[Show abstract][Hide abstract] ABSTRACT: The groundwater of Ambagarh Chouki, Rajnandgaon, India, shows elevated levels of As and F−, frequently above the WHO guidelines. In this work, the concentrations of As, F−, Na+, Mg2+, Ca2+, Cl−, SO42−, HCO3−, Fe, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the groundwater of Ambagarh Chouki are described. The sources of dissolved components in the groundwater are investigated using the cluster and factor analysis. Five factors have been identified and linked to processes responsible for the formation of groundwater chemistry. High concentrations of dissolved As seems to be linked to high concentrations of DOC, suggesting reductive dissolution of ferric oxyhydroxides as arsenic mobilization process. Fluoride is found in shallow depth water, presumably as a consequence of evaporation of water and removal of Ca2+ by precipitation of carbonates.
[Show abstract][Hide abstract] ABSTRACT: The anomalous drip in the Punkva caves (Moravian Karst) shows specific hydrogeochemical properties such as low SIcalcite~0.14±0.11 (standard deviation), low mineralization (4.53±0.42)×10-3moll-1, and enhanced values of δ13C (-7.85 to -8.35‰ VPDB), Mg/Ca×1000 ratio (45.7±3.3), and Sr/Ca×1000 ratio (0.65±0.06). By these properties, the anomalous drip significantly differs from other regular drips in the same cave and other caves in the region. The study suggests that the anomalous drip properties are a consequence of prior calcite precipitation or/and water mixing along the water flow path. As the former processes are spatially controlled, the knowledge of dripwater flow path seems to be necessary for correct paleoclimatic/paleoenvironmental reconstructions.
No preview · Article · Oct 2015 · Hydrological Processes
[Show abstract][Hide abstract] ABSTRACT: The area of the city of Tsumeb in northern Namibia is strongly affected by gaseous emissions and by dust fallout from the local smelter. This is also reflected in increased concentrations of lead and arsenic in blood and urine of the residents. Consequently, modeling of the dispersion of dust and SO2 emissions from the smelter was used in this study to delineate the contaminated area and to assess the health risks. The modeling results were verified by ground-based geochemical survey of soil and grass in the area. The results of modeling revealed that the concentrations of SO2 in the Tsumeb town were relatively low, whereas the highest dust fallout concentrations were found around the Tsumeb smelter. The Tsumeb town residential area was less affected due to favorable landscape morphology between the smelter and the city (the Tsumeb Hills).
No preview · Article · Aug 2015 · Applied Geochemistry
[Show abstract][Hide abstract] ABSTRACT: Study region: Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus: We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region: Arsenic concentrations above the WHO guideline value of 10. μg/L were present in 33 wells and above the previous Indian national drinking standard of 50. μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection-dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.
Full-text · Article · Jun 2015 · Journal of Hydrology: Regional Studies
[Show abstract][Hide abstract] ABSTRACT: The contents of As, Cu, Cd, Pb, Mn, along with the Pb isotopic ratios 206Pb/207Pb and 208Pb/206Pb were studied in both soils and tree rings of the marula tree (Sclerocarya birrea) in the vicinity of the Tsumeb deposit (Namibia). Amounts of all the studied metals and As are higher in the immediate vicinity of the Tsumeb Cu-Pb smelter in the soil. The tree rings also have their maximum content of all the studied substances in the vicinity of the smelter (with the exception of Pb). At a more distant site, the maximum concentration of Pb in the soils was 29.8 mg/kg, while the content in the soil in the vicinity of the smelter was as much as 8,174 mg/kg. In the vicinity of the smelter, the maximum Pb content in the tree rings reaches a value of 5.7 mg/kg, compared to a more distant site, where the contents are as high as 9.2 mg/kg. The lower Pb content in the trees on contaminated soil indicates that the composition of the xylem determines the above-ground uptake, rather than the root uptake. Similarly, the above-ground uptake is documented by the isotopic composition of Pb at the distant location, where the tree rings have different contents of Pb isotopes compared to in the soil. The As, Cd, Cu, Pb, and Zn contents are highest in the tree rings from the 1950s (and older), along with those from the 1990s, while the Mn contents were highest in those from the 1960s and 1990s. The contaminant peaks in the 1950s and 1960s could be associated with the roasting of sulfidic ores, while the peak values in the 1990s could have been caused by the start of Cu slag reprocessing in the late 1980s, and culmination of works at the smelter prior to the closing of the mine. The tree rings of the marula tree were found to be a suitable archive for above-ground pollution close to Cu and Pb smelters.
