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The role of secondary minerals in controlling the
migration of arsenic and metals from high-sulfide
wastes (Berikul gold mine, Siberia)
R. Giere ´ a,*, N.V. Sidenkob, E.V. Lazarevab
aDepartment of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907-1397, USAbThe United Institute of Geology, Geophysics and Mineralogy, pr. Koptyuga 3, Novosibirsk 630090, Russia
Abstract
The role of secondary minerals in controlling the migration of As, Cu, Zn, Pb and Cd has been investigated in piles
of high-sulfide waste at the Berikul Au mine, Kemerovo region, Russia. These wastes contain 40–45 wt.% sulfides and
have been stored for approximately 50 a near the Mokry Berikul river. Sulfide oxidation generates acid pore solutions
(pH=1.7) with high concentrations of SO42 (190 g/l), Fe (57 g/l), As (22 g/l), Zn (2 g/l), Cu (0.4 g/l), Pb (0.04 g/l), and
Cd (0.03 g/l). From these solutions, As is precipitated as amorphous non-stoichiometric Fe-sulfoarsenates in the lower
horizons of the waste piles. During precipitation of the Fe-sulfoarsenates, the concentration of Fe in these phases
decreases from 34 to 21 wt.%, that of As increases from 11 to 22 wt.%, while the S content remains approximately
constant (5.4–5.8 wt.%). Arsenic is also accumulated in jarosite-beudantite solid solutions (up to 8.4 wt.% As), which
occur as inclusions in the amorphous Fe-sulfoarsenates. In efflorescent crusts on the surface of the waste pile, As co-
precipitates with the Fe(III) sulfates copiapite (0.27 wt.% As) and rhomboclase (0.87 wt.% As). Zinc and Cu are
incorporated primarily into Fe(II) sulfates, i.e. melanterite in the interior of the waste pile, and rozenite in the efflor-
escent crust. The Zn mineral dietrichite is also formed at the surface of the waste pile as a result of evaporation of pore
solutions, and is the only Fe(II) sulfate containing detectable amounts of As (0.64 wt.%). Lead is mainly co-pre-
cipitated with minerals of the jarosite group, where the Pb content may reach 4.3 wt.%. Co-precipitation of toxic ele-
ments with sulfates and sulfoarsenates of Fe is shown to be a significant mechanism in controlling the concentration of
heavy metals in pore solutions of high-sulfide mine wastes. Precipitation of secondary phases causes the formation of a
hardpan layer with low permeability at a depth of 1–1.5 m below the surface of the waste pile. Rainwater accumulates
above the hardpan horizons and slowly drains along these aquicludes to the bottom of the pile. Most of the rainwater
evaporates during infiltration. This leads to formation of the described efflorescent sulfate crusts. Dissolution of these
crusts during the next rain storm produces highly acidic surface waters (pH=1.1) rich in SO42 (30 g/l), Fe (18 g/l), As
(0.24 g/l), Zn (0.12 g/l), Cu (0.04 g/l), Pb and Cd (0.002 g/l). During the warm (t>0 C) period of the year, which lasts
about 7 months, these surface waters transport a total of a few tens of kilograms of As and Zn, several kilograms of Cu, and a few hundred grams of Pb and Cd from the waste pile into the Mokry Berikul river. As a result, the con-
centrations of these metals in the river water increase by an order of magnitude, thus reaching levels close to, or
exceeding the maximum values permissible for drinking water.
# 2003 Elsevier Science Ltd. All rights reserved.
0883-2927/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0883-2927(03)00055-6
Applied Geochemistry 18 (2003) 1347–1359
www.elsevier.com/locate/apgeochem
* Corresponding author.
