Concentration Weighted Trajectory Research Articles

Seasonality, sources apportionment, human health risks assessments, and potential implications on the atmospheric chemistry of polycyclic aromatic hydrocarbons in size-segregated aerosols from a Romanian metropolitan area.

Urbanization and industrialization are important transformations shaping the current statement of the society, enhancing significantly the combustion emissions which are threatening the global climate system, air quality, and human health. These emissions contain polycyclic aromatic hydrocarbons (PAHs) which are well known for their high toxicity. The present study is the first assessing the seasonal variation of 17 PAHs in size segregated fractions of atmospheric aerosol particles from a Romanian metropolitan area. In addition to sources apportionment and health risks, the potential role of PAHs on the atmospheric chemistry in the area was also addressed. Higher PAHs concentrations were determined in winter season, the highest values being quantified for benzo[b]fluoranthene, benzo[a]pyrene, and indeno[1,2,3-cd]pyrene. Each analyzed PAH exhibited a dominant peak in the accumulation mode (0.1-1.0 μm), with maxima at 381 nm. Gasoline combustion was identified as a significant contributor to the PAHs levels in the atmospheric aerosols from the area. Biomass-burning contributions were highlighted during the winter and autumn seasons. The positive matrix factorization (PMF) model apportioned four PAHs sources, as follows: vehicular (31%), mixed combustion (33%), biomass and wood burning (19%), and coal and natural gas combustion (18%) sources. Concentration-weighted trajectory (CWT) analysis method revealed clear contributions to PAHs abundances from local and regional air masses. Alveolar region of adults seems to have the highest susceptibility for PAHs deposition. Values exceeding acceptable limits for carcinogenic risk throughout the year are associated with benzo[a]pyrene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, benzo[a]anthracene etc. The present study can be considered as a reference in the region in order measures of mitigation and control for PAHs emission sources to be introduced.

Characterization of aerosol composition: Insights from SEM-EDX analysis and CALIPSO overpasses

The effect of atmospheric aerosols on the earth’s radiation budget is primarily through their direct effects. Understanding aerosols’ morphology and elemental composition is crucial in this context. For two years, from January 2017 to December 2018, aerosol samples (PM10) were collected on quartz filter papers using a high-volume sampler (PM10) in Chennai, a semi-urban coastal environment located at 12.81°N, 80.03°E. These filter papers were stored under ambient laboratory conditions and were subsequently subjected to ultrasonication using ethanol as the solvent to separate the aerosols from the filters. The extracted samples were then analyzed using scanning electron microscopy (SEM) for the morphology and energy dispersive X-ray analysis (EDX) for elemental composition. The EDX analysis of the samples revealed the presence of various elements such as carbon (C), oxygen (O), aluminum (Al), silicon (Si), sulfur (S), potassium (K), iron (Fe), magnesium (Mg), calcium (Ca), vanadium (V), bismuth (Bi), sodium (Na), chlorine (Cl), phosphorus (P), and technetium (Tc). High concentrations of carbon, oxygen, and aluminum–silicate particles indicated the presence of carbonaceous aerosols and wind-blown dust particles. Concentration-weighted trajectory (CWT) analysis was carried out to assess the transport pathways of aerosols in the region. CALIPSO overpasses during the study period were selected, and the Vertical Feature Mask (VFM) identifiers for different aerosol types were compared with the local experimental results. The findings show that CALIPSO possess a reasonably effective capability in detecting and characterizing the local aerosol types. CALIPSO detected Dusty marine, Clean marine, Elevated smoke and Polluted dust in the study area across all four seasons. These findings closely match the characteristics of such aerosol types obtained from SEM/EDX analysis, HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) modeling, and the Angstrom exponent derived from sunphotometer readings.

