scholarly journals Source attribution of climatically important aerosol properties measured at Paposo (Chile) during VOCALS

2010 ◽  
Vol 10 (22) ◽  
pp. 10789-10801 ◽  
Author(s):  
D. Chand ◽  
D. A. Hegg ◽  
R. Wood ◽  
G. E. Shaw ◽  
D. Wallace ◽  
...  
Keyword(s):  
Light Scattering ◽  
Size Distribution ◽  
Biomass Burning ◽  
Receptor Modeling ◽  
Scattering Coefficient ◽  
Source Attribution ◽  
Aerosol Composition ◽  
Submicron Aerosol ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration

Abstract. Measurements of submicron aerosol composition, light scattering, and size distribution were made from 17 October to 15 November 2008 at the elevated Paposo site (25° 0.4' S, 70° 27.01' W, 690 m a.s.l.) on the Chilean coast as part of the VOCALS* Regional Experiment (REx). Based on the chemical composition measurements, a receptor modeling analysis using Positive Matrix Factorization (PMF) was carried out, yielding four broad source categories of the aerosol mass, light scattering coefficient, and a proxy for cloud condensation nucleus (CCN) concentration at 0.4% supersaturation derived from the size distribution measurements assuming an observed soluble mass fraction of 0.53. The sources resolved were biomass burning, marine, an urban-biofuels mix and a somewhat ambiguous mix of smelter emissions and mineral dust. The urban-biofuels mix is the most dominant aerosol mass component (52%) followed by biomass burning (25%), smelter/soil dust (12%) and marine (9%) sources. The average (mean±std) submicron aerosol mass concentration, aerosol light scattering coefficient and proxy CCN concentration were, 8.77±5.40 μg m−3, 21.9±11.0 Mm−1 and 548±210 cm−3, respectively. Sulfate is the dominant identified submicron species constituting roughly 40% of the dry mass (3.64±2.30 μg m−3), although the indentified soluble species constitute only 53% of the mass. Much of the unidentified mass is likely organic in nature. The relative importance of each aerosol source category is different depending upon whether mass, light scattering, or CCN concentration is being considered, indicating that the mean size of aerosols associated with each source are different. Marine aerosols do not appear to contribute to more than 10% to either mass, light scattering, or CCN concentration at this site. Back trajectory cluster analysis proved consistent with the PMF source attribution. *VOCALS: VAMOS** Ocean-Cloud-Atmosphere-Land Study (VOCALS) **VAMOS: Variability of American Monsoon System

scholarly journals Source attribution of climatically important aerosol properties measured at Paposo (Chile) during VOCALS

2010 ◽  
Vol 10 (7) ◽  
pp. 17853-17887 ◽  
Author(s):  
D. Chand ◽  
D. A. Hegg ◽  
R. Wood ◽  
G. E. Shaw ◽  
D. Wallace ◽  
...  
Keyword(s):  
Light Scattering ◽  
Size Distribution ◽  
Biomass Burning ◽  
Receptor Modeling ◽  
Scattering Coefficient ◽  
Source Attribution ◽  
Aerosol Composition ◽  
Submicron Aerosol ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration

Abstract. Measurements of submicron aerosol composition, light scattering, and size distribution were made from 17 October to 15 November 2008 at the elevated Paposo site (25° 0.4' S, 70°27.01' W, 690 m a.s.l.) on the Chilean coast as part of the VOCALS1 Regional Experiment (REx). Based on the chemical composition measurements, a receptor modeling analysis using Positive Matrix Factorization (PMF) was carried out, yielding four broad source categories of the aerosol mass, light scattering coefficient, and a proxy for cloud condensation nucleus (CCN) concentration at 0.4% supersaturation derived from the size distribution measurements assuming an observed soluble mass fraction of 0.53. The sources resolved were biomass burning, marine, an urban-biofuels mix and a somewhat ambiguous mix of smelter emissions and mineral dust. The urban-biofuels mix is the most dominant aerosol mass component (52%) followed by biomass burning (25%), smelter/soil dust (12%) and marine (9%) sources. The average (mean±std) submicron aerosol mass concentration, aerosol light scattering coefficient and proxy CCN concentration were, 8.77±5.40 μg m−3, 21.9±11.0 Mm−1 and 548±210 cm−3, respectively. Sulfate is the dominant identified submicron species constituting roughly 40% of the dry mass (3.64±2.30 μg m−3, although the indentified soluble species constitute only 53% of the mass. Much of the unidentified mass is likely organic in nature. The relative importance of each aerosol source category is different depending upon whether mass, light scattering, or CCN concentration is being considered, indicating that the mean size of aerosols associated with each source are different. Marine aerosols do not appear to contribute to more than 10% to either mass, light scattering, or CCN concentration at this site. Back trajectory cluster analysis proved consistent with the PMF source attribution. 1 VOCALS: VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS)VAMOS: Variability of American Monsoon System

scholarly journals Evaluating the PurpleAir monitor as an aerosol light scattering instrument

2021 ◽  
Author(s):  
James R. Ouimette ◽  
William C. Malm ◽  
Bret A. Schichtel ◽  
Patrick J. Sheridan ◽  
Elisabeth Andrews ◽  
...  
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Size Distribution ◽  
Field Data ◽  
Scattered Light ◽  
Concentration Field ◽  
Scattering Coefficient ◽  
Coefficient Of Determination ◽  
Aerosol Size Distribution ◽  
Aerosol Mass Concentration

Abstract. The Plantower PMS5003 sensors (PA-PMS) used in the PurpleAir (PA) monitor PA-II-SD configuration are equivalent to cell-reciprocal nephelometers using a 657 nm perpendicularly polarized light source that integrates light scattering from 18 to 166 degrees. Yearlong field data at the National Oceanic and Atmospheric Administration’s (NOAA) Mauna Loa Observatory (MLO) and Boulder Table Mountain (BOS) sites show that the 1 h average of the PA-PMS first size channel, labeled “> 0.3 μm” (“CH1”) is highly correlated with submicrometer aerosol scattering coefficients at the 550 nm and 700 nm wavelengths measured by the TSI 3563 integrating nephelometer, from 0.4 Mm−1 to 500 Mm−1. This corresponds to an hourly average submicrometer aerosol mass concentration of approximately 0.2 to 200 ug m−3. A physical-optical model of the PA-PMS is developed to estimate light intensity on the photodiode, accounting for angular truncation as a function of particle size. Predictions are then compared with yearlong fine aerosol size distribution and scattering coefficient field data at the BOS site. It is shown that CH1 is linearly proportional to the model-predicted intensity of the light scattered by particles in the PA-PMS laser to its photodiode over 4 orders of magnitude. This is consistent with CH1 being a measure of the scattering coefficient and not the particle number concentration or particulate matter concentration. Field data at BOS confirm the model prediction that the ratio of CH1 to the scattering coefficient would be highest for aerosols with median scattering diameters < 0.3 μm. The PA-PMS detects aerosols smaller than 0.3 μm diameter in proportion to their contribution to the scattering coefficient. The model predicts that the PA-PMS response to particles > 0.3 μm decreases relative to an ideal nephelometer by about 75 % for particle diameters ≥ 1.0 μm. This is a result of using a laser that is polarized, the angular truncation of the scattered light, and particle loss in the instrument before reaching the laser. The results of this study indicate that the PA-PMS is not an optical particle counter and that its six size fractions are not an accurate representation of particle size distribution. The relationship between the PA-PMS 1 h average CH1 and bsp1, the scattering coefficient in Mm−1 due to particles below 1 μm aerodynamic diameter, at wavelength 550 nanometers, is found to be bsp1 = 0.015 ± 2.07 × 10−5 × CH1, for relative humidity below 40 %. The coefficient of determination R2 is 0.97. This suggests that the low-cost and widely used PA monitors can be used to measure and predict the aerosol light scattering coefficient in the mid-visible nearly as well as integrating nephelometers.

