A regular solution site-mixing model for illites

The dependence on the composition of the thermodynamic stability of an illite can be treated in terms of a regular solution site-mixing model. Four end-member micas (muscovite, pyrophyllite, phlogopite, and annite) were mixed to simulate an illite in this study. In the model, random mixing of cations was assumed over each given class of cation sites. Mixing over cation sites between different classes of cation sites was not allowed. The resulting free energy and chemical potential equations contain four site interaction parameters: three for octahedral site interactions and one for interlayer and tetrahedral site interactions. These parameters cannot presently be evaluated because of a lack of experimental data on Fe³⁺-free illites. The model does imply that the octahedral site interaction parameters must be significantly more positive than the interlayer and tetrahedral site interaction parameter to account for the dominant dioctahedral nature of most natural illites. This constraint is necessary to balance out the increase in stability due to the configurational entropy of an illite having a major trioctahedral component.The model can be extended to cover a wider range of illite compositions by the inclusion of an end-member mica containing Fe³⁺ ions in the octahedral sites. At present the thermodynamic properties of such an end-member are unknown.     

Silica in Lake Superior: mass balance considerations and a model for dynamic response to eutrophication

The dissolved silica concentration in waters of Lake Superior probably is in a steady state because it is not influenced significantly by man, and the climate, topography and vegetation in the drainage area of the lake have been stable for the past 4000 years. Therefore the rate at which dissolved silica is introduced to the lake should equal the output rate.The primary inputs are: tributaries (4.1–4.6 × 10⁸kgSiO₂/yr), diffusion from sediment pore waters (0.21?0.78 × 10⁸kgSiO₂/yr) and atmospheric loading (0.26 × 10⁸kgSiO₂/yr). Silica is lost from the lake waters by: outflow through the St. Marys River, diatom deposition, adsorption onto particulates in the sediments, and authigenic formation of new silicate minerals. Tributary outflow accounts for less than one half the annual input of silica, and diatom deposition and silica adsorption withdraw less than 10% of the annual input. Therefore the formation of new silicate phases must be the dominant sink for dissolved silica in Lake Superior. The specific phases formed are not identified in the bottom sediments. X-ray diffraction studies suggest that smectite is one product, and amorphous ferroaluminum silicates may be another product.Mathematical modeling of the dissolved silica response to lake eutrophication suggests that the phosphate loading to Lake Superior would have to increase by about 250-fold to cause a silica depletion rate equal to that reported for Lake Michigan, assuming no change in the rate of upwelling of deep waters.     

Non‐local damage modelling of concrete: a procedure for the determination of model parameters

This paper presents a procedure for the determination of parameters of non‐local damage models. This is to assure a consistent response of a non‐local damage model, as choice of the internal length and other parameters of the model are varied. Correlations between the internal length and other parameters governing the local constitutive behaviour of the model are addressed and exploited. Focus is put on the relationship between the internal length of the non‐local model and the width of the fracture process zone. Numerical examples are used to demonstrate the rigour of the proposed method. Copyright © 2006 John Wiley & Sons, Ltd.     

A digital model to evaluate the water balance in a typical hardrock environment

A digital model was designed and developed to study the water balance situation in a typical hardrock environment near Hyderabad, Andhra Pradesh. The model was calibrated over a period of six years with observed field hydrographs. An optimum error factor of 0.001 m was chosen and the computer took 47 iterations for outputting the results with the desired accuracy. Prognostic studies were carried out with progressively increasing draft conditions and water levels were observed to be declining even when the draft was less than the recharge. The analysis of the experiments further amended the belief of the earlier workers.     

Uncertainty in a monthly water balance model using the generalized likelihood uncertainty estimation methodology

Journal of Earth System Science - Hydrological models are simplified representations of natural processes and subject to errors. Uncertainty bounds are a commonly used way to assess the impact of...     