Full-text · Article · Jun 2015 · Water Air and Soil Pollution
[Show abstract][Hide abstract] ABSTRACT: Mine tailings at Rosh Pinah located in semiarid southern Namibia were investigated by the combination of mineralogical methods and leaching using water and simulated gastric solution. They are well-neutralized with leachate pH > 7 and neutralization potential ratios (NPR) up to 4. Neutralization is mainly due to abundant Mn-rich dolomite in the matrix. Concentrations of released contaminants in water leachate follow the order Zn > Pb > Cu > As. Relatively high leached concentrations of Zn and partly also of Pb are caused by their link to relatively soluble carbonates and Mn-oxyhydroxides. In contrast, As is almost immobile by binding into Fe-oxyhydroxides, which are resistant to dissolution. Barium is released by the dissolution of Ba-carbonate (norsethite) and precipitates in sulfate-rich pore water as barite.
No preview · Article · May 2015 · Journal of African Earth Sciences
[Show abstract][Hide abstract] ABSTRACT: Numerous hot springs and fumaroles occur along the Andes Mountains, in the Bolivian Altiplano, where people use thermal springs for recreational purposes as pools, baths and also for consumption as drinking water and irrigation once it is mixed with natural surface waters; most of these thermal springs emerge from earth surface and flow naturally into the rivers streams which drain further into the Poopó Lake. Physicochemical characteristics of the thermal water samples showed pH from 6.3 to 8.3 with an average of 7.0, redox potential from +106 to +204 mV with an average of +172 mV, temperatures from 40 to 75°C with an average of 56°C and high electrical conductivity ranging from 1.8 to 75 mS/cm and averaged 13 mS/cm. Predominant major ions are Na+ and Cl- and the principal water types are 37.5 % Na-Cl type and 37.5 % Na-Cl-HCO3 type. Arsenic concentrations ranged from 7.8 to 65.3 μg/L and arsenic speciation indicate the predominance of As(III) species. Sediments collected from the outlets of thermal waters show high iron content, and ferric oxides and hydroxides are assumed to be principal mineral phases for arsenic attenuation by adsorption/co-precipitation processes. Arsenic concentrations in cold water samples from shallow aquifers are higher than those in thermal springs (range < 5.6 to 233.2 μg/L), it is likely that thermal water discharge is not the main source of high arsenic content in the shallow aquifer as they are very immature and may only have a small component corresponding to the deep geothermal reservoir. As people use both thermal waters and cold waters for consumption, there is a high risk for arsenic exposure in the area.
Full-text · Article · Mar 2015 · Journal of South American Earth Sciences
[Show abstract][Hide abstract] ABSTRACT: The arsenic mineralization in historical waste rock pile at Kaňk site near Kutná Hora developed over a period of about 500 years. The objective of this study was to determine principal secondary arsenic mineral phases and their environmental stability. The only common primary As-bearing mineral – arsenopyrite - occurs in the mineral assemblage of Kutná Hora base-metal deposit together with quartz, pyrite, sphalerite, and pyrrhotite. Most of arsenic is bound in supergene minerals (scorodite, jarosite-beudantite, bukovskýite, pitticite), which are relatively stable under oxidizing conditions prevailing in the pile. The Kaňk site is a type locality for bukovskýite, kaňkite, zýkaite, and parascorodite. In long-term perspective, the most stable minerals from viewpoint of As-binding appear to be scorodite and beudantite. A higher mobility was observed for As incorporated into jarosite and poorly crystalline to amorphous phases (FeIII -oxyhydroxides, pitticite). This study has not confirmed significant mobility of arsenic within the pile and water infiltrating in recharge periods of the year (late winter-early spring) should not mobilize arsenic at a significant rate. However, monitoring of the stability of secondary As-phases and dissolved arsenic in the environment around the pile is required to avoid future migration of arsenic out of the pile.