E-mail address: [email protected] (R. Giere ´ ).
mailto:[email protected]:[email protected]://www.sciencedirect.com/http://www.sciencedirect.com/http://www.sciencedirect.com/
8/17/2019 The Role of Secondary Minerals in Controlling
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1. Introduction
Abandoned mine wastes containing high sulfide con-
centrations are among the most serious sources of
environmental pollution. Understanding the geochem-
ical processes which control precipitation and dissolu-
tion of secondary minerals in abandoned sulfide mines iscrucial for the formulation of models that predict the
environmental impact of such sites. Moreover, a better
knowledge of these mechanisms will allow remediation
of existing problem sites and/or a reduction of the
extent of future pollution. Pore waters in and drainage
solutions from high-sulfide waste are characterized by
low pH values and high concentrations of various heavy
metals (Blowes et al., 1991; Nordstrom, 1991). The
concentration of heavy metals in the pore solutions is
mainly controlled by their precipitation together with Fe
hydroxides and/or sulfates (Blowes and Jambor, 1990).
Precipitation and dissolution cycles of some secondaryminerals are strongly influenced by seasonal wetting and
drying cycles (Frau, 2000), and thus it is important to
include meteorological parameters in models that simu-
late environmental impacts. Although mobilization of
As from mine waste is discussed in the literature, most
reports focus on low-sulfide wastes only (e.g., Al et al.,
1994; Leblanc et al., 1996; Roussel et al., 1998; Lang-
muir et al., 1999; Shuvaeva et al., 2000; Ardau et al.,
2001; Gaskova and Bortnikova, 2001).
The goal of the present study is to understand the
processes controlling the migration and sequestration of
Cu, Zn, and Pb and, in particular, the mobility of As in
high-sulfide waste piles. To achieve this goal, the authors
investigated high-sulfide mine wastes at the Berikul Au
mine in Siberia. A specific objective of the present paper
is to combine detailed mineralogical investigations of
the secondary phases occurring in the waste with both
meteorological observations and studies of the water
chemistry of samples collected in various parts of the
waste pile and in the nearby river.
2. Description of the waste site
The Berikul Au mine is situated in the northern partof the Kemerovo region, Western Siberia, about 450 km
NE of Novosibirsk (Fig. 1). The deposit, an Au-sulfide-
quartz vein with a Au content of 1–5 g/t, was mined
exclusively for Au. The mine was in operation between
1942 and 1991, but no other production data were
available to the authors. Gold occurred as fine-grained
intergrowths with sulfide minerals, mainly pyrite and
arsenopyrite. From these sulfides, Au was extracted at
the Berikul mill by using the cyanide technique. After
removal of the Au-bearing cyanide solutions, the sulfide
flotation residues were neutralized by adding Ca(ClO)2
before being dumped on waste piles. The waste studiedhere has been in a pile since 1952, while waste from
other piles was used for road construction when new
tailings impoundments were built in 1972.
The discarded material contains 40–45 wt.% fine-
grained sulfides, including pyrite (35–40 wt.%), arseno-
pyrite (2–5 wt.%), and minor amounts of pyrrhotite,
sphalerite, chalcopyrite, and galena. Among the gangue
minerals found in the wastes, the predominant phases
are quartz (30–35 wt.%), albite (5–10 wt.%), chlorite
(5–10 wt.%), muscovite (about 5 wt.%), and calcite (3–5
wt.%). The studied high-sulfide wastes have been
deposited on alluvial material, consisting of carbonate
boulders, and were stored for about 50 a on the left
bank of the Mokry Berikul river. The waste pile has a
length of approximately 250 m, a width of 50 m at its
base, and a height of 3 m (Fig. 2). The alluvial material
around the waste pile is dry, and no springs have been
detected near the river bank, suggesting that the river
Fig. 1. Map showing the location of the Berikul Au mine in the Kemerovo region of Southwestern Siberia.
1348 R. Gieré et al. / Applied Geochemistry 18 (2003) 1347–1359
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represents the local ground water table. The only
‘‘springs’’ found are drainage water emanations at the
base of the waste piles (Plate IA, Fig. 2).
The Berikul site is located at an altitude of 850 m
above sea level. The average yearly temperature is
1.5 C, and the total precipitation averages 600 mm of
rain and snow annually. There is, however, a distinct
warm period during which the temperature is above
freezing. This warm period lasts from May to October,
and most of the precipitation (approximately 400 mm)falls during this time.
