up to 0.8) suggests a strong influence of stubble burning on air quality over Delhi. Furthermore, the firecracker activities significantly increase the concentration of particulate matter with ~100% increment in PM2.5 and ~55% increment in PM10 mass concentrations for a relatively shorter period (1 to 2days).

Comparison of the Performance of the GRASP and MERRA2 Models in Reproducing Tropospheric Aerosol Layers

Two approaches, based on Generalized Retrieval of Aerosol and Surface Properties (GRASP) and Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) models, are investigated for reproducing aerosol layers in the troposphere. The GRASP algorithm is supplied with synergistic LIDAR and sunphotometer measurements to obtain aerosol extinction profiles. MERRA-2 is an atmospheric reanalysis coupling model that includes an external mixture of sea salt, dust, organic carbon, black carbon, and sulfate aerosols. A data set from Racibórz observatory, obtained with LIDAR and a sunphotometer in the 2017–2020 period, is analysed with GRASP along with the closest grid point data given by MERRA-2. The models demonstrate satisfactory agreement, yet some discrepancies were observed, indicating the presence of biases. For vertically integrated profiles, the correlation coefficient (R) between aerosol optical thickness was calculated to be 0.84, indicating a strong linear relationship. The Pearson correlation coefficient calculated between profiles for the selected altitude sectors varies between 0.428 and 0.824, indicating moderate to good agreement at all altitudes. GRASP shows denser aerosol layers in the mid-troposphere, while MERRA-2 gives higher aerosol extinctions throughout the high troposphere to low stratosphere region. Moreover, GRASP does not provide vertical variability in the extinction profile near the ground, due to a lack of data in the LIDAR’s incomplete overlap range. Lastly, the aerosol layer identification and type recognition are validated with statistical analysis of air mass backward trajectories with endpoints spatially and temporally collocated with individual identified layers. These reveal potential source regions that are located within areas known to be significant sources for the different identified aerosol types.

Preliminary discussion about the air pollution status in Afghanistan from Aerosol Optical Depth

Kabul city, the capital of Afghanistan, has suffered from poor air quality for the last two decades. This study focuses on Kabul’s spatiotemporal characteristics of aerosol optical depth (AOD). The annual and long-term 20 years of AOD data were retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) a combination of Terra and Aqua satellites using the Google Earth Engine geospatial analysis platform to determine seasonal variation and long-term trend of the aerosols. The air mass backward trajectories were calculated using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Furthermore, ArcGIS 10.7.1 is used to visualize the AOD over the city. The results show high AOD in summer. However, autumn is recorded as the lowest average AOD season. In addition, the 20 years of data from 2001 to 2021 shows a slight increase in AOD. We suggest that the increase in AOD in the city is due to the rapid growth of the population. The cross-boundary atmospheric aerosols affect the air quality in the city.

Atmospheric radioactive nuclide deposition on the coast of the Maowei Sea, northern Beibu Gulf, China

The natural radioisotopes 7Be, 210Pb, and 210Po, with different half-lives, are all particle-reactive and serve as natural tracers to study sources and transportation of sediments, sedimentation rates, and sediment chronology. Atmospheric deposition of these radioisotopes is the premise and foundation of their tracing application. The Maowei Sea is a semi-closed bay along the Beibu Gulf, which is an important gulf in the northwest of the South China Sea, but the atmospheric deposition of the abovementioned radioisotopes has not been systematically reported along the coast. In this research paper, the atmospheric depositional fluxes of 7Be, 210Pb, and 210Po were observed over a period from June 2018 to December 2021 on the coast of the Maowei Sea. The annual atmospheric depositional fluxes (Bq m-2 yr-1) of 7Be, 210Pb, and 210Po on the coast of the Maowei Sea were 496.80, 201.72, and 58.08, respectively. The distributions for 7Be and 210Pb depositional fluxes during a whole year (years 2019 and 2021) followed a bimodal pattern, with one peak from February to April and another peak from August to October, while the distribution for 210Po depositional flux showed only one peak during the year of 2019 and another during 2021. The deposition flux and activity of 7Be showed a strong positive correlation with the deposition flux and activity of 210Pb, respectively; the deposition flux and activity of 210Po also showed positive correlations with the deposition fluxes and activities of 210Pb and 7Be, respectively, indicating a similarly scavenging behavior from the atmosphere. A Pearson correlation matrix was used to illustrate the factors influencing the atmospheric depositions and found that precipitation, air quality index (AQI), and PM (both PM2.5 and PM10) were the major factors that influenced the deposition of these three radionuclides. Precipitation had significant positive correlations with the deposition fluxes of all three radionuclides, indicating that, for these radionuclides, rainfall was the main scavenging way from the atmosphere. The observations for specific single rainfall events and their air mass backward trajectory analyses showed that the air masses movement during the rainfall may be another important factor that impacted the depositional fluxes for 7Be, 210Pb, and 210Po.

