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71.
Søren Jessen Flemming Larsen Dieke Postma Pham Hung Viet Nguyen Thi Ha Pham Quy Nhan Dang Duc Nhan Mai Thanh Duc Nguyen Thi Minh Hue Trieu Duc Huy Tran Thi Luu Dang Hoang Ha Rasmus Jakobsen 《Applied Geochemistry》2008
To study the geological control on groundwater As concentrations in Red River delta, depth-specific groundwater sampling and geophysical logging in 11 monitoring wells was conducted along a 45 km transect across the southern and central part of the delta, and the literature on the Red River delta’s Quaternary geological development was reviewed. The water samples (n = 30) were analyzed for As, major ions, Fe2+, H2S, NH4, CH4, δ18O and δD, and the geophysical log suite included natural gamma-ray, formation and fluid electrical conductivity. The SW part of the transect intersects deposits of grey estuarine clays and deltaic sands in a 15–20 km wide and 50–60 m deep Holocene incised valley. The NE part of the transect consists of 60–120 m of Pleistocene yellowish alluvial deposits underneath 10–30 m of estuarine clay overlain by a 10–20 m veneer of Holocene sediments. The distribution of δ18O-values (range −12.2‰ to −6.3‰) and hydraulic head in the sample wells indicate that the estuarine clay units divide the flow system into an upper Holocene aquifer and a lower Pleistocene aquifer. The groundwater samples were all anoxic, and contained Fe2+ (0.03–2.0 mM), Mn (0.7–320 μM), SO4 (<2.1 μM–0.75 mM), H2S (<0.1–7.0 μM), NH4 (0.03–4.4 mM), and CH4 (0.08–14.5 mM). Generally, higher concentrations of NH4 and CH4 and low concentrations of SO4 were found in the SW part of the transect, dominated by Holocene deposits, while the opposite was the case for the NE part of the transect. The distribution of the groundwater As concentration (<0.013–11.7 μM; median 0.12 μM (9 μg/L)) is related to the distribution of NH4, CH4 and SO4. Low concentrations of As (?0.32 μM) were found in the Pleistocene aquifer, while the highest As concentrations were found in the Holocene aquifer. PHREEQC-2 speciation calculations indicated that Fe2+ and H2S concentrations are controlled by equilibrium for disordered mackinawite and precipitation of siderite. An elevated groundwater salinity (Cl range 0.19–65.1 mM) was observed in both aquifers, and dominated in the deep aquifer. A negative correlation between aqueous As and an estimate of reduced SO4 was observed, indicating that Fe sulphide precipitation poses a secondary control on the groundwater As concentration. 相似文献
72.
73.
Wei Chen Xiaowei Hong Riyu Lu Aifen Jin Shizhu Jin Jae-Cheol Nam Jin-Ho Shin Tae-Young Goo Baek-Jo Kim 《大气科学进展》2016,33(1):1-9
This study investigates the interannual variation of summer surface air temperature over Northeast Asia(NEA) and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are obtained by EOF analysis.The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode.This anomaly extends from southeast of Lake Baikal to Japan,with a central area in Northeast China.The second EOF mode is characterized by a seesaw pattern,showing a contrasting distribution between East Asia(specifically including the Changbai Mountains in Northeast China,Korea,and Japan) and north of this region.This mode is named the East Asia(EA) mode.Both modes contribute equivalently to the temperature variability in EA.The two leading modes are associated with different circulation anomalies.A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet.On the other hand,a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet.In addition,the NEA mode tends to be related to the Eurasian teleconnection pattern,while the EA mode is associated with the East Asia-Pacific/PacificJapan pattern. 相似文献
74.