3. Methods of investigation
Solid samples were collected from both surface out-
crops and excavation pits, which were dug with a
mechanical excavator in different parts of the waste pile
(see Fig. 2). The pits were excavated in order to gain an
insight into the stratification of the waste pile, to com-
pare vertical and lateral zoning, and to collect samples
from the interior of the pile. The solids were then put
into hermetically sealed polyethylene bags and frozen
immediately to preserve the initial characteristics of
pore waters. The solid waste material was studied by
reflected light microscopy and scanning electron micro-
scopy (Jeol JSM-36). X-ray powder diffraction (XRD)
analyses were performed with a DRON-UM dif-
fractometer (Burevestnik, made in Russia) using filtered
Cu-K a radiation. Thermogravimetric analysis (TGA)
was carried out with a MOM device (made in Hungary),
using a 120 mg sample, which was heated from roomtemperature to 1000 C, at 12 C/min.
The compositions of the secondary phases were
determined with a CAMECA-SX50 electron microp-
robe at the Department of Earth and Atmospheric Sci-
ences of Purdue University. The instrument is equipped
with 4 wavelength dispersive spectrometers, and was
operated for quantitative analysis at an acceleration
potential of 20 kV and a beam current of 80 nA mea-
sured on a Faraday cup. Samples and standards were
coated with 20 nm of C. Well-characterized minerals
and synthetic oxides were used as standards. Data col-
lection time was 20 s for most major elements, and
Fig. 2. Schematic map of the studied waste pile and the surrounding area at the Berikul site showing sample localities, hydrologicalstations, and excavation pits.
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thawed in the laboratory. With the exception of the pore
solutions, the Eh and the pH of all water samples were
measured in the field immediately after sampling by
using an INFRASPAK potentiometer (made in Russia),
whereby the precision of a single measurement was 10
mV for Eh, and 0.08 for pH. The Eh and pH mea-
surements for the pore solutions were carried out onlyafter the samples had been thawed and the solutions
extracted in the laboratory. Approximately 100 ml of
solution were collected by a syringe through a filter
(0.45 mm) into glassware, and were subsequently divided
into two aliquots. One of the aliquots was then acidified
with HNO3 to preserve the metal concentration,
whereas the other aliquot was preserved in its initial
state. All water samples were stored about 1 month at a
temperature 4–6 C in a refrigerator. The concentrations
in the acidified solutions of As, Ca, Cd, Cu, Fe, K, Mg,
Na, Pb, and Zn were determined by flame atomic-
absorption spectrometry (AAS; Perkin-Elmer equip-ment, model 3030E equipped with an HGA-600
graphite furnace) and by thermal-electric AAS (Pue-
Unikam equipment, model SP-9). The contents of
NH4+, Cl, F, NO3
, HCO3, and SO4
2 were deter-
mined in the second aliquot by ion chromatography
using a Russian-made MILIXROM chromatograph.
4. Results and discussion
4.1. The waste pile in cross-section
During the fifty 50 a of storage in the pile, the waste
was subjected to supergene alteration, which led to a
characteristic layering. In cross-section, 5 main hor-izons can be distinguished in the waste pile (Fig. 3).
These are distinct in terms of mineral content, color,
porosity and hardness, and comprise, from bottom to
top:
4.1.1. Horizon 1
This zone consists of friable, only slightly altered sul-
fide wastes of gray-green color. It contains 3–5 wt.%
calcite, and is approximately 1–1.5 m thick.
4.1.2. Horizon 2
Overlying horizon 1, this layer consists of lithifiedwaste containing gypsum as binding material. It is a
hardpan layer with a thickness of approximately 1 m.
Leaching cavities are observed in this zone (shown in
black in Fig. 3), and these are often filled by jarosite and
amorphous Fe-sulfoarsenates (Plate IB). As a rule, such
hardpan layers are characterized by low permeability,
which prevents penetration of solutions and gases into
the deeper horizons of waste piles (Blowes et al., 1991).
At the studied site, the hardpan layer contains trace
amounts of calcite, i.e. approximately 1 wt.%, but all
overlying horizons are devoid of calcite.
