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1.
Abstract. Surface water bodies are expected to form in several pits
at the Getchell Open Pit Mine after mining has ceased due to
inflowing surface and ground water. Predicting the long-term
geochemical behavior of the pit water is important in assessing
potential environmental effects. One of the pits, the Summer
Camp Pit, began to develop a pit lake in 1991 when dewatering
ceased and the pit was used to store water pumped from
underground operations. This provided a field-scale opportunity
to identify the controls on lake water chemistry and determine
the effects of seasonal mixing events on long-term chemical
behavior. During a five-year period (1996-2001), a number of
physical, chemical and mineralogical characteristics of the lake
were monitored with the intent of using this information as a
basis for predicting long-term geochemical behavior of future
lakes in the other pits. Seasonal and multiyear cycles were
identified within the water column. These cycles were influenced
by climatic changes and element and sediment loadings of inflow
to the lake. Stratification occurred, with the metalimnion or
active layer of the lake evolving from a low total dissolved
solids (TDS), alkaline water to a high TDS, neutral to mildly
acidic water, until turnover occurred due to density variations
between the metalimnion and epilimnion, completely mixing the
layers. A hypolimnion that formed has the potential to stabilize
metals in the basal sediments as sulfide minerals below a
chemolimnion in the lake. Longer-term events also appear to
involve the hypolimnion.The monitoring program demonstrated the dynamic nature of
a pit lake and how the complex limnology can affect seasonal
water quality. Such considerations are important in interpreting
water quality from pit lakes and in selecting monitoring data to
use when constructing mathematical models for predicting changes
in water quality. 相似文献
2.
Abstract. Permitting of open pit mines that intersect the
groundwater table necessitates the use of sophisticated
numerical models to determine the temporal impact of pit lake
hydraulics. However, while mine feasibility and the potential
environmental influences of open-pit dewatering can be estimated
using conventional screening-level methods, to date there have
been few published transient analytical solutions to estimate
the pit lake recovery duration and inflow rates. The
Comprehensive Realistic Yearly Pit Transient Infilling Code
(CRYPTIC) described here is based on the Jacob-Lohman equation,
modified to include the pit geometry and effects of
precipitation and evaporation from the pit lake surface as well
as the input/output of external flows. It assumes that the
aquifer is homogeneous and isotropic with laterally extensive
horizontal flow but differs from other methods in that it
includes transient inflows. CRYPTIC was used to successfully
model the Berkeley Pit Lake (Butte, Montana) recovery data and
its predictions also compared favorably with results from the
Pipeline Pit (north-central Nevada) numerical model. However,
while this analytical approach provides useful hydraulic
insights at the feasibility stage of mine planning, more
detailed analysis is required to determine critical mine
permitting requirements. For example, the lateral extent of the
drawdown cone, time to maximum extent of dewatering, and
temporal effects on springs and seeps require deployment of a
full numerical code and substantially more data. 相似文献
3.
Abstract. The Sleeper open pit gold mine operated from the mid-1980s
through the mid-1990s. Operations were mostly sub-water table
and extensive dewatering was required to lower groundwater
levels by 180 m. Dewatering flows peaked at 930 L/s, with most
flow contributed from an alluvial aquifer. After completion of
mining, the pit was rapidly filled with water pumped from the
alluvial aquifer to reduce the exposure time of sulfide wall
rocks and waste rocks in the ultimate pit. The pumped alluvial
groundwater provided a large volume of low total dissolved
solids (TDS), high alkalinity water that controlled the early
chemistry. The rising lake waters were amended with lime to
buffer excess acidity contributed to the lake from reactive pit
wall rocks during submergence. The pore water contained in
submerged waste rock at the base of the pit was elevated in TDS
and subsequently of higher density that the lake water. The
density contrast and waste rock location limited contributions
of waste rock pore water to the main body of the lake. Some
stratification of the early lake occurred, with shallow water
characterized by higher pH, low dissolved metals, and sulfate;
deeper water had lower pH and higher dissolved metals and
sulfate. The reservoir of alkalinity in the shallow layer mixed
with the deeper waters and created a stabilized lake with a
homogenized column that exceeded water quality expectations.
