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11.
Tracing leachates at landfills is usually carried out using either geophysical methods or chemical analyses of groundwater.
There are often problems with fingerprinting pollution sources or clarifying the spreading pattern due to a wide variety of
possibilities giving similar anomalies. The aims of the project were to evaluate the advantages of combining results from
multigeophysical modelling and statistical/chemical modelling in order to identify pollution sources and the spreading pattern
and to test a new technique for chemical fingerprinting. The project was carried out at a landfill in central Sweden using
geophysical measurements and modelling of CVES, GPR and VLF as well as chemical modelling using M3 (multivariate mixing and
mass balance calculations). The results indicate that by combining geophysical modelling and chemical calculations, the possibilities
of fingerprinting the origin of pollution as well as delineating the spreading pattern are significantly increased. 相似文献
12.
Mark Wilkinson 《Chemical Geology》2002,191(4):277-283
K-Ar ages of Gulf Coast shales do not correspond to diagenetic ‘events’, but are a combination of inherited detrital ages and authigenic overprints. The key to understanding K-Ar ages of shales is the fate of the 40Ar when the host minerals dissolve or react during the illitisation reaction: is 40Ar incorporated within the illite, or is it lost to the porewaters? Ages are modelled as due to a single illitisation reaction, assuming a uniform precursor sediment and open-system import of K. Both whole-rock and clay mineral fraction data can be reproduced by modelling. The 40Ar incorporated into illite is a surprisingly high proportion (75-100%) of that produced within detrital phases (smectite, K-feldspar, mica), perhaps implying that the illitisation reaction is a solid-state transformation, or that 40Ar is imported into the shales along with incoming K. The model does not provide a good fit to the data below 4000 m, when the illitisation reaction is apparently complete, but shales lose 40Ar by solid-state diffusion or recrystallisation. 相似文献
13.
欠压实地层古地层压力恢复的统计模拟法及其在松辽盆地中的应用 总被引:1,自引:0,他引:1
恢复烃源岩古地层压力和对于研究其生留排烃过程具有重要意义。Nakayama[1]等在开展盆地模拟研究时应用Rubey(1959)和Chapman(197)等人提出的数学地质模型对欠压实地层的古地层压力进行恢复。本文通过对松辽盆地欠压实地层的研究发现欠压实因子随地层厚度、埋深、围岩渗透性等地质条件的不同而改变,在此基础上提出了欠压实地层压力恢复的统计模拟法,克服了目前Nakayama[1]等将地层埋藏过程中的欠压实因子视为常数的不足,从而使计算结果更接近实际。统计模拟法在松辽盆地的应用结果表明了这一方法在实用中的可行性和有效性。 相似文献
14.
Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with
various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and
N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest,
including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate
the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical
load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two
catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering
(i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline
in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive
data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by
strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition
by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and
vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included
in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state
condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up
to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition
since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge
area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the
sandstone aquifer.
Received: 30 July 1996/Accepted: 23 January 1997 相似文献
15.
A model to simulate 137Cs profiles in soils during the time in which they are being eroded is proposed. The model uses one parameter to characterize the cesium transference in the soil and another to express the erosion rate. To test the model, 137Cs profiles of stable and eroded soils were collected at sampling sites located on semi-arid and temperate slopes in the Central Ebro basin, Spain. The 137Cs profiles, corresponding to uncultivated soils with natural vegetation cover, were simulated using this model. The 137Cs inventories and profiles calculated with the model are very similar to those measured experimentally, and thus it is possible to calculate soil erosion rates in physiographically diverse Mediterranean environments. 相似文献
16.
A.K.L. Johnson 《The Australian geographer》2004,35(1):39-57
Rainfall regimes with strong spatial and temporal variation are characteristic of many coastal regions of north and eastern Australia. In coastal regions of north eastern Australia, regimes vary considerably over short distances. This occurs because of changes in local topography, including the height and orientation of mountain ranges and the direction of the coastline with respect to the prevailing moist south east air stream. Northern Australia experiences a tropical monsoon climate with rainfall occurring predominantly during the summer months. Areas with a closer proximity to the coast typically experience the heavier rainfalls. While networks of rainfall gauges have been established and continuous records are available for most of these stations from the 1890s, their low distribution density relative to the complexity of rainfall pattern they are required to represent means that there remains a poor understanding of the spatial and temporal distribution of rainfall in the wet tropics. An enhanced knowledge of rainfall distribution in both space and time has the potential to deliver significant economic and environmental benefits to managers of natural resources. This paper reports on the application of a technique for estimating mean annual and mean monthly rainfall across the Herbert River catchment of north east Australia's dry and wet tropics. The technique utilises thin plate smoothing splines to incorporate both location and elevation into estimates of rainfall distribution. We demonstrate that the method can be applied successfully at the meso scale and within the domain of routinely available data. As such, the method has broad relevance for decision making. 相似文献
17.
