Biomass burning is one of the largest aerosol sources worldwide. In this study, the hygroscopic properties of fresh and aged wood burning particles were investigated under controlled laboratory ...conditions in several smog chamber experiments. Beech log wood was burnt in a residential log wood burner and the particles emitted during the different burning phases (starting, flaming, and smoldering) were analyzed. The particles were photochemically aged using the own volatile organic compound emissions from the burnt wood. The hygroscopic properties of the particles at relative humidities below and above 100% were determined and compared.
The freshly emitted soot particles have a fractal-like structure. The structure collapsed in half of the experiments where soot was present for particles ≥100nm under the presence of a high relative humidity, leading to a more compact structure. This restructuring induces an underestimation of the hygroscopicity measured with mobility diameter based methods.
The hygroscopicity parameter “apparent κ” of fresh wood combustion particles varies between 0 and 0.39. With aging, the hygroscopicity of the particles generally increases. This is due to the uptake of organic matter and inorganic salts, and because the particles become more oxidized.
One smoldering phase experiment was carried out, which, in contrast to the other experiments, showed very high apparent κ values between 0.2 and 0.4 at the beginning of the experiment, depending on the size of the particles. These values were decreasing with time. This suggests a different composition of the particles, with a higher fraction of inorganic components initially.
The results indicate that it is not possible to use only one κ value for different burning phases and aging times of wood combustion particles in climate models.
► Fresh and aged wood burning particles from a log wood burner were investigated in a smog chamber. ► Their hygroscopic properties were determined in the sub- and supersaturated regime. ► Different burning phases (flaming, starting, and smoldering) and particle sizes were investigated. ► The hygroscopicity of the organic fraction of the particles was estimated for one experiment.
Currently the main pollution comes from the anthropogenic sources related to residential heating and combustion. Most of the emitted particles from this sources are in the mode below 1 μm. Therefore, ...only by using methods based on the electric mobility separation and size enhancement we can measure the size and concentration of this particles from nano to ultrafine sizes. This contribution describes the most recent methods how to study particle size and concentration of the particles coming from combustion sources.
Proton-transfer-reaction mass spectrometry (PTR-MS) is a useful tool in ambient trace gas analysis, especially for the analysis of oxygenated volatile organic compounds (OVOC). Many OVOCs are ...produced during photooxidation of volatile organic compounds and contribute to both the gas phase and secondary organic aerosols (SOA). The inlet system of the PTR-MS instrument was modified to allow also for the measurement of the particulate phase of an aerosol with a high time resolution. The new inlet consists mainly of a denuder to strip off the gas phase, and a heater (120/150 °C) to vaporize the aerosol particles. This inlet system was tested with pinonic acid particles generated with a nebulizer and SOA particles formed during the photooxidation of 1,3,5-trimethylbenzene and α-pinene with NO x in a smog chamber. The performance of this new technique is discussed and the partitioning coefficients for the oxidation products are estimated.
Air pollution in the urban environment is a major concern. The ambient concentrations depend on the levels of transboundary imported pollution, the intensity of local sources and the prevailing ...atmospheric conditions. This work studies the relative impact of two atmospheric variables–atmospheric stability and regional scale turbulence–in determining the air pollution concentrations. We considered a setting (downtown Haifa, Israel) impacted by a large variety of sources, emitting pollutants with different chemical attributes and atmospheric life times. We found that traffic accounts for most of the locally produced pollution in the study location. However, the meteorological factors can overwhelm its impact and dictate the concentrations. The switch from stable to convective conditions and the more vigorous daytime wind are associated with a premature end of the morning peak concentrations that result from rush hour emissions of NOx, Black Carbon (BC) and ultra–fine particles. It results in daytime concentration which are lower than (winter) or equal to (summer) those at night, in spite of the much lower night–time traffic volumes. Similar, albeit weaker, impact was detected in the benzene and toluene concentrations. Sources outside the study area are responsible for most of the CO, PM1 and PM2.5 concentrations but during winter nights, characterised by strong atmospheric stability and low turbulence, their concentrations are elevated due to the local emissions. We developed a diagnostic statistical nonlinear model for the pollutant concentrations, which points to a stronger association of the atmospheric stability with the concentrations during stable conditions but turbulence dominating during convective conditions. Our findings explain the relatively low overall concentrations of locally emitted pollutants in the study area but warn of the potential for high concentrations during night–time in locations with comparable meteorological conditions.