Spatiotemporal variations of atmospheric mercury at urban and suburban areas in Southern Vietnam megacity: A preliminary year-round measurement study

Atmospheric mercury (Hg) pollution studies in peninsular Southeast Asia (PSEA) are currently experiencing shortage on spatiotemporal coverage due to limited observation data. Therefore, our study provided year-round (May 2022–April 2023) atmospheric Hg data at two urban and one suburban site in Ho Chi Minh City (HCMC) Vietnam - a megacity in PSEA. Higher total gaseous Hg (TGM) levels at 2 urban sites of 2.49 ± 0.86 ng m−3 (Nguyen Van Cu) and 2.12 ± 0.49 ng m−3 (Linh Trung) were observed as compared to the suburban site of 1.76 ± 0.50 ng m−3 (Can Gio) which suggests the influence of anthropogenic Hg sources. Higher TGM concentration in October 2022–January 2023 as opposed to May 2022–September 2022 at all 3 sites reflected the influence of abrupt change in air mass origins and transport pathways in southern Vietnam. Backward trajectories (BWTs) and concentration-weighted trajectory (CWT) models further suggested East Asian outflow from northeast (NE) direction as a prominent TGM source in HCMC. Our two case studies in June and December 2022 helped to distinguish the impacts of local accumulation besides long-range atmospheric Hg transport towards TGM levels in HCMC. We also attempted to address TGM public health concerns wherein a minimal hazard quotient (HQ < 1) implied insignificant Hg health risk via inhalation pathways. Our study strives to offer crucial information to fill the Hg data gap as well as seeks to explore the impact of monsoon drives on Hg pollution in the PSEA region.

Particulate black carbon mass concentrations and the episodic source identification driven by atmospheric blocking effects in Astana, Kazakhstan

Black carbon (BC) is a component of fine particulate matter (PM2.5) that is a key contributor to adverse human health effects and climate forcing. To date, BC mass concentrations and possible sources in Kazakhstan have not been studied. Thus, understanding the temporal variations of BC for a large developing region with a complex climate is useful. In this study, measurements of fine particulate BC mass concentrations in Astana were made from June 2020 to October 2021 by measuring light absorption of PM2.5 on filters. The mean BC concentration was 2.56 ± 1.29 μg m−3 with maximum and minimum monthly mean BC concentrations being 4.56 ± 2.03 μg m−3 and 1.12 ± 0.42 μg m−3 in January 2021 and June 2020, respectively. Temporal analyses of BC, SO2, PM10, NOx, CO, meteorological and atmospheric stability parameters were performed. Aggregated pollutant ‘episodic loadings’ during the heating and non-heating periods were identified. Their relationships with blocking anticyclones and cyclones were investigated by examining the reversal of meridional gradients at 500 hPa geopotential height (GPH) maps and identifying Omega (Ω) and Rex blocking types. Astana has some of the highest BC concentrations of cities worldwide. Seasonal BC source location identification using Conditional Bivariate Probability Function (CBPF) analysis implicated combined heat and power (CHP) plant emissions as the major BC source in Astana. Significant increases in BC concentrations were observed during the cold season due to numerous sources, generally poorer atmospheric dispersion and blocking events. The Concentration Weighted Trajectory (CWT) analysis results showed that the distribution of the 75th percentile of BC during episodic periods actively controlled by blockings exceeding than the entire measurement period, which may reflect cross-border transport and adjacent countries.

Atmospheric wet and dry phosphorus deposition in Lake Erhai, China

Lake Erhai is a potentially phosphorus (P)-limited lake and its water quality may have been affected by atmospheric P deposition. However, there have been few studies on atmospheric P deposition in this lake. In this study, we established five wet deposition monitoring sites and two dry deposition monitoring sites around Lake Erhai to quantify the wet and dry deposition of total phosphorus (TP), including dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP) and particulate phosphorus (PP) from July 2022 to June 2023. Wet deposition fluxes of P species were collected by automatic rainfall collection instrument, and dry deposition fluxes were estimated using airborne concentration measurements and inferential models. The results reveal that among the different P components, DOP had the highest contribution (50%) to wet TP deposition (average all sites 12.7 ± 0.7 mg P m2/yr), followed by PP (40%) and DIP (10%). Similarly, DOP (51%) was the major contributor to dry TP deposition (average two sites 2.4 ± 0.9 mg P m2/yr), followed by DIP (35%) and PP (14%). Wet deposition dominated the annual total TP deposition (wet plus dry), accounting for approximately 83%. The key seasons for dry deposition were spring and autumn, which accounted for 64% of the annual total dry TP deposition. In comparison, wet deposition was significantly higher in the summer, accounting for 73% of the annual total wet TP deposition. The results of the potential source contribution function and concentration-weighted trajectories analysis indicate that local source emission and long-range transport from surrounding cities jointly exerted a substantial influence on aerosol P concentrations, particularly in the eastern and northwestern regions of the lake. These findings provide a comprehensive understanding of the different P components in atmospheric deposition, which is beneficial for developing effective strategies to manage the P cycle in Lake Erhai.

