Geochemical evolution of uraniferous soda lakes in Eastern Mongolia   总被引：1，自引：1，他引：0  

Benjamin S. Linhoff  Philip C. Bennett  Tamir Puntsag  Ochir Gerel 《Environmental Earth Sciences》2011,62(1):171-183

Extremely high concentrations of uranium (U) were discovered in shallow, groundwater-fed hyperalkaline soda lakes in Eastern Mongolia. A representative groundwater sample in this area is dilute and alkaline, pH = 7.9, with 10 mM TIC and 5 mM Cl⁻. In contrast, a representative lake water sample is pH ~ 10 with TIC and Cl⁻ each more than 1,000 mM. Groundwater concentrations of U range from 0.03 to 0.43 μM L⁻¹. Lake water U ranges from 0.24 to >62.5 μM, possibly the highest naturally occurring U concentrations ever reported in surface water. Strontium isotopes ⁸⁷Sr/⁸⁶Sr varied in groundwaters from 0.706192 to 0.709776 and in lakes ⁸⁷Sr/⁸⁶Sr varied from 0.708702 to 0.709432. High concentrations of U, Na, Cl⁻, and K correlate to radiogenic Sr in lake waters suggesting that U is sourced from local Cretaceous alkaline rhyolites. Uranium-rich groundwaters are concentrated by evaporation and U(VI) is chelated by CO₃⁻² to form the highly soluble UO₂(CO₃)₃⁻⁴. Modeled evaporation of lakes suggests that a U-mineral phase is likely to precipitate during evaporation.  相似文献   

Application of primary haemocyte culture of Penaeus monodon in the assessment of cytotoxicity and genotoxicity of heavy metals and pesticides   总被引：1，自引：0，他引：1  

Jose S  Jayesh P  Mohandas A  Philip R  Bright Singh IS 《Marine environmental research》2011,71(3):169-177

Lack of shrimp cell lines has hindered the study of pollutants which adversely affects shrimp health and its export value. In this context a primary haemocyte culture developed from Penaeus monodon was employed for assessing the cytotoxicity and genotoxicity of two heavy metal compounds, cadmium chloride and mercuric chloride and two organophosphate insecticides, malathion and monocrotophos. Using MTT assay 12?h IC(50) values calculated were 31.09?±?16.27?μM and 5.52?±?1.16?μM for cadmium chloride and mercuric chloride and 59.94?±?52.30?mg?l(-1) and 186.76?±?77.00?mg?l(-1) for malathion and monocrotophos respectively. Employing Comet assay, DNA damage inflicted by these pollutants on haemocytes were evaluated and the pollutants induced DNA damage in >60% of the cells. The study suggested that haemocyte culture could be used as a tool for quantifying cytotoxicity and genotoxicity of aquaculture drugs, management chemicals and pollutants.  相似文献   

An explicit finite difference model for simulating weakly nonlinear and weakly dispersive waves over slowly varying water depth   总被引：2，自引：0，他引：2  

Xiaoming Wang  Philip L.-F. Liu 《Coastal Engineering》2011

In this paper, a modified leap-frog finite difference (FD) scheme is developed to solve Non linear Shallow Water Equations (NSWE). By adjusting the FD mesh system and modifying the leap-frog algorithm, numerical dispersion is manipulated to mimic physical frequency dispersion for water wave propagation. The resulting numerical scheme is suitable for weakly nonlinear and weakly dispersive waves propagating over a slowly varying water depth. Numerical studies demonstrate that the results of the new numerical scheme agree well with those obtained by directly solving Boussinesq-type models for both long distance propagation, shoaling and re-fraction over a slowly varying bathymetry. Most importantly, the new algorithm is much more computationally efficient than existing Boussinesq-type models, making it an excellent alternative tool for simulating tsunami waves when the frequency dispersion needs to be considered.  相似文献   

Geostandards and Geoanalytical Research Bibliographic Review 2013     

Klaus Peter Jochum  Uwe Nohl  Beate Schwager  Brigitte Stoll  Philip Suesser  Ulrike Weis 《Geostandards and Geoanalytical Research》2014,38(4):513-515