4.1.3. Horizon 3
Overlying the hardpan layer is a tobacco-colored,
0.5–1 m thick horizon, which consists of very moist and
fine-grained wastes of silt size. This zone, referred to as
the melanterite zone, contains leached relics of hardpan
material (Fig. 3), which are overgrown by melanterite
aggregates (up to 10 cm across). The presence of such
relics of lithified material in horizons above the actual
hardpan layer documents that the lithified waste is dis-
solving as a result of decreasing pH in the pore solutions
during sulfide weathering. The hardpan material,
however, decomposes only slowly, because of its low
permeability.
4.1.4. Horizon 4
This thin intermediate zone has a gray color, and is
composed of quartz, jarosite and sulfides. It separates
the melanterite zone from the overlying horizon 5.
4.1.5. Horizon 5
The uppermost horizon is distinctly yellow, is up to
0.5 m thick, and contains some strongly oxidized relics
of hardpan material. The predominant phase is jarosite;
hence, this horizon is referred to below as the jarosite
zone.
Fig. 3. Supergene weathering profile through the waste pile at
the Berikul site. This profile displays the situation encountered
in excavation pit B-2/99 in the eastern part of the waste pile (see
Fig. 2), but it is representative of the entire site. The numbered
horizons are described in the text.
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4.2. Secondary minerals
4.2.1. Gypsum (CaSO42H 2O)
Gypsum is the earliest secondary mineral found, and
it occurs even in the slightly altered sulfide wastes of
zone 1. In the hardpan layer, gypsum crystals are up to
2 mm across and form a framework that binds the fine-grained sulfide phases (Plate IB). The concentrations of
As, Cu, Zn, and Pb in gypsum are all below detection
limits.
4.2.2. Jarosite solid solutions
Two main varieties of jarosite-group phases were
detected, and these can be distinguished on the basis of
the predominance of alkali-site ions (Table 1). The first
variety is hydronium jarosite (H3O,K,Na)Fe3+3 (-
SO4)2(OH)6. The second variety is jarosite sensu stricto,
(K,H3O,Na)Fe3+3 (SO4)2(OH)6, with K concentrations
that are considerably higher (3.1 wt.%) than in hydro-nium jarosite. Average Na concentrations are low in
both varieties, namely 0.3 and 0.5 wt.% in hydronium
jarosite and jarosite, respectively. Hydronium jarosite
forms spherical aggregates up to 20 mm in size, which
were observed in all horizons (Plate IC). Extensive pre-
cipitation of hydronium jarosite must have started after
formation of gypsum in the hardpan layers, as docu-
mented by the mineralogical zoning observed around
leaching cavities in the hardpan (typical zoning shown
in Plate IB).
The zones more distant from the open cavity are less
altered and contain the earliest secondary phase, i.e.
gypsum (Zone 1 in Plate IB). In the more weathered
material, which forms the walls of cavities (Zone 2 in
Plate IB), hydronium jarosite begins to appear. Sul-
foarsenates are observed closest to and as incrustations
of the cavities (Zone 3 in Plate IB). From these obser-
vations, it is concluded that during the weathering of the
waste material, the secondary minerals crystallized in
the following sequence: gypsum ! hydronium jarosite
! sulfoarsenates.
The second jarosite variety, jarosite sensu stricto,
occurs as oolites of about 5 mm in diameter along cracks
(Plate IC) in horizon 4 (see Fig. 3). It also forms rims
around hydronium jarosite, showing clearly that it pre-
cipitated after hydronium jarosite. Jarosite is con-
siderably richer in Cu and Zn than hydronium jarosite
(Table 1). Moreover, jarosite is characterized by sig-nificantly higher contents of both As (1.7 wt.%) and Pb
(4.3 wt.%). Joint incorporation of As and Pb into jar-
osite is consistent with the possible occurrence of a solid
solution between jarosite [KFe33+(SO4)2(OH)6] and
beudantite [PbFe33+(AsO4,SO4)(OH)6; see also Jambor
and Dutrizac, 1983; Rattray et al., 1996].
