Sampling strategy and climatic implications of tree-ring stable isotopes on the southeast Tibetan Plateau

We explore the potential of tree-ring cellulose δ¹⁸O and δ¹³C records for reconstructing climate variability in the southeast Tibetan Plateau. Our sampling strategy was designed to investigate intra and inter-tree variability, and the effects of the age of tree on δ¹⁸O variation. We show that intra-tree δ¹³C and δ¹⁸O variability is negligible, and inter-tree coherence is sufficient to build robust tree-ring δ¹⁸O or δ¹³C chronologies based on only four trees. There is no evidence of an age effect regarding δ¹⁸O, in contrast with tree-ring width. In our warm and moist sampling site, young tree δ¹³C is not clearly correlated with monthly mean meteorological data. Tree-ring δ¹⁸O appears significantly anti-correlated with summer precipitation amount, regional cloud cover, and relative humidity. Simulations conducted with the ORCHIDEE land surface model confirm the observed contribution of relative humidity to tree cellulose δ¹⁸O, and explain the weak correlation of δ¹³C with climate by the non-linear integration linked with photosynthesis. Altogether, the tree-ring cellulose δ¹⁸O is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period.     

Hydro-geomorphic hazards and impact of man-made structures during the catastrophic flood of June 2000 in the Upper Guil catchment (Queyras, Southern French Alps)

The Guil River Valley (Queyras, Southern French Alps) is prone to catastrophic floods, as the long historical archives and Holocene sedimentary records demonstrate. In June 2000, the upper part of this valley was affected by a “30-year” recurrence interval (R.I.) flood. Although of lower magnitude and somewhat different nature from that of 1957 (>100-year R.I. flood), the 2000 event induced serious damage to infrastructure and buildings on the valley floor. Use of methods including high-resolution aerial photography, multi-date mapping, hydraulic calculations and field observations made possible the characterisation of the geomorphic impacts on the Guil River and its tributaries. The total rainfall (260 mm in four days) and maximum hourly intensity (17.3 mm h⁻¹), aggravated by pre-existing saturated soils, explain the immediate response of the fluvial system and the subsequent destabilisation of slopes. Abundant water and sediment supply (landsliding, bank erosion), particularly from small catchment basins cut into slaty, schist bedrock, resulted in destructive pulses of debris flow and hyperconcentrated flows. The specific stream power of the Guil and its tributaries was greater than the critical stream power, thus explaining the abundant sediment transport. The Guil discharge was estimated as 180 m³ s⁻¹ at Aiguilles, compared to the annual mean discharge of 6 m³ s⁻¹ and a June mean discharge of 18 m³ s⁻¹. The impacts on the Guil valley floor (flooding, aggradation, generalised bank erosion and changes in the river pattern) were widespread and locally influenced by variations in the floodplain slope and/or channel geometry. The stream partially reoccupied former channels abandoned or modified in their geometry by various structures built during the last four decades, as exemplified by the Aiguilles case study, where the worst damage took place. A comparative study of the geomorphic consequences of both the 1957 and 2000 floods shows that, despite their poor maintenance, the flood control structures built after the 1957 event were relatively efficient, in contrast to unprotected places. The comparison also demonstrates the role of land-use changes (conversion from traditional agro-pastoral life to a ski/hiking-based economy, construction of various structures) in reducing the Guil channel capacity and, more generally, in increasing the vulnerability of the human installations. The efficiency of the measures taken after the 2000 flood (narrowing and digging out of the channel) is also assessed. Final evaluation suggests that, in such high mountainous environments, there is a need to keep most of the 1957 flooded zone clear of buildings and other structures (aside from the existing villages and structures of particular economic interest), in order to enable the river to migrate freely and to adjust to exceptional hydro-geomorphic conditions without causing major damage.     

