The response of playa and sabkha hydraulics and mineralogy to climate forcing   总被引：1，自引：0，他引：1  

Tyler SW  Muñoz JF  Wood WW 《Ground water》2006,44(3):329-338

Dry playa lakes and sabkhat often represent the terminus of large ground water flow systems and act as integrators of both upgradient (recharge) and downgradient discharge (evaporation). Ground water levels beneath playa/sabkha systems show a variety of surprising responses driven by large evaporation demands and chemical processes not typically encountered in more humid regions. When the water table is very close to the land surface, almost instantaneous rises can be observed with little observed change in either upgradient ground water recharge or potential evaporation. Conversely, when water tables are several meters below the playa surface, water table responses to interannual variability of recharge can be damped and lag significantly behind such changes. This review of the dynamics of shallow water tables in playa lakes and sabkhat discusses the pertinent hydraulic and solute processes and extracts a simple but comprehensive model based on soil physics for predicting the water table response to either upstream recharge changes or changes in potential evaporation at the playa/sabkha. Solutes and associated authigenic minerals are also shown to be important in discriminating both the causes and effects of water level fluctuations.  相似文献   

Perfluorinated alkyl acids in water, sediment and wildlife from Sydney Harbour and surroundings     

Thompson J  Roach A  Eaglesham G  Bartkow ME  Edge K  Mueller JF 《Marine pollution bulletin》2011,62(12):2869-2875

Perfluorinated alkyl compounds (PFCs) including perfluorooctane sulphonate (PFOS) and perfluorooctanoate (PFOA) were measured in environmental samples collected from around Homebush Bay, an urban/industrial area in the upper reaches of Sydney Harbour and Parramatta River estuary. Water, surface sediment, Sea Mullet (Mugil cephalus), Sydney Rock Oyster (Saccostrea commercialis) and eggs of two bird species; White Ibis (Threskiornis molucca), and Silver Gull (Larus novaehollandiae) were analysed. In most samples PFOS was the dominant PFC. Geometric mean PFOS concentrations were 33 ng/g ww (wet weight) in gull eggs, 34 ng/g ww in ibis eggs, and 1.8 ng/g ww and 66 ng/g ww in Sea Mullet muscle and liver, respectively. In sediment the PFOS geometric mean was 1.5 ng/g, in water average PFOS and PFOA concentrations ranged from 7.5 to 21 ng/L and 4.2 to 6.4 ng/L, respectively. In oysters perfluorododecanoic acid was most abundant, with a geometric mean of 2.5 ng/g ww.  相似文献   

Spectroscopy of Mars from 2.04 to 2.44 micrometers during the 1993 opposition: absolute calibration and atmospheric vs mineralogic origin of narrow absorption features     

Bell JF rd  Pollack JB  Geballe TR  Cruikshank DP  Freedman R 《Icarus》1994,111(1):106-123

We present moderate-resolution (lambda/delta lambda = 300 to 370) reflectance spectra of Mars from 2.04 to 2.44 micrometers that were obtained at UKIRT during the 1993 opposition. Seven narrow absorption features were detected and found to have a Mars origin. By comparison with solar and Mars atmospheric spectra, five of these features were attributed all or in part to Mars atmospheric CO2 or CO(2.052 +/- 0.003, 2.114 +/- 0.002, 2.150 +/- 0.003, 2.331 +/- 0.001, and 2.357 +/- 0.002 micrometers). Two of the bands (2.331 +/- 0.001 and 2.357 +/- 0.002 micrometers) appear to have widths and depths that are consistent with additional, nonatmospheric absorptions, although a solar contribution cannot be entirely ruled out. Two other weak bands centered at 2.278 +/- 0.002 and 2.296 +/- 0.002 micrometers may be at least partially mineralogic in origin. The data provide no conclusive identification of the mineralogy responsible for these absorption features. However, examination of terrestrial spectral libraries and previous moderate spectral resolution mineral studies indicates that the most likely origin of these features is either (bi)carbonate or (bi)sulfate anions in framework silicates or (Fe, Mg)-OH bonds in sheet silicates. If the bands are caused by phyllosilicate minerals, then an explanation must be found for the extremely narrow widths of the cation-OH features in the Mars spectra as compared to terrestrial minerals.  相似文献   

