Speciation and Mobility of Selected Trace Metals (As, Cu, Mn, Pb and Zn) in Sediment with Depth in Cam River-Mouth, Haiphong, Vietnam

The speciation and mobility of some selected trace metals (As, Cu, Mn, Pb and Zn) in sediments with depth was investigated in the Cam River-mouth (Vietnam) by collecting sediment cores and analysing porewater and sediment composition, complemented with single (ammonium-EDTA) and sequential (BCR 3-step) extractions and mineralogical analysis (XRD). All trace metals show overall decreasing trends with depth in porewater as a result of anthropogenic input in upper sediment layers. High porewater concentrations of As, Mn and Pb in oxic and suboxic sediment layers may result in groundwater pollution. Sediment-bound Pb and Mn dominate in the reducible and the acid-soluble fraction, respectively, while Cu and Zn distribute rather evenly between four extracted fractions. The porewater metal speciation, as predicted by a geochemical model Visual MINTEQ version 3.0, indicates that the toxicity of Cu, Mn, Pb and Zn (presented by the proportions of free metal ions) decreases with depth, while the toxicity of As increases when As(III) becomes more abundant. The dissolved concentrations of trace metals are not only controlled by the precipitation/dissolution of discrete hydroxide/oxide, carbonate and phosphate minerals, but also by sorption processes on major sorbents (i.e. As on goethite, and Mn and Zn on calcite and dolomite). Sulphide minerals do not show any control even in the anoxic zone most likely because of the low concentration of sulphur.     

Geoheritage values in the Cat Ba islands, Vietnam

Geological wonders have been generally known as natural wonderful products. Resulted from geological processes, geological wonders are diverse in size that have geoheritage values that should be protected from damaging of substance, form and natural development. In a large scale, geological wonders can be geoheritage areas, containing several geodiversity elements that are geologically important or in a smaller scale, they can be geosites of heritage values (or geoheritage sites). In the delimitation of areas, having geoheritage values and the establishment of geoparks, the first thing is to recognise them as geosites and geoheritage areas that indicate great geological values. Besides the Ha Long bay, the world natural heritage with its outstanding aesthetic and geological values, the Cat Ba islands are typical and grandeur karst landscapes formed in tropical condition. Based on the geodiversity elements with their own geoheritage values on aesthetics, uniqueness and grandeur in the Cat Ba islands, the authors have recognised three geoheritage areas: the south cape of the Cat Ba embayment, Tung Gau (shelter), and the Lan Ha bay. Sites where Brachiopods, Crinoids and Tetracorals are exposed on the way through the island are considered as palaeontological geosites. The folds of limestone layers in the northern part of Cat Co 3 beach, with typical turbidite structures in carbonate formations are considered as a lithological geosite. The Devonian-Carboniferous boundary near the Cat Co 3 beach is regarded as a stratigraphical geosite while Que Kem and Turtle islands, etc. are considered as geomorphological geosites.     

Terrestrial water dynamics in the lower Ganges—estimates from ENVISAT and GRACE

In this study, the hydrodynamics of lower Ganges basin in India has been monitored using radar altimetry data from environmental satellite (ENVISAT) mission and microgravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. River stage time series have been constructed for different virtual stations on the lower Ganges. Time series for the integrated water volume changes from microgravity measurements have also been constructed to characterize the seasonal and interannual fluctuation patterns in water storage and flux. The ENVISAT dataset indicates an average seasonal river stage fluctuation of 8 m in the lower Ganges River. The GRACE dataset reveals a seasonal fluctuation ranging from 0.18 to 0.40 m in the vertically integrated total water storage in the lower Ganges basin. The two independent datasets show broad similarity in the lower Ganges basin and outline the importance of space-based techniques for monitoring continental water resources.     

Recent contamination by persistent organochlorines in Baikal seal (Phoca sibirica) from Lake Baikal, Russia

Blubber samples of Baikal seals pups (Phoca sibirica) collected in 2001 and 2002 were analyzed for persistent organochlorines (OCs) such as PCBs (polychlorinated biphenyls), DDTs (dichlorodiphenyltrichloroethane and its metabolites), HCHs (hexachlorocyclohexane isomers), CHLs (chlordane related compounds), TCPMe [tris(4-chlorophenyl)methane] and TCPMOH [tris(4-chlorophenyl)methanol]. The distribution pattern of OCs was in the following order: DDTs>PCBs>CHLs>HCHs>TCPMOH>TCPMe. Organochlorine concentrations and composition patterns in eight pup blubber samples (2002) analyzed in the present study were compared with the corresponding levels in juvenile Baikal seals from 1992 survey, and it was found that residue levels of OC compounds have declined during the 10 year period. In particular, concentrations of PCBs, HCHs and CHLs in seals collected in 2002 were approximately two times lower, while DDTs levels were three times lower than the corresponding levels in 1992. Furthermore, higher ratios of beta-HCH/HCHs and p,p(')-DDE/DDTs were found in 2002 samples. While comparing the OC levels with those in other seal pups it appeared that all the OC concentrations were lower than the levels in seals from coastal California known as one of the most polluted areas. PCB and DDT concentrations in the present specimens were higher than that in Arctic seal pups. The proportions of tri-, tetra-, penta- and hexachlorobiphenyls in pups captured in 2002 were higher than those in 1992. TEQ concentrations of non- and mono-ortho coplanar PCBs in Baikal seals collected in 2002 were higher than those in seals collected from some locations in the world, where human and industrial activities are extensive, suggesting potential for toxic implications of coplanar PCBs in Baikal seals.     

