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Journal of Atmospheric Chemistry

Current research reports and chronological list of recent articles..




The international scientific Journal of Atmospheric Chemistry is devoted to the study of the chemistry of the atmosphere, with particular emphasis on the region below about 100 km. The strongly interdisciplinary nature of atmospheric chemistry means that it embraces a great variety of sciences.

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Journal of Atmospheric Chemistry - Abstracts



Stable carbon and nitrogen isotopic characteristics of PM2.5 and PM10 in Delhi, India

Abstract

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.


Datum: 23.01.2022


Spatio-temporal variation and sensitivity analysis of aerosol particulate matter during the COVID-19 phase-wise lockdowns in Indian cities

Abstract

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.


Datum: 20.01.2022


Kinetics for the photo-chemical degradation of Methyl butyrate in presence of Cl atoms and OH radicals

Abstract

The Cl/OH initiated temperature dependent photo-oxidative reaction kinetics of methyl butyrate (MB) were examined using a relative rate (RR) technique. Gas chromatography with flame ionization and mass spectrometric detection were used to monitor the concentration of the reactants and to identify the products. The temperature dependent kinetics of MB with Cl atoms were measured with respect to the reaction of Cl with C2H 6 and C2H4. The temperature dependent kinetics for the reaction of MB with OH radicals were measured using n- propanol and iso -propanol as references. The obtained rate coefficients for the Cl and OH reactions with MB are, k Cl(Expt) (T) = [(7.76 ± 0.47) × 10 −11] exp [(10.31 ± 0.20)/T] cm3 molecule−1 s−1 and k OH(Expt) (T) = [(4.32 ± 0.21) × 10 −12] exp [-(25.26 ± 0.39)/T] cm3 molecule−1 s−1 respectively. Dual level direct dynamics were used to perform the computational calculations to further elucidate the mechanisms over the studied temperature range. The rate coefficients for H-abstraction reactions were computed using Canonical Variational Transition State Theory with Small Curvature Tunneling (CVT/SCT) with Interpolated Single Point Energies (ISPE) method. The rate coefficients over the studied temperature range yielded the Arrhenius equations: k Cl(Theory) (200–400 K) = [(4.05 ± 0.54) × 10–11] exp [-(2.80 ± 0.11)/T] cm3 molecule−1 s−1 and k OH(Theory) (200–400 K) = [(1.96 ± 0.68) × 10 -11] exp [-(384 ± 38)/T] cm3 molecule −1 s −1. Possible degradation mechanisms for the reactions are proposed based on the observed products. Thermo-chemical parameters, ozone formation potential, branching ratios, and the atmospheric lifetime of MB are calculated to understand the fate of MB in the atmosphere.


Datum: 01.12.2021


Seasonal characteristics and sources of carbonaceous components and elements of PM10 (2010–2019) in Delhi, India

Abstract

In this study we present the seasonal chemical characteristics and potential sources of PM10 at an urban location of Delhi, India during 2010˗2019. The concentrations of carbonaceous aerosols [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC) and water insoluble organic carbon (WIOC)] and elements (Al, Fe, Ti, Cu, Zn, Mn, Pb, Cr, F, Cl, Br, P, S, K, As, Na, Mg, Ca, B, Ni, Mo, V, Sr, Zr and Rb) in PM10 were estimated to explore their possible sources. The annual average concentration (2010–2019) of PM10 was computed as 227 ± 97 µg m−3 with a range of 34˗734 µg m−3. The total carbonaceous aerosols in PM10 was accounted for 22.5% of PM10 mass concentration, whereas elements contribution to PM10 was estimated to be 17% of PM10. The statistical analysis of OC vs. EC and OC vs. WSOC of PM10 reveals their common sources (biomass burning and/or fossil fuel combustion) during all the seasons. Enrichment factors (EFs) of the elements and the relationship of Al with other crustal metals (Fe, Ca, Mg and Ti) of PM10 indicates the abundance of mineral dust over Delhi. Principal component analysis (PCA) extracted the five major sources [industrial emission (IE), biomass burning + fossil fuel combustion (BB + FFC), soil dust, vehicular emissions (VE) and sodium and magnesium salts (SMS)] of PM10 in Delhi, India. Back trajectory and cluster analysis of airmass parcel indicate that the pollutants approaching to Delhi are mainly from Pakistan, IGP region, Arabian Sea and Bay of Bengal.