Chemical Characterization and Source Apportionment of PM10 Using Receptor Models over the Himalayan Region of India

This study presents the source apportionment of coarse-mode particulate matter (PM10) extracted by 3 receptor models (PCA/APCS, UNMIX, and PMF) at semi-urban sites of the Indian Himalayan region (IHR) during August 2018–December 2019. In this study, water-soluble inorganic ionic species (WSIIS), water-soluble organic carbon (WSOC), carbon fractions (organic carbon (OC) and elemental carbon (EC)), and trace elements of PM10 were analyzed over the IHR. Nainital (62 ± 39 µg m−3) had the highest annual average mass concentration of PM10 (average ± standard deviation at 1 σ), followed by Mohal Kullu (58 ± 32 µg m−3) and Darjeeling (54 ± 18 µg m−3). The annual total ∑WSIIS concentration order was as follows: Darjeeling (14.02 ± 10.01 µg m−3) > Mohal-Kullu (13.75 ± 10.21 µg m−3) > Nainital (10.20 ± 6.30 µg m−3), contributing to 15–30% of the PM10 mass. The dominant secondary ions (NH4+, SO42−, and NO3−) suggest that the study sites were strongly influenced by anthropogenic sources from regional and long-range transport. Principal component analysis (PCA) with an absolute principal component score (APCS), UNMIX, and Positive Matrix Factorization (PMF) were used for source identification of PM10 at the study sites of the IHR. All three models showed relatively similar results of source profiles for all study sites except their source number and percentage contribution. Overall, soil dust (SD), secondary aerosols (SAs), combustion (biomass burning (BB) + fossil fuel combustion (FFC): BB+FFC), and vehicular emissions (VEs) are the major sources of PM10 identified by these models at all study sites. Air mass backward trajectories illustrated that PM10, mainly attributed to dust-related aerosols, was transported from the Thar Desert, Indo-Gangetic Plain (IGP), and northwestern region of India (i.e., Punjab and Haryana) and Afghanistan to the IHR. Transported agricultural or residual burning plumes from the IGP and nearby areas significantly contribute to the concentration of carbonaceous aerosols (CAs) at study sites.

Characteristics and Source Apportionment of Volatile Organic Compounds in Zhanjiang in Summer

Ozone pollution is intensifying in China, and its related studies are weak in non-focus regions and non-focus cities. Here, we investigated the characteristics and sources of volatile organic compounds (VOCs) at three sampling sites in Zhanjiang. We analyzed 101 VOCs using a gas chromatography-mass spectrometry/hydrogen ion flame detector (GC-MS/FID) and high-performance liquid chromatography (HPLC) using a Summa canister and DNPH adsorption tube. We calculated the ozone formation potential (OFP) of VOCs and used the positive matrix factorization (PMF) model for source apportionment. The results showed that the mean φ(TVOCs) was 1.28×10-7, and the dominant contributors were OVOCs (52%), followed by alkanes (36%), alkenes (7%), halogenated hydrocarbons (2.42%), aromatic hydrocarbons (1.61%), and alkynes (0.78%). The diurnal variation in VOCs was influenced by photochemical reactions; the ratio of aromatic hydrocarbons and alkanes was high in the morning and evening and low at noon, whereas OVOCs had a low ratio in the morning and noon and high in the evening, influenced by primary emissions and the upwind transport of pollutants. The OFP was 3.28×10-7, and the dominant species were formaldehyde, butene, n-butane, butanone, and acetaldehyde.The analysis of X/E values (characterizing the aging degree of air masses) and backward trajectories of air masses showed that during the sampling, when influenced by air masses from the south or southwest, X/E was small, and the aging degree of air masses was high, indicating the influence of regional transport; when influenced by air masses from the east or southeast direction, X/E was large, and the air masses were fresh, and VOCs were mainly from local emissions. Six emission sources of VOCs, including industrial emissions, gasoline vehicle exhaust and gasoline evaporation, regional background and transport sources, biomass combustion, diesel vehicles and marine shipping emissions, and solvent use emission sources, were resolved using the PMF model, with contributions of 36.05%, 28.99%, 13.84%, 10.13%, 7.05%, and 3.95%, respectively.Zhanjiang should strengthen the supervision of formaldehyde, butene, n-butane and butanone, industry sources, and mobile sources as the focus of control.

