Keller, Alejandro
E-Mail-Adresse
Geburtsdatum
Suchergebnisse
A novel measurement system for unattended, in situ characterization of carbonaceous aerosols
Carbonaceous aerosol is a relevant constituent of the atmosphere in terms of climate and health impacts. Nevertheless, measuring this component poses many challenges. There is currently no simple and sensitive commercial technique that can reliably capture its totality in an unattended manner, with minimal user intervention, for extended periods of time. To address this issue we have developed the fast thermal carbon totalizator (FATCAT). Our system captures an aerosol sample on a rigid metallic filter and subsequently analyses it by rapidly heating the filter directly, through induction, to a temperature around 800°C. The carbon in the filter is oxidized and quantified as CO2 in order to establish the total carbon (TC) content of the sample. The metallic filter is robust, which solves filter displacement or leakage problems, and does not require a frequent replacement like other measurement techniques. The limit of detection of our system using the 3σ criterion is TC =0.19 µg-C (micrograms of carbon). This translates to an average ambient concentration of TC =0.32 µg-C m^−3 and TC =0.16 µg-C m^−3 for sampling interval of 1 or 2 h respectively using a sampling flow rate of 10 L min^−1. We present a series of measurements using a controlled, well-defined propane flame aerosol as well as wood-burning emissions using two different wood-burning stoves. Furthermore, we complement these measurements by coating the particles with secondary organic matter by means of an oxidation flow reactor. Our device shows a good correlation (correlation coefficient, R^2>0.99) with well-established techniques, like mass measurements by means of a tapered element oscillating microbalance and TC measurements by means of thermal–optical transmittance analysis. Furthermore, the homogeneous fast-heating of the filter produces fast thermograms. This is a new feature that, to our knowledge, is exclusive of our system. The fast thermograms contain information regarding the volatility and refractoriness of the sample without imposing an artificial fraction separation like other measurement methods. Different aerosol components, like wood-burning emissions, soot from the propane flame and secondary organic matter, create diverse identifiable patterns.
Coated soot particles with tunable, well-controlled properties generated in the laboratory with a miniCAST BC and a micro smog chamber
A Micro Smog Chamber (MSC) was coupled for the first time with a miniCAST 5201 Type BC combustion generator with the aim to produce a series of stable and reproducible model aerosols simulating the physical properties of combustion particles present in ambient air. With this setup it was possible to generate particles ranging from “fresh” soot (single scattering albedo SSA≤0.05, absorption Ångström exponent AAE close to 1, high EC/TC mass fraction (approximately 90%) and mobility diameter typically <100 nm) to “aged” soot with different amounts of organic coating. The “aged” soot particles could grow up to 200 nm and exhibited high SSA (up to 0.7 at λ = 870 nm), an increased AAE (up to 1.7) and low EC/TC mass fraction (down to <10%). The ageing was achieved by coating the soot particles with increasing amounts of secondary organic matter (SOM) formed by the photo-oxidation of α-pinene or mesitylene in the MSC. Thereby, the SSA and AAE increased with coating thickness, while the EC/TC mass fraction decreased. Over the experimental period of 2 h, the generation of the “aged” soot aerosols was stable with a standard deviation in particle size and number concentration of <1% and <6%, respectively. The day-to-day reproducibility was also satisfactory: with α-pinene as SOM precursor the variability (standard deviation) in particle size was <2% and in the AAE and SSA < 6%. Particle number concentrations up to 106 cm−3 and mass concentrations up to 15 mg/m3 (depending on particle size and SOM amount) could be generated, much higher than what has been reported with other oxidation flow reactors. The generated carbonaceous aerosols could find useful applications in the field of aerosol instrument calibration, particularly in the standardization of filter-based absorption photometers under controlled conditions.
Responses of reconstituted human bronchial epithelia from normal and health-compromised donors to non-volatile particulate matter emissions from an aircraft turbofan engine
Health effects of particulate matter (PM) from aircraft engines have not been adequately studied since controlled laboratory studies reflecting realistic conditions regarding aerosols, target tissue, particle exposure and deposited particle dose are logistically challenging. Due to the important contributions of aircraft engine emissions to air pollution, we employed a unique experimental setup to deposit exhaust particles directly from an aircraft engine onto reconstituted human bronchial epithelia (HBE) at air-liquid interface under conditions similar to in vivo airways to mimic realistic human exposure. The toxicity of non-volatile PM (nvPM) from a CFM56-7B26 aircraft engine was evaluated under realistic engine conditions by sampling and exposing HBE derived from donors of normal and compromised health status to exhaust for 1 h followed by biomarker analysis 24 h post exposure. Particle deposition varied depending on the engine thrust levels with 85% thrust producing the highest nvPM mass and number emissions with estimated surface deposition of 3.17 × 109 particles cm−2 or 337.1 ng cm−2. Transient increase in cytotoxicity was observed after exposure to nvPM in epithelia derived from a normal donor as well as a decrease in the secretion of interleukin 6 and monocyte chemotactic protein 1. Non-replicated multiple exposures of epithelia derived from a normal donor to nvPM primarily led to a pro-inflammatory response, while both cytotoxicity and oxidative stress induction remained unaffected. This raises concerns for the long-term implications of aircraft nvPM for human pulmonary health, especially in occupational settings.
Non-volatile particle emissions from aircraft turbine engines at ground-idle induce oxidative stress in bronchial cells
Aircraft emissions contribute to local and global air pollution. Health effects of particulate matter (PM) from aircraft engines are largely unknown, since controlled cell exposures at relevant conditions are challenging. We examined the toxicity of non-volatile PM (nvPM) emissions from a CFM56-7B26 turbofan, the world’s most used aircraft turbine using an unprecedented exposure setup. We combined direct turbine-exhaust sampling under realistic engine operating conditions and the Nano-Aerosol Chamber for In vitro Toxicity to deposit particles onto air–liquid-interface cultures of human bronchial epithelial cells (BEAS-2B) at physiological conditions. We evaluated acute cellular responses after 1-h exposures to diluted exhaust from conventional or alternative fuel combustion. We show that single, short-term exposures to nvPM impair bronchial epithelial cells, and PM from conventional fuel at ground-idle conditions is the most hazardous. Electron microscopy of soot reveals varying reactivity matching the observed cellular responses. Stronger responses at lower mass concentrations suggest that additional metrics are necessary to evaluate health risks of this increasingly important emission source.