First approximation sea-level dependent mathematical model for volume eroded and submarine profile development in a semienclosed sea: Kiel Bay,Western Baltic

Given a marine basin of near homogeneous lithology, a known sea level curve, and known submarine abrasion rates, a model is developed to estimate the volume of material eroded by marine action. Assumptions of the model are that erosion is effected solely by submarine abrasion, which is assumed known and uniform through time, and that the volume eroded is small relative to the total volume of the basin. The basis of the model is that the volume eroded V, between time limits t₁ andt ₂,is essentially a function of the perimeter length l of the basin, which in turn is time-dependent on the sea level curve, so that $$V = k\int_{t1}^{t2} {l(t)dt} $$ where k is an abrasion rate constant. The model was tested on Kiel Bay, Western Baltic, a shallow semienclosed, essentially nontidal sea, for which considerable data is available. Critical for numerical integration of the model is the k value, representing the volume eroded from the shore normal profile per unit length of shoreline per year. A number of possible k values were utilized, the most likely realizing a total volume eroded over the past 9000 y, since the sea first entered Kiel Bay, of 2.60×10⁹ m ³. From this model, long-term average vertical submarine abrasion rates for Kiel Bay can be deduced as being between 0.001 and 0.0004 m/y. An extension to the model analyzes the effect of sea level transgression rate on whether cliffs develop and predicts the theoretical form of the submarine profile based on varying abrasion rates summarized as $$y_B (x) = \left\{ {\begin{array}{*{20}c} {h({x \mathord{\left/ {\vphantom {x {V_c }}} \right. \kern-\nulldelimiterspace} {V_c }}) - a_T (x) for x > 0;} \\ {x\tan \theta - a_T (x) for x > 0.} \\ \end{array} } \right.$$ Here the origin x=0, y_B=0 is chosen horizontally at the position where cliff formation first occurs, and vertically at the sea level at that time. The coordinate x measures distance inshore from the origin, y_B(x) is the vertical position of the sea floor, a_T(x) is the total depth abraded, tanθ is the original land surface slope, V_c the rate of cliff retreat, and h(t) the sea-level at time t. The synthetic profiles are compared to actual erosional profiles from representative sectors of Kiel Bay. The model predicts cliff development began at about 5800 yB.P., resulting in submarine abrasion profile lengths of about 1740 m and cliff heights of about 17.4 m for original land surface slopes of 0.01. This agrees to within about 10% of mean values obtained from bathymetric and topographic maps.     

干旱内陆灌区土壤水盐模型

研究干旱内陆区土壤水分运移规律以及土壤盐分运移规律,有助于合理利用水资源,减少潜水无效蒸发,防止土壤盐碱化。根据水量平衡和盐量平衡原理,建立了土壤水盐模型,计算土壤水盐迁移量,并对干旱内陆区土壤水盐运移规律做了初步研究。     

Computation of surface energies in an electrostatic point charge model: I. Theory

The attachment energies, the slice energies and the specific surface energies can be calculated in an electrostatic point charge model using the formula derived by Madelung for the potential introduced by an infinite row of equally spaced point charges. Power series are given for the Hankel function iH ₍₀₎ ⁽¹⁾ (iy) and Ψ(x)=d ln x!/dx. The logarithmic expression in the Madelung formula converges rapidly when applying a power series, which combines equally charged cations and anions. Besides the specific surface energy (γ ^hkl), the slice energy (E _s ^hkl ) and the attachment energy (E _a ^hkl ) can be considered as special categories of surface energies as they depend on surface configurations as well. The specific surface energy γ is the energy per unit area of surface needed to split the crystal parallel to a face (hkl). The attachment energy (E _a) is the energy released per mole, when a new slice of thickness d _hkl crystallizes on an already existing crystal face (hkl). The growth rate of the crystal face (hkl) is a function of its attachment energy. The slice energy (E _s) is the energy released per mole, when a new slice d _hkl is formed from the vapour neglecting the influence of edge energies. The lattice energy (E _c) which is the energy released per mole of a crystal crystallizing from the vapour, is given by the following relation: E _c=E _a+E _s.     

