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1.
A detailed characterization of the site is crucial to designing an efficient method of managing the risks associated with
tailings from abandoned mines. Therefore, samples collected from various depths within tailings in Guryong mine, Korea, were
analyzed for their chemical, physical and mineralogical characteristics. All samples of the Guryong tailings had acid-generating
potential. However, in the oxidation zone, the net acid generation (NAG) was low (30 kg H2SO4 t−1) although the acid neutralization potential (ANP) was less than zero. The ANP values in the unoxidation zone were higher
(> −56.0 kg CaCO3 t−1) than in the other zones. As a result, the amount of alkali ions that are needed to neutralize the acid needs to be considered.
In this experiment G3, G4 and G6 drill cores containing fine tailings particles near the unoxidation zone were observed to
contain calcite (CaCO3) with acid-neutralizing capacity. A low pH (2−4) in the oxidation zone of the tailings changed to a neutral pH in the unoxidation
zone of the tailings. These results suggest that the acid-neutralizing capacity of the tailings was controlled by particle
and mineral composition of tailings. 相似文献
2.
A physically-based semidistributed model, TOPMODEL, is applied to a 340 hectare spruce forested catchment in mid-Wales. the model is calibrated to runoff and the subsurface flow is divided into components of flow identified by depth of origin. in addition, chemical mixing techniques are used to provide a hydrograph separation between acidic soil waters and well buffered deep waters. the short-term variations in the components of flow identified by these two approaches compare well. 相似文献
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4.
近距离地闪电场变化及对通道电荷密度分布的响应 总被引：1，自引：0，他引：1
一般认为,如果回击过程将先导通道的电荷完全中和,则几十米到几百米范围内的近距离先导电场与回击电场的大小相同,否则,二者之间则存在一定的差异。为了对上述观点进行分析,将源电荷先导模式和MTLL回击模式组合建立了先导-回击模式(这两个模式的组合意味着先导通道的电荷被回击完全中和),对近距离先导-回击电场变化的"V"形结构进行了模拟分析。结果表明,即使假定先导电场被回击完全中和,在近距离30—550m范围回击电场与先导电场强弱关系并不确定。另外,根据进一步的讨论,上述模拟结果几乎不受其他因素,如土壤湿度(该因素直接决定土壤电参数)和地形起伏的影响。因此,在回击开始几十微秒内,基于地面测量的先导-回击电场之差来判断先导通道电荷是否被回击完全中和可能存在一定的不确定。 相似文献
5.
M.?BenzaazouaEmail author B.?Bussière A.-M.?Dagenais M.?Archambault 《Environmental Geology》2004,46(8):1086-1101
Five sulfide mine tailings coming from the Joutel mine tailing ponds (Quebec, Canada) were tested by the humidity cell test (30 to 52 cycles duration) and the column test (11 to 12 cycles duration). The objectives of this study were twofold. First, there was the determination of the tailings acid generation potential for site reclamation. Second, there was the kinetic test comparison for understanding the tailings geochemical behavior under different test conditions. The samples used had a wide diversity in terms of acid-generation potential, particle size distribution, and parameters influencing reaction rates. Leachates produced remained at a near neutral pH for the duration of the tests. Evolution of the main elements involved in the dissolution processes demonstrated neutralization by carbonates as a response to the acid generated by sulfide oxidation. Depletion rates given by sulfates are higher for the humidity cell tests when compared to those obtained for the column tests. This is consistent with most studies to date, the humidity cell test being considered as more severe. However, by taking the ratio between cumulative elements coming from neutralization and the ones coming from oxidation, similar curves (named herein oxidation –neutralization curves) for all tests were obtained. These results show that overall geochemical behavior of the tailings is similar at near neutral pH for both types of tests. With this interpretation method, the acid-generation potential of the Joutel tailings were tested and compared to the static test results to constrain their uncertainty zone with regard to the studied tailings. The tailings geochemical behavior (carbonate dissolution response to sulfide oxidation) at near neutral pH condition appears slightly dependent of test conditions under certain hypothesis. 相似文献
6.
Binding Character of Selected Elements in Acidic Mining Lake Sediments To investigate the vertical element distribution in an acidic mining lake the concentrations of selected elements were measured by ICP‐MS and ICP‐OES. By knowing the metal concentrations in different depths it is possible to divide these metals into three groups. While the concentrations of iron, manganese, and zinc decline with decreasing depth, those of aluminium, copper, and nickel rise up. For lead and cobalt no distinct tendency could be determined. The limit value for all measured elements was not exceeded in any sampling location. The binding character of the metals is, besides the seasonal conditions of the lake (circulation in spring and stagnation in summer), influenced by the sediment depth. The addition of Carbokalk® for lake water neutralization had no significant effect on binding character of the analyzed metals. The application of a sequential extraction procedure enabled a classification of the available metal binding forms. All analyzed metals occurred mainly in compounds which are difficult to mobilize and for environment only slightly available. 相似文献
7.
