Andrew T. Lambe’s research while affiliated with Aerodyne Research, Inc. and other places

What is this page?


This page lists works of an author who doesn't have a ResearchGate profile or hasn't added the works to their profile yet. It is automatically generated from public (personal) data to further our legitimate goal of comprehensive and accurate scientific recordkeeping. If you are this author and want this page removed, please let us know.

Publications (41)


Characterizing Atmospheric Oxidation and Cloud Condensation Nuclei Activity of Polystyrene Nanoplastic Particles
  • Article

May 2025

·

7 Reads

Environmental Science and Technology

Sahir Gagan

·

Alana J Dodero

·

Miska Olin

·

[...]

·

Nanoplastic particles (NPPs) are emerging anthropogenic pollutants and have been detected in urban, rural, and remote areas. Characterizing the lifetime, fate, and cloud-forming potential of atmospheric NPPs improves our understanding of their environmental processes and climate impacts. This study provides the first quantified heterogeneous reaction rate and lifetime of polystyrene (PS) NPPs against common atmospheric oxidants. The atomized PS NPPs were introduced to a Potential Aerosol Mass (PAM) oxidation flow reactor with ·OH exposure of 0 to 1.5 × 10¹² molecules cm–3 s, equivalent to atmospheric exposure from 0 to 18 days, assuming an ambient ·OH concentration of 1 × 10⁶ cm–3. The decay of the PS mass concentration was quantified by monitoring tracer ions, C6H6 ⁺ (m/z 78) and C8H8 ⁺ (m/z 104), by using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The pseudo-first-order rate constant of PS particles reacting with ·OH, k OH, was determined to be (3.2 ± 0.7) × 10–13 cm³ molecule–1 s–1, equivalent to a half-lifetime of a few hours to ∼80 days in the atmosphere, depending on particle sizes and hydroxyl radical concentrations. The hygroscopicity of 100 nm PS NPPs at different ·OH exposure levels was quantified using a cloud condensation nuclei counter (CCNC), showing a twofold increase of hygroscopicity parameter upon 27 days of atmospheric photooxidation.



A comprehensive evaluation of enhanced temperature influence on gas and aerosol chemistry in the lamp-enclosed oxidation flow reactor (OFR) system
  • Preprint
  • File available

November 2023

·

111 Reads

Oxidation flow reactors (OFRs) have been widely used to investigate the formation of secondary organic aerosol (SOA). However, the UV lamps that are commonly used to initiate photochemistry in OFRs can lead to increases in the reactor temperature with consequences that have not been assessed in detail. In this study, we systematically investigated the temperature distribution inside an Aerodyne Potential Aerosol Mass OFR and the associated impacts on flow and chemistry arising from lamp heating. A lamp-induced temperature enhancement was observed, which was a function of lamp driving voltage, number of lamps, lamp types, OFR residence time, and positions inside OFR. Under common OFR operational conditions (e.g., < 5 days of equivalent atmospheric OH exposure under low-NOx conditions), the temperature enhancement was usually within 1–5 °C. Under extreme (but less commonly used) settings, the heating could reach 15 °C. The influence of the increased temperature over ambient conditions on the flow distribution, gas, and condensed phase chemistry inside OFR was evaluated. We found that the increase in temperature changes the flow field, leading to a reduced tail on the residence time distribution and corresponding oxidant exposure due to faster recirculation. According to simulation results from a box model using radical chemistry, the variation of absolute oxidant concentration inside of OFR due to temperature increase was small (<5 %). The temperature influences on existing and newly formed OA were also investigated, suggesting that the increase in temperature can impact the yield, size, and oxidation levels of representative biogenic and anthropogenic SOA types. Recommendations for temperature-dependent SOA yield corrections and OFR operating protocols that mitigate lamp-induced temperature enhancement and fluctuations are presented. We recommend blowing air around the outside of the reactor with fans during OFR experiments to minimize the temperature increase inside OFR. Temperature increases are substantially lower for OFRs using less powerful lamps than the Aerodyne version.