Theoretical modelling of cis -vacant and trans -vacant configurations in the octahedral sheet of illites and smectites

 The cis-vacant configurations of smectites and illites have been studied theoretically by using transferable empirical interatomic potentials. A wide range of compositions of octahedral and tetrahedral cation and interlayer charge has been considered. All results have been compared with the trans-vacant configurations in each sample. The calculated values reproduce the differences in the lattice parameters between the cis- and trans-vacant configurations of experimental studies. Taking into account the cis-/trans-vacant proportion, the calculated structures agree with experiment for the main structural features of the crystal lattice. The effect of the cation substitution in the octahedral and tetrahedral sheets on the cell parameters has been also studied, finding good linear relationships. The calculated cation substitution effects are consistent with experimental results. Although the energy difference between the cis- and trans-vacant configurations is small, the cis-vacant is more stable when the composition of clays is more smectitic, like the experimental behaviour. Similar trends of the cation substitution effect on the cis-/trans-vacant proportion to the experimental results are found. The structure of the hydroxy groups has also been analysed. The OH bond length, the orientation of the O–H bond with respect to the (001) plane and the non-bonding H...O distances have been studied. Received: 4 September 2000 / Accepted: 29 January 2001     

Quantitative assessment of drought in a lacustrine wetland based on a water balance model

Upstream inflow decline and excessive water withdrawal are the major reasons for failure in maintaining ecological functions of wetlands and could lead to wetland drought and degradation. Quantitative evaluation of wetlands drought constitutes the basis for managing and scheduling water resources and guaranteeing biological safety. In the study, we proposed a Palmer wetland drought index (PWDI) based on the water balance model that describes wetland hydrological characteristics linked to its located basin to describe drought-reflected ecological characteristics in lacustrine Baiyangdian Wetland and compared it with Palmer drought severity index (PDSI). The results presented that PWDI is able to reflect the worst drought in history, and the drought is mainly affected by water stored in the wetland, but PDSI is inadequate for evaluating the wetland drought. The PWDI methodology provides a clear, objective approach for describing the intensity of drought and can be readily adapted to characterize drought on an operational basis.     

Evaluation of the SWAT model for water balance study of a mountainous snowfed river basin of Nepal

In this study, a semi-distributed hydrologic model Soil and Water Assessment Tool (SWAT) has been employed for the Karnali River basin, Nepal to test its applicability for hydrological simulation. Further, model was evaluated to carry out the water balance study of the basin and to determine the snowmelt contribution in the river flow. Snowmelt Runoff Model (SRM) was also used to compare the snowmelt runoff simulated from the SWAT model. The statistical results show that performance of the SWAT model in the Karnali River basin is quite good (p-factor = 0.88 and 0.88, for daily calibration and validation, respectively; r-factor = 0.76 and 0.71, for daily calibration and validation, respectively). Baseflow alpha factor (ALPHA_BF) was found most sensitive parameter for the flow simulation. The study revealed that the average annual runoff volume available at the basin outlet is about 47.16 billion cubic metre out of which about 12% of runoff volume is contributed by the snowmelt runoff. About 25% of annual precipitation seems to be lost as evapotranspiration. The results revealed that both the models, SWAT and SRM, can be efficiently applied in the mountainous river basins of Nepal for planning and management of water resources.     

考虑植被和人类活动影响的水文模型参数时变特征分析

变化环境下流域水文物理特性常呈现"非稳态"特征,代表流域特性的模型参数也会随之发生变化,因此,开展水文模型参数时变研究有助于提高水文模拟精度。考虑植被条件和人类活动对水文过程的影响,基于植被归一化指数、人口、地区生产总值、粮食产量和有效灌溉面积5个指标建立两参数月水量平衡模型参数的时变函数表达式,并考虑4种参数时变情形。选取直门达、张家山、咸阳、横江、丹江口和峡江站6个水文站分析对比4种情形下模型的径流模拟结果及其不确定性。结果表明:所有站点在1982—2006年内水文物理特性呈现"非稳态"特征;且较常参数而言,时变参数模型模拟效果更好,并获得更优的确定性预报结果,其中直门达站径流模拟精度提高最为显著,率定期和检验期内的纳西效率系数（N_S）分别提高了10.3%和8.8%。该研究可以为变化环境下流域水库调度、水资源规划与管理等提供理论依据和技术支撑。     

VEBEX: Vegetation and surface energy balance experiment for the tropics

Surface features such as soil moisture and vegetation have a profound impact on the surface energy balance and the atmospheric boundary layer. To quantify this effect for a tropical location, a detailed field experiment, VEBEX, was designed and successfully executed in a tropical site at Bangalore, India. VEBEX was a joint experiment between the North Carolina State University, Indian Institute of Science (IISc), and the University of Agricultural Science (UAS) at Bangalore, India. Continuous surface meteorological measurements were taken over an entire crop period (pre-sowing to post-harvest). During different stages of the plant growth, intensive observations of surface turbulence, and measurements of physiological and soil moisture measurements were also conducted. The results obtained provide an insight into the unusually strong variability for the tropics. Interpretation of the observations and an overview of the analysis procedure and future research initiatives are also presented.     

