scholarly journals Long-term record of aerosol optical properties and chemical composition from a high-altitude site (Manora Peak) in Central Himalaya

2010 ◽  
Vol 10 (23) ◽  
pp. 11791-11803 ◽  
Author(s):  
K. Ram ◽  
M. M. Sarin ◽  
P. Hegde
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
High Altitude ◽  
Water Soluble ◽  
Western India ◽  
Central Himalaya ◽  
Gangetic Plain ◽  
Long Term Study ◽  
Inorganic Species

Abstract. A long-term study, conducted from February 2005 to July 2008, involving chemical composition and optical properties of ambient aerosols from a high-altitude site (Manora Peak: 29.4° N, 79.5° E, ~1950 m a.s.l.) in the central Himalaya is reported here. The total suspended particulate (TSP) mass concentration varied from 13 to 272 μg m−3 over a span of 42 months. Aerosol optical depth (AOD) and TSP increase significantly during the summer (April–June) due to increase in the concentration of mineral dust associated with the long-range transport from desert regions (from the middle-East and Thar Desert in western India). The seasonal variability in the carbonaceous species (EC, OC) is also significantly pronounced, with lower concentrations during the summer and monsoon (July–August) and relatively high during the post-monsoon (September–November) and winter (December–March). On average, total carbonaceous aerosols (TCA) and water-soluble inorganic species (WSIS) contribute nearly 25 and 10% of the TSP mass, respectively. The WSOC/OC ratios range from 0.36 to 0.83 (average: 0.55 ± 0.15), compared to lower ratios in the Indo-Gangetic Plain (range: 0.35–0.40), and provide evidence for the enhanced contribution from secondary organic aerosols. The mass fraction of absorbing EC ranged from less than a percent (during the summer) to as high as 7.6% (during the winter) and absorption coefficient (babs, at 678 nm) varied between 0.9 to 33.9 Mm−1 (1 Mm−1=10−6 m−1). A significant linear relationship between babs and EC (μgC m−3) yields a slope of 12.2 (± 2.3) m2 g−1, which is used as a measure of the mass absorption efficiency (σabs) of EC.

scholarly journals Long-term record of aerosol optical properties and chemical composition from a high-altitude site (Manora Peak) in Central Himalaya

2010 ◽  
Vol 10 (3) ◽  
pp. 7435-7467 ◽  
Author(s):  
K. Ram ◽  
M. M. Sarin ◽  
P. Hegde
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
High Altitude ◽  
Water Soluble ◽  
Simultaneous Increase ◽  
Central Himalaya ◽  
Aerosol Optical Properties ◽  
Abundance Pattern ◽  
Post Monsoon

Abstract. This MS reports on a long-term study of aerosol optical properties and chemical composition, conducted during February 2005–July 2008, from a high-altitude site (Manora Peak, ~2000 m a.s.l.) in the central Himalaya. The chemical analyses suggest that, on average, total carbonaceous aerosols (TCA) and water-soluble inorganic species (WSIS) contribute nearly 25% and 10% of the total suspended particulate (TSP) mass, respectively. Both, TSP and aerosol optical depth (AOD) exhibit significant increase during summer months, with simultaneous increase in the abundance of mineral dust under the prevailing south-westerly winds and long-range transport from desert regions (from middle-East and Thar Desert in western India). The temporal variability in the abundance pattern of carbonaceous species (EC, OC) is also significantly pronounced, with lower concentrations occurring during summertime (April–June) and monsoon (July–August) and relatively high during post-monsoon (September–November) and wintertime (December–March). The WSOC/OC ratios (range: 0.32 to 0.83) during summer and post-monsoon suggest significant contribution from secondary organic aerosols. The mass fraction of absorbing EC (elemental carbon) ranges from less than a percent (during summer and monsoon) to as high as 7.6% (during winter) and absorption coefficient (babs, at 678 nm) varied as 0.9–33.9 Mm−1 (1 Mm−1=10−6 m−1). The linear regression analysis between (babs and EC concentration (μgC m−3) yields a slope of 12.2(±2.3) m2 g−1, referred as mass absorption efficiency (σabs) of EC. However, temporal data suggests lower σabs values during winter and higher in summer and post-monsoon. The change in the mixing state of aerosols and/or variability in the emission sources could be a plausible reason for the variability in σabs at this high-altitude site (Manora Peak).

