排序方式： 共有4条查询结果，搜索用时 500 毫秒
1
1.
Using groundwater quality data from the Lusatian post-mining district a hydrogeochemical model is derived for the evolution of mining affected groundwaters in pyrite-rich dumps which consist mainly of silicates and variable amounts of calcite. Pyrite oxidation paralleled by buffer processes leads to gypsum saturation in a significant portion of the water. Gypsum precipitation controls SO4 and Ca concentrations in groundwaters above an ionic strength (I) of 60 mM. It has been found that there is always a clear relationship between I, SO4 and Ca concentrations. In particular, there is a tendency that Ca concentrations decrease with increase in ionic strength above I = 60 mM and a striking rareness of samples with SO4 concentrations between 20 and 30 mM above an ionic strength of 100 mM. These observations are explained by a genetic model. This model also explains the observed relationship between the c(Fe)/c(SO4)-ratio, the ionic strength, and the observed pH-values. Based on the field data and supported by geochemical equilibrium calculations, it is shown that silicate weathering along with calcite dissolution must be a significant buffering process at least in some areas. 相似文献
2.
John P. Ortiz Mark A. Person Peter S. Mozley James P. Evans Susan L. Bilek 《Ground water》2019,57(3):465-478
We used hydrogeologic models to assess how fault-zone properties promote or inhibit the downward propagation of fluid overpressures from a basal reservoir injection well (150 m from fault zone, Q = 5000 m3/day) into the underlying crystalline basement rocks. We varied the permeability of the fault-zone architectural components and a crystalline basement weathered layer as part of a numerical sensitivity study. Realistic conduit-barrier style fault zones effectively transmit elevated pore pressures associated with 4 years of continuous injection to depths of approximately 2.5 km within the crystalline basement while compartmentalizing fluid flow within the injection reservoir. The presence of a laterally continuous, relatively low-permeability altered/weathered basement horizon (kaltered layer = 0.1 × kbasement) can limit the penetration depth of the pressure front to approximately 500 m. On the other hand, the presence of a discontinuous altered/weathered horizon that partially confines the injection reservoir without blocking the fault fluid conduit promotes downward propagation of pressures. Permeability enhancement via hydromechanical failure was found to increase the depth of early-time pressure front migration by a factor of 1.3 to 1.85. Dynamic permeability models may help explain seismicity at depths of greater than 10 km such as is observed within the Permian Basin, NM. 相似文献
3.
Felix Bilek 《Environmental Geology》2006,49(5):674-683
Dump groundwaters in the former East-German lignite-mining district are characterized by high amounts of ferrous iron and
sulphate. Both the pyrite weathering products endanger the surface water quality when discharged into lakes. Only the precipitation
of both contaminants in the subsurface can prevent the further contamination of surface waters. The two-step process of microbial
catalyzed sulphate reduction and iron sulphide precipitation is limited by the low availability of natural organic substances
as electron donators. Therefore, a new remediation technique is developed based on the injection of a liquid organic electron
donator (methanol) into the contaminated aquifer. The saturated aquifer is used as a bioreactor, where iron monosulphides
are precipitated in the groundwater-filled pore space. Column experiments were performed under natural pressure and temperature
conditions with natural anoxic groundwater and original sediments to test the remediation technology. The test showed that
a complete iron removal (4 mmol/l), even under rather acid conditions (pH 3.8), is possible after having established an active
sulphate reducer population. The turnover of the added organic substance with sulphate is complete and the amount of the resulting
sulphide controls the effluent pH. In addition, intensified microbial activity triggers the turnover of natural organic substances.
Also, natural Fe(III) hydroxides react with the sulphide produced. Considering the long natural retention times (decades),
artificially enhanced FeS precipitation is spontaneous, although it shows kinetic behaviour in the range of days. In light
of the promising results, the development of a field scale application of this technique is considered to be necessary. It
will have to focus on the improved precipitation control of the FeS in the subsurface. 相似文献
4.
—Spatial variations in mechanical properties of the interplate thrust faults along the Japan and Middle America subduction zones are examined using teleseismic broadband earthquake recordings. Moment-normalized source duration is used to probe rigidity variations along the interface. We invert body waves to estimate source depth and source duration for 40 events in the Japan subduction zone and 38 events in the Middle America subduction zone. For both areas, there is a systematic decrease in source duration with increasing depth along the subduction zone interface. This is most likely a result of variation in properties of sediments on the plate contact. Variations in source duration are greatly reduced at depths greater than 18 km in both regions. Enhanced spatial heterogeneity at shallow depth may reflect variations in plate roughness, sediment distribution, permeability of the fault zone, and stress. 相似文献
1