No preview · Article · Feb 2015 · Mineralogy and Petrology
[Show abstract][Hide abstract] ABSTRACT: Mine tailings in African countries Zambia and Namibia have been investigated with an objective to determine the role of secondary hematite in immobilization of contaminants. Two sites, Chambishi and Mindolo, are located in the Copperbelt in Zambia with relatively humid climates and two sites, Berg Aukas and Kombat, are in Namibia, where the climate is semiarid. At the Chambishi site which is about 40 years old, a hardpan composed of hematite and gypsum has formed at a depth of about 60 cm and large amounts of Cu and Co have been deposited. At the much younger Mindolo site (30 years old, but most V remains in primary descloizite, embedded in a carbonate matrix while a relatively small amount of released V is incorporated into hematite. In contrast, released Zn and Pb are incorporated mainly into smithsonite and cerussite, which are less stable from an environmental viewpoint. Finally, at the Kombat mine tailings (< 5 years old), As released from pyrite is also incorporated into hematite, but Cu released by dissolution of chalcopyrite and bornite has precipitated as malachite, which is less stable than hematite. Water-leached concentrations of contaminants such as Cu, Zn, and Pb (also present in some carbonate phases) are an order of magnitude higher than water-leached concentrations of V and As which are bound to crystalline ferric minerals such as hematite and soluble only in the aqua regia fraction of sequential extraction. It seems that rapid formation of hematite under tropical climate conditions and incorporation of contaminants into this mineral phase is favourable for attenuation of released contaminants. These findings have implications at other mining sites with similar climates in Africa, South America and Asia.
[Show abstract][Hide abstract] ABSTRACT: Geological heterogeneity associated with layers,
open mine voids, tectonic faults and fractures can all
make modelling difficult, particularly for mine dewatering.
This heterogeneity is difficult to represent with the traditional
MODFLOW structured grid. A new version of
MODFLOW, called MODFLOW-USG (for UnStructured
Grid), supports a wide variety of structured and unstructured
grid types (Panday et al. in MODFLOW-USG version
1: an unstructured grid version of MODFLOW for simulating
groundwater flow and tightly coupled processes
using a control volume finite-difference formulation.
USGS, Reston, 2013) that provide flexibility for modelling
difficult geologic structures. This communication compares
aspects of MODFLOW and MODFLOW-USG, and uses
the Gbely lignite deposit as an example of a situation for
which MODFLOW-USG could be applied.
Full-text · Article · Dec 2014 · Mine Water and the Environment
[Show abstract][Hide abstract] ABSTRACT: Summary We present here major ion, trace element, stable and radioisotope data based on forty-six groundwater samples collected from various locations along few selected profiles across the Chianan Plain, southwestern Taiwan including the area affected by well known Blackfoot disease manifested by peripheral vascular gangrene. The objective of the study was to understand the role of local hydrogeology in terms of spatial variation of arsenic concentration in groundwater wells of the entire Chianan Plain and the foothill belt of the Central Mountain Range. An attempt has also been made to assess the contribution of nearby geothermal sources to the arsenic budget in groundwater of the Chianan Plain. Our study shows a gradual increase in all major and trace ion concentrations including total arsenic from foothill belt (arsenic: median = 4 μg/L, range = 0–667.6 μg/L, sample number n = 16) to coastal zones (arsenic: median = 42.74 μg/L, range = 0.14–348.6 μg/L, n = 15) of the plain. Inverse geochemical modeling shows that Ca may be exchanged on clays, and that the degree of the exchange increases from the foothill to the coastal zones. Inverse geochemical modeling further suggests that the oxidation of organic matter (CH2O) required in various east-west profiles across the plain to balance the total bicarbonate concentration and CO2 input from organic matters significantly increases from the foothill to the coastal zones with transfer coefficients ranging from 1.55 × 10−2 to 1.69 × 10−5 mol/L. High concentrations of tritium (mean = 1.33 ± 0.11 TU; n = 4) in foothill groundwater and low concentration of tritium in groundwater of central zone suggest gradually increasing water–rock interaction from the foothill to the coastal part. Few elevated arsenic (median = 171.8 μg/L, maximum = 667.60 μg/L, minimum = 24 μg/L; n = 6) hotspots are identified in the foothill belt. Available lithologs and aquifer test data suggest that the presence of impermeable clay around those pockets possibly inhibits vertical and lateral flushing of the aquifer and aids strong water–rock interactions subsequently leading to release of arsenic into groundwater. Using oxygen isotope and chloride mass balance method, we estimated that geothermal sources can recharge a maximum of 4% of groundwater in proximal aquifers and contribute <2% of average As concentration in the groundwater of Chianan Plain. Our preliminary observations thus show some arsenic enrichment in foothill aquifers, providing a necessity of detailed study of the aquifer systems in these understudied regions. Moreover, our research indicates that the contribution of arsenic from geothermal sources is insignificant, which stands in contrast to earlier studies suggesting that mud volcanoes and thermal springs in the Western Foothill Belt of the Central Mountain Range were potential sources of groundwater arsenic in the Chianan Plain aquifers.