Datum: 01.12.2021


Wet deposition of atmospheric inorganic reactive nitrogen (Nr) across an urban-industrial-rural transect of Nr emission hotspot (India)

Abstract

The present study comprehensively reports the simultaneous measurement of wet deposition of total inorganic nitrogen (TIN; which is the sum of the NH4+-N and NO3-N) at three different sites in Nr emission hotspot of Indo-Gangetic plain (IGP) over a year-long temporal scale from October 2017 to September 2018. At rural Meetli (MTL) site, urban Baraut (BRT) site and industrial Loni (LNI) site, the annual wet deposition of NH4+-N was estimated as 21.87, 19.48 and 7.43 kg N ha−1 yr−1, respectively; the annual wet deposition NO3-N was estimated as 12.96, 12.17 and 4.44 kg N ha−1 yr−1, respectively; and the annual wet deposition of TIN was estimated as 34.83, 31.64 and 11.87 kg N ha−1 yr−1, respectively. NH4+-N was dominantly contributing species in annual, monsoon and non-monsoon-time wet deposition of TIN at all sites. The spatial gradient (variability) in percent contribution of NH4+ to total annual volume-weighted mean (VWM) concentration of all analyte ions was observed as MTL (43.23%) > BRT (37.90%) > LNI (30%). On the other hand, the spatial gradient in percent contribution of NO3 to total annual VWM concentration of all analyte ions was observed as MTL (7.45%) > BRT (6.89%) > LNI (5.32%). The extremely narrow range of NH4+-N/NO3-N ratios (ranging from 1.60 at BRT site to 1.69 at LNI site) showed the approximately equal relative abundance of oxidized and reduced nitrogen (N) deposition across all sites. Inferences from enrichment factor analysis, principal component analysis and Pearson’s correlation coefficient analysis suggested that across all sites, virtually all NH4+-N and NO3-N depositions were originated anthropogenically. The annual wet deposition of TIN measured in this study showed ≥ 6865%, ≥ 6228% and ≥ 2274% increment than the natural N deposition rate at MTL, BRT and LNI site, respectively. These empirically measured annual wet depositions of TIN also emanated theoretical transgression of critical N load threshold across all sites therefore signifying probable undermining of long-term elastic stability and resilience of ecosystems against stressor in the study domain.


Datum: 01.12.2021


Carbon isotopic signatures of carbonyls from roadside air observation

Abstract

In this work, isotopic effects of carbonyls were evaluated during the simulation sampling of gaseous carbonyls by using a carbon isotope method developed, and then variation characteristics of carbon isotopic compositions were investigated for three dominant carbonyls including formaldehyde, acetaldehyde and acetone in the roadside air of Nanning for the first time. A small difference in δ13C values (0.04 to 0.50 ‰) were observed between the calculated and measured values of carbonyl-derivatives, indicating that the effect on carbon isotopic fractionation could hardly occurred in the simulation sampling of gaseous carbonyls. The roadside air measurements showed that \({\delta }^{13}\) C values of formaldehyde, acetaldehyde and acetone were –36.02 ‰ to –31.18 ‰, –35.35 ‰ to –32.01 ‰ and –30.45 ‰ to –29.09 ‰, respectively. Further correlation of the measured \({\delta }^{13}\) C values was good for formaldehyde, acetaldehyde and acetone (R2 = 0.6275–0.7755), indicating that their similar sources could be the direct vehicular emission or indirect productions from precursors such as hydrocarbons. Particularly, formaldehyde, acetaldehyde and acetone in the roadside air were all enriched in the early afternoon by round 0.5–6 ‰ in 13C compared to other sampling durations, which was likely due to the contributions from the positive photo-oxidation productions of hydrocarbons. Finally, it was found that all measured \({\delta }^{13}\) C values (–36.5 ‰ to –29.0 ‰) agreed with the forecasted \({\delta }^{13}\) C range (–43.0 ‰ to –26.0 ‰) according to the 13C mass balance of carbonyls and their precursors such as hydrocarbons, indirectly confirming such positive productions in the roadside air.