Genesis of New Particle Formation Events in a Semi-Urban Location in Eastern Himalayan Foothills

New particle formation (NPF) events identified using scanning mobility particle sizer (SMPS) measurements, their subsequent growth and other characteristics over Dibrugarh, a semi-urban location in the eastern Himalayan foothills (EHF), during November–December 2016 are presented. The mean total number concentration of ultrafine aerosols was found to be high during morning and evening rush hours. The NPF occurrence frequency was found to be 14%. The temporal evolution of the hourly average aerosol number size distribution revealed that the nucleation burst occurred at a lower size spectrum, supporting the existence of NPF burst events. It continued to grow through coagulation loss and condensation sink with an average growth rate of 17.16 ± 12.29 nm/hr. The satellite-based observations showed a high concentration of the NPF precursors NO2, SO2, and HCHO during the NPF days. The backward air mass trajectories confirmed that the sources of emissions were confined within an area of radius ~100 km surrounding the observation site. These locally generated precursors and their associated photochemistry could be a probable reason for NPF occurrence at the study site.

Pollen long-distance transport associated with symptoms in pollen allergics on the German Alps: An old story with a new ending?

Pollen grains are among the main causes of respiratory allergies worldwide and hence they are routinely monitored in urban environments. However, their sources can be located farther, outside cities' borders. So, the fundamental question remains as to how frequent longer-range pollen transport incidents are and if they may actually comprise high-risk allergy cases. The aim was to study the pollen exposure on a high-altitude location where only scarce vegetation exists, by biomonitoring airborne pollen and symptoms of grass pollen allergic individuals, locally.The research was carried out in 2016 in the alpine research station UFS, located at 2650 m height, on the Zugspitze Mountain in Bavaria, Germany. Airborne pollen was monitored by use of portable Hirst-type volumetric traps. As a case study, grass pollen-allergic human volunteers were registering their symptoms daily during the peak of the grass pollen season in 2016, during a 2-week stay on Zugspitze, 13–24 June. The possible origin of some pollen types was identified using back trajectory model HYSPLIT for 27 air mass backward trajectories up to 24 h.We found that episodes of high aeroallergen concentrations may occur even at such a high-altitude location. More than 1000 pollen grains m−3 of air were measured on the UFS within only 4 days. It was confirmed that the locally detected bioaerosols originated from at least Switzerland, and up to northwest France, even eastern American Continent, because of frequent long-distance transport. Such far-transported pollen may explain the observed allergic symptoms in sensitized individuals at a remarkable rate of 87 % during the study period.Long-distance transport of aeroallergens can cause allergic symptoms in sensitized individuals, as evidenced in a sparse-vegetation, low-exposure, ‘low-risk’ alpine environment. We strongly suggest that we need cross-border pollen monitoring to investigate long-distance pollen transport, as its occurrence seems both frequent and clinically relevant.

A Study of Real-Time and Satellite Data of Atmospheric Pollutants during Agricultural Crop Residue Burning at a Downwind Site in the Indo-Gangetic Plain