scholarly journals The sensitivity of PM<sub>2.5</sub> acidity to meteorological parameters and chemical composition changes: 10-year records from six Canadian monitoring sites

2019 ◽  
Author(s):  
Ye Tao ◽  
Jennifer G. Murphy
Keyword(s):  
Chemical Composition ◽  
Meteorological Parameters ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Seasonal Cycles ◽  
Accuracy And Precision ◽  
Different Seasons ◽  
Water Soluble Inorganic Ions ◽  
Composition Changes

Abstract. Aerosol pH is difficult to measure directly but can be calculated if the chemical composition is known with sufficient accuracy and precision to calculate the aerosol water content and the H+ concentration through ion balance. In practical terms, simultaneous measurements of at least one semi-volatile constitute, e.g. NH3 or HNO3, are required to provide a constraint on the calculation of pH. Long-term records of aerosol pH are scarce due to the limited monitoring of NH3 in conjunction with PM2.5. In this study, 10-year (2007–2016) records of pH of PM2.5 at six eastern Canadian sites were calculated using the E-AIM II model with the input of gaseous NH3, gaseous HNO3 and major water-soluble inorganic ions in PM2.5 provided by Canada's National Air Pollution Surveillance (NAPS) Program. Clear seasonal cycles of aerosol pH were found with lower pH (~2) in summer and higher pH (~3) in winter consistently across all six sites, while the day-to-day variations of aerosol pH were higher in winter compared to summer. Tests of the sensitivity of aerosol pH to meteorological parameters demonstrate that the changes in ambient temperature largely drive the seasonal cycle of aerosol pH. The sensitivity of pH to chemical composition shows that pH has different responses to the changes in chemical composition in different seasons. During summertime, aerosol pH was mainly determined by temperature with limited impact from changes in NHx or sulfate concentrations. However, in wintertime, both meteorological parameters and chemical composition contribute to the variations in aerosol pH, resulting in the larger variation during wintertime. This study reveals that the sensitivity of aerosol pH to chemical composition is distinctly different under different meteorological conditions and needs to be carefully examined for any particular region.

scholarly journals First insights into northern Africa high-altitude background aerosol chemical composition and source influences

2021 ◽  
Vol 21 (24) ◽  
pp. 18147-18174
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Laurent Poulain ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
North Africa ◽  
Mineral Dust ◽  
Water Soluble ◽  
Atmospheric Composition ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Aerosol Chemical Composition

Abstract. Field measurements were conducted to determine aerosol chemical composition at a newly established remote high-altitude site in North Africa at the Atlas Mohammed V (AMV) atmospheric observatory located in the Middle Atlas Mountains. The main objectives of the present work are to investigate the variations in the aerosol composition and better assess global and regional changes in atmospheric composition in North Africa. A total of 200 particulate matter (PM10) filter samples were collected at the site using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, water-soluble ions, organic carbon (OC/EC), aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAH) contents. The results indicate that high-altitude aerosol composition is influenced by both regional and transregional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. During background conditions characterized by low wind speeds (avg. 3 m s-1) and mass concentrations in the range from 9.8 to 12 μg m-3, the chemical composition is found to be dominated by inorganic elements, mainly suspended dust (61 %) and ionic species (7 %), followed by organic matter (7 %), water content (12 %), and unidentified mass (11 %). Despite the proximity of the site to the Sahara, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 22 % of the sampling duration. Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as heneicosane, hentriacontane, and nonacosane. The AMV site is dominated by four main air mass inflows, which often leads to different aerosol chemical compositions. Mineral dust influence was seasonal and ranged between 21 % and 74 % of the PM mass, with peaks observed during the summer, and was accompanied by high concentrations of SO42- of up to 3.0 μg m-3. During winter, PM10 concentrations are low (<30 μg m-3), the influence of the desert is weaker, and the marine air masses (64 %) are more dominant with a mixture of sea salt and polluted aerosol from the coastal regions (Rabat and Casablanca). During the daytime, mineral dust contribution to PM increased by about 42 % because of road dust resuspension. In contrast, during nighttime, an increase in the concentrations of alkanes, PAHs, alkane-2-ones, and anthropogenic metals such as Pb, Ni, and Cu was found due to variations in the boundary layer height. The results provide the first detailed seasonal and diurnal variation of the aerosol chemical composition, which is valuable for long-term assessment of climate and regional influence of air pollution in North Africa.

