Using a moving measurement platform for determining the chemical composition of atmospheric aerosols between Moscow and Vladivostok

The TROICA-9 expedition (Trans-Siberian Observations Into the Chemistry of the Atmosphere) was carried out at the Trans-Siberian railway between Moscow and Vladivostok in October 2005. Measurements of aerosol physical and chemical properties were made from an observatory carriage connected to a passenger train. Black carbon (BC) concentrations in fine particles (PM<sub>2.5</sub>, aerodynamic diameter <2.5 μm) were measured with an aethalometer using a five-minute time resolution. Concentrations of inorganic ions and some organic compounds (Cl<sup>−</sup>, NO<sub>3</sub><sup>−</sup>, SO<sub>4</sub><sup>2−</sup>, Na<sup>+</sup>, NH<sub>4</sub><sup>+</sup>, K<sup>+</sup>, Ca<sup>2+</sup>, Mg<sup>2+</sup>, oxalate and methane sulphonate) were measured continuously by using an on-line system with a 15-min time resolution. In addition, particle volume size distributions were determined for particles in the diameter range 3–850 nm using a 10-min time resolution. The continuous measurements were completed with 24-h PM<sub>2.5</sub> filter samples stored in a refrigerator and analyzed later in a chemical laboratory. The analyses included the mass concentrations of PM<sub>2.5</sub>, ions, monosaccharide anhydrides (levoglucosan, galactosan and mannosan) and trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, V and Zn). The mass concentrations of PM<sub>2.5</sub> varied in the range of 4.3–34.8 μg m<sup>−3</sup> with an average of 21.6 μg m<sup>−3</sup>. Fine particle mass consisted mainly of BC (average 27.6%), SO<sub>4</sub><sup>2−</sup> (13.0%), NH<sub>4</sub><sup>+</sup> (4.1%) and NO<sub>3</sub><sup>−</sup> (1.4%). One of the major constituents was obviously organic carbon which was not determined. The contribution of BC was high compared with other studies made in Europe and Asia. High concentrations of ions, BC and particle volume were observed between Moscow and roughly 4000 km east of it, as well as close to Vladivostok, primarily due to local anthropogenic sources. In the natural background area between 4000 and 7200 km away from Moscow, observed concentrations were low, even though local particle sources, such as forest fires, occasionally increased concentrations. During the measured forest fire episodes, most of the aerosol mass appeared to consist of organic particulate matter. Concentrations of the biomass burning tracers levoglucosan, oxalate and potassium were elevated close to the forest fire areas observed by the MODIS satellite. The polluted air masses from Asia seem to have significant influences on the concentration levels of fine particles over south-eastern Russia

Recommendations for new Experiments able to better Characterize Flashing Flows in nozzles for improving Critical Flow Modelling in System Codes

The FONESYS network of system code developers made a benchmark of eight system codes against Two-Phase Critical Flow (TPCF) experiments, which updated the state of the art in TPCF modelling. 0-D and 1-D TPCF code models still have large prediction errors particularly for slightly sub-cooled inlet conditions. Three main reasons explain these errors: (1) 3D effects in complex geometry, (2) nucleation delay, which depends on non-well-controlled parameters such as purity of water or status of metallic surface, (3) interfacial transfers in rapidly changing non-established flashing flow with unknown flow regimes. It seems possible to progress at least on the third point using new measurements techniques. The SILENCE network of experimentalists in thermal-hydraulics conducted reflections on the type of measurements that should be used in future experiments on TPCF to provide new local information on flow regime, bubble size, film thickness and drop size. This paper first recalls the characteristics of TPCF and summarizes the conclusions of the benchmark of TPCF code models. Then, one presents the limitations of the current modelling, and the limitations of the existing TPCF database. The needs of new measurements are listed. Advanced measurement techniques are reviewed with an evaluation of their applicability to flashing flow in nozzles. Then, recommendations for any new experiment on TPCF are given

Vladivostok

Using a moving measurement platform for determining the chemical composition of atmospheric aerosols between Moscow an

Assessing the impact of initial nonresponse and attrition in the analysis of unemployment duration with panel surveys

Combined survey-register data, Nonresponse analysis, Duration of unemployment,