Download

Technical note: Gas-phase nitrate radical generation via irradiation of aerated ceric ammonium nitrate mixtures

July 2023

·

61 Reads

We present a novel photolytic source of gas-phase NO3 suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize NO2 + O3 reactions and/or thermal dissociation of dinitrogen pentoxide (N2O5). The method generates NO3 via irradiation of aerated aqueous solutions of ceric ammonium nitrate ((NH4)2Ce(NO3)6, “CAN”) and nitric acid (HNO3) or sodium nitrate (NaNO3). We present experimental and model characterization of the NO3 formation potential of irradiated CAN/HNO3 and CAN/NaNO3 mixtures containing [CAN] = 10−3 to 1.0 M, [HNO3] = 1.0 to 6.0 M, [NaNO3] = 1.0 to 4.8 M, photon fluxes (I) ranging from 6.9×1014 to 1.0×1016 photons cm−2 s−1, and irradiation wavelengths ranging from 254 to 421 nm. NO3 mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [NO3] was achieved using [HNO3] ≈ 3.0 to 6.0 M and UVA radiation (λmax = 369 nm) in CAN/HNO3 mixtures or [NaNO3] ≥ 1.0 M and UVC radiation (λmax = 254 nm) in CAN/NaNO3 mixtures. Other reactive nitrogen (NO2, N2O4, N2O5, N2O6, HNO2, HNO3, HNO4) and reactive oxygen (HO2, H2O2) species obtained from the irradiation of ceric nitrate mixtures were measured using a NOx analyzer and an iodide adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of NO3-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds and secondary organic aerosols from the β-pinene + NO3 reaction using a Filter Inlet for Gases and Aerosols (FIGAERO) coupled to the HR-ToF-CIMS.


Insights into secondary organic aerosol formation from the day- and nighttime oxidation of PAHs and furans in an oxidation flow reactor

July 2023

·

179 Reads

Secondary organic aerosols (SOA) formed by oxidation of typical precursors largely emitted by biomass burning, such as PAHs and furans, are still poorly characterized in terms of formation yields, physical and light absorption properties, particularly those generated at night following reaction with nitrate radicals (NO3). In the present study, we evaluated and compared the formation yields, effective density (ρeff), absorption Ångström exponent (α), and mass absorption coefficient (MAC) of laboratory-generated SOA from three furan compounds (furan, 2-methylfuran, and 2,5-dimethylfuran) and four PAHs (naphthalene, acenaphthylene, fluorene, and phenanthrene). SOA were generated in an oxidation flow reactor from the reaction between hydroxyl radicals (OH; 0.1 - 20 equivalent aging days) or NO3 radicals (0.05 - 6 equivalent aging nights of 14 h) with single furan or PAH. The ρeff, formation yields, α, and MAC of the generated SOA varied depending on the precursor and oxidant considered. The ρeff of SOA formed with OH and NO3 tended to increase with particle size before reaching a “plateau”. This was particularly evident for the nighttime chemistry experiments with NO3 radicals (1.2 to 1.6 on average for particles > 100 nm). Such results highlighted potential differences in the chemical composition of the SOA, as well as probably in their morphology, according to the particle size. Three times lower SOA formation yields were obtained with NO3 compared to OH. The yields of PAH SOA (18 to 76 %) were 5 to 6 times higher than those obtained for furans (3-12 %). While furan SOA showed low or negligible light absorption properties, PAH SOA was found to have a significant impact in the UV-Visible region, implying a significant contribution to atmospheric brown carbon (BrC). No increase in the MAC values was observed from OH to NO3 oxidation processes, probably due to a low formation of nitrogen-containing chromophores through homogeneous gas phase oxidation processes with NO3 only (without NOx). Overall, the results obtained in this work demonstrated that PAHs are significant precursors of SOA emitted by biomass burning, through both, day- and nighttime processes, and have a substantial impact on the aerosol light absorption properties and so probably on climate.



