scholarly journals Compositional Variation of PCBs, PAHs, and OCPs at Gas Phase and Size Segregated Particle Phase during Dust Incursion from the Saharan Desert in the Northwestern Anatolian Peninsula

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
S. Levent Kuzu
Keyword(s):  
Size Distribution ◽  
Regression Line ◽  
Compositional Variation ◽  
Particle Phase ◽  
Atmospheric Conditions ◽  
Bimodal Size Distribution ◽  
Anatolian Peninsula ◽  
Median Diameter ◽  
Favorable Conditions ◽  
Mass Median Diameter

A dust incursion occurred in Istanbul on 1 February 2015 from the Saharan Desert. During this episode, 938 μg·m−3of TSP concentration was observed. TSP concentration was 64 μg·m−3and 78 μg·m−3on the following two days. Particles of 3 μm were dominant during the episode; however, particles < 0.49 μm were dominant after the episode. The averages of total (gas + particle) PCB, PAH, and OCP concentrations were 279 pg·m−3, 175 ng·m−3, and 589 pg·m−3, respectively. Tri-CBs were dominant in most of the samples. Flt and Phe had the highest contribution to PAH species.β-HCH and heptachlor had the highest share in terms of OCPs. Particle phase PCBs exhibited monomodal size distribution, whereas OCPs had bimodal size distribution. PAHs exhibited either monomodal or bimodal size distribution on different days. The mass median diameter of PAHs did not change significantly during different atmospheric conditions due to their local sources. Gas/particle partitioning of each pollutant was evaluated by plotting their subcooled vapor pressure against the partitioning coefficient. From 1 to 3 February, the slope of the regression line shifted close to −1, indicating that the least favorable conditions were present during dust incursion for an equilibrium state.

scholarly journals Microwave Properties of Ice-Phase Hydrometeors for Radar and Radiometers: Sensitivity to Model Assumptions

2012 ◽  
Vol 51 (12) ◽  
pp. 2152-2171 ◽  
Author(s):  
Benjamin T. Johnson ◽  
Grant W. Petty ◽  
Gail Skofronick-Jackson
Keyword(s):  
Brightness Temperature ◽  
Size Distribution ◽  
Radar Reflectivity ◽  
Index Of Refraction ◽  
Microwave Properties ◽  
Complex Index ◽  
Median Diameter ◽  
Mass Median ◽  
Mass Median Diameter ◽  
Complex Index Of Refraction

AbstractA simplified framework is presented for assessing the qualitative sensitivities of computed microwave properties, satellite brightness temperatures, and radar reflectivities to assumptions concerning the physical properties of ice-phase hydrometeors. Properties considered included the shape parameter μ of a gamma size distribution and the melted-equivalent mass median diameter D0, the particle density, the dielectric mixing formula, and the choice of complex index of refraction for ice. These properties are examined for selected radiometer frequencies of 18.7, 36.5, 89.0, and 150.0 GHz and radar frequencies at 2.8, 13.4, 35.6, and 94.0 GHz—consistent with existing and planned remote sensing instruments. Passive and active microwave observables of ice particles are found to be extremely sensitive to the D0 of the size distribution. Similar large sensitivities are found for variations in the ice volume fraction whenever the geometric mass median diameter exceeds approximately ⅛th of the wavelength. At 94 GHz the two-way path-integrated attenuation is potentially large for dense/compact particles. The distribution parameter μ has a comparatively weak effect on any observable: less than 1–2 K in brightness temperature and a maximum of 2.7 dB (S band only) in the effective radar reflectivity. Reversal of the roles of ice and air in the Maxwell Garnett dielectric mixing formula leads to a substantial change in both microwave brightness temperature (~10 K) and radar reflectivity (approximately 2 dB across all frequencies). The choice of the complex index of refraction of ice can produce a 3%–4% change in the brightness temperature depression.

