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1.
Application of remote-sensing data to groundwater exploration: A case study of the Cross River State, southeastern Nigeria 总被引：12，自引：2，他引：10
The Cross River State, Nigeria, is underlain by the Precambrian-age crystalline basement complex and by rocks of Cretaceous
to Tertiary age. The exploration for groundwater in this area requires a systematic technique in order to obtain optimum results,
but the non-availability of funds and facilities has made it extremely difficult to carry out site investigations prior to
the drilling of water wells. Therefore, the failure rate is as high as 80%. In order to delineate areas that are expected
to be suitable for future groundwater development, black and white radar imagery and aerial photographs were used to define
some hydrological and hydrogeological features in parts of the study area. Lineament and drainage patterns were analysed using
length density and frequency. Lineament-length density ranges from 0.04–1.52; lineament frequency is 0.11–5.09; drainage-length
density is 0.17–0.94, and the drainage frequency is 0.16–1.53. These range of values reflect the differences in the probability
of groundwater potentials. Results were then used to delineate areas of high, medium, and low groundwater potential. Study
results also indicate that correlations exist between lineament and drainage patterns, lithology, water temperature, water
conductivity, well yield, transmissivity, longitudinal conductance, and the occurrence of groundwater.
Received, August 1994 · Revised, March 1996, June 1996 · Accepted, October 1996 相似文献
2.
Hydrochemical facies in parts of the Nigerian basement complex 总被引：3，自引：0，他引：3
Water analyses usually involve large amounts of data that require sorting to aid in interpretation. One method that could
be used is the hydrochemical facies diagrams. The hydrochemical facies of groundwater from four drainage basins of the Nigerian
basement complex, Ife, Asa, Shika, and Kan Gimi, are evaluated using trilinear and Stiff diagrams similar to methods used
in lithofacies and geochemical studies. The hydrochemical facies for the basins studied are influenced, aside from the lithology,
by the rainfall and their proximity to the sea. In general, no single cation–anion pair exceeds 50%, hence an appreciable
percentage of the groundwater in the study areas is of the nondominant type. Within the overburden aquifer of the basement
complex, with limited regional flow, a rainfall of about 1150 mm per annum is arbitrarily set as the boundary between alkaline
and saline groundwater.
Received: 11 August 1995 · Accepted: 6 November 1995 相似文献
3.
Delineation of saltwater intrusion into the freshwater aquifer of Lekki Peninsula,Lagos, Nigeria 总被引：2，自引：0，他引：2
A. A. Adepelumi B. D. Ako T. R. Ajayi O. Afolabi E. J. Omotoso 《Environmental Geology》2009,56(5):927-933
Recently, the deterioration of water quality in the coastal zones of Lekki Peninsula area of Lagos due to saltwater infiltration
into the freshwater aquifer has become a major concern. With the aim of providing valuable information on the hydrogeologic
system of the aquifers, the subsurface lithology and delineating the groundwater salinity, vertical electrical resistivity
(VES) sounding survey was carried out utilizing surface Schlumberger electrode arrays, and electrode spacing varying between
1 and 150 m. The DC resistivity surveys revealed significant variations in subsurface resistivity. Also, the VES resistivity
curves showed a dominant trend of decreasing resistivity with depth (thus increasing salinity). In general, the presence of
four distinct resistivity zones were delineated viz.: the unconsolidated dry sand (A) having resistivity values ranging between
125 and 1,028 Ωm represent the first layer; the fresh water-saturated soil (zone B) having resistivity values which correspond
to 32–256 Ωm is the second layer; the third layer (zone C) is interpreted as the mixing (transition) zone of fresh with brackish
groundwater. The resistivity of this layer ranges from 4 to 32 Ωm; while layer four (zone D) is characterized with resistivities
values generally below 4 Ωm reflecting an aquifer possibly containing brine. The rock matrix, salinity and water saturation
are the major factors controlling the resistivity of the formation. Moreover, this investigation shows that saline water intrusion
into the aquifers can be accurately mapped using surface DC resistivity method. 相似文献
4.
