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1.
Salinity mapping of coastal groundwater aquifers using hydrogeochemical and geophysical methods: a case study from north Kelantan,Malaysia 总被引:2,自引:0,他引:2
Integrated hydrogeochemical and geophysical methods were used to study the salinity of groundwater aquifers along the coastal
area of north Kelantan. For the hydrogeochemical investigation, analysis of major ion contents of the groundwater was conducted,
and other chemical parameters such as pH and total dissolved solids were also determined. For the geophysical study, both
geoelectrical resistivity soundings and reflection seismic surveys were conducted to determine the characteristics of the
subsurface and groundwater contained within the aquifers. The pH values range from 6.2 to 6.8, indicating that the groundwater
in the study area is slightly acidic. Low content of chloride suggests that the groundwater in the first aquifer is fresh,
with an average concentration of about 15.8 mg/l and high geoelectrical resistivity (>45 ohm m). On the other hand, the groundwater
in the second aquifer is brackish, with chloride concentration ranging from 500 mg/l to 3,600 mg/l and very low geoelectrical
resistivity (<45 ohm m) as well as high concentration of total dissolved solids (>1,000 mg/l). The groundwater in the third
aquifer is fresh, with chloride concentrations generally ranging from 2 mg/l to 210 mg/l and geoelectrical resistivity of
greater than 45 ohm m. Fresh and saltwater interface in the first aquifer is generally located directly in the area of the
coast, but, for the second aquifer, both hydrogeochemical and geoelectrical resistivity results indicate that the fresh water
and saltwater interface is located as far as 6 km from the beach. The considerable chloride ion content initially suggests
that the salinity of the groundwater in the second aquifer is probably caused by the intrusion of seawater. However, continuous
monitoring of the chloride content of the second aquifer indicated no significant changes with time, from which it can be
inferred that the salinity of the groundwater is not affected by seasonal seawater intrusion. Schoeller diagrams illustrate
that sulphate concentrations of the groundwater of the second aquifer are relatively low compared to those of the recent seawater.
Therefore, this result suggests that the brackish water in the second aquifer is probably from ancient seawater that was trapped
within the sediments for a long period of time, rather than due to direct seawater intrusion. 相似文献
2.
Nur Islami Samsudin Hj Taib Ismail Yusoff Azman Abdul Ghani 《Environmental Earth Sciences》2012,65(3):699-712
Integrated geoelectrical resistivity, hydrochemical and soil property analysis methods were used to study the groundwater
characteristics of sandy soils within a shallow aquifer in the agriculture area, Machang. A pilot test investigation was done
prior to the main investigation. The area was divided into two sites. Test-Site 1 is non-fertilized; Test-Site 2 is the former
regularly fertilized site. From the surface to depths of 75 cm, a lower average resistivity was obtained in Test-Site 2 (around
0.37 less than in Test-Site 1). The presence of nitrate and chloride contents in pore water reduced the resistivity values
despite the low moisture content. The pH values for the whole area range from 4.11 to 6.88, indicating that the groundwater
is moderately to slightly acidic. In the southern region, concentration of nitrate is considered to be high (>20 mg/l), while
it is nearly zero in the northern region. In the south, the soil properties are similar. However, the geoelectrical model
shows lower resistivity values (around 18 Ω m) at the sites with relatively high nitrate concentration in the groundwater
(>20 mg/l). Conversely, the sites with low nitrate concentration reveal the resistivity values to be higher (>35 Ω m). Basement
and groundwater potential maps are generated from the interpolation of an interpreted resistivity model. The areas that possibly
have nitrate-contaminated groundwater have been mapped along with groundwater flow patterns. The northern part of the area
has an east to west groundwater flow pattern, making it impossible for contaminated water from the southern region to enter,
despite the northern area having a lower elevation. 相似文献
3.