Figure 2. An example of isomers quantified in b) the chromatogram of ion (C9H14O4)I -in CIMS with a) their corresponding FID peaks (highlighted in red). The peaks marked with numbers are those included in the analysis of isomer sensitivity.
Figure 6. Measured moles of a) compounds and b) formulas (i.e., summation of isomers within each formula) in all oxidation experiments vs their fitted moles using the linear regression equation obtained in Figure 5.
Figure 7. Relationship between sensitivities and retention time index of all compounds in oxidation experiments. Black markers are all data equally divided into eight bins based on the ranking of their sensitivity and retention time index, centered on averages with error bars representing the standard deviation of sensitivity and retention time index. The size of the round marker represents the number of moles of each compound.
Figure 8. The relationship between differences (Δ) in log(sensitivity) and retention index for all pairs of isomers with a given formula. Black markers are all data equally divided into eight bins (octiles), centered on averages with error bars representing standard deviations.
Quantification of Isomer-Resolved Iodide CIMS Sensitivity and Uncertainty Using a Voltage Scanning Approach

June 2021

·

173 Reads

Chemical ionization mass spectrometry (CIMS) using iodide as a reagent ion has been widely used to classify organic compounds in the atmosphere by their elemental formula. Unfortunately, calibration of these instruments is challenging due to a lack of commercially available standards for many compounds, which has led to the development of methods for estimating CIMS sensitivity. By coupling a Thermal desorption Aerosol Gas chromatograph (TAG) simultaneously to a flame ionization detector (FID) and an iodide CIMS, we use the individual particle-phase analytes, quantified by the FID, to examine the sensitivity of the CIMS and its variability between isomers of the same elemental formula. Iodide CIMS sensitivities of isomers within a formula are found to generally vary by one order of magnitude with a maximum deviation of two orders of magnitude. Furthermore, we compare directly measured sensitivity to a method of estimating sensitivity based on declustering voltage (i.e., “voltage scanning”). This approach is found to carry high uncertainties for individual analytes (half to one order of magnitude), but represents a central tendency that can be used to estimate the sum of analytes with reasonable error (~30 % differences between predicted and measured moles). Finally, GC retention time, which is associated with vapor pressure and chemical functionality of an analyte, is found to qualitatively correlate with iodide CIMS sensitivity, but the relationship is not close enough to be quantitatively useful and could be explored further in the future as a potential calibration approach.


Figure 2: As with Figure 2, but for NO3,Arizona on 08/22/2019. Based on HYSPLIT back-trajectories, the plume for this experiment was again less than one hour old, though smoke that had settled in the valley under the nocturnal boundary layer may have been older. Background map is from USGS EarthExplorer, and fire map overlays are from the National Wildfire Coordinating Group's Incident Information System (InciWeb).
Figure 3: As with Figures 2 and 3, showing fire ignition point (white triangle), OHOregon and NO3,Oregon experiment locations (white stars), and fire boundary maps for 08/26/2019. HYSPLIT back-trajectories again show the plumes for these experiments were much less than one hour old. Background map is from USGS EarthExplorer, and fire map overlays are from the National Wildfire Coordinating Group's Incident Information System (InciWeb).
Figure 6: Enhancement and depletion of ion families measured by the AMS during NO3• oxidation. CHO1N and CHOgt1N, while present in lower relative abundances, showed the largest enhancement through NO3• oxidation.
Figure 8: Enhancement and depletion of ion families measured by the AMS during OH• oxidation. CHO1N is depleted while CHOgt1N is enhanced, however, both these families are present in low relative abundances which may exaggerate the
Figures and Tables
Diel Cycle Impacts on the Chemical and Light Absorption Properties of Organic Carbon Aerosol from Wildfires in the Western United States

March 2021

·

97 Reads

·

1 Citation

Organic aerosol (OA) emissions from biomass burning have been the subject of intense research in recent years, involving a combination of field campaigns and laboratory studies. These efforts have aimed at improving our limited understanding of the diverse processes and pathways involved in the atmospheric processing and evolution of OA properties, culminating in their accurate parameterizations in climate and chemical transport models. To bring closure between laboratory and field studies, wildfire plumes in the western United States were sampled and characterized for their chemical and optical properties during the ground-based segment of the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign. Using a custom-developed multiwavelength integrated photoacoustic-nephelometer (MIPN) spectrometer in conjunction with a suite of instruments, including an oxidation flow reactor equipped to generate hydroxyl (OH∙) or nitrate (NO3∙) radicals to mimic daytime or nighttime oxidative aging processes, we investigated the effects of multiple equivalent days or nights of OH∙/NO3∙ exposure on the chemical composition and mass absorption cross-sections (MAC(λ)) at 488 and 561 nm of OA emitted from wildfires in Arizona and Oregon. We found that OH∙ exposure reduced the wavelength-dependent MAC(λ) by a factor of 0.72 ± 0.08, consistent with previous laboratory studies. On the other hand, NO3∙ exposure increased it by a factor of up to 1.69 ± 0.38. The MAC enhancement following NO3∙ exposure was correlated with an enhancement in CHO1N and CHOgt1N ion families measured with an aerosol mass spectrometer.


