scholarly journals Effect of photochemical aging on the ice nucleation properties of diesel and wood burning particles

2012 ◽  
Vol 12 (6) ◽  
pp. 14697-14726 ◽  
Author(s):  
C. Chou ◽  
O. Stetzer ◽  
T. Tritscher ◽  
R. Chirico ◽  
M. F. Heringa ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Diesel Oxidation Catalyst ◽  
Ice Nucleation ◽  
Oxidation Catalyst ◽  
Ice Formation ◽  
Nucleation Behavior ◽  
Diesel Particles ◽  
Wood Burning ◽  
Photochemical Aging ◽  
Deposition Mode

Abstract. A measurement campaign (IMBALANCE) was conducted in 2009 and aimed at characterizing the physical and chemical properties of freshly emitted and photochemically aged combustion particles emitted from a log wood burner and diesel vehicles: a EURO3 Opel Astra with a diesel oxidation catalyst (DOC) but no particle filter and a EURO2 Volkswagen Transporter TDI Syncro with no emission after-treatment. Ice nucleation experiments in the deposition and condensation freezing modes were conducted with the Portable Ice Nucleation Chamber (PINC) at three nominal temperatures, −30 °C, −35 °C and −40 °C. Freshly emitted diesel particles showed ice formation only at −40 °C in the deposition mode at 137% relative humidity with respect to ice (RHi) and 92% relative humidity with respect to water (RHw), and photochemical aging did not play a role in modifying their ice nucleation behavior. Only one diesel experiment where α-pinene was added, showed an ice nucleation enhancement after the aging at −35 °C. Wood burning particles also act as ice nuclei (IN) at −40 °C in the deposition mode at the same conditions as for diesel particles and photochemical aging did also not alter the ice formation properties of the wood burning particles. Unlike diesel particles, wood burning particles form ice via condensation freezing at −35 °C with no ice nucleation observed at −30 °C for wood burning particles. Photochemical aging did not affect the ice nucleation ability of the diesel and wood burning particles at the three different temperatures investigated but a broader range of temperatures below −30 °C need to be investigated in order to draw an overall conclusion on the effect of photochemical aging on deposition/condensation ice nucleation across the entire temperature range relevant to cold clouds.

scholarly journals Effect of photochemical ageing on the ice nucleation properties of diesel and wood burning particles

2013 ◽  
Vol 13 (2) ◽  
pp. 761-772 ◽  
Author(s):  
C. Chou ◽  
Z. A. Kanji ◽  
O. Stetzer ◽  
T. Tritscher ◽  
R. Chirico ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Chemical Properties ◽  
Diesel Oxidation Catalyst ◽  
Ice Nucleation ◽  
Oxidation Catalyst ◽  
Ice Formation ◽  
Diesel Vehicles ◽  
Diesel Particles ◽  
Wood Burning ◽  
Deposition Mode

Abstract. A measurement campaign (IMBALANCE) conducted in 2009 was aimed at characterizing the physical and chemical properties of freshly emitted and photochemically aged combustion particles emitted from a log wood burner and diesel vehicles: a EURO3 Opel Astra with a diesel oxidation catalyst (DOC) but no particle filter and a EURO2 Volkswagen Transporter TDI Syncro without emission aftertreatment. Ice nucleation experiments in the deposition and condensation freezing modes were conducted with the Portable Ice Nucleation Chamber (PINC) at three nominal temperatures, −30 °C, −35 °C and −40 °C. Freshly emitted diesel particles showed ice formation only at −40 °C in the deposition mode at 137% relative humidity with respect to ice (RHi) and 92% relative humidity with respect to water (RHw), and photochemical ageing did not play a role in modifying their ice nucleation behaviour. Only one diesel experiment where α-pinene was added for the ageing process, showed an ice nucleation enhancement at −35 °C. Wood burning particles also act as ice nuclei (IN) at −40 °C in the deposition mode at the same conditions as for diesel particles and photochemical ageing also did not alter the ice formation properties of the wood burning particles. Unlike diesel particles, wood burning particles form ice via condensation freezing at −35 °C whereas no ice nucleation was observed at −30 °C. Photochemical ageing did not affect the ice nucleation ability of the diesel and wood burning particles at the three different temperatures investigated but a broader range of temperatures below −40 °C need to be investigated in order to draw an overall conclusion on the effect of photochemical ageing on deposition/condensation ice nucleation across the entire temperature range relevant to cold clouds.