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Investigation of the Stable Atmospheric Boundary Layer at Halley Antarctica   总被引：2，自引：2，他引：0  

Javier Sanz Rodrigo  Philip S. Anderson 《Boundary-Layer Meteorology》2013,148(3):517-539

Boundary-layer measurements from the Brunt Ice Shelf, Antarctica are analyzed to determine flux–profile relationships. Dimensionless quantities are derived in the standard approach from estimates of wind shear, potential temperature gradient, Richardson number, eddy diffusivities for momentum and heat, Prandtl number, mixing length and turbulent kinetic energy. Nieuwstadt local scaling theory for the stable atmospheric boundary-layer appears to work well departing only slightly from expressions found in mid-latitudes. An $E$ E – $l_{\mathrm{m}}$ l m single-column model of the stable boundary layer is implemented based on local scaling arguments. Simulations based on the first GEWEX Atmospheric Boundary-Layer Study case study are validated against ensemble-averaged profiles for various stability classes. A stability-dependent function of the dimensionless turbulent kinetic energy allows a better fit to the ensemble profiles.  相似文献   

What is at stake for Brazilian Amazonia in the climate negotiations     

Philip M. Fearnside 《Climatic change》2013,118(3-4):509-519

Issues left undecided at COP-18 in Doha in December 2012 are critical to containing the two greatest threats to Brazil’s Amazon forest: direct deforestation and forest loss through drought and fire provoked by climate change. Brazil’s diplomatic positions on the role of tropical forests in mitigating global warming currently call for receiving donations through a voluntary fund, but without generating carbon credit valid against emissions-reduction commitments by countries that accept limits on their national emissions (i.e., Annex I countries). Brazil has long rejected accepting a target (assigned amount), and has instead presented a non-binding “voluntary objective.” At COP-17 in Durban, Brazil expressed willingness to accept a commitment after 2020, but only if all of the rest of the world agreed to do the same. This author argues that Brazil’s national interests would be better served by accepting a target now and by supporting fully marketable carbon credit from Reducing Emissions from Deforestation and Degradation (REDD). The global goal of preventing mean temperature from increasing beyond 2 °C above pre-industrial levels would be much more likely to be achieved in practice with tropical forests fully included in a carbon market as part of an agreement for the period after 2012.  相似文献   

Diagnosis and testing of low-level cloud parameterizations for the NCEP/GFS model using satellite and ground-based measurements     

Hyelim Yoo  Zhanqing Li  Yu-Tai Hou  Steve Lord  Fuzhong Weng  Howard W. Barker 《Climate Dynamics》2013,41(5-6):1595-1613

The objective of this study is to investigate the quality of clouds simulated by the National Centers for Environmental Prediction global forecast system (GFS) model and to examine the causes for some systematic errors seen in the simulations through use of satellite and ground-based measurements. In general, clouds simulated by the GFS model had similar spatial patterns and seasonal trends as those retrieved from passive and active satellite sensors, but large systematic biases exist for certain cloud regimes especially underestimation of low-level marine stratocumulus clouds in the eastern Pacific and Atlantic oceans. This led to the overestimation (underestimation) of outgoing longwave (shortwave) fluxes at the top-of-atmosphere. While temperature profiles from the GFS model were comparable to those obtained from different observational sources, the GFS model overestimated the relative humidity field in the upper and lower troposphere. The cloud condensed water mixing ratio, which is a key input variable in the current GFS cloud scheme, was largely underestimated due presumably to excessive removal of cloud condensate water through strong turbulent diffusion and/or an improper boundary layer scheme. To circumvent the problem associated with modeled cloud mixing ratios, we tested an alternative cloud parameterization scheme that requires inputs of atmospheric dynamic and thermodynamic variables. Much closer agreements were reached in cloud amounts, especially for marine stratocumulus clouds. We also evaluate the impact of cloud overlap on cloud fraction by applying a linear combination of maximum and random overlap assumptions with a de-correlation length determined from satellite products. Significantly better improvements were found for high-level clouds than for low-level clouds, due to differences in the dominant cloud geometry between these two distinct cloud types.  相似文献   