Rural diversification in the Baltic countryside: a local perspective

Today “rural diversification” is high on the agenda in rural development. This article analyses rural diversification under conditions of post-socialist economic transition using case areas in Latvia and Estonia. The study shows that transition from centrally planned economy to market economy has had an enormous impact in the rural areas. Agricultural production and employment has decreased dramatically and rural unemployment is high. The conditions for rural diversification the first years after independence depended a lot on the local presence of non-farm activities before the split up of collective farming, in both production facilities but also in the skills and relations people had. Since independence, markets for traditional rural services and products have decreased. The extent to which local businesses find markets outside the local area and people have been able to integrate into the new labour market of service and construction jobs often in urban areas are essential for the diversification of the rural economy. Most rural inhabitants only have skills in large-scale agriculture and limited contacts to outside the local area which makes exploiting new opportunities difficult. The local capacity for withholding, developing and inducing new activities is weak. The challenge for rural development policy is to extend the possibilities of the rural inhabitants to exploit new opportunities.     

Application of the water balance model J2000 to estimate groundwater recharge in a semi-arid environment: a case study in the Zarqa River catchment, NW-Jordan

Pollution and overexploitation of scarce groundwater resources is a serious problem in the Zarqa River catchment, Jordan. To estimate this resource’s potential, the amount and spatial distribution of groundwater recharge was calculated by applying the hydrological model J2000. The simulation period is composed of daily values gathered over a 30-year period (July 1977 to June 2007). The figure finally obtained for estimated groundwater recharge of the Zarqa River catchment is 105 × 10⁶ m³ per year (21 mm a^?1). This is 19 % higher than the value previously assumed to be correct by most Jordanian authorities. The average ratio of precipitation to groundwater recharge is 9.5 %. To directly validate modelled groundwater recharge, two independent methods were applied in spring catchments: (1) alteration of stable isotope signatures (δ¹⁸O, δ²H) between precipitation and groundwater and (2) the chloride mass balance method. Recharge rates determined by isotopic investigations are 25 % higher, and recharge rates determined by chloride mass balance are 9 % higher than the modelled results for the corresponding headwater catchments. This suggests a reasonably modelled safe yield estimation of groundwater resources.     

Stochastic water balance model for rainfall recharge quantification in Ruataniwha Basin,New Zealand

Quantification of groundwater recharge is important for water resources management. Different methods can be used to estimate groundwater recharge. The most suitable approach depends on site characteristics. Water balance model was used in this study to quantify groundwater recharge from rainfall in Ruataniwha Basin, Hawke’s Bay, New Zealand. Because it is a closed basin, this method was determined to be more suitable than any other method. The basin is fed by surface water flow and rainfall, without any lateral groundwater flow. Records of surface water inflow and outflow are available with a certain degree of reliability. To cope with uncertainty in different components of water balance, different sampling methods were used. The Mean Value Latin Hypercube Sampling (MVLHS) was used and compared with Latin Hypercube Sampling (LHS), and Monte Carlo Simulation (MCS). It was found the groundwater recharge from rainfall is about 415 million m³/year. Results of this study have revealed that MVLHS converges faster and with lower variance than LHS and MCS.     

The chronology of dinosaur oospecies in south-western Europe: Refinements from the Maastrichtian succession of the eastern Pyrenees

The Late Cretaceous deposits of the continental Tremp Formation in the Vallcebre Syncline (South-eastern Pyrenees) provide an extensive egg record of dinosaurs. The parataxonomical study and analysis of multiple eggshell samples, the precise stratigraphical control of several sections and the time calibration of the abundant egg levels enable the establishment of a robust oospecies succession. The successive occurrence of three megaloolithid oospecies (Megaloolithus siruguei-Megaloolithus mamillare-Megaloolithus sp.) in the Early and Late Maastrichtian is well correlated with the magnetic polarity time scale throughout the chron 31. The replacement of Megaloolithus siruguei with Megaloolithus mamillare occurs around the reversal of chrons 31r-31n. A comparison with oospecies successions from Arc basin localities (France) allows the age calibration for such oospecies replacement to be confirmed. This age refinement implies that some of the stated boundaries for the proposed oospecies assemblages may change and that an in-depth revision of the age and magnetic calibration of some south European egg localities is required.     

