Aerosol acidity is found to exert negative effects on ecosystem diversity and architectural appearance. Current analytical technology is unable to measure in-situ aerosol acidity (i.e., pH value) of ambient fine particle due to the absence of appropriate pH electrodes. Thermodynamic modeling methods including ISORROPIA II and Extended Aerosol Inorganics Model Version IV (E-AIM V) are mostly used in the estimation of in-situ aerosol acidity with the inputs of water soluble ions worldwide. This study proposes a flexible method with the aid of multilayer perceptron (MLP) neural network analysis to estimate in-situ aerosol acidity of ambient fine particle (< 2.5 μm in aerodynamic diameter or PM2.5) with the inputs of water soluble ions (i.e., Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+), gaseous air pollutants (i.e., CO, NO2, SO2) and meteorological parameters (i.e., humidity and temperature). The dataset consists of ambient fine particles collected across four individual sampling periods in the autumn and winter of 2019 and 2020 at a suburban site of Nanjing. The pH values of ambient fine particle were found to be ranging from 2.0 to 4.0 estimated by E-AIM model. Levels of pH estimated by MLP neural network analysis agreed well with pH values estimated by E-AIM model with R2 value of 0.98.

At the pandemic of COVID-19, the movement of business and other non-essential activities were majorly restricted at the end of March 2020 in India and continued in different lockdown phases until June 2020. By categorically, studying sensitivity towards anthropogenic factors with other environmental implications in urban Indian cities during phase-wise lockdown scenarios will pave the way for a refined Clean Air Programme (CAP). In this study, the aerosol particulate matter variations between the lockdown phases in both spatial and temporal scales have been explored along with cities exceeding national ambient air quality (NAAQ) standards covering different geographical regions of India for their air quality level. The results of the spatial pattern of Copernicus Atmosphere Monitoring System (CAMS) near-real-time data showed a negative change both in Aerosol Optical Depth (AOD) (-0.2 to 0.1) and black carbon AOD (bcAOD) (-0.9 to -0.75). The changes were evident in successive phases of lockdown with an overall AOD reduction of about 70–90%. Southern urban cities showed a significant impact of mobile sources from temporal analysis than other cities. Principal Component Analysis (PCA) for effects of pollutants by anthropogenic factors (mobile and point source) and meteorological factors (wind speed, wind direction, solar radiation, relative humidity) revealed the two significant driving factors. PM reduction was about 50–70%, predominantly due to anthropogenic factors. The factor analysis revealed the influence of meteorological factors between the major urban cities (Delhi, Kolkata, Mumbai, Chennai, Bengaluru, and Hyderabad). Cities that exceed NAAQ standard performed well during phase-wise lockdowns, exceptional to cities in Gangetic plain. This study helps to frame region-specific strategic action plans for the CAP.

This study aimed to calculate size-fractionated PM-bound metals concentration (Co, V, Ni, Cu, Mn, As, Cd, Pb, Cr and Hg) in a European hot spot area in terms of PM air pollution (Zabrze, Poland) and to show their deposition ratios in human airways. Additionally, meteorological data was used to conclude the probable influence of atmospheric conditions on the variability of the PM mass concentrations in different periods of the year. Data regarding the elemental composition of size-fractionated PM in various regions of Poland was also presented. The determination of the selected metals in PM-fractionated samples (PM1, PM2.5, and PM10) was performed in two periods – the heating and non-heating season. It was found that metals were primarily associated with particles less than 1 µm, however, the PM size distribution had shown bi-modal characteristics and the maxima of metal mass distribution occurred in both submicron and fine modes. High PM1 mass loadings, observed especially in the non-heating season were probably due to an influx of fine and even smaller particles from traffic sources. Metals distributions as well as respiratory deposition ratios for PM-bound elements calculated using the MPPD V2.11 model favored nasal and head deposition. The overall mass deposition of metals in the respiratory tract of adults was: 0.39 (Head region, H); 0.07 (Tracheobronchial region, TB); 0.16 (Pulmonary region, P) respectively. No matter the season, the highest inhalable concentrations of metals were found for Cu, Mn, Cr and Pb. Only Cr and Pb are classified as carcinogenic and mutagenic (according to IARC classification).