Aircraft Applications of Insecticides in East Africa. VI.—Applications of a coarse Aerosol containning DDT to control the Tsetse Flies, Glossina morsitans Westw., Glossina swynnertoni Aust. and Glossina pallidipes Aust.

1954 ◽  
Vol 45 (3) ◽  
pp. 585-603 ◽  
Author(s):  
K. S. Hocking ◽  
D. Yeo ◽  
D. G. Anstey
Keyword(s):  
Random Effects ◽  
Glossina Pallidipes ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Median Diameter ◽  
Coarse Aerosol ◽  
Savannah Woodland ◽  
Mass Median ◽  
Glossina Swynnertoni ◽  
Mass Median Diameter

An experiment is described where applications of a coarse aerosol were made to savannah woodland containing the tsetse flies, Glossina moritans Westw., G. swynnertoni Aust. and G. pallidipes Aust.Seven applications were made, each at a nominal dosage of 0·25 lb. of technical DDT per acre and 0·25 gallons of solution per acre. The applications in any particular part of the treaed woodland covered an interval of 90 days, or rather more than two pupal periods.The coarse aerosol was produced by emitting the insecticidal solution under pressure through fine nozzles fitted to a boom. It had a mass median diameter of approximately 60 microns, and droplet dismeters varied from a few microns to approximately 200 microns.The population of G. pallidipes was so drastically reduced that it has subsequently dies out. The reduction of G. morsitans was approximately 95 per cent. The differences between the reductions are attributed mainly to differences between the ease with which the three species can be killed. It is pointed out that this is not necessarily equivalent to differences in susceptibility.Comparisons are made with previous experiments, and the different results of the various experiments are difficult to explian satisfactory. The increased cover in savannah areas during the leafy period may have reduced the effectiveness of the applications, and the total periods covered by the various series of applications were probably also important. Random effects, leading to ineffective treatments, may also be important.Costs are discussed.

Experimental Study on Jet Breakup Behavior With Surface Solidification

2010 ◽  
Author(s):  
Takashi Wada ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuta Uchiyama ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Size Distribution ◽  
Reactor Vessel ◽  
Image Processing Technique ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Median Diameter

For the safety design of the Fast Breeder Reactor (FBR), the Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In the PAHR, it is strongly required that the molten core material can be cooled down and solidified by the sodium coolant in the reactor vessel. There is high possibility for molten material to be ejected as a liquid jet into sodium coolant in the reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant or not, it is necessary to understand the interaction between molten core material and coolant such as jet breakup and fragmentation behavior in coolant. The jet breakup behavior is the phenomenon that the front of molten material breaks up in coolant. To clarify the mechanism of jet breakup and fragmentation during the CDA for the FBR, it is necessary to understand the correlation between jet breakup lengths and size distribution of fragments when molten material jet interacting with coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size distribution of fragments experimentally. Molten jet of U-alloy 138 is injected into water as simulated core material and coolant by free-fall. The density ratio of core material and coolant is almost same as that of the real FBR system. The jet breakup behavior as interaction of molten material with coolant is observed with high speed video camera. Front velocity of the molten material jet is estimated by using the image processing technique. It suddenly decreases when the jet fall into the coolant. The jet breakup length estimated from observed images is compared with the breakup theories to understand the effect of experimental parameters for the jet breakup length. The solidified fragments are gathered and classified in size, and the mass in each size is measured. Median diameter is obtained from the mass distribution of the fragments. In comparison with interfacial instabilities, the median diameter of fragments shows the independent of relative velocity. The jet breakup lengths and median diameters compared with existing theories is discussed.

scholarly journals Aged boreal biomass burning aerosol size distributions from BORTAS 2011

2014 ◽  
Vol 14 (17) ◽  
pp. 24349-24385 ◽  
Author(s):  
K. M. Sakamoto ◽  
J. D. Allan ◽  
H. Coe ◽  
J. W. Taylor ◽  
T. J. Duck ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Climate Model ◽  
Sampling Period ◽  
Characteristic Size ◽  
Entrainment Rate ◽  
Size Distributions ◽  
Eastern Canada ◽  
Median Diameter

Abstract. Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ∼1–2 days) from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter), σ = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (ΔOA / ΔCO) along the path of Flight b622 show values of 0.05–0.18 μg m−3 ppbv−1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ΔOA / ΔCO enhancement ratios. We estimate that the fresh-plume median diameter was in the range of 59–94 nm with modal widths in the range of 1.7–2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.

