Geochemistry of mine waters draining a low-sulfide, gold-quartz vein deposit, Bralorne, British Columbia     

Alexandre J. Desbarats  Michael B. Parsons  Jeanne B. Percival  Suzanne Beauchemin  Y.T. John Kwong 《Applied Geochemistry》2011,26(12):1990-2003

The Bralorne and Pioneer mines, now inactive, produced over 4 million ounces of Au from an orogenic lode Au deposit located on the eastern edge of the Coastal Mountains of SW British Columbia. Between 2007 and 2009, drainage from a recently developed exploration adit was investigated in order to better understand and anticipate potential environmental management issues associated with the development of this type of deposit in the future. Portal discharge rate and specific conductance were monitored continuously over a 14-month period during which 36 water samples were collected. Additional samples were collected from flooded workings within the adit. Concentrations of As and Sb at the portal range as high as 1738 and 316 μg/L, respectively, while those in the mine pool reach 3304 and 349 μg/L, respectively. Effluent chemistry is mildly alkaline (pH = 8.7) and is dominated by Na, Ca, Mg, HCO₃ and SO₄. Geochemical inverse modeling of effluent composition indicates weathering of albite (2515 kg/a), ferroan dolomite (718 kg/a), pyrite (456 kg/a), arsenopyrite (23 kg/a) and stibnite (2 kg/a). Modeled sulfide reaction coefficients, normalized by their corresponding host rock concentrations, suggest that oxidation of arsenopyrite is 25 times slower than that of pyrite whereas oxidation of stibnite is 1.5 times faster. Oxidative dissolution of arsenopyrite and stibnite releases 10.6 kg/a of As and 1.1 kg/a of Sb of which 57% and 46%, respectively, are sorbed to ferrihydrite and gibbsite on the bed of the shallow channel through which the mine pool drains to the portal. Although mass balance calculations predict the formation of sufficient ferrihydrite to sorb 100% of the As dissolved in the mine pool, this attenuation process was ineffective possibly because the precipitated sorbents settled to the bottom of the water column or because of competition for sorption sites from Ca and HCO₃. The dissolved Sb/As molar ratio in portal effluent (0.082) is much greater than the Sb/As ratio of the mineralization (0.002) because of slower arsenopyrite oxidation and somewhat lesser sorption of Sb.  相似文献   

Geochemistry of the Earth’s Surface     

Suzanne Anderson  Sigurdur Gislason 《Applied Geochemistry》2011

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Intrusion and contamination of high-temperature dunitic magma: the Nordre Bumandsfjord pluton, Seiland, Arctic Norway     

W. L. Griffin  B. A. Sturt  C. J. O’Neill  C. L. Kirkland  Suzanne Y. O’Reilly 《Contributions to Mineralogy and Petrology》2013,165(5):903-930

The Caledonian Nappe Complex of Arctic Norway provides rare insights into the interaction between mafic–ultramafic magmas and the deep continental crust. The Kalak Nappe Complex contains >25,000 km³ of mafic igneous rocks, mostly layered gabbros, making up the 570–560 Ma Seiland Igneous Complex. The complex has been intruded by a series of ultramafic magmatic rocks, including the Nordre Bumandsfjord pluton. Field relationships in this pluton show that extremely fluid, dry, relatively Fe-rich (Fo₈₁) dunite magmas intruded a pile of cumulate gabbros, with block stopping and intrusive brecciation. Diking on scales from mm to metres and extensive melting and assimilation of the gabbros attest to high temperatures, consistent with a 2-km-wide granulite-facies contact aureole. Major- and trace-element trends show that the dunites were progressively contaminated by a cpx-rich partial melt of the gabbros, producing a range of lithologies from dunite through lherzolites to wehrlite. Experimental studies of natural samples at 0.8–1 GPa define the dunite solidus at 1,650–1,700 °C. In the average peridotite, contamination has produced a crystallisation interval of ca 400 °C (1,600–1,200 °C); this would provide large amounts of heat for melting and metamorphism and would maintain the fluidity of the magmas to relatively low T, consistent with field relationships. Thermochemical and dynamic modelling demonstrates that the dunitic primary magmas may represent the last melting of a rapidly ascending diapir of previously depleted subducted oceanic lithosphere. The mafic rocks of the Seiland Complex may already have been extracted from this diapir, and the late dikes of the province may reflect melting of the asthenosphere as the diapir spread out beneath the lithosphere. Ultramafic magmas, abundant in the Archean, may still be more common than usually assumed. However, they would only penetrate to the shallow crust under unusually extensional conditions, where ascent could outpace assimilation.  相似文献   

