Mercury speciation in the Mt. Amiata mining district (Italy): Interplay between urban activities and mercury contamination

doi:10.1016/j.chemgeo.2014.04.023

Chemical Geology

Volume 380, 25 July 2014, Pages 110-118

https://doi.org/10.1016/j.chemgeo.2014.04.023 Get rights and content

Highlights

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The speciation of Hg in solids was determined in the Mt. Amiata district (Italy).
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Different geological materials were investigated by various analytical techniques.
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The speciation is dominated by insoluble Hg sulfides (cinnabar and metacinnabar).
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Sparingly soluble Hg compounds are present, increasing Hg mobility in this area.
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Anthropization of the Mt. Amiata area may highly affect Hg speciation.

Abstract

A fundamental step to evaluate the biogeochemical and eco-toxicological significance of Hg dispersion in the environment is to determine speciation of Hg in solid matrices. In this study, several analytical techniques such as scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), sequential chemical extractions (SCEs), and X-ray absorption spectroscopy (XANES) were used to identify Hg compounds and Hg speciation in samples collected from the Mt. Amiata Hg mining district, southern Tuscany, Italy. Different geological materials, such as mine waste calcine (retorted ore), soil, stream sediment, and stream water suspended particulate matter were analyzed. Results show that the samples were generally composed of highly insoluble Hg compounds such as sulphides (HgS, cinnabar and metacinnabar), and more soluble Hg halides such as those associated with the mosesite group. Other moderately soluble Hg compounds, HgCl₂, HgO and Hg⁰, were also identified in stream sediments draining the mining area. The presence of these minerals suggests active and continuous runoff of soluble Hg compounds from calcines, where such Hg compounds form during retorting, or later in secondary processes. Specifically, we suggest that, due to the proximity of Hg mines to the urban center of Abbadia San Salvatore, the influence of other anthropogenic activities was a key factor for Hg speciation, resulting in the formation of unusual Hg-minerals such as mosesite.

Introduction

Mercury (Hg) is a heavy metal of environmental concern with no known biological function in humans (Eisler, 1987). Conversion of inorganic Hg to methyl-Hg (CH₃Hg⁺) is a potential concern in many environments, because it is at least one order of magnitude more mobile than inorganic Hg, 50–100 times more toxic, and more readily bioaccumulated, especially in the aquatic food chain (Compeau and Bartha, 1984, Gabriel and Williamson, 2004).

Speciation of Hg is fundamental, because it controls Hg solubility, reactivity, bioavailability, and therefore, toxicity (Stein et al., 1996). The solubility of Hg compounds varies considerably, from Hg sulphides, which are less reactive compared to Hg-chlorides/sulphates/oxides, the latter displaying much higher solubilities (Kim et al., 2000). Mercury sulphides are the most abundant ore minerals in Hg deposits, but are the least toxic of the Hg compounds (Morita et al., 1998).

Erosion and runoff of Hg from inactive and active Hg mines worldwide potentially contaminates local streams and rivers (Gray et al., 2006, Rimondi et al., 2012).

The speciation of low Hg concentrations in complex mixed inorganic and organic matrices, such as soils and sediments, can be determined by means of different techniques: SCE, SEM-EDS and transmission electron microscopy (TEM), XAS, and thermal desorption (Biester et al., 2000, Kim et al., 2004, Neculita et al., 2005, Bernaus et al., 2006, Esbrí et al., 2010). The combined use of these microanalytical techniques provides a tool for the identification of minor, but important, soluble and insoluble Hg compounds in various solid samples collected from areas of past Hg mining. The high lower limit of determination for Hg (usually ~ 1–100 μg/g) during XAS analysis prevents the application of this technique to lower concentrations (ng/g) of Hg, which is common for methyl-Hg in contaminated areas (Gray et al., 2006, Gray et al., 2004, Rimondi et al., 2012). Conversely, low concentrations of Hg in solids can be quantified by SCE. Therefore, information from these two techniques is complementary (Kim et al., 2003, Terzano et al., 2010).

In this study, SEM-EDS, SCE, and XANES analyses were used in order to identify various Hg compounds and Hg speciation in samples collected from the Mt. Amiata Hg district (southern Tuscany, Italy; Fig. 1), the 4th largest Hg producing region worldwide. Here mining activity ceased in the 1980s, but abandoned mine wastes continue to release Hg into the downstream environment, where Hg is actively methylated and accumulated in fish (Rimondi et al., 2012). Moreover, runoff from Mt. Amiata is not limited to the local fluvial ecosystems but extends several kilometers downstream from the mines (Gray et al., 2014), and thus affects the Hg budget of the Mediterranean region. The Mediterranean basin, comprising, in addition to Mt. Amiata, the giant Hg districts at Almadén, Spain, and Idrija, Slovenia, accounts for about 60% of the Hg historically produced worldwide (Hylander and Meili, 2003).