scholarly journals Characteristics of Aerosol during a Severe Haze-Fog Episode in the Yangtze River Delta: Particle Size Distribution, Chemical Composition, and Optical Properties

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 56 ◽  
Author(s):  
Ankang Liu ◽  
Honglei Wang ◽  
Yi Cui ◽  
Lijuan Shen ◽  
Yan Yin ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Chemical Composition ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Water Soluble ◽  
Air Masses ◽  
Soluble Ions ◽  
Wide Range ◽  
Water Soluble Ions

Particle size distribution, water soluble ions, and black carbon (BC) concentration in a long-term haze-fog episode were measured using a wide-range particle spectrometer (WPS), a monitor for aerosols and gases (MARGA), and an aethalometer (AE33) in Nanjing from 16 to 27 November, 2018. The observation included five processes of clean, mist, mix, haze, and fog. Combined with meteorological elements, the HYSPLIT model, and the IMPROVE model, we analyzed the particle size distribution, chemical composition, and optical properties of aerosols in different processes. The particle number size distribution (PNSD) in five processes differed: It was bimodal in mist and fog and unimodal in clean, mix, and haze. The particle surface area size distribution (PSSD) in different processes showed a bimodal distribution, and the second peak of the mix and fog processes shifted to a larger particle size at 480 nm. The dominant air masses in five processes differed and primarily originated in the northeast direction in the clean process and the southeast direction in the haze process. In the mist, mix, and fog processes local air masses dominated. NO3− was the primary component of water soluble ions, with the lowest proportion of 45.6% in the clean process and the highest proportion of 53.0% in the mix process. The ratio of NH4+ in the different processes was stable at approximately 23%. The ratio of SO42− in the clean process was 26.2%, and the ratio of other processes was approximately 20%. The average concentration of BC in the fog processes was 10,119 ng·m−3, which was 3.55, 1.80, 1.60, and 1.46 times that in the processes of clean, mist, mix, and haze, respectively. In the different processes, BC was primarily based on liquid fuel combustion. NO3−, SO42−, and BC were the main contributors to the atmospheric extinction coefficient and contributed more than 90% in different processes. NO3− contributed 398.43 Mm−1 in the mix process, and SO42− and BC contributed 167.90 Mm−1 and 101.19 Mm−1, respectively, during the fog process.

scholarly journals The sensitivity of PM<sub>2.5</sub> acidity to meteorological parameters and chemical composition changes: 10-year records from six Canadian monitoring sites

2019 ◽  
Vol 19 (14) ◽  
pp. 9309-9320 ◽  
Author(s):  
Ye Tao ◽  
Jennifer G. Murphy
Keyword(s):  
Chemical Composition ◽  
Meteorological Parameters ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Volatile Constituent ◽  
Accuracy And Precision ◽  
Different Seasons ◽  
Water Soluble Inorganic Ions ◽  
Conjugate Bases

