Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.     

The use of image processors for acquisition and reduction of astrometric data in real time

In Dynamical Astronomy, the data used to fit theories are positional observations. If the data are reduced using computers, the measure itself is not, and informations are lost. The classical way is to use photographic plates measured by hand. The use of automatic machine permits to save time but not to increase the amount of data.The arrival of silicium targets and CCD allows to acquire much more data directly stored on computer. We used this technique associated with array processors. So we succeeded to increase the accuracy of the data. This method was applied to the observation of the motion of some asteroids and of the Galilean satellites of Jupiter.     

The composition of Ceres: A determination by high-pressure physics

In this letter we report on a calculation of the chemical composition of the asteriod (1) Ceres, performed by using a particular theory of behaviour of materials under high pressure. Chemical similarities between Ceres, Mars and Mercury are noted and possible explanations suggested. As a by-product, the mass of (10) Hygiea is calculated.     

The ethylxanthate adsorption on copper-activated sphalerite under flotation-related conditions in alkaline media

Floatability and surface characteristics of sphalerite in the presence of different concentrations of copper sulphate and K-ethylxanthate, for various times of activation and collection, were studied. The resulting changes on the sphalerite surface were determined by infrated attenuated total reflection spectroscopy and correlated with electrokinetic measurement and floatability test results.The collectorless flotation of the examined sphalerite was very weak in alkaline media, independent of whether the mineral was activated with copper or without copper treatment. However, copper showed an activating effect on KEX sphalerite flotation in the alkaline region. Copper ions of high concentration provoked an “apparently depressing effect” on KEX sphalerite flotation, reacting with EX⁻ to form copper-ethylxanthate-like species in the bulk of the solution. After decantation of the solution, before KEX was added, the depressing effect disappeared and sphalerite flotation was virtually complete.Cu(I)-ethylxanthate was the main surface product under the different experimental conditions. The kinetics of the copper-ion adsorption and KEX adsorption was relatively fast.     

Assessment of CMIP5 historical simulations of rainfall over Southeast Asia

Theoretical and Applied Climatology - We present preliminary analyses of the historical (1986–2005) climate simulations of a ten-member subset of the Coupled Model Inter-comparison Project...     

Regional climate simulations over Vietnam using the WRF model

Time-irreversible symmetry is a fundamental property of nonlinear time series. Time-irreversible behaviors of mean temperature measured on 182 stations over China from 1960 to 2012 are analyzed by directed horizontal visibility graph (DHVG for short), and significance of results has been estimated by Monte Carlo simulations. It is found that dominated time irreversibility emerges in nearly all daily temperature anomaly variations over China. Further studies indicate that these time-irreversible behaviors result from asymmetric distributions of persistent daily temperature increments and decrements, and this kind of symmetry can be quantified by distributions of consecutive daily mean temperature increasing or decreasing steps. At the same time, the findings above have been confirmed by artificially generated time series with given value of multiscale asymmetry.     

A note on the melting of iron under high pressure

Using new experimental data on the pressure dependence of the melting temperature of iron, the value of the high temperature limit of the Grüneisen parameter,, has been derived. The calculation has been performed within the theory of melting of metals recently proposed by Schlosseret al., (1989,Phys. Rev.,B40, 5929), with and without modifications due to taking into account the pressure dependence of the ratio/V. The results of both calculations are in agreement with values quoted in recent literature. Possible causes of the discrepancies are discussed. A change of occuring atP 120–130 GPa indicates the occurence of a phase transition, whose existence is confirmed within a particular semiclassical theory of dense matter.     

Ecological risk assessment of heavy metals sampled in sediments and water of the Houjing River,Taiwan

The Houjing River flows through Kaohsiung, the most industrialized city in southern Taiwan. In this study, heavy metal concentrations in water and sediments from samples along the river were investigated to illustrate metal contamination levels and call for the awareness of industrial pollution prevention. The heavy metal concentrations in the water samples were low and appear to pose little direct risk to aquatic life and irrigation, but heavy metal concentrations in the sediments are locally very high and present an environmental risk. Cadmium, Cu, and Zn were found in higher concentrations in the river sediments than those recommended in some sediment quality guidelines and findings of river sediments in similar studies worldwide. Hence, the ecological risk of heavy metal contamination in sediments was assessed using the pollution load index (PLI) and potential ecological risk index (RI). Three of the eleven sites sampled were found to have PLI values higher than 1 and 8 of them had ‘considerable’ to ‘very high’ RI values, suggesting a considerable ecological risk. These findings provide an insight into elemental metal contamination of the Houjing River and present a baseline data set, which will be critical for future development and environmental protection plans devised for the region.     

Correlation of CYP1A1 induction, as measured by the P450 RGS biomarker assay, with high molecular weight PAHs in mussels deployed at various sites in San Diego Bay in 1993 and 1995

In 1993 collections of marine mussels (Mytilus galloprovincialis) were deployed 1 m from the water surface at six sites in San Diego Bay for 88 days. A similar mussel deployment was conducted in 1995, except the animals were deployed 1 m off the bottom and only for 32 days. After recovery from the sites, tissue was extracted with dichloromethane and the solvent extracts analyzed for chemical contaminant content and the ability to produce CYP1A1 induction in a transgenic cell line (TV101L cells). The cells used in the assay (P450 RGS) are stably transfected with a plasmid containing firefly luciferase linked to human CYP1A1 promoter sequences. Induction (fold increase compared to control) was determined by luminometry 16 h after application of small volumes (2–10 μl) of solvent extracts to cultured cells. Small mussels deployed in the Naval Station (NAV) in 1993 exhibited very high bioaccumulation of polycyclic aromatic hydrocarbons (PAHs; 52 μg/g) and polychlorinated biphenyls (PCBs), in addition to very strong induction of CYP1A1 measured by reporter gene system (RGS) responses. Large mussels deployed at the NAV station in 1993 and intermediate-sized animals placed at three stations within the NAV station in 1995 accumulated 13–29 μg PAH/g and exhibited relatively high RGS responses. Correlation of RGS responses for all mussel samples to the measured PAH concentrations was 0.85 (r²). When the concentrations of seven specific PAHs found in the samples are converted to benzo[a]pyrene equivalents, from previously derived toxic equivalency factors (TEFs) for this test system, and compared to measured RGS responses, the correlations are approximately 0.9. The results of these studies indicate that the RGS biomarker can be used as a screening tool for detection of CYP1A1-inducing compounds in tissues, and an estimate of potential human health or ecological risk from ingestion of contaminated organisms. Positive RGS responses can be followed by detailed chemical analyses of PAHs and coplanar PCBs using the same extract.