Current water quality meets all Nevada primary drinking water
standards with the exception of sulfate, TDS, and manganese,
which are slightly elevated, as predicted. Chemistry has
remained stable since development of the initial lake. 相似文献
4.
Abstract. The concentration of dissolved organic carbon (DOC) in the Berkeley pit lake water ranges from 2 to 4 mg/L, and is comparable
to that of its inflow waters. On the dates sampled, the DOC concentrations decreased towards the surface of the lake, in a
manner similar to the concentration of dissolved Fe. This may reflect adsorption of DOC onto newly formed ferric precipitates
in the epilimnion of the lake. The total organic carbon (TOC) content of the lake sediment is 0.20 to 0.33%, and is on the
low end of TOC in natural aquatic sediments. In contrast, the DOC concentrations of sediment pore waters are unusually high,
ranging from 50 to 380 mg/L, and are much higher than DOC values of pore waters from typical marine or lacustrine sediments.
The high DOC concentrations are explained by release of adsorbed organic carbon from ferric precipitates as they age and recrystallize,
coupled with the relative scarcity of heterotrophic bacteria in the acidic and heavy metal-rich waters that would otherwise
consume DOC through reduction of sulfate. 相似文献
5.
Abstract. Due to operational and regulatory practicalities, pit lakes will continue to be common legacies of mine lease relinquishments.
Unplanned or inappropriate management of these geographical features can lead to both short- and long-term liability to mining
companies, local communities, and the nearby environment during mining operations or after lease relinquishment. However,
the potential for pit lakes to provide benefit to companies, communities, and the environment is frequently unrecognised and
yet may be a vital contribution to the sustainability of the open-cut mining industry. Sustainable pit lake management aims
to minimise short and long term pit lake liabilities and maximise short and long term pit lake opportunities. Improved remediation
technologies are offering more avenues for pit lakes resource exploitation than ever before, at the same time mining companies,
local communities, and regulatory authorities are becoming more aware of the benefit these resources can offer. 相似文献
6.
Larry G. Twidwell Christopher H. Gammons Courtney A. Young Richard B. Berg 《Mine Water and the Environment》2006,25(2):86-92
Abstract. Unconsolidated sediment at the bottom of the Berkeley pit lake is a mixture of detrital silicate minerals derived from sloughing
of the pit walls and secondary minerals precipitated out of the water column. The latter include gypsum and K-rich jarosite.
The pore waters have a similar pH to the overlying lake waters (pH 3.1 to 3.4), and have similarly high concentrations of
dissolved heavy metals, including Al, Cd, Cu, Mn, Ni, and Zn. Sediment cores show that the top meter of the sediment column
is moderately oxidized (jarosite-stable). Petrography, chemical analysis and geochemical modelling all suggest a transformation
of poorly crystalline ferric compounds such as schwertmannite and/or ferrihydrite near the sediment surface to jarosite with
depth in the core. No evidence of bacterial sulfate reduction was found in this study, despite the presence of 0.3 to 0.4
wt% organic carbon in the pit lake sediment. 相似文献
7.
Abstract. The basic chemical properties of Tertiary (T) and Quaternary (Q) aquifers near the Piaseczno opencast sulphur mine and the
water in the open pit, along with the stratigraphy and hydrogeology of the area, were characterized to assess the feasibility
of inundating the mine with ground water. Ground water quality varied markedly in the opencast area. A distinct stratification
was noted in the pit water; total dissolved solids, calcium, chloride, hardness, and hydrogen sulphide increased from the
top water level to the bottom of the pit lake. The concentrations of SO42- and Cl- in the opencast water were very high, especially in the hypolimnion zone. Based on our preliminary analysis, it appears that
an artificial lake formed in the Piaseczno open pit could be used in the future as a fish and wildlife habitat as well as
for recreational purposes. 相似文献
8.