Black carbon (BC) along with PM2.5 (fine particular matters) plays an important role in the assessment health effect of human beings. Winter season campaign measurements carried out for BC concentrations by using 7 different wavelengths such as 370, 470, 520, 590, 660, 880, and 950 nm, handy aethalometer (AE-33, Magee Scientific, USA), at two different locations i.e., National Institute of Technology, Jamshedpur (NIT J) and Sakchi, Jamshedpur (SAK J), in eastern India. During the study period, the mass concentration of BC varies from 4.19 µgm−3 to 15.36 µgm−3, with an average mean of 8.88 ± 2.40 µgm−3 in NIT J and SAK J, the mass concentration of BC varies from 6.3 µgm−3 to 13.48 µgm−3, with an average mean of 10.29 ± 1.58 µgm−3. However, the concentration of PM2.5 varies from 102.98 µgm−3to 198.21 µgm−3, with an average mean of 155.82 ± 29.98 µgm−3 in NIT J and SAK J, the concentration of PM2.5 varies from 110.83 µgm−3 to 207.65 µgm−3, with an average mean of 169.14 ± 22.40 µgm−3. It was reported that SAK J has a higher BC concentration compared to NIT J. This was due to heavy traffic load and dense population in SAK J. Backward Trajectories were seen that the airborne particulate matter came from differerajeshnt directions. According to the diagnostic ratio analysis of BC, it was observed that most of the BC mass concentrations come from fossil-fuel (69.70%) followed by wood-burning (30.30%) in a particular place. The overall health risk assessment of BC concentration observed during the study period was 26.70, 13.95, 24.95 and 51.32 at NIT J as well as 32.07, 16.72, 29.95 and 61.87 at SAK J, the passive cigarettes comparable concerning the risk of CVM, LC, LBW, and PLEDSC, respectively.

We introduce the CMC based Ionic Surfactant Activity model (CISA) to calculate activity coefficients in ternary aqueous solutions of an ionic surfactant and an inorganic salt. The surfactant can be either anionic or cationic and in the present development, the surfactant and inorganic salts share a common counterion. CISA incorporates micellization into the Pitzer–Debye–Hückel (PDH) framework for activities of mixed electrolyte solutions. To reduce computing requirements, a parametrization of the critical micelle concentration (CMC) is used to estimate the degree of micellization instead of explicit equilibrium calculations. For both binary and ternary systems, CISA only requires binary experimentally-based parameters to describe water–ion interactions and temperature–composition dependency of the CMC. The CISA model is intended in particular for atmospheric applications, where higher-order solution interaction parameters are typically not constrained by experiments and the description must be reliable across a wide range of compositions. We evaluate the model against experimental activity data for binary aqueous solutions of ionic surfactants sodium octanoate and sodium decanoate, as common components of atmospheric aerosols, and sodium dodecylsulfate, the most commonly used model compound for atmospheric surfactants. Capabilities of the CISA model to describe ternary systems are tested for the water–sodium decanoate–sodium chloride system, a common surrogate for marine background cloud condensation nuclei and to our knowledge the only atmospherically relevant system for which ternary activity data is available. For these systems, CISA is able to provide continuous predictions of activity coefficients both below and above CMC and in all cases gives an improved description of the water activity above the CMC, compared to the alternative model of Burchfield and Wolley [J. Phys. Chem., 88(10), 2149–2155 (1984)]. The water activity is a key parameter governing the formation and equilibrium growth of cloud droplets. The CISA model can be extended from the current form to include the effect of other inorganic salts with the existing database of binary PDH parameters and using appropriate mixing rules to account for ion specificity in the micellization process.