Figure 1. Schematics of the TAG-CIMS/FID interface, with a photo inserted. Details of each instrument are simplified. Restrictive capillaries to each detector are used to balance flows to each detector due to differences in pressure (dimensions and temperatures shown).
Figure 2. Comparison of chromatograms between FID and CIMS from particle sample generated from limonene-O3 reaction. The timeseries signals of CIMS are the analyte total ion counts, which are summation of all ions with the reagent ions removed while signals of FID are single-channel. The signals of both CIMS and FID are normalized to the highest peak in the chromatogram.
Figure 4c is a factor of ten higher than that in Figure 4a). For example, the analyte total ion counts of vanillin (labeled with an arrow, retention time = 965 secs), has a peak height of 1.0×10 5 ions/s in iodide ionization mode while the peak height of vanillin in multi-reagent ionization mode is 8.6×10 5 ions/s. This increase in ions is observed to occur almost entirely through the addition of new chemical pathways. In multi-reagent ionization, the three most abundant ions in the vanillin mass spectrum 335 are deprotonation (i.e., [M-H] -), the cluster with O2 -(i.e., [M+O2] -), and the deprotonated dimer (i.e., [M2-H] -). Because of the presence of oxygen in the reagent ion flow, the abundance of [M-H] -and [M+O2] -is enhanced significantly. Though the [M+I] -is no longer observed in the spectrum, this is only due to the significant increase in other signals; the actual impact on the iodide adduct formation pathway is minor. To demonstrate, we plot the comparisons of the [M-H] -and [M+I] -of vanillin between the two ionization modes in Figure 5. The peak height of the [M-H] -ion of vanillin increases by a factor of 10, from 340
Coupling a gas chromatograph simultaneously to a flame ionization detector and chemical ionization mass spectrometer for isomer-resolved measurements of particle-phase organic compounds

August 2020

·

132 Reads

Atmospheric oxidation products of volatile organic compounds consist of thousands of unique chemicals that have distinctly different physical and chemical properties depending on their detailed structures and functional groups. Measurement techniques that can achieve molecular characterizations with details down to functional groups (i.e., isomer-resolved resolution) are consequently necessary to provide understandings of differences of fate and transport within isomers produced in the oxidation process. We demonstrate a new instrument coupling the thermal desorption aerosol gas chromatograph (TAG), which enables the separation of isomers, with the high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS), which has the capability of classifying unknown compounds by their molecular formulas, and the flame ion detector (FID), which provide a near-universal response to organic compounds. The TAG-CIMS/FID is used to provide isomer-resolved measurements of samples from liquid standard injections and particle-phase organics generated in oxidation flow reactors. By coupling a TAG to a CIMS, the CIMS is enhanced with an additional dimension of information (resolution of individual molecules) at the cost of time resolution (i.e., one sample per hour instead of per minute). We found that isomers are prevalent in sample matrix with an average number of three to five isomers per formula depending on the precursors in the oxidation experiments. Additionally, a multi-reagent ionization mode is investigated in which both zero air and iodide are introduced as reagent ions, to examine the feasibility of extending the use of an individual CIMS to a broader range of analytes with still selective reagent ions. While this approach reduces iodide-adduct ions by a factor of two, [M−H]− and [M+O2]− ions produced from lower-polarity compounds increase by a factor of five to ten, improving their detection by CIMS. The method expands the range of detected chemical species by using two chemical ionization reagents simultaneously, enabled by the pre-separation of analyte molecules before ionization.