Crop residue burning emits a variety of air pollutants that drastically affect air quality, both locally and regionally. To study the impact of crop residue burning, in the present study, concentrations of particulate matter (PM2.5), trace gases (tropospheric ozone (O3), nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs)) were recorded in Agra, a suburban downwind site. The study was conducted during the pre-harvest (15 September to 5 October 2021) and post-harvest periods (6 October to 10 November 2021). During the post-harvest period, PM2.5 concentrations were recorded to be three to four times higher than the NAAQ Standards (35 µg/m3), while O3 and VOC concentrations showed an increment of 16% and 30.4%, respectively. NOx and CO concentrations also showed higher levels (19.7 ± 7.5 ppb and 1498.5 ± 1077.5 ppb) during this period. Moderate resolution imaging spectroradiometer (MODIS), along with air mass backward trajectory analysis (HYSPLIT Model), were used to detect fire hotspots that suggested that the enhanced pollutant levels may be due to the burning of crop residue in agricultural fields over the northwest Indo-Gangetic Plain (NW-IGP). Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX) analysis showed high K concentrations during the post-harvest period, which may be attributed to crop residue burning or biomass combustion.

Detecting local and regional air pollution from biomass burning at a suburban site

Identifying pollution plumes is challenging in cities where in situ air pollution data are scarce, monitoring stations are placed close to roadways, and the smoke from biomass burning might be of local and regional origin. This work characterizes local and regional smoke events at a suburban site in Londrina, southern Brazil, during the dry season. We measured black carbon at 370 and 800 nm (BC370 and BC880), fine particulate matter (PM2.5), particle number (PN), nitrogen oxides (NOx) and ozone (O3) concentrations with 1–2 min resolutions. Ancillary data, such as meteorological variables, aerosol optical depth (AOD) and air mass backward trajectories, aided identifying the sources. The pollution datasets were analyzed by using descriptive statistics, diurnal cycles, temporal correlations, and conditional probability functions coupled with cluster analysis of backward trajectories. Hourly mean (± standard deviation) concentrations were 1.33 ± 1.28 μg m-3 (BC370), 0.91 ± 0.84 μg m-3 (BC880), 15.90 ± 12.95 μg m-3 (PM2.5), 5691 ± 4872 cm-3 (PN), 7.23 ± 7.53 μg m-3 (NOx) and 49.77 ± 17.66 μg m-3 (O3). The prevalence of aerosols from biomass burning was indicated by Ångström exponent (Å370/880) values predominantly larger than 1 (1.51 ± 0.20). Pollutant concentrations peaked on weekend evenings and, occasionally, scattered along the day due to the short-lived open burning of residential solid waste. These events led to fast changing concentrations, increasing from 282 to 929% between consecutive 2-min measurements, reaching 69.29 μg m-3 (BC370), 456.77 μg m-3 (PM2.5) and 232,500 cm-3 (PN). Emissions from biomass-fueled boilers also contributed to deteriorate the local air quality, under favorable local winds. Three regional events advected pollution from Cerrado (tropical savanna) wildfires lasting two-three days each, and were associated with the South American Low Level Jet. During these event, the AOD reached up to 0.37 and mean PM2.5, BC370, and O3 concentrations were (2.5–3.3), (1.9–2.9) and (1.3–1.5) times higher compared to a clean period. Lowering the population exposure to biomass burning requires immediate action to control local sources, and international cooperation is needed to combat regional wildfires in a warming climate.

Cloud condensation nuclei and backward trajectories of air masses at Mt. Moussala in two months of 2016

This study presents the results about the influence of the weather elements on the Cloud Condensation Nuclei (CCN) size distribution. For this purpose the data for summer (July) and winter (December) conditions of 2016 from the highest in the Balkan Peninsula Environmental Observatory on Mt. Moussala are used for finding the extrema of the CCN concentrations. To characterize the synoptic situation we extend our study with data for the geopotential height, wind and temperature at 700 hPa for the considered two months. We use the HYSPLIT model of the National Oceanic and Atmospheric Administration to trace the backward trajectories of the air masses for the previous 72 h before their arrival at Mt. Moussala. Thus we identify two major types of trajectories, sea and continental, depending on the time spent over the corresponding surface and three groups according to the predominant height, from the lowest to the highest one. The prevailing trajectory type in the two months studied is the continental one. During most of July the air masses are coming along the high layers of the atmosphere, while in December the majority of the trajectories are coming from the lowest layers. We match these two types of trajectories with an existing synoptic classification scheme of the weather patterns over the Balkan region.

Impacts of the antartic ozone hole influence events over southern Brazil in October 2015.