The data of 17 air quality monitoring stations of Greater Cairo are used to perform a statistical analysis aiming to detect any heterogeneous surface effects of mineral dust on the distribution of reactive trace gases (SO2 NO2, and ozone) in. After a thorough quality check, the methodology consisted of i) selecting representative stations by agglomerative hierarchical clustering, ii) identifying dust events based on PM10 measurements, remote sensing observations, and meteorology, and iii) applying the non-parametric Kruskal Wallis (KW) hypothesis test to compare (at the 95% confidence level) trace gas concentrations during dust and non-dust events. The representative stations display either a background-like or a bimodal variability with concentrations (even that of the secondary product NO2) peaking at traffic rush hours but during dust storms all stations capture the signal of mineral dust advection. Eight wintertime and springtime dust cases are retained for the study. After the role of the confounding factors (i.e., ventilation index, relative humidity, and photolysis) has been carefully discussed and taken into account, the KW test shows that there is no significant reduction of the SO2, NO2 and ozone concentrations attributable to dust during 7 of the 8 events. The drop of the concentrations coinciding with the advection of dry dust-laden Saharan air masses is rather an effect of the dilution resulting from the combination of large wind speed and mixing layer height than of the heterogeneous uptake of these gases on the mineral dust surface.

This study investigates chemical composition of rainwater (RW) and its contribution from different sources collected over the period of two years (2016 and 2017) at a high altitude location (1380 m above mean sea level) located at Mahabaleshwar situated in the Western Ghats in Peninsular India. The volume weighted mean pH of RW was found to vary between 4.57 and 7.51 (average 5.95) indicating overall alkaline nature of the RW. Prominent ionic species in the RW were Ca 2+ (25%), Na + (19%), Cl − (23%), SO 4 2− (10%), and Mg 2+ (9%) with NH 4 + , NO 3 − and K + together forming about 8% of ionic composition. Moreover, ample presence of dust source (Ca 2+ ) was found that acted as a major neutraliser to the acidic ions. The order of Neutralisation Factor of ions was Ca 2+ > Mg 2+ > NH 4 + . In addition, a strong correlation between Na + and Cl − (r ≈ 0.99) further suggested substantial supplement of marine (NaCl) component to the RW. The impact of local anthropogenic activities such as fossil fuel/biomass burning was observed apart from some contribution from the long-range transport. The high contribution of non-sea salt fractions to Ca 2+ , SO 4 2− , Mg 2+ and K + showed a substantial effect of crustal and continental air masses. Results of source apportionment for the RW composition by using the Positive Matrix Factorization technique indicated four factors i.e. Marine and long range transport (Na + , Cl − ), crustal (Ca 2+ , Mg 2+ ), emissions from the fossil fuel and biomass burning (NO 3 − , SO 4 2− ) and the agriculture/farming activities (NH 4 + ).

Particulate-bound Polycyclic Aromatic Hydrocarbons (PAHs) have been identified as pollutants of serious concern due to their severe health impacts on human and animal life. In the present work, 16 USEPA (United States Environmental Protection Agency) identified PAHs present in PM2.5 at Jorhat, India during the winter months (Jan-March, 2020) were analyzed. Apart from the temporal variability of these compounds, the impact of varying meteorological factors like temperature, wind speed, relative humidity, and planetary boundary layer height on PAHs concentration have also been studied. It has been observed that the effect of ambient air temperature and planetary boundary layer on PAHs concentration are significant compared to other meteorological parameters during the winter season. The average concentration of total PAHs during this period was 157.2 ± 127.7 ng/m3 with dominance of high molecular weight aromatics compared to the low molecular weight ones. Among all 16 PAHs studied, the contribution of benzo(b,j)fluoranthene (27.26%) to total PAHs concentration was found to be the highest followed by di-benzo(a,h)anthracene (10.37%). Source identification analysis using isomeric PAHs ratios indicated that crop residue burning, vehicular emission, coal, and wood combustion are the major emission sources of PAHs. A comparative study of PAHs emission at the present site with other northern cities of India has been performed and it is observed that vehicular emission contributing to PAHs is common to all cities but in Kolkata, wood and coal combustion were also responsible for PAHs emission. Biomass burning is also seen to be a contributor to Amritsar. Whereas in Jorhat, crop residue and coal/wood combustion are seen to be major contributors to PM2.5 bound PAHs unlike other cities.Graphical abstract