Turbidites and their association with past earthquakes in the deep Çınarcık Basin of the Marmara Sea
Two gravity cores (CAG-3 and C-15) from the tectonically active, 1,276-m deep Çınarcık Basin of the Marmara Sea each include three sandy turbiditic mud units (1 mm–2 cm thick) with sharp basal contacts. The high benthic foraminifer content of these units suggests that the sediments were transported by turbidity currents from the upper slope region. These units represent the thin edges of turbidites thickening towards the subsiding north-eastern part of the basin, and contain quartz, detrital calcite, intact shells and shell fragments, smectite, pyrite framboids, muscovite, biotite, epidote and garnet. Their clay fractions are more enriched in smectite than those of adjacent layers. AMS 14C ages (957±43 a.d. and 578±31 a.d.) of two upper and middle turbiditic units in core C15 overlap with the historical İstanbul-Thrace (intensity=10) and İstanbul-Kocaeli (intensity=9) earthquakes of 26 October 986 and 15 August 553, respectively. This overlap, together with sedimentological characteristics, strongly suggests that the turbiditic units are related to the tectono-seismic activity of the North Anatolian Fault. The age of the lowest turbiditic unit in core C-3 was found to be 6,573±87 a b.p. (calendar) by AMS 14 C. In terms of chronostratigraphic relationships and lithological composition, the turbiditic units in core CAG-3 cannot be correlated with those in C15. This can be explained by gravity-controlled sedimentation causing wedging out of turbidites towards the edge of the basin. 相似文献
75.
GSTA is a major glutathione S-transferase gene responsible for 4-hydroxynonenal conjugation in largemouth bass liver 总被引:2,自引:0,他引:2
We have previously shown that largemouth bass (Micropterus salmoides) has a remarkable ability to conjugate 4-hydroxy-2-nonenal (4HNE), a mutagenic and cytotoxic alpha,beta-unsaturated aldehyde produced during the peroxidation of lipids. In addition, we have isolated a glutathione S-transferase cDNA (bass GSTA) that encodes a recombinant protein which is highly active in 4HNE conjugation and structurally similar to plaice (Pleuronectes platessa) GSTA. In the present study, HPLC-GST subunit analysis revealed the presence of at least two major GST isoforms in bass liver, with one peak constituting 80% of the total bass liver GST protein. Liquid chromatography mass spectrometry (LC-MS) and electrospray ionization analysis of the major bass GST subunit yielded a molecular weight of 26,396 kDa. Endo-proteinase Lys-C digestion and Edman degradation protein sequencing of this GST peak demonstrated that this protein was encoded by bass GSTA. Analysis of genomic DNA fragments isolated by nested PCR indicated the presence of a GST gene cluster in bass liver that contained GSTA, and was similar to a GST gene cluster characterized by Leaver et al., in plaice. Collectively, our data indicates the presence of a major GST in bass liver involved in the protection against oxidative stress. This GST is part of a gene cluster that may be conserved in certain freshwater and marine fish. 相似文献
76.
77.
To supplement conventional geophysical log data, this study presents temporal variations in electrical conductivity (EC) and temperature with depth in a multilayered coastal aquifer, on the eastern part of Jeju Island, Korea. One‐month time‐series data obtained at eight points from a multi‐depth monitoring system showed that semidiurnal and semimonthly tidal variations induced dynamic fluctuations in EC and temperature. At some depths, EC ranged from 1483 to 26 822 µS cm?1, while some points showed no significant variations. The results of EC log and time‐series data revealed that a sharp fresh‐saltwater interface occurred at low tide, but the diffusion zone broadened to 20 m at high tide. EC, temperature, and tide level data were used for the cross‐correlation analysis. The response time of EC and temperature to tide appears to range from less than 30 min to 11 h. Using end‐member mixing analysis (EMMA), the fraction of variations of chloride concentration in the multilayered aquifer was explained, and a conceptual model was developed which subdivided the coastal aquifer into four vertical zones. The percentage of water derived from seawater varied from 2 to 48 at specific depth, owing to tidal fluctuations. Continuous observations of EC and temperature at multiple depths are powerful tools for quantifying the transport of saline water by tidal variations in multilayered coastal aquifers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
78.