The impact of logging on the surrounding flow in a managed forest

The influence of a freshly logged area in a managed pine forest on the flow field is investigated by comparing sodar wind profile data over the forest canopy with the synoptic wind field extracted from North American Regional Reanalysis, National Centers for Environmental Prediction. As a consequence of the pressure gradient arising from the sharp temperature difference between the clearcut and the surrounding uncut forests, the local wind direction over the forest measured with the sodar departs dramatically from the prevailing synoptic wind direction when the latter is transverse to the clearcut-sodar direction. Sodar measurements also indicate systematic strong updrafts during daytime followed by nighttime downdrafts with wind coming from the logged area. This suggests the presence of horizontal advection carrying daytime warm air (or nighttime cool air) from the clearcut to the forested area. This paper also examines the influence of wind velocity, clearcut fetch, and solar radiation on locally generated circulations and advection. The presence of local circulations arising from contrasting neighboring surface characteristics well outside the footprint is of particular relevance for atmospheric flux sites where robust surface?Catmosphere exchange values are sought. This study highlights the high level of circumspection required at the time of identifying locations for flux sites. It also suggests vigilant monitoring of the surrounding landscape during eddy?Cflux measurements particularly in actively managed landscapes.     

Trace element distributions in surficial sediments of the northern Tyrrhenian Sea: Contribution to heavy-metal pollution assessment

The trace element distributions in surficial sediment of Tyrrhenian Sea have been investigated as a part of a series of studies on the environmental quality of the area off the Tuscany coast (west-central Italy). This research has focused on the presence of possible contaminated zones; it also provides data for the identification and future monitoring and control of pollution sources. The study of numerous surface sediments and core samples has made it possible to distinguish between heavy-metal enrichments related to natural sources and other anomalies caused by anthropogenic contamination. Over much of the basin, the surface Pb, Cu, Zn, and As contents appear considerably enriched relative to those below 15 cm; among these metals, Pb shows the highest and most widespread enrichment. Only in the case of some coarse-grained sediments close to the mouth of Cecina River it is possible to relate anomalously high Zn contents to natural sources. In all other sampling stations, the enrichments of Pb, Cu, Zn, and As are ascribed to man's influence. The sediment distributions of Co, Cr, and Ni do not seem to be related to anthropogenic activities; rather they mirror influx of materials derived from sources of ophiolitic rock. The distribution of barium shows only two significant positive anomalies, and both are related to natural causes. Concentrations of vanadium are high in a zone close to an important smelting plant; these are thought to be of anthropogenic origin.     

盐湖丰产元素与Zintl化合物(续完)

Zintl化合物是以Edward Zintl命名的化合物,是一类由电正性的碱金属或碱土金属与电负性的13族或14族元素形成的特殊金属间化合物。其价键模式可以是离子键、金属键和共价键共存,其中的准金属可以共价键的形式形成各种形式的离子簇,因而其结构复杂多样。这类化合物的部分阴离子簇不仅具有稳定的笼状、层状和链状结构,并且具有特殊的光、电、磁等性能,使得在半导体、催化、电极材料等方面都有应用的前景和发展潜力。介绍了几个特殊Zintl化合物体系,盐湖丰产元素在Zintl化合物中的作用,指出了含有盐湖丰产元素的Zintl化合物的应用前景和方向。     

盐湖丰产元素与Zintl化合物(续一)

Zintl化合物是以Edward Zintl命名的化合物,是一类由电正性的碱金属或碱土金属与电负性的13族或14族元素形成的特殊金属间化合物。其价键模式可以是离子键、金属键和共价键共存,其中的准金属可以共价键的形式形成各种形式的离子簇,因而其结构复杂多样。这类化合物的部分阴离子簇不仅具有稳定的笼状、层状和链状结构,并且具有特殊的光、电、磁等性能,使得在半导体、催化、电极材料等方面都有应用的前景和发展潜力。介绍了几个特殊Zintl化合物体系,盐湖丰产元素在Zintl化合物中的作用,指出了含有盐湖丰产元素的Zintl化合物的应用前景和方向。     

Arsenic — a Review. Part II: Oxidation of Arsenic and its Removal in Water Treatment

In natural waters arsenic normally occurs in the oxidation states +III (arsenite) and +V (arsenate). The removal of As(III) is more difficult than the removal of As(V). Therefore, As(III) has to be oxidized to As(V) prior to its removal. The oxidation in the presence of air or pure oxygen is slow. The oxidation rate can be increased by ozone, chlorine, hypochlorite, chlorine dioxide, or H₂O₂. The oxidation of As(III) is also possible in the presence of manganese oxide coated sands or by advanced oxidation processes. Arsenic can be removed from waters by coprecipitation with Fe(OH)₃, MnO₂ or during water softening. Fixed‐bed filters have successfully been applied for the removal of arsenic.The effectiveness of arsenic removal was tested in the presence of adsorbents such as FeOOH, activated alumina, ferruginous manganese ore, granular activated carbon, or natural zeolites. Other removal technologies are anion exchange, electrocoagulation, and membrane filtration by ultrafiltration, nanofiltration or reverse osmosis.     