Abstract. In the Eastern Middle Anthracite field of Pennsylvania, a
formerly acidic (pH = 3.6) surface mine lake (initially
approximately 45,000m3 in volume) is
being reclaimed using fluidized bed combustor (FBC) ash. The pH
of the water in the pit dramatically increased when the alkaline
ash was added. The pH of the water is now well buffered, and has
not dropped below a value of 11.0 since March 2000. Analysis of
data from samples collected over the past six years indicate
that the lakes alkalinity is controlled by carbonate, silicate,
and hydroxide reactions. The relative importance of these
factors varies with ash input, and can be determined in a
predictable fashion. Laboratory tests determined that the mass
of CaO was more significant than the particle surface area on
the pH of the solution. Using only alkaline material, the
transition between caustic and carbonate alkalinity was
apparent, though this did not account for interaction with
silicate minerals, which should be considered when using
alkaline ash for reclamation. Field data indicate that with
time, the pH will again decrease but will be buffered by calcite
present on both the upper walls of the mine pool and within
pores of the FBC ash. Less than 1% of the ash is currently used
to increase the pH and alkalinity, so a large reserve exists for
long term buffering capacity. 相似文献
9.
Abstract. The Berkeley pit lake in Butte, Montana is one of the largest accumulations of acid mine drainage in the world. The pit lake
began filling in 1983, and continues to fill at a rate of roughly 10 million liters d-1. This paper details how changes in mining activities have led to changes in the rate of filling of the pit lake, as well
as changes in its limnology and geochemistry. As of 2005, the Berkeley pit lake is meromictic, with lower conductivity water
resting on top of higher conductivity water. This permanent stratification was set up by diversion of surface water—the so-called
Horseshoe Bend Spring—into the pit during the period 2000 to 2003. However, the lake may have been holomictic prior to 2000,
with seasonal top-to-bottom turnover events. The present mining company is pumping water from below the chemocline to a copper
precipitation plant, after which time the Cu-depleted and Fe-enriched water is returned to the pit. Continued operation of
this facility may eventually change the density gradient of the lake, with a return to holomictic conditions. A conceptual
model illustrating some of the various physical, chemical, and microbial processes responsible for the unusually poor water
quality of the Berkeley pit lake is presented. 相似文献
10.
Improving the Accuracy of Geochemical Rock Modelling for Acid Rock Drainage Prevention in Coal Mine 总被引:1,自引:0,他引:1
Abstract.
The results of static tests are used to geochemically model the distribution of potentially acid and non-acid forming materials and plan mining excavation and overburden dumping to prevent or minimize the generation of acid rock drainage (ARD). The accuracy of the model depends very much on the amount and validity of the available pre-mine data and how the data is interpreted in both lateral and vertical directions. This results of such modelling was compared with subsequent overburden information provided by analysis of blast hole drill cuttings. We found that the model overestimated the amount of potentially acid forming material, but that it was still useful in ARD prevention. 相似文献
11.
Using the DRASTIC System to Assess the Vulnerability of Ground Water to Pollution in Mined Areas of the Upper Silesian Coal Basin 总被引:1,自引:1,他引:1
Abstract An attempt was made to use the U.S. EPA DRASTIC ranking system to assess the vulnerability of ground water in the Upper Silesian
Coal Basin. Analysis of the various system components indicate that several DRASTIC factors would have to be modified to consider
the effects of mining, subsidence, and ground water rebound. 相似文献
12.
Robert S. Hedin 《Mine Water and the Environment》2006,25(3):146-152
Abstract: The net acidity of a water sample can be measured directly by titration with a standardized base solution or calculated from
the measured concentrations of the acidic and basic components. For coal mine drainage, the acidic components are primarily
accounted for by free protons and dissolved Fe2+, Fe3+, Al3+, and Mn2+. The base component is primarily accounted for by bicarbonate. A standard way to calculate the acidity for coal mine drainage
is: Acidcalc = 50*(2*Fe2+/56 + 3*Fe3+/56 + 3*Al/27 + 2*Mn/55 + 1000*10-pH)—alkalinity, where acidity and alkalinity are measured as mg/L CaCO3 and the metals are mg/L. Because such methods of estimating acidity are derived by independent laboratory procedures, their
comparison can provide a valuable QA/QC for AMD datasets. The relationship between measured and calculated acidities was evaluated
for 14 datasets of samples collected from mine drainage discharges, polluted receiving streams, or passive treatment systems,
containing a total of 1,484 sample analyses. The datasets were variable in nature, ranging from watersheds where most of the
discharges contained alkalinity to ones where all of the discharges were acidic. Good relationships were found to exist between
measured and calculated acidities. The average acidity measurement was 239 mg/L CaCO3 and the average acidity calculation was 226 mg/L CaCO3. Linear regressions were calculated for individual datasets and for the entire dataset. The linear regression for the entire
dataset was: Acidcalc = 0.98 * Acidmeas – 8, r2 = 0.98. The good correlation between calculated and measured acidity is the basis for an easy and inexpensive QA/QC for AMD
data. Substantial variation between measured and calculated acidities can be used to infer sampling or analytical problems. 相似文献
13.
