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611.
Alireza Riyahi Bakhtiari Mohamad Pauzi Zakaria Mohammad Ismail Yaziz Mohamad Nordin Hj Lajis Xinhui Bi Mohamad Che Abd Rahim 《Applied Geochemistry》2009,24(9):1777-1787
Four anoxic sediment cores were collected from Chini Lake, Malaysia in order to investigate the variability of polycyclic aromatic hydrocarbon (PAH) and perylene concentrations. The study also determined significant differences of perylene concentrations in different sediment layers. Total PAH concentrations ranged from 248 to 8098 ng g−1 in the samples. Diagnostic PAH ratios such as methylphenanthrenes/phenanthrene (MP/P), phenanthrene/anthracene (P/A) and fluoranthene/(fluoranthene + pyrene) (Fl/(Fl + Py) revealed a dominance of pyrogenic influences and partial petrogenic inputs to the top sediment layers. Perylene concentrations were high in the top layers (<12 cm) and increased with increasing depth. There is a significant positive correlation (r = 0.705, p = 0.01) between perylene concentrations and TOC. Analysis of variance (ANOVA) and LSD revealed significant differences (p < 0.05) in TOC-normalized perylene concentrations between the upper (<12 cm) and bottom layers (>12 cm). The average perylene concentrations accounted for 26–50% (0–12 cm) and 50–77% (12–36 cm) of pentacyclic-aromatic hydrocarbon isomers (PAI) present whereas it made up 10–34% (0–12 cm) and 46–66% (12–36 cm) of the total PAH. The average pyrene concentrations decreased with increasing depth and accounted for 62% (0–3 cm), 20–23% (3–12 cm) and 3–1.4% (12–36 cm) of perylene present. The results of hierarchical cluster analysis based on these ratios suggested different input sources for the top and bottom layers. It is concluded that the activity of termites on woody plants produced perylene which is supplied to the lake by run-off from the heavy and frequent rains in this Asian tropical climate. In addition, there was also in situ formation of perylene in the bottom layers due to diagenetic processes. 相似文献
612.
Nicholas J.G. Pearce John A. Westgate Guilherme A.R. Gualda Emma Gatti Ros F. Muhammad 《第四纪科学杂志》2020,35(1-2):256-271
The Youngest Toba Tuff contains five distinct glass populations, identified from Ba, Sr and Y compositions, termed PI (lowest Ba) – PV (highest Ba), representing five compositionally distinct pre-eruptive magma batches that fed the eruption. The PI–PV compositions display systematic changes, with higher FeO, CaO, MgO, TiO2 and lower incompatible element concentrations in the low-SiO2 PIV/PV, than the high-SiO2 PI–PIII compositions. Glass shard abundances indicate PIV and PV were the least voluminous magma batches, and PI and PIII the most voluminous. Pressure estimates using rhyolite-MELTS indicate PV magma equilibrated at ~6 km, and PI magma at ~3.8 km. Glass population proportions in distal tephra and proximal (caldera-wall) material describe an eruption which commenced by emptying the deepest PIV and PV reservoirs, this being preferentially deposited in a narrow band across southern India (possibly due to jet-stream and/or plinian eruption transport), and as abundant pumice clasts in the lowermost proximal ignimbrites. Later, shallower magma reservoirs erupted, with PI being the most abundant as the eruption ended, sourcing the majority of distal ash from co-ignimbrite clouds (PI- and PIII-dominant), where associated ignimbrites isolated earlier (PIV- and PV-rich) deposits. This study shows how analysis of tephra glass compositional data can yield pre-eruption magma volume estimates, and enable aspects of magma storage conditions and eruption dynamics to be described. 相似文献
613.
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615.
Several organisms have been used as indicators, bio-monitoring agents or test organisms in ecotoxicological studies. A close relative of the well established Japanese medaka, the Java medaka (Oryzias javanicus), has the potential to be a test organism. The fish is native to the estuaries of the Malaysian Peninsula, Thailand, Indonesia and Singapore. In this study, newly fertilised eggs were exposed to different concentrations of Cd and Hg. Observations were done on the development of the embryos. Exposure to low levels of Cd and Hg (0.01-0.05 ppm) resulted in several developmental disorders that led to death. Exposure to ≥1.0 ppm Cd resulted in immediate developmental arrest. The embryos of Java medaka showed tolerance to a certain extent when exposed to ≥1.0 ppm Hg compared to Cd. Based on the sensitivity of the embryos, Java medaka is a suitable test organism for ecotoxicology in the tropical region. 相似文献
616.