Despite its importance, geochemical studies in the Mt. Amiata area are sparse, and investigations of Hg speciation combining XANES and SCE represent a completely new and novel approach, with few examples for other areas mined for Hg worldwide. Moreover, at the main Mt. Amiata Hg mine (Abbadia San Salvatore), waste calcines are located next to the urban center, offering then the possibility to study the interaction of Hg with urban activities. In this study, a comprehensive set of samples collected in and around the Mt. Amiata area were analyzed including (1) mine waste calcines and soils, (2) suspended particulate matter in stream waters, (3) stream sediments, and (4) pre-industrial (pre-dating mining) stream sediments. Speciation of Hg was identified in materials representing both the source of Hg to the environment (calcine and soil in the mining area), and downstream sites with Hg contamination (lake and stream sediment). Moreover, the present-day speciation of Hg in the mining area was evaluated by analysis of suspended particulate matter in stream water, whereas sediment deposited in pre-industrial times provided the local pre-mining background. A finding of particular interest is the occurrence of mosesite, a quite rare Hg halide that so far had been reported only as an alteration product of primary ores (Kim et al., 2000, Kim et al., 2004); we suggest that this phase results from the interplay between mine residues and other urban activities.

Section snippets

Investigated site

In southern Tuscany (Italy), a large Hg and Sb metallogenic province is centered around Mt. Amiata (Fig. 1), an active volcano-geothermal area, developed in the inner part of the Northern Apennines. The building of the Apennines during the Tertiary as a thrust and fold chain (see e.g. Molli, 2008, for a review) and the related post-collisional events determined the present geological setting of Mt. Amiata, and related volcanism and geothermal activity. The Hg–Sb metallogeny is associated with

Chemical analysis and XRD/microprobe studies

Concentrations of Hg in solid samples varied between 27 and 1480 μg/g (Table 2). The highest Hg concentrations were found in mine waste calcines (688–1480 μg/g). Previous studies have reported high Hg concentrations in calcine, which is related to the presence of HgS that was not converted to Hg gas during ore retorting, as well as Hg by-product compounds formed during retorting (Gray et al., 2004, Rimondi et al., 2012).

High Hg concentrations (108–671 μg/g) were found in samples of soil, stream

Conclusions

Speciation results obtained using XANES and SCE analysis generally show Hg sulphides as the dominant minerals in most of the analyzed soil and sediment samples. Anthropogenic processes such as ore roasting affect the speciation of Hg in mine waste calcines, mainly resulting in (a) minor amounts of Hg⁰, (b) conversion of cinnabar to metacinnabar, (c) secondary formation of moderately soluble Hg(I)-chlorides and Hg–N–Cl⁻ compounds, and (d) formation of moderately soluble Hg species such as HgCl₂

Acknowledgments

This study was financially supported by MIUR PRIN 2010–2011 (grant 2010MKHT9B to P. Costagliola and P. Lattanzi). We wish to acknowledge the staff of the European Synchrotron Radiation Facility for their assistance during XANES data collection at Beamline BM25. Daniele Rappuoli and Marcello Niccolini (Municipality of Abbadia San Salvatore) are gratefully thanked for their assistance during the fieldwork. This research was accomplished thanks to the scientific instruments provided by the Ente

References (59)

F. Bardelli et al.
Characterization of road dust collected in Traforo del San Bernardo highway tunnel: Fe and Mn speciation
Atmos. Environ.
(2011)
M.O. Barnett et al.
Oxidative dissolution of metacinnabar (β-HgS) by dissolved oxygen
Appl. Geochem.
(2001)
N.S. Bloom et al.
Selective extractions to assess the biogeochemically relevant fractionation of inorganic mercury in sediments and soils
Anal. Chim. Acta.
(2003)
D.T. Cuong et al.
Metal speciation in coastal marine sediments from Singapore using a modified BCR-sequential extraction procedure
Appl. Geochem.
(2006)
V. Davide et al.
Characterisation of bed sediments and suspension of the river Po (Italy) during normal and high flow conditions
Water Res.
(2003)
C. Gleyzes et al.
Fractionation studies of trace elements in contaminated soils and sediments: a review of sequential extraction procedures
Trends Anal. Chem.
(2002)
J.E. Gray et al.
Mercury methylation influenced by areas of past mercury mining in the Terlingua district, Southwest Texas USA
Appl. Geochem.
(2006)
E.A. Holley et al.
Mercury mobilization by oxidative dissolution of cinnabar (α-HgS) and metacinnabar (β-HgS)
Chem. Geol.
(2007)
L.D. Hylander et al.
500 years of mercury production: global annual inventory by region until 2000 and associated emissions
Sci. Total Environ.
(2003)
M.-P. Isaure et al.
Quantitative Zn speciation in a contaminated dredged sediment by μ-PIXE, μ-SXRF, EXAFS spectroscopy and principal component analysis
Geochim. Cosmochim. Acta
(2002)

C.S. Kim et al.

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy

Sci. Total Environ.

