Impacts of saline water irrigation and shrimp pond discharges on the surrounding waters of a coastal district in the Mekong delta of Vietnam

This study discusses impacts of saline water irrigation and shrimp pond discharges on the surrounding waters in the coastal Cai Nuoc district, Mekong delta of Vietnam where the landscape was re-shaped by shrimp aquaculture since 2000. Sampling took place at the end of the wet season of 2009 in the district (as aquaculture sites) and a nearby freshwater-dominated reference site. The aquaculture sites showed significantly higher salinities and organic loadings (biochemical oxygen demand, chemical oxygen demand) but lower dissolved nutrients (NO₃–N, NO₂–N, and PO₄–P), total iron, and phytoplankton diversity compared to the reference site. Irrigation of saline waters has exacerbated salinization, leading to significant biological changes in the surrounding waters. Impacts of shrimp pond discharges on the surrounding waters were not very dramatic in terms of organic loadings and nutrients. The increase in organic loadings in the surrounding waters was mostly due to contribution from other pollution sources, such as domestic/industrial discharges and runoff. Enhanced salinization and changes in nutrients resulted in a decline in species richness and diversity, and a change in the evenness of the phytoplankton community. Besides, the composition of zooplankton and zoobenthos were also restructured. The mild impacts of shrimp pond discharges on the surrounding waters were primarily due to the limited inputs for shrimp aquaculture in this area.     

Self-Interacting Dark Matter in the SU(3)C⊗ SU(3)L ⊗ U(1)N models

We present the gauge models based on SU(3)_C⊗ SU(3)_L ⊗ U(1)_N (3-3-1) group which contain particles satisfying conditions for dark matter. There are two such models: one with exotic positive charged lepton and a variant with right-handed neutrinos. The scalar self-interacting dark matters are stable without imposing of new symmetry and should be weak-interacting. PACS Nos: 95.35.+d, 12.60.Fr, 14.80.Cp     

Influence of synoptic processes on the vietnamese current (the South China Sea) Dynamics during the Winter–Summer 1999 transition period

Demonstrated is an influence of synoptic processes on the seasonal dynamics of the Vietnamese Current in the South China Sea varying its direction under the influence of the monsoon. The spring season of 1999 is used as an example of the transition from the winter to summer. In winter, under the influence of the northeastern monsoon, the current is directed from north to south and in the summer, at the southwestern monsoon, in the opposite direction. In the spring, two zones of different water modification are formed: an impact is observed of both the leaving winter monsoon and the coming summer monsoon. Considered is an atmospheric process of low-gradient field type, when the pressure field is characterized by the low pressure gradient over the whole South China Sea. It is revealed that the Vietnamese Current moves in the summer regime (from south to north) in the northern and southern parts and keeps the winter regime (from north to south) in the central part.     

Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam

Effects of elevated seawater temperature show high spatial heterogeneity and variation within and among coral species. The objective of this study was to investigate how two coral species, Porites lutea and Galaxea fascicularis, from two high latitude reefs differently exposed to chronic disturbance, respond to elevated seawater temperatures. Corals were collected from reefs nearshore (i.e. subjected to high sediment load, higher chlorophyll α concentrations, turbidity etc.) and offshore (i.e. less exposed). The corals were exposed in the lab to gradually increasing temperatures (25.5-33.5?°C) for 72?h after which they were allowed to recover to ambient temperature (25.5?°C) for 24?h. Production and respiration were measured after 24, 48, 72 and 96?h. The results show that P. lutea from nearshore reefs suffered an initial decrease in gross primary production/respiration (GP/R) ratio after 24?h, after only a moderate temperature increase (+2?°C, from 25.5 to 27.5?°C), while there was no difference in GP/R ratio between heat-exposed and controls the other days, indicating that the chronic disturbance in the nearshore reef had no effect on their thermotolerance. Furthermore, P. lutea from the offshore reef showed a decrease in GP/R ratio both after 24?h and 72?h (33.5?°C) of exposure. In comparison, G. fascicularis showed a decrease in GP/R ratio after 48?h, 72?h and 96?h of exposure for the nearshore corals. Also, after 72?h these corals had withdrawn their polyps. There were no differences between heat-treated and controls for the offshore G. fascicularis. This implies that the chronically disturbed G. fascicularis had lower thermotolerance when exposed to a temperature increase. This study, hence, shows that the response of corals to elevated seawater temperature varies with species and environmental background history.     