Full-text · Article · Oct 2014 · Journal of Hydrology
[Show abstract][Hide abstract] ABSTRACT: A geochemical approach was applied to understand the factors controlling the mobilization of As and
trace elements (TEs) in mining areas of the Poopó and Antequera River sub-basins on the Bolivian
Altiplano. A total of 52 samples (surface, groundwater and geothermal water) were collected during
the rainy season (2009). Arsenic, Cd and Mn concentrations exceed World Health Organization (WHO)
drinking water guidelines and Bolivian regulations for drinking water in 28 groundwater samples, but
Cu, Ni, Pb and Zn do not. Arsenic, Cd, Mn, Pb and Zn concentrations exceed World Health Organization
guidelines for drinking water and Bolivian regulations Class A standard for discharge to water bodies
in 20 surface water samples, whereas levels of Cu do not, and Ni and Fe rarely exceed regulation and
guideline values. Factor analysis was applied to 18 hydrochemical parameters of 52 samples. Five factors
for groundwater (plagioclase weathering, dissolution of gypsum and halite, TEs mobilization at acidic pH,
sulfide oxidation, and release of As) account for 86.5% of the total variance for Antequera and 83.9% for
Poopó sub-basins. Four factors for surface water data (weathering and mobilization of TEs influenced
by pH, dissolution of evaporate salts, neutralization of acid mine drainage, and As release due to
dissolution of Mn and Fe oxides) account for 91% of the total variance in Antequera and 96% in Poopó
sub-basins. The As and TEs mobilized in these regions could affect the local water sources, which is a prevalent concern with respect to water resource management in this semi-arid Altiplano region. Presence of
both natural and anthropogenic sources of contamination requires careful monitoring of water quality.
Full-text · Article · Sep 2014 · Journal of Hydrology
[Show abstract][Hide abstract] ABSTRACT: Vanadium-rich mine tailings at Berg Aukas, site with a world-known vanadium mineralization in northeastern Namibia, were investigated using a combination of solid phase and mineralogical analyses, leaching tests and speciation modeling. Principal objective of the study was to determine, if vanadium can be released into the environment. In spite of >30 y of weathering and oxidation of tailings material to a maximum sampling depth of 2.4 m, a large portion of V still remains in the primary mineral descloizite, (Pb,Zn)2(OH)VO4. A part of V was mobilized and adsorbed/co-precipitated with ferric oxyhydroxides. Based on sequential extraction and 57Fe Mössbauer spectroscopy, a large amount of ferric iron is present in insoluble hematite and goethite, where V is effectively bound. Other potential contaminants are Zn, present mostly in the primary mineral willemite, Zn2SiO4, descloizite and also in secondary smithsonite, ZnCO3; and Pb, which was transferred from completely dissolved galena to cerussite, PbCO3 and is also partly present in primary descloizite. Conditions in the mine tailings are alkaline (pH generally >8.2) and oxidizing during dry period, but mobility of V is low due to low solubility of descloizite and secondary crystalline ferric phases such as hematite. In contrast, Zn and especially Pb in secondary carbonates, probably represent more serious environmental and health risks.
