Assessment of NO<Subscript>3</Subscript><Superscript>−</Superscript> contamination in a karstic aquifer,with the use of geochemical data and spatial analysis     

Evangelos P. Tziritis 《Environmental Earth Sciences》2010,60(7):1381-1390

Kopaida plain is a cultivated region of Eastern Greece, with specific characteristic related with the paleogeographic evolution and the changes in land use. The present article examines the contamination that derives from nitrates, in terms of contaminant levels, definition of sources and spatial distribution of contaminant plume. For this purpose, 50 water samples were collected from the karstic aquifer and analyzed for 15 parameters including major ions, trace elements, physicochemical parameters, and stable isotopes. The assessment of the above parameter values along with the notes derived by the statistical process revealed the existence of nitrate contamination which has been spatial defined with the aid of spatial interpolation techniques. The correlation of NO₃ ⁻ concentrations with the stable isotope values, defined the infiltration conditions and showed contaminant transport. Nitrate values revealed the potential environmental threat for local people, as 10% of the samples exceeded the parametric value of 50 ppm and 54% of them are above 25 ppm, indicating no optimal quality conditions. The origin of nitrate contamination seems to derive exclusively from the application of N-fertilizers, since the rest of potential sources were not verified by analytical data and field works.  相似文献   

Deriving airborne laser scanning based computational canopy volume for forest biomass and allometry studies     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

A computational canopy volume (CCV) based on airborne laser scanning (ALS) data is proposed to improve predictions of forest biomass and other related attributes like stem volume and basal area. An approach to derive the CCV based on computational geometry, topological connectivity and numerical optimization was tested with sparse-density, plot-level ALS data acquired from 40 field sample plots of 500–1000 m² located in a boreal forest in Norway. The CCV had a high correspondence with the biomass attributes considered when derived from optimized filtrations, i.e. ordered sets of simplices belonging to the triangulations based on the point data. Coefficients of determination (R²) between the CCV and total above-ground biomass, canopy biomass, stem volume, and basal area were 0.88–0.89, 0.89, 0.83–0.97, and 0.88–0.92, respectively, depending on the applied filtration. The magnitude of the required filtration was found to increase according to an increasing basal area, which indicated a possibility to predict this magnitude by means of ALS-based height and density metrics. A simple prediction model provided CCVs which had R² of 0.77–0.90 with the aforementioned forest attributes. The derived CCVs always produced complementary information and were mainly able to improve the predictions of forest biomass relative to models based on the height and density metrics, yet only by 0–1.9 percentage points in terms of relative root mean squared error. Possibilities to improve the CCVs by a further analysis of topological persistence are discussed.  相似文献   

Safe and just operating spaces for regional social-ecological systems     

《Global Environmental Change》2014

Humanity faces a major global challenge in achieving wellbeing for all, while simultaneously ensuring that the biophysical processes and ecosystem services that underpin wellbeing are exploited within scientifically informed boundaries of sustainability. We propose a framework for defining the safe and just operating space for humanity that integrates social wellbeing into the original planetary boundaries concept (Rockström et al., 2009a,b) for application at regional scales. We argue that such a framework can: (1) increase the policy impact of the boundaries concept as most governance takes place at the regional rather than planetary scale; (2) contribute to the understanding and dissemination of complexity thinking throughout governance and policy-making; (3) act as a powerful metaphor and communication tool for regional equity and sustainability. We demonstrate the approach in two rural Chinese localities where we define the safe and just operating space that lies between an environmental ceiling and a social foundation from analysis of time series drawn from monitored and palaeoecological data, and from social survey statistics respectively. Agricultural intensification has led to poverty reduction, though not eradicated it, but at the expense of environmental degradation. Currently, the environmental ceiling is exceeded for degraded water quality at both localities even though the least well-met social standards are for available piped water and sanitation. The conjunction of these social needs and environmental constraints around the issue of water access and quality illustrates the broader value of the safe and just operating space approach for sustainable development.  相似文献   