An Improved Set of a--X Parameters for Fe--Mg--Ca Garnets and Refinements of the Orthopyroxene-Garnet Thermometer and the Orthopyroxene--Garnet--Plagioclase--Quartz Barometer

An internally consistent set of activity-composition relationsfor Fe-Mg-Ca garnets constrained from calorimetric and phaseequilibrium experiments provides the basis for refining theorthopyroxene-garnet thermometer and the orthopyroxene-garnet-plagioclase-quartzbarometer based on the equilibria FeSiO₃ + 1/3Mg₃Al₂Si₃O₁₂ = MgSiO₃ + 1/3Fe₃Al₂Si₃O₁₂ (A) Mg₂Si₂O₆ + CaAl₂Si₂O₈ = 2/3 Mg₃Al₂Si₃O₁₂ + 1/3 Ca₃Al₂Si₃O₁₂+ SiO₂ (B) Fe₂Si₂O₆ + CaAl₂Si₂O₈ = 2/3 Fe₃Al₂Si₃O₁₂ + 1/3 Ca₃Al₂Si₃O₁₂+ SiO₂. (C) The major modification arises from better constrained valuesof mixing parameters for the pyrope-almandine binary. Thermodynamicanalysis of reversed experimental data on Fe-Mg partioning betweenorthopyroxene and garnet (Kawasaki & Matsui, 1983; Lee &Ganguly, 1988), when combined with the enthalpy of solutiondata for the pyrope-almandine binary (Geiger et al.t 1987),yields and AGIT of the exchange reaction as cal in the temperaturerange 1248–1573 K. The retrieved data, combined with the known thermochemical parametersfor the pyrope-grossular and almandine-grossular binaries andcomplementary phase equilibrium data, have been used to estimatetemperatures from equilibrium (A) and pressures from equilibria(B) and (C). The geothermometer registers temperatures higherby 70–100C than those obtained from Harley's (1984) formulationand 20–40?C lower than those from Lee & Ganguly's(1988) formulation for granulite grade rocks; the scatter inestimated temperatures for all areas is lower when comparedwith the other two formulations. The estimated pressures from(B) and (C) are reasonable for granulite grade rocks in thepressure range 3.0–12.0 kb and agree, in most cases, within? 1000'b. The smaller scatter in the computed temperatures and convergenceof calculated pressure values support the claim that the formulationspresented here represent improved versions of the orthopyroxene-garnetgeothermometer and the orthopyroxene-garnet-plagioclase-quartzgeobarometer.     

Origin of Illites at Dexing Porphyry Copper Deposit,Jiangxi Province,East China：Implications for Alteration Zoning and Ore—Forming Fluid Evolution

According to differences in features of illites including spatial distribution, crystallinity index, volume of swelling layer, polytype and relationship between its index and copper grade, two typical kinds of illite can be classified within the Tongchang porphyry copper deposit, Dexing County, East China. One is a kind of hydrothermally altered minerals within the hydrothermal alteration zone, including altered granodiorite-porphyry and altered metamorphic tuffaceous phyllite near the contact zone with porphyry rockbody. The illite crystallinity and expandability are mainly affected by water/rock ratio or fluid flux, and hydrothermal illite is formed by illitization of plagioclase and/or micas during hydrothermal fluid evolution within the porphyry body and near the contact zone with wall rocks. The other is a product of low-grade metamorphism itself by illitization of smectite, whose crystallinity index is lower than the hydrothermal illite and which is of 2M₁ polytype with no swelling layer, in the altered metamorphic tuffaceous phyllite far from porphyry rockbody ( > 2 km). Moreover, the negative correlation between illite index and copper grade indicates that, within the alteration zone, the smaller the illite crystallinity, the stronger the alteration degree, and the higher the copper grade due to higher water/rock ratio. At lower levels of the porphyry body, however, the illite crystallinity (IC) values are controlled mainly by temperature and time.