atmospheric aerosols

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Molecular characterization of alkyl nitrates in atmospheric aerosols by ion mobility mass spectrometry

Molecular characterization of alkyl nitrates in atmospheric aerosols by ion mobility mass spectrometry

In this study, we present the first demonstration of the ion mobility mass spectrometry (IMS-MS) interfaced with an electrospray ionization (ESI) source that enables the molecu- lar characterization of alkyl nitrates in atmospheric aerosols. The IMS technique has been widely employed in the fields of biochemistry and homeland security. The majority of pre- vious studies that adapted ESI for IMS analysis employed ei- ther the desorption electrospray ionization (DESI) to detect trace amounts of ANs on ambient surfaces (Cotte-Rodríguez et al., 2005; Popov et al., 2005; Takáts et al., 2005; Justes et al., 2007) or the secondary electrospray ionization (SESI) for gas-phase AN measurements (Tam and Hill, 2004; Martínez- Lozano et al., 2009; Crawford and Hill, 2013). The analy- sis of ANs directly from liquid solutions, on the other hand, has not yet been widely explored. Hilton et al. (2010) found that the NO − 3 fragment dominates the IMS spectra of several types of ANs measured in the negative ESI, suggesting that these nitrate molecules readily fragment due to the thermally labile nature of the -ONO 2 functionality, thereby resulting in
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Optical Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Self Organizing Map for Climate Change Diagnostics

Optical Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Self Organizing Map for Climate Change Diagnostics

It has been demonstrated that the ÅE is a good indicator of fraction of small aerosol particles with radii r = 0.057 - 0.21 μm relative to large particles with ra- dii = 1.8 - 4 μm for atmospheric aerosols [24]. Additionally, the ÅE is often used as a qualitative indicator of aerosol particle size, with values greater than 2 indi- cating small particles associated with combustion byproducts, and values less than 1 indicating large particles like sea salt and dust [25]. Figure 2 shows the application of SOM on ÅE over each study site, specifically, Mbita and Mount Kilimanjaro are highly correlated and dominated by a single cluster. The single cluster can be attributed to the anthropogenic influence over the study sites i.e. land clearance, deforestation activities and biomass burning that dominate the study sites [21] [26]. This conclusion is arrived at since from Figure 3 the two sites experience distinct precipitation rates during the study period. On the con- trary, Nairobi is characterized by two clear clusters attributed to dry and wet seasons experienced over the site. The dominant aerosol particles over the site constitute vehicular and industrial emissions, biomass and refuse burning [27] as well as their long distance transport from the surrounding regions. These aerosol particles are highly hygroscopic in nature [28], hence, the two clear clus- ters that are modulated by the two seasons experienced over Nairobi. On the other hand, Kampala experienced two clusters but with relatively higher values in ÅE as compared to the rest of the study sites in the region. These values sug- gest the dominance of aerosol particles in the λ = 670 nm wavelength, these aerosol particles originate from vehicular emissions [23]. Malindi displays the least values in ÅE suggesting the existence of sea spray, sea salt and long distance transport of aerosol particles from the Arabian Peninsula desert via Monsoon winds which indeed are seasonal [20]. Likewise, SOM displays two clusters over Mau Forest complex which are associated to the two prevailing seasons experienced over the site. Additionally, continual biomass burning and forest
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The Cd isotope composition of atmospheric aerosols from the Tropical Atlantic Ocean

The Cd isotope composition of atmospheric aerosols from the Tropical Atlantic Ocean

