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Dissolved matter and suspended solids in the Smolník Creek

polluted by acid mine drainage (Slovakia)


Department of Mineral Deposits Geology, Comenius University, Faculty of Natural Sciences, Mlynská Dolina G, 842 15 Bratislava,

Slovak Republic;,  Phone: (421) 260.296.495,  Fax: (421) 265.429.064

(Manuscript received February 21, 2005; accepted in revised form December 8, 2005)

Abstract: The impact of acid mine drainage on the Smolník Creek catchment was evaluated approximately 10 years after
the closure of the mining area. Water and suspended solids (particles  > 0.45  m) were collected five times from June
2002 to July 2003. The water chemistry of 44 samples and Fe, Al, Mg, Ca, Na, K, Cu, Zn, Mn, Pb, As contents of
25 suspended solids sample HNO

leachates were analysed. Past reclamation effort decreased the volume of water

effluent from the abandoned mine system and improved their quality, which is indicated by the decreased content of
dissolved matter from 7—17 g/l to 5 ± 1 g/l. However, from the new mine drainage 860 m


/day of acid mine drainage

water (pH 3.8 ± 0.5) enter the creek and other polluted water is generated by tailings and old dumps. Elevated contents
of Fe, SO



, Cu, Zn, Mn in comparison with the water limit (CD 98/83/EC) were detected in the creek water 16 km

downstream the mine, near the confluence with the Hnilec River. The total mass of suspended solids seasonally increased
2—3 times under the mine because of iron oxyhydroxides generation in the mine-creek water-mixing zones. The
suspended solids transported substantial doses of iron, Al, Cu, As and other elements, which can be the same or even higher
than is removed in dissolved form. The suspended solids analyses documented the immediate impact and quantity of mine-
derived pollution enlargement in the catchment and they increased objectivity of environmental impact assessment.

Key words: pollution, catchment, precipitates, acid mine drainage, iron oxyhydroxides.


Abandoned sulphide ore mines are serious source of acid
mine waters enriched with sulphate, iron and other toxic
elements, which contaminate surface water, sediments and
soils. The generation of this water is obviously the result
of pyrite oxidation in mine waste, which is subject to in-
tensive weathering (Nordstrom 1982; Gould et al. 1994;
Bigham et al. 1996). The generated acid mine drainage
(AMD) continually leaches the ore-bearing and rock min-
erals and mobilizes a number of potentially toxic ele-
ments. Pyrite as a waste mineral is deposited in gangue
dumps and tailing heaps where AMD would be produced
for tens of years (Jambor & Blowes 1994; Alpers & Blowes

The abandoned Smolník mine is regarded as a “hot spot”

in the Central Europe region, where AMD is generated and
discharged from a flooded mine and contaminated the
Smolník Creek catchment (Lintnerová 1996; Šottník 2000;
Rojkovič et al. 2003; Jordan & D’Alessandro 2004). The
goal of this paper is to documented the environmental risk
of an abandoned mine ten years after its flooding. The basis
of the study is a series of water analyses collected irregu-
larly in various time periods. Water analyses characterizing
time intervals before (1986—1990) and after (1990—1994)
the mine’s closure, the subsequent ecological accident on
the Smolník Creek (1994—1995), the period of mine area
remediation (1998—1999) and the 2002—2003 period are
presented (Lintnerová 1996; Jaško et al. 1996, 1998;

Lintnerová et al. 1999, 2003; Šottník 2000). The precipi-
tates and suspended solids analyses were adapted into a
methodology of environmental risk assessment (Pontér et
al. 1992; Lintnerová et al. 1999; Brake et al. 2001; Hren et
al. 2001; Rhoton et al. 2002; Miller et al. 2003). Sulphate,


 and other ions are transported as dissolved species in

the mine groundwater. When exposed to air or mixed with
freshwater, Fe


 is readily oxidized to Fe


 and secondary

Fe precipitates are formed producing even more acidity
(Stumm & Sulzberger 1992; Cornell & Schwertmann
1996). During rapid precipitation and neutralization of
iron oxyhydroxides they scavenge and remove dissolved
elements (Lintnerová et al. 1999; Rosse & Elliot 2000;
Lee et al. 2002). However, these fine-grained solids are
common by transported in suspended form (Ingri &
Widerlund 1994; Brake et al. 2001; Lee et al. 2002).
Ochre-iron compounds coated the creek and the Hnilec
River sediments for 2—3 kilometers from the confluence.
The aim of this study is to evaluate the amount and chemi-
cal and mineral composition of suspended solids in creek
water and indicate its importance for the mine-derived
pollution spreading in the catchment area.