No preview · Article · Aug 2014 · Journal of African Earth Sciences
[Show abstract][Hide abstract] ABSTRACT: Exploitation of groundwater from shallow, high prolific Holocene sedimentary aquifers has been a main element for achieving safe drinking water and food security in Bangladesh. However, the presence of elevated levels of geogenic arsenic (As) in these aquifers has undermined this success. Except for targeting safe aquifers through installations of tubewells to greater depth, no mitigation option has been successfully implemented on a larger scale. The objective of this study has been to characterise the hydrostratigraphy, groundwater flow patterns, the hydraulic properties to assess the vulnerability of low-arsenic aquifers at Matlab, in south-eastern Bangladesh, one of the worst arsenic-affected areas of the country. Groundwater modelling, conventional pumping test using multilevel piezometers, hydraulic head monitoring in piezometer nests, 14C dating of groundwater and assessment of groundwater abstraction were used. A model comprising of three aquifers covering the top 250 m of the model domain showed the best fit for the calibration evaluation criteria. Irrigation wells in the Matlab area are mostly installed in clusters and account for most of the groundwater abstraction. Even though the hydraulic heads are affected locally by seasonal pumping, the aquifer system is fully recharged from the monsoonal replenishment. Groundwater simulations demonstrated the presence of deep regional flow systems with recharge areas in the eastern, hilly part of Bangladesh and shallow small local flow systems driven by local topography. Based on modelling results and 14C groundwater data, it can be concluded that the natural local flow systems reach a depth of 30 m b.g.l. in the study area. A downward vertical gradient of roughly 0.01 down to 200 m b.g.l. was observed and reproduced by calibrated models. The vertical gradient is mainly the result of the aquifer system and properties rather than abstraction rate, which is too limited at depth to make an imprint. Although irrigation wells substantially change local flow pattern, targeting low-As aquifers seems to be a suitable mitigation option for providing people with safe drinking water. However, installing additional irrigation- or high capacity production wells at the same depth is strongly discouraged as these could substantially change the groundwater flow pattern. The results from the present study and other similar studies can further contribute to develop a rational management and mitigation policy for the future use of the groundwater resources for drinking water supplies.
No preview · Article · Jun 2014 · Journal of Hydrology
[Show abstract][Hide abstract] ABSTRACT: The mine tailings at Kombat, in semiarid northeastern Namibia, were investigated by the combination of solid-phase analyses, mineralogical methods, leaching tests, and speciation modeling. Dissolution of the most abundant primary sulfides, chalcopyrite and galena, released copper and lead which were adsorbed onto ferric oxyhydroxides or precipitated in the form of malachite, Cu2CO3(OH)2, and cerussite, PbCO3, respectively. Arsenic released from arsenopyrite was incorporated into ferric oxyhydroxides. Based on sequential extraction and (57)Fe Mössbauer spectroscopy, a large amount of ferric iron is present as low solubility hematite and goethite formed rapidly (<10 years) under warm semiarid climatic conditions, and arsenic in these phases is relatively tightly bound. It seems that Cu and especially Pb in carbonate minerals represent a more serious environmental risk. Immobilization of As in hematite has implications for other mining sites in regions with similar climatic conditions because this process results in long-term immobilization of As.
No preview · Article · Apr 2014 · Environmental Monitoring and Assessment
[Show abstract][Hide abstract] ABSTRACT: Purpose Whereas mercury (Hg) has been extensively studied in gold mining areas (including artisanal mining), it is often overlooked as a minor contaminant in these districts, within which industrial base-metal mining and smelting are in operation. The aims of this study were to investigate Hg in tropical soils from mining and smelting areas in Namibia and Zambia and to apply statistical methods to generate models for the prediction of Hg concentrations in the soils studied. Materials and methods Twenty-one soil profiles (n = 159 soil samples) were collected in metal mining districts in the northern parts of Namibia (Tsumeb, Berg Aukas, Kombat) and in the Zambian Copperbelt (Kitwe, Mufulira). Total Hg was analysed by atomic absorption spectrometry and compared statistically with other physico-chemical and chemical soil parameters. Mercury concentrations in potential sources (feed and wastes from smelters as well as mine tailings, n = 35) were also determined. Results and discussion Mercury concentrations in soils from mining/smelting areas were significantly higher in northern Namibia (range 0.0038–4.39, mean 0.39, median 0.02 mg kg−1) than in the Zambian Copperbelt (range 0.0055–0.39, mean 0.02, median 0.01 mg kg−1). This phenomenon is related to the higher levels of Hg in the mine tailing materials as well as the feed/wastes from the smelters in Namibia (specifically in Berg Aukas and Tsumeb). Only 27 % (Namibia) and 26 % (Zambia) of the soil samples exceeded geochemical anomaly thresholds (0.033 and 0.016 mg kg−1, respectively), generally indicating a low Hg pollution level. The highest Hg concentrations were observed in the uppermost soil layers. Total Hg correlated significantly with other contaminants and, in the Zambian dataset, also with Corg and Stot. Conclusions Based on measurements of total Hg in soils from the mining/smelting areas in Namibia and Zambia, only one fourth of the samples exceeded geochemical anomaly thresholds, and they indicated a relatively low level of Hg pollution. Elevated Hg concentrations were only observed in topsoils in the immediate vicinities of mine tailings and active smelters. Constructed regression models were found to be useful for prediction of Hg concentrations at both of the regions studied.