Variations in stable isotope composition have recently been employed to study the environmental cycling of Cd, particularly in the ocean. Cadmium is subject to internal cycling in the ocean, with removal through biological uptake in surface waters and regeneration at depth due to remineralization of organic material [Boyle et al., 1976; Bruland, 1980]. This regenerated Cd is returned to the surface through deepwater convec- tion, diapycnal mixing, and upwelling, constituting the dominant Cd source to ocean surface waters [Bruland, 1980]. These biogeochemical processes produce mass-dependent Cd isotope variations, whereby surface waters evolve to “ heavier ” isotope compositions with increasing Cd depletion [Ripperger et al., 2007; Abouchami et al., 2011; Xue et al., 2013; Abouchami et al., 2014]. Deviations from the expected relationship between Cd concentrations and isotope compositions due to biological cycling have been used to decon- volve the effects of processes such as water mass mixing and removal through sulfide precipitation on the distribution of Cd in the ocean [Xue et al., 2013; Yang et al., 2014; Janssen et al., 2014; Conway and John, 2015]. External inputs of Cd should also perturb the coupled Cd concentration and isotope composition distributions imparted by biological cycling [Ripperger et al., 2007; Yang et al., 2012, 2014]. Hence, Cd isotopes will be a useful tracer of external inputs to ocean surface waters. To this end, it is necessary to constrain the Cd isotope compositions of external oceanic inputs. Currently, limited data have been published for the compo- sition of riverine fluxes [Lambelet et al., 2013], while only unpublished results are available for atmospheric aerosols from a single locality [Yang et al., 2015].
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Spatial Temporal Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Growing Hierarchical Self Organizing Maps

Spatial Temporal Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Growing Hierarchical Self Organizing Maps

DOI: 10.4236/gep.2018.66008 102 Journal of Geoscience and Environment Protection heterogeneous field that makes aerosol characterization real challenge [1] [2]. Despite this, recent initiatives by organizations such as NASA among others have increasingly deployed a number of passive remote sensing platforms that provide systematic and accurate long-term measurements of aerosol characteris- tics over the globe. This initiative hasn’t been reciprocated adequately by the science community since a large percentage of the data actually used is low, in part because of a lack of efficient and effective analysis tools. For example, less than 5% of all remotely sensed images are ever viewed by human eyes or actually used [3]. Therefore, the increasing quantity and type of data available for climate change research studies among them atmospheric aerosols require effective fea- ture extraction methods such as self-organizing map (SOM) and the growing hierarchical self-organizing map (GHSOM). Additionally, accurate extraction of key features and characteristic patterns of variability from a large data set is vital to correctly monitor atmospheric processes and how they alter climate change [4].
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Identification of secondary fatty alcohols in atmospheric aerosols in temperate forests

Identification of secondary fatty alcohols in atmospheric aerosols in temperate forests

different deciduous forest sites in Japan. Fatty diols, such as n-heptacosan-5,10-diol, were identified in atmospheric aerosols for the first time. Among the identified SFAs, n- nonacosan-10-ol was the most abundant compound, followed by n-nonacosan-5-10-diol at both of the forest sites. Con- centrations of the SFAs exhibited distinct seasonal variation, with pronounced peaks during the growing season at each forest site. The SFAs showed significant correlation with su- crose, which is used as a molecular tracer of pollen. A signif- icant fraction of the SFAs was attributed to the submicrome- ter particles in the growing season. The results indicate that they originated mostly from plant waxes and could be used as useful tracers for primary biological aerosol particles.
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The Semi-Volatile Fraction of Atmospheric Aerosols

The Semi-Volatile Fraction of Atmospheric Aerosols

Atmospheric aerosols are solid or liquid particulate matter made up of a mixture of organic and inorganic compounds and water. The organic fraction can make up anywhere from 20-90% of the total aerosol. 1 This matter is suspended in the atmosphere where its potential effects are of concern. Atmospheric aerosols can negatively influence climate as well as human health. In fact, a total of 1-2% of all deaths in the developed world are caused from breathing particulate matter. 2 The Department of Health has demonstrated the significance of air quality and the consequences that particulate matter can pose. 3 The effect organic aerosols have on both climate and health is determined in part by their chemical composition. Therefore, it is important to understand the
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Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