Datum: 01.12.2021


Size distributions and dry deposition fluxes of water-soluble inorganic nitrogen in atmospheric aerosols in Xiamen Bay, China

Abstract

Size-segregated aerosol particles were collected using a high volume MOUDI sampler at a coastal urban site in Xiamen Bay, China, from March 2018 to June 2020 to examine the seasonal characteristics of aerosol and water-soluble inorganic ions (WSIIs) and the dry deposition of nitrogen species. During the study period, the annual average concentrations of PM1, PM2.5, PM10, and TSP were 14.8 ± 5.6, 21.1 ± 9.0, 35.4 ± 14.2 μg m−3, and 45.2 ± 21.3 μg m−3, respectively. The seasonal variations of aerosol concentrations were impacted by the monsoon with the lowest value in summer and the higher values in other seasons. For WSIIs, the annual average concentrations were 6.3 ± 3.3, 2.1 ± 1.2, 3.3 ± 1.5, and 1.6 ± 0.8 μg m−3 in PM1, PM1-2.5, PM2.5–10, and PM>10, respectively. In addition, pronounced seasonal variations of WSIIs in PM1 and PM1-2.5 were observed, with the highest concentration in spring-winter and the lowest in summer. The size distribution showed that SO42−, NH4+ and K+ were consistently present in the submicron particles while Ca2+, Mg2+, Na+ and Cl mainly accumulated in the size range of 2.5–10 μm, reflecting their different dominant sources. In spring, fall and winter, a bimodal distribution of NO3 was observed with one peak at 2.5–10 μm and another peak at 0.44–1 μm. In summer, however, the fine mode peak disappeared, likely due to the unfavorable conditions for the formation of NH4NO3. For NH4+ and SO42−, their dominant peak at 0.25–0.44 μm in summer and fall shifted to 0.44–1 μm in spring and winter. Although the concentration of NO3–N was lower than NH4–N, the dry deposition flux of NO3–N (35.77 ± 24.49 μmol N m−2 d−1) was much higher than that of NH4–N (10.95 ± 11.89 μmol N m−2 d−1), mainly due to the larger deposition velocities of NO3–N. The contribution of sea-salt particles to the total particulate inorganic N deposition was estimated to be 23.9—52.8%. Dry deposition of particulate inorganic N accounted for 0.95% of other terrestrial N influxes. The annual total N deposition can create a new productivity of 3.55 mgC m−2 d−1, accounting for 1.3–4.7% of the primary productivity in Xiamen Bay. In light of these results, atmospheric N deposition could have a significant influence on biogeochemistry cycle of nutrients with respect to projected increase of anthropogenic emissions from mobile sources in coastal region.


Datum: 11.10.2021


Effects of light intensity on the production of VSLs from the marine diatom Ditylum brightwellii