Full-text · Article · Mar 2014 · Journal of Soils and Sediments
[Show abstract][Hide abstract] ABSTRACT: The concentrations of arsenic (As), copper (Cu), cobalt (Co), lead (Pb) and zinc (Zn) in washed leaves and washed and peeled tubers of cassava (Manihot esculenta Crantz, Euphorbiaceae) growing on uncontaminated and contaminated soils of the Zambian Copperbelt mining district have been analyzed. An enrichment index (EI) was used to distinguish between contaminated and uncontaminated areas. This index is based on the average ratio of the actual and median concentration of the given contaminants (As, Co, Cu, mercury (Hg), Pb and Zn) in topsoil. The concentrations of copper in cassava leaves growing on contaminated soils reach as much as 612 mg kg−1 Cu (total dry weight [dw]). Concentrations of copper in leaves of cassava growing on uncontaminated soils are much lower (up to 252 mg kg−1 Cu dw). The concentrations of Co (up to 78 mg kg−1 dw), As (up to 8 mg kg−1 dw) and Zn (up to 231 mg kg−1 dw) in leaves of cassava growing on contaminated soils are higher compared with uncontaminated areas, while the concentrations of lead do not differ significantly. The concentrations of analyzed chemical elements in the tubers of cassava are much lower than in its leaves with the exception of As.
No preview · Article · Mar 2014 · Journal of African Earth Sciences
[Show abstract][Hide abstract] ABSTRACT: A survey of groundwater from six geothermal springs in Namibia showed high concentrations of dissolved fluoride, with values up to 18.9 mg/l. All values are higher than both the WHO limit and the Namibian guideline. High concentrations of fluoride are linked to Na-HCO3 or Na-SO4-HCO3 groundwater types, with increasing sulphate and chloride concentrations towards the south of Namibia. Values of δ2H and δ18O are more negative for the north of the country, and with increasing altitude of springs and distance from precipitation sources towards the southeast from the Indian Ocean. A shift of about 1‰ from the LMWL for Windhoek was observed for δ18O samples, which was probably caused by the exchange with reservoir rocks. Values of δ34S(SO4) reflect mixing of two principal sulphate sources, i.e., dissolution of gypsum originating from playas and interaction with sulphidic mineralization in tectonic bedrock zones. Values of δ13C(DIC) seem to be affected by a variable vegetation cover and mainly by the input of endogenous CO2. Estimated reservoir temperatures vary from 60 °C to 126 °C, with a maximum value at the Ganigobes site. The geothermal springs of Namibia in this study do not meet drinking water standards and thus their water can be used only for other purposes e.g. for thermal spas. Treatment would be necessary to decrease dissolved fluorine concentrations for drinking water purposes.
No preview · Article · Jan 2014 · Journal of Geochemical Exploration
[Show abstract][Hide abstract] ABSTRACT: Mining wastes of Zn-Pb ores were studied at Olkusz, Southern Poland, using X-ray diffraction, SEM/EDS analyses. Additionally the chemistry of surface water runoff collected on the tailings slope was analyzed. The surface layer of tailing piles contains pyrite and marcasite, and dolomite as predominant carbonate mineral. The principal secondary sulfate mineral is gypsum, but the presence of trace epsomite was also inferred. Grains of dolomite are relatively fresh: the source of Ca necessary for crystallization of gypsum seems to be highly corroded minor calcite. In surface runoff, pH is close to neutral; Ca and sulfate are the dominant ions, followed by Mg. Concentrations of sulfate reaches 939 mg/l, whereas concentrations of Ca and Mg are 389 mg/l and 15.43 mg/l, respectively. The principal heavy metal in runoff is Zn, reaching 2.65 mg/l. Most species in runoff exhibited a negative correlation with the amount of precipitation in 5 days preceding the formation of surface runoff, due to their presence in efflorescent salts precipitated in dry period. Bicarbonate showed a positive correlation with the amount of precipitation, probably due to enhanced dissolution of calcite under high water saturation conditions. The results of this study indicate a dominant role of the surface layer of tailings and previous precipitation conditions in the formation of the surface runoff chemistry. In the future, surface runoff and fast releases of contaminants may become more important as a consequence of on-going climatic changes resulting in higher intensity of storm events.