Abstract. Various vibrational modes present in molecular mixtures of laboratory and atmospheric aerosols give rise to complex Fourier transform infrared (FT-IR) absorption spec- tra. Such spectra can be chemically informative, but they often require sophisticated algorithms for quantitative char- acterization of aerosol composition. Naïve statistical cali- bration models developed for quantification employ the full suite of wavenumbers available from a set of spectra, lead- ing to loss of mechanistic interpretation between chemical composition and the resulting changes in absorption patterns that underpin their predictive capability. Using sparse repre- sentations of the same set of spectra, alternative calibration models can be built in which only a select group of absorp- tion bands are used to make quantitative prediction of various aerosol properties. Such models are desirable as they allow us to relate predicted properties to their underlying molecu- lar structure. In this work, we present an evaluation of four algorithms for achieving sparsity in FT-IR spectroscopy cal- ibration models. Sparse calibration models exclude unnec- essary wavenumbers from infrared spectra during the model building process, permitting identification and evaluation of the most relevant vibrational modes of molecules in com- plex aerosol mixtures required to make quantitative predic- tions of various measures of aerosol composition. We study two types of models: one which predicts alcohol COH, car- boxylic COH, alkane CH, and carbonyl CO functional group (FG) abundances in ambient samples based on laboratory calibration standards and another which predicts thermal op- tical reflectance (TOR) organic carbon (OC) and elemental
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An automated baseline correction protocol for infrared spectra of atmospheric aerosols collected on polytetrafluoroethylene (Teflon) filters

An automated baseline correction protocol for infrared spectra of atmospheric aerosols collected on polytetrafluoroethylene (Teflon) filters

ternative scenarios relevant to climate change adaptation or policy decision-making (Drouet et al., 2015; Monks et al., 2009; Isaksen et al., 2009; Goldstein and Galbally, 2007; Kanakidou et al., 2005). Atmospheric aerosols, or particu- late matter (PM), occur as complex mixtures of inorganic salts, crustal elements, sea spray, organic compounds, black carbon, and water (Seinfeld and Pandis, 2006), and a combi- nation of analytical techniques are required to resolve their physical and chemical characteristics (Kulkarni et al., 2011). A useful and relatively inexpensive strategy is to collect at- mospheric aerosol particles onto a substrate for offline anal- ysis in the laboratory. Amongst different substrates, polyte- trafluoroethylene (PTFE) filters have been extensively used in both measurement campaigns (Maria et al., 2002, 2003; Takahama et al., 2011; Frossard et al., 2014; Russell, 2003) and routine monitoring networks, such as the IMPROVE net- work in pristine and rural areas or the Chemical Speciation Network/Speciation Trends Network in urban and suburban areas in the United States (Dillner and Takahama, 2015a). Advantages of PTFE substrates include their stability, hy- drophobicity, and negligible carbon gas adsorption (Turpin et al., 1994; Gilardoni et al., 2007; Ruthenburg et al., 2014). As such, they are amenable to gravimetric mass, elemental analysis, and detailed chemical speciation analysis (e.g., Sur- ratt et al., 2007).
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Optical properties of atmospheric aerosols using filter-based absorption photometers

Optical properties of atmospheric aerosols using filter-based absorption photometers

Size is the most fundamental property of an aerosol particle and there is always a distribution of differently sized particles in the atmosphere. Size determines the dynamics of aerosol particles, how they interact with light, and whether they can act as CCN (Heintzenberg 1989, Andreae and Rosenfeld 2008, Moosmüller et al. 2009). Aerosol particles are larger than the molecules of air that suspend them and small enough to be suspended without being quickly removed by gravitational settling. Thus aerosol particles range in size from a nanometer to roughly 100 μm. Particles with a size of less than 1 μm are classified as fine-mode particles, whereas larger particles are classified as coarse-mode particles (Seinfeld and Pandis 2006). The fine mode can be further divided into a cluster mode (1–3 nm), a nucleation mode (3–25 nm), an Aitken mode (25–100 nm), and an accumulation mode (100–1000 nm) (Kulmala et al. 2001, Seinfeld and Pandis 2006, Kulmala et al. 2007, Kulmala et al. 2012). This division is made because the different modes are governed by different physical processes. The fine and coarse modes comprise aerosol particles with different origins. Atmospheric aerosols can be introduced into the atmosphere directly as particles called primary aerosol particles; they are not formed in the atmosphere. Secondary aerosol particles, however, are formed in the atmosphere from gas-phase precursors.
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Determination of the Effects of Kelvin Radii and Bulk hygroscopicity on Atmospheric Aerosols Using MVN mix Ratios