Abstract. Aerosol pH is difficult to measure directly but can be calculated if the chemical composition is known with sufficient accuracy and precision to calculate the aerosol water content and the H+ concentration through the equilibrium among acids and their conjugate bases. In practical terms, simultaneous measurements of at least one semi-volatile constituent, e.g. NH3 or HNO3, are required to provide a constraint on the calculation of pH. Long-term records of aerosol pH are scarce due to the limited monitoring of NH3 in conjunction with PM2.5. In this study, 10-year (2007–2016) records of pH of PM2.5 at six eastern Canadian sites were calculated using the E-AIM II model with the input of gaseous NH3, gaseous HNO3 and major water-soluble inorganic ions in PM2.5 provided by Canada's National Air Pollution Surveillance (NAPS) Program. Clear seasonal cycles of aerosol pH were found with lower pH (∼2) in summer and higher pH (∼3) in winter consistently across all six sites, while the day-to-day variations of aerosol pH were higher in winter compared to summer. Tests of the sensitivity of aerosol pH to meteorological parameters demonstrate that the changes in ambient temperature largely drive the seasonal cycle of aerosol pH. The sensitivity of pH to chemical composition shows that pH has different responses to the changes in chemical composition in different seasons. During summertime, aerosol pH was mainly determined by temperature with limited impact from changes in NHx or sulfate concentrations. However, in wintertime, both meteorological parameters and chemical composition contribute to the variations in aerosol pH, resulting in the larger variation during wintertime. This study reveals that the sensitivity of aerosol pH to chemical composition is distinctly different under different meteorological conditions and needs to be carefully examined for any particular region.

Optical properties of atmospheric brown carbon (BrC) for photochemical and biomass burning-dominated aerosol regimes in India.

2020 ◽  
Author(s):  
Archita Rana ◽  
Supriya Dey ◽  
Sayantan Sarkar
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Global Climate ◽  
Strong Association ◽  
Absorption Efficiency ◽  
Water Soluble ◽  
Tropospheric Chemistry ◽  
Gangetic Plain ◽  
Brown Carbon ◽  
Fluorescence Measurements

&lt;p&gt;Black and brown carbon (BC and BrC) are potent climate forcing agents with pronounced effects on global climate and tropospheric chemistry. Given the large heterogeneities in BC emission inventories from India and the paucity of studies on BrC characteristics, field-based measurements of BC and BrC sources and optical properties are essential to understand their impacts on regional climate. To address this issue, we report the first ground-based measurements of BC and BrC from a rural location in the highly polluted eastern Indo-Gangetic Plain (IGP) during May-November 2018 encompassing the photochemistry-dominated summer (May-June) and regional biomass burning (BB)-dominated post-monsoon (October-November) periods. A 7-wavelength Aethalometer was used for time-resolved measurements of BC mass and was supplemented by UV-Vis and fluorescence measurements of time-integrated (24 h) aqueous and organic BrC fractions, and measurements of OC, EC, WSOC, and ionic species.&lt;br&gt;The daily averaged BC increased 4 times during the BB regime (12.3 &amp;#177; 3.9 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt;) as compared to summer (4.2 &amp;#177; 0.8 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt;), while aqueous and organic BrC fractions demonstrated light absorption (babs_365) enhancements of 3-5 times during BB. For aqueous BrC, the averaged AE of 5.9-6.2 and a prominent fluorescence peak at ~420 nm suggested the presence of humic-like substances (HULIS), potentially from secondary photochemical formation during summer and primary emission during BB periods. Fluorescence and UV-Vis spectra also indicated the presence of nitroaromatic compounds, presumably from OH oxidation in summer and nighttime NO3- oxidation in the presence of enhanced NOx and precursor emission during BB. The latter was supported by the strong association between water-soluble organic carbon (WSOC; a proxy for aqueous BrC) and aerosol NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; (r=0.70, p&lt;0.05). During BB, the fraction of water-insoluble (i.e., organic) BrC increased from 41% at 330 nm to 59 % at 550 nm while during the photochemistry-dominated summer period, the water-insoluble BrC fraction decreased from 73% at 400 nm to 41% at 530 nm, possibly due to photobleaching in the presence of OH. The BB-related BrC aerosol was also characterized by higher aromaticity and increased molecular weights of organic components as evidenced by mass absorption efficiency (MAE) ratios (MAE&lt;sub&gt;250&lt;/sub&gt;/MAE&lt;sub&gt;365&lt;/sub&gt;). Overall, this study established that BrC is a significant component of light-absorbing aerosol in the eastern IGP and that BrC optical properties may vary significantly in this region depending on the relative dominance of aerosol emissions and atmospheric processes.&lt;/p&gt;