Evaluation of hydrogeochemical processes in the Pleistocene aquifers of Middle Ganga Plain, Uttar Pradesh, India 总被引:4,自引:4,他引:0
Janardhana Raju Nandimandalam 《Environmental Earth Sciences》2012,65(4):1291-1308
Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting
a total of fifty-one groundwater samples in shallow (<25 m) and deep aquifer (>25 m) in the Varanasi area. Hydrochemical facies,
Mg-HCO3 dominated in the largest part of shallow groundwater followed by Na-HCO3 and Ca-HCO3 whereas Ca-HCO3 is dominated in deep groundwater followed by Mg-HCO3 and Na-HCO3. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave
part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump)
within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical
modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions
occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate
bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity
in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer
are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals. 相似文献
4.
Medhat A. El-Bihery 《Environmental Geology》2009,58(5):1095-1105
Recently, Ras Sudr (the delta of Wadi Sudr) area received a great amount of attention due to different development expansion
activities directed towards this area. Although Quaternary aquifer is the most prospective aquifer in Ras Sudr area, it has
not yet completely evaluated. The present work deals with the simulation of the Quaternary groundwater system using a three-dimensional
groundwater flow model. MODFLOW code was applied for designing the model of the Ras Sudr area. This is to recognize the groundwater
potential as well as exploitation plan of the most prospective aquifer in the area. The objectives were to determine the hydraulic
parameters of the Quaternary aquifer, to estimate the recharge amount to the aquifer, and to determine the hydrochemistry
of groundwater in the aquifer. During this work, available data has been collected and some field investigation has been carried
out. Groundwater flow model has been simulated using pilot points’ method. SEAWAT has been also applied to simulate the variable-density
flow and sea water intrusion from the west. It can be concluded that: (1) the direction of groundwater flow is from the east
to the west, (2) the aquifer system attains a small range of log-transformed hydraulic conductivity. It ranges between 3.05
and 3.35 m/day, (3) groundwater would be exploited by about 6.4 × 106 m3/year, (4) the estimated recharge accounts for 3 × 106 m3/year, (5) an estimated subsurface flow from the east accounts for 2.7 × 106 m3/year, (6) the increase of total dissolved solids (TDS) most likely due to dilution of salts along the movement way of groundwater
from recharge area to discharge area in addition to a contribution of sea water intrusion from the west. Moreover, it is worth
to note that a part of TDS increase might be through up coning from underlying more saline Miocene sediments. It is recommended
that: (1) any plan for increasing groundwater abstraction is unaffordable, (2) reliable estimates of groundwater abstraction
should be done and (3) automatic well control system should be made. 相似文献
5.
Ibticem Chamtouri Habib Abida Hafedh Khanfir Salem Bouri 《Environmental Geology》2008,55(5):1123-1133
Groundwater in Sfax City (Tunisia) has been known since the beginning of the century for its deterioration in quality, as
a result of wastewater recharge into the aquifer. An average value of 12 × 106 m3 of untreated wastewater reaches the groundwater aquifer each year. This would result not only in a chemical and biological
contamination of the groundwater, but also in an increase of the aquifer piezometric level. Quantitative impacts were evaluated
by examining the groundwater piezometric level at 57 surface wells and piezometers. The survey showed that, during the last
two decades, the groundwater level was ever increasing in the urban area with values reaching 7 m in part; and decreasing
in Sidi Abid (agricultural area) with values exceeding −3 m. Groundwater samples for chemical and microbial analysis were
collected from 41 wells spread throughout the study area. Results showed significantly elevated levels of sodium, chlorides,
nitrates and coliform bacteria all over the urban area. High levels (NO3: 56–254 mg/l; Na >1,500 mg/l; Coliforms >30/100 ml) can be related to more densely populated areas with a higher density
of pit latrine and recharge wells. Alternatively results showed a very variable chemical composition of groundwater, e.g.
electrical conductivity ranges from 4,040 to19,620 μs/cm and the dry residual varies between 1.4 and 14 g/l with concentrations
increasing downstream. Furthermore a softening of groundwater in Set Ezzit (highly populated sector) was observed. 相似文献
6.