Determination of the Effects of Kelvin Radii and Bulk hygroscopicity on Atmospheric Aerosols Using MVN mix Ratios

uture climate predictions over the next century remain scientific goal for most of the earth science community. Uncertainty in predicting climate change at 2100 mainly lies in the uncertainty associated with feedbacks in the carbon cycle (Gregory et al., 2009) and aerosol forcing (Forster et al., 2007). These feedbacks are the results of both natural and anthropogenic of land-atmosphere-ocean interactions. Atmospheric aerosols are suspended liquid or solid particles in the atmosphere originating from both natural and anthropogenic activities, affect local radiative forcing by scattering and absorbing of terrestrial radiation, thus, affects radiation balance of the earth and climate (Hess et. al., 1998). Radiative properties of clouds depend on the size and number concentration of droplets, which is governed by atmospheric conditions, such as the number of cloud condensation nuclei (CCN) and the supersaturation of water. The ambient relative humidity changes the microphysical and optical properties of hygroscopic atmospheric aerosols (Cheng et al., 2008), such as sea-salts and water soluble. These ambient atmospheric aerosols are external and internal mixtures of particles with different chemical compounds such as soot, sulphate, nitrate, organic carbon and mineral dust. The state of mixing of these components is crucial for understanding the role of aerosol particles in the atmosphere, As the ambient relative humidity (RH) changes, hygroscopic atmospheric aerosols can undergo phase transformation, droplet growth, and evaporation. Phase transformation from a solid particle to a saline droplet usually occurs spontaneously when the RH reaches a level called the deliquescence humidity and its values depend also on the chemical composition of the aerosol particle (Orr et al. 1958; Tang 1976). The chemical composition of aerosol undergoes spatio-temporal changes, hence characteristics such as Kelvin radii (Kelvin effects) and bulk hygroscopicity factors (water activities) are significantly different from places and particles (Mochida et al.,
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Natural convection and entropy generation of ultrafine atmospheric aerosols in the presence of hydrodynamic partial slip and thermal radiation due to solar energy

Natural convection and entropy generation of ultrafine atmospheric aerosols in the presence of hydrodynamic partial slip and thermal radiation due to solar energy

Figure 5 illustrates the variation in rates of the average Nusselt number and entropy generation due to adding minor volume fraction of nanoparticles and applying partial slip boundary conditions. Fig- ure 5(a) elucidates that adding high thermal conductive nanoparticles to the base uid increases heat transfer, whereby all Nu values are larger than zero. Mean- while, after an enhancement of the average Nusselt number due to applied partial slip boundary condi- tions, Nu values are insensitive to variation of values. Figure 5(b) shows that the inuence of nanopar- ticles on the average entropy generation is reduced by applying partial slip boundary conditions. Figure 5(c) depicts the eect of solid volume fraction of nanopar- ticles on the heat transfer enhancement rate due to applied partial slip boundary conditions. It can be seen that Nu y values increase greatly when 2% more nanoparticles are added to the nanouid. The existence of ultrane atmospheric aerosols has also developed the entropy generation reduction rate due to applying
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Theory of the Scattering Phase Matrix Determination for Atmospheric Aerosols

Theory of the Scattering Phase Matrix Determination for Atmospheric Aerosols

A theoretical foundation is presented for the experimental determination of the scattering-phase matrix for spherical aerosols. In this paper we present a calculation of the angular distribution of light for the atmospheric aerosols. Scattered light patterns produced by spherical transparent particles of a wide range of diameters and for a useful range of forward scattering angles (0-360 o ) are calculated by using Lorenz-

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Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: systematic intercomparison of calibration methods for US measurement network samples

Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: systematic intercomparison of calibration methods for US measurement network samples