Oliver Totsche Andrew Fyson Christian E. W. Steinberg 《Mine Water and the Environment》2006,25(4):204-213
Abstract. Microbial alkalinity production was evaluated as a method to prevent reacidification of neutralized mining lakes by acidic
ground and seepage water. We used 60 L mesocosms to represent the sediment and water column of a shallow acidic mine lake.
To enhance alkalinity production, acidic and neutralized lake waters were treated with either phosphorus (controlled eutrophication)
or organic matter (controlled saprobization). Controlled eutrophication could not produce enough autochthonous biomass as
substrate for microbial alkalinity production to change the acidity of the water. Chemical pre-neutralization of the acidic
water caused the inorganic carbon concentration to increase, but at the same time, hindered algae growth by reducing the availability
of phosphate by sorption to the freshly precipitated iron hydroxide. This effect was so strong that even high phosphorus additions
could not increase the algae biomass production. In contrast to controlled eutrophication, controlled saprobization produced
significant alkalinity. Despite inhibition of the most important alkalinity producing process, namely microbial sulfate reduction,
by low pH values, the microbial alkalinity production rate was not affected by pre-neutralization of the water column. Other
alkalinity producing processes raised the pH in the reactive zone until sulfate reduction was no longer inhibited. 相似文献
14.
Abstract. Airborne geophysical reconnaissance was used to identify
potential flow paths for mercury-rich, acidic water entering
Clear Lake near the Sulphur Bank Mercury Mine. Airborne magnetic
and electromagnetic conductivity surveys were conducted over a
12.3 km2 (4.75
mi2) area that included the Oaks Arm
of Clear Lake and the old mine. These surveys identified four
magnetic and/or conductive anomalies that may represent
groundwater conduits towards or away from the Herman
Impoundment. An anomaly that extended from Herman Impoundment
through a waste rock dam and into Clear Lake was selected for a
more detailed ground electromagnetic conductivity survey. The
combined results of the airborne and ground surveys provided a
detailed, lateral depiction of conductive zones, the most
probable pathways for groundwater flow. These surveys also
identified near-surface areas that may contain elevated
concentrations of sulfide minerals that weather to produce acid
groundwater. 相似文献
15.
Abstract: Modeling of mine water rebound in the southernmost zone of the Durham Coalfield has been undertaken in an attempt to reproduce
observed water level recovery, since the 1970s, within five coal blocks south of the Butterknowle Fault. The lumped parameter
model GRAM (groundwater rebound in abandoned mineworkings) was chosen to perform the simulations since it overcomes, to a large extent, a common problem found in such studies,
namely a lack (especially concerning historic hydrogeological records) and superabundance of various kinds of data. The results
obtained from this approach are satisfying and closely resemble the observed pattern of mine water rebound for the mining
blocks studied. Such research indicates the critical dependence of predictions on factors such as the volume of water flowing
into the system, the percentage runoff, and the value of storage coefficient assigned to the old workings. Model predictions
are most useful as a tool for improving the conceptual understanding of abandoned mine systems and as a basis for evaluating
alternative possibilities of coalfield behaviour, rather than as a strict quantitative assessment for all management purposes. 相似文献
16.
Abstract.