Abstract

Very short-lived substances (VSLs) are known to play an important role in ozone depletion in the troposphere and stratosphere. Environmental factors that influence the production of these compounds by marine phytoplankton, which is known to be the source of these compounds in open oceans, have not yet been well studied. Here we examined the effects of light intensity on the production of VSLs by the marine diatom Ditylum brightwellii. Bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl), bromoform (CHBr3), chloroform (CHCl3), and dibromomethane (CH2Br2) in cultures incubated under full spectrum daylight intensities of 30, 60, and 120 µmol photons m− 2 s− 1 were measured using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring chlorophyll-a concentration and cell density. Both the chlorophyll-a concentration (the cell density) and the production rates of VSLs increased with increasing light intensity. The maximum production rates of CHBrCl2, CHBr2Cl, CHBr3, CHCl3, and CH2Br2 were observed during the exponential or stationary phase, with the exception of CH2Br2 incubated under 30 µmol photons m− 2 s− 1. The chlorophyll a-normalized (or cell-normalized) production rates of VSLs increased with increasing light intensity, e.g., the maximum of chlorophyll a-normalized production rates of CHCl3 under light intensities of 30, 60 and 120 µmol photons m− 2 s− 1 were 0.06, 0.46 and 1.84 µmol (g chlorophyll a) −1 day− 1, respectively. Our results suggest that marine diatoms are one of the significant sources of VSLs and that light intensity is a significant factor in estimating VSLs emissions from the open ocean.


Datum: 17.09.2021


Study of seasonal variation of PM2.5 concentration associated with meteorological parameters at residential sites in Delhi, India

Abstract

The seasonal variation of particulate matter and its relationship with meteorological parameters were measured at five different residential sites in Delhi. Sampling was carried out for one year including all three seasons (summer, monsoon, and winter). The yearly average concentration of particulate matter (PM2.5) was 135.16 ± 41.34 µg/m3. The highest average values were observed in winter (208.44 ± 43.67 µg/m3) and the lowest during monsoon season (80.29 ± 39.47 µg/m3). The annual average concentration of PM2.5 was found to be the highest at the Mukherjee Nagar site (242.16 µg/m3 ) during the winter and lowest at (Jawaharlal Nehru University) JNU (35.65 µg/m3) during the monsoon season. The strongest correlation between PM mass and a meteorological parameter was a strong negative correlation with temperature (R2=0.55). All other parameters were weakly correlated (R2<0.2) with PM mass.


Datum: 01.09.2021


Aerosol removal coefficients based on 7Be, 210Pb, and 210Po radionuclides in the urban atmosphere

Abstract

In this study, the aerosol removal coefficients based on 7Be, 210Pb and 210Po radionuclides in the urban air, in Lodz, Poland, were investigated over 3 years, between May 2014 and December 2017. Results representing the summer/warm and winter/cold seasons were applied to quantity and quality estimates of aerosol removal processes. The values for the removal processes were closely dependent on the meteorological conditions; therefore, a set of nine meteorological parameters was employed in the analysis. The multiple regression method was applied to explain the relationship between the removal coefficients of aerosols and independent factors identified using Principal Component Analysis.


Datum: 01.09.2021


Trace gases and PM2.5-bound metal abundance over a tropical urban environment, South India

Abstract

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.


Datum: 01.09.2021


Source apportionment and health risks assessment of black carbon Aerosols in an urban atmosphere in East India

Abstract

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.


Datum: 01.09.2021


Source identification and exposure assessment to PM10 in the Eastern Carpathians, Romania

Abstract

Observations of particulate matter less than 10 µm (PM10) were conducted from January to December in 2015 in the Ciuc basin, Eastern Carpathians, Romania. Daily concentrations of PM10 ranged from 10.90 to 167.70 µg/m3, with an annual mean concentration of 46.31 µg/m3, which is higher than the European Union limit of 40 µg/m3. Samples were analyzed for a total of 21 elements. O, C and Si were the most abundant elements accounting for about 85% of the PM10 mass. Source identification showed that the elemental composition of PM10 is represented by post volcanic activity, crustal origin, and anthropogenic sources, caused by the resuspension of crustal material, sea salt and soil dust. The average PM10 composition was 72.10% soil, 20.92% smoke K, 13.84% salt, 1.53% sulfate and 1.02% organic matter. The back-trajectory analysis showed that the majority of PM10 pollution comes from the West, Southwest and South.


