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Particle Phase (particle + phase)
Selected AbstractsEnvironmental factors affecting the levels of legacy pesticides in the airshed of Delaware and Chesapeake Bays, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2010Anubha Goel Abstract Organochlorine insecticides and their degradation products contribute to toxicity in Chesapeake Bay, USA, sediments and affect the reproductive health of avian species in the region; however, little is known of atmospheric sources or temporal trends in concentrations of these chemicals. Weekly air (n,=,265) and daily rain samples (n,=,494) were collected over 2000 to 2003 from three locations in the Delmarva Peninsula, USA. Pesticides were consistently present in the gas phase with infrequent detection in the particle phase. Hexachlorocyclohexanes (HCHs) and cis - and trans -chlordane were detected most frequently (95,100%), and cis - and trans -nonachlor, oxychlordane, heptachlor, heptachlor epoxide, dieldrin, and 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene (4,4,-DDE) were also detected frequently. The highest mean air concentrations were for dieldrin (60,84,pg/m3), ,-HCH (37,83,pg/m3), and 4,4,-DDE (16,80,pg/m3). Multiple regression analyses of air concentrations with temperature and wind conditions using modified Clausius-Clapeyron equations explained only 30 to 60% of the variability in concentration for most chemicals. Comparison of the air concentrations and enthalpy of air,surface exchange values at the three sites indicate sources of chlordanes and ,-HCH sources are primarily from long-range transport. However, examination of chlordane isomer ratios indicates some local and regional contributions, and ,-HCH, 4,4,-DDE, dieldrin, heptachlor, heptachlor epoxide, and oxychlordane also have local or regional sources, possibly from contaminated soils. Median rain sample volumes of 1 to 3 L led to infrequent detections in rain; however, average measured concentrations were 2 to 10 times higher than in the Great Lakes. Dissipation half-lives in air were well below 10 years for all chemicals and below published values for the Great Lakes except dieldrin, which did not decline during the sample period. Environ. Toxicol. Chem. 2010;29:1893,1906. © 2010 SETAC [source] Water-column concentrations and partitioning of polybrominated diphenyl ethers in the New York/New Jersey Harbor, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2008Archil Zarnadze Abstract Despite the emerging concern regarding polybrominated diphenyl ethers (BDEs), very few measurements of BDE concentrations in ambient water have been published. In the present study, BDEs were measured in water samples from the New York/New Jersey Harbor (USA). Samples were taken in Raritan Bay west of Sandy Hook during four intensive sampling campaigns in 2000 and 2001. Congeners 17, 47, 99, 100, 153, 154, 183, and 209 were detected. Total BDE (,BDE) concentrations (average ± standard deviation) were 175 ± 75 ng/g in the particle phase and 110 ± 72 pg/L in the apparent dissolved phase. The deca-congener, BDE 209, constituted 85 and 9% of ,BDEs in the particle and apparent dissolved phases, respectively. The ,BDE levels are significantly higher than those measured in Lake Ontario, USA, and in The Netherlands, but they are similar to concentrations measured in Lake Michigan and San Francisco Bay (both USA). Calculated values of the organic carbon-water partition coefficient (KOC) were strongly correlated with literature values of the octanol-water partition coefficient (KOW). The data suggest that sorption of BDEs to colloids is important in this system, although quantifying the extent of colloid sorption is difficult. [source] Laminar diffusion of suspended particulate matter using a two phase flow modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2002T. C. Panda Abstract The present paper envisages laminar mixing of a two-dimensional jet of particulate suspension in an incompressible carrier fluid with a free stream in direction of the jet axis. Finite difference technique has been employed for finding out solution of governing equations. It is found that the diffusion parameter ,, the ratio of particle diffusion coefficient and kinematic viscosity of the carrier fluid, have significant influence on the concentration of particles. A large value of , has the effect in increasing the perturbation velocity up and perturbation density ,p. It is observed that the volume fraction ,, has no significant effect on perturbation velocity u and up but has profound effect on perturbation velocity v and vp. It is also found that the particle phase as well as the carrier fluid velocity attain free stream value for the large ,, the modified x -co-ordinate. Further the magnitude of the perturbation quantities u, up, v, vp decreases as , increases i.e. at far away from the nozzle exit. Copyright © 2002 John Wiley & Sons, Ltd. [source] CFD modeling of the Wurster bed coaterAICHE JOURNAL, Issue 10 2009Stina Karlsson Abstract In the Wurster bed coater, the wetting, drying, and circulation of particles are combined to produce a high quality coating. The drying and wetting conditions in a laboratory scale Wurster bed coater are modeled and compared with experimental data. A model combining multiphase fluid dynamics with heat and mass transfer is developed to model the particle and gas motion and the transport of thermal energy and moisture. A wetting region is defined, where a specified moisture content is set in the particle phase, above the jet inlet, to describe the injection of coating liquid. The simulation shows the characteristic circulation of particles in the equipment, as well as the behavior of the moisture in the system and agrees well with measurements. The simulation indicates how different process conditions influence the drying regions. The results show that most of the drying, under typical operating conditions, takes place in the Wurster tube. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] An Improved LES on Dense Particle-Liquid Turbulent Flows Using Integrated Boltzmann EquationsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2007Xuelin Tang Abstract An improved large eddy simulation (LES) using a dynamic second-order subgrid stress (SGS) model has been developed for simulating dense particle-liquid two-phase turbulent flows. The governing equations of each phase are obtained from a microscopic point of view, using the kinetic theory of molecular gas. They are derived by multiplying the Boltzmann equation of each phase by property parameters and integrating over the velocity space. An inter-particle collision term is included in the governing equation of the particle phase. Assuming a Maxwellian distribution of the velocity for particle-phase, an inter-particle collision term is derived. On a amélioré la simulation des grands tourbillons (LES) à l'aide d'un modèle de contraintes dans les mailles inférieures (SGS) de second ordre dynamique afin de simuler des écoulements turbulents diphasiques particules-liquide. Les équations gouvernantes de chaque phase sont obtenues d'un point de vue microscopique, au moyen de la théorie cinétique du gaz moléculaire. Elles sont calculées en multipliant l'équation de Boltzmann de chaque phase par des paramètres de propriétés et en intégrant sur l'intervalle des vitesses. Un terme de collision inter-particulaire est inclus dans l'équation gouvernante de la phase des particules. [source] Uniform Polymeric Hollow Microcapsules with Controlled Doping Levels Fabricated under Nonreactive Conditions,ADVANCED MATERIALS, Issue 8 2007K. Wygladacz A chemically nonreactive method for the fabrication of uniform core/shell fluorescent polymeric microspheres (see figure) is demonstrated with a flow apparatus. Various dyes and labeled proteins are doped into the appropriate particle phases, and an early example of chemical sensing is demonstrated. [source] |