scholarly journals Evolution of trace gases and particles emitted by a chaparral fire in California

2012 ◽  
Vol 12 (3) ◽  
pp. 1397-1421 ◽  
Author(s):  
S. K. Akagi ◽  
J. S. Craven ◽  
J. W. Taylor ◽  
G. R. McMeeking ◽  
R. J. Yokelson ◽  
...  
Keyword(s):  
Light Scattering ◽  
Biomass Burning ◽  
Trace Gases ◽  
Three Dimensional ◽  
Barometric Pressure ◽  
Molar Ratio ◽  
Gaseous Ammonia ◽  
Detection Range ◽  
Aging Period ◽  
Aerosol Mass

Abstract. Biomass burning (BB) is a major global source of trace gases and particles. Accurately representing the production and evolution of these emissions is an important goal for atmospheric chemical transport models. We measured a suite of gases and aerosols emitted from an 81 hectare prescribed fire in chaparral fuels on the central coast of California, US on 17 November 2009. We also measured physical and chemical changes that occurred in the isolated downwind plume in the first ~4 h after emission. The measurements were carried out onboard a Twin Otter aircraft outfitted with an airborne Fourier transform infrared spectrometer (AFTIR), aerosol mass spectrometer (AMS), single particle soot photometer (SP2), nephelometer, LiCor CO2 analyzer, a chemiluminescence ozone instrument, and a wing-mounted meteorological probe. Our measurements included: CO2; CO; NOx; NH3; non-methane organic compounds; organic aerosol (OA); inorganic aerosol (nitrate, ammonium, sulfate, and chloride); aerosol light scattering; refractory black carbon (rBC); and ambient temperature, relative humidity, barometric pressure, and three-dimensional wind velocity. The molar ratio of excess O3 to excess CO in the plume (ΔO3/ΔCO) increased from −5.13 (±1.13) × 10−3 to 10.2 (±2.16) × 10−2 in ~4.5 h following smoke emission. Excess acetic and formic acid (normalized to excess CO) increased by factors of 1.73 ± 0.43 and 7.34 ± 3.03 (respectively) over the same time since emission. Based on the rapid decay of C2H4 we infer an in-plume average OH concentration of 5.27 (±0.97) × 106 molec cm−3, consistent with previous studies showing elevated OH concentrations in biomass burning plumes. Ammonium, nitrate, and sulfate all increased over the course of 4 h. The observed ammonium increase was a factor of 3.90 ± 2.93 in about 4 h, but accounted for just ~36% of the gaseous ammonia lost on a molar basis. Some of the gas phase NH3 loss may have been due to condensation on, or formation of, particles below the AMS detection range. NOx was converted to PAN and particle nitrate with PAN production being about two times greater than production of observable nitrate in the first ~4 h following emission. The excess aerosol light scattering in the plume (normalized to excess CO2) increased by a factor of 2.50 ± 0.74 over 4 h. The increase in light scattering was similar to that observed in an earlier study of a biomass burning plume in Mexico where significant secondary formation of OA closely tracked the increase in scattering. In the California plume, however, ΔOA/ΔCO2 decreased sharply for the first hour and then increased slowly with a net decrease of ~20% over 4 h. The fraction of thickly coated rBC particles increased up to ~85% over the 4 h aging period. Decreasing OA accompanied by increased scattering/particle coating in initial aging may be due to a combination of particle coagulation and evaporation processes. Recondensation of species initially evaporated from the particles may have contributed to the subsequent slow rise in OA. We compare our results to observations from other plume aging studies and suggest that differences in environmental factors such as smoke concentration, oxidant concentration, actinic flux, and RH contribute significantly to the variation in plume evolution observations.

