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

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.

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

A 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.

Characteristics of Dry Ice Particles Produced by Expanding Liquid Carbon Dioxide and its Application for Surface Cleaning

The characteristics of dry ice particles produced by expanding liquid carbon dioxide and its application for surface cleaning have been studied experimentally. The production of the dry ice particles was based on the Joule-Thomson effect. The ejected dry ice particles were observed using a high-speed microscope camera. Through digital image processing, the particle size and particle velocity in the jet were analyzed. To in-situ measure the size distribution of the dry ice particles, a laser diffraction method was used. The experimental results showed that the primary dry ice particles ejected from the expansion nozzle were about 1 μm in mass median diameter. The presence of a thermally insulated tube at the outlet of the nozzle enhanced the agglomeration of the particles, whereby agglomerates of about 100 μm in mass median diameter were formed. The performance of dry ice jet for removing fine particles adhering to surfaces was also evaluated using microscopic observation. It was found that the particle removal process consists of two stagesslow removal stage and rapid removal stagethat are related to the jet temperature.

Role of Initial Melt Inventory on Debris Generation With Woods Metal Water Interaction Under Drop Mode

Thermal interaction of a hot liquid with a cold volatile liquid was investigated with woods metal melt water system at first contact temperature just above the spontaneous nucleation temperature of water. Drop mode experiments were carried out up to 1000 g of melt and resulting debris sizes and shapes were analyzed. Experiment was carried out with melt temperature of 425 °C and water pool at 30 °C. One of the 100 g run resulted in an energetic interaction with a mass median diameter 2.5 mm ± 1.58. The MMD is seen to change to higher values for non-energetic cases and higher melt inventories. Dynamic pressure signals are also recorded. Relative contribution of thermal and hydrodynamic fragmentation is assessed in pool and narrow geometries. Dependence of mass median diameter on initial melt inventory has been brought out.

Study on Jet Breakup Behavior at Core Disruptive Accident for Fast Breeder Reactor

It is important to estimate the cooling possibility of the molten jet in coolant during a core disruptive accident (CDA) of a fast breeder reactor (FBR). In the present study, the molten jet of U-alloy 78 simulating the core material is injected into the water simulating the coolant. The visual data of the molten jet breakup behavior is observed by using the high-speed video camera. The front velocity of the molten jet is estimated by using the image processing technique from the visual data. It shows that the front velocity of the molten jet can be divided into three time regions. In the first region, the front velocity of the molten jet increases. In the second region, the front velocity of the molten jet suddenly decreases. In the third region, the front velocity of the molten jet keeps at low and steady. In first region, the column diameter of the molten jet decreases with the passage of time. At the location between first region and second region, the column of the molten jet breaks up and disappears. In the present study, the jet breakup length is defined as the distance from the water surface to the location where the jet column disappears. The results show that the jet breakup length depends on the injection nozzle diameter, but does not depend on the jet penetration velocity. This tendency agrees with the prediction by Epstein’s equation. After the experiment, the solidified fragments are collected and the mass median diameter is measured. The mass median diameter is compared with the existing theories. Furthermore, a model to estimate the cooling possibility during a CDA of a FBR is constructed, reflecting the above-mentioned results.