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31.
The Al-Batin alluvial fan covers a broad area of southern Iraq. It was the main battlefield of two devastating wars in 1991 and 2003, during which huge amounts of depleted uranium (DU) were used. This study aims to assess the geochemistry of this fan sediment including the potential effects of the DU used. Sixty-three samples were collected from sediments including three samples from sediments under tanks attacked by DU ammunition. Major elements were measured by XRF (fusion bead method), whereas ICP-MS was used to measure the trace elements. The results suggest that the most dominant major minerals are in the order of: quartz?>?secondary gypsum?>?calcite?>?feldspar, clay minerals?>?iron oxide, and show abnormal concentrations of Sr, Cr, Ni, and V. This study also determined an area with high concentration of U in the north east part of the fan. Statistical analysis and spatial distribution of important elements suggests that two major factors affect mineral formation. The first factor reflects the influence of minerals in the source area of the sediments (Arabian Shield): quartz, carbonate, clay minerals, feldspars, as well as iron oxides and elevated concentrations of V, Ni, and Cr. The second factor points at authigenic formation of secondary gypsum and celestite and elevated U concentration under the control of a hot arid climate and the specific groundwater situation. However, the origin of the sediments is geogenic, while the anthropogenic impact seems to be minor. Spatial distribution of U and the 235/238U ratio did not show any peaks in the places where tanks have been destroyed. This is contrary to media speculations and some scientific reports about the permanent risks of DU in the area, which creates public concern about the potential risk of living in this area. 相似文献
32.
In presence of disinfectants, PAH are remobilized from the coal tar lining of water distribution mains. Reactions of the PAH with chlorine and chlorine dioxide can lead to chlorinated PAH that might show higher mutagenic effects than the parent PAH. The application of the solid-phase microextraction as a sampling preparation method in combination with a gas chromatographic mass spectrometric device is a reliable and useful method to achieve detection limits in the lower nanogramme-per-liter level for PAH and chlorinated PAH. Thus, the reactions of four PAH (anthracene, fluoranthene, fluorene, and phenanthrene) with chlorine and chlorine dioxide under conditions prevalent in drinking water distribution systems could be investigated. In batch experiments with demineralized and drinking water at pH 7, the concentrations of fluoranthene, fluorene, and phenanthrene remained constant, whereas anthracene reacted quantitatively with both disinfectants. In these reactions, no chlorinated products could be detected, only mono-hydroxyanthracene and anthraquinone were formed. A reaction mechanism for both reaction products is proposed. The results suggest that oxidation is the major pathway of the reaction of PAH with disinfectants in the systems under investigation. 相似文献
33.
S. Merkel A. P. Jephcoat J. Shu H.-K. Mao P. Gillet R. J. Hemley 《Physics and Chemistry of Minerals》2002,29(1):1-9
Physical properties including the equation of state, elasticity, and shear strength of pyrite have been measured by a series
of X-ray diffraction in diamond-anvil cells at pressures up to 50 GPa. A Birch–Murnaghan equation of state fit to the quasihydrostatic
pressure–volume data obtained from laboratory X-ray source/film techniques yields a quasihydrostatic bulk modulus K
0T
=133.5 (±5.2) GPa and bulk modulus first pressure derivative K
′
0T
=5.73 (±0.58). The apparent equation of state is found to be strongly dependent on the stress conditions in the sample. The
stress dependency of the high-pressure properties is examined with anisotropic elasticity theory from subsequent measurements
of energy-dispersive radial diffraction experiments in the diamond-anvil cell. The calculated values of K
0T
depend largely upon the angle ψ between the diffracting plane normal and the maximum stress axis. The uniaxial stress component
in the sample, t=σ3−σ1, varies with pressure as t=−3.11+0.43P between 10 and 30 GPa. The pressure derivatives of the elastic moduli dC
11/dP=5.76 (±0.15), dC
12/dP=1.41 (±0.11) and dC
44/dP=1.92 (±0.06) are obtained from the diffraction data assuming previously reported zero-pressure ultrasonic data (C
11=382 GPa, C
12=31 GPa, and C
44=109 GPa).
Received: 21 December 2000 / Accepted: 11 July 2001 相似文献
34.
