Electrical resistivity surveys to delineate groundwater potential aquifers in Peddavanka watershed,Anantapur District,Andhra Pradesh,India

Vertical electrical resistivity soundings were conducted in order to delineate groundwater potential aquifers in Peddavanka watershed, which is a catchment of about 398 km² in Anantapur District, Andhra Pradesh, India. The main lithologic units in the watershed are quartzite, limestone, shale, and alluvium. Ninety-nine vertical electrical soundings were conducted using the Schlumberger configuration, covering the entire watershed. The data were interpreted with the help of master curves and auxiliary point charts. Interpretations of VES were used to generate a top layer apparent resistivity contour map and longitudinal conductance map. Isoresistivity contour maps were prepared and interpreted in terms of resistivity and thickness of various sub-surface layers using computer software (SURFER), and isocontour diagrams depicting the depth to bedrock were prepared. Resistivity results were correlated with the existing lithology. Based on the depth to bedrock, the thickness of the saturated layer and the resistivity of the second layer, a groundwater potential map has been prepared, in which good, moderate, and poor zones are classified. The study reveals that the weathered and fractured portions in shale and limestone that occur in the southernmost and central portions of the watershed area constitute the productive water-bearing zones categorized as good groundwater potential aquifers.     

Environmental impact of drainage of Dianzi Iron Mine on the groundwater system of the Dawu Water Supply Base

Due to growing water extraction for industry and agriculture, the Dawu Water Supply Base, in the east of Zibo, China, has been in a state of serious over-extraction. It will also be affected by the deep drainage of the Dianzi Iron Mine, which will be exploited in 2005. As to the environmental impact on the groundwater system of the Dawu Water Supply Base is concerned, this paper makes a systematic study about the influence of the mine draining on the water-supply environment of the Dawu Water Supply Base by using the numerical model of groundwater system. The result shows that the groundwater level will have an additional drawdown of 1.2–1.8 m/yr by the mine draining alone. The numerical analysis results indicate that the optimal model for determining the best extraction plan is the solution for the contradiction between water supply and water drainage.     

A field evaluation of enhanced reductive dechlorination of chlorinated solvents in groundwater,New York Metropolitan Area

An initial assessment of an old manufacturing site with groundwater impacted by trichloroethene (TCE) contamination in the metropolitan New York area showed that the TCE was being removed naturally by reductive dechlorination. However, complete dechlorination was not expected at the site because the process was progressing too slowly under transitional to aerobic conditions at a degradation constant of –0.0013 and a TCE half life of 533 days. A pilot test was conducted at the site in which a carbohydrate substrate (molasses) was injected into the groundwater to create an In-Situ Reactive Zone (IRZ). Post-pilot test groundwater sampling and analysis indicated that an IRZ was created successfully as the total organic carbon (TOC) content and conductivity increased significantly while oxidation-reduction (REDOX) potential and dissolved oxygen (DO) decreased. The created IRZ caused enhanced reductive dechlorination of TCE at the site, found to proceed with a degradation constant of –0.0158 and a TCE half life of 44 days.     

Radon-rich waters in Russia

In radon mineral curative waters, according to Russian mineral water classification, the radon concentration should be greater than 185 Bq/l. There are about 30 mineral waters with high levels of radon in Russia. Radon-rich waters have high therapeutic effects. It is proven that natural background radiation stimulates the human immune system. Radon is a natural radioactive gas that has no taste, smell or color. Radon-222 is one of the heaviest elements in the zero groups of inert gases. It is a gaseous radioactive element. All radon isotopes are -emitters while the transformation of its decay products is accompanied by the emitting of -or -particles. The main products of radon decay are short-lived isotopes Po, Pb, Bi, and TL. Belonging to the uranium and thorium decay chain, radon isotopes form directly during the decay of radium isotopes. Therefore the radon concentration depends upon the concentration of its parent's isotope in water and rocks washed by it as well as upon the amount of radon emanation. Loose rocks or rocks with a great number of cracks are characterized by higher radon concentration (zones of tectonic disturbance, weathering crusts, etc.).Crystalline rocks usually have higher uranium concentrations than the average bedrock. Examples of rock types, which often have enhanced uranium concentration >5% ppm U includes the following: granites, syenites, pegmatite, acid volcanic rocks and acid gneisses. In the earth's crust radon migrates either in a gaseous or dissolved state. It can go to the surface without any chemical reaction. Formation of the radon-rich therapeutics waters of Russia has been analyzed, and most of them are genetically connected to crystalline acid rocks that have exceeded uranium-radium mineralization. The radon content in Russia reaches more than 8,000 Bq/l. Radon-rich waters of this type occur in the Altai, Karelia, St Petersburg and Trans-Baikal regions. Another type is connected to geodynamic activity of regions and secondary radioactivity. A well-known example of radon-rich waters of the second type is Pyatigorsk in the North Caucasus. Mixing confined carbon dioxide-hydrogen sulfide water and unconfined groundwater forms radon waters. The radon concentration is 1,170–2,430 Bq/l. The occurrence of radon-rich water deposits in other regions of Russia is described. Further investigation of the radon content in other geological environments will contribute to the environmental safety as well as to the solution to many genetic, hydrogeochronological, paleoreconstructive and prediction problems in hydrogeology.     