Displacement prediction in colluvial landslides, Three Gorges Reservoir, China   总被引：12，自引：7，他引：5  

Juan Du  Kunlong Yin  Suzanne Lacasse 《Landslides》2013,10(2):203-218

The prediction of active landslide displacement is a critical component of an early warning system and helps prevent property damage and loss of human lives. For the colluvial landslides in the Three Gorges Reservoir, the monitored displacement, precipitation, and reservoir level indicated that the characteristics of the deformations were closely related to the seasonal fluctuation of rainfall and reservoir level and that the displacement curve versus time showed a stepwise pattern. Besides the geological conditions, landslide displacement also depended on the variation in the influencing factors. Two typical colluvial landslides, the Baishuihe landslide and the Bazimen landslide, were selected for case studies. To analyze the different response components of the total displacement, the accumulated displacement was divided into a trend and a periodic component using a time series model. For the prediction of the periodic displacement, a back-propagation neural network model was adopted with selected factors including (1) the accumulated precipitation during the last 1-month period, (2) the accumulated precipitation over a 2-month period, (3) change of reservoir level during the last 1 month, (4) the average elevation of the reservoir level in the current month, and (5) the accumulated displacement increment during 1 year. The prediction of the displacement showed a periodic response in the displacement as a function of the variation of the influencing factors. The prediction model provided a good representation of the measured slide displacement behavior at the Baishuihe and the Bazimen sites, which can be adopted for displacement prediction and early warning of colluvial landslides in the Three Gorges Reservoir.  相似文献   

How Collaborative Approaches to Environmental Problem Solving View Indigenous Peoples: A Systematic Review     

Suzanne von der Porten  Robert C. de Loë 《社会与自然资源》2014,27(10):1040-1056

Collaborative approaches to environmental problem solving are becoming commonplace around the world. These processes often occur in the traditional territories of Indigenous peoples. Hence, how Indigenous peoples are viewed in the collaboration literature is important because of the distinctive position they hold in many societies. In this article we conducted a systematic review of the collaboration literature that focused on environmental concerns and referred to Indigenous peoples. The goals were to identify how Indigenous peoples are discussed in this literature, and to reveal the assumptions that are made about the roles and views of Indigenous peoples and nations. The Indigenous governance literature was used to highlight the contrasting perspectives of Indigenous peoples. The systematic review revealed discordant assumptions about the roles of Indigenous peoples between these two bodies of literature. Implications for the theory and practice collaborative environmental problem solving are identified.  相似文献   

Expanding Local Water Supplies: Assessing the Impacts of Stormwater Infiltration on Groundwater Quality     

Suzanne Dallman  Martin Spongberg 《The Professional geographer》2013,65(2):232-249

In urban regions, the increased volume of stormwater runoff that results from the impermeable urban landscape is a potential source of water supply, particularly for groundwater recharge. One concern regarding infiltration of stormwater is its potential impact on groundwater quality. To further evaluate this, an extensive monitoring program was conducted in and around Los Angeles, California, over a six-year period. Samples collected from stormwater runoff, the vadose zone, and groundwater were analyzed for constituents of concern including metals, nutrients, organics, bacteria, and emerging contaminants. Findings indicate no degradation of groundwater quality as a result of intentional infiltration. At sites with shallow groundwater, concentrations of some constituents decreased over the period of the study.  相似文献   

Rock damage and regolith transport by frost: an example of climate modulation of the geomorphology of the critical zone     

Robert S. Anderson  Suzanne P. Anderson  Gregory E. Tucker 《地球表面变化过程与地形》2013,38(3):299-316

In this article we craft process‐specific algorithms that capture climate control of hillslope evolution in order to elucidate the legacy of past climate on present critical zone architecture and topography. Models of hillslope evolution traditionally comprise rock detachment into the mobile layer, mobile regolith transport, and a channel incision or aggradation boundary condition. We extend this system into the deep critical zone by considering a weathering damage zone below the mobile regolith in which rock strength is diminished; the degree of damage conditions the rate of mobile regolith production. We first discuss generic damage profiles in which appropriate length and damage scales govern profile shapes, and examine their dependence upon exhumation rate. We then introduce climate control through the example of rock damage by frost‐generated crack growth. We augment existing frost cracking models by incorporating damage rate limitations for long transport distances for water to the freezing front. Finally we link the frost cracking damage model, a mobile regolith production rule in which rock entrainment is conditioned by the damage state of the rock, and a frost creep transport model, to examine the evolution of an interfluve under oscillating climate. Aspect‐related differences in mean annual surface temperatures result in differences in bedrock damage rate and mobile regolith transport efficiency, which in turn lead to asymmetries in critical zone architecture and hillslope form (divide migration). In a quasi‐steady state hillslope, the lowering rate is uniform, and the damage profile is better developed on north‐facing slopes where the frost damage process is most intense. Because the residence times of mobile regolith and weathered bedrock in such landscapes are on the order of 10 to 100 ka, climate cycles over similar timescales result in modulation of transport and damage efficiencies. These lead to temporal variation in mobile regolith thickness, and to corresponding changes in sediment delivery to bounding streams. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Impact and recovery associated with the deposition of capital dredgings at UK disposal sites: Lessons for future licensing and monitoring   总被引：1，自引：0，他引：1  