Regional and Transported A erosols in Ambient A tmosphere of Raipur,India, during W inter

2021 ◽  
Vol 30 (1) ◽  
pp. 7-17
Author(s):  
Manas Kanti Deb ◽  
Mithlesh Mahilang ◽  
Jayant Nirmalkar
Keyword(s):  
Size Distribution ◽  
Long Range ◽  
Fine Particles ◽  
Characteristic Size ◽  
Long Range Transport ◽  
Bimodal Size Distribution ◽  
Entire Study ◽  
Coarse Mode ◽  
Range Transport ◽  
Air Trajectory

Size fractionated atmospheric aerosols were collected using cascade impactor sampler on quartz flter substrate during October 2015 to February 2016 in campus of Pt Ravishankar Shukla University of Raipur Chhattisgarh. The size of aerosol particles is of crucial importance to several processes in the atmosphere. The relative concentrations in both modes are responsible for the variability observed in the shape of the size distribution. Characteristic size distributions of measured aerosol over central India showed identifcation of three main behaviour types during entire study period: (i) month in which bimodal size distribution dominated in coarse mode (October 2015, 5 December 2015 and January, 2016), (ii) those months in which bimodal distribution equally intense in both one, and coarse modes (November, 2015) and (iii) those which were mainly dominated within fine (February, 2016, December, 2015). The two-subsequent month namely November 2015 and December 2015 shows bimodal size distribution with dominance in fine size range in comparison to coarse mode, possibly these high loading of one particles is due to long range transport. The peculiar observation of air trajectory shows that there is increase in fine particles concentration during December 2015, although there in increase in temperature and wind speed. The reason for this high concentration is long range transport of air masses. However, January has normal trend in particular matter concentration. The important finding of the present study based on characteristic size distribution and air trajectory plots accomplishes that fine particles are obtained through long range transport whereas coarse particles are mainly from local origin.

scholarly journals Diesel exhaust nanoparticles and their behaviour in the atmosphere

2018 ◽  
Vol 474 (2220) ◽  
pp. 20180492 ◽  
Author(s):  
Roy M. Harrison ◽  
A. Rob MacKenzie ◽  
Hongming Xu ◽  
Mohammed S. Alam ◽  
Irina Nikolova ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Size Distribution ◽  
Diesel Exhaust ◽  
Dynamical Behaviour ◽  
Air Pollutant ◽  
Diesel Exhaust Particles ◽  
Atmospheric Conditions ◽  
Engine Exhaust ◽  
Number Count ◽  
Model Studies

Diesel engine emissions are by far the largest source of nanoparticles in many urban atmospheres, in which they dominate the particle number count, and may present a significant threat to public health. This paper reviews knowledge of the composition and atmospheric properties of diesel exhaust particles, and exemplifies research in this field through a description of the FASTER project (Fundamental Studies of the Sources, Properties and Environmental Behaviour of Exhaust Nanoparticles from Road Vehicles) which studied the size distribution—and, in unprecedented detail, the chemical composition—of nanoparticles sampled from diesel engine exhaust. This information has been systematized and used to inform the development of computational modules that simulate the behaviour of the largely semi-volatile content of the nucleation mode particles, including consequent effects on the particle size distribution, under typical atmospheric conditions. Large-eddy model studies have informed a simpler characterization of flow around the urban built environment, and include aerosol processes. This modelling and engine-laboratory work have been complemented by laboratory measurements of vapour pressures, and the execution of two field measurement campaigns in London. The result is a more robust description of the dynamical behaviour on the sub-kilometre scale of diesel exhaust nanoparticles and their importance as an urban air pollutant.