Timing and intensity of groundwater movement during Egyptian Sahara pluvial periods by U-series analysis of secondary U in ores and carbonates

Wet climatic episodes are known to have prevailed in the Egyptian Sahara several times during the late Quaternary, most recently during the Holocene 8000 yr ago. Earlier wet episodes have been recognized as having occurred during the past 300,000 yr and have been dated by U-series methods in speleothems and in lake travertines. We show here that the times of enhanced groundwater movement can also be determined by ²³⁰Th/²³⁴U dating of secondary U in ores of uranium, iron, and phosphate. We also present evidence that such acceleration of groundwater movements is indicated by relatively low ²³⁴U/²³⁸U activity ratios in the secondary uranium. Our new data show that pluvial periods in Egypt occurred during marine oxygen isotope stages 4, 5, 6, and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23,000-yr precession cycle of the Milankovich curve, modulated by the 100,000-yr eccentricity cycle.     

Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco)

The El Jadida landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 150 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the ground. At the site of this landfill, the groundwaters circulate deeply (10–15 m) in the Cenomanian rock (calcareous–marl), which is characterised by an important permeability from cracks. The soil is sand–clay characterized by a weak coefficient of retention.The phreatic water ascends to the bottom of three quarries, which are located within the landfill. These circumstances, along with the lack of a leachate collection system, worsen the risks for a potential deterioration of the aquifer.To evaluate groundwater pollution due to this urban landfill, piezometric level and geochemical analyses have been monitored since 1999 on 60 wells. The landfill leachate has been collected from the three quarries that are located within the landfill. The average results of geochemical analyses show an important polluant charge vehiculed by landfill leachate (chloride = 5680 mg l⁻¹, chemical oxygen demand = 1000 mg l⁻¹, iron = 23 000 μg l⁻¹). They show also an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 4.5 mS cm⁻¹ in electric conductivity, 1620 and 1000 mg l⁻¹ respectively in chlorides and sulfate (), 15–25 μg l⁻¹ in cadmium, and 60–100 μg l⁻¹ in chromium. These concentrations widely exceed the standard values for potable water.Several determining factors in the evolution of groundwater contamination have been highlighted, such as (1) depth of the water table, (2) permeability of soil and unsaturated zone, (3) effective infiltration, (4) humidity and (5) absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.     

同位素指示的巴丹吉林沙漠南缘地下水补给来源

通过恢复巴丹吉林沙漠及其周边地区大气降水氚值，并结合区域稳定同位素组合特征，揭示了区域地下水氚年龄的多解性与地下水稳定同位素的温度效应。恢复的1963年核试验期氚高峰值达到2 100 TU，进入90年代平均为60 TU。1960年以来降水补给的地下水氚值都应大于15 TU，而1963年的高峰氚衰变至今应在200 TU左右。地下水实测氚值较低，表明由现代少量降水补给的地下水与大量的古水进行了混合。影响降水中δ18O和δ2H分布的主要影响因子是月平均空气温度，对δ18O与δ2H的影响权重分别占到59.9%和57.0%。巴丹吉林沙漠及其周边地区地下水较低的稳定同位素组成表明，其补给主要是晚更新世较冷环境下形成的，来源于东南部的雅布赖山区，部分浅层地下水接受现代降水与河流的补给。      

Arsenic distribution and source in groundwater of Yangtze River Delta economic region,China

This thesis focuses Arsenic(As) distribution and occurrence in groundwater of Yangtze River Delta economic region, East China. 2019 groundwater samples were collected to analyze 26 chemical compositions, including As. The Principal Component Analysis(PCA) was used to find out As source in groundwater. The results show that average As concentration in groundwater of this study is 9.33 μg/l, and maximum As concentration is up to 510 μg/l. The variation coefficient is 314.34%. High arsenic phreatic water(10 μg/l) distributes along the Yangtze River and its estuary. Weak hydrodynamic conditions, wide p H value variation range and deteriorating environment are dominating factors, especially in Yangtze River Delta. The PCA suggests that arsenic in phreatic water is mainly of natural origin. Part of arsenic may directly originate from sediment organics and be related to organics decomposition.     

王府水源地可利用潜力评价

水资源贫乏的山丘地区,水源地一般选择在山前河谷平原区作为地下水开采区,随着经济社会的发展,需水量的加大,水源的保证程度也会降低.利用水源地的水文地质条件、区域用水情况和现状水源地开采量对王府水源地进行安全性评价.给出水源地安全性的定量指标.     

Effect of system variables and particle size on physical characteristics of air sparging plumes

Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure, well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60° were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%), or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging. However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which should reduce mass transfer limitations during sparging.