Geochemistry and solute sources of surface waters of the Tarim River Basin in the extreme arid region, NW Tibetan Plateau

Major ion concentrations of river, lake and snow waters were measured to better understand the water quality, hydrochemical processes and solute sources of surface waters within the Tarim River Basin in the extreme arid region. Surface waters are slightly alkaline and are characterized by high total dissolved solids (TDS). TDS values varies over two orders of magnitude from fresh (76%) to brackish (24%) with a mean value of 1000 mg/L, higher than the global river average and river waters draining the Himalayas and the southeastern Tibetan Plateau. Most of the samples were Ca(2+)-(Mg(2+))-HCO(3)(-) type and suited for drinking and irrigation. Water quality of Aksu River (AK), Hotan River (HT) and Northern Rivers (NR) is better than the others. Rock weathering, ion exchange and precipitation are the major hydrogeochemical processes responsible for the solutes in rivers waters. Anthropogenic input to the water chemistry is minor and human activities accelerate increase of river TDS. The quantitative solute sources are first calculated using a forward model in this area. The results show that evaporite dissolution, carbonate weathering, atmospheric input, and silicate weathering contributed 58.3%, 25.7%, 8.7%, and 8.2% of the total dissolved cations for the whole basin. Evaporite dissolution dominated in Lake Waters (LW), HT, Yarkant River (YK), Tarim River (TR), and Southern Rivers (SR), contributing 73.5%, 53.4%, 56.7%, 77%, and 74.2% of the total dissolved cations, respectively. Carbonate weathering dominated in AK and NR, contributing 48% and 44.4% of the total dissolved cations, respectively. The TDS flux of HT, TR, AK, YK was 66.0, 118.6, 134.9, and 170.4 t/km(2)/yr, respectively, higher than most of the rivers in the world. Knowledge of our research can promote effective management of water resources in this desert environment and add new data to global river database.</p

Atmospheric lead in urban Guiyang, Southwest China: Isotopic sourcesignatures

Total suspended particles (TSP) and their source-related samples from Guiyang, Southwest China, were collected and analyzed for their lead (Pb) concentrations and Pb isotopic compositions, to identify the sources of atmosphere lead in urban Guiyang. Coals from Guizhou Province had significantly high radiogenic Pb, different to those from North China. Local vehicle exhaust had similar Pb isotope ratios to those of other areas in China. Pb isotopic compositions of atmospheric aerosols, rainwaters, plant samples, and acid-soluble fraction of street dusts were similar to each other. The results clearly suggest that the PbeZn ore-related industrial emission, and/or vehicle exhaust, rather than the local coal combustion, are the main sources of atmospheric Pb in Guiyang. Furthermore, binary mixing model indicates that the contribution of coal combustion to the local atmospheric Pb decreased from about 40% in 1988 to about 10% in 2013.</p

Gamma-ray astronomy and cosmic-ray physics with ARGO-YBJ

The ARGO-YBJ detector, located 4300 m a.s.l. on the Tibet plateau, is a ground-based, full- coverage array of Resistive Plate Chambers (RPCs) covering a surface of 78×74 m2, surrounded by a guard ring of RPCs enclosing a total surface of about 11000 m2. ARGO-YBJ was designed to detect extensive air showers generated by cosmic rays and gamma rays with primary energy greater than few hundred GeV, in order to study the region of the cosmic-ray spectrum out of the reach of both satellite-based experiments and traditional ground-based arrays. The experiment has been running with its complete layout since November 2007, collecting over 2:5×1011 events. The main results obtained by ARGO-YBJ will be presented here, and specifically: the monitoring of astronomical gamma-ray sources, such as the Crab nebula and the MRK 421 AGN, the moon shadow, the medium-scale anisotropy map, the proton-proton inelastic cross section at center-of- mass energy between 70 and 500 GeV where no accelerator data are available

Gamma-ray astronomy with ARGO-YBJ

ARGO-YBJ is a full coverage air shower array located at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm2) recording data with a duty cycle ≥85% and an energy threshold of a few hundred GeV. In this paper the latest results in Gamma-Ray Astronomy are summarized

ARGO-YBJ experiment and the Tev gamma astronomy

The ARGO-YBJ detector is an extensive air shower array consisting of a carpet of Resistive Plate Chamber (RPCs

Performance of the resistive plate chambers in the ARGO-YBJ experiment

The ARGO-YBJ experiment is designed for the detection of Extensive Air Showers (EAS) in the primary energy range 100 GeV–10 TeV. Its full-coverage feature allows to lower the energy threshold about one order of magnitude with respect to sampling EAS detectors. Here the performance of the RPC array is described and the current status of the experiment is presented

Analyse experimentale des mecanismes de coercivite dans les aimants Nd-Fe-B frittes

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc