Papers by Christian Wisskirchen
Journal of the American Society of Mining and Reclamation, Jun 30, 2006
A study of an acidic lake (pH ~1) resulting from the deposition of copper leaching spoil waters a... more A study of an acidic lake (pH ~1) resulting from the deposition of copper leaching spoil waters and acid mine drainage of the Zn-Pb (-Ag-Bi-Cu) deposit Cerro de Pasco is presented. The data shows for the lake water concentration ranges and mean values of 1440-7180 (4330) mg/L Fe, 33.5-105 (87) mg/L Cu, 180-746 (493) mg/L Zn, 13-63 (48) mg/L As, 2.2-5.3 (2.9) mg/L Pb, 11205-42300 (29250) mg/L SO 4 −2 and an acidity of 14480-21440 (16775) mg/L CaCO 3. Lake water mean values did not differ significantly from values measured for discharge water. Within the lake water body most element concentrations increased with water depth. Infiltrated acidic waters dissolved the limestone bedrock under formation of argillaceous gypsum, overlying dissolving calcite. In the precipitating gel-like matter and upper parts of dissolved bedrock, heavy metals enriched in composition to the lake water. X-ray fluorescence data show for this kind of sediment concentration ranges and mean values of 0.76-12.38 (5,98) wt% Fe 2 O 3 , 51-3980 (1301) mg/kg Cu, 275-8034 (3822) mg/kg Zn, 43-5781 (898) mg/kg As, 21-1310 (261) mg/kg Pb, 0.7-11 (6.2) wt% S. Heavy metals are most likely fixed by organic matter (15 wt% TOC) in form of chelate complexes. The high amounts of organic carbon in the upper part of the sediments most likely results from the discharged spoil waters of the Cu extraction plant. Hydroxides formed during first steps of the infiltration of the bedrock dissolve during later steps of the lake water bedrock interaction.
From 1926 until 1975, the Potrerillos-El Salvador mining district (porphyry copper deposits) sent... more From 1926 until 1975, the Potrerillos-El Salvador mining district (porphyry copper deposits) sent most of its flotation tailings in suspension through the El Salado River directly to the sea at the Chanaral Bay, Atacama desert, Chile. Over 220 Mt of tailings, containing between 1-2 wt% pyrite, have been dumped into the bay, resulting in a displacement of the shore line over one kilometer further out to the sea. The tailings are estimated to be 10-15 m thick, covering an area of 4.5 km. The hydrology of the tailings system is controlled by a groundwater infiltration of highly saline water (up to 60 g/L Cl and 30 g/L Na) and the tidal cycle. Data suggests that low- saline water (up to 0.9 mg/L Cl and 0.8 mg/L Na), possibly from the municipally water supply or an unknown source, infiltrated into the tailings system. Oxidation resulted in a 70 to 188 cm thick low-pH (0.8 - 4) oxidation zone at the top, which is characterized by jarosite and unidentified orange-brown Fe(III) hydroxides a...
Applied Geochemistry, 2010
Acid mine drainage (AMD) from the Zn-Pb(-Ag-Bi-Cu) deposit of Cerro de Pasco (Central Peru) and w... more Acid mine drainage (AMD) from the Zn-Pb(-Ag-Bi-Cu) deposit of Cerro de Pasco (Central Peru) and waste water from a Cu-extraction plant has been discharged since 1981 into Lake Yanamate, a natural lake with carbonate bedrock. The lake has developed a highly acidic pH of $1. Mean lake water chemistry was characterized by 16,775 mg/L acidity as CaCO 3 , 4330 mg/L Fe and 29,250 mg/L SO 4. Mean trace element concentrations were 86.8 mg/L Cu, 493 mg/L Zn, 2.9 mg/L Pb and 48 mg/L As, which did not differ greatly from the discharged AMD. Most elements showed increasing concentrations from the surface to the lake bottom at a maximal depth of 41 m (e.g. from 3581 to 5433 mg/L Fe and 25,609 to 35,959 mg/L SO 4). The variations in the H and O isotope compositions and the element concentrations within the upper 10 m of the water column suggest mixing with recently discharged AMD, shallow groundwater and precipitation waters. Below 15 m a stagnant zone had developed. Gypsum (saturation index, SI $ 0.25) and anglesite (SI $ 0.1) were in equilibrium with lake water. Jarosite was oversaturated (SI $ 1.7) in the upper part of the water column, resulting in downward settling and re-dissolution in the lower part of the water column (SI $ À0.7). Accordingly, jarosite was only found in sediments from less than 7 m water depth. At the lake bottom, a layer of gel-like material ($90 wt.% water) of pH $1 with a total organic C content of up to 4.40 wet wt.% originated from the kerosene discharge of the Cu-extraction plant and had contaminant element concentrations similar to the lake water. Below the organic layer followed a layer of gypsum with pH 1.5, which overlaid the dissolving carbonate sediments of pH 5.3-7. In these two layers the contaminant elements were enriched compared to lake water in the sequence As < Pb % Cu < Cd < Zn = Mn with increasing depth. This sequence of enrichment was explained by the following processes: (i) adsorption of As on Fe-hydroxides coating plant roots at low pH (up to 3326 mg/kg As), (ii) adsorption at increasing pH near the gypsum/calcite boundary (up to 1812 mg/kg Pb, 2531 mg/kg Cu, and 36 mg/kg Cd), and (iii) precipitation of carbonates (up to 5177 mg/kg Zn and 810 mg/kg Mn; all data corrected to a wet base). The infiltration rate was approximately equal to the discharge rate, thus gypsum and hydroxide precipitation had not resulted in complete clogging of the lake bedrocks.
