Atmospheric Processes Influencing Aerosols Generated by Combustion and the Inference of Their Impact on Public Exposure: A Review

A few field studies have reported high levels of in-cabin ultrafine particles and discussed certain contributing factors such as vehicle operations and atmospheric meteorological conditions. However, to generalize limited field study results to a wide range of conditions, a deeper understanding of affecting factors and a simple model that can predict on-road particle concentrations are essential. This paper has two objectives, first, to analyze the effects of surrounding vehicle density, relative freeway lane position, and vehicle speed on measured particle concentrations on two California freeways, I-405 (5% diesel) and I-710 (25% diesel). The second objective is to test the use of Emission Factor (EMFAC) 2007 and Caline4 (CL4) models in predicting on-road particle concentrations. Particle number and mass concentrations were collected using a mobile laboratory driving on the I-710 and I-405 freeways. Particle number concentration was found to be affected by the density of surrounding heavy duty diesel trucks which is consistent with previous studies. The highest particle number concentrations were measured in the outer lanes on the freeway and the lowest was in the inner lanes. The highest levels of particles were measured at vehicle speeds of 40-50 mph. Analysis of CL4 model was conducted using factor-of-two test. For the I-710, 85% of values were within the factor-of-two envelope, and for the I-405, 77% were within the envelope. Regression analysis showed that the model is able to account for 43% of the variability on the I-710 and 26% of the variability on the I-405. The use of CL4 in conjunction with EMFAC shows promise as a simple tool to estimate on-road PM 2.5 concentration.

Section: Vehicle Speed Effectsmentioning

confidence: 97%

Particle Concentration on Freeways: Affecting Factors and a Simple Model Development

Fung

Zhou

Hinds

et al. 2013

“…Traffic emissions are also found to be the main source of Ultra Fine Particles (UFP) in urban areas (Avino et al, 2011). Especially the semi-volatile PM fraction of these emissions is highly correlated with the toxicological potency of PM (Ning and Sioutas, 2010). Antwerp also includes one of the largest harbor areas in the world where a large number of refineries are present, resulting in elevated SO 2 emissions, which are of particular interest in this study.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Regional Dynamics of Gaseous Admixtures and Aerosols in the Areas of Lake Baikal (Russia) and Antwerp (Belgium)

Aloyan

Arutyunyan

Yermakov

et al. 2012

A combined mathematical model was developed for the regional-scale dynamics of gaseous admixtures and aerosols in the atmosphere. The model incorporates the following modules: thermo-hydrodynamic equations for meso-scale atmospheric processes in the non-hydrostatic approximation; transport of gaseous admixtures and aerosols, with allowance for photochemical transformation and binary homogeneous nucleation; and kinetic processes of condensation/evaporation and coagulation. Particular emphasis is given to the mechanisms of new-particle formation through binary homogeneous nucleation of drops of sulfuric acid and water vapor. By using this model, numerical experiments were performed to investigate spatio-temporal variations in the concentrations of gaseous admixtures and aerosols, as well as the formation of fine aerosol clusters in the Lake Baikal (Russia) and Antwerp (Belgium) areas due to strong industrial emission sources. The results of the numerical experiments are analyzed.

“…The instantaneous dilution ratio (DR) is calculated as (Ning and Sioutas, 2010 [CO ] The one-liter canister flow rate is controlled by a critical orifice. CO, CO 2 , and methane (CH 4 ) are analyzed by gas chromatograph with flame ionization detector (GC-FID), and NMHC (C 2 -C 11 ) are analyzed by GC-mass spectrometry (MS)-FID (U.S.EPA, 1999).…”

Section: Multipollutant Dilution Sampling and Measurement Systemmentioning

confidence: 99%

An Efficient Multipollutant System for Measuring Real-World Emissions from Stationary and Mobile Sources

Wang

Watson

Chow

et al. 2012

A portable dilution sampling and measurement system was developed for measuring multipollutant emissions from stationary and mobile sources under real-world operating conditions. This system draws a sample of exhaust gas from the source, dilutes it with filtered air and quantifies total volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO 2 ), nitric oxide (NO), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), oxygen (O 2 ), particle size distribution, particle number and mass concentrations, and black carbon (BC) concentration at 1-6 sec interval. Integrated samples by canisters and filter packs are acquired for laboratory analyses of VOC speciation, particle mass concentration, light absorption, elements, isotopes, ions, ammonia (NH 3 ), hydrogen sulfide (H 2 S), sulfur dioxide (SO 2 ), carbon, and organic compounds. Experiments were carried out to evaluate this system. The accuracy of key real-time instruments were found to deviate < ± 12% from references. CO 2 was used as the tracer gas to verify the concentration uniformity in the three measurement modules and relative concentration difference was < 5.1%. Instrument response time was tested by emissions from lighting and burning matches. The DustTrak DRX and optical particle counter (OPC) had the fastest response time, while other instruments had 3.5-21.5 sec delay from the DustTrak DRX and OPC. This system was applied to measure emissions from burning pine logs in a wood stove. The real-time data showed flaming, transition, and smoldering phases, and allowed real-time emission ratios to be calculated. Combing real-time data and laboratory analysis, this measurement system allows the development of multipollutant emission factors and source profiles.