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Amer A. Al-Rawas 《Engineering Geology》1999,53(3-4):327-350
The factors controlling the expansive nature of the soils and rocks in Northern Oman were studied. Basic geotechnical data from over 40 sites were collected and using empirical relationships, swelling potentials were identified. A laboratory testing program was carried out using undisturbed samples from these swell pressures up to 3.5 MPa, and swell percent values up to 30 were measured. The clay minerals and cations of these samples were determined and Na-smectite was identified as being the main clay-mineral present. Microfabric studies showed generally dense clay matrices. However, these swelling materials exist as impersistent bands with non-swelling soils and rocks which makes prediction of the ground heave problematic. 相似文献
2.
Naga Mangala SudheepKandikere Ramaiah Sridhar 《Limnologica》2012,42(2):87-94
The hyporheic zones constitute a major site of storage of organic matter and energy flow in freshwater ecosystems. To complement the studies carried out in North America and Europe, we evaluated the sediment quality and occurrence of aquatic hyphomycetes in coarse particulate organic matter (CPOM; ≥5 mm) and fine particulate matter (FPM; ≤1 mm) in three locations of Kaiga stream and eight locations of Kadra dam of the River Kali in Western Ghats. The pH of sediments of stream and dam was acidic (5.8-6.6) and the average organic carbon of stream sediments was higher than dam sediments (8.6% vs. 3.9%). Among the eight minerals monitored, Fe was highest in all sediments and Ni was below detectable limit in four dam sediments. Spores of aquatic hyphomycetes were directly released from the CPOM fractions of sediments upon bubble chamber incubation, while the FPM fractions produced spores indirectly by colonization of sterile leaf baits followed by bubble chamber incubation. The species richness and diversity in CPOM was higher than FPM in stream as well as dam sediments. The Sorensen's similarity indices between the fungal flora of CPOM in stream (66.7-81.8%) and dam (69.2-88%) locations were generally higher than FPM. The spore output per mg CPOM was between 1215 (dam) and 3384 (stream). The species richness was negatively correlated with Cr (P < 0.01; r = −1.000) of stream sediments, while it was negatively correlated with organic carbon (P < 0.05; r = −0.740) and positively correlated with K (P < 0.05; r = 0.750) of dam sediments. Occurrence and survival of aquatic hyphomycetes in hyporheic habitats of freshwater bodies indicate the importance of such zones as reservoir of fungal inoculum necessary in fundamental functions such as organic matter processing and energy flow. The present study provides baseline data on the sediment quality and fungal composition of stream and dam locations of River Kali of Kaiga region, which will develop as center of industrial activities in future. 相似文献
3.
Kireet Kumar M. S. Miral Sneh Joshi Namrata Pant Varun Joshi L. M. Joshi 《Environmental Geology》2009,58(6):1151-1159
The present study investigates solute dynamics of meltwater of Gangotri glacier system in terms of association of different
chemical compounds with the geology of the area. In the meltwater, the presence of cations varied as c(Mg2+) > c(Ca2+) > c(Na+) > c(K+), while order of concentration of anions has been c(HCO3
−) > c(SO4
2−) > c(Cl−) > c(NO3
−) in years 2003 and 2004. The magnesium and calcium are found as the dominant cations along with bicarbonate and sulphate
as dominant anions. The high ratios of c(Ca2+ + Mg2+)/total cations and c(Ca2+ + Mg2+)/c(Na+ + K+) indicate that the meltwater chemistry of the Gangotri glacier system catchment is mostly controlled by carbonate weathering.
Attempts are made to develop rating curves for discharge and different cations. Sporadic rise in discharge without corresponding
rise in concentration of most of cations is responsible for their loose correlation in a compound valley glacier like Gangotri
glacier. 相似文献
4.
An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO2 and brine consisting in equal molal concentrations of NaCl and CaCl2. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO2 storage in deep saline aquifers. The dependence of CO2/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO2/NaCl solution and CO2/CaCl2 solution. CO2/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO2/NaCl solution and CO2/CaCl2 solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts. 相似文献
5.
The effectiveness of CO2 storage in deep saline aquifers and hydrocarbon reservoirs is governed, among other factors, by the interfacial tension between the injected CO2 and formation water (brine). Experimental data on CO2/water and CO2/NaCl solution have revealed that the interfacial tension depends on the pressure, temperature and water salinity. However, there is still a lack of data for other salts (such as MgCl2 and CaCl2) which are also present in aquifers and carbonate reservoirs. 相似文献
6.
Tayel El-Hasan Kamal Momani Jafar Al-Nawayseh Khaled Al-Nawayseh 《Environmental Geology》2008,54(1):103-110
The Dead Sea as a unique geological and geographical phenomenon has an effect on its adjacent areas. Therefore, 17 sampling
sites at the eastern highlands facing the Dead Sea; beside three blank sites were collectedlocated during summer (2005). The
aim was to investigate such influence on the chemical and mineralogical composition of dry deposition, and to measure the
settling rate. The investigations showed that the depositional rate at the studied sites was much lower than other areas at
central and southern Jordan. The average heavy metal contents are almost similar in all sampling sites and the blanks, and
they exhibit similar enrichment series, whereas, the meaningful difference between sampling sites and blank was in cation
and anion content, which caused different enrichment series between the two sites. The index of pollution (IP) confirms that
mainly cations and anions have IP > 1.0 and they dominate the southern and the closest sampling sites to the Dead Sea. The
XRD results reveals that the studied samples have minor phases such as halite, gypsum, and dolomite. Meanwhile, these mineral
phases are not found in blank samples. All these results indicates the influence of the Dead Sea, as it is a highly saline
large water mass, which accompanied with by high evaporation rates causing causes the atmosphere over the Sea to be enriched
with these cations, anions, elements and minerals, which eventually are adsorbed in air particulate or carried out as dry
deposition and transported by the NW–SE prevailing winds, and fall over the eastern highlands. 相似文献
7.
Relationship of environmental geochemistry to soil degradation in Helwan catchment, Egypt 总被引：1，自引：0，他引：1
Ahmed A. Melegy 《Environmental Geology》2005,48(4-5):524-530
Environmental geochemistry plays an important role in understanding the distribution of major cations (Ca2+, Mg2+, Na+, K+) in Helwan catchment, south Cairo, Egypt. Evaluation of soil mechanical erosion rate, depletion rate, exchangeable rates
of base cations and sodium adsorption ratios are essential for understanding soil degradation problems in the representative
Helwan catchment. Soil erosion is a natural process. It often becomes a problem when human activity causes it to occur much
faster than under natural conditions. The results of the mechanical erosion rate of soil and the exchangeable rates of base
cations are 1845 and 80.3 kg ha−1 yr−1, respectively. The high intensity of the mechanical erosion rate is probably attributed to the high specific surface area
of the studied type of Vertisol, intensive application of fertilizer and industrial activities. Mechanical erosion of soil,
exchangeable rate of base cations and the depletion rate of base cations are almost inexhaustible sources of sodium, and all
these increase the problem of sodic soils and may affect plant productivity in Helwan catchment. 相似文献
8.
Prof. A. Della Giusta Dr. F. Princivalle Dr. Susanna Carbonin 《Mineralogy and Petrology》1987,37(3-4):315-321
Summary The crystal structures of two natural magnetites were refined. Both turned out to have equipoints 8a and 16d (Fd3m) fully occupied and hence different from type I and type II defect structures investigated by Fleet (1981, 1982). It was possible to improve the cation radii for Fe2+ ad Fe3+ in octahedral and tetrahedral coordinations for pure and almost pure magnetites obtaining very good agreement between observed and calculated values of the two independent geometric structure parameters, i.e. cell edge and oxygen coordinate. The present results lead to an estimate of inversion parameter i in (Fe
1–i
2+
Fe
i
3+
)(Fe
i
2+
Fe
2t-i
3+
)O4, of about 0.90, equal for all the four pure magnetites, independently of type of structure and also of cooling history.
Kristallstruktur und kationverteilung von einigen natürlichen magnetiten
Zusammenfassung Die Kristallstrukturen von zwei natürlichen Magnetiten wurden verfeinert. Es stellte sich heraus, daß ihre Gitterplätze 8 a und 16d (Fd 3 m) voll besetzt sind, und sich somit von den von Fleet (1981, 1982) bestimmten Defektstrukturen unterscheiden. Die Kationradien für Fe2+ und Fe3+ in Oktaeder- und Tetraeder-Koordinationen wurden für reine und fast reine Magnetite verbessert. Dabei wurde eine gute Korrelation zwischen beobachteten und berechneten Werten der beiden unabhängigen Parameter in der Struktur, d.h. Gitterkonstante und Sauerstoff-Ortsparameter gefunden. Die vorliegenden Ergebnisse bringen einen Umkehrparameter i in (Fe 1–i 2+ Fe i 3+ )(Fe i 2+ Fe 2–i 3+ )O4 von ungefähr 0.90, der in allen reinen Magnetiten gleich und unabhängig von dem Strukturtyp sowie dem Abkühlverhalten ist.相似文献
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