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•Atmospheric stability and turbulence override the impact of local pollution sources.•The relative importance of sources and meteorology depends on the stability state.•Large contribution of external sources to CO and PM concentrations.•Meteorology's impact explains the relatively low concentrations in the study area.•Our conclusions can be useful for air pollution management and exposure modelling.
The aim of this study was to establish traceable number concentration measurements of airborne particles beyond 10 μm in particle size. To this end, the primary standards for particle number ...concentration at the National Metrology Institutes of Switzerland and Japan were further developed to extend their measurement capabilities. Details on the upgraded setup are provided. An inter-comparison of the two primary standards using an optical particle counter as transfer standard showed that these agree well within the stated uncertainties at polystyrene (PS) equivalent optical diameter of 15 µm. Subsequently, four Model 3321 (TSI Inc., USA) aerodynamic particle size spectrometers (APS) were calibrated against the primary standard of Switzerland using size-certified PS spheres with optical/aerodynamic diameter up to 20 µm as test aerosols. The counting efficiency profile and unit-to-unit variability of the APS units were determined. The results presented here can be useful for the analysis and interpretation of data collected by the different atmospheric aerosol networks worldwide. The outlined methodology can also be applied in the calibration of automated bio-aerosol monitors.
This study aim is to compare the number concentration of airborne nanoparticles reported by 13 different Condensation Particle Counters (CPC) with regards to a reference CPC, for a set of aerosols of ...interest. Among the models investigated, 5 are handheld CPC, while the 8 others are stationary CPC. The latter include butanol-based CPC as well as water-based CPC. Polydisperse test aerosols with modal diameters between 6 and 460 nm were produced in the CAIMAN experimental facility. Non-hydrophobic aerosols consisted of metal-based particles (Ti, C, Al, Cu, Ag), as well as nebulized suspensions (SiO2). Hydrophobic particles consisted of DEHS as well as alkanes (n-C13 to n-C20). Overall, about 400 different conditions were investigated to represent a wide range of aerosols potentially encountered in workplaces. The range of number concentrations provided by the reference CPC was 500 - 400 000 cm−3. To highlight the possible effect of particle counting efficiency on the total concentration reported by the different CPCs, 40% of the test aerosols presented a modal diameter below 40 nm. The influence of particle material for water-based CPCs was investigated through the generation of about 100 hydrophobic test aerosols. CPC response was found to be sensitive to the mode of the aerosols measured, depending on the counting efficiency curve of the CPC investigated. An effect of particle hydrophobicity on the response of some water-based CPC models was demonstrated, while one water-based CPC did not show any material dependence.
This study provides insights into the performance of a new nano-water-based condensation particle counter (N-WCPC, TSI 3788) and presents a comparison to the well-established butanol-based ultrafine ...CPC (UCPC, TSI 3776). The suitability of the N-WCPC to measure ambient airborne nanoparticles of various compositions has been assessed with an urban background aerosol in a light industrial area and provided comparable results (within 2%) to the 3776 at various particle number concentrations. The subsequent investigation using laboratory generated nearly monodisperse positively charged sucrose, sodium chloride, proteins, emery oil, and candle-generated particles in the diameter range of 2-53 nm showed material-dependent N-WCPC cut-off sizes between 2.2 and 17.2 nm at standard operating temperatures.
Copyright 2013 American Association for Aerosol Research
The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary ...organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.
The paper is devoted the standard CEN/TS 16976 described a standardized measuring method with number concentration of UFP. As well as, described TSI 3750-CEN CPC which meet all of these requirements.
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