Understanding spatial variations of malaria in Vietnam using remotely sensed data integrated into GIS and machine learning classifiers

Abstract

This study examines the potentials of remotely sensed data, GIS and some machine learning classifiers and ensemble techniques in the investigation of the non-linear relationship between malaria occurrences and socio-physical conditions in the Dak Nong province of Viet Nam. Accuracy assessment was determined with Receiver Operating Characteristic (ROC) curve and pair t-test. The results showed that the area under ROC of Random Subspace ensemble model performed better than the other models based on statistical indicators. Comparing pair t-test with Area Under Curve values showed a slight difference of about 1%. Therefore ensemble techniques had significantly improved the performance of the base classifier. However, the performances might vary according to geographic locations. It is concluded that the machine learning classifiers combined with remotely sensed data and GIS is promising for malaria vulnerability mapping, and the derived maps can be used as a fundamental basis for programmes on spatial disease control.     

Shrinkage Properties of Soft Clay Treated with Cement and Geofibers

In this study, effects of two types of geofibers, namely polypropylene and recycled carpet, on three dimensional shrinkage properties of cement treated kaolinite and bentonite clays are investigated. Cement treated clay specimens were prepared with cement contents of 5, 10, and 15 % by weight of dry soil for kaolinite samples, and 30, 40 and 50 % for bentonite samples. To investigate and understand the influence of different fiber types and contents, three different percentages of fiber content (i.e. 0.1, 0.2 and 0.5 % polypropylene fibers; and 0.5, 0.75 and 1 % carpet fibers) were adopted. The results of shrinkage tests on 126 cylindrical samples of cement treated clay with various cement and fiber contents were analysed to understand the relationships between these parameters and the shrinkage percentage of treated soil. Results of this study indicate that combination of cement and fiber is effective in reducing the volume change of clayey soils undergoing drying process. In the applied ranges of cement and fiber contents, the influence of cement addition on the shrinkage reduction is more significant than the addition of fibers for the treated kaolinite. However, addition of fibers in curtailing the shrinkage of bentonite clay is more significant than the cement addition.     

Modern climate of the Cát Tiên National Park (Southern Vietnam): Climatological data for ecological studies

A method of using the standard network weather station data for local ecosystem research is considered on the example of the modern climate of the Cát Tiên National Park (Southern Vietnam) and local climate change in 1980–2010. Special attention is focused on the environmental parameters, which play a role of the limiting factors. It is shown that the climate of Southern Vietnam responds with statistical significance to global climate change. Suggestions about the possible reactions of tropical monsoon forest ecosystem to climate change are given.     

An Application of the Multi-Physics Ensemble Kalman Filter to Typhoon Forecast

This study examines the roles of the multi-physics approach in accounting for model errors for typhoon forecasts with the local ensemble transform Kalman filter (LETKF). Experiments with forecasts of Typhoon Conson (2010) using the weather research and forecasting (WRF) model show that use of the WRF’s multiple physical parameterization schemes to represent the model uncertainties can help the LETKF provide better forecasts of Typhoon Conson in terms of the forecast errors, the ensemble spread, the root mean square errors, the cross-correlation between mass and wind field as well as the coherent structure of the ensemble spread along the storm center. Sensitivity experiments with the WRF model show that the optimum number of the multi-physics ensemble is roughly equal to the number of combinations of different physics schemes assigned in the multi-physics ensemble. Additional idealized experiments with the Lorenz 40-variable model to isolate the dual roles of the multi-physics ensemble in correcting model errors and expanding the local ensemble space show that the multi-physics approach appears to be more essential in augmenting the local rank representation of the LETKF algorithm rather than directly accounting for model errors during the early cycles. The results in this study suggest that the multi-physics approach is a good option for short-range forecast applications with full physics models in which the spinup of the ensemble Kalman filter may take too long for the ensemble spread to capture efficiently model errors and cross-correlations among model variables.