For operations and closure planning, understanding lag times to the potential development of acid... more For operations and closure planning, understanding lag times to the potential development of acidic conditions is critical for management of a tailing storage facility (TSF). While this is important for many mines, for the site presented herein (and similar projects) the climatic and hydraulic conditions expected for TSFs in the extreme arid climate of the Atacama Desert present specific challenges for prediction of lag times to acidic conditions and subsequent metals leaching. Long term humidity cell testing (up to 151 total cycles) was undertaken for several fractions of pilot plant tailings for a copper porphyry deposit. Modified humidity cell tests were also utilized with weekly cycles of humid and dry air and rinses every 20 cycles. The delayed rinse cells were used to provide insight for conditions where wetting of tailings will occur very infrequently following deposition. Tailings evaluated had total sulfur contents near 1.0% and low neutralization potential. While predicted...
Applied Geochemistry, 2010
Acid mine drainage (AMD) from the Zn-Pb(-Ag-Bi-Cu) deposit of Cerro de Pasco (Central Peru) and w... more Acid mine drainage (AMD) from the Zn-Pb(-Ag-Bi-Cu) deposit of Cerro de Pasco (Central Peru) and waste water from a Cu-extraction plant has been discharged since 1981 into Lake Yanamate, a natural lake with carbonate bedrock. The lake has developed a highly acidic pH of $1. Mean lake water chemistry was characterized by 16,775 mg/L acidity as CaCO 3 , 4330 mg/L Fe and 29,250 mg/L SO 4 . Mean trace element concentrations were 86.8 mg/L Cu, 493 mg/L Zn, 2.9 mg/L Pb and 48 mg/L As, which did not differ greatly from the discharged AMD. Most elements showed increasing concentrations from the surface to the lake bottom at a maximal depth of 41 m (e.g. from 3581 to 5433 mg/L Fe and 25,609 to 35,959 mg/L SO 4 ). The variations in the H and O isotope compositions and the element concentrations within the upper 10 m of the water column suggest mixing with recently discharged AMD, shallow groundwater and precipitation waters. Below 15 m a stagnant zone had developed. Gypsum (saturation index, SI $ 0.25) and anglesite (SI $ 0.1) were in equilibrium with lake water. Jarosite was oversaturated (SI $ 1.7) in the upper part of the water column, resulting in downward settling and re-dissolution in the lower part of the water column (SI $ À0.7). Accordingly, jarosite was only found in sediments from less than 7 m water depth. At the lake bottom, a layer of gel-like material ($90 wt.% water) of pH $1 with a total organic C content of up to 4.40 wet wt.% originated from the kerosene discharge of the Cu-extraction plant and had contaminant element concentrations similar to the lake water. Below the organic layer followed a layer of gypsum with pH 1.5, which overlaid the dissolving carbonate sediments of pH 5.3-7. In these two layers the contaminant elements were enriched compared to lake water in the sequence As < Pb % Cu < Cd < Zn = Mn with increasing depth. This sequence of enrichment was explained by the following processes: (i) adsorption of As on Fe-hydroxides coating plant roots at low pH (up to 3326 mg/kg As), (ii) adsorption at increasing pH near the gypsum/calcite boundary (up to 1812 mg/kg Pb, 2531 mg/kg Cu, and 36 mg/kg Cd), and (iii) precipitation of carbonates (up to 5177 mg/kg Zn and 810 mg/kg Mn; all data corrected to a wet base). The infiltration rate was approximately equal to the discharge rate, thus gypsum and hydroxide precipitation had not resulted in complete clogging of the lake bedrocks.
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Papers by Christian Wisskirchen