Day–night variation, size distribution, source identification, and health risk of polycyclic aromatic hydrocarbons in particulate matter in Ulsan, South Korea

Particulate matter (PM) in 11 different sizes was collected at a semi-rural site in Ulsan, a multi-industrial city in South Korea, over one year from 2019 to 2020 to investigate the temporal patterns in size distribution and potential sources of polycyclic aromatic hydrocarbons (PAHs). The mean concentration of Σ21 PAHs was higher in winter (0.29 and 0.45 ng/m3 for coarse and fine PM, respectively) than in summer (0.06 and 0.07 ng/m3). Although there was no statistically significant difference between day and night for the concentration of individual PAHs in both coarse and fine PM, the concentrations were generally higher during the day than at night. During the day, Σ21 PAHs had two distinct peaks (0.056–0.10 μm and 3.20–5.60 μm) in winter, but they tended to partition to larger particles (1.00–1.80 μm and >18.0 μm) in summer. This result suggests that the volatilization of PAHs in smaller particles was enhanced by high-temperature conditions in summer, followed by their condensation onto larger particles. At night, Σ21 PAH peaks were mainly around the size of 0.7 μm (droplet mode), suggesting the importance of heterogeneous-aqueous reactions. The results of the conditional bivariate probability function and concentration-weighted trajectory indicate that the high concentrations of PAHs in summer and winter were more affected by local pollution and long-range atmospheric transport, respectively. The results of the health risk assessment demonstrate that PAHs in fine PM contributed significantly to cancer risk compared to those in coarse PM. In conclusion, investigating the size distribution of PAHs in particles is necessary to understand their environmental behaviors and evaluate potential health risks.

Pollution Characteristics, Source, and Health Risk Assessment of Metal Elements in PM2.5 Between Winter and Spring in Zhengzhou

A total of 18 metal elements in ambient PM2.5 in Zhengzhou were continuously determined using an online heavy metal observation instrument in January and April, 2021, and the changes in element concentrations were analyzed. Metal elements were traced via enrichment factors, positive matrix factorization (PMF), and a characteristic radar chart. The US EPA health risk assessment model was used to assess the health risks of heavy metals, and the backward trajectory method and the concentration-weighted trajectory (CWT) method were used to evaluate the potential source regions of health risks. The results showed that the element concentrations were higher in spring, and the sum of Fe, Ca, Si, and Al concentrations accounted for 89.8% and 87.5% of the total element concentrations in winter and spring, respectively. Cd was enriched significantly, which was related to human activities. The concentrations of Pb, Se, Zn, Ni, Sb, and K in winter and Cr, Ni, Fe, Mn, V, Ba, Ca, K, Si, and Al in spring increased with the increasing pollution level. The results of PMF and the characteristic radar chart showed that the main sources of metal elements in winter and spring were industry, crust, motor vehicles, and mixed combustion, with industry and mixed combustion pollution occurring more often in winter and crust pollution occurring more often in spring. Significant non-carcinogenic risks existed in both winter and spring with more severe health risks in winter, and Mn caused significant non-carcinogenic risks. The health risks in winter were mainly influenced by Zhengzhou and surrounding cities and long-distance transport in the northwest, and the health risks in spring were mainly influenced by Zhengzhou and surrounding cities.

Exploring secondary aerosol formation associated with elemental carbon in the lower free troposphere

The variability of element carbon (EC) mixed with secondary species significantly complicates the assessment of its environmental impact, reflecting the complexity and diversity of EC-containing particles' composition and morphology during their ascent and regional transport. While the catalytic role of EC in secondary aerosol formation is recognized, the effects of heterogeneous chemistry on secondary species formation within diverse EC particle types are not thoroughly understood, particularly in the troposphere. Alpine sites offer a prime environment to explore EC properties post-transport from the ground to the free troposphere. Consequently, we conducted a comprehensive study on the genesis of secondary aerosols in EC-containing particles at Mt. Hua (altitude: 2069 m) from 1 May to 10 July, using a single particle aerosol mass spectrometer (SPAMS). Our analysis identified six major EC particle types, with EC-K, EC-SN, and EC-NaK particles accounting for 27.6 %, 27.0 %, and 19.6 % of the EC particle population, respectively. The concentration-weighted trajectory (CWT) indicated that the lower free troposphere over Mt. Hua is significantly affected by anthropogenic emissions at ground-level, predominantly from northwestern and eastern China. Atmospheric interactions are crucial in generating high sulfate levels in EC-SN and EC-OC particles (> 70 %) and notable nitrate levels in EC-K, EC-BB, and EC-Fe particles (> 80 %). The observed high chloride content in EC-OC particles (56 ± 32 %) might enhance chlorine's reactivity with organic compounds via heterogeneous reactions within the troposphere. Distinct diurnal cycles for sulfate and nitrate are mainly driven by varying transport dynamics and formation processes, showing minimal dependency on EC particle types. Enhanced nocturnal oxalate conversion in EC-Fe particles is likely due to the aqueous oxidation of precursors, with Fe-catalyzed Fenton reactions enhancing OH radical production. This investigation provides critical insights into EC's role in secondary aerosol development during its transport in the lower free troposphere.