The Possible Site of Action of Sodium Cromoglycate Assessed by Exercise Challenge

1974 ◽  
Vol 46 (2) ◽  
pp. 265-272 ◽  
Author(s):  
S. Godfrey ◽  
E. Zeidifard ◽  
K. Brown ◽  
J. H. Bell
Keyword(s):  
Sodium Cromoglycate ◽  
Particle Sizes ◽  
Post Exercise ◽  
Asthmatic Patients ◽  
Exercise Challenge ◽  
Site Of Action ◽  
Median Diameter ◽  
Mass Median ◽  
Spinning Disc ◽  
Mass Median Diameter

1. The protective effect of different particle sizes of sodium cromoglycate (SCG) was assessed by exercise challenge in nine asthmatic patients. 2. SCG particles of 11·7 μm or 2·0 μm mass median diameter were generated by a spinning disc and compared with lactose placebo particles. The drugs were given 10 min before a 6 min run on a treadmill. 3. The post-exercise bronchoconstriction caused a 48% fall in peak flow rate in the placebo test, a 41% fall after the large SCG particles and a 20% fall after the small particles. 4. It is concluded that the site of action of SCG is probably in the smallest airways.

Aircraft Applications of Insecticides in East Africa. II.—An experimental Attempt to Produce a Fly-free Corridor through a Belt of Tsetse-infested Woodland

1953 ◽  
Vol 44 (3) ◽  
pp. 601-609 ◽  
Author(s):  
K. S. Hocking ◽  
H. C. M. Parr ◽  
D. Yeo ◽  
P. A. Robins
Keyword(s):  
East Africa ◽  
Wind Direction ◽  
Tsetse Fly ◽  
Low Level ◽  
Median Diameter ◽  
Savannah Woodland ◽  
Mass Median ◽  
Mass Median Diameter

An experimental attempt was made to produce a fly-free corridor through a belt of savannah woodland containing the tsetse fly G. swynnertoni.An area two miles wide and four miles long was treated with a coarse spray of a 4·6 per cent, w/v solution of DDT in Shell Diesoline. The dosage per application was 0·5 gallons per acre, and seven applications were made, at intervals of approximately two weeks, so that the treatment covered two pupal periods.The fly density had fallen to a very low level by the end of the experiment, and the area remained virtually free from flies for the subsequent two months. An examination of the data suggests, however, that the fly population was maintained largely by immigrant flies, and was certainly subject to wide variations, and it seems certain that the effect of the applications would have been considerably less upon a stable, self-supporting population.The drop spectrum of the ground deposit had a mass median diameter of 0·35 mm., and the recovery of insecticide in the area was approximately 60 per cent. Leeward and under sides of obstacles did not receive a dose although in some cases dosages were obtained on apparently leeward sides, probably because of local reversals of wind direction.

The Correlation of Drop-Size Distributions in Fuel Nozzle Sprays—Part I: The Drop-Size/Volume-Fraction Distribution

1977 ◽  
Vol 99 (3) ◽  
pp. 309-314 ◽  
Author(s):  
H. C. Simmons
Keyword(s):  
Drop Size ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Different Types ◽  
Median Diameter ◽  
Fraction Distribution ◽  
Fuel Nozzle ◽  
Drop Size Distributions ◽  
Mass Median ◽  
Mass Median Diameter

The paper presents data on the drop-size/volume-fraction distributions of sprays observed with a large number of gas-turbine fuel nozzles of different types including both pressure and air-atomizers, using a range of fuel viscosities, at a variety of operating conditions. The data were obtained by both optical and wax-droplet methods. It is shown that a universal nondimensional correlation can be established for all the fuel nozzles when the drop-size is normalized to the mass median diameter. The correlation enables prediction of the drop-size/volume-fraction distribution for a spray given only the mass median or Sauter mean diameter.

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