Geospatial and geostatistical approach for groundwater potential zone delineation

Over the past few decades, groundwater has become an essential commodity owing to increased demand as a result of growing population, industrialization, urbanization and so on. The water supply situation is expected to become more severe in the future because of continued unsustainable water use and projected change in hydrometeorological parameters due to climate change. This study is based on the integrated approach of remote sensing, geographical information system and multicriteria decision‐making techniques to determine the most important contributing factors that affect the groundwater resources and to delineate the groundwater potential zones. Ten thematic layers, namely, geomorphology, geology, soil, topographic elevation (digital elevation model), land use/land cover, drainage density, lineament density, proximity of surface water bodies, surface temperature and post‐monsoon groundwater depth, were considered for the present study. These thematic layers were selected for groundwater prospecting based on the literature; discussion with the experts of the Central Ground Water Board, Government of India; field observations; geophysical investigation; and multivariate techniques. The thematic layers and their features were assigned suitable weights on Saaty's scale according to their relative significance for groundwater occurrence. The assigned weights of the layers and their features were normalized by using the analytic hierarchy process and eigenvector method. Finally, the selected thematic maps were integrated using a weighted linear combination method to create the final groundwater potential zone map. The final output map shows different zones of groundwater potential, namely, very good (16%), good (35%), moderate (28%) low (17%) and very low (2.1%). The groundwater potential zone map was finally validated using the discharge and groundwater depth data from 28 and 98 pumping wells, respectively, which showed good correlation. Copyright © 2014 John Wiley & Sons, Ltd.     

An automated 3D modeling of topological indoor navigation network

Indoor navigation is important for various applications such as disaster management, building modeling, safety analysis etc. In the last decade, indoor environment has been a focus of wide research that includes development of indoor data acquisition techniques, 3D data modeling and indoor navigation. In this research, an automated method for 3D modeling of indoor navigation network has been presented. 3D indoor navigation modeling requires a valid 3D model that can be represented as a cell complex: a model without any gap or intersection such that two cells (e.g. room, corridor) perfectly touch each other. This research investigates an automated method for 3D modeling of indoor navigation network using a geometrical model of indoor building environment. In order to reduce time and cost of surveying process, Trimble LaserAce 1000 laser rangefinder was used to acquire indoor building data which led to the acquisition of an inaccurate geometry of building. The connection between surveying benchmarks was established using Delaunay triangulation. Dijkstra algorithm was used to find shortest path in between building floors. The modeling results were evaluated against an accurate geometry of indoor building environment which was acquired using highly-accurate Trimble M3 total station. This research intends to investigate and propose a novel method of topological navigation network modeling with a less accurate geometrical model to overcome the need of required an accurate geometrical model. To control the uncertainty of the calibration and of the reconstruction of the building from the measurements, interval analysis and homotopy continuation will be investigated in the near future.     

Six decades of agricultural land use change in Bangladesh: Effects on crop diversity,productivity, food availability and the environment, 1948–2006

This paper provides a detailed analysis of agricultural land use change in Bangladesh over a 59‐year period (1948–2006) and examines how these have impacted crop diversity, productivity, food availability and the environment. The key findings of the analysis are: first, land use intensity has increased significantly over this period, mainly from the widespread adoption of a rice‐based Green Revolution technology package beginning in the early 1960s; second, contrary to expectation, crop diversity too has increased; third, although land productivity has increased significantly, declines in the productivity of fertilizers and pesticides raise doubts over sustaining agricultural growth; fourth, food availability has improved, with a reversal in the dietary energy imbalance in recent years despite a high population growth rate; and finally, the production environment has suffered with widespread soil nutrient depletion experienced in many agroecological regions. The policy implication points towards crop diversification as a desired strategy for agricultural growth to improve resource economy, productivity and efficiency in farming in Bangladesh.     

On the mechanism of X-ray production by dart leaders of lightning flashes

Radiation with energies up to about 250 keV associated with the dart leader phase of rocket-triggered lightning were reported by Dwyer et al. (2004). The mechanism of X-ray generation by dart leaders, however, is unknown at present. Recently, Cooray et al., in pressPlease provide complete bibliographic details for Ref. cooray e al., in press and Saleh et al., in press if available., Cooray et al., 2009a developed physical concepts and mathematical techniques necessary to calculate the electric field associated with the tip of dart leaders. We have utilized the results of these calculations together with the energy dependent frictional force on electrons, as presented by Moss et al. (2006), to evaluate the maximum energy an electron will receive in accelerating in the dart-leader-tip electric field. The main assumptions made in performing the calculations are: (a) the dart leader channel is straight and vertical; (b) the path of the electrons are straight inside the channel; and (c) the decay of the channel temperature is uniform along the length of the dart leader. In the calculation, we have taken into account the fact that the electric field is changing both in space and time and that the gas in the defunct return stroke channel is at atmospheric pressure and at elevated temperature (i.e. reduced gas density). The results of the calculation show that for a given dart leader current there is a critical defunct-return-stroke-channel temperature above which the cold electron runaway becomes feasible. For a typical dart leader, this temperature is around 2500 K. This critical temperature decreases with increase in dart leader current. Since the temperature of the defunct return stroke channel may lie in the range of 2000–4000 K, the results show that the electric field at the tip of dart leaders is capable of accelerating electrons to MeV energy levels.     

