scholarly journals Relationship between the Optical Properties and Chemical Composition of Urban Aerosol Particles in Lithuania

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Julija Pauraite ◽  
Kristina Plauškaitė ◽  
Vadimas Dudoitis ◽  
Vidmantas Ulevicius
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Organic Aerosol ◽  
Single Scattering ◽  
Chemical Compositions ◽  
Spectra Analysis ◽  
Average Value ◽  
Aerosol Mass ◽  
In Situ Investigation

In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.

scholarly journals Hygroscopicity and composition of Alaskan Arctic CCN during April 2008

2011 ◽  
Vol 11 (8) ◽  
pp. 21789-21834
Author(s):  
R. H. Moore ◽  
R. Bahreini ◽  
C. A. Brock ◽  
K. D. Froyd ◽  
J. Cozic ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Anthropogenic Pollution ◽  
Organic Aerosol ◽  
International Polar Year ◽  
Mass Spectral ◽  
Aerosol Mass ◽  
Alaskan Arctic ◽  
Air Mass Types ◽  
The Individual

Abstract. We present a comprehensive characterization of cloud condensation nuclei (CCN) sampled in the Alaskan Arctic during the 2008 Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project, a component of the POLARCAT and International Polar Year (IPY) initiatives. Four distinct air mass types were sampled including relatively pristine Arctic background conditions as well as biomass burning and anthropogenic pollution plumes. Despite differences in chemical composition, inferred aerosol hygroscopicities were fairly invariant and ranged from κ = 0.1–0.3 over the atmospherically-relevant range of water vapor supersaturations studied. Analysis of the individual mass spectral m/z 43 and 44 peaks from an aerosol mass spectrometer show the organic aerosols sampled to be well-oxygenated, consistent with with long-range transport and aerosol aging processes. However, inferred hygroscopicities are less than would be predicted based on previous parameterizations of biogenic oxygenated organic aerosol, suggesting an upper limit on organic aerosol hygroscopicity above which κ is less sensitive to the O:C ratio. Most Arctic aerosol act as CCN above 0.1 % supersaturation, although the data suggest the presence of an externally-mixed, non-CCN-active mode comprising approximately 0–20 % of the aerosol number. CCN closure was assessed using measured size distributions, bulk chemical composition measurements, and assumed aerosol mixing states; CCN predictions tended toward overprediction, with the best agreement (± 0–20 %) obtained by assuming the aerosol to be externally-mixed with soluble organics. Closure also varied with CCN concentration, and the best agreement was found for CCN concentrations above 100 cm−3 with a 1.5- to 3-fold overprediction at lower concentrations.

scholarly journals Processing of biomass burning aerosol in the Eastern Mediterranean during summertime

2013 ◽  
Vol 13 (10) ◽  
pp. 25969-25999 ◽  
Author(s):  
A. Bougiatioti ◽  
I. Stavroulas ◽  
E. Kostenidou ◽  
P. Zarmpas ◽  
C. Theodosi ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Biomass Burning ◽  
Eastern Mediterranean ◽  
Late Summer ◽  
Organic Aerosol ◽  
High Temporal Resolution ◽  
Night Time ◽  
Air Masses ◽  
Aerosol Mass ◽  
Atmospheric Processing

Abstract. The aerosol chemical composition in air masses affected by wildfires from the Greek islands of Chios, Euboea and Andros, the Dalmatian Coast and Sicily, during late summer of 2012 was characterized at the remote background site of Finokalia, Crete. Air masses were transported several hundreds of kilometers, arriving at the measurement station after approximately half a day of transport, mostly during night-time. The chemical composition of the particulate matter was studied by different high temporal resolution instruments, including an Aerosol Chemical Speciation Monitor (ACSM) and a seven-wavelength aethalometer. Despite the large distance from emission and long atmospheric processing, a clear biomass burning organic aerosol (BBOA) profile containing characteristic markers is derived from BC measurements and Positive Matrix Factorization (PMF) analysis of the ACSM mass spectra. The ratio of fresh to aged BBOA decreases with increasing atmospheric processing time and BBOA components appear to be converted to oxygenated organic aerosol (OOA). Given that the smoke was mainly transported overnight, it appears that the processing can take place in the dark. These results show that a significant fraction of the BBOA loses its characteristic AMS signature and is transformed to OOA in less than a day. This implies that biomass burning can contribute almost half of the organic aerosol mass in the area during summertime.