Datum: 01.06.2021


Composition dependent density of ternary aqueous solutions of ionic surfactants and salts

Abstract

Surfactants exist in atmospheric aerosols mixed with inorganic salts and can significantly influence the formation of cloud droplets due to bulk–surface partitioning and surface tension depression. To model these processes, we need continuous parametrizations of the concentration dependent properties of aqueous surfactant–salt solutions for the full composition range from pure water to pure surfactant or salt. We have developed density functions based on the pseudo-separation method and Young’s mixing rule for apparent partial molal volumes for solutions that mimic atmospheric droplets of marine environments. The developed framework requires only model parameters from binary water–salt and water–surfactant systems and includes the effect of salinity on micellization with composition-dependent functions for the critical micelle concentration (CMC). We evaluate different models and data available in the literature to find the most suitable representations of the apparent partial molal volume of sodium chloride (NaCl) in aqueous solutions and the CMC of selected atmospheric and model surfactants in pure water and aqueous NaCl solutions. We compare model results to experimental density data, available in the literature and obtained from additional measurements, for aqueous solutions containing one of the ionic surfactants sodium octanoate, sodium decanoate, sodium dodecanoate or sodium dodecylsulfate mixed with NaCl in different relative ratios. Our model follows the experimental trends of increasing densities with increasing surfactant concentrations or increasing surfactant–salt mixing ratios both, below and above the CMC, capturing the effect of the inorganic salt on the surfactant micellization.


Datum: 01.06.2021


Wet deposition ethanol concentration at US atmospheric integrated research monitoring network (AIRMoN) sites

Abstract

Ethanol concentrations measured in 178 event-based wet deposition samples collected at five Atmospheric Integrated Research Monitoring Network (AIRMoN) sites in the Eastern US between February 2018 to January 2019 ranged from below the detection limit of 19 nM to 4160 nM. The volume weighted average ethanol concentration at each site ranged from 237 nM to 1375 nM. No significant correlation was observed between ethanol and any analytes (NH4+, Cl, SO42−, NO3, Ca2+, Na+, Mg2+, K+, PO43− and H+) at all sites in the study, likely due to differences in atmospheric residence time and emission sources. Significant seasonal variations of ethanol were not observed for any sites, however notably higher concentrations in the winter vs. summer and growing vs. nongrowing seasons suggest photochemical dynamics play a substantial role in seasonal atmospheric concentrations. The AIRMoN concentrations were combined with previous measured ethanol wet deposition data to produce an updated empirical-based global wet deposition ethanol flux of 3.7 ± 1.8 Tg/yr (n = 1051). The carbon isotopic composition of a subset of samples ranged from −25.8 to −15.7‰ with an average of (−20.4 ± 4.0‰, n = 6). Isotope mixing model results indicate an approximately equivalent contribution of biogenic (55.2 ± 14.4%) and anthropogenic (44.8 ± 14.4%) sources of ethanol to the atmosphere over all collections sites. Results provide atmospheric scientists, environmental chemists and policy makers with baseline U.S. atmospheric ethanol concentrations in order to help determine the impact of future ethanol fuel production and to help quantify the wet deposition ethanol sink.


Datum: 01.06.2021


Ambient air characteristics of biogenic volatile organic compounds at a tropical evergreen forest site in Central Western Ghats of India