Predicting the future DOC flux from upland peat catchments 总被引:6,自引:0,他引:6
18.
Evaluation of current statistical approaches for predictive geomorphological mapping 总被引:5,自引:3,他引:5
Predictive models are increasingly used in geomorphology, but systematic evaluations of novel statistical techniques are still limited. The aim of this study was to compare the accuracy of generalized linear models (GLM), generalized additive models (GAM), classification tree analysis (CTA), neural networks (ANN) and multiple adaptive regression splines (MARS) in predictive geomorphological modelling. Five different distribution models both for non-sorted and sorted patterned ground were constructed on the basis of four terrain parameters and four soil variables. To evaluate the models, the original data set of 9997 squares of 1 ha in size was randomly divided into model training (70%, n=6998) and model evaluation sets (30%, n=2999).In general, active sorted patterned ground is clearly defined in upper fell areas with high slope angle and till soils. Active non-sorted patterned ground is more common in valleys with higher soil moisture and fine-scale concave topography. The predictive performance of each model was evaluated using the area under the receiver operating characteristic curve (AUC) and the Kappa value. The relatively high discrimination capacity of all models, AUC=0.85–0.88 and Kappa=0.49–0.56, implies that the model's predictions provide an acceptable index of sorted and non-sorted patterned ground occurrence. The best performance for model calibration data for both data sets was achieved by the CTA. However, when the predictive mapping ability was explored through the evaluation data set, the model accuracies of CTA decreased clearly compared to the other modelling techniques. For model evaluation data MARS performed marginally best.Our results show that the digital elevation model and soil data can be used to predict relatively robustly the activity of patterned ground in fine scale in a subarctic landscape. This indicates that predictive geomorphological modelling has the advantage of providing relevant and useful information on earth surface processes over extensive areas, such data being unavailable through more conventional survey methods. 相似文献
19.
Experimental evidences and numerical modelling of debris flow initiated by channel runoff 总被引:1,自引:1,他引:1
Debris flow initiation by channel bed mobilization is a common process in high mountainous areas. Initiation is more likely
to occur at the outlet of small, steeply sloping basins where concentrated overland flow feeds an ephemeral channel incised
in slope deposits. Such geological conditions are typical of the Dolomite region (Italian Alps), which is characterized by
widespread debris flow activity triggered by severe summer thunderstorms. Real-time data and field observations for one of
these catchments (Acquabona catchment, Belluno, Italian Alps) were used to characterize the hydrological response of the initiation
area to rainfalls of varying intensity and duration. The observed behaviour was then reproduced by means of a simple hydrological
model, based on the kinematic wave assumption, to simulate the generation of channel runoff. The model is capable of predicting
the observed hydrological response for a wide range of rainfall impulses, thus providing a physical basis for the understanding
of the debris flow triggering threshold. 相似文献
20.
Sulphate reduction is a key reaction to remove acidity from water bodies affected by acid mine drainage. In this study, 35SSO42− reduction rates determined in sediments from a variety of acidic lignite pit lakes have been compiled. The rates decreased with pH and are strongly dependent on carbon substrate. The rates were fitted to a Monod model adapted to the specific conditions of acidic pit lakes (APL) sediments: i) sulphate reduction rate is independent from sulphate concentration due to the high concentration typically observed in APL systems (10–30 mM), ii) the observed pH dependency of sulphate reduction was accounted for by an inhibition function Finihibt which considers the occurrence of low cell numbers of sulphate reducing bacteria at pH values < 4.75. Simulated steady-state sulphate reduction rates are predicting measured rates at carbon substrate concentrations of <10 μM. Estimated steady-state reaction time scales range between 2.4 h at pH 7 and 41 h at pH 3 at a carbon half-saturation constant of KC−S = 100 μM and are increasing with increasing KC−S values. Time scales at low pH are too long to allow for significant generation of alkalinity during the time of residence of groundwater passing through the top and hence most reactive zone of APL sediments which has important implications for the remediation of acidic pit lakes. 相似文献