Optical Properties of Secondary Organic Aerosol from cis-3-Hexenol and cis-3-Hexenyl Acetate: Effect of Chemical Composition, Humidity, and Phase

2016 ◽  
Vol 50 (10) ◽  
pp. 4997-5006 ◽  
Author(s):  
Rebecca M. Harvey ◽  
Adam P. Bateman ◽  
Shashank Jain ◽  
Yong Jie Li ◽  
Scot Martin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Hexenyl Acetate

scholarly journals Intercomparison of biomass burning aerosol optical properties from in situ and remote-sensing instruments in ORACLES-2016

2019 ◽  
Vol 19 (14) ◽  
pp. 9181-9208 ◽  
Author(s):  
Kristina Pistone ◽  
Jens Redemann ◽  
Sarah Doherty ◽  
Paquita Zuidema ◽  
Sharon Burton ◽  
...  
Keyword(s):  
Optical Properties ◽  
Case Studies ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Measurement Techniques ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Biomass Burning Aerosol

Abstract. The total effect of aerosols, both directly and on cloud properties, remains the biggest source of uncertainty in anthropogenic radiative forcing on the climate. Correct characterization of intensive aerosol optical properties, particularly in conditions where absorbing aerosol is present, is a crucial factor in quantifying these effects. The southeast Atlantic Ocean (SEA), with seasonal biomass burning smoke plumes overlying and mixing with a persistent stratocumulus cloud deck, offers an excellent natural laboratory to make the observations necessary to understand the complexities of aerosol–cloud–radiation interactions. The first field deployment of the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign was conducted in September of 2016 out of Walvis Bay, Namibia. Data collected during ORACLES-2016 are used to derive aerosol properties from an unprecedented number of simultaneous measurement techniques over this region. Here, we present results from six of the eight independent instruments or instrument combinations, all applied to measure or retrieve aerosol absorption and single-scattering albedo. Most but not all of the biomass burning aerosol was located in the free troposphere, in relative humidities typically ranging up to 60 %. We present the single-scattering albedo (SSA), absorbing and total aerosol optical depth (AAOD and AOD), and absorption, scattering, and extinction Ångström exponents (AAE, SAE, and EAE, respectively) for specific case studies looking at near-coincident and near-colocated measurements from multiple instruments, and SSAs for the broader campaign average over the month-long deployment. For the case studies, we find that SSA agrees within the measurement uncertainties between multiple instruments, though, over all cases, there is no strong correlation between values reported by one instrument and another. We also find that agreement between the instruments is more robust at higher aerosol loading (AOD400>0.4). The campaign-wide average and range shows differences in the values measured by each instrument. We find the ORACLES-2016 campaign-average SSA at 500 nm (SSA500) to be between 0.85 and 0.88, depending on the instrument considered (4STAR, AirMSPI, or in situ measurements), with the interquartile ranges for all instruments between 0.83 and 0.89. This is consistent with previous September values reported over the region (between 0.84 and 0.90 for SSA at 550nm). The results suggest that the differences observed in the campaign-average values may be dominated by instrument-specific spatial sampling differences and the natural physical variability in aerosol conditions over the SEA, rather than fundamental methodological differences.

scholarly journals Mass Extinction Efficiency Approximation for Polydispersed Aerosol Using Harmonic Mean-Type Approximation

2020 ◽  
Vol 10 (23) ◽  
pp. 8637
Author(s):  
Junshik Um ◽  
Seonghyeon Jang ◽  
Young Jun Yoon ◽  
Seoung Soo Lee ◽  
Ji Yi Lee ◽  
...  
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Extinction Coefficient ◽  
Mass Extinction ◽  
Aerosol Particles ◽  
Size Distributions ◽  
Extinction Efficiency ◽  
Type Approximation ◽  
Aerosol Mass ◽  
Mass Extinction Efficiency

Among many parameters characterizing atmospheric aerosols, aerosol mass extinction efficiency (MEE) is important for understanding the optical properties of aerosols. MEE is expressed as a function of the refractive indices (i.e., composition) and size distributions of aerosol particles. Aerosol MEE is often considered as a size-independent constant that depends only on the chemical composition of aerosol particles. The famous Malm’s reconstruction equation and subsequent revised methods express the extinction coefficient as a function of aerosol mass concentration and MEE. However, the used constant MEE does not take into account the effect of the size distribution of polydispersed chemical composition. Thus, a simplified expression of size-dependent MEE is required for accurate and conventional calculations of the aerosol extinction coefficient and also other optical properties. In this study, a simple parameterization of MEE of polydispersed aerosol particles was developed. The geometric volume–mean diameters of up to 10 µm with lognormal size distributions and varying geometric standard deviations were used to represent the sizes of various aerosol particles (i.e., ammonium sulfate and nitrate, elemental carbon, and sea salt). Integrating representations of separate small mode and large mode particles using a harmonic mean-type approximation generated the flexible and convenient parameterizations of MEE that can be readily used to process in situ observations and adopted in large-scale numerical models. The calculated MEE and the simple forcing efficiency using the method developed in this study showed high correlations with those calculated using the Mie theory without losing accuracy.