Analysis of rainwater in historical cities plays a key role to save ancient monuments from atmospheric agents. In this study we sampled the Rome’s rainwater from February to July of 2018 and we analysed them to determine their chemical and physical parameters: pH, redox potential, conductivity, temperature, and the concentration of the main inorganic ions (Na+, K+, Ca++, Mg++, F−, Cl−, NO3−, SO4−−). The volume of the daily fallen rainwater, the speed and direction of the wind in the sampling site were also collected. In order to find a correlation between all the above data we used the Principal Component Analysis (PCA). Results evidenced that there aren’t authentic “acid rains” as the minimum pH value that we found is 5.2. In some cases high concentrations of nitrates and sulphates were found with maximum values of 12.4 ppm and 18.7 ppm respectively. We also found no correlation between the rainwater’s composition and the seasonal period; on the contrary, the speed and direction of the wind, especially when coming from the sea or industrial country near Rome, play a noticeable role on the rainwater composition. Graphical abstract Graphical abstract

A total of 30 precipitation samples were collected at a remote site of Qinghai Lake in the northeastern Tibetan Plateau, China, from June to August 2010. All samples were analyzed for major cations (NH4+, Na+, K+, Ca2+, and Mg2+) and anions (F−, Cl−, NO3−, and SO42−), electric conductivity (EC), pH, dissolved organic carbon (DOC), and oxygen isotopic composition (δ18O). The volume-weighted mean (VWM) values of pH and EC in the precipitation samples were 7.2 and 19.0 μs cm−1. Ca2+ was the dominant cation in precipitation with a VWM of 116.9 μeq L−1 (1.6–662.9 μeq L−1), accounting for 45.7% of total ions in precipitation. SO42− was the predominant anion with a VWM of 32.7 μeq L−1, accounting for 47.1% of the total anions. The average precipitation DOC was 1.4 mg L−1, and it shows a roughly negative power function with the precipitation amount. The values of δ18O in the rainwater in Qinghai Lake varied from −13.5‰ to −3.9‰ with an average of −8.1‰. The enrichment factor analysis indicates that crustal materials from continental dust were the major sources for Ca2+ in the precipitation samples. The high concentration of Ca2+ in the atmosphere played an important role in neutralizing the acidity of rainwater in Qinghai Lake area. Cluster analysis of air-mass trajectories indicates that the air masses associated with northeast and east had high values of NH4+, SO42−, and NO3−, whereas large Ca2+ loading was related to the air mass from west.

The study analysed spatio-temporal distribution of fire radiative power (FRP) and estimates of trace gases [volatile organic compounds (VOCs) and nitrogen oxides (NO x )] along with their reactivity during biomass burning period of March (2003–2017) over the northeast region (NER), India. Reanalysis data of FRP along with emission rates of trace gases have been retrieved from Global Fire Assimilation System. Results showed that average FRP was estimated to be 0.37 Wm −2 with the highest value in Mizoram (0.16 Wm −2 ) among 7-states of the study region. Temporally, relatively higher FRP occurred during the year of 2006 and 2010 while lowest in 2017. FRP-based VOCs and NO x emission estimates were 431 and 69.5 mg/m 2 /day, respectively which are consistent with observed FRP. Among different groups of VOCs, oxygenated species were the largest group (~56%) estimated followed by alkenes, alkanes, aromatics, and biogenic. Photochemical reactivities of VOCs were estimated using propylene-equivalent and maximum incremental reactivity methods which showed oxygenated species had the highest contributions in chemical reactivity. Based on the MIR scale, the top ten leading contributor species for ozone (O 3 ) formation were in descending order of formaldehyde, acetaldehyde, ethene, propene, toluene, butane, isoprene, methanol, pentene, and hexane which accounted for approximately 97% of total ozone formation. We also examined the ozone formation regime using VOCs/NO x ratios which indicated that O3 formation was likely to be VOC-sensitive over NER. Our results could be used for the understanding of FRP-based trace gas emissions during biomass burning and to establish effective preventive measures for reduction in O 3 pollution.