scholarly journals Retrieval of Vertical Mass Concentration Distributions—Vipava Valley Case Study

2019 ◽  
Vol 11 (2) ◽  
pp. 106 ◽  
Author(s):  
Longlong Wang ◽  
Samo Stanič ◽  
Klemen Bergant ◽  
William Eichinger ◽  
Griša Močnik ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Mass Concentration ◽  
Mineral Dust ◽  
Small Scale ◽  
Vertical Profiles ◽  
Total Uncertainty ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Types

Aerosol vertical profiles are valuable inputs for the evaluation of aerosol transport models, in order to improve the understanding of aerosol pollution ventilation processes which drive the dispersion of pollutants in mountainous regions. With the aim of providing high-accuracy vertical distributions of particle mass concentration for the study of aerosol dispersion in small-scale valleys, vertical profiles of aerosol mass concentration for aerosols from different sources (including Saharan dust and local biomass burning events) were investigated over the Vipava valley, Slovenia, a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. The analysis was based on datasets taken between 1–30 April 2016. In-situ measurements of aerosol size, absorption, and mass concentration were combined with lidar remote sensing, where vertical profiles of aerosol concentration were retrieved. Aerosol samples were characterized by SEM-EDX, to obtain aerosol morphology and chemical composition. Two cases with expected dominant presence of different specific aerosol types (mineral dust and biomass-burning aerosols) show significantly different aerosol properties and distributions within the valley. In the mineral dust case, we observed a decrease of the elevated aerosol layer height and subsequent spreading of mineral dust within the valley, while in the biomass-burning case we observed the lifting of aerosols above the planetary boundary layer (PBL). All uncertainties of size and assumed optical properties, combined, amount to the total uncertainty of aerosol mass concentrations below 30% within the valley. We have also identified the most indicative in-situ parameters for identification of aerosol type.

scholarly journals Cloud Activating Properties of Aerosol Observed during CELTIC

2007 ◽  
Vol 64 (2) ◽  
pp. 441-459 ◽  
Author(s):  
Craig A. Stroud ◽  
Athanasios Nenes ◽  
Jose L. Jimenez ◽  
Peter F. DeCarlo ◽  
J. Alex Huffman ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Size Distribution ◽  
Organic Aerosol ◽  
Aerosol Size Distribution ◽  
Model Bias ◽  
Aerosol Composition ◽  
Ambient Aerosol ◽  
Aerosol Mass ◽  
Mass Fractions ◽  
Mass Size

Abstract Measurements of aerosol size distribution, chemical composition, and cloud condensation nuclei (CCN) concentration were performed during the Chemical Emission, Loss, Transformation, and Interactions with Canopies (CELTIC) field program at Duke Forest in North Carolina. A kinetic model of the cloud activation of ambient aerosol in the chamber of the CCN instrument was used to perform an aerosol–CCN closure study. This study advances prior investigations by employing a novel fitting algorithm that was used to integrate scanning mobility particle sizer (SMPS) measurements of aerosol number size distribution and aerosol mass spectrometer (AMS) measurements of the mass size distribution for sulfate, nitrate, ammonium, and organics into a single, coherent description of the ambient aerosol in the size range critical to aerosol activation (around 100-nm diameter). Three lognormal aerosol size modes, each with a unique internally mixed composition, were used as input into the kinetic model. For the two smaller size modes, which control CCN number concentration, organic aerosol mass fractions for the defined cases were between 58% and 77%. This study is also unique in that the water vapor accommodation coefficient was estimated based on comparing the initial timing for CCN activation in the instrument chamber with the activation predicted by the kinetic model. The kinetic model overestimated measured CCN concentrations, especially under polluted conditions. Prior studies have attributed a positive model bias to an incomplete understanding of the aerosol composition, especially the role of organics in the activation process. This study shows that including measured organic mass fractions with an assumed organic aerosol speciation profile (pinic acid, fulvic acid, and levoglucosan) and an assumed organic aerosol solubility of 0.02 kg kg−1 still resulted in a significant model positive bias for polluted case study periods. The slope and y intercept for the CCN predicted versus CCN observed regression was found to be 1.9 and −180 cm−3, respectively. The overprediction generally does not exceed uncertainty limits but is indicative that a bias exists in the measurements or application of model. From this study, uncertainties in the particle number and mass size distributions as the cause for the model bias can be ruled out. The authors are also confident that the model is including the effects of growth kinetics on predicted activated number. However, one cannot rule out uncertainties associated with poorly characterized CCN measurement biases, uncertainties in assumed organic solubility, and uncertainties in aerosol mixing state. Sensitivity simulations suggest that assuming either an insoluble organic fraction or external aerosol mixing were both sufficient to reconcile the model bias.