scholarly journals Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition

2015 ◽  
Vol 8 (1) ◽  
pp. 309-352 ◽  
Author(s):  
E. A. Bruns ◽  
I. El Haddad ◽  
A. Keller ◽  
F. Klein ◽  
N. K. Kumar ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Aerosol ◽  
Emission Factors ◽  
Smog Chamber ◽  
Wood Combustion ◽  
Flow Reactors ◽  
Aerosol Mass ◽  
Combustion Emissions ◽  
Smog Chambers ◽  
Composition Of Products

Abstract. A variety of tools are used to simulate atmospheric aging, including smog chambers and flow reactors. Traditional, large-scale smog chambers age emissions over the course of hours to days, whereas flow reactors rapidly age emissions using high oxidant concentrations to reach higher degrees of oxygenation than typically attained in smog chamber experiments. The atmospheric relevance of the products generated under such rapid oxidation warrants further study. However, no previously published studies have compared the yields and chemical composition of products generated in flow reactors and smog chambers from the same starting mixture. The yields and composition of the organic aerosol formed from the photo-oxidation of α-pinene and of wood combustion emissions were determined using aerosol mass spectrometry in a smog chamber (SC) and two flow reactors: a potential aerosol mass reactor (PAM) and a micro-smog chamber (MSC). Reactants were sampled from the SC and aged in the MSC and PAM using a range of hydroxyl radical (OH) concentrations and then photo-chemically aged in the SC. The maximum yields/emission factors and the chemical composition of the products in both the α-pinene and wood combustion systems determined with the PAM and SC agreed reasonably well. High OH exposures have been shown previously to lower yields by breaking carbon-carbon bonds and forming higher volatility species, which reside largely in the gas phase, however, fragmentation in the PAM was not observed. The yields determined using the PAM for the α-pinene system were slightly lower than in the SC, possibly from increased wall losses of gas-phase species due to the higher surface area to volume ratios in the PAM, even when offset with better isolation of the sampled flow from the walls. The α-pinene SOA results for the MSC were not directly comparable, as particles were smaller than the optimal AMS transmission range. For the wood combustion system, emission factors measured by the MSC were typically lower than those from the SC, possibly due to nucleation mode particles not observed by the AMS or the condensational loss of gases to the walls inside or after the MSC. The chemical composition of products in the flow reactors and SC were in reasonable agreement in both systems. The emission factors determined using the flow reactors increased relative to the SC when the wood combustion emissions contained higher fractions of aromatic compounds, suggesting that the performance of the flow reactors may be dependent on the chemical composition of the reactants.

scholarly journals Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods

2018 ◽  
Author(s):  
Liqing Hao ◽  
Olga Garmash ◽  
Mikael Ehn ◽  
Pasi Miettinen ◽  
Paola Massoli ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Atmospheric Chemistry ◽  
Mass Fraction ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Sulfate Aerosol ◽  
Organic Mass ◽  
Night Time ◽  
Aerosol Mass

Abstract. Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols-Effects on Clouds and Climate) campaign was conducted during the spring 2014 at SMEAR II station (Station for Measuring Forest Ecosystem-Aerosol Relations) in Finland. The particles were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A PBL (planetary boundary layer) dilution model was developed to assist interpreting the measurement results. Right before nucleation events, the mass concentrations of organic and sulfate aerosol species were both decreased rapidly along with the growth of PBL heights. However, the mass fraction of sulfate aerosol of the total aerosol mass was increased, in contrast to a decrease for the organic mass fraction. Meanwhile, an increase of LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the total organic mass was observed, in distinct comparison to a reduction of SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at the beginning of nucleation events, the observed sulfate aerosol mass was mainly driven by vertical turbulent mixing of sulfate-rich aerosols between the residual layer and the newly formed boundary layer, while the condensation of sulfuric acid played a minor role in interpreting the measured sulfate mass concentration. For the measured organic aerosols, their temporal profiles were mainly driven by dilution from PBL development, organic aerosol mixing in different boundary layers and/or condensation of organic vapors, but accurate measurements of organic vapor concentrations and characterization on the spatial aerosol chemical composition are required. In general, the observed aerosol particles by AMS are subjected to joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in different boundary layers. During aerosol growth periods in the night time, the mass concentrations of organic aerosols and organic nitrate aerosols were both increased. The increase of SVOOA mass correlated well with the calculated increase of condensed HOMs (highly oxygenated organic molecules) mass. To our knowledge, our results are the first atmospheric observations showing a connection between increase in SVOOA and condensed HOMs during the night time.