拉柯斯特重力仪在微重力测量中野外观测技术的改进     

Thim.  JF 吴朝钧 《地质科学译丛》1989,(1):95-97

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安大略湖上的航空重力测试     

Halp.  JF 王红方 《物探化探译丛》1996,(6):14-19

１９９１年３月在安大略湖上进行了航空重力测试，其目的是籽验证用轻型飞机进行快速经济的航空重力测量的可能性。重力仪选用的是ＬａＣｏｓｔｅ ＆Ｒｏｍｂｅｒｇ公司的线性动态重力仪。用ＰＣ计算机作为数字控制器，测量飞机为Ｐｉｐｅｒ Ｎａｖａｊｏ双引擎飞机，Ｔｒｉｍｂｌｅ ４０００型ＧＰＳ接收机连同就近的ＧＰＳ地面基站进行差分动态定位，得到了精确的导定位数据，测出了以前水下重力测量圈定的安大略湖东部主要的低  相似文献   

Microbes all around     

Skinner HC  Banfield JF 《Geotimes》1997,42(8):16-19

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Use of the Comet assay to assess DNA damage in hemocytes and digestive gland cells of mussels and clams exposed to water contaminated with petroleum hydrocarbons   总被引：2，自引：0，他引：2  

Hamouten D  Payne JF  Rahimtula A  Lee K 《Marine environmental research》2002,54(3-5):471-474

Oil spills can result in the deposition of large quantities of petroleum hydrocarbons into intertidal and shallow waters seriously impacting bivalve populations. Petroleum hydrocarbons are enriched in polycyclic aromatic hydrocarbons (PAH) and PAH analogs many of which may have potential to damage DNA. The Comet assay is useful for assessing DNA damage and has been used to a limited degree with aquatic organisms, but mostly with studies in vitro. We have carried out studies with the Comet assay to assess the DNA damaging potential of complex mixtures of petroleum hydrocarbons for bivalves. Experiments were carried out with mussels (Mytilus edulis) and clams (Mya arenaria) with dispersions and water soluble fractions of an Arabian crude oil which was also chemically characterized in detail by GC-MS. Pilot studies were first conducted to evaluate test performance and reproducibility. An interindividual coefficient of variation ranging from 17 to 30% was established for the assay with hemocytes and digestive gland cells of both species. Exposure to hydrocarbon fractions had no significant impact on clams. However, an increase in DNA damage was observed at P < 0.1 with digestive gland cells of mussels exposed to aqueous fractions of a light crude oil. These studies have demonstrated a potential for DNA damage in bivalves exposed to oil spills in inshore waters as well as potential for interspecies sensitivity.  相似文献   

The water quality of the Ria de Aveiro lagoon, Portugal: from the observations to the implementation of a numerical model   总被引：1，自引：0，他引：1  

Lopes JF  Dias JM  Cardoso AC  Silva CI 《Marine environmental research》2005,60(5):594-628

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法国气象局的业务半球模式     

J.COIFFIER  Y.ERNIE  JF.GELEYN  J.CLOCHARD  F.DUPONT  季晓阳 《海洋预报》1988,(Z1)

一、引言 自1985年初以来,一个新的半球谱模式已在法国气象局的CRAY—Ⅰ计算机上业务化运行了。这个模式的目标是提供直到4天的准确的预报产品。尽管这个模式已经完成了它的任务,但还有几个问题必须逐步解决;热带附近的预报场和分析场之间的误差,由于变量从分析高度到模式高度来回插值引起的初始震荡以及在物理过程参数化中出现的缺陷,有关修改已在模式中采用并证明是有效的。这项工作很容易用纬向平均诊断的方法来做。这种诊断对于指出模式的缺陷和检验它们的订正是有用的工具。  相似文献   

Stable isotope laser spectrometer for exploration of Mars     

Sauke TB  Becker JF 《Planetary and Space Science》1998,46(6-7):805-812

On Earth, measurements of the ratios of stable carbon isotopes have provided much information about geological and biological processes. For example, fractionation of carbon occurs in biotic processes and the retention of a distinctive 2-4% contrast in 13C/12C between organic carbon and carbonates in rocks as old as 3.8 billion years constitutes some of the firmest evidence for the antiquity of life on the Earth. We have developed a prototype tunable diode Laser spectrometer which demonstrates the feasibility of making accurate in situ isotopic ratio measurements on Mars. This miniaturized instrument, with an optical path length of 10 cm, should be capable of making accurate 13C/12C and 15N/14N measurements. Gas samples for measurement are to be produced by pyrolysis using soil samples as small as 50 mg. Measurements of 13C/12C, 18O/16O and 15N/14N have been made to a precision of better than 0.1% and various other isotopes are feasible. This laser technique, which relies on the extremely narrow emission linewidth of tunable diode lasers (<0.001 cm(-1)) has favorable features in comparison to mass spectrometry, the standard method of accurate isotopic ratio measurement. The miniature instrument could be ready to deploy on the 2003 or other Mars lander missions.  相似文献