scholarly journals Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Genrik Mordas ◽  
Nina Prokopciuk ◽  
Steigvilė Byčenkienė ◽  
Jelena Andriejauskienė ◽  
Vidmantas Ulevicius
Keyword(s):  
Optical Properties ◽  
Light Scattering ◽  
Urban Environment ◽  
Size Distribution ◽  
Number Concentration ◽  
Scattering Coefficient ◽  
Dust Particles ◽  
Aerosol Size Distribution ◽  
Air Masses ◽  
The Impact

Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius). Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm) measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm) and number concentration (Dpa> 0.5 μm) registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3and 12.8 Mm−1associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3and 276 Mm−1associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1) during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed.

scholarly journals Aerosol physicochemical properties and implication for visibility during an intense haze episode during winter in Beijing

2014 ◽  
Vol 14 (16) ◽  
pp. 23375-23413 ◽  
Author(s):  
Y. H. Wang ◽  
Z. R. Liu ◽  
J. K. Zhang ◽  
B. Hu ◽  
D. S. Ji ◽  
...  
Keyword(s):  
Light Scattering ◽  
Particle Growth ◽  
Submicron Particles ◽  
Aerosol Mass Spectrometer ◽  
Average Mass ◽  
Submicron Aerosol ◽  
Aerosol Mass ◽  
Synoptic Conditions ◽  
Haze Episode ◽  
Pm2.5 And Pm10

Abstract. The evolution of physical, chemical and optical properties of urban aerosol particles was characterized during an extreme haze episode in Beijing, PRC from 24 January through 31 January 2013 based on in-situ measurements. The average mass concentrations of PM1, PM2.5 and PM10 were 99 ± 67 μg m−3 (average ± stdev), 188 ± 128 μg m−3 and 265 ± 157 μg m−3, respectively. A significant increase in PM1−2.5 fraction was observed during the most heavily polluted periods. The average scattering coefficient (λ = 550 nm) was 877 ± 624 M m−1. An increasing relative amount of coarse particles can be deduced from the variations of backscattering ratios, asymmetry parameter and scattering Ångström exponent. Particle number size distributions between 14 nm and 2500 nm diameter showed high number concentrations, particularly in the nucleation mode and accumulation modes. Size-resolved chemical composition of submicron aerosol from a High Resolution-ToF-Aerosol Mass Spectrometer showed that the mass concentration of organic, sulfate, nitrate, ammonium and chlorine mainly resided on 500 nm to 800 nm (vacuum diameter) particles, and sulfate and ammonium contributed most to particle growth during the most heavily polluted day (28 January). Increasing relative humidity and stable synoptic conditions on 28 January combined with heavy pollution, lead to enhanced water uptake by the hygroscopic submicron particles and formation of secondary aerosol, maybe the main reasons for the severity of the haze episode. Light scattering apportionment showed that organic, ammonium sulfate, ammonium nitrate and ammonium chloride compounds contributed to light scattering fractions of 57%, 23%, 10% and 10%, respectively. This study indicated that the organic component in submicron aerosol plays an important role in visibility degradation in this haze episode in and around Beijing.