Ahmed Abdulameer Jassim M. Thabit Firas H. AL-Menshed Broder Merkel 《Environmental Earth Sciences》2018,77(17):619
Electrical resistivity surveying for delineating seawater intrusion was performed in the Dibdibba aquifer in the area between the cities of Al-Zubair–Safwan and Al-Zubair–Umm Qasr in the vicinity of Khor AL-Zubair Channel, Basrah governorate, southern Iraq. Fourteen 2D resistivity profiles with a total length of 14 km were collected in the study area. The resistivity sections were compared with lithological data extracted from 11 boreholes. Thirty-nine groundwater samples were collected within the area and analyzed for chemical constituents; internal hydrogeological reports and unpublished studies were also evaluated. Results reveal the existence of three major resistivity layers, ranging from 0.1 to 130 Ωm at various depths and locations. The first layer has very low electrical resistivity (0.1–5 Ωm) representing a layer saturated with saltwater intruded from Khor AL-Zubair Channel. The second layer shows resistivity in the range of 5–130 Ωm, attributed to a transition zone and an unaffected zone saturated with brackish groundwater. The last resistivity layer (<?3 Ωm) represents coarse-grain sediments saturated with saline groundwater. Furthermore, a hard clay bed (Jojab) appears with a resistivity of 3–7 Ωm in all 2D imaging lines within a depth of 20–28 m. Electrical conductivity (EC) measurements from seven wells collected in 2014 and 2016 show a positive EC difference increasing landward with an average increase of 1927 µS/cm. In addition, six chemical relationships (Na/Cl, [Ca?+?Mg]/[HCO3?+?SO4], SO4/HCO3, SO4/Cl, Mg/Ca and Cl/[HCO3?+?CO3]) are used to detect the source of salinity in groundwater. This study proves that extensive use of high-resolution 2D imaging sections, alongside lithological and hydrogeological data, can serve as a useful tool to delineate the boundaries between aquifers, identify hydraulic boundaries between groundwater with different salinities and allocate hard clay layers between the upper and lower Dibdibba aquifer. In general, the combination of 2D imaging and hydrochemistry enables conceptualization of the hydrogeological situation in the subsurface and characterization of the salinity source, here seawater intrusion, in the study area. There have been no studies published so far on the characteristics of saltwater intrusion in the study area, and this study is considered to be important for monitoring and studying the intrusion and regression of seawater. 相似文献
35.
Mehdi Zarei Ezzat Raeisi Broder J. Merkel Nicolai-Alexeji Kummer 《Environmental Earth Sciences》2013,70(2):587-604
Konarsiah salt diapir is situated in the Simply Folded Zone of the Zagros Mountain, south Iran. Eight small permanent brine springs emerge from the Konarsiah salt body, with average total dissolved solids of 326.7 g/L. There are numerous brackish to saline springs emerging from the alluvial and karst aquifers adjacent to the diapir. Concerning emergence of Konarsiah diapir in the study area, halite dissolution is the most probable source of salinity in the adjacent aquifers. However, other sources including evaporation and deep brines through deep Mangerak Fault are possible. The water samples of the study area were classified based on their water-type, salinity, and the trend of the ions concentration curves. The result of this classification is in agreement with the hydrogeological setting of the study area. The hydrochemical and isotopic evaluations show that the groundwater samples are the result of mixing of four end members; Gachsaran sulfate water, Sarvak and Asmari carbonate fresh waters, and diapir brine. The molar ratios of Na/Cl, Li/Cl, Br/Cl, and SO4/Cl; and isotopic signature of the mixed samples justify a groundwater mixing model for the aquifers adjacent to the salt diapir. The share of brine in each adjacent aquifer was calculated using Cl mass balance. In addition, concentrations of 34 trace elements were determined to characterize the diapir brine and to identify the possible tracers of salinity sources in the mixed water samples. B, Mn, Rb, Sr, Cs, Tl, and Te were identified as trace elements evidencing contact of groundwater with the salt diapir. 相似文献
36.
Trace element hydrochemical assessment of the Calabar Coastal Plain Aquifer,southeastern Nigeria using statistical methods 总被引:2,自引:0,他引:2
Groundwater samples from 33 locations within the Coastal Plain Sands aquifer of Calabar (Nigeria) were collected and analysed for 43 trace elements by means of ICP-MS. The aim of this study is to determine the natural background levels of trace elements as a guide for future pollution monitoring of the aquifer. Secondly, this article focuses on the pollution vulnerability of the coastal plain sand aquifer. Statistical methods have been used to determine the source(s) of these elements. Results show that the area is characterised by four types of groundwater, including: Na-HCO3, Na-HCO3-Cl, Na-Cl and Ca-Na-HCO3-Cl. Secondly, all the elements considered are below normal averages. In addition, the Spearman correlation shows significant correlation especially among the lanthanide group of elements (p<0.0001). Factors analyses indicate mainly two groups of elements. The first group being due to the natural geochemical process (weathering/leaching of the basement lithology; characteristics of the elements) and the second is due to tidal flushing of the estuary. This indicates that the source of the trace element in the aquifer is due to a geogenic process and not anthropogenic. Thus, the present data set will serve as a reference source for pollution monitoring in the area. 相似文献
37.