Application of quasi-empirical orthogonal functions to estimate wildfire impacts in northwestern Spain

Galicia (NW Spain) is one of the most fire-prone regions in Southern Europe. In the summer of 2022, a total of thirteen wildfires each exceeding 500 ha were reported in this area, with ten of these large fires occurring in the Ourense region. To study the impacts of wildfire smoke plumes on ambient air PM2.5 concentrations, a network of 18 PurpleAir monitors was deployed across the Galicia region during July and August 2022. The PM2.5 concentration data were then used as input to test the applicability of quasi-empirical orthogonal functions (QEOFs obtained with Positive Matrix Factorization (PMF)) to characterize the spatial variability of wildfire smoke impacts on air quality. HYSPLIT back-trajectory analysis and Concentration-Weighted Trajectory (CWT) models were implemented, and the results from these tools were combined with source contributions. As a result, 19 wildfires were identified and linked with peak ambient PM2.5 concentrations (>300 μg/m3 of PM2.5; 1-h mean). Specifically, the Folgoso do Courel fire emerged as a significant contributor to these high concentrations and played an important role in influencing a significant number of the identified factors. Moreover, the results also suggested that emissions from fires in Portugal reached the study area, contributing additional impacts on air quality. These results demonstrated that this approach was useful in identifying the emission source areas contributing to observed PM2.5 concentrations during wildfire events. The PM2.5 concentration maps resulting from the CWT analysis were also valuable in understanding the short- and long-term exposures to PM2.5 from wildfire smoke.

Seasonal variation, source identification, and health risk assessment of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Ulsan, South Korea

Gaseous and particulate 21 PAHs were monitored at a residential site in Ulsan, South Korea, over three seasons (December 2013–August 2014). The mean concentrations of Σ21 PAHs were highest in winter (16.2 ± 8.2 ng/m3), followed by spring (8.37 ± 4.53 ng/m3) and summer (6.23 ± 2.53 ng/m3). The mean gaseous concentration of Σ21 PAHs (7.39 ± 4.39 ng/m3) was 2.7 times higher than that of particulate PAHs (2.70 ± 3.38 ng/m3). To identify the sources of PAHs (both types of sources and their areas), diagnostic ratios, principal component analysis, and concentration-weighted trajectory (CWT) were used. The results showed that pyrogenic sources (e.g., coal combustion) were the primary emission sources of PAHs in winter and spring. In summer, the influence of both coal and heavy oil combustion was dominant, suggesting that PAHs could be transported from industrial areas of Ulsan (e.g., petrochemical and nonferrous industrial complexes) by seasonal winds. Regarding emission source areas, the CWT analysis revealed that in winter and spring, PAHs in Ulsan could be attributed to emissions from regional areas, e.g., China and North Korea. The PAH concentrations were also used to assess the health risks associated with the inhalation of these compounds for adults aged 18–70. The results showed that the cancer risks from Σ19 PAHs and Σ13 PAHs did not exceed the guideline set by the US EPA (10−6), indicating no cancer risks for this target group. However, it is worth noting that certain PAHs, which are not listed as priority PAHs by the US EPA, make significant contributions to the benzo[a]pyrene equivalent and the associated cancer risks. Therefore, it is necessary to investigate not only the priority PAHs but also other PAH species to fully evaluate their effect on human health.