4.2.3. Amorphous iron sulfoarsenates (AISA)
Sulfoarsenates of Fe are precipitated in the leaching
cavities observed in the hardpan layer (Plate IB), as well
as in the lithified hardpan relics in the waste of the
overlying horizons 3 and 5 (Fig. 3). These phases are X-ray amorphous, and exhibit a reddish-brown to reddish-
orange color. As outlined below, there are 3 varieties of
AISA, which can be distinguished on the basis of their
chemical composition. Since the authors were unable to
select enough material of a specific type of AISA based
on its physical appearance, a sample of non-distinct
AISA had to be used for infrared (IR) spectroscopy,
TGA and XRD. The IR spectrum of this material is
similar to that of sarmientite, Fe3+2 (AsO4)(-
SO4)OH5H2O, and thus qualitatively points to a simi-
lar composition (Fig. 4a). The thermal properties of
these two phases are also similar, as documented by the
weight loss curves shown in Fig. 4b. The weight loss
between 100 and 685 C, representing water content, is
30.2% for the amorphous phase, and 23.0% for sar-
mientite. The weight losses between 685 and 980 C,
representing the SO3 content, are 4.8 and 16.4% for the
amorphous phase and sarmientite, respectively. To
explore which phases would crystallize from the amor-
phous substance if it were heated, the AISA sample was
heated to 220 C and kept at that temperature for 6 h.
Table 1
Average elemental concentrations (with standard deviations) in sulfoarsenates and sulfates of Fe (wt.%), as determined by electronprobe microanalysis
n Al As Cu Fe K Pb S Zn
Hydronium jarosite from horizon 4 7 0.110.07 0.730.10 0.010.01 28.81.3 0.970.26 0.310.08 11.80.3 0.010.02
Hydronium jarosite from horizon 5 24 0.120.08 0.350.13 0.030.02 27.22.3 1.60.3 0.360.24 10.80.7 0.020.02
Jarosite from horizon 4 7 0.060.02 1.70.2 0.240.08 29.90.6 3.10.4 4.30.8 12.50.3 0.170.09
AISA, matrix of group I 12 0.300.11 11.01.0 0.040.03 34.31.4 0.070.08 0.070.03 5.40.7 0.080.05
AISA, matrix of group II 33 1.20.3 14.01.3 0.030.03 28.81.0 0.020.03 0.090.05 5.90.4 0.260.10
AISA, group III 82 1.90.4 21.61.4 0.090.04 20.91.7 0.030.10 0.890.35 5.51.0 0.290.07
Inclusions in matrix of group I 6 0.200.10 8.12.3 0.040.03 32.01.1 1.00.5 0.340.26 7.81.4 0.060.04
Inclusions in matrix of group II 16 2.90.9 8.42.5 0.030.03 25.22.6 1.81.5 1.71.1 8.01.2 0.240.10
n=Number of analyses; AISA is amorphous Fe-sulfoarsenates.
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Following heat treatment, an XRD pattern was gener-
ated, revealing peaks that correspond to the d-spacings
of the strongest lines of jarosite, beudantite, and goe-
thite (Fig. 4c). The crystalline equivalent of the studied
AISA sample, thus, is a phase mixture, which displays
an overall similarity in IR and thermal properties to the
Fe-sulfoarsenate sarmientite. This crystalline phase
mixture, however, does not correspond exactly to the
amorphous starting material, because the heat treatment
must also have changed the water content (see Fig. 4b).
Among the amorphous Fe-sulfoarsenates, up to 3
types may be distinguished by chemical composition
and microstructure. The two earliest varieties, adjoining
the walls of the cavities, are reddish-brown in color and
consist of a matrix containing microscopic spherical
inclusions (Plate ID), which will be discussed below.
Farthest away from the cavity walls, a third zone occurs
which is reddish-orange in color, and does not contain
any inclusions. The As content in the matrix increases
from the earliest variety (AISA, group I, Table 1) to the
Fig. 4. Properties of an amorphous Fe-sulfoarsenate sample. (a) Infrared (IR) absorption spectra showing the absorption bands cor-
responding to molecules of water, sulfate and arsenate. Solid line=spectrum for amorphous Fe-sulfoarsenate (this study); dotted
line=spectrum for sarmientite (from Abeledo and Benyacar, 1968.); (b) thermogravimetric data for amorphous Fe sulfoarsenate
(solid line) and sarmientite (dotted line); (c) powder XRD pattern obtained after heating the amorphous Fe-sulfoarsenate material.The pattern reveals a mixture of beudantite (Bd), jarosite (Jr) and goethite (Gt).