First evidence of the Cambrian basement in Upper Peninsula of Thailand and its implication for crustal and tectonic evolution of the Sibumasu terrane     

《Gondwana Research》2014,25(3-4):1031-1037

Although the Sibumasu terrane in Asia was previously considered to be composed of Phanerozoic rocks with Cambrian crystalline basement, no reliable or direct radiometric dating evidences of such crystalline basement was ever reported. Our new in-situ zircon U/Pb dating of the Khao Tao orthogneiss yields a concordant age of 501.5 ± 7.5 Ma (2σ), which provides the first robust evidence for the Cambrian crust in Upper Peninsula of Thailand. The zircon εHf_(T) values range from + 3.7 to − 6.1 with model ages (T^C_DM) of 1244–1827 Ma, suggests a mixed crust-mantle source. The chemical similarity and spatial continuity of the Khao Tao orthogneiss with other pre-Neotethys marginal Eurasian and Sibumasu granitoids indicate the linear paleogeographic association under a similar magmatic arc-related regime along the Gondwana India–Australia margin as part of the Pan-African Orogeny system.  相似文献   

Density-Stratified Flow Events in Great Salt Lake,Utah, USA: Implications for Mercury and Salinity Cycling     

David L. Naftz  Gregory T. Carling  Cory Angeroth  Michael Freeman  Ryan Rowland  Eddy Pazmiño 《Aquatic Geochemistry》2014,20(6):547-571

Density stratification in saline and hypersaline water bodies from throughout the world can have large impacts on the internal cycling and loading of salinity, nutrients, and trace elements. High temporal resolution hydroacoustic and physical/chemical data were collected at two sites in Great Salt Lake (GSL), a saline lake in the western USA, to understand how density stratification may influence salinity and mercury (Hg) distributions. The first study site was in a causeway breach where saline water from GSL exchanges with less saline water from a flow restricted bay. Near-surface-specific conductance values measured in water at the breach displayed a good relationship with both flow and wind direction. No diurnal variations in the concentration of dissolved (<0.45 μm) methylmercury (MeHg) were observed during the 24-h sampling period; however, the highest proportion of particulate Hg_total and MeHg loadings was observed during periods of elevated salinity. The second study site was located on the bottom of GSL where movement of a high-salinity water layer, referred to as the deep brine layer (DBL), is restricted to a naturally occurring 1.5-km-wide “spillway” structure. During selected time periods in April/May, 2012, wind-induced flow reversals in a railroad causeway breach, separating Gunnison and Gilbert Bays, were coupled with high-velocity flow pulses (up to 55 cm/s) in the DBL at the spillway site. These flow pulses were likely driven by a pressure response of highly saline water from Gunnison Bay flowing into the north basin of Gilbert Bay. Short-term flow reversal events measured at the railroad causeway breach have the ability to move measurable amounts of salt and Hg from Gunnison Bay into the DBL. Future disturbance to the steady state conditions currently imposed by the railroad causeway infrastructure could result in changes to the existing chemical balance between Gunnison and Gilbert Bays. Monitoring instruments were installed at six additional sites in the DBL during October 2012 to assess impacts from any future modifications to the railroad causeway.  相似文献   

Effect of macropore tortuosity and morphology on preferential flow through saturated soil: A Lattice Boltzmann study     