现有的井群疏干、地下巷道集中排水、地表地下联合疏干方法都已比较成熟有效,但当矿区的地下水系统由非均质各向异性、低渗透性含水介质组成时,井群疏干受到低渗透性含水层和高倾角裂隙的制约,无法达到良好的疏干效果。地下巷道集中排水方法一次性工程投入很大,含水层富水性极度不均时易造成许多不必要的浪费;地表地下联合疏干方法的地面部分对矿坑边坡安全和采场作业都会造成一定的影响。结合马钢集团南山矿业公司高村露天铁矿的地下水疏干技术研究专项,调查分析了矿区地质和水文地质条件,含水介质特点及含水层富水特征,借助GMS软件建立了高村矿区地下水水流模型,提出了辐射井疏干技术的设想,并依据前人提出的"渗流-管流耦合模型"模拟辐射井,完成了此类矿山的地下水辐射井疏干方法的初步研究。 相似文献
7.
8.
Samir Kamel 《Environmental Earth Sciences》2011,63(1):189-199
The hydrodynamic groundwater data and stable isotopes of water have been used jointly for better understanding of upward leakage
and mixing processes in the Djerid aquifer system (southwestern Tunisia). The aquifer system is composed of the upper unconfined
Plio-Quaternary (PQ) aquifer, the intermediate (semi-)confined Complex Terminal (CT) aquifer and the deeper confined Continental
Intercalaire (CI) aquifer. A total of 41 groundwater samples from the CT and PQ aquifers were collected during June 2001.
The stable isotope composition of waters establishes that the CT deep groundwater (depleted as compared to present Nefta local
rainfall) is ancient water recharged during late Quaternary time. The relatively recent water in the shallow PQ aquifer is
composed of mixed water resulting from upward leakage and sporadic meteoric recharge. In order to characterize the meteoric
input signal for PQ in the study area, rainfall water samples were collected during 4 years (2000–2003) at the Nefta meteorological
station. Weighted mean values of isotopic contents with respect to rainfall amounts have been computed. Despite the short
collection period in the study area, results agree with those found in Beni Abbes (southwestern Algerian Sahara) by Fontes
on 9 years of rainfall surveillance. Stable isotopic relationships provide clear evidence of shallow PQ aquifer replenishment
by deep CT groundwater. The 18O/upward leakage rate allowed the identification of distinctive PQ waters related to CT aquifer configuration (confined in
the western part of the study area, semi-permeable in the eastern part). These trends were confirmed by the relation 18O/TDS. The isotope balance model indicated a contribution of up to 75% of the deep CT groundwater to the upper PQ aquifer
in the western study area, between Nefta and Hazoua. 相似文献
9.
Sandow Mark Yidana Samuel Ganyaglo Bruce Banoeng-Yakubo Thomas Akabzaa 《Journal of African Earth Sciences》2011,59(2-3):185-194
A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10?5 m/d to 7.14 × 10?4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast–southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization. 相似文献
10.
The oxidation of pyrite results in sulphate concentrations from 1,300 to 2,000 mg/l in the dump water of the open cast mine
Inden, which is located in Germany. Under near-neutral pH and reduced redox conditions, precipitation of siderite (FeCO3) retains up to 85% of the pre-liberated ferrous iron, so that iron concentrations in the dump water are relatively low as
compared to the concentrations of sulphate. The highly mineralised dump water will enter the aquifer system northwards of
Inden during the next centuries. This area is used intensely for water extraction. Model calculations show that there will
be no problem of acidification in the adjacent aquifer system and, therefore, no problem of high heavy metal concentrations
during the next centuries. The most important problem will be high sulphate concentrations in the groundwater. Besides dispersion
and diffusion, there are no chemical mechanisms that lower the sulphate concentrations downstream. On the basis of the simulations,
sulphate plumes of about 1–2 km in width and up to 15 km in length are expected. Within the core of these plumes, sulphate
concentrations will be above the drinking water limits. 相似文献