Mercury pollution caused by artisanal gold mining the Ocoña river Valley, Peru

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The Campo de Calatrava volcanic field: geology and resources.

The volcanic region of Campo de Calatrava, located in South-Central Spain, and in particular in the Ciudad Real Province (Castilla-La Mancha region) is one of the three most important areas with recent volcanic activity in the Iberian Peninsula, together with those of Olot (Gerona, in Catalonia) and Cabo de Gata (Almeria, in Andalucía). In this work we describe succinctly the characteristics of this volcanism, as well as the related iron and manganese (plus minor cobalt) oxides mineralizations. Finally, an also brief description of the legal measures implemented to protect the local volcanic buildings is included

The use of mercury for gold recovering in the artisanal gold mining from the Mapiri river basin, Apolobamba, Bolivia

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Environmental pollution produced by gold artisanal mining in the Mapiri river basin, Apolobamba, Bolivia

Mining activity is very important in Bolivia since colonial times. Today it has been reactivated, especially gold mining, due to rise in metal prices. Artisanal and small-scale mining activities are abundant in the protected area of Apolobamba, near the border with Peru. Here mercury is used to recovery gold by obtaining an Hg-Au amalgam. This manipulation with mercury causes an important environmental impact in the area. The present work is a preliminary study of the contamination of the Mapiri river basin in the Apolobamba area. In the head of this basin, located at more than 4000 m above sea level, gold is mined from hydrothermal gold deposits of Paleozoic age. We have sampled several mining sites from this area, in particular the ones known as Viscachani, Flor de Mayo and Chojlaya, located in the proximity of the head area of the Mapiri river basin. These mining sites were in activity during the present sampling campaign. Different metals were measured by means of XRF (Se, As, Cu, Zn, Cd, Pb, Hg) in tailing samples from the different gold mining sites. In addition mercury concentrations were measured in water and in vegetation close to the processing areas by means of atomic absorption spectrometry with Zeeman effect (LUMEX RA-915 Equipment). Tailings are mainly constituted by quartz with minor contents of clay minerals and sulphides. The most abundant sulphides are galena and arsenopyrite. Chalcopyrite, sphalerite, pyrite and sulphosalts also occur in minor amounts, as well as minor secondary minerals. Gold content, after recovery with mercury, is high, between 4.56 ppm and 10.35 ppm. The Hg content of the tailings ranges from 149 to 1027 ppm. Lixiviable mercury from these samples ranges between 30.10 and 859.94 ng l-1. Water released from the tailings contains between 0.1 and 5.7 ppb of Hg. Studied vegetation typical of the area has high Hg contents, between 162 and 219 ppm. In addition there is a high arsenic content in all the studied tailings, except in those from the Viscachani mining site, where concentrations of this element ranges from 456 ppm to 18540 ppm. The Pb content usually ranges from 337 to 939 ppm. The Chojlaya mining site tailing has exceptionally high values of heavy metals: Pb content is between 2.26 and 3.27 wt.%, Cd ranges from 160 to 228 ppm, Zn from 194 to 794 ppm, Cu from 847 to 1052 ppm and Se from 105 to 187 ppm. These contents also contribute to an environmental pollution. In conclusion the gold mining activities in the Mapiri river basin produce and intense environmental pollution, mainly related to mercury and arsenic contents in the proximity of these mining activities. After processing, tailings still contain important amounts of gold suggesting that the amalgamation method is not effective to gold recovering.Peer ReviewedPostprint (published version

Mercury emission and dispersion models from soils contaminated by cinnabar mining and metallurgy.

The laboratory flux measurement system (LFMS) and dispersion models were used to investigate the kinetics of mercury emission flux (MEF) from contaminated soils. Representative soil samples with respect to total Hg concentration (26?9770 mg g 1) surrounding a decommissioned mercury-mining area (Las Cuevas Mine), and a former mercury smelter (Cerco Metal urgico de Almadenejos), in the Almad en mercury mining district (South Central Spain), were collected. Altogether, 14 samples were analyzed to determine the variation in mercury emission flux (MEF) versus distance from the sources, regulating two major environmental parameters comprising soil temperature and solar radiation. In addition, the fraction of the water-soluble mercury in these samples was determined in order to assess how MEF from soil is related to the mercury in the aqueous soil phase. Measured MEFs ranged from less than 140 to over 10 000 ng m 2 h 1, with the highest emissions from contaminated soils adjacent to point sources. A significant decrease of MEF was then observed with increasing distance from these sites. Strong positive effects of both temperature and solar radiation on MEF was observed. Moreover, MEF was found to occur more easily in soils with higher proportions of soluble mercury compared to soils where cinnabar prevails. Based on the calculated Hg emission rates and with the support of geographical information system (GIS) tools and ISC AERMOD software, dispersion models for atmospheric mercury were implemented. In this way, the gaseous mercury plume generated by the soil originated emissions at different seasons was modeled. Modeling efforts revealed that much higher emissions and larger mercury plumes are generated in dry and warm periods (summer), while the plume is smaller and associated with lower concentrations of atmospheric mercury during colder periods with higher wind activity (fall). Based on the calculated emissions and the model implementation, yearly emissions from the ??Cerco Metal urgico de Almadenejos?? decommissioned metallurgical precinct were estimated at 16.4 kg Hg y 1, with significant differences between seasons

Mercury emissions in equilibrium: a novel approach for the quantification of mercury emissions from contaminated soils.