Description of the biology of Caspian vimba, Vimba vimba (Linnaeus, 1758), in Gorgan Bay-Miankaleh Wildlife Refuge (southeast Caspian Sea)

We collected Vimba vimba throughout the spawning season (mid April to mid June, 2007) in Gorgan Bay (south-western Iran) and investigated its age, growth, and reproductive traits. The maximum age was 5⁺ years. Both sexes grew allometrically (positive for males: b=3.140 9 and negative for females: b=2.791 4). The von Bertalanffy growth functions were described by the formulae L _t =32.565(1-e^{−0.184(t+0.530)}) for males and L _t =35.950(1-e^{−0.179(t+0.529)}) for females. The overall sex ratio was balanced, but males were predominant in the smaller size classes and females in the larger size classes. Based on the gonadosomatic index (GSI) values, spawning appears to occur between late April and late May in the bay. The highest mean GSI was 6.44 for males in early May and 20.36 for females in late April. Absolute fecundity varies from the minimum of 5 436 eggs for age 3⁺ fish to the maximum of 36 141 eggs for age 5⁺ fish. Fecundity was also positively correlated with fish size (length and weight). Egg diameter ranged from 1.05 to 1.70 mm in the mean of 1.42 mm. There was no correlation between female size and ova diameter.     

Distribution of heavy metals in the core sediments of a tropical wetland system

Five sediment cores from the fresh water region of the Vembanad wetland system were studied for the trace element contents The average concentration of iron, manganese, nickel, copper, zinc, cadmium, lead, mercury and chromium were determined. The core samples were collected using gravity type corer, digested with a mixture of nitric acid and perchloric acid and analyzed by atomic absorption spectrophotometry. Heavy metals such as iron, copper, nickel and zinc reported enrichment towards the surface of the core sediment sample collected from the centre of the lake. Lead, cadmium and mercury showed uniform distribution through out the core. Quality of the sediments were evaluated based on sediment quality guidelines, pollution load index, sum of toxic units and with effect range low/effect range median and threshold effect level/probable effect level values of Environmental Protection Agency guidelines. The degree of contamination for each station was determined. The concentration of different heavy metals has been compared with the world average concentration of shale values. Results of the analysis showed that Vembanad lake is facing serious metal pollution with increased rate of deposition.     

Arsenic in freshwater systems: Influence of eutrophication on occurrence,distribution, speciation,and bioaccumulation

Arsenic exists in a variety of chemical forms, and microbial metabolism results in the occurrence of thermodynamically unstable arsenite (As^III) and methylarsenic compounds in freshwaters (rivers and lakes). The inorganic forms (As^V and As^III) and the methylated forms (methylarsonic acid; MMAA^V and dimethylarsinic acid; DMAA^V) are the main species of As in freshwaters while the bulk of the total dissolved As is inorganic species. Although the predominant forms of methylarsenic compounds are consistently DMAA^V followed by MMAA^V, the DMAA^III and MMAA^III species have also been found in freshwaters. Several observations have revealed that phytoplankton activities are responsible for the seasonal variations of methylarsenic compounds in freshwaters. Although it was unclear if the occurrences of methylarsenic compounds were from the breakdown of larger molecules or the end-products of phytoplankton biosynthesis, recent studies have revealed that less toxic As–glutathione complexes are intermediates in the biosynthesis of organoarsenic compounds by phytoplankton. Recent studies have also revealed that eutrophication plays an important role in the production, distribution, and cycling of methylarsenic compounds in freshwaters. In this review, the recent reports on the influence of eutrophication on distribution, speciation, and bioaccumulation in freshwaters are discussed.     

Estimation of concentration and exposure doses due to radon by using CR-39 plastic track detectors in the residences of Sudhnuti, Azad Kashmir, Pakistan

This paper presents the results of indoor radon concentration measurements in 120 dwellings of district Sudhnuti of Azad Kashmir. Measurements were taken with CR-39 passive alpha track detector. CR-39 based box type radon detectors were installed in a bedroom and living rooms of each house. The detectors were retrieved after exposing to indoor radon for period of 6 months and then etched in 6 M NaOH at 80°C for 16 h, the observed track densities were converted in to the indoor radon concentration. Indoor radon concentration varied from 20 ± 12 to 170 ± 4 Bq m⁻³ for the houses of the district Sudhnuti. Arithmetic mean (AM), geometric mean (GM) and geometric standard deviations (GSD) were found to be 82 ± 6, 77 ± 6 and 1.51, respectively. The minimum value of weighted average radon concentration was recorded in one of the house of Mang town, whereas the maximum value was found in the Pattan Sher Khan region. Doses due to indoor radon exposure vary from 0.50 ± 0.31 to 4.28 ± 0.11 mSv year⁻¹ AM, GM and GSD. of mean effective doses were found to be 2.06 ± 0.13, 1.95 ± 0.18 and 1.51, respectively. According to the recommendations made by the Health Protection Agency, UK (200 Bq m⁻³) all the houses surveyed are within the safe limits.     

Dynamics of hourly sea level at Hillarys Boat Harbour,Western Australia: a chaos theory perspective

Water level forecasting using recorded time series can provide a local modelling capability to facilitate local proactive management practices. To this end, hourly sea water level time series are investigated. The records collected at the Hillarys Boat Harbour, Western Australia, are investigated over the period of 2000 and 2002. Two modelling techniques are employed: low-dimensional dynamic model, known as the deterministic chaos theory, and genetic programming, GP. The phase space, which describes the evolution of the behaviour of a nonlinear system in time, was reconstructed using the delay-embedding theorem suggested by Takens. The presence of chaotic signals in the data was identified by the phase space reconstruction and correlation dimension methods, and also the predictability into the future was calculated by the largest Lyapunov exponent to be 437 h or 18 days into the future. The intercomparison of results of the local prediction and GP models shows that for this site-specific dataset, the local prediction model has a slight edge over GP. However, rather than recommending one technique over another, the paper promotes a pluralistic modelling culture, whereby different techniques should be tested to gain a specific insight from each of the models. This would enable a consensus to be drawn from a set of results rather than ignoring the individual insights provided by each model.