scholarly journals A review of current knowledge concerning PM<sub>2.5</sub> chemical composition, aerosol optical properties, and their relationships across China

2017 ◽  
Author(s):  
Jun Tao ◽  
Leiming Zhang ◽  
Junji Cao ◽  
Renjian Zhang
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Current Knowledge ◽  
Northern China ◽  
Water Soluble ◽  
Chemical Components ◽  
Carbonaceous Aerosols ◽  
Ambient Conditions ◽  
Aerosol Optical Properties ◽  
Inorganic Aerosols

Abstract. To obtain a thorough knowledge of PM2.5 chemical composition and its impact on aerosol optical properties across China, existing field studies conducted after the year of 2000 are reviewed and summarized in terms of geographical, inter-annual, and seasonal distributions. Annual PM2.5 was up to six times of the national air quality standard in some megacities in northern China. Annual PM2.5 was higher in northern than southern cities, and higher in inland than coastal cities. In a few cities with data longer than a decade, PM2.5 showed a slight decrease only in the second half of the past decade, while carbonaceous aerosols decreased, sulfate (SO42−) and ammonium (NH4+) remained at high levels, and nitrate (NO3−) increased. The highest seasonal averages of PM2.5 and its major chemical components were mostly observed in the cold seasons. Annual average contributions of secondary inorganic aerosols to PM2.5 ranged from 25 % to 48 %, and those of carbonaceous aerosols ranged from 23 % to 47 %, both with higher values in southern regions due to the frequent dust events in northern China. The geographical pattern of scattering coefficient (bsp) was similar to that of PM2.5, and that of aerosol absorption coefficient (bap) was determined by elemental carbon (EC) mass concentration and its coating. bsp in ambient condition of RH = 80 % can be amplified about 1.8 times of that under dry condition. Secondary inorganic aerosols accounted for about 60 % of aerosol extinction coefficient (bext) under ambient conditions in megacities with RH higher than 70 %. The mass scattering efficiency (MSE) of PM2.5 ranged from 3.0 to 5.0 m2 g−1 for aerosols produced from anthropogenic emissions and from 0.7 to 1.0 m2 g−1 for natural dust aerosols. The mass absorption efficiency (MAE) of EC ranged from 6.5 to 12.4 m2 g−1 in urban environments, but the MAE of water-soluble organic carbon (WSOC) was only 0.05 to 0.11 m2 g−1. Historical emission control policies in China and their effectiveness were discussed based on available chemically resolved PM2.5 data, which provides the much-needed knowledge for guiding future studies and emission policy making.

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

2020 ◽  
Vol 10 (14) ◽  
pp. 4858
Author(s):  
Seungshik Park ◽  
Hue Dinh Thi Hong ◽  
Sung Yong Cho ◽  
Min-Suk Bae
Keyword(s):  
Chemical Composition ◽  
Light Absorption ◽  
Significant Contribution ◽  
Water Soluble ◽  
Traffic Emissions ◽  
Pollution Monitoring ◽  
Poor Correlation ◽  
Transport Pathways ◽  
Important Contributor ◽  
Inorganic Species

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

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