Suzanne Ware  Stefan G. Bolam  Hubert L. Rees 《Marine pollution bulletin》2010,60(1):79-90

The majority of studies relating to impacts and recovery at dredgings disposal sites have concentrated on areas subject to regular and frequent disposals of maintenance dredgings over relatively long time periods. In comparison less is known regarding the significance of impacts and the recovery processes associated with the disposal of capital dredgings that commonly involves the infrequent deposition of heterogenous material over relatively restricted time periods. Impacts and recovery processes are likely to be different to those associated with the disposal of maintenance dredgings. For example, findings suggest that capital dredgings deposited at both the Roughs Tower and Barrow-in-Furness result in the occurrence of persistent changes to seafloor substrata within the license area and this subsequently effects the composition of associated faunal communities present. Moreover, whilst the two disposal sites are geographically distinct similar species are identified as being particularly sensitive to capital disposal activities in both areas.  相似文献   

Sources and fate of nutrients in a subtropical reservoir   总被引：1，自引：0，他引：1  

Michele?A.?BurfordEmail author  Susanne?A.?Green  Andrew?J.?Cook  Suzanne?A.?Johnson  Jason?G.?Kerr  Katherine?R.?O’Brien 《Aquatic Sciences - Research Across Boundaries》2012,74(1):179-190

This study examined the sources and fate of nutrient inputs from two principal tributaries to the eutrophic subtropical Wivenhoe reservoir: an unregulated river and a dammed river with regular releases, during a period of declining reservoir water levels. Nutrient budgets were constructed over a period of 6 years, and combined with short-term data on nutrient concentrations and forms, and δ¹⁵N stable isotope data. Our study found that over a 6 year period, there was net retention of phosphorus (P) in the reservoir, with 60% of inputs retained. Most of the P input load came from the unregulated river, with an agricultural catchment, during periods of high flow. During one event half of the total TP load from the unregulated river in the study period was delivered in only 12 days. Much of the P was dissolved inorganic P (DIP) and was derived from high P concentrations in soils and sediments. This highlights the importance of appropriate catchment management practices to reduce P losses from terrestrial systems because retention of P in reservoir sediments reduces the availability of this nutrient for agricultural production. In contrast, there was negligible retention of nitrogen (N). The unregulated river was an important source of N derived from N fixation in the river and adjacent soils, while the source from the dammed river was mostly reprocessed N. The high retention of P relative to N is consistent with relatively higher accumulation of P in sediments.  相似文献   

Response of large-scale coastal basins to wind forcing: influence of topography     

Wen L. Chen  Pieter C. Roos  Henk M. Schuttelaars  Mohit Kumar  Tjerk J. Zitman  Suzanne J. M. H. Hulscher 《Ocean Dynamics》2016,66(4):549-565

Because wind is one of the main forcings in storm surge, we present an idealised process-based model to study the influence of topographic variations on the frequency response of large-scale coastal basins subject to time-periodic wind forcing. Coastal basins are represented by a semi-enclosed rectangular inner region forced by wind. It is connected to an outer region (represented as an infinitely long channel) without wind forcing, which allows waves to freely propagate outward. The model solves the three-dimensional linearised shallow water equations on the f plane, forced by a spatially uniform wind field that has an arbitrary angle with respect to the along-basin direction. Turbulence is represented using a spatially uniform vertical eddy viscosity, combined with a partial slip condition at the bed. The surface elevation amplitudes, and hence the vertical profiles of the velocity, are obtained using the finite element method (FEM), extended to account for the connection to the outer region. The results are then evaluated in terms of the elevation amplitude averaged over the basin’s landward end, as a function of the wind forcing frequency. In general, the results point out that adding topographic elements in the inner region (such as a topographic step, a linearly sloping bed or a parabolic cross-basin profile), causes the resonance peaks to shift in the frequency domain, through their effect on local wave speed. The Coriolis effect causes the resonance peaks associated with cross-basin modes (which without rotation only appear in the response to cross-basin wind) to emerge also in the response to along-basin wind and vice versa.  相似文献