The effect of mixed layer across air mass trajectory pathways on PM2.5 constituent levels: The case of a major urban center in the Eastern Mediterranean

Αn advanced three dimensional (3D) version of air mass Concentration Weighted Trajectory (CWT) model was applied, coupled with Mixed Layer Depth (MLD) estimations across the trajectory pathways. Three years daily PM2.5 composition measurements from an urban background site in Athens (Greece) were incorporated in the 3D-CWT model, to identify the atmospheric circulation patterns affecting PM2.5 constituent levels during cold (October 16th to April 15th) and warm (April 16th to October 15th) periods. The recirculation of local air masses inside the Mixed Layer (ML) during the cold period, was associated with accumulation of all PM2.5 constituents emitted from combustion sources (EC, OC, SO42−, NO3−, NH4+ and K+), whilst regional contributions of the same species were mainly associated with Northern airflows above the ML through Balkan Peninsula. In the cold period, transport of sea spray (Cl−, Na+ and Mg2+) and dust (Ca2+), from the Mediterranean and the Sahara desert respectively, was detected mainly through the ML, whilst sea salt from the Black Sea and dust from Balkan Peninsula were also transferred with Northern airflows above the ML. Contrariwise, transport from the Balkans area especially above the ML enriched the levels of all constituents of anthropogenic origin during the warm period, whilst the pattern of Saharan dust advections was also vertically extended above the ML. Conclusively, the implemented 3D-CWT model revealed a more detailed description of PM2.5 transport pathways in Athens, in comparison with the classic CWT model, by including the effect of MLD across the air mass trajectories.

Influence of Transboundary Pollution on the Variability of Surface Ozone Concentrations in the Desert Southwest of the U.S.: Case Study for Arizona

Arizona, a rapidly growing state in the southwestern U.S., faces ozone pollution challenges, including nonattainment areas in Yuma and Maricopa counties influenced by neighboring state pollution transport. In this study, we use five-year (2017–2021) hourly back-trajectories and O3 concentration data for concentration-weighted trajectory (CWT) analysis to identify transport pathways and potential source regions of O3 at six monitoring sites in Arizona. We divide the data into five seasons (winter, spring, dry summer, monsoon summer, and fall) to examine variations in O3 concentration and transport across sites and seasons. The highest mean O3 concentrations occur during spring (37–49 ppb), dry summer (39–51 ppb), and monsoon summer (34–49 ppb), while winter (19–41 ppb) exhibits the lowest seasonal mean. The CWT results reveal that high O3 concentrations (≥40 ppb) in Arizona, with the exception of Phoenix and Tucson sites, are influenced significantly by regional and international transport, especially in spring (14.9–35.4%) and dry summer (12.7–26.9%). The major potential source areas (excluding the Phoenix and Tucson sites) are predominantly located outside Arizona. This study highlights the critical role of pollution transport in influencing O3 variability within Arizona and will be valuable in shaping pollution control strategies in the future.

Sources, gas-particle distribution and health risks of atmospheric PAHs in two typical basin cities in China

The sources of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of various cities are highly intricate. Conducting research on the pollution characteristics of different types of PAHs in cities will help to focus on solving air pollution problems based on urban characteristics. Polycyclic aromatic hydrocarbons (PAHs) in the PM2.5-bound state and gas-phase were analyzed in the winter atmosphere of Yuncheng and Nanyang, China, to determine their pollution and spatial characteristics. The results revealed that in Yuncheng, the average concentrations of these 16 PAHs were 129.83 ± 96.63 ng m−3 in the PM2.5-bound form and 168.05 ± 88.64 ng m−3 in the gas phase, surpassing those observed in Nanyang, where the averages were 66.53 ± 32.49 ng m−3 and 112.80 ± 65.90 ng m−3 for particulate and gas phases, respectively. Gaseous samples primarily contained low molecular weight PAHs, while medium and high molecular weight PAHs were more prevalent in particulate samples. The linear relationship between the gas-particle partition coefficient (logKP) and the gas partition coefficient (PL0) and KOA value of PAHs in both cities suggested that during winter, PAHs in Yuncheng and Nanyang predominantly adsorb onto particles, failing to achieve gas-particle equilibrium. Source analysis using positive matrix factorization (PMF) identified coal combustion (26.4%–41.9%), biomass combustion (26.3%–29.6%), motor vehicle emissions (16.3%–30.4%), and evaporation sources (15.8%–26.9%) as the primary sources of atmospheric PAHs in both cities. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) analyses indicated that pollutants originating from the northwest direction and near-earth air masses exerted a substantial influence on both cities. According to health risk assessments, both Yuncheng City and Nanyang City exhibited a certain risk of cancer due to atmospheric PAH exposure. However, the risk of cancer was higher in Yuncheng City compared to Nanyang City. The research results uncover the pollution characteristics and primary sources of polycyclic aromatic hydrocarbons (PAHs) in different types of urban air. It emphasizes the substantial contribution of local pollution sources to atmospheric PAHs and emphasizes the necessity of prioritizing control measures.