《Computers and Geotechnics》2014

Unlike micropores where water moves upward or downward based on hydraulic gradient, in macropores, water flows predominantly downward due to the gravity. Therefore, models based on capillary flow are not capable of simulating macropore flow. There are attempts to model the macropore flow using two domains, one for capillary flow and another one for macropores. These models use Richard’s equation for capillary flow and Poiseuille’s law for macropores in which the macropore is approximated to be cylindrical or planar. This study quantifies the magnitudes of the errors induced by this assumption. Influence of macropore shapes and tortuosity was quantified by using a 3D Lattice Boltzmann model, which is capable of simulating fluid flow in micropores as well as macropores of cracked clays. Artificial macropores of constant sectional area and volume, but different shapes were generated in 3D and the influence of macropore shapes, shape related parameters, and tortuosity were systematically investigated. Macropore flow rate decreases with different shapes compared to cylindrical macropores and increase in aspect ratio of sectional shape leads to decrease in macropore flow rate. The maximum effect of bends/turnings along the tortuous macropore was about 25% on overall decrease of flow rate due to tortuosity. However, more detailed study is required on the influence of bends on macropore flow rate. The macropore flow rate reduces by about 70% for tortuosity of 1.41. A prediction equation is verified to predict the flow rate of different shapes and tortuous macropores based on straight cylindrical macropore using aspect ratio and tortuosity factor.  相似文献   

Invariant manifolds, phase correlations of chaotic orbits and the spiral structure of galaxies     

N. Voglis  P. Tsoutsis  C. Efthymiopoulos 《Monthly notices of the Royal Astronomical Society》2006,373(1):280-294

In the presence of a strong   m = 2  component in a rotating galaxy, the phase-space structure near corotation is shaped to a large extent by the invariant manifolds of the short-period family of unstable periodic orbits terminating at L ₁ or L ₂. The main effect of these manifolds is to create robust phase correlations among a number of chaotic orbits large enough to support a spiral density wave outside corotation. The phenomenon is described theoretically by soliton-like solutions of a Sine–Gordon equation. Numerical examples are given in an N -body simulation of a barred spiral galaxy. In these examples, we demonstrate how the projection of unstable manifolds in configuration space reproduces essentially the entire observed bar–spiral pattern.  相似文献   

The role of the earth scientist in assessing the impacts of climatic changes due to the greenhouse effect: two case studies of 'prognostic geology'     

C. Perissoratis  D. Georgas 《地学学报》1994,6(3):306-312

  相似文献   

An (U-Th)/He age for the small Monturaqui impact structure,Chile     

《Quaternary Geochronology》2022

Single-crystal (U-Th)/He dating of 32 apatite and zircon crystals from an impact breccia yielded a weighted mean age of 663 ± 28 ka (n = 3; 4.2 % 2σ uncertainties) for the Monturaqui impact structure, Chile. This ~350 m diameter simple crater preserves a small volume of impactite consisting of polymict breccias that are dominated by reworked target rock clasts. The small size, young age and limited availability of melt material for traditional geochronological techniques made Monturaqui a good test to define the lower limits of the (U-Th)/He system to successfully date impact events. Numerical modeling of ⁴He loss in apatite and zircon crystals shows that, for even small craters such as Monturaqui, the short-lived compressional stage and shock metamorphic stage can account for the observed partial to full resetting of (U-Th)/He ages in accessory minerals. Despite the distinctly different ⁴He diffusion parameters of apatite and zircon, the 2σ-overlapping youngest ages are recorded in both populations of minerals, which supports the inference that the weighted mean of the youngest (U-Th)/He population is the age of formation of this impact structure.  相似文献   

AMT法勘查贵州铝土矿   总被引：1，自引：0，他引：1  

张西君  王永泰  陈坡 《物探与化探》2015,(2):283-287

贵州铝土矿资源储量丰厚,分布面广,但多为隐伏型沉积型矿,仅有的易辨别、易发现的地表或浅层铝土矿已经开发殆尽,在此开展隐伏铝土矿的物探方法试验研究对今后勘查工作具有重要的指导意义。本文简要介绍了AMT基本工作方法以及贵州金沙长沟工区的地质和地球物理特征,重点讨论了AMT在长沟工区铝土矿勘查中的应用效果,通过对电阻率断面图的综合推断解释,划分出了二叠系、石炭系、寒武系之间地层界面,圈出了含矿有利部位。经钻孔验证,取得了较好的找矿效果。  相似文献