Figure 2. O3 mixing ratio generated using OFR185 at I254 = (3.5±0.7)×10 15 photons cm −2 s −1 (lamp types A and C-G) and I254 = 5.8×10 14 photons cm −2 s −1 (lamp type B) as a function of T185 and [H2O]. Error bars represent ±1σ of replicate O3 measurements and ± 2 mm uncertainty in lengths of individual T185 = 0 and 1 segments.
Figure 4. Calculated I185 and I254 values for the lamp types shown in Figure 1. I185:I254 values were calculated from linear regression functions and used to derive OHex estimation equations. I185 and I254 values obtained by Li et al. (2015a) in an earlier-generation PAM OFR are shown for reference.
Figure 6. OHexp estimation equation fit coefficients plotted as a function I254:I254. Trendlines were calculated from exponential regression functions with fit parameters that are presented in Table 3.
Technical Note: Effect of varying the λ = 185 and 254 nm photon flux ratio on radical generation in oxidation flow reactors

July 2020

·

83 Reads

·

2 Citations

Oxidation flow reactors (OFRs) complement environmental smog chambers as a portable, low-cost technique for exposing atmospheric compounds to oxidants such as ozone (O3) and hydroxyl (OH) radicals. OH is most commonly generated in OFRs via photolysis of externally added O3 at λ = 254 nm (OFR254), or combined photolysis of O2 and H2O at λ = 185 nm plus photolysis of O3 at λ = 254 nm (OFR185) using low-pressure mercury (Hg) lamps. Whereas OFR254 radical generation is influenced by [O3], [H2O], and photon flux at λ = 254 nm (I254), OFR185 radical generation is influenced by [O2], [H2O], I185, and I254. Because the ratio of photon fluxes, I185 : I254, is OFR-specific, OFR185 performance varies between different systems even when constant H2O and I254 are maintained. Thus, calibrations and models developed for one OFR185 system may not be applicable to another. To investigate these issues, we conducted a series of experiments in which I185 : I254 emitted by Hg lamps installed in an OFR was systematically varied by fusing multiple segments of lamp quartz together that either transmitted or blocked 185 nm radiation. Integrated OH exposure (OHexp) values achieved for each lamp type were obtained using the tracer decay method as a function of UV intensity, humidity, residence time, and external OH reactivity (OHRext). Following previous related studies, a photochemical box model was used to develop a generalized OHexp estimation equation as a function of [H2O], [O3] and OHRext that is applicable for I185 : I254 &approx; 0.001 to 0.1.


Citations (24)


... 31,32 In the absence of sunlight, oxidation by the nitrate radical at night or in dense smoke forms absorbing nitroaromatics and 90 organonitrates, which enhance BrC absorption during dark aging. [33][34][35][36] Gas/aerosol repartitioning can also significantly affect the optical properties of BB aerosol in the hours after emission. 37,38 Evaporation during plume dilution decreases total aerosol mass, although evaporated semi-volatile compounds can re-condense onto existing particles or facilitate new particle formation via 95 ...

Reference:

Optical properties of biomass burning aerosol during the 2021 Oregon fire season: comparison between wild and prescribed fires
Diel Cycle Impacts on the Chemical and Light Absorption Properties of Organic Carbon Aerosol from Wildfires in the Western United States

... The mechanism of OFR185 mode, in which O3 and OH radicals were generated by the photolysis of O2 and H2O inside OFR, was applied in the model. Note that the ratio of photon flux between 185 and 254 nm from lamps produced by Light 170 Source Inc. does not change as a function of their intensity (Rowe et al., 2020), while these ratios do vary with intensity for the BHK lamps . In the model, the photon flux ratio of 185/254 nm was set to be constant (5%). ...

Technical Note: Effect of varying the λ = 185 and 254 nm photon flux ratio on radical generation in oxidation flow reactors

... 203Combining these two independent high-resolution mass spectrometer techniques, HrTOF-CIMS 204and UPLC/(-)ESI-Orbitrap MS, provides a very powerful tool for analyzing the particle-phase 205 chemical composition of OOMs, for identifying molecular structures of different isomers. So far, 206only a few studies have combined these two methods to make molecular-level chemical speciation 207of OOMs (e.g.,[Du et al., 2022;Huang et al., 2020;Mehra et al., 2020]). It is noted that HrTOF-208 CIMS (iodide ionization) and UPLC/(-)ESI-Orbitrap MS may have different ionization 209 efficiencies and detection efficiencies for different chemical compounds. ...

