Hydrothermal arsenic enrichment in an active mountain belt: Southern Alps, New Zealand

Horton, Travis W.; Becker, J. A.; Craw, Dave; Koons, P. O.; Chamberlain, C. Page

doi:10.1016/s0009-2541(00)00416-2

Cited by 24 publications

(11 citation statements)

References 41 publications

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“…Numerous studies have been reported about the hydrothermal alteration of rocks especially in the context of ore genesis, characterization and formation (Aiuppa et al, 2006;Allen and Hahn, 1994;Halbach et al, 1993;Horton et al, 2001;Huston et al, 1995;Ostwald and England, 1977). Also, several authors have studied the evolution of toxic elements including As and heavy metals from mine pit lakes that are in contact with hydrothermally altered rock (Davis and Ashenberg, 1989;Davis et al, 2006;Eary, 1998;Levy et al, 1997;Savage et al, 2009;Tempel et al, 2000), but studies regarding the leaching behavior and release mechanisms of As from excavated altered rocks and the parameters that control these mechanisms are still lacking in the 4 literature.…”

Section: Introductionmentioning

confidence: 99%

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Tabelin

Igarashi

Takahashi

2012

Applied Geochemistry

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This paper describes the mobilization and speciation of arsenic (As) found in hydrothermally altered rock under oxic column conditions. The altered rock sample was obtained from a tunnel project located in the Nakakoshi area of Hokkaido, Japan, whose geology is represented by slate, shale and sandstone. This area underwent silicification, pyritization and argillic alteration resulting in the As-enrichment of the rock.Results of the column experiments show that the infiltration rate, bulk density and rock bed thickness affected the duration of water residence, which in turn influenced the pH of the rock-water system. Coexisting ions most notably calcium (Ca 2+) at amounts greater than ca. 50 mg/L retarded the mobilization of As. Mobilization of As from the rock with time occurred in two stages: stage 1 (weeks 1 -20) with higher As leaching and stage 2 (weeks 20 -76) characterized by nearly constant As release. In addition, pore water As concentrations revealed that the columns developed into two regions: the top half where most of the leaching occurred and the bottom part dominated by adsorption. Thus, the mechanisms controlling the mobilization of As from the rock is a combination of one or more of the following processes: dissolution of soluble As-bearing fractions, pyrite oxidation and adsorption reactions. Arsenite (As [III]) was the dominant species in the effluent at the start of the experiment in columns with shorter water residence time and lower pH conditions (< 8). On the other hand, arsenate (As[V]) was the major inorganic species released from the rock at higher pH (8 -9.5) and when the system was close to equilibrium. Speciation of As with depth also indicated that As[III] disappeared around the bottom half of the columns, probably as a result of adsorption and/or oxidation. Arsenic speciation is partially controlled by the pH dependent adsorption of As species. The important adsorbent phases in the rock included Fe-Al oxides/oxyhydroxides, clay minerals and organic matter, which permitted the columns to attenuate additional As loadings including As [III]. Implications of these results on the design of a novel disposal method for these altered rocks include the enhancement of As adsorption through the addition of natural or artificial adsorbents and the utilization of a covering soil with low permeability to minimize rainwater infiltration into the rock.

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Section: Introductionmentioning

confidence: 99%

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Tabelin

Igarashi

Takahashi

2012

Applied Geochemistry

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“…These results in conjunction with the low As content of calcite (Table 3) indicate that calcite found in the altered sedimentary rocks used in this study is not one of the primary sources of As. However, this might not be true for other hydrothermally altered rocks as noted by Horton et al (2001). These authors reported that although most of the calcite samples that they analyzed had low As contents, those located in fault zones in direct contact with the hydrothermal fluid were rich in As (mean As content = 81.2 ppm).…”