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latest one (group III) from 11 to 22 wt.%, while the Fe
content decreases in the same order, from 34 to 21
wt.%. The heavy metal contents increase to a lesser
extent, namely Zn from 0.08 to 0.29 wt.%, Cu from 0.04
to 0.09 wt.%, and Pb from 0.07 to 0.9 wt.%. This che-
mical evolution from group I to group III takes place at
nearly constant S contents (Table 1). In the ternary dia-
gram shown in Fig. 5, the matrix of group II plots close
to the ideal composition of beudantite (PbFe3+3 (AsO4,-
SO4)(OH)6), i.e., it is significantly richer in Fe than
stoichiometric bukovskyite (Fe3+2 (AsO4)(-
SO4)OH7H2O) and sarmientite. Bukovskyite and beu-
dantite have been identified at the Carnoules Pb-(Zn)
mine, Gard, France where they are associated withscorodite (Fe3+AsO42H2O) and angelellite
(Fe3+4 As2O11), which were precipitated from acidic mine
waters (Leblanc et al., 1996). Group-III AISA plot near
the ideal composition of zykaite (Fe3+4 (AsO4)3(-
SO4)OH15H2O) in Fig. 5, but they are richer in SO3.
As displayed in Fig. 5, the studied amorphous sulfoar-
senates exhibit a wide compositional variation, and their
average compositions do not correspond to the stochio-
metry of the discussed minerals. The inclusions in group
I and II contain more Al, K, Pb and less As in compar-
ison to the matrix (Plate ID, Table 1). On the ternary
As2
O5 –SO
3 –Fe
2O3
diagram, the compositions of these
inclusions form distinct trends between jarosite and
beudantite, suggesting that they represent solid solu-
tions between these two phases.
In summary, the chemical analyses and the X-ray
powder pattern of the heated amorphous substance
indicate that the inclusions may represent poorly crys-
tallized jarosite (KFe33+(SO4)2(OH)6)–beudantite
(PbFe33+(AsO4,SO4)(OH)6) solid solutions. The average
contents of SO3 and As2O5 in jarosite–beudantite are
similar in both group I and group II inclusions, but the
group I inclusions are richer in Fe (Table 1, Fig. 5).
Additionally, the second group is characterized by
higher concentrations of Al and Zn. The latter is sub-
stituting for Fe in the jarosite structure. The overallsequential increase in Al, As, Zn and Pb observed for
both the matrix and the jarosite - beudantite inclusions
from earliest to latest varieties suggests that the con-
centrations of these elements in the pore solution
increased during formation of these phases. Such an
increase in concentration in solutions with simultaneous
deposition of solids is possible only if water evaporates.
4.2.4. Melanterite (Fe2+SO47H 2O)
Melanterite occurs as green crystals (up to 2 cm
across) in the interior parts of the waste pile. This is in
contrast to other soluble Fe-sulfates, which have been
Fig. 5. Ternary diagram (in mol%) for the system As2O5 –SO3 –Fe2O3 –H2O, showing the ideal composition (star symbols) of selected
minerals in the system, and the analyzed compositions of jarosites and amorphous Fe-sulfoarsenates (AISA) from the Berikul site.
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found only on the surface of the waste pile. Melanterite
is observed to overgrow hardpan relics, which contain
jarosite solid solutions and amorphous Fe-sulfoarse-
nates, and therefore is clearly younger than both the
jarosite solid solutions and the amorphous Fe-sulfoar-
senates. In the uppermost portions of the waste pile,
however, melanterite gives way to jarosite (horizons 4and 5, Fig. 3), probably as a result of the more oxidiz-
ing conditions near the surface of the waste pile. Thus,
sulfates and sulfoarsenates of Fe3+ are precipitated
during the earliest and last stages of weathering,
whereas sulfates of Fe2+ (i.e. melanterite) are formed
during the intermediate stage. This unusual develop-
ment of the weathering process, is at present not
understood.