The investigation of a limestone cave on the Ryonggok-ri of Sangwon County, North Hwanghae Province, DPRK, has yielded many faunal remains including Late Pleistocene deer, brown bears and horses. Uranium series dating of fossil teeth yielded dates of ~72ka at the base of Layer 2 – the bone-bearing unit – and ~44ka at the top. The rich and diverse mammal remains of Ryonggok Cave No. 1 are indicative of warm and humid temperate conditions during the Late Pleistocene, and reflect the presence of both dense forests and open grassland. In addition, pollen and spores from the site include two families and 24 genera of trees, six families and a genus of grasses and herbs, and two families and six genera of ferns, corroborating the environments inferred from the faunal remains. 相似文献
79.
Thanh Duc Dang Thomas A. Cochrane Mauricio E. Arias Pham Dang Tri Van Tonny T. de Vries 《水文研究》2016,30(21):3824-3838
The Mekong floodplains, which encompasses the region from Kratie Township in Central Cambodia to the Vietnamese East Sea, is a region of globally renown agricultural productivity and biodiversity. The construction of 135 dams across the Mekong basin and the development of delta‐based flood prevention systems have caused public concern given possible threats on the stability of agricultural and ecological systems in the floodplains. Mekong dams store water upstream and regulate flow seasonality, while in situ flood prevention systems re‐distribute water retention capacity in the floodplains. The main aim of this paper is to evaluate possible impacts of the recent development of both hydropower dams and flood prevention systems on hydrological regimes in the Mekong floodplains. An analysis of measured daily and hourly water level data for key stations in the Mekong floodplains from Kratie to the river mouth in Vietnam was conducted. Hydropower dam information was obtained from the hydropower database managed by the Mekong River Commission, and the MODIS satellite imagery was used to detect changes in flooding extent related to the operation of flood prevention systems in the Vietnam Mekong Delta. Results indicate that the upper part of the floodplains, the Cambodian floodplains, may buffer upstream dam impacts to the Vietnam Mekong Delta. Flood prevention up to date has had the greatest effect on the natural hydrological regime of the Mekong floodplains, evidenced by a significant increase of water level rise and fall rates in the upper delta and causing water levels in the middle delta to increase. The development of flood prevention systems has also effected spatial distribution of flooding as indicated via a time series analysis of satellite imagery. While this development leads to increase localized agricultural productivity, our historical data analysis indicates that development of one region detrimentally affects other regions within the delta, which could increase the risk of future conflicts among regions, economic sectors and the ecological value of these important floodplains. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
80.
Namık Aysal Marcel Guillong Tamara Bayanova Mayuko Fukuyama Nicole Leonard İsak Yılmaz Elif Varol Fatma Şişman Tükel Yusuf Kaan Kadıoğlu Nurullah Hanilçi Fulya Uzun Ersin Kaygısız 《Geostandards and Geoanalytical Research》2023,47(2):297-310
Gem quality andradite-rich garnet (IUC-1), obtained from the Miocene trachyte dome near Ankara city (Turkey), has been identified as a potential natural secondary reference material for U-Pb dating. In this study, U-Pb dating was performed in five different laboratories using isotope dilution TIMS and laser ablation ICP-MS to determine the homogeneity of euhedral garnet crystals. The U-Pb ID-TIMS data for IUC-1 yielded 207Pb/235U and 206Pb/238U ages of 20.9 ± 0.4 and 20.6 ± 0.8 Ma respectively, and these values are consistent with U-Pb LA-ICP-MS analyses, in which different garnet crystals yielded ages of 20.8 ± 0.1, 20.7 ± 0.1, 20.7 ± 0.2 and 20.2 ± 0.1 Ma. An andradite (IUC-2) from the Serçeören wollastonite skarn (Turkey) can be used as a secondary reference material provided detailed imaging of the crystals is undertaken. ID-TIMS data yielded 207Pb/235U and 206Pb/238U ages of 20.4 ± 0.4 and 20.9 ± 1.0 Ma respectively, and yielded U-Pb ages on different grains of 20.5 ± 0.1, 20.7 ± 1.0, 20.8 ± 1.7 and 20.9 ± 1.6 Ma. The assigned weighted mean age of IUC-1 (20.4 ± 0.5 Ma, 2s) is proposed as a 2023 reference value. IUC-1 garnet is expected to contribute significantly to rapidly developing garnet geochronology in the near future. 相似文献