THE ICE NUCLEATION BEHAVIOR OF AMINO-ACID PARTICLES

1966 ◽  
Vol 44 (10) ◽  
pp. 2431-2445 ◽  
Author(s):  
J. Maybank ◽  
N. Barthakur
Keyword(s):  
Amino Acid ◽  
Liquid Phase ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Cloud Chamber ◽  
Airborne Particles ◽  
Ice Formation ◽  
Vapor Pressures ◽  
Nucleation Behavior ◽  
Threshold Temperatures

The problem of whether ice nucleation takes place more readily from the vapor directly to the solid, or via an intermediate liquid phase has been studied for several of the more efficient amino-acid nucleators. It has been shown that the threshold temperatures observed in cloud chamber tests are in fact those of the material acting as freezing nuclei (i.e. via the liquid phase), and any discrepancies between such tests and trials with bulk water may be accounted for satisfactorily by partial destruction of the nucleus surface by the water. Investigations on ice formation about airborne particles and on macroscopic amino-acid crystals have shown that for certain of these substances a transition in behavior takes place around −20 °C. Below this temperature, ice formation no longer requires saturation conditions with respect to supercooled water and so the particles may be considered to act by converting the vapor directly to ice, and can, therefore, be designated sublimation nuclei.The major obstacle in the way of airborne particles acting as freezing nuclei has been the requirement that they act first as condensation centers. Under the conditions prevailing in supercooled clouds with vapor pressures equal to, or barely exceeding that of water saturation, condensation is unlikely on the somewhat hydrophobic surfaces of amino-acid particles. It has been shown, however, by using a radioactive tracer in small water droplets that droplet–particle collisions can occur. While not efficient, this process would permit a few particles in a cloud chamber experiment to act as freezing nuclei, thereby establishing the potential activity of the material itself.

scholarly journals Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures

2005 ◽  
Vol 5 (3) ◽  
pp. 3391-3436 ◽  
Author(s):  
C. M. Archuleta ◽  
P. J. DeMott ◽  
S. M. Kreidenweis
Keyword(s):  
Sulfuric Acid ◽  
Relative Humidity ◽  
Mineral Dust ◽  
Aerosol Particles ◽  
Diffusion Chamber ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Nucleation Behavior ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. This study examines the potential role of some types of mineral dust and mineral dust with sulfuric acid coatings as heterogeneous ice nuclei at cirrus temperatures. Commercially-available nanoscale powder samples of aluminum oxide, alumina-silicate and iron oxide were used as surrogates for atmospheric mineral dust particles, with and without multilayer coverage of sulfuric acid. A sample of Asian dust aerosol particles was also studied. Measurements of ice nucleation were made using a continuous-flow ice-thermal diffusion chamber (CFDC) operated to expose size-selected aerosol particles to temperatures between −45 and −60°C and a range of relative humidity above ice-saturated conditions. Pure metal oxide particles supported heterogeneous ice nucleation at lower relative humidities than those required to homogeneously freeze sulfuric acid solution particles at sizes larger than about 50 nm. The ice nucleation behavior of the same metal oxides coated with sulfuric acid indicate heterogeneous freezing at lower relative humidities than those calculated for homogeneous freezing of the diluted particle coatings. The effect of soluble coatings on the ice activation relative humidity varied with the respective uncoated core particle types, but for all types the heterogeneous freezing rates increased with particle size for the same thermodynamic conditions. For a selected size of 200 nm, the natural mineral dust particles were the most effective ice nuclei tested, supporting heterogeneous ice formation at an ice relative humidity of approximately 135%, irrespective of temperature. Modified homogeneous freezing parameterizations and theoretical formulations are shown to have application to the description of heterogeneous freezing of mineral dust-like particles with soluble coatings.

scholarly journals Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures

2005 ◽  
Vol 5 (10) ◽  
pp. 2617-2634 ◽  
Author(s):  
C. M. Archuleta ◽  
P. J. DeMott ◽  
S. M. Kreidenweis
Keyword(s):  
Sulfuric Acid ◽  
Relative Humidity ◽  
Mineral Dust ◽  
Aerosol Particles ◽  
Diffusion Chamber ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Nucleation Behavior ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. This study examines the potential role of some types of mineral dust and mineral dust with sulfuric acid coatings as heterogeneous ice nuclei at cirrus temperatures. Commercially-available nanoscale powder samples of aluminum oxide, alumina-silicate and iron oxide were used as surrogates for atmospheric mineral dust particles, with and without multilayer coverage of sulfuric acid. A sample of Asian dust aerosol particles was also studied. Measurements of ice nucleation were made using a continuous-flow ice-thermal diffusion chamber (CFDC) operated to expose size-selected aerosol particles to temperatures between -45 and -60°C and a range of relative humidity above ice-saturated conditions. Pure metal oxide particles supported heterogeneous ice nucleation at lower relative humidities than those required to homogeneously freeze sulfuric acid solution particles at sizes larger than about 50 nm. The ice nucleation behavior of the same metal oxides coated with sulfuric acid indicate heterogeneous freezing at lower relative humidities than those calculated for homogeneous freezing of the diluted particle coatings. The effect of soluble coatings on the ice activation relative humidity varied with the respective uncoated core particle types, but for all types the heterogeneous freezing rates increased with particle size for the same thermodynamic conditions. For a selected size of 200 nm, the natural mineral dust particles were the most effective ice nuclei tested, supporting heterogeneous ice formation at an ice relative humidity of approximately 135%, irrespective of temperature. Modified homogeneous freezing parameterizations and theoretical formulations are shown to have application to the description of heterogeneous freezing of mineral dust-like particles with soluble coatings.