Section: Mechanisms Controlling the Mobilities Of Arsenic And Lead Unmentioning

confidence: 93%

“…Hydrothermally altered rocks have been extensively studied 3 especially in the context of ore formation, metal enrichment, and mineralization (Aiuppa et al, 2006;Allen and Hahn, 1994;Franzson et al, 2008;Halbach et al, 1993;Horton et al, 2001;Huston et al, 1995;Marques et al, 2010;Martin-Crespo et al, 2004;Ostwald and England, 1977;Pokrovski et al, 2007), but very few have investigated the potential leaching of toxic elements from these rocks when exposed to the environment.…”

Section: Introductionmentioning

confidence: 99%

The roles of pyrite and calcite in the mobilization of arsenic and lead from hydrothermally altered rocks excavated in Hokkaido, Japan

Tabelin¹,

Igarashi²,

Tamoto³

et al. 2012

Journal of Geochemical Exploration

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This paper describes the enrichment of hydrothermally altered volcanic and sedimentary rocks with arsenic (As) and lead (Pb), and the effects of pyrite and calcite on the mobilities and release mechanisms of these toxic elements under oxic and anoxic conditions. Enrichment of the altered rock with As and Pb predominantly occurred in precipitated pyrite grains and not on the alumino-silicate minerals making up the matrix of the rock. Arsenic was incorporated in pyrite grains formed during alteration in both volcanic and sedimentary rocks, but Pb was only found in the pyrite grains of the volcanic rock samples. When in contact with water, altered volcanic rocks had acidic pH while altered sedimentary rocks had alkaline pH. The mobilities of both As and Pb from the altered rocks were enhanced at acidic and alkaline pH and a minimum was observed in the circumneutral pH under both oxic and anoxic conditions. The absence of O 2 retarded the oxidation of pyrite most notably in the alkaline region but not in the acidic and circumneutral pH. The absence of CO 2 increased the pH of samples with significant calcite content but did not affect those containing substantial amounts of pyrite. Increasing the CO 2 also had insignificant effect on the concentrations of As and Pb in the leachate. The mechanisms controlling the mobilization of As and Pb from these rocks like dissolution of soluble secondary minerals, pyrite oxidation and adsorption were all related to pyrite while the pH of the rock when in contact with water was controlled by pyrite and calcite. Thus, excavated waste rocks that have been altered can be grouped based on the relative abundance of pyrite and calcite and their pH when in contact with water.

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“…In addition, hydrothermally altered rocks have been extensively covered in the literature particularly in the context of ore formation and characterization (Aiuppa 3 et al 2006;Allen and Hahn 1994;Halbach et al 1993;Horton et al 2001;Huston et al 1995;Ostwald and England 1977). However, very few have tackled the problem associated with toxic element release from excavated rocks.…”

Section: Introductionmentioning

confidence: 99%

Removal of Arsenic, Boron, and Selenium from Excavated Rocks by Consecutive Washing

Tabelin

Basri²,

Igarashi

et al. 2012

Water Air Soil Pollut

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This paper describes the leaching behavior and release mechanisms of arsenic (As), boron (B) and selenium (Se) from excavated rocks using sequential extraction for solid-phase fractionation, batch experiments with pH variation, and consecutive batch experiments with changes in the solid-liquid mixing ratios. Arsenic in the excavated rock was mostly found with the sulfides/organic matter fraction while majority of the leachable B and Se were associated with the exchangeable phases. The leaching of As was strongly pH dependent, Se was pH dependent only around the acidic region, and B was pH independent. Consecutive washing technique with deionized water effectively lowered the B and Se concentrations in the leachate below the drinking water standards of Japan, but was inefficient in the removal of As. Arsenic exhibited non-conservative leaching behavior and its movement was affected by processes like dissolution, precipitation and pyrite oxidation. In contrast, B and Se behaved more conservatively, resulting in their easy removal from the excavated rock by simple washing and dilution.

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Hydrothermal arsenic enrichment in an active mountain belt: Southern Alps, New Zealand

Cited by 24 publications

References 41 publications

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

The roles of pyrite and calcite in the mobilization of arsenic and lead from hydrothermally altered rocks excavated in Hokkaido, Japan

Removal of Arsenic, Boron, and Selenium from Excavated Rocks by Consecutive Washing

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