Evaluation of the Chemical Composition of Gas and Particle Phase Products of Aromatic Oxidation [discussion paper]
  • Citing Article
  • March 2020

... Liquid chromatography coupled with electrospray ionization orbitrap mass spectrometry (LC-Orbitrap MS) can probe the chemical composition of individual polar and non-polar particle-phase products with accurate mass measurement (Perry et al., 2008;Banerjee and Mazumdar, 2012;Mutzel et al., 2021). LC-MS has been extensively used for the chemical characterization of organic aerosols, quantifying 85 targeted tracers and characterising using tandem MS to determine the molecular identity of ambient SOA (Iinuma et al., 2007;Samy and Hays, 2013;Hamilton et al., 2013;Parshintsev et al., 2015;Chen et al., 2020) and laboratory-produced SOA (Winterhalter et al., 2003;Pereira et al., 2014;Mehra et al., 2020b;Mutzel et al., 2021). ...

Evaluation of the Chemical Composition of Gas and Particle Phase Products of Aromatic Oxidation

... This comparison is important for understanding differences in SOA formation and composition from these often grouped precursors. A companion paper provides detailed discussion of the mechanisms responsible for formation of the dominant oxidised products from these precursors (Wang et al., 2020). ...

Oxygenated products formed from OH-initiated reactions of trimethylbenzene: Autoxidation and accretion

... NO 3 þ O 2 followed by the reaction NO 3 þ NO 2 ! N 2 O 5 (Lambe et al. 2020). In these experiments, the NO 2 in the N 2 flow rate was set between 0 and 15 cm 3 min À1 , and O 3 was generated by passing 2 LPM of O 2 through an ozone chamber housing a mercury fluorescent lamp (GPH212T5VH, Light Sources, Inc.). ...

Nitrate radical generation via continuous generation of dinitrogen pentoxide in a laminar flow reactor coupled to an oxidation flow reactor

... On the other hand, Psat can be converted to C * with the assumption of the ideal gas law (Ylisirniö et al., 2019(Ylisirniö et al., , 2021. In this way, the relationship between C * and Tmax was deduced as: ...

Composition and volatility of SOA formed from oxidation of real tree emissions compared to single VOC-systems

... Particle composition measurements made using an aerosol mass spectrometer confirmed that the coating material was completely removed and established the relative composition for the mixed coating experiments. The absorption enhancement was determined as the ratio between the coated and uncoated (thermally denuded) particle absorption corrected for losses in the thermodenuder and for the influence of multiply charged particles (42). Further details are available in refs. ...

Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot
Sara D. Forestieri

·

Taylor M. Helgestad

·

Andrew T. Lambe

·

[...]

·

et. al

... There the increasing SOA yields with increasing SQT contribution to the precursor mix was explained by the much higher SOA yield of β-caryophyllene (Faiola et al., 2018). In chamber studies with emissions of aphid stressed Scots in which farnesenes were the dominant SQT species, SOA yields decreased with increasing SQT contribution for ozonolysis reaction while no change was observed for pure OH reaction experiments (Faiola et al., 2019). In our 255 experiments in the PAM reactor, the ratio between O3 and OH exposure was in the range of 10 5 which is comparable to ambient levels (Kang et al., 2007). ...

Insights into the O : C dependent mechanisms controlling the evaporation of α-pinene secondary organic aerosol particles

Atmospheric Chemistry and Physics Discussions

... Because models rely heavily on refractive indices to calculate aerosol optical properties, many investigations have focused on the "inverse problem" [4] of empirically retrieving the complex refractive index ( m ) m = n + ik (1) from measured optical and morphological data by either: 1) size-(and mass-) selecting particles and measuring some combination of the extinction, scattering and absorption efficiencies ( Q ext , Q scat and Q abs , respectively) or cross-sections ( C ext , C scat and C abs , respectively) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] -efficiencies are the ratio of the optical crosssection to physical cross-section -or 2) using the full distribution of aerosol particles and measuring the size distribution and at least two of the extinction ( α ext ), scattering ( α scat ), backscattering ( α bscat ) and/or absorption ( α abs ) coefficients [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] . Chemical species data have also been used to calculate an effective refractive index that is then compared to measured optical data [35,43] . ...

Measurement and modeling of the multi-wavelength optical properties of uncoated flame-generated soot

Atmospheric Chemistry and Physics Discussions