The North Appalachian Experimental Watershed in Coshocton, Ohio, USA has recorded average pH of precipitation of 4.7 over a 30-year period. The area lies within the Pennsylvanian siltstones and shale, dominated by aluminosilicates and <5% calcite. A study was conducted to determine the evolution of acid deposition through an unsaturated to saturated zone composed of siltstone and shale in an isolated hill, precluding lateral flow and seepage. The results from water–rock chemical reactions modeled using PHREEQM demonstrate the percolating precipitation water is neutralized to pH 7.5 within the top 1.5 m. The model suggests that, along with calcite, dissolution of albite, illite, and kaolinite are the dominant mechanisms of neutralization. The cation exchange capacity of the siltstone and shale, in the range 54.6–386 meq/100 g, appears to be a function of high organic carbon content of 2.0–3.2%. While cation exchange is responsible for some of the Na+ in solution, it is not the primary source of Ca2+, Mg2+, or K+ ions. Exchange onto clays is occurring, but is secondary to exchange on organic matter. Chemical composition of groundwater perched within a coal seam is controlled by oxidation and dissolution of pyrite, returning pH to approximately 4.0. 相似文献
8.
The present study investigated the chemical composition of wet atmospheric precipitation in India’s richest coal mining belt.
Total 418 samples were collected on event basis at six sites from July to October in 2003 and May to October in 2004 and analysed
for pH, EC, F−, Cl−, , , Ca2+, Mg2+, Na+, K+ and . The average pH value (5.7) of the rainwater of the investigated area is alkaline in nature. However, the temporal pH variation
showed the alkaline nature during the early phase of monsoonal rainfall but it trends towards acidic during the late and high
rainfall periods. The rainwater chemistry of the region showed high contribution of Ca2+ (47%) and (21%) in cations and (55%) and Cl− (23%) in anionic abundance. The high non seas salt fraction (nss) of Ca2+ (99%) and Mg2+ (96%) suggests crustal source of the ions, while the high nss (96%) and high ratio signifying the impact of anthropogenic sources and the source of the acidity. The ratio of varies from 0.03 to 3.23 with the average value of 0.84 suggesting that Ca2+ and play a major role in neutralization processes. The assessment of the wet ionic deposition rates shows no any specific trend,
however Ca2+ deposition rate was highest followed by and
. 相似文献
9.
Mineralogical constraints on the determination of neutralization potential and prediction of acid mine drainage 总被引：4，自引：1，他引：3
A. D. Paktunc 《Environmental Geology》1999,39(2):103-112
Acid-base accounting tests, commonly used as a screening tool in acid mine drainage (AMD) predictions, have limitations in
(1) measuring with confidence the amount of neutralizers present in samples and (2) affording an interpretation of what the
test results mean in terms of predicting the occurrence of acid mine drainage. Aside from the analytical difficulties inherent
to the conventional methods, a potential source of error in neutralization potential (NP) measurements is the contribution
from the dissolution of non-carbonate minerals. Non-carbonate alkalinity measured during static tests may or may not be available
to neutralize acidity produced in the field. In order to assess the value-added of extending the NP with the knowledge of
mineralogical composition and evaluate potential sources of errors in NP measurements, a suite of samples were examined and
characterized in terms of their mineralogical and chemical compositions. The results indicate that although the acid-base
accounting tests work well for simple compositions, the tests may result in overestimation or underestimation of NP values
for field samples. Mineralogical constraint diagrams relating NP determinations to Ca, Mg and CO2 concentrations were developed with the purpose to serve as supplementary guides to conventional static tests in identifying
possible NP contributions from non-carbonate minerals and checking the quality of the chemical testing results. Mineralogical
NP makes it possible to interpret the meaning of NP results and to assess the behaviour of samples over time by predicting
the onset of AMD and calculating NP values for individual size fractions.
Received: 1 June 1998 · Accepted: 6 October 1998 相似文献
10.
In this study, variations of the chemical composition of precipitation in Nanjing, China, over a 12-year period (1992–2003) are presented. The average annual concentration of pH value was 5.15, ranging from 4.93 to 5.36, and there was no significant trend in the acidity of precipitation. SO42−, Cl− and NO3− were the main anions, while Ca2+, NH4+ and Mg2+ were the main cations. The concentrations of these main ions were very high compared to those reported in many other areas around the world. Most of the ions came from anthropogenic and crustal sources. High correlations were found among dust-derived cations Ca2+, Mg2+and K+, between Cl− and SO42−, between Cl− and NH4+ and between acidic anions and dust-derived cations, such as SO42− and Ca2+, SO42− and K+, Cl− and Ca2+, Cl− and K+, F− and Mg2+ and F− and K+. A significant decreasing trend was observed in concentration of SO42− because of the abatement strategies for SO2 emissions and energy policy change, while a significant increasing trend was found in the contribution of NO3− to acidification due to the rapidly growing number of motor vehicles. A significant decreasing trend was found in dust-derived cation Ca2+ due to more stringent controls of industrial dust emissions and rapid urbanization reducing the amount of open land, while the contribution of NH4+ to neutralization increased relatively. 相似文献