This paper summarizes the dynamics and causes of the Stava disaster, and highlights some risky design procedures that led to the 19 July 1985 tailings dam failure. It then presents the Stava 1985 Foundation, which was formed to focus attention on such risks and to strengthen the culture of respect for human lives and safety. 相似文献
17.
Abstract Closure of Pb-Zn mines in the Iglesias district (SW Sardinia, Italy) caused the cessation of pumping in 1997, and the consequent flooding of underground workings. Deep saline water mixed with the shallow groundwater as the water table rose, increasing salinity. Stratification caused the saline water at depth to settle over a period of three years. At the beginning of rebound, an increase in dissolved Zn, Cd, Pb, and Hg was observed under near-neutral pH conditions. Following peak concentrations, a marked decrease of Zn, Cd, and Hg, and to a lesser extend Pb, occurred. After 7 years of rebound, the concentrations of these metals are relatively low at most mine sites, although the levels are generally still higher than in unmined areas. Nowadays, the highest release of metals to the aquatic system occurs from the weathering of tailings and mine wastes. 相似文献
18.
Abstract Closure of Pb-Zn mines in the Iglesiente district (SW Sardinia, Italy) caused the cessation of pumping in 1997 at Monteponi,
and in 1998 at San Giovanni. Consequent flooding of underground workings occurred in the district and also involved Campo
Pisano. In June 1998, as the water table rose from 160 to 20 m below sea level, the deep saline water mixed with the shallow
ground water at Monteponi and nearby mines. In the same period, an increase in dissolved metals (especially Zn, Cd, and Pb)
was observed under near-neutral pH conditions. Following peak concentrations, a marked decrease of Zn, Cd, and Hg occurred.
Dissolved Pb showed fluctuating concentrations over the monitoring period (1996-2005). In January 2000, when the water table
rose to 20 m above sea level, the salinity of ground water decreased significantly at all of the mines. Stratification caused
the more saline water at depth to settle three years after rebound started. Depth profiles carried out in 2005 at Monteponi,
San Giovanni, and Campo Pisano showed an increase in conductivity and dissolved metals in ground water at deeper levels, especially
at depths below sea level.After eight years of rebound, a marine component was still present at depth in ground water at San
Giovanni (about 2%), and to a lesser extent at Monteponi (about 0.4%). 相似文献
19.
Abstract.
Drainage systems in large surface mines are designed to
accomplish three basic objectives: keeping working conditions
dry, stable and safe; lowering hydrostatic pressure and
increasing the effective stress of soil to improve slope
stability; and ensuring pit floor workability. This can be
achieved with drainage facilities that include channels, water
collection sumps, and pump stations. We report the development
of a computer-aided system called Dewatering of Open Pit Mines
(DEWOP), which can assist open pit mine designers to solve
water-related problems. The system was developed in a Visual
Basic object programming language, taking advantage of
multi-user, open database connectivity, such as Microsoft
Access, for storage and processing of information. In tests at
coal and copper surface mines, it reduced drainage facilities
costs by 8%. 相似文献
20.
K. Gnandi G. Tchangbedji K. Killi G. Baba A. I. Ouro Salim 《Mine Water and the Environment》2005,24(4):215-221
Abstract About 2.5 million t of sedimentary phosphorite mine tailings, highly enriched with trace metals such as Cd, Cr, Cu, Ni, and
Zn, are dumped annually in the coastal waters of Togo without any pre-treatment, causing serious pollution problems in the
region. We conducted laboratory jar tests of a coagulation-flocculation procedure with coagulants RM45U and AN945MPM to clarify
the sludge. The efficiency of the method depends particularly on two factors: the amount of coagulant and the solid concentration
of the sludge to be treated. Thus, with a mud concentration of 47.7 g/L, the average optimal amount of the two coagulants
was 25 mg/L. With both coagulants, water turbidity passed from 60 x 103 NTU to approximately 3 NTU after clarification with
the optimal amount of the two coagulants. RM45U reduced concentrations of Pb by 40%, Zn by 98.8%, Fe by 80.6%, and Cd by 32.8%.
AN945MPM reduced Pb by 20%, Zn by 98.5%, Fe by 48%, and Cd by 32.8%. 相似文献