scholarly journals Cold-Tolerance Mechanisms of the Antarctic Nematode Panagrolaimus Davidi

1991 ◽  
Vol 155 (1) ◽  
pp. 629-641
Author(s):  
D. A. WHARTON ◽  
I. M. BROWN
Keyword(s):  
Surface Water ◽  
Relative Humidity ◽  
Freezing Tolerance ◽  
Thermal History ◽  
Liquid Paraffin ◽  
Ice Nucleation ◽  
Ice Formation ◽  
Tolerance Mechanisms ◽  
The Antarctic

When free of surface water in air or liquid paraffin, the antarctic nematode Panagrolaimus davidi is freezing intolerant but avoids freezing by supercooling. Survival of long-term exposure is enhanced by sub-zero temperatures compared with controls maintained at 99% relative humidity and 15°C. In water the nematodes are seeded by exogenous ice nucleation and a proportion are freezing tolerant. Ice formation appears to be restricted to the pseudocbel. The degree of freezing tolerance is dependent upon the age of the culture and its thermal history. P. davidi is freezing tolerant when exposed to sub-zero temperatures in water and freezing intolerant when free of surface water and able to supercool. These two strategies are not mutually exclusive as they are often thought to be in arthropods.

scholarly journals The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 336
Author(s):  
Deniz Zengel ◽  
Simon Barth ◽  
Maria Casapu ◽  
Jan-Dierk Grunwaldt
Keyword(s):  
Catalytic Reduction ◽  
Elevated Pressure ◽  
Systematic Investigation ◽  
Diesel Oxidation Catalyst ◽  
Zeolite Catalysts ◽  
Oxidation Catalyst ◽  
Pollutant Concentrations ◽  
Oxidation Of Hydrocarbons ◽  
Negative Effect ◽  
The Impact

Positioning the catalysts in front of the turbocharger has gained interest over recent years due to the earlier onset temperature and positive effect of elevated pressure. However, several challenges must be overcome, like presence of higher pollutant concentrations due to the absence or insufficient diesel oxidation catalyst volume at this location. In this context, our study reports a systematic investigation on the effect of pressure and various hydrocarbons during selective catalytic reduction (SCR) of NOx with NH3 over the zeolite-based catalysts Fe-ZSM-5 and Cu-SSZ-13. Using a high-pressure catalyst test bench, the catalytic activity of both zeolite catalysts was measured in the presence and absence of a variety of hydrocarbons under pressures and temperatures resembling the conditions upstream of the turbocharger. The results obtained showed that the hydrocarbons are incompletely converted over both catalysts, resulting in numerous byproducts. The emission of hydrogen cyanide seems to be particularly problematic. Although the increase in pressure was able to improve the oxidation of hydrocarbons and significantly reduce the formation of HCN, sufficiently low emissions could only be achieved at high temperatures. Regarding the NOx conversion, a boost in activity was obtained by increasing the pressure compared to atmospheric reaction conditions, which compensated the negative effect of hydrocarbons on the SCR activity.

Development of a Low Emissions Upgrade Kit for EMD GP20D and GP15D Locomotives

2012 ◽  
Author(s):  
Steven G. Fritz ◽  
John C. Hedrick ◽  
Tom Weidemann
Keyword(s):  
Fuel Injection ◽  
Diesel Oxidation Catalyst ◽  
Oxidation Catalyst ◽  
Particulate Filter ◽  
Injection Timing ◽  
Fuel Injection Timing ◽  
Tier 1 ◽  
Emission Regulations ◽  
Diesel Oxidation ◽  
Tier 3

This paper describes the development of a low emissions upgrade kit for EMD GP20D and GP15D locomotives. These locomotives were originally manufactured in 2001, and met EPA Tier 1 locomotive emission regulations. The 1,491 kW (2,000 HP) EMD GP20D locomotives are powered by Caterpillar 3516B engines, and the 1,119 kW (1,500 HP) EMD GP15D locomotives are powered by Caterpillar 3512B engines. CIT Rail owns a fleet of 50 of these locomotives that are approaching their mid-life before first overhaul. Baseline exhaust emissions testing was followed by a low emissions retrofit development focusing on fuel injection timing, crankcase ventilation filtration, and application of a diesel oxidation catalyst (DOC), and then later a diesel particulate filter (DPF). The result was a EPA Tier 0+ certification of the low emissions upgrade kit, with emission levels below EPA Line-Haul Tier 3 NOx, and Tier 4 HC, CO, and PM levels.

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