A high-pressure neutron diffraction study of the ferroelastic phase transition in RbCaF3     

Kevin S. Knight  William G. Marshall  Philip M. Hawkins 《Physics and Chemistry of Minerals》2014,41(6):461-472

The fluoroperovskite phase RbCaF₃ has been investigated using high-pressure neutron powder diffraction in the pressure range ~0–7.9 GPa at room temperature. It has been found to undergo a first-order high-pressure structural phase transition at ~2.8 GPa from the cubic aristotype phase to a hettotype phase in the tetragonal space group I4/mcm. This transition, which also occurs at ~200 K at ambient pressure, is characterised by a linear phase boundary and a Clapeyron slope of 2.96 × 10^?5 GPa K^?1, which is in excellent agreement with earlier, low-pressure EPR investigations. The bulk modulus of the high-pressure phase (49.1 GPa) is very close to that determined for the low-pressure phase (50.0 GPa), and both are comparable with those determined for the aristotype phases of CsCdF₃, TlCdF₃, RbCdF₃, and KCaF₃. The evolution of the order parameter with pressure is consistent with recent modifications to Landau theory and, in conjunction with polynomial approximations to the pressure dependence of the lattice parameters, permits the pressure variation of the bond lengths and angles to be predicted. On entering the high-pressure phase, the Rb–F bond lengths decrease from their extrapolated values based on a third-order Birch–Murnaghan fit to the aristotype equation of state. By contrast, the Ca–F bond lengths behave atypically by exhibiting an increase from their extrapolated magnitudes, resulting in the volume and the effective bulk modulus of the CaF₆ octahedron being larger than the cubic phase. The bulk moduli for the two component polyhedra in the tetragonal phase are comparable with those determined for the constituent binary fluorides, RbF and CaF₂.  相似文献   

Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska     

Christopher F. Waythomas  Philip Watts  Fengyan Shi  James T. Kirby 《Quaternary Science Reviews》2009,28(11-12):1006-1019

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources.To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths that range from 40 to 80 km, maximum thicknesses of 400–800 m, and maximum widths of 10–40 km. We also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse, at four locations (Makushin, Cleveland, Seguam and Yunaska SW volcanoes), which represent large to moderate sized events in this region. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model, which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large local tsunamis as well as large transoceanic tsunamis. These waves may be several meters in elevation at distal locations, such as Japan, Hawaii, and along the North and South American coastlines where they would constitute significant hazards.  相似文献   

Win-win scenarios at the climate–development interface: Challenges and opportunities for stove replacement programs through carbon finance     

Gregory L. Simon  Adam G. Bumpus  Philip Mann 《Global Environmental Change》2012,22(1):275-287

Achieving win-win outcomes in environment–development programs is a laudable goal, but frequently difficult to realize. In this paper we review the possibilities for win-win climate and development outcomes in programs that distribute improved cookstoves with the use of carbon finance. We show that improved cookstove technologies form an important, if asymmetrical, environment–development interface, and illustrate the mutually supported local (development) and global (climate change) benefits of continued improved stoves use—where success in one program area is directly tied to benefits in the other. We also describe how program results are highly contextual and that, in practice, there are a number of challenges to achieving effective ‘win-win’ outcomes—including cultural, financial, governance and technological barriers. While carbon finance provides an opportunity to fund scaleable and enforceable stove programs, it may also introduce mutually supported impediments—where progress towards one set of program objectives, directly compromises progress towards other objectives. Drawing on development debates for improved cookstove use, scientific reports on stove-based greenhouse gas reductions, and preexisting case studies of carbon and non-carbon financed cookstoves in Peru, Uganda and Cambodia, we conclude that the challenge for future carbon financed improved cookstove projects will be to leverage inherent symbioses between climate and development arenas in order to overcome mutually supported impediments. Achieving substantive win-win conditions will require further scholarly and practical engagement to tackle the many outstanding challenges and uncertainties reviewed in this essay.  相似文献