Pollution Characteristics and Source Apportionment of Black Carbon Aerosols during Spring in Beijing.

Black carbon (BC) aerosols are important for absorbing aerosols, affecting global climate change and regional air quality, and potentially harming human health. From March to May 2023, we investigated black carbon aerosol levels and air pollution in Beijing. Employing methods such as linear regression, Potential Source Contribution Function (PSCF) and Concentration-Weighted Trajectory (CWT), we analyzed the characteristics and sources of black carbon aerosols in the region. Results indicate that the light absorption coefficients of BC and BrC decrease with increasing wavelength, with BrC accounting for less than 40% at 370 nm. Daily variations in BC and PM2.5 concentrations exhibit similar trends, peaking in March, and BC displays a distinct bimodal hourly concentration structure during this period. Aethalometer model results suggest that liquid fuel combustion contributes significantly to black carbon (1.08 ± 0.71 μg·m-3), surpassing the contribution from solid fuel combustion (0.31 ± 0.2 μg·m-3). Furthermore, the significant positive correlation between BC and CO suggests that BC emissions in Beijing predominantly result from liquid fuel combustion. Potential source area analysis indicates that air masses of spring in Beijing mainly originate from the northwest (40.93%), while potential source areas for BC are predominantly distributed in the Beijing-Tianjin-Hebei region, as well as parts of the Shandong, Shanxi and Henan provinces. Moreover, this study reveals that dust processes during spring in Beijing have a limited impact on black carbon concentrations. This study's findings support controlling pollution in Beijing and improving regional air quality.

Light absorption properties and source contributions of black and brown carbon in Guangxi, southern China

Black carbon (BC) and brown carbon aerosols (BrC) are primary light-absorbing carbonaceous aerosols that significantly influence the global and regional radiation balance, as well as air quality. Guangxi Zhuang Autonomous Region, as a primarily agricultural province of China and neighbouring Southeast Asia, is subjected to both local emissions and pollution transport from Southeast Asian biomass burning. To investigate the light absorption properties and source contributions of BC and BrC in this region, observations from a 7-wavelength Aethalometer are employed to estimate the light absorption properties of BC and BrC over the period from March to December 2020 in Nanning, China. This study focuses on analysing the absorption contributions of BC and BrC to the total absorption of carbonaceous aerosols, identifying their emission sources, and exploring the impact of long-range transport of biomass burning (BB) from Southeast Asia on BC and BrC based on backward trajectory and weighted concentration-weighted trajectories (WCWT) model. Our results show that the absorption Ångström exponent (AAE) of light-absorbing carbonaceous aerosols varies from 0.54 to 2.08, reflecting the presence of different absorbing aerosol sources with specific optical properties. The average absorption coefficients of BC and BrC at 370 nm, denoted as babs,BC(370) and babs,BrC(370), are 42.25 Mm−1 and 9.63 Mm−1, respectively, with the highest value observed in winter. The average absorption of BrC contributes 19% to the total absorption from light-absorbing carbonaceous aerosols, and this contribution decreases for high babs,BrC(370) values, with the highest value in summer at 20%. For the BC source apportionment using a site-specific AAE, fossil fuel combustion (FF) contributes 57%, with its highest proportion in summer (62%). Meanwhile, biomass burning (BB) accounts for 43%, with the greatest contribution in winter (58%). These results highlight the considerable role of BB in Guangxi. In terms of the BrC sources, secondary BrC (BrCsec) is responsible for 32% of the total light absorption of BrC at 370 nm, and is particularly characterized by a much higher level of 35% at night, meaning the dominant role of BrCsec in Nanning. The relative contribution of babs,BrC,sec(370) increases with a higher contribution of babs,BrC(370) to aerosol absorption. Compared with the BrCsec, primary BrC values are higher in spring and winter, due to the increased emissions from biomass burning. Based on the analysis of backward trajectory and WCWT, the increase in BC and BrC during March and April is mainly influenced by the long-range transport of BB from Southeast Asian countries, e.g., Laos and Thailand. Overall, the contributions of BB and FF emissions to BC are comparable in Guangxi, while BrC mainly formed from primary sources is significantly impacted by both local emissions and the long-range transport of BB. Studying the optical characteristics and emission sources in this region can promote the understanding of the radiative effect of light-absorbing carbonaceous aerosols under the joint contributions from biomass burning and industrial emissions.