The essential principle of the technique is to record chemi- cally specific absorption bands resulting from dipole moment transitions induced by interaction of molecular vibrations with mid-IR radiation (Harris and Bertolucci, 1989). Quanti- tative analysis of spectra is based on the Beer–Lambert law, which ascribes a linear relationship between the abundance of a substance and the mid-IR absorbance at wavenumbers corresponding to the vibrational modes of discriminating molecular bonds (Griffiths and Haseth, 2007). However, this task is confronted with several challenges. Condensed-phase spectra can have broad, overlapping absorption bands due not only to irreducible decay of excited vibrational states (life- time broadening), but also to the slight variations in resonant frequencies of similar bonds interacting with local environ- ments (heterogeneous broadening) (Kelley, 2013). Absorp- tion intensities of the same FG can additionally vary accord- ing to the neighboring substituents of each FG (Allen and Palen, 1989; Maria et al., 2003). These issues are particularly salient in environmental samples, which contain a large num- ber of bonds of the same type in different configurations. Ad- ditionally, inorganic salts such as ammonium nitrate and sul- fate have absorption bands in the mid-IR (Cunningham et al., 1974; McClenny et al., 1985; Pollard et al., 1990; Krost and McClenny, 1994) and can interfere with organic FG analy- sis. Furthermore, given that atmospheric aerosols are com- plex mixtures containing thousands of different compound types (Hamilton et al., 2004; Kroll et al., 2011), strategies for characterization have been based on what we can inter- pret from simpler laboratory mixtures.
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Two-wavelength thermal–optical determination of light-absorbing carbon in atmospheric aerosols

Two-wavelength thermal–optical determination of light-absorbing carbon in atmospheric aerosols

In the wider landscape of atmospheric carbonaceous aerosol, despite a worldwide diffused effort, the situation is not satisfactory and a standardized and conclusive approach is still missing. The quantitative determination of total, or- ganic, and elemental carbon (TC, OC, and EC) is often per- formed by a thermal–optical analysis (Birch and Cary, 1996; Watson et al., 2005; Hitzenberger et al., 2006) of aerosol samples collected on quartz-fiber filters. However, thermal– optical analyses are affected by several issues and artifacts (Yang and Yu, 2002; Chow et al., 2004) and different lab- oratories/agencies adopt protocols which systematically re- sult in discrepancies, particularly large in the EC quantifica- tion (Birch and Cary, 1996; Chow et al., 2007; Cavalli et al., 2010). A further issue arises when the effects of the possible presence of BrC in the sample are taken into account. So far, the monitoring of the sample transmittance during the ther- mal cycle has been introduced to correct for the well-known charring effect and the formation of pyrolytic carbon (Birch and Cary, 1996). This implies that BC is the sole absorbing compound at the wavelength implemented in the thermal– optical analyzer (for instance at λ = 635 nm, the wavelength of the laser diode mounted in the extremely diffused Sun- set Lab. Inc. EC–OC analyzer). Basically, with a sizeable concentration of BrC in the sample, one of the key assump- tions of the thermal–optical methods fails and the EC–OC separation is even more unstable (not to say that, by de- sign, the BrC quantification is not possible). This issue was preliminarily addressed by Chen et al. (2015) by a multi- wavelength thermal–optical reflectance and thermal–optical transmittance (TOR–TOT) instrument (thermal spectral anal- ysis – TSA) and further investigated in Massabò et al. (2016). In the latter work, a method to correct the results of a stan- dard Sunset analyzer and to retrieve the BrC concentration in the sample was introduced. The achievement was possi- ble thanks to a synergy with the information provided by the multi-wavelength absorbance analyzer, MWAA (Massabò et al., 2015) developed in the same laboratory. A further step towards BrC quantification through the utilization of TSA was discussed in Chow et al. (2018), where it was proven that the use of seven wavelengths in thermal–optical carbon analysis allows contributions from biomass burning and sec- ondary organic aerosols to be estimated. It is worth noting that the biomass burning contribution to PM concentration can also be estimated by other methods such as aerosol mass spectrometry, AMS (Daellenbach et al., 2016).
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Assessment of Potential Toxic Fraction in Atmospheric Aerosols in Rural Environment Salve P.R., Wate S.R. and Krupadam R.J.*

Assessment of Potential Toxic Fraction in Atmospheric Aerosols in Rural Environment Salve P.R., Wate S.R. and Krupadam R.J.*