Development Optimization Using Reservoir Response Surfaces: Methods for Integrating Facility and Operational Options

The objective of a field development optimization process, or workflow, is to investigate various options and determine a course of action that will deliver the largest expected value from an asset. The analysis is often complicated by uncertainty in important inputs. Ideally, operators desire workflows and tools that integrate reservoir engineering and optimization principles in a fast-solving model that can be used to explore the full range of the uncertain inputs. This need is acute in the screening and concept selection stage where the primary objective is to determine the sensitivity of competing concepts to the sources of uncertainty. In these early stages, model results can be used to determine whether additional information should be collected, and to narrow down the number of competing options. The objective of this research is the development of a workflow and tool that integrates reservoir response surfaces within a project optimization model that contains facility and operational options, and to use this model to investigate the impacts of uncertainty on decision making. The integration of technical options is critical because a static view of capital investment and facility constraints causes a systematic undervaluation and can introduce error to development decisions. The new workflow and integrated reservoir-economic optimization tool developed in this research leverage methods and engineering work products that are already known to industry, for example, experimental design (ED) and response surface methods (RSMs). A demonstration is provided for a gas flood project using a stylized reservoir. Specifically, we investigate the selection of initial well configurations and injection capacities while simultaneously accounting for the options to update these decisions after production information is acquired in the early periods of production. The workflow is used to optimize the development of a gas flood. As a second step, the workflow is used to solve a value of information problem.     

Sea Level Rise Affecting the Vietnamese Mekong Delta: Water Elevation in the Flood Season and Implications for Rice Production

In this study, we assessed the impact of sea level rise, one of the most ascertained consequences of global climate change, for water levels in the Vietnamese Mekong Delta (VMD). We used a hydraulic model to compute water levels from August to November - when flooding is presently critical- under sea level rise scenarios of 20 cm (=Δ 20) and 45 cm (=Δ 45), respectively. The outputs show that the contour lines of water levels will be shifted up to 25 km (Δ 20) and 50 km (Δ 45) towards the sea due to higher sea levels. At the onset of the flood season (August), the average increment in water levels in the Delta is 14.1 cm (Δ 20) and 32.2 cm (Δ 45), respectively. At the peak of the flood season (October), high discharge from upstream attenuates the increment in water level, but average water level rise of 11.9 cm (Δ 20) and 27.4 cm (Δ 45), respectively, still imply a substantial aggravation of flooding problems in the VMD. GIS techniques were used to delineate areas with different levels of vulnerability, i.e., area with high (2.3 mio ha =60% of the VMD), medium (0.6 mio ha = 15%) and low (1 mio ha =25%) vulnerability due to sea level rise. Rice production will be affected through excessive flooding in the tidally inundated areas and longer flooding periods in the central part of the VMD. These adverse impacts could affect all three cropping seasons, Mua (main rainfed crop), Dong Xuan (Winter-Spring) and He Thu (Summer-Autumn) in the VMD unless preventive measures are taken.     

A general purpose autonomous transmitter and receiver system forunderwater acoustic experiments

A versatile multifrequency, multi-purpose acoustic transmitter and receiver system has been developed and used to measure low frequency acoustic backscatter from the ocean surface. The instrumentation is general purpose in that all signal and sample parameters are selected by software and a variety of transmission, scattering and reverberation experiments are possible without hardware modification. The system is battery-powered and self-contained for remote and unattended operation for periods of months, depending upon the experimental parameters that affect power and tape consumption. The main features of the system are: a high-powered broadband set of acoustic sources-with center frequencies of 100, 200, 400, and 800 Hz, programmable output signal types, a 64-element vertical hydrophone array, fifty gigabytes of data storage capacity, dynamically-tuneable band pass filters and variable sampling rates, high power microprocessors for in situ signal processing and independent subsystems for recording mooring depth and inclination. The system has been used in surface backscattering experiments at sea and results that demonstrate the capability of the system are presented and discussed     

Multi-scale variability of circulation in the Gulf of Tonkin from remote sensing of surface currents by high-frequency radars

Ocean Dynamics - The sea surface velocity measurements obtained during the period of 2014–2016 using two high-frequency radars (HFR), which were installed on the northern coast of Vietnam,...     

Predicting soil erosion hazard in Lattakia Governorate(W Syria)

The main objective of this study is to predict soil erosion in the Lattakia Governorate(WSyria)using the Water Erosion Prediction Project model(WEPP)and to compare the result with that of the RUSLE.Field survey and data collection were carried out,and 44 soil samples were analyzed.In addition,all the necessary input files were prepared for use in the WEPP model and RUSLE.Results show that more than of 80%of the locations studied experience slight to moderate erosion(less than 5 t/ha/y),whereas the rest of the locations experience severe soil erosion hazard.Moreover,the volume of runoff estimated by the WEPP model is in the range of 51e321 mm,and the R^2 between the simulated soil erosion and the predicted runoff reached 0.68.Interestingly,the R^2 between the WEPP model and RUSLE is 0.56,which indicates a good correlation between the two models.