Investigating sources and health risk assessment of n-alkanes in atmospheric wet deposition in Indo-Gangetic Plain

The present study determines the levels of n-alkanes in atmospheric wet deposition at an urban site in the Indo-Gangetic Plain, Delhi, during monsoon and non-monsoon periods in 2021. The n-alkane homologs (C10–C33) were determined in wet deposition, which included wet-only and bulk samples. The average total n-alkanes were found to be 56.0 ± 16.7 and 439.4 ± 150.8 μg/L in wet-only samples, whereas, 149.6 ± 46.4 and 454.9 ± 108.4 μg/L in bulk samples during monsoon and non-monsoon periods, respectively. The low molecular weight n-alkanes (C10–C25) exhibited no odd-even predominance in wet-only and bulk depositions during monsoon and non-monsoon periods. However, the high molecular weight n-alkanes (>C25) showed odd-even predominance during the non-monsoon period. The molecular distribution patterns of n-alkanes indicated possible emissions from bacteria, fossil-fuel combustion, direct volatilization of unburnt fuels, biogenic sources, and other anthropogenic activities. A health risk assessment for n-alkanes revealed the higher susceptibility of children via dermal and oral exposure. The Hazard Index for the exposure of n-alkanes through atmospheric wet deposition was <1, i.e., within the acceptable limit. The Carbon Preference Index (CPI) and wax n-alkanes (WNA)%, supported the prevalence of mixed emission sources with higher contributions from anthropogenic activities. Five sources of n-alkanes were identified using the positive matrix factorization (PMF) model, i.e., gasoline vehicles + fuel evaporation, biogenic, biogenic + diesel exhaust, road dust, and mixed, contributing ∼30 %, 11 %, 26 %, 17 %, and 16 % respectively. The Concentration Weighted Trajectory (CWT) analysis revealed that n-alkanes in wet-only and bulk samples were contributed by different local, regional, and long-range transport of air pollutants.

Source apportionment of atmospheric ammonia in suburban Beijing revealed through 15N-stable isotopes

Addressing the urgent issue of atmospheric ammonia (NH3) emissions is crucial in combating poor air quality in megacities. Previous research has highlighted the significant contribution of nonagricultural sources, particularly fossil fuel emissions, to urban NH3 levels. However, there is limited assessment of NH3 dynamics in suburban areas. This study focuses on four suburban sites in Beijing, covering a 16 to 22-month observation period, to investigate spatial and temporal patterns of NH3 concentrations. The δ15N-stable isotope method is employed to identify NH3 sources and their contributions. Our results demonstrate that agricultural sources (53 %) dominate atmospheric NH3 emissions in suburban areas of Beijing, surpassing nonagricultural sources, and primarily emanate from local sources. Notably, fertilizer application (37 ± 11 %) and livestock breeding (32 ± 6 %) emerge as the primary contributors in summer and spring, respectively, leading to significantly elevated NH3 concentrations during these seasons. Even in autumn and winter, both agricultural (49 %) and nonagricultural (51 %) sources contribute almost equally to NH3 emissions. This study emphasizes the need for coordinated efforts to control atmospheric NH3 pollution in Beijing City, with particular attention to addressing both vehicular and agricultural emissions.

Overview of the Trajectory-Ensemble Potential Source Apportionment Web (TraPSA-Web) Toolkit for Atmospheric Pollutant Source Identification

Trajectory ensemble receptor models (TERMs) were widely used to determine the likely source locations and apportionment of air pollutants. This paper describes the development and applications of the Trajectory-ensemble Potential Source Apportionment Web application (TraPSA-Web), a comprehensive toolkit for likely atmospheric pollutant source location apportionments using TERMs and back trajectories generated with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The TERMs integrated within the TraPSA-web include Concentration Field Analysis (CFA), Concentration Weighted Trajectory (CWT), single-site and multiple-site Potential Source Contribution Function (PSCF), and Simplified Quantitative Transport Bias Analysis (SQBA). TraPSA-Web is designed as a web application with a user-friendly modern graphical user interface (GUI), which largely enhances the accessibility to the users. TraPSA-Web will provide the air quality research community with a sophisticated toolkit for (1) easy management of the research project and datasets, (2) efficient automatization for HYSPLIT configurations, calculations, and result aggregations, (3) flexible configurations for the research scenarios and TERM parameters, and (4) interactive visualizations for the pollutant pattern analysis and TERM result mapping.