Pure-iron end-member hibbingite, Fe2(OH)3Cl(s), may be important to geological repositories in salt formations, as it may be a dominant corrosion product of steel waste canisters in an anoxic environment in Na–Cl- and Na–Mg–Cl-dominated brines. In this study, the solubility of Fe2(OH)3Cl(s), the pure-iron end-member of hibbingite (FeII, Mg)2(OH)3Cl(s), and Fe(OH)2(s) in 0.04 m to 6 m NaCl brines has been determined. For the reactionFe2(OH)3Cl(s) + 3H+ ? 3 H2O + 2 Fe2+ + Cl?,the solubility constant of Fe2(OH)3Cl(s) at infinite dilution and 25 °C has been found to be log10 K = 17.12 ± 0.15 (95% confidence interval using F statistics for 36 data points and 3 parameters). For the reactionFe(OH)2(s) + 2H+ ? 2 H2O + Fe2+,the solubility constant of Fe(OH)2 at infinite dilution and 25 °C has been found to be log10 K = 12.95 ± 0.13 (95 % confidence interval using F statistics for 36 data points and 3 parameters). For the combined set of solubility data for Fe2(OH)3Cl(s) and Fe(OH)2(s), the Na+–Fe2+ pair Pitzer interaction parameter θNa+/Fe2+ has been found to be 0.08 ± 0.03 (95% confidence interval using F statistics for 36 data points and 3 parameters). In nearly saturated NaCl brine we observed evidence for the conversion of Fe(OH)2(s) to Fe2(OH)3Cl(s). Additionally, when Fe2(OH)3Cl(s) was added to sodium sulfate brines, the formation of green rust(II) sulfate was observed, along with the generation of hydrogen gas. The results presented here provide insight into understanding and modeling the geochemistry and performance assessment of nuclear waste repositories in salt formations. 相似文献
617.
Khairayu Badron Ahmad Fadzil Ismail Jafri Din Abd.Rahman Tharek 《Journal of Atmospheric and Solar》2011,73(5-6):601-610
Satellite communications operating at 10 GHz and above in the tropics suffer severe signal degradation due to rain. Attenuation due to rain at 38 GHz had been measured for a period of 20 months in Malaysia. Analyses carried out include seasonal variations, diurnal effects and the annual cumulative distributions. Obtained results were compared with several established prediction models including the ITU-R. The rain fade characteristics were also investigated in determining the levels of signal loss and fading. In addition, the studies highlight several potential fade mitigation techniques that can be embarked. These fundamental aprehensions are very critical for future earth space communication link design and can be exploited as preliminary groundwork plan for the researchers as well as engineers. 相似文献
618.
Muhammad Umar Henrik Friis Abdul Salam Khan Akhtar Muhammad Kassi Aimal Khan Kasi 《Journal of Asian Earth Sciences》2011,40(2):622-635
The Maastrichtian Pab Formation in the southern part of Pakistan is composed of fine- to very coarse-grained texturally mature quartz arenite and subordinate sublitharenite varieties. The sandstones have undergone intense and complex diagenetic episodes due to burial and uplift. Diagenetic modifications were dependent mainly on the clastic composition of sandstone, burial depth and thrust tectonics. Diagenetic events identified include compaction, precipitation of calcite, quartz, clay minerals and iron oxide/hydroxide, dissolution and alteration of unstable clastic grains as feldspar and volcaniclithic fragments as well as tectonically induced grain fracturing. The unstable clastic grains like feldspar and lithic volcanic fragments suffered considerable alteration to kaolinite and chlorite. Dissolution and alteration of feldspar and volcanic lithic fragments and pressure solution were the main sources of quartz cements. Mechanical compaction and authigenic cements like calcite, quartz and iron oxide/hydroxide reduced the primary porosity, whereas dissolution of clastic grains and cements has produced secondary porosity. Chlorite coatings on clastic grains have prevented quartz cementation. Coarse-grained, thick bedded packages of fluviodeltaic, shelf delta lobe and submarine channels facies have higher average porosity than fine-grained, thin bedded and bioturbated sandstone of deeper shelf and abyssal plain environments and these facies are concluded to be possible future hydrocarbon prospects. 相似文献
619.
Geotechnical modeling of fractures and cavities that are associated with geotechnical engineering problems in Kuala Lumpur limestone,Malaysia 总被引:1,自引:0,他引:1
This study presents a modified geotechnical model of subsurface cavities and fractures that are associated with foundation
and pilling problems. The topographical model was used to automatically extract minimum surface curvature, slope, and pits.
The image processing shows that more than fourteen regional faults, trending NE, SW, and WNW affect the Kuala Lumpur limestone
bedrock and the surface topography from South to North. These fractures often show higher probability of piling and constructions
problems. The faults are tensional, low lying, and wrench of length 10–20 km. Opencast ex-mining pond floors (bathymetry)
are good indicators of subsurface fractures and cavities that affect the limestone bedrock. The LANDSAT image (band one) shows
that the fractures of opencast ex-mining pond floors have the same trend as the regional faults. These techniques can help
geotechnical engineers to predict subsurface fractures and cavities, especially in areas adjacent to ex-mining ponds. In brief,
most of the subsurface cavities and ex-mining ponds, for example the Phong Fatt pond, are located on and along fault zones. 相似文献
620.
The raw material soil of Al-Sowera factory quarry (quarry soil and mixture) used for building brick industry was tested mineralogically, geochemically and geotechnically. Mineral components of soil are characterized by Clay minerals (Palygoriskite and chlorite) and non-clay minerals like calcite, quratz, feldspar, gypsum and halite. The raw material is deficient in SiO2, Al2O3, K2O, Fe2O3 and MgO, while enriched in CaO. Loss on ignition and Na2O are in suitable level and appear to be concordant with the standard. Grain size analyses show that the decreasing sand and clay, and increasing silt ratio in both quarry soil and mixture caused decreasing in strength of brick during molding and after firing. The quarry soil is characterized by high plasticity clayey soil of 30.49 plastic index (P.I), whereas the mixture considered a clayey soil has a low plasticity of 7.7 plastic index (P.I). To improve the chemical and physical properties of the raw material, alumina-silicate minerals rich in K2O, Fe2O3 and MgO are recommended as additive materials to the main mixture. 相似文献