(2000)

C.S. Kim et al.

Geological and anthropogenic factors influencing mercury speciation in mine wastes: an EXAFS spectroscopy study

Appl. Geochem.

(2004)

M.D. Krohn et al.

Relations of ammonium minerals at several hydrothermal systems in the western U.S

J. Volcanol. Geotherm. Res.

(1993)

E.R. Malinowski

Theory of error for target factor analysis with applications to mass spectrometry and nuclear magnetic resonance spectrometry

Anal. Chim. Acta.

(1978)

E.R. Malinowski

Theory of error applied to factor loadings resulting from combination target factor analysis

Anal. Chim. Acta.

(1980)

F. Panfili et al.

The effect of phytostabilization on Zn speciation in a dredged contaminated sediment using scanning electron microscopy, X-ray fluorescence, EXAFS spectroscopy, and principal components analysis

Geochim. Cosmochim. Acta

(2005)

V. Rimondi et al.

Concentration, distribution, and translocation of mercury and methylmercury in mine-waste, sediment, soil, water, and fish collected near the Abbadia San Salvatore mercury mine, Mt. Amiata district, Italy

Sci. Total Environ.

(2012)

R. Terzano et al.

Solving mercury (Hg) speciation in soil samples by synchrotron X-ray microspectroscopic techniques

Environ. Pollut.

(2010)

J.R. Bacon et al.

Is there future for sequential chemical extractions?

Analyst

(2008)

A. Bernaus et al.

Characterisation of Almadén mercury mine environment by XAS technique

J. Environ. Monit.

(2005)

A. Bernaus et al.

Microprobe techniques for speciation analysis and geochemical characterization of mine environments: the mercury district of Almadén in Spain

Environ. Sci. Technol.

(2006)

H. Biester et al.

Mercury speciation in sediments affected by dumped mining residues in the drainage area of the Idrija mercury mine, Slovenia

Environ. Sci. Technol.

(2000)

J.E. Burkstaller et al.

Oxidation of cinnabar by Fe(III) in acid mine waters

Environ. Sci. Technol.

(1975)

G.C. Compeau et al.

Methylation and demethylation of mercury under controlled redox, pH and salinity conditions

Appl. Environ. Microbiol.

(1984)

P. Costagliola et al.

Arsenic bearing-calcite in natural travertines: evidence from sequential extraction, μ-XAS AND μ-XRF

Environ. Sci. Technol.

(2013)

F.W. Dickson et al.

The stability relations of cinnabar and metacinnabar

Am. Mineral.

(1959)

V. Duchi et al.

Geochemical study of gases and waters of the low temperature thermal systems of the Mt. Amiata area

Boll. Soc. Geol. Ital.

(1985)

R. Eisler

Mercury Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review. Biological Report 85 (1.10)

(1987)

J.M. Esbrí et al.

XANES speciation of mercury in three mining districts — Almadén, Asturias (Spain), Idria (Slovenia)

J. Synchrotron Radiat.

(2010)

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Mercury speciation in the Mt. Amiata mining district (Italy): Interplay between urban activities and mercury contamination

Highlights

Abstract

Introduction

Section snippets

Investigated site

Chemical analysis and XRD/microprobe studies

Conclusions

Acknowledgments

Atmos. Environ.

Appl. Geochem.

Anal. Chim. Acta.

Appl. Geochem.

Water Res.

Trends Anal. Chem.

Appl. Geochem.

Chem. Geol.

Sci. Total Environ.

Geochim. Cosmochim. Acta

Sci. Total Environ.

Appl. Geochem.

J. Volcanol. Geotherm. Res.

Anal. Chim. Acta.

Anal. Chim. Acta.

Geochim. Cosmochim. Acta

Sci. Total Environ.

Environ. Pollut.

Is there future for sequential chemical extractions?

Analyst

Characterisation of Almadén mercury mine environment by XAS technique

J. Environ. Monit.

Microprobe techniques for speciation analysis and geochemical characterization of mine environments: the mercury district of Almadén in Spain

Environ. Sci. Technol.

Mercury speciation in sediments affected by dumped mining residues in the drainage area of the Idrija mercury mine, Slovenia

Environ. Sci. Technol.

Oxidation of cinnabar by Fe(III) in acid mine waters

Environ. Sci. Technol.

Methylation and demethylation of mercury under controlled redox, pH and salinity conditions

Appl. Environ. Microbiol.

Arsenic bearing-calcite in natural travertines: evidence from sequential extraction, μ-XAS AND μ-XRF

Environ. Sci. Technol.

The stability relations of cinnabar and metacinnabar

Am. Mineral.

Geochemical study of gases and waters of the low temperature thermal systems of the Mt. Amiata area

Boll. Soc. Geol. Ital.

Mercury Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review. Biological Report 85 (1.10)

XANES speciation of mercury in three mining districts — Almadén, Asturias (Spain), Idria (Slovenia)

J. Synchrotron Radiat.