The impact of the Antarctic Ozone Hole Influence over Southern Brazil in October 2015 was analyzed using daily mean data of the Total Column Ozone (TCO), Ultraviolet Index (UVI) and Radiative Cloud Fraction (RCF) from the Ozone Monitoring Instrument satellite instrument. Vertical profiles and fields of ozone content and Potential Vorticity available from the European Centre for Medium-Range Weather Forecast reanalysis, air masses backward trajectories from the HYbrid Single-Particle Lagrangian Integrated Trajectory model and channel 3 water vapor images from the Geostationary Operational Environmental Satellite GOES-13 were also analyzed. The five identified events showed an -7.4±2.3% average TCO reduction, leading to an +16.6±54.6% UVI increase even with a predominance of partly cloudy days. Other impacts were observed in the ozone profiles, where the most significant anomalies occurred from 650 K reaching 1.2 ppmv at the 850 K level. In the ozone fields at 700 K, the presence of a polar origin tongue was observed causing negatives anomalies between -0.2 and 0.4 ppmv in a transient system format forced with eastward-traveling Rossby waves passing through the Southern of Brazil and Uruguay.

2019 Southeast Asia Transboundary Haze and its Influence on Particulate Matter Variations: A Case Study in Kota Kinabalu, Sabah

<abstract><p>In 2019, Malaysia faced a deterioration of air quality due to transboundary haze, which brought negative implications, especially for public health. In light of the above scenario, continuous particulate matter (PM<sub>10</sub>, PM<sub>2.5</sub> and PM<sub>1</sub>) and meteorological parameters amid the haze period were taken to unravel the influence of haze on particulate matter variations and to investigate the association between particulate matter concentrations with meteorological parameters and fire hotspots in Kota Kinabalu, where it is rarely studied. Particulate matter and the meteorological parameters were monitored during the haze season, continuously from 21 August–30 September 2019, using AirMate, a ground-based air monitoring equipment. Air mass backward trajectories were simulated using the HYSPLIT Model, and fire hotspot data was obtained from the Greenpeace Global Fire Dashboard. The results showed increasing particulate matter concentrations during the haze period, with PM<sub>2.5</sub> exceeding the New Ambient Air Quality Standards (2020) on multiple days. For meteorological parameters, all parameters showed a significant weak positive relationship with respective particulate matter. However, the correlation between particulate matter and fire hotspots in Indonesia showed a moderate positive relationship. The backward trajectories simulated indicated the influence of south-westerly winds in transporting the pollutants from fire hotspots in the Indonesia region. Thus, we provide beneficial information about the impacted area during the 2019 transboundary haze episode, where the interactions between the particulate matter variations and the parameters studied were unraveled.</p></abstract>

Number size distribution of bacterial aerosols in terrestrial and marine airflows at a coastal site of Japan

Size-differentiated concentration of bacterial aerosols is essential for investigating their dissemination via the atmosphere. In this study, the number size distribution of bacterial aerosols was measured at a coastal site in southwestern Japan (32.324°N, 129.993°E) using a size-segregated eight-stage (>11, 7.0–11, 4.7–7.0, 3.3–4.7, 2.1–3.3, 1.1–2.1, 0.65–1.1, and 0.43–0.65μm) sampler. The results showed that the distribution differed according to the source areas: terrestrial air, oceanic air, or a combination of the two. The distribution in the long-distance transported terrestrial air from the Asian continent was monomodal, with a peak of 3.3–4.7 μm. The distribution in local land breeze air was bimodal, with the peaks at 0.43–1.1 and 3.3–4.7 μm. A similar bimodal distribution was encountered when the local island air and long-distance transported terrestrial air mixed. In contrast, the size distribution did not show clear peaks in the air from either nearby or remote marine areas. According to the air mass backward trajectories, the further the distance the air moved in the 72 h before arriving at the site, the lower the concentration of total bacterial aerosols. The estimation of dry deposition fluxes of bacterial cells showed that the deposition was dominated by cells larger than 1.1 μm with a relative contribution from 70.5 % to 93.7 %, except for the local land breeze cases, where the contributions in the size ranges larger and smaller than 1.1 μm were similar. These results show the distinctive number size distributions and removal processes of bacterial aerosols in different types of air. In addition, they indicate that size-dependent characteristics of airborne bacteria should be considered when studying their activities and roles in the atmospheric environment.