Concentration profile of PAHs: The fluorescence responsive PAHs found in PM10 are (Ace), (Flu), (Phen), (Pyr), (Chr), (Anth), (BaP) and (Flt).The concentration of total PAHs ranged between 2.67-17 ng m -3 during winter, summer and post- monsoon season respectively. The concentration of total PAHs in winter showed highest concentration (17 ng m -3 ). During summer, the PAHs concentration ranged between 2.51-3.79 ng m -3 with an average of 2.96 ng m -3 . In post-monsoon season, the concentration of total PAHs ranged between 1.63-3.59 ng m -3 with an average of 2.74 ng m -3 . In all the seasons, the low molecular weight PAHs compounds concentration was observed to be low which may be due to higher tendency to evaporate. These PAHs compounds have a high vapor pressure and also have tendency to exist in the gas phase, thus easily evaporated as compared to higher PAHs. The low molecular weight PAHs which were lighter tend to remain in the gaseous phase than the particulate phase aerosols 11 .
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Quantitative sampling and analysis of trace elements in atmospheric aerosols: impactor characterization and Synchrotron-XRF mass calibration

Quantitative sampling and analysis of trace elements in atmospheric aerosols: impactor characterization and Synchrotron-XRF mass calibration

Abstract. Identification of trace elements in ambient air can add substantial information to pollution source apportion- ment studies, although they do not contribute significantly to emissions in terms of mass. A method for quantitative size and time-resolved trace element evaluation in ambient aerosols with a rotating drum impactor and synchrotron ra- diation based X-ray fluorescence is presented. The impactor collection efficiency curves and size segregation characteris- tics were investigated in an experiment with oil and salt par- ticles. Cutoff diameters were determined through the ratio of size distributions measured with two particle sizers. Further- more, an external calibration technique to empirically link fluorescence intensities to ambient concentrations was devel- oped. Solutions of elemental standards were applied with an ink-jet printer on thin films and area concentrations were subsequently evaluated with external wet chemical methods. These customized and reusable reference standards enable quantification of different data sets analyzed under varying experimental conditions.
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Retrieval algorithm for atmospheric aerosols based on multi angle viewing of ADEOS/POLDER

Retrieval algorithm for atmospheric aerosols based on multi angle viewing of ADEOS/POLDER

1996 and in January and April, 1997. Our results coincide with the aerosol map derived from OCTS radiance data by Nakajima et al. (1999). It is interesting to note that these global distributions represent several characteristic pattern of aerosols on a world-wide scale. Husar (Husar et al., 1997) mentioned that a high concentration of aerosols is seen over the Gulf of Guinea throughout the year. These aerosols seem to be dust-originated particles from the Sahara desert. Our results also indicate large values of τ a over the Gulf of Guinea

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An Overview of Hand held Sun Photometer Measurements of Atmospheric Aerosols

An Overview of Hand held Sun Photometer Measurements of Atmospheric Aerosols

data shows that the AOT for green light drops continuously from September to January and 154. then picks up in February[r]

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Significant Climate Impact of Highly Hygroscopic Atmospheric Aerosols in Delhi, India

Significant Climate Impact of Highly Hygroscopic Atmospheric Aerosols in Delhi, India

supersaturation of ~0.51±0.04% (Delhi), ~0.70% (Europe and North America), 0.80-0.92% (Asia, Australia, South America and Africa), and ~0.85% (Beijing), respectively. Therefore, the CCN activation ability of aerosols in Delhi is much higher than the continental averages and another Asian megacity, Beijing. This indicates a larger impact of aerosols in Delhi on climate and hydrologic cycle, even if under same meteorologic conditions and same particle number concentration. Additionally, the frequent influence of monsoon and great PM 2.5

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Seasonal Variability of Atmospheric Aerosols in Karachi, Pakistan

Seasonal Variability of Atmospheric Aerosols in Karachi, Pakistan

meteorological parameters and emissions from industrial and indiscriminate solid waste burning and the most important source of black carbon emissions in Karachi was vehicular traffic. Aerosols in terms of Aerosol Optical Depth (AOD) from AERONET and MODIS satellites showed similar trends as that of black carbon. Aeronet 500nm. AODs were maximum for July (0.95 monsoon) and minimum (around 0.4) in November-February. However, changes in spectral dependency were uncertain. This also implied that a columnar spectral optical depth represents a different aerosol type associated with having advection from various directions and sources. Seasonal AOD maps obtained from MODIS for Karachi also confirm the AOD seasonal trend as stated in case of Aeronet and in situ Aethalometer measurements.
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