Melanterite contains considerable amounts of Zn and
Cu (Table 2). Pisanites, i.e. Cu–Zn varieties of mel-
anterite, are common in wastes of sulfide ore deposits in
the Ural region (Emlin, 1991), and Zn-bearing mel-
anterite has been reported from Iron Mountain, Cali-
fornia, USA (Alpers et al., 1994). Recently, melanterite
has also been described as an environmentally impor-
tant secondary phase formed as a result of pyrite oxi-
dation at an abandoned mine in Sardinia, Italy (Frau,
2000).
4.2.5. Iron sulfates in efflorescent crust
On the slopes of the waste pile, efflorescent crusts
consisting of Fe-sulfates were observed. In these crusts,
formed through evaporation of pore solutions, the fol-
lowing Fe-sulfates were identified: rozenite (Fe2+
SO44H2O), copiapite (Fe2+Fe43+
(SO4)6(OH)220H2O),and rhomboclase (HFe3+(SO4)24H2O). The efflor-
escent crusts further contain the Zn mineral dietrichite,
(Zn,Fe2+)Al2(SO4)422H2O, which was also identified
by powder XRD and which contains equal amounts of
Zn and Fe (3.3 wt.%). The Fe2+/Fe3+ ratio decreases
from rozenite to copiapite, to rhomboclase (see the for-
mulae above), in parallel to the decrease in the contents
of Zn and Cu (Table 2). At the Berikul site, thus, Fe2+-
sulfates seem to be richer in Cu and Zn than Fe3+-sul-
fates. On the other hand, the highest As content is
observed in rhomboclase, suggesting that As is captured
when Fe(III) sulfates precipitate.
4.3. Water characteristics
During this study, 4 types of water were distinguished on
the basis of their occurrence: pore waters, drainage (infil-
trating) waters, surface waters, and water of the Mokry
Berikul river. Each type of water is a link in the pathway of
element migration into the environment (Fig. 6).The pore solutions are generated through interaction
of sulfides, rainwater and atmospheric O2. They are
accumulated above the low-permeable hardpan layer,
mainly in the melanterite zone (horizon 3, Fig. 3). It is
assumed that only a small part of the solutions could
penetrate through the hardpan layer, because the
slightly altered wastes in horizon 1 remained dry even
Table 2
Average elemental concentrations (with standard deviations) of As, Zn, Cu and Pb in the soluble sulfate phases (wt.%)
n As Zn Cu Pb
Melanterite, Fe2+SO47H2O 3
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that dissolution of surface minerals was much more
pronounced during the first rain storm, probably
because the intermittent dry period between the storms
was too short to build up a significant amount of sec-
ondary surface minerals in the efflorescent crusts. Tak-
ing the average metal concentrations in the surfacewaters (listed in Table 3) and the average discharge
volume for these two events (480 l), it was calculated
that each storm removed, on average, approximately
113 g As, 57 g Zn, 19 g Cu, 0.8 g Pb, and 0.8 g Cd from
the slope of the waste pile facing the Mokry Berikul
river, and discharged the metals into the river.
According to these measurements, and based on aver-
age meteorological data (400 mm of rain during the
warm season), it has been calculated that during the
warm season, a few tens of kilograms of As and Zn, sev-
eral kilograms of Cu, and a few hundred grams of Pb and
Cd might be transported into the Mokry Berikul river.
Some of the dissolved metals will be transformed into
suspended solid precipitates as soon as the acid surface
streams mix with the nearly neutral river water. The
above calculation assumes that the rainstorms whichwere sampled are typical of other rainstorms during the
warm season, and thus the authors are unable to antici-
pate the effects of much heavier or much lighter rains.