Lithogenic concentrations of trace metals in soils and saprolites over crystalline basement rocks: A case study from SW Nigeria 总被引：2，自引：0，他引：2
Moshood N. Tijani Olugbenga A. Okunlola Akinlolu F. Abimbola 《Journal of African Earth Sciences》2006,46(5):427-438
In this study, an assessment of the lithogenic concentrations of trace metals in soils and saprolite over basement rock units in Ibadan, SW-Nigeria is presented in respect of bedrock types and geochemical controls on the weathering-associated release of trace metals. Consequently, soil, weathered and fresh rock samples from the Precambrian Basement of SW Nigeria were collected from three different bedrock units within Ibadan metropolis and subjected to mineralogical and geochemical analyses. The analytical results revealed major proportions of oxides in the range of 18–20% Al2O3, 2–6% Na2O and 1–6% K2O for weathered profiles over granite-gneiss and pegmatite units, compared to 2–3% Al2O3, <0.5% Na2O and <1.0% K2O over schist-quartzite. For the trace elements, weathered profiles on granite-gneiss and schist-quartzite settings exhibit similar enrichment trends (enrichment factor, EF l) for most of the trace elements, unlike the pegmatite bedrock. However, enrichments are relatively greater in the top soil unit compared to the intermediate saprolite unit, especially for Pb, Ni, Zn, Cr, Co, Rb, Sr and Ba, a situation attributed to leaching and redistribution within the weathered profiles through pedogenetic process and percolating groundwater.Furthermore, the estimated weathering indices using Ruxton Ratio (RR = {SiO2/Al2O3}) and Chemical Index of Alteration (CIA = 100{Al2O3/[Al2O3 + CaO + Na2O + K2O]}) revealed RR of 2.9–3.7 and CIA of 54–73% for granite-gneiss and pegmatite units, implying medium levels of weathering, compared to RR of 30.8–35.5 and CIA of >60% for schist-quartzite units, which suggest weak chemical weathering. Also, the estimated high percentage loss, especially for Pb, Rb, Sr, Ba relative to the bedrocks, shows that the trace elements can be mobilized within the weathering profiles even at a low degree of chemical weathering. Such weathering-induced release of trace metals is of environmental significance as natural lithogenic input sources and as background reference for future monitoring of possible human/anthropogenic impacts. 相似文献
5.
Distribution of heavy metals in soils of Port Harcourt and its environs,Niger Delta,Nigeria 总被引：1，自引：0，他引：1
Geochemical evaluation of the distribution of heavy metals in soils of Port Harcourt and its environs in the Niger Delta region is presented in respect of anthropogenic factor and index of geoaccumulation. Sixteen (16) soil samples were collected from two horizons (0-10 cm and 100 cm) from the various grids and analyzed. The geo-chemical analyses showed the vertical and horizontal distributions of heavy metals. The results showed the ranges of the metals determined as follows: Pb (6.86-2.49)×10-6, with an average of 4.63×10-6; Cd (0.05-0.00)×10-6, with an average of 0.02×10-6, As (0.01-0.00)×10-6, with an average of 0.00×10-6. Cu (15.36-10.80) ×10-6, with an average of 13.36×10-6, and V (1.36-0.20)×10-6, with an average of 0.94×10-6. Quantification of the degree of pollution was carried out using anthropogenic factor (AF) and index of geoaccumulation (Igeo). The Igeo values of 0.06, 0.02 and 0.00 for Pb, Cd and As, respectively indicate low-level contamination while Zn (1.14) and V (1.40) show me-dium-level contamination. The sources of contamination are attributed to urbanized anthropogenic activities. The majority of the samples analyzed show that the AF values are less than 1 with the exception of vanadium (V) whose AF values range from 2.73 to 13.60×10-6. Vanadium is more enriched than As, Cd, Pb, and Cu. The order of degrees of anthropogenic contamination and index of geoaccumulation in the soil is V >Zn >Pb >Cu >Cd >AS. Metals were retained near the top soil and their concentrations in the deepest horizons were lower and normal for uncontaminated soils. Metal concentrations in the top soil horizons were significantly related to distance from the industrial and hu-man activities. 相似文献
6.
Rare-earth elements as source indicators of Pan-African granites from Obudu Plateau,Southeastern Nigeria 总被引：1，自引：1，他引：0
The rare-earth element （REE） concentrations of representative granite samples from the southeast of the Obudu Plateau, Nigeria, were analyzed with an attempt to determine the signatures of their source, evolutionary history and tectonic setting. Results indicated that the granites have high absolute REE concentrations （190×10^-6-1191×10^-6; av.=549×10^-6） with the chondrite-normalized REE patterns characterized by steep negative slopes and prominent to slight or no negative Eu anomalies. All the samples are also characterized by high and variable concentrations of the LREE （151×10^-6-1169×10^-6; av.= 466×10^-6）, while the HREE show low abundance （4×10^-6-107×10^-6; av.=28×10^-6）. These are consistent with the variable levels of REE fractionation, and differentiation of the granites. This is further supported by the range of REE contents, the chondrite-normalized patterns and the ratios of LaN/YbN （2.30-343.37）, CeN/YbN （5.94-716.87）, LaN/SmN （3.14-11.68） and TbN/YbN （0.58-1.65）. The general parallelism of the REE patterns, suggest that all the granites were comagmatic in origin, while the high Eu/Eu＊ ratios （0.085-2.807; av.=0.9398） indicate high fo2 at the source. Similarly, irregular variations in LaN/YbN, CeN/YbN and Eu/Eu＊ ratios and REE abundances among the samples suggest behaviors that are related to mantle and crustal sources. 相似文献
7.