Optical properties of atmospheric particles at Mexico City (UNAM) and Queretaro (JQRO) were measured with a Photoacoustic Extinctiometer (PAX) at 870 nm. The Mexico City Metropolitan Area has around 21 million inhabitants and Queretaro Metropolitan Area has little more than a million. Observations of meteorological parameters (relative humidity, solar radiation, and wind speed) were used to identify the rainy and dry seasons and explain the daily and seasonal behaviors of particles optical properties. The measurements were made from November 1, 2014 to July 31, 2016. At UNAM, the mean values of the scattering coefficient (Bscat) in cold dry, warm dry, and rainy seasons were 35.8, 27.1, and 31.3 Mm−1, respectively; while at JQRO were 10.9, 11.9, and 15.0 Mm−1. The average values of the absorption coefficient (Babs) at UNAM during the cold dry, warm dry, and rainy seasons were 14.5, 12.7, and 12.7 Mm−1, respectively; whereas at JQRO were 4.9, 4.7, and 3.9 Mm−1. Both absorption and scattering coefficients showed similar diurnal behaviors, but at UNAM they are three times higher than JQRO. Concentrations of criteria gases (O3, NO, NO2 and NOx) were also measured. At UNAM no difference was observed between the seasonal values for the single scattering albedo (SSA); while in JQRO, the rainy season had the highest seasonal value, being 13% higher than in the dry seasons. The Mass Scattering Cross-Section (MSC) values at UNAM were close to 2 m2/g; on the other hand, at JQRO the MSC values were lower than 1 m2/g. The results suggest a seasonal variability in the aerosol optical properties in both sites, which should be verified with more long-term studies.

Particle morphology and elemental compositions are among the crucial parameters of aerosols required for accurate understanding of the climatic effect of aerosols in the earth-atmosphere system; yet their vertical distributions and region specific properties are poorly characterised due to sparse in-situ measurements. This is the first study to classify and quantify the vertical distributions of the morphological characteristics and elemental composition of aerosols based on single particle as well as bulk chemical analysis over seven geographically diverse regions of northern and central parts of India during spring (April–May, 2013), carried out as a part of Regional Aerosol Warming Experiment (RAWEX). Significant regional distinctiveness in shapes (non-sphericity), sizes and elemental compositions of the airborne particles were conspicuous, having dominance of highly irregular granular aggregates over the north Indian sites. The non-spherical coarse mode particles dominated the lower free tropospheric regions (> 2 km) of the Indo-Gangetic Plains (IGP). These particles could be responsible for enhanced spring time aerosol absorption in the elevated region of the atmosphere. Elemental compositions of the single particle analysis indicate that the free tropospheric layer over the IGP and central India is enriched with Na and Ca compounds mixed with Fe or Al (soil particles), indicating long range transport of crustal aerosols. This finding is very well supported by the bulk particle analysis indicating abundance of Ca2+ in the free troposphere with low contribution of ssNa+. Particles with irregular rough surfaces having dominance of SiO2 were observed over all the study sites. The percentage share of spherical (either smooth or rough) particles to the total morphological characteristics of the particles was found to be highly subdued (< 10%). The present study thus critically assesses the relevant knowledge pertaining to the morphological features of aerosols over the IGP during spring for the accurate estimation of aerosol radiative properties. More such efforts are required in future to study the connections and dependencies between morphological and radiative properties of aerosols in different seasons.

Particulate matter (PM) can affect climate, air quality, human health, acid deposition and visibility, and contain a significant fraction of organic (OC) and elemental carbon (EC). Southern Africa is an important source region for OC and EC, however, little OC and EC data have been published for this region. This paper presents a multi-year, multi-site (an urban-industrial site in the Vaal Triangle, UI-VT; an industrially influenced site at Amerfoort, iI-AF; and two regional background sites at Skukuza and Louis Trichardt, RR-SK and RR-LT) PM with an aerodynamic diameter ≤ 2.5 μm (PM2.5) OC and EC dataset for South Africa. The median OC (9.3) and EC (3.2 μg.m−3) concentrations at UI-VT were 1.3 to 2.5 and 2.7 to 4.4 times higher, if compared to the other sites. OC/EC ratios indicated that sources in close proximity to UI-VT were likely the main contributors, while sources that are more distant contributed fractionally more at the other sites. Household combustion for space heating and regional open biomass burning contributed to elevated levels during the cold and dry months at UI-VT. Regional open biomass burning also lead to higher OC and EC concentrations during the dry season at the industrially influenced site (iI-AF) and one of the regional background sites (RR-SK). From the seasonal concentration patterns, it seemed as if household combustion for space heating also contributed at these two sites during the cold months, but this could not be proven, even if only samples with limited influence of open biomass burning were considered. Such biomass burning influences were semi-quantified by considering MODIS fire pixels occurring within the air mass fetch region for each sample. For the remaining regional background site (RR-LT) the results suggesed that only regional open biomass burning contributed to elevated levels of OC and EC in the dry season and that household combustion for space heating did not contribute significantly.

