Seasonal Dynamics of Phytoplankton and Environmental Factors around the Chagwi-do off the West Coast of Jeju Island,Korea

The dynamics of phytoplankton abundance with seasonal variation in physicochemical conditions were investigated monthly at 10 stations around the Chagwi-do off the west coast of Jeju Island, Korea, including inshore, middle shore, and offshore in the marine ranching area from September 2004 to November 2005. Water temperature varied from 12.1 to 28.9°C (average 18.8°C), and salinity from 28.9 to 34.9 psu (average 33.7 psu). The chlorophyll a concentration was 0.02-2.05 μg L¹ (average 0.70 μg L¹), and the maximum concentration occurred in the bottom layer in April. A total of 294 phytoplankton species belonging to 10 families was identified: 182 Bacillariophyceae, 52 Dinophyceae, 9 Chlorophyceae, 12 Cryptophyceae, 6 Chrysophyceae, 4 Dictyophyceae, 13 Euglenophyceae, 6 Prymnesiophyceae, 5 Prasinophyceae, and 5 Raphidophyceae. The standing crop was 2.21-48.69x10⁴ cells L¹ (average 9.23x 10⁴ cells L¹), and the maximum occurred in the bottom layer in April. Diatoms were most abundant throughout the year, followed by dinoflagellates and phytoflagellates. A phytoplankton bloom occurred twice: once in spring, peaking in April, and once in autumn, peaking in November. The spring bloom was represented by fourChaetoceros species andSkeletonema costatum; each contributed 10–20% of the total phytoplankton abundance. The autumn bloom comprised dinoflagellates, diatoms, and phytoflagellates, of which dinoflagellates were predominant.Gymnodinium conicum, Prorocentrum micans, andP. triestinum each contributed over 10% of the total phytoplankton abundance.     

Multivariate statistical analysis and environmental isotopes of Amman/Wadi Sir (B2/A7) groundwater,Yarmouk River Basin,Jordan

Multivariate statistical techniques, cluster and factor analyses were applied on the Amman/Wadi Sir groundwater chemistry, Yarmouk River basin, north Jordan. The main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution. The k‐means cluster analysis yields three groups with distinct ionic concentrations. Cluster 1 comprises the vast majority of the sampled wells, and the water that belongs to this cluster can be classified as freshwater. Cluster 2 comprises only 2% of the sampled wells; it has the highest ionic concentration. The water of this cluster can be classified as brackish water. Cluster 3 involves 23% of the sampled wells, and it has total ionic concentration intermediate to that of clusters 1 and 2. Factor analysis yields a three‐factor model, which explains 76.77% of the groundwater quality variation. Factor 1 ‘salinity factor’ involves EC, Na⁺, Cl^‐, SO₄^‐2, K⁺ and Mg⁺² and reflects groundwater salinization because of overpumping. Factor 2 ‘hardness factor’ includes Ca⁺², HCO₃^‐ and the pH value and signifies soil–water/rock interaction. Factor 3 ‘nitrate factor’ involves only NO₃^‐ and points to groundwater contamination because of human activities, mainly untreated wastewater, and crops and animal cultivation in the unconfined portion of the aquifer. Factors 1 and 3 can be described as human‐induced factors, whereas factor 2 can be described as geogenic factor. Factors' scores were mapped to deduce the controlling processes on the groundwater chemistry. Stable isotope composition of ¹⁸O and ²H has revealed that the groundwater is a mixture of two water types. The radioactive isotopes tritium and ¹⁴ C were used to evaluate present day recharge to the aquifer and to estimate the groundwater age, respectively. Present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessing factors affecting drought,earthquake, and flood risk perception: empirical evidence from Bangladesh

Natural Hazards - Understanding household disaster risk perception is crucial to formulate and apply disaster risk reduction strategies. Using survey data from 300 households from three highly...     

A stable meshfree method for fully coupled flow-deformation analysis of saturated porous media

A fully coupled meshfree algorithm is proposed for numerical analysis of Biot’s formulation. Spatial discretization of the governing equations is presented using the Radial Point Interpolation Method (RPIM). Temporal discretization is achieved based on a novel three-point approximation technique with a variable time step, which has second order accuracy and avoids spurious ripple effects observed in the conventional two-point Crank Nicolson technique. Application of the model is demonstrated using several numerical examples with analytical or semi-analytical solutions. It is shown that the model proposed is effective in simulating the coupled flow deformation behaviour in fluid saturated porous media with good accuracy and stability irrespective of the magnitude of the time step adopted.     

Geochemical assessment of groundwater contamination with special emphasis on fluoride concentration, North Jordan

The concentrations of fluorine in groundwater of North Jordan range from 0.009 to 0.055 mg/l. Other chemical parameters, e.g. pH, EC, TDS, Cl, TH, HCO₃, PO₄, SO₄, NO₃, NH₄, K, Ca, Mg, and NO₃ have been studied and showed higher concentrations in HCO₃⁻ and NO₃⁻ of 307 and 51 mg/l, respectively. Thermodynamic considerations show that almost all the analyzed samples are undersaturated with respect to calcite and fluorite. This undersaturation is probably due to their low availability in the locations. Fluoride concentration shows a positive relation to pH and HCO₃, whereas Cl, Mg, Ca, and Na initially increase and then decrease with increasing fluoride in the water. Saturation indexes of fluorite and calcite are estimated. The chemistry of the groundwater is controlled by the fluorite and calcite solubility. The topography of the area has exerted control on the aerial extent of fluoride concentration.     

TOXICITY OF TWO HERBICIDES 2,4 -D DIMETHYLAMINE AND BENSULFURON METHYL TO RICE FIELD CHIRONOMUS KIIENSIS (TOKUNAGA) ( DIPTERA: CHIRONOMIDAE)

1 INTRODUCTIONRice field is a unique man -made wetland envi-ronment where many varieties of aquatic insects oc-curred ( Ali, Ahmad, 1988; Yamazaki,et al,2001a; Che Salmah, Abu Hassan, 2002). Duringrice cultivation in Malaysia, herbicides are used in-tensi…     

Estimation of frequency dependent coda wave attenuation structure at the vicinity of Cairo Metropolitan Area

Estimation of seismic wave attenuation in the shallow crust in terms of coda wave Q structure previously investigated in the vicinity of Cairo Metropolitan Area was improved using seismograms of local earthquakes recorded by the Egyptian National Seismic Network. The seismic wave attenuation was measured from the time decay of coda wave amplitudes on narrow bandpass filtered seismograms based on the single scattering theory. The frequency bands of interest are from 1.5 to 18 Hz. In general, the values obtained for various events recorded at El-Fayoum and Wadi Hagul stations are very similar for all frequency bands. A regional attenuation law Q _c = 85.66 f ^0.79 was obtained.