Characteristics and Source Apportionment of Carbonaceous Aerosols in the Typical Urban Areas in Chongqing During Winter

To investigate the characteristics, source apportionment, and potential source areas of carbonaceous aerosols in Chongqing during winter, PM2.5 samples were collected from January 2021 to February 2021 in the urban areas of Wanzhou (WZ), Yubei (YB), and Shuangqiao (SQ). The results showed that the average mass concentrations of PM2.5, OC, and EC in SQ were (72.6 ±33.3), (18.2 ±8.2), and (4.4 ±1.7) μg·m-3, respectively, higher than those in WZ[(67.2 ±30.3), (17.2 ±7.4), and (5.1 ±2.4) μg·m-3] and YB[(63.4 ±25.7), (15.4 ±6.3), and (4.2 ±1.9) μg·m-3]. Compared with that during the clear period, the concentration and fraction of EC in total carbon increased by 103.0% and 8.1%, respectively, in WZ compared to that in other areas during pollution period, whereas the OC/EC ratio was decreased significantly (-10.5%), indicating that the primary emission of carbonaceous aerosols increased significantly during the pollution period. The average mass concentrations of secondary organic carbon (SOC) in SQ and YB were (7.7 ±4.8) μg·m-3 and (6.9 ±2.8) μg·m-3 significantly higher, respectively, than that in WZ[(4.5 ±1.9) μg·m-3] during the campaign. This indicated that the secondary transformation had a greater influence on the carbonaceous aerosols in SQ and YB than that in WZ. Furthermore, in contrast to that in WZ, the ratios of SOC/OC were increased with the increase in PM2.5 concentrations, and significant correlations between SOC concentration and aerosol water content, NO2 concentration, and the value of NOR were observed in SQ and YB (P &lt; 0.01), indicating that the increasing of carbonaceous aerosol concentrations might be mainly driven by the SOC with -NO2 groups produced by aqueous chemical reactions during winter in SQ and YB. The positive definite matrix factor (PMF) results in these urban areas showed that the contribution of biomass/coal combustion source in WZ (47.4%) was significantly higher than that in YB (34.2%) and SQ (38.1%), whereas the gasoline motor vehicle emission and secondary transformation impacts were more significant in YB. The results of the concentration weighted trajectory (CWT) showed that the potential sources of carbonaceous aerosols were mainly the local and northeastern parts of these urban areas (such as Changshou).

Source apportionment of ambient PM2.5 in Ho Chi Minh City, Vietnam

The emission sources of fine particulate matter (PM2.5) have not yet been fully identified in Ho Chi Minh City (HCMC), Vietnam, presenting difficulties to authorities in controlling air pollution efficiently. To address this issue, this study explores the source apportionment of PM2.5 by the positive matrix factorization (PMF) model and identifies potential regional sources through the weighted concentration-weighted trajectory (WCWT) model based on the field observation data of PM2.5 in HCMC. 24-h PM2.5 samples were collected in central HCMC for a year (September 2019–August 2020). Herein, inductively coupled plasma mass spectroscopy was used to analyze trace elements, in addition to identifying PM2.5 mass and other chemical species, such as water-soluble ions and carbonaceous species, reported in our former study. The PMF results showed that PM2.5 in HCMC was dominated by anthropogenic-rich sources comprising biomass burning, coal combustion, transportation, and crustal origins (36.4% of PM2.5 mass), followed by secondary ammonium sulfate (18.4%), sea salt (13.7%), road dust (9.6%), and coal and crude oil combustion (9.4%). WCWT results suggested that the geological sources of PM2.5 were mainly from local areas and scattered to the northeast/southwest of HCMC. In addition, the long-range transport of PM2.5 from surrounding countries was revealed during the assembly restriction and lockdown period in 2020.Graphical