Soil erosion by water is one of the most widespread forms of soil degradation in Europe. There are many undesirable consequences of soil erosion due to water such as loss of water storage capacity in reservoirs and transfer of pollutants from farmland to water bodies. The objectives of this study were to calibrate and validate the Water Erosion Prediction Project watershed model (WEPP 2012.8) in the Bautzen dam catchment area with monthly and daily single events for runoff and sediment yield. This is to our knowledge the first study using WEPP in Germany. The catchment (310 km2) was subdivided into small sub-catchments with an area of <260 ha as recommended in WEPP. A sensitivity analysis revealed that the runoff is highly sensitive to the effective hydraulic conductivity in Bautzen, whereas the sediment yield is highly sensitive to rill erodibility, critical shear stress, and to the effective hydraulic conductivity as well. All these parameters were initially calculated using WEPP’s built-in equations and parameters, which, however, produced very poor results for both runoff and sediment yield. Therefore, the model was calibrated for 2 years (2005–2007) and validated for another 2 years (2008–2009) against monthly measurements, in addition to 14 daily single events from the calibration period and 2010. The monthly results were compared with the monthly measurements on the basis of a continuous simulation. Results of calibration and validation periods show a satisfactory performance of WEPP with a determination coefficient R 2 above 0.6 and Nash–Sutcliffe efficiency coefficients above 0.50 for runoff and sediment yield. Thus, the model could be used to simulate runoff and sediment yield, and used in scenario studies in the Bautzen dam catchment area. 相似文献
38.
Impact of Alkaline Earth Metals on Aqueous Speciation of Uranium(VI) and Sorption on Quartz 总被引:2,自引:0,他引:2
The effect of Mg-, Ca-, and Sr–Uranyl-Carbonato complexes with respect to sorption on quartz was studied by means of batch
experiments with U(VI) concentration of 0.126 × 10−6 M in the presence and absence of Mg, Ca, and Sr (each 1 mM) at pH from 6.5 to 9. In the absence of alkaline earth elements,
90% of the U(VI) sorbed on the quartz surface at all pH. In the presence of Mg, Ca, and Sr, the sorption of U(VI) on quartz
decreased to 50, 10, and 30%, respectively. Sorption kinetics of U(VI) on quartz is faster in the absence of alkaline earth
elements and reached equilibrium after 12 h, whereas in the presence of Mg, Ca and Sr, the kinetics of U(VI) sorption on quartz
is pH dependent and attained equilibrium after 24 h. Aqueous speciation calculations for alkaline earth uranyl carbonates
were carried out by using PHREEQC with the Nuclear Energy Agency thermodynamic database (NEA_2007) by adding constants for
MUO2(CO3)32− and M2UO2(CO3)30 (M = Ca, Mg, Sr). This study reveals that alkaline earth elements can have a significant effect on the aqueous speciation
of U(VI) under neutral to alkaline pH conditions and subsequently sorption behavior and mobility of U(VI) in aqueous environments. 相似文献
39.
40.
Parke A. Rublee Susan M. Merkel Maria A. Faust 《Estuarine, Coastal and Shelf Science》1983,16(5):501-509
The number of bacteria in sediments, interstitial water and overlying tidal water of an oligohaline marsh system are about 109, 106 and 106 cells cm?3, respectively. Average cell size in the overlying water (about 0·06 μm3), is much smaller than that in sediments and interstitial water (about 0·18 μm3). Most bacterial cells in sediments are bound to sediment particles and less than 1% of the cells were displaced by percolating water through sediment columns. Concentration of bacteria in flooding tidal waters is generally higher than that in ebbing waters. Movement of bacterial biomass does not appear to be a significant mechanism of particulate organic transport in marsh sediments and marsh sediments do not appear to be a source of suspended bacteria for estuaries. 相似文献