Toxicity of a secondary-treated sewage effluent to marine biota in Bass Strait, Australia: development of action trigger values for a toxicity monitoring program

Melbourne Water's Eastern Treatment Plant (ETP) produces a secondary-treated sewage effluent which is chlorinated and discharged into Bass Strait at Boags Rocks, Victoria, Australia. Disappearance of the sensitive brown seaweed Hormosira banksii from rock platforms immediately adjacent to the shore-line discharge was identified in the early 1990s. Subsequently, Melbourne Water and CSIRO undertook an environmental impact assessment and review of land and marine effluent disposal options, which included ambient water quality monitoring, biological monitoring, bioaccumulation studies and toxicity testing of existing effluent to assess the nature and magnitude of the environmental effects. This paper presents data from the toxicity monitoring programs since 2001. Chronic toxicity testing using macroalgal germination and cell division (H. banksii), microalgal growth rate (Nitzschia closterium) and scallop larval development (Chlamys asperrima), confirmed that ammonia was the major cause of effluent toxicity. Results from this toxicity monitoring program were used to develop action trigger values for toxicity for each species, which were then used in a refined monitoring program in 2005-2007. An upgrade of the ETP is in progress to improve nitrification/denitrification in order to reduce ammonia concentrations and the toxicity of the effluent. Toxicity testing with a simulated upgraded effluent confirmed that ammonia concentrations and toxicity were reduced. Estimated "safe" dilutions of effluent, calculated using species sensitivity distributions, decreased from 1:140-300 for existing ETP effluent to 1:20 for nitrified effluent, further confirming that treatment improvements should reduce the impact on marine biota in the vicinity of the discharge.     

Speciation of Arsenic Using Chelation Solvent Extraction and High Performance Liquid Chromatography

Research interest in speciation of arsenic stems from its species dependent behavior in the environment and in living organisms. The complexity of the matrix to be analyzed and low concentrations of target arsenic species that may be labile or difficult to chromatogram, indicate that a suitable pre‐treatment methodology is required. This study investigated the usefulness of chelation solvent extraction – high performance liquid chromatography (CSE‐HPLC) for the speciation of arsenic in water. It involved reacting arsenic with the chelant known for its affinity towards arsenic, followed by extraction, separation, and identification of the arsenic‐chelant‐arsenic complex. Arsenic species having different physicochemical properties were investigated. Species, such as, As₂O₃, As₃O₅, KH₂AsO₄, Na₂HAsO₄, and NaAsO₂ were detected as a group of closely eluted peaks with different retention times and spectral properties, whereas, the organic arsenic species CH₃Na₂AsO₃, o‐arsanilic acid, roxarson and triphenyl arsine separated quite well on the EnviroseP‐CM HPLC column. Key method parameters, such as, type of HPLC column, composition of mobile phase and organic solvents affecting peak resolution and sensitivity were optimized. Real environmental matrices contaminated with arsenic were analyzed under varying wavelengths (λ_max = 190, 210, 220, 234, 244, and 282 nm), with good precision. Different arsenic species were detected in these samples with excellent background and signal‐to‐noise ratios demonstrating the robustness of the method. The detection limit, reproducibility, selectivity, accuracy, and dynamic range of the calibration curves were evaluated.     

Robotic telescopes and networks: New tools for education and science

Nowadays many telescopes around the world are automated and some networks of robotic telescopes are active or planned. Such equipment could be used for thetraining of students and for science in the Universities of DCs and of newastronomical countries, by sending them observational data via Internetor through remotely controlled telescope. It seems that it is thetime to open up for discussion with UN and ESA organizations and also withIAU, how to implement links between robotic telescopes and suchUniversities applying for collaborations. Many scientific fields couldthus be accessible to them, for example on stellar variability, near-earthobject follow-up, -ray burst counterpart tracking, and so on.