Mercury emissions from soil samples with different mercury contents have been estimated using a closed circuit array. The samples were collected from the Almaden mercury mining district. The emissions confirmed that temperature and light radiation favour mercury desorption due to the increase in the mercury vapour pressure. An additional positive factor could be the photocatalytic reduction of soluble Hg2+ to volatile Hg0 at the soil surface. A physicochemical model based on mass transfer and equilibrium was developed and was used to reproduce the mercury emissions at the laboratory scale. The use of this model allowed us to obtain the unknown mass transfer coeficient (KL) and adsorption parameters required to quantify the possible gaseous mercury fluxes from these contaminated soils. Experimental results indicate that an equilibrium between the solid and gas phases was established. The proposed kinetic model reproduced perfectly the experimental data, with KL found to be proportional to the inverse of temperature and independent of the radiation. The concentration of mercury in the gas phase was mainly dependent on the soluble mercury content (HgS). Equilibrium data were #64257;tted by Langmuir and Freundlich models and the best fit was obtained using the multi-layer model attending to the convex shape of the curves, which is characteristic of non-porous or possibly macroporous materials having a low adsorption energy. The Freundlich constant (KF) was also fitted as a polynomial function with temperature and this gave a straight line for the light radiation and a second grade equation for dark conditions. Once the parameters had been obtained, the Hg emission fluxes from contaminated soils were estimated and the values were between two and three orders of magnitude higher than those published in the literature for non-contaminated soils

Intraplate mafic magmatism, degasification, and deposition of mercury: the giant Almadén mercury deposit (Spain) revisited

The giant Almadén mercury deposit (Spain) is hosted by the Lower Silurian Criadero Quartzite; in turn this ore-bearing rock unit is cross-cut by the so-called Frailesca unit, a diatreme body of basaltic composition. The geochemical characteristics of the Silurian to Devonian Almadén District volcanic units indicate that these rocks originated from an enriched, evolving mantle source that ultimately yielded basanites?nephelinites to yolites, through olivine-basalts, pyroxene-basalts, trachybasalts, trachytes, very scarce rhyolites, and quartzdiabases. The Silurian intraplate alkaline volcanism developed in submarine conditions which triggered widespread hydrothermal activity resulting in Hg ore formation and pervasive alteration to carbonates. The #948;18O, #948;13C, and #948;34S isotopic signatures for carbonates and pyrite suggest different sources for carbon and sulfur, including magmatic and organic for the former and magmatic and sea water for the latter. The most important and efficient natural source of mercury on Earth is by far the volcanic activity, which liberates mercury via quiescent degassing and catastrophic (Plinian) events when eruptions can overwhelm the atmospheric budget of Hg. Thus, we suggest that CO2 degasification and coeval distillation of mercury from the volcanic rocks fed the huge hydrothermal system that led to massive deposition of mercury at Almadén. Build up of Hg0 gas in magmatic chambers during waning rifting in the Late Ordovician, followed by renewed volcanism in the Early Silurian, would have resulted in massive degasification of the accumulated mercury. Part of this mercury went into the Criadero Quartzite leading to formation of the huge Almadén deposit and others (e.g., El Entredicho) along the same stratigraphic level. Progressive depletion of the deep seated magmatic Hg stock would have resulted in a drastic reduction in ore deposit size after the Lower Silurian when smaller deposits formed (e.g., Las Cuevas)

Evaluación de la contaminación de mercurio en La Cuenca del rio Ocoña, Perú

En el departamento de Arequipa, sur del Perú, se localiza la cuenca del rio Ocoña, donde se encuentran diferentes asentamientos mineros artesanales. En esta zona se explota el oro. La recuperación del metal precioso se realiza mediante amalgamación con mercurio, en algunos casos utilizando retortas y en otros en las propias cases. La utilización de éste se realiza sin medidas de protección lo que produce una contaminación al medio ambiente de toda la zona. Mediante este trabajo se realizó una evaluación de la contaminación producida por el uso del mercurio en la cuenca del río Ocoña. Para ello, se han obtenido un total de 12 muestras de agua procedentes de diferentes lugares de la cuenca. Además se han analizado 3 muestras de plantes y sus suelos y 20 de cabellos humanos, correspondientes a habitantes de la población de Misky.Postprint (published version

Mercury vapours emissions from the ingenios in Potosí (Bolivia).

Potosí (South West Bolivia) is a well known historical mining site in the world, with mining activity centered at the so-called Cerro Rico. It is an impressive mount formed by rhyolitic rocks affected by intensive hydrothermal alteration, and hosting a complex vein deposit including mainly Ag and Sn minerals. From the start of the mining activity, in the late 16th century, to 1850, the main ore was silver minerals, and from 1850 the silver ores exhausted, and mining activity centered on tin minerals. During the first stage, the silver minerals were treated by amalgamation, using the so-called ?método de patio?, which implied the usage of mercury and other compounds as metallurgical agents, and supposed the release of important quantities of mercury to the local environment. This work was carried out at the ?ingenios?, milling and mercury processing facilities located next to streams, in order to have the water and mechanical energy needed for the process, and nowadays in ruins. Our results put forward very low mercury vapor concentrations in the region, reaching only occasionally values over 4 ng m#8722;3, as well as in the town area, were maximum values reach 31 ng m#8722;3 with an average of 5.5 ng m3; detailed surveys at the \Ingenios\ demonstrated that in these facilities mercury vapor concentrations were also low, but the excavation of the topsoil causes an important release of the elemental vapor, reaching concentrations over 3000 ng m3. Causes of this low emission of unmodified soil are here interpreted as caused by biological and physicochemical transformation of the metallic mercury accumulated in the soil, to mineral phases such as cinnabar/metacinnabar and/or schuetteite, in reactions mediated by the formation of methylmercury