Soil parent materials and soil properties in two separate catchment areas on the Jos Plateau, Nigeria 总被引：1，自引：0，他引：1
E.A. Olowolafe 《GeoJournal》2002,56(3):201-212
On the Jos Plateau, soils derived from basalt and volcanic ash are much more intensively and extensively utilized for agricultural
purposes than the granite soils. This study was carried out to determine the differences that may have contributed to this
discrimination. Twenty four soil profiles were dug and described in two separate catchment areas that really portray the variance.
Soil samples were analysed using standard procedures. The results show that basalt and volcanic ash-derived soils have relatively
deeper profiles, lower bulk density, higher contents of clay, organic matter, exchangeable bases, micro-nutrients (Cu & Zn)
and weatherable minerals. They are also higher in their CEC and base saturation percentage while available water capacity,
hydraulic conductivity and natural water content are more adequate in them. Hence, the basalt and volcanic ash soils are more
favourable for crop growth while the deficiencies in granite soils present more constraints to agricultural land use. Consequently,
there are differences between the soil types in their crop-yielding capacities. These differences constitute a reflection
of soil parent material influence. Agriculture in the area is mainly low-input. There is the need for improved management
practices for the enhancement of soil conditions of granite areas in particular and the whole area in general.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Two waste-disposal sites (old and new) in Calabar Municipality, SE Nigeria were evaluated to assess their suitability as
landfill sites and their impact on the groundwater. The field investigation included surface geological/hydrogeological and
geochemical studies. Leachate and groundwater were sampled and analysed for 3 months (April, May and June, 1997) for geochemical
characterisation. The results indicate that the two waste-disposal sites in the Calabar Municipality do not meet the requirements
as landfill sites. Physico-chemical analyses for temperature, pH, conductivity, dissolved oxygen, biological oxygen demand
after 5 days of incubation (BOD5), sulphate, nitrates, nitrite, trace and major elements in the leachate known to impact human health and the environment,
indicate high levels of pollution. The values for groundwater in the vicinity of the disposal sites were found to be within
the World Health Organisation (WHO) permissible limit.
Received: 29 March 1999 · Accepted: 3 January 2000 相似文献
9.
The present article is the second in a series of baseline water quality evaluation studies in parts of south-eastern Nigeria.
Study results indicate that the water samples from the study are generally acidic, soft and fresh in addition to low sodium
and salinity hazard. Regression equations indicate a good positive correlation between conductivity and Na, Ca, Mg and SO4. Ca-SO4 and Ca-Cl constitute the major facies in the area. Generally the waters in the area are good for most domestic and agricultural
purposes.
Received: 14 April 1997 · Accepted: 3 February 1998 相似文献
10.
M. 'N. Tijani 《Environmental Geology》1994,24(3):194-202
Detailed study of chemical analysis results of several groundwater samples (UNICEF-Assisted Water project, Kwara state, Nigeria) were carried out in an attempt to assess the quality and usability of groundwaters in the Moro area. Chemical analysis results indicate higher concentrations of Ca2+, Mg2+, and HCO3
– as compared to Na+, K+, Cl–, and SO4
2–. With exception of few locations where Fe is relatively higher, the concentrations of these ions together with other water quality parameters are all within permissible limits of the domestic and agricultural standards.On the basis of the analytical results, groundwaters in the study area are largely characterized as Ca-(Mg)-HCO3 type reflecting (possibly) young facies with limited migratory history. The occurrence of Ca-(Mg)-Na-HCO3 water type in certain areas is attributed to cation exchange processes. In addition, the observed scattered relationship between the TDS and the thickness of weathered horizons in the boreholes indicates the contribution of precipitation (recharge) to the ionic inputs in the groundwaters in addition to the weathering and dissolution processes. 相似文献