The forests of the boreal and mid-latitude zones of the Northern Hemisphere are the largest source of reactive volatile organic compounds (VOCs), which have an important impact on the processes occurring in the atmospheric boundary layer. However, the composition of biogenic emissions from them remains incompletely characterized, as evidenced by the significant excess OH radical concentrations predicted by models in comparison with those observed under the forest canopy. The missing OH sink in the models may be related to the fact that they do not take into account the emission of highly reactive VOCs by vegetation on the forest floor. In this work, we report the results of laboratory determinations of the composition of VOCs emitted by representatives of different groups of plants that form the living soil cover (LSC) in the forests of the boreal and mid-latitude zones: bryophytes, small shrubs, herbaceous plants, and ferns. In the chromatograms of volatile emissions of all 11 studied plant species, 254 compounds with carbon atoms ranging in number from two to 20 were registered. All plants were characterized by the emission of terpenes, accounting for 112 compounds, and the second largest group (35 substances) was formed by carbonyl compounds. Both groups of compounds are characterized by high reactivity and are easily included in the processes of gas-phase oxidation with the participation of radicals HO, NO3 and ozone. These data indicate the importance of a thorough study of the so far disregarded source of VOCs, that is, the LSC in forests.

To assess the efficacy of the “Implementation Details of Air Pollution Prevention and Control Action Plan”, the chemical composition of PM2.5 and other pollutants was determined during the winters of 2013–2014 and 2016–2017 at two urban sites in Xiangtan City, Hunan. The concentrations of PM2.5, SO2, and NO2 decreased from 146.0 to 94.5 μg/m3, 75.9 to 33.5 μg/m3, and 80.6 to 55.8 μg/m3, respectively, from winter 2013–2014 to winter 2016–2017. The concentrations of almost all the major chemical components of PM2.5 decreased as well, particularly secondary inorganic aerosols (SIAs). These results indicate that the implementation of the air quality control plan was very effective in improving air quality. Analysis of the data also suggests that SIA formation is likely responsible for high winter PM2.5 pollution and that high relative humidity levels and low wind speed can promote the formation of SIA. A 72-h back trajectory analysis shows that both regional transport and the accumulation of local pollutants under stagnant meteorological conditions promote the occurrence of episodes of high wintertime pollution levels.

This paper reports the chemistry of fine (PM2.5) and coarse (PM10) aerosols sampled over a period of three years during 2018–2021 at a semi -arid tropical location in the rain shadow region of the peninsular India. The data is classified in to dry (December to May) and wet (June to November) periods. Scavenging effect due to rains have culminated in to less concentrations of both fine and coarse aerosols and their ionic components in the wet period. Significantly high concentrations of the crustal components such as Ca, Na, K and Mg from the local dust resulted in the alkaline pH in both dry and wet periods with Ca and Mg emerging as major neutralizing components. Overall, < 20% samples of both fine and coarse aerosols depicted acidic pH. Concentration of SO4 was comparatively more than NO3 indicating towards more presence of stationary sources (industrial/domestic emissions) than mobile (vehicular emissions) sources. Combustion generated and highly absorbing black carbon aerosols showed high concentration during the dry period. Local activities comprising residential, agricultural, vehicular and industrial emissions were the major sources of aerosols at Solapur however, the contribution from the distant sources were also found to contribute as inferred from the cluster analysis and concentration weighted trajectories (CWT). The observed abundances of the alkaline dust aerosols that could act as cloud condensation nuclei or ice nuclei will have important implications on the studies related to cloud aerosol precipitation interaction over this region.

