In Vitro Studies Evaluating Leaching of Mercury from Mine Waste Calcine Using Simulated Human Body Fluids

In vitro bioaccessibility (IVBA) studies were carried out on samples of mercury (Hg) mine-waste calcine (roasted Hg ore) by leaching with simulated human body fluids. The objective was to estimate potential human exposure to Hg due to inhalation of airborne calcine particulates and hand-to-mouth ingestion of Hg-bearing calcines. Mine waste calcines collected from Hg mines at Almadén, Spain, and Terlingua, Texas, contain Hg sulfide, elemental Hg, and soluble Hg compounds, which constitute primary ore or compounds formed during Hg retorting. Elevated leachate Hg concentrations were found during calcine leaching using a simulated gastric fluid (as much as 6200 μg of Hg leached/g sample). Elevated Hg concentrations were also found in calcine leachates using a simulated lung fluid (as much as 9200 μg of Hg leached/g), serum-based fluid (as much as 1600 μg of Hg leached/g), and water of pH 5 (as much as 880 μg of Hg leached/g). The leaching capacity of Hg is controlled by calcine mineralogy; thus, calcines containing soluble Hg compounds contain higher leachate Hg concentrations. Results indicate that ingestion or inhalation of Hg mine-waste calcine may lead to increased Hg concentrations in the human body, especially through the ingestion pathway

Isotopic Variability of Mercury in Ore, Mine-Waste Calcine, and Leachates of Mine-Waste Calcine from Areas Mined for Mercury

The isotopic composition of mercury (Hg) was determined in cinnabar ore, mine-waste calcine (retorted ore), and leachates obtained from water leaching experiments of calcine from two large Hg mining districts in the U.S. This study is the first to report significant mass-dependent Hg isotopic fractionation between cinnabar ore and resultant calcine. Data indicate that δ202Hg values relative to NIST 3133 of calcine (up to 1.52‰) in the Terlingua district, Texas, are as much as 3.24‰ heavier than cinnabar (−1.72‰) prior to retorting. In addition, δ202Hg values obtained from leachates of Terlingua district calcines are isotopically similar to, or as much as 1.17‰ heavier than associated calcines, most likely due to leaching of soluble, byproduct Hg compounds formed during ore retorting that are a minor component in the calcines. As a result of the large fractionation found between cinnabar and calcine, and because calcine is the dominant source of Hg contamination from the mines studied, δ202Hg values of calcine may be more environmentally important in these mined areas than the primary cinnabar ore. Measurement of the Hg isotopic composition of calcine is necessary when using Hg isotopes for tracing Hg sources from areas mined for Hg, especially mine water runoff

El complejo volcánico cerros Bravos, región de Maricunga, Chile: Geología, alteración hidrotermal y mineralización

El Complejo Volcánico Cerros Bravos (Oligoceno-Mioceno) es un conjunto de lavas y domos dacítico-andesíticos calcoalcalinos de gran extensión (450 km2) ubicado a unos 140 km al este de Copiapó, Chile, que integra la Franja de Maricunga, cadena volcánica neógena que representa un arco pluto-volcánico de margen continental. Los análisis radiométricos K-Ar señalan que el complejo volcánico Cerros Bravos estuvo activo entre los 26-18 Ma (Oligoceno-Mioceno inferior) en tanto que el complejo La Coipa registra actividad hasta el Mioceno medio (15 Ma), y desde allí hacia el sur los centros volcánicos presentan edades entre 16 y 6 Ma. El complejo hospeda la zona de alteración hidrotermal del Prospecto Esperanza, sistema epitermal del tipo sulfato-ácido con mineralización de oro y plata controlada estructuralmente y asociada a una intensa silicificación y argilización con calcolinita, alunita y jarosita, con edades radiométricas K-Ar entre 20-18 Ma. Los estudios isotópicos de Pb realizados en rocas y sulfuros de los depósitos de la Franja de Maricunga indican que las rocas ígneas del Oligoceno-Mioceno son una mezcla de manto subcortical máfico o material cortical y material cortical radiogénico. El Pb en los depósitos de metales preciosos de la franja es dominado por una fuente como las rocas ígneas huéspedes y, localmente, otras rocas huéspedes (sedimentarias triásicas) pueden haber contribuido con Pb durante la circulación hidrotermal en ambiente cercano a la superficie. La aplicación de las metodologías de la teledetección en imágenes Landsat TM en la zona de Maricunga demostró ser una herramienta eficaz para la exploración ya que permitió destacar perfectamente las zonas de alteración hidrotermal presentes en el área y la elaboración de mapas de alta confiabilidad a escala regional

Mercury Contamination from Hydraulic Placer-Gold Mining in the Dutch Flat Mining District, California

Mercury contamination at historic gold mining sites represents a potential risk to human health and the environment. Elemental mercury (quicksilver) was used extensively for the recovery of gold at both placer and hardrock mines throughout the western United States. In placer mine operations, loss of mercury during gold recovery was reported to be as high as 30 percent. In the Dutch Flat mining district located in the Sierra Nevada region of California, placer mines processed more than 100,000,000 cubic yards of gold-bearing gravel. The placer ore was washed through mercury-charged ground sluices and drainage tunnels from 1857 to about 1900, during which time many thousands of pounds of mercury were released into the environment. Mine waters sampled in 1998 had total unfiltered mercury concentrations ranging from 40 ng/L (nanograms per liter) to 10,400 ng/L, concentrations of unfiltered methyl mercury ranged from 0.01 ng/L to 1.12 ng/L. Mercury concentrations in sluice-box sediments ranged from 600 μg/g (micrograms per gram) to 26,000 μg/g, which is in excess of applicable hazardous waste criteria (20 μg/g). These concentrations indicate that hundreds to thousands of pounds of mercury may remain at sites affected by hydraulic placergold mining. Elevated mercury concentrations have been detected previously in fish and invertebrate tissues downstream of the placer mines. Extensive transport of remobilized placer sediments in the Bear River and other Sierra Nevada watersheds has been well documented. Previous studies in the northwesternSierra Nevada have shown that the highest average levels of mercury bioaccumulation occur in the Bear and South Fork Yuba River watersheds; this study has demonstrated a positive correlation of mercury bioaccumulation with intensity of hydraulic gravel mining

Isotope geochemistry of mercury in source rocks, mineral deposits and spring deposits of the California Coast Ranges, USA

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155673/1/Smith_et_al_2008_Isotope_geochemistry.pd

A PROBABILISTIC DECISION ANALYTICAL APPROACH FOR WATERSHED PLANNING: A MERCURY TOTAL MAXIMUM DAILY LOAD CASE STUDY

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