scholarly journals Effect of oxidant concentration, exposure time, and seed particles on secondary organic aerosol chemical composition and yield

2015 ◽  
Vol 15 (6) ◽  
pp. 3063-3075 ◽  
Author(s):  
A. T. Lambe ◽  
P. S. Chhabra ◽  
T. B. Onasch ◽  
W. H. Brune ◽  
J. F. Hunter ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Short Exposure ◽  
Heterogeneous Oxidation ◽  
Seed Particles ◽  
Aerosol Mass ◽  
Environmental Chambers

Abstract. We performed a systematic intercomparison study of the chemistry and yields of secondary organic aerosol (SOA) generated from OH oxidation of a common set of gas-phase precursors in a Potential Aerosol Mass (PAM) continuous flow reactor and several environmental chambers. In the flow reactor, SOA precursors were oxidized using OH concentrations ranging from 2.0 × 108 to 2.2 × 1010 molec cm−3 over exposure times of 100 s. In the environmental chambers, precursors were oxidized using OH concentrations ranging from 2 × 106 to 2 × 107 molec cm−3 over exposure times of several hours. The OH concentration in the chamber experiments is close to that found in the atmosphere, but the integrated OH exposure in the flow reactor can simulate atmospheric exposure times of multiple days compared to chamber exposure times of only a day or so. In most cases, for a specific SOA type the most-oxidized chamber SOA and the least-oxidized flow reactor SOA have similar mass spectra, oxygen-to-carbon and hydrogen-to-carbon ratios, and carbon oxidation states at integrated OH exposures between approximately 1 × 1011 and 2 × 1011 molec cm−3 s, or about 1–2 days of equivalent atmospheric oxidation. This observation suggests that in the range of available OH exposure overlap for the flow reactor and chambers, SOA elemental composition as measured by an aerosol mass spectrometer is similar whether the precursor is exposed to low OH concentrations over long exposure times or high OH concentrations over short exposure times. This similarity in turn suggests that both in the flow reactor and in chambers, SOA chemical composition at low OH exposure is governed primarily by gas-phase OH oxidation of the precursors rather than heterogeneous oxidation of the condensed particles. In general, SOA yields measured in the flow reactor are lower than measured in chambers for the range of equivalent OH exposures that can be measured in both the flow reactor and chambers. The influence of sulfate seed particles on isoprene SOA yield measurements was examined in the flow reactor. The studies show that seed particles increase the yield of SOA produced in flow reactors by a factor of 3 to 5 and may also account in part for higher SOA yields obtained in the chambers, where seed particles are routinely used.

scholarly journals Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case

2003 ◽  
Vol 3 (6) ◽  
pp. 1903-1917 ◽  
Author(s):  
M. G. Iziomon ◽  
U. Lohmann
Keyword(s):  
Optical Properties ◽  
Great Plains ◽  
Single Scattering ◽  
Aerosol Concentration ◽  
Carbonaceous Aerosols ◽  
Radiative Effect ◽  
Mean Values ◽  
Submicron Aerosol ◽  
Aerosol Mass ◽  
A Minor

Abstract. A multi-year field measurement analysis of the characteristics and direct radiative effect of aerosols at the Southern Great Plains (SGP) central facility of the Atmospheric Radiation Measurement (ARM) Program is presented. Inter-annual mean and standard deviation of submicrometer scattering fraction (at 550 nm) and Ångström exponent å (450 nm, 700 nm) at the mid-latitude continental site are indicative of the scattering dominance of fine mode aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal variation of submicron aerosol concentration to coagulation, photochemistry and the evolution of the boundary layer. Precipitation does not seem to play a role in the observed afternoon maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer (12.1±6.7mg m-3), with the summer value being twice that in the winter. Of the chemically analyzed ionic components (which exclude carbonaceous aerosols), SO4= and NH4+ constitute the dominant species at the SGP seasonally, contributing 23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The single scattering albedo w0 shows the most remarkable distinction between the two aerosol constituents. We also present aircraft measurements of vertical profiles of aerosol optical properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light scattering coefficient. Column-averaged and surface annual mean values of hemispheric backscatter fraction (at 550 nm), w0 (at 550 nm) and å (450 nm, 700 nm) agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring) at the ARM site

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