The river water exhibits a pH that ranges from 7.6
(upstream, sample B-4) to 6.5 (downstream, sample
B-11), reflecting the input of acid water from the waste
pile (Table 5). The river water samples have an average
Eh of +370 mV, and their total salt content is approxi-
mately 120 mg/l (Table 5). This water is a SO42-enriched
(12.5 mg/l on average) HCO32 –Ca type, with average
Table 4
Results of individual meteorological, chemical and hydrological measurements during two consecutive rainstorms in August 2000:
precipitation, elemental concentrations in surface waters (in mg/l), and volume of surface water (in l) discharged into the river for each
measuring station (see Fig. 2)
Precipitation Sampling station Zn Cd Pb Cu As Volume
1.93 mm (20.08.2000) ST-1/1 200 2.6 1.9 52 300 446ST-1/2 160 2.6 1.6 47 280 500
1.96 mm (22.08.2000) ST-2/1 55 0.7 1.7 26 170 423
ST-2/2 60 0.8 1.7 30 190 551
The data shown in Table 3 for the surface waters represent the average of all 4 measurements listed here.
Table 5
Water analyses of samples collected from the Mokry Berikul River (see Fig. 2). B-4: upstream; B-10: near waste pile; B-11: down-
stream
Sample # B-4 B-10 B-11 MCL (US) MCL (Russia)
pH 7.6 7.1 6.5 – –
Eh (mV) 389 359 346 – –
As
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contents of 18 mg/l Ca and 82.5 mg/l HCO32. Compared
to the upstream river water (sample B-4), the concentra-
tions of As, Cu, Zn, Pb and Cd are significantly higher in
the water near the waste pile (sample B-10), and gen-
erally even higher further downstream (sample B-11).
For example, the downstream concentration of Cd is
higher by two orders of magnitude than the upstreamconcentration. The concentration of As in the river near
the waste pile (sample B-10) is much higher than that in
the upstream water, and specifically, it is one order of
magnitude higher than the maximum contaminant level
allowed in drinking water in the US (EPA, 2001). A
similar observation can be made for the downstream
concentration of Cd. For Zn, the concentrations are
close to the maximum concentrations permitted in
drinking water in Russia (Eremeev, 1990).
The data clearly document that the waters emanating
from and running off the waste pile have a serious impact
on the water quality of the Mokry Berikul river. Thisenvironmental impact is particularly dramatic during the
warm season, when most of the precipitation is recorded
and evaporation is most intense. During the major part
of the cold season, the waste pile is covered by snow, which
reduces the evaporation as well as the amount of runoff.
5. Conclusions
Acid solutions containing high concentrations of
SO42, Fe, As and heavy metals are generated during
sulfide oxidation in the Berikul waste pile. The mobility
of As, Cu, Zn and Pb within the waste pile is controlled
by precipitation of these metals as secondary phases.
Arsenic is precipitated in the form of amorphous Fe-
sulfoarsenates, which form a matrix with inclusions of
jarosite–beudantite. These inclusions show lower con-
centrations of As than the matrix. On the surface of the
waste pile, As co-precipitates with sulfates containing
trivalent Fe. Copper and Zn are precipitated together
with melanterite and rozenite, because these metals sub-
stitute for Fe2+ in sulfates. Within the efflorescent crusts,
Zn is accumulated in dietrichite. Most of the Pb is cap-
tured by jarosite–beudantite solid solutions. A sequential
increase in Al, As, Zn and Pb in both amorphous sulfoar-senates and jarosite–beudantite inclusions suggests that
the concentrations of these elements increase in the pore
solution when the solid phases precipitate, a feature that
can be explained by slow water evaporation.
This study has established that the main pathway of
element migration is via surface drainage during and
after rainstorms. In dissolved form, a few tens of kilo-
grams of As and Zn, several kilograms of Cu, and sub-
kilogram quantities of Pb and Cd are removed by sur-
face waters and transported into the Mokry Berikul
river during the warm season of the year. This discharge
results in a dramatic increase in the As, Cu, Zn, Pb and
Cd concentration in the river water, where some of these
metals reach concentrations near or in excess of the
maximum levels permitted for safe drinking water.
Acknowledgements
The authors are grateful to Dr. Richard Wanty, Dr.
Pierfranco Lattanzi, and an anonymous reviewer for
providing constructive reviews. Their valuable sugges-
tions and thoughtful criticism of an earlier version
helped us to improve the quality of this paper. We fur-
ther would like to thank Carl Hager for his assistance at
the Purdue University electron microprobe.
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