A Raman lidar system was operated along with the Microtops sunphotometer measurements to carry out the study of the variation of the optical properties of aerosols over Palampur (32.11° N and 76.53° E), India from 17th April to 11th May 2019. The lidar system is furnished with Raman (N2) channel and depolarization channel allowing independent measurement of Lidar Ratio (LR) and linear depolarization ratio. The study reveals that the majority of the aerosols approximately were restricted within the planetary boundary layer (PBL) and very less loading was present in the free troposphere over the study location. The particle loading over the study period was found to be very less with aerosol backscatter coefficient (at 355 nm) ranging from ∼0.13 Mm−1sr−1 to ∼7.25 Mm−1sr−1 with mean value of 2.67 ± 0.82 Mm−1sr−1 and it is well supplemented by the mean aerosol optical depth (AOD) of 0.37 ± 0.13 obtained from Microtops Sunphotometer. The average lidar ratio values for 0-1 km altitude (L1) 72 ± 13sr, for 1-2 km (L2) altitude 55 ± 8sr, for 2-3 km (L3) 54 ± 15sr were observed as suggesting dominance of the biomass burning aerosols and anthropogenic aerosols. The particle depolarization ratio (355 nm) values were found from approximately 4.8 ± 2.7% to 11.5 ± 1.9% with the mean value of 7 ± 1.3% suggesting the presence of non-spherical particles. To trace the sources of the pollution, we derived the HYSPLIT trajectory which shows the majority of the movement was from local sources.

Pre and Post-Monsoon levels of ambient SO2, NO2, PM2.5 and the trace metals Fe, Cu, etc. were measured at industrial and residential regions of the Kochi urban area in South India for a period of two years. The mean PM2.5, SO2 and NO2 concentrations across all sites were 38.98 ± 1.38 µg/m3, 2.78 ± 0.85 µg/m3 and 11.90 ± 4.68 µg/m3 respectively, which is lower than many other Indian cities. There was little difference in any on the measured species between the seasons. A few sites exceeded the NAAQS (define acronym and state standard) and most of the sites exceeded WHO (define acronym and state standard) standard for PM2.5. The average trace metal concentrations (ng/m3) were found to be Fe (32.58) > Zn (31.93) > Ni (10.13) > Cr (5.48) > Pb (5.37) > Cu (3.24). The maximum concentration of trace metals except Pb were reported in industrial areas. The enrichment factor, of metals relative to crustal material, indicated anthropogenic dominance over natural sources for the trace metal concentration in Kochi’s atmosphere. This work demonstrates the importance of air quality monitoring in this area.

This study presents the chemical composition (carbonaceous and nitrogenous components) of aerosols (PM2.5 and PM10) along with stable isotopic composition (δ13C and δ15N) collected during winter and the summer months of 2015–16 to explore the possible sources of aerosols in megacity Delhi, India. The mean concentrations (mean ± standard deviation at 1σ) of PM2.5 and PM10 were 223 ± 69 µg m−3 and 328 ± 65 µg m−3, respectively during winter season whereas the mean concentrations of PM2.5 and PM10 were 147 ± 22 µg m−3 and 236 ± 61 µg m−3, respectively during summer season. The mean value of δ13C (range: − 26.4 to − 23.4‰) and δ15N (range: 3.3 to 14.4‰) of PM2.5 were − 25.3 ± 0.5‰ and 8.9 ± 2.1‰, respectively during winter season whereas the mean value of δ13C (range: − 26.7 to − 25.3‰) and δ15N (range: 2.8 to 11.5‰) of PM2.5 were − 26.1 ± 0.4‰ and 6.4 ± 2.5‰, respectively during the summer season. Comparison of stable C and N isotopic fingerprints of major identical sources suggested that major portion of PM2.5 and PM10 at Delhi were mainly from fossil fuel combustion (FFC), biomass burning (BB) (C-3 and C-4 type vegitation), secondary aerosols (SAs) and road dust (SD). The correlation analysis of δ13C with other C (OC, TC, OC/EC and OC/WSOC) components and δ15N with other N components (TN, NH4+ and NO3−) are also support the source identification of isotopic signatures.