Abstract

Non-methane volatile organic compounds (NMVOCs) play key roles in local and regional atmospheric chemistry as precursors for the production of ozone and secondary organic aerosols. Ambient air C2-C5 NMVOCs were measured at a tropical forest site in the central Western Ghats and urban site of Udaipur in India during the late monsoon period of 2016–17 and 2015, respectively. In the Western Ghats, air samples were collected from the protected Bhagwan Mahaveer Sanctuary. Ethene, propene, and isoprene were the dominant biogenic compounds with mean concentrations of 4.8 ± 2, 1.6 ± 0.66 and 1.05 ± 0.43 ppb, respectively. The concentrations of anthropogenic compounds such as propane and pentane were significantly lower than those of light alkenes. The contributions of ethene and propene among different NMVOCs were ~ 44 and 14%, respectively. However, the contributions of isoprene were highly variable of 3–22%. The tight correlation (r2 = 0.90) between the mixing ratios of ethene and propene and their ratio indicates their common formation and emission mechanisms. The molar emission ratio of ethene/propene (2.9 ± 0.17 ppb ppb−1) was comparable to those measured at other biogenic sites of Asia while higher than those reported for mid-latitude sites. The concentrations of light alkenes and isoprene at the Western Ghats were 4–5 times higher than those measured in an urban environment in the same season. The higher ozone formation potentials and Propylene-Equivalent concentrations of alkenes and isoprene than those of other NMVOCs indicate important implications of biogenic emissions on ozone photochemistry in the forest regions of India.

Graphical abstract


Datum: 01.06.2021


Characterization of Rome’s rainwater in the early of 2018 aiming to find correlations between chemical-physical parameters and sources of pollution: a statistical study

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


Datum: 01.02.2021


Chemical composition and source attribution of PM2.5 and PM10 in Delhi-National Capital Region (NCR) of India: results from an extensive seasonal campaign

Abstract

Ambient particulate matter concentrations in Delhi and its peripheral towns has been a matter of serious concern in the last decade. Understanding the changing nature of the chemical composition of particulates, their spatial and seasonal variability can be utilized for identifying probable sources. This study presents an extensive dataset of the chemical composition of PM2.5 and PM10 collected using speciation samplers, from 19 locations representing different activities and spread across Delhi–NCR during summer and winter seasons in the year 2016–17. Identification of contributing sources using chemical ratios as source indicators is attempted. A distinct seasonal variability in both PM2.5 and PM10 was observed, with winter maxima and summer minima. The fine fraction i.e. PM2.5 was dominated by organic matter (OM) with mean concentrations of 40.96±25.74 μg/m3 followed by Sulfate-Nitrate-Ammonium (SNA) ions (31.44±20.69 μg/m3) and Elemental Carbon (EC) (19.56±12.57 μg/m3); while the coarse fraction i.e. PM10 was dominated by OM (73.03±40.55 μg/m3) and SNA (47.25±30.56 μg/m3) along with significant contributions from crustal materials (40.85±18.89 μg/m3). The chemical ratios suggested mixed sources of PM with major contributions from vehicular emissions, re-suspended and/or construction dust, and fossil fuel combustion along with intermittent contributions from biomass and open waste burning. This analysis provides useful insights into the sources and processes affecting the particulate formation and underlines the need to control primary emissions as well as secondary precursors for air quality improvements in the region. The data generated under this campaign can also serve as an essential input for further evaluation using receptor modeling.


Datum: 01.02.2021


Inorganic Ionic Composition of Rainwater at a High Altitude Station over the Western Ghats in Peninsular India

Abstract

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 Ca2+ (25%), Na+ (19%), Cl(23%), SO42− (10%), and Mg2+ (9%) with NH4+, NO3 and K+ together forming about 8% of ionic composition. Moreover, ample presence of dust source (Ca2+) was found that acted as a major neutraliser to the acidic ions. The order of Neutralisation Factor of ions was Ca2+ > Mg2+ > NH4+. 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 Ca2+, SO42−, Mg2+ 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 (Ca2+, Mg2+), emissions from the fossil fuel and biomass burning (NO3, SO42−) and the agriculture/farming activities (NH4+).


Datum: 01.02.2021


Emission estimates of trace gases (VOCs and NOx) and their reactivity during biomass burning period (2003–2017) over Northeast India

Abstract

The study analysed spatio-temporal distribution of fire radiative power (FRP) and estimates of trace gases [volatile organic compounds (VOCs) and nitrogen oxides (NOx)] 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 NOx emission estimates were 431 and 69.5 mg/m2/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 (O3) 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/NOx 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 O3 pollution.


Datum: 01.02.2021


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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