scholarly journals Evaluation of the carbon content of aerosols from the burning of biomass in the Brazilian Amazon using thermal, optical and thermal-optical analysis methods

2010 ◽  
Vol 10 (5) ◽  
pp. 12859-12906 ◽  
Author(s):  
L. L. Soto-García ◽  
M. O. Andreae ◽  
T. W. Andreae ◽  
P. Artaxo ◽  
W. Maenhaut ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Amazon Basin ◽  
Sampling Site ◽  
Water Soluble ◽  
Diurnal Changes ◽  
Optical Analysis ◽  
Dry Period ◽  
Aerosol Composition ◽  
Aerosol Mass ◽  
Mass Concentrations

Abstract. Aerosol samples were collected at a pasture site in the Amazon Basin as part of the project LBA-SMOCC-2002 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). Sampling was conducted during the late dry season, when the aerosol composition was dominated by biomass burning emissions, especially in the submicron fraction. A 13-stage Dekati low-pressure impactor (DLPI) was used to collect particles with nominal aerodynamic diameters ranging from 0.03 to 0.10 μm. Gravimetric analyses of the DLPI substrates and filters were performed to obtain aerosol mass concentrations. The concentrations of total, apparent elemental, and organic carbon (TC, ECa, and OC) were determined using thermal and thermal-optical analysis (TOA) methods. A light transmission method (LTM) was used to determine the concentration of equivalent black carbon (BCe) or the absorbing fraction at 880 nm for the size-resolved samples. During the dry period, due to the pervasive presence of fires in the region upwind of the sampling site, concentrations of fine aerosols (Dp < 2.5 μm: average 59.8 μg m−3) were higher than coarse aerosols (Dp > 2.5 μm: 4.1 μg m−3). Carbonaceous matter, estimated as the sum of the particulate organic matter (i.e., OC×1.8) plus BCe, comprised more than 90% to the total aerosol mass. Concentrations of ECa (estimated by thermal analysis with a correction for charring) and BCe (estimated by LTM) averaged 5.2±1.3 and 3.1±0.8 μg m−3, respectively. The determination of EC was improved by extracting water soluble organic material from the samples, which reduced the average light absorption Ångström exponent of particles in the size range of 0.1 to 1.0 μm from being greater than 2.0 to approximately 1.2. The size-resolved BCe measured by the LTM showed a clear maximum between 0.4 to 0.6 μm in diameter. The concentrations of OC and BCe varied diurnally during the dry period, and this variation is related to diurnal changes in boundary layer thickness and in fire frequency.

scholarly journals Size distribution of near-surface aerosols and its relation to the columnar aerosol optical depths

2004 ◽  
Vol 22 (10) ◽  
pp. 3347-3351 ◽  
Author(s):  
P. S. Pillai ◽  
K. Krishna Moorthy
Keyword(s):  
Size Distribution ◽  
Quartz Crystal Microbalance ◽  
Relative Abundance ◽  
Mass Concentration ◽  
Quartz Crystal ◽  
Near Surface ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Multi Wavelength ◽  
Aerosol Properties

Abstract. Simultaneous data on Aerosol Optical Depth (AOD) and size segregated, near-surface, aerosol mass concentration was obtained from a Multi wavelength Solar Radiometer (MWR) and Quartz Crystal Microbalance Impactor (QCM), respectively. These were used to examine the association between near-surface aerosol properties and columnar AOD. The spectral AODs were approximated to the Ångström relation τp=βλ-α, and the wavelength exponent α and turbidity coefficient β have been obtained. In general, α was found to be well associated with the relative abundance of accumulation mode aerosols (estimated from the simultaneous QCM data) while β followed the variations of the coarse mode aerosol mass concentration; the association being closer during periods of continental airmass.

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