16 research outputs found
Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot
Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles, (ii) thermally denuded nascent particles, and (iii) particles that were coated and then thermally denuded, leading to the collapse of the initially lacy, fractal-like morphology. The measured mass absorption coefficients (MACs) depended on soot maturity and generation but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters \u3e∼160 nm, the MAC and absorption Ångström exponent (AAE) values were independent of particle collapse while the single-scatter albedo increased. The MAC values for these larger particles were also size-independent. The mean MAC value at 532 nm for larger particles was 9.1±1.1 m2 g−1, about 17 % higher than that recommended by Bond and Bergstrom (2006), and the AAE was close to unity. Effective, theory-specific complex refractive index (RI) values are derived from the observations with two widely used methods: Lorenz–Mie theory and the Rayleigh–Debye–Gans (RDG) approximation. Mie theory systematically underpredicts the observed absorption cross sections at all wavelengths for larger particles (with x\u3e0.9) independent of the complex RI used, while RDG provides good agreement. (The dimensionless size parameter x=πdp/λ, where dp is particle diameter and λ is wavelength.) Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to underpredictions in the absorption by BC, with the extent of underprediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant, size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models
Real-Time Black Carbon Emission Factor Measurements from Light Duty Vehicles
Eight light-duty gasoline low emission vehicles (LEV I) were tested on a Chassis dynamometer using the California Unified Cycle (UC) at the Haagen-Smit vehicle test facility at the California Air Resources Board in El Monte, CA during September 2011. The UC includes a cold start phase followed by a hot stabilized running phase. In addition, a light-duty gasoline LEV vehicle and ultralow emission vehicle (ULEV), and a light-duty diesel passenger vehicle and gasoline direct injection (GDI) vehicle were tested on a constant velocity driving cycle. A variety of instruments with response times ≥0.1 Hz were used to characterize how the emissions of the major particulate matter components varied for the LEVs during a typical driving cycle. This study focuses primarily on emissions of black carbon (BC). These measurements allowed for the determination of BC emission factors throughout the driving cycle, providing insights into the temporal variability of BC emission factors during different phases of a typical driving cycle
Establishing the impact of model surfactants on cloud condensation nuclei activity of sea spray aerosol mimics
Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments
Data from: Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)
Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot
Data from: Temperature Dependence of Sea Spray Aerosol Production. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)
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Real-time black carbon emission factor measurements from light duty vehicles.
Eight light-duty gasoline low emission vehicles (LEV I) were tested on a Chassis dynamometer using the California Unified Cycle (UC) at the Haagen-Smit vehicle test facility at the California Air Resources Board in El Monte, CA during September 2011. The UC includes a cold start phase followed by a hot stabilized running phase. In addition, a light-duty gasoline LEV vehicle and ultralow emission vehicle (ULEV), and a light-duty diesel passenger vehicle and gasoline direct injection (GDI) vehicle were tested on a constant velocity driving cycle. A variety of instruments with response times ≥0.1 Hz were used to characterize how the emissions of the major particulate matter components varied for the LEVs during a typical driving cycle. This study focuses primarily on emissions of black carbon (BC). These measurements allowed for the determination of BC emission factors throughout the driving cycle, providing insights into the temporal variability of BC emission factors during different phases of a typical driving cycle
Real-Time Black Carbon Emission Factor Measurements from Light Duty Vehicles
Eight
light-duty gasoline low emission vehicles (LEV I) were tested
on a Chassis dynamometer using the California Unified Cycle (UC) at
the Haagen-Smit vehicle test facility at the California Air Resources
Board in El Monte, CA during September 2011. The UC includes a cold
start phase followed by a hot stabilized running phase. In addition,
a light-duty gasoline LEV vehicle and ultralow emission vehicle (ULEV),
and a light-duty diesel passenger vehicle and gasoline direct injection
(GDI) vehicle were tested on a constant velocity driving cycle. A
variety of instruments with response times ≥0.1 Hz were used
to characterize how the emissions of the major particulate matter
components varied for the LEVs during a typical driving cycle. This
study focuses primarily on emissions of black carbon (BC). These measurements
allowed for the determination of BC emission factors throughout the
driving cycle, providing insights into the temporal variability of
BC emission factors during different phases of a typical driving cycle
Recommended from our members