Geology of deposit and environmental risk of the

mining area

The abandoned Smolník ore deposit is situated in the

Slovenské rudohorie Mts in the SE of Slovakia (Fig. 1).

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The volcano-sedimentary ore complex consists of concen-
trated pyrite beds and lenses in graphitic and mica-chlo-
rite schist. Pyrite and chalcopyrite were dominant ore
minerals (Bartalský 1993).

Smolník was a copper-ore deposit of European impor-

tance in the Middle Ages. It was exploited for centuries
until 1990 (Bartalský 1993). AMD in the mining area
were generated by the more than 6 million tones of
abandoned pyrite ore in deposits and disseminated py-
rite in surrounding rocks. As a result of flooding be-
tween 1991 and 1994, acid mine waters discharged
from the flooded mine and contaminated the Smolník
Creek and the Hnilec River (Lintnerová 1996; Jaško et
al. 1996; Šottník 2000). Approximately 3 million tones
of tailings were removed from the Smolník mine
(Bartalský 1993). The tailing impoundment located
near the abandoned mine increases the environmental
risk of the mining area (Fig. 1). The tailings were cov-
ered with wood waste. The average 30 cm layer was not
able to prevent the air oxygen diffusion and pyrite oxi-
dation. Drainage water discharging on the impoundment
base is neutral and iron oxyhydroxides precipitated from
ferrous waters in open drainages (Lintnerová et al. 1999).
Mine dumps, covering about 5 km


 in the vicinity of the

abandoned mine area and other waste, like wall rocks,

metallurgic slag and tailings were disposed in
the area during the various mining periods. The
remediation of the mine area and technical im-
provement of the surface drainage system, the
reinforcement of the creek bottom and the fill-
ing of the mine shaft (by andesite and limestone
crush) decreased the potential amount of water
infiltrating to the underground in the aban-
doned mine area. However, acid mine water en-
riched with metals and sulphate continuously
contaminates surface waters, sediments and soils
in the mine area (Lintnerová et al. 2003; Šoltés
et al. 2003).

Materials and methods

Effluent mine water, the Smolník Creek water

and suspended solid samples were collected at
nine sites (Fig. 1). The creek water quality was
evaluated from the time of active mining in 1989
until 2003. The available data from the hydro-
logical and chemical database of the Slovak Hy-
drometeorological Institute (SHMI) and other
unpublished data were used (Jaško et al. 1996,
1998; Šottník 2000; Rojkovič et al. 2003).


Mine water samples were collected from the

new drainage of the abandoned mine (SM-2),
waste dump channels (SM-3, SM-5), tailing
drainage (SM-OD) and from the Smolník Creek.
SM-1 is uncontaminated water. SM-4 and SM-6

are samples from zones of the mine and tailings drainage wa-
ter mixing with creek water (mixing zone 1 and 2). The sample
points SM-8 and SM-9 were located about 11 and 16 km re-
spectively downstream from the abandoned mine. Two
samples from Hnilec River water were taken to monitor
changes in its water composition. Sample H-0 was located
upstream from the confluence and H-1 at the confluence
with Smolník Creek (Fig. 1).

Water samples were collected in five sampling periods

from June 2002 to July 2003 in variable hydrological con-
ditions. August 2002 was a period with the high precipita-
tion in the whole Central European region and the creek
water runoff was about 2.5 times higher than average. In
the remaining four sampling periods (June 2002, October
2002, April 2003, July 2003) flow in the Smolník Creek
were close to the average amount of 1 m



Conductivity, Eh and pH values of each 44 samples were

measured in the field. The collected water samples were fil-
tered on site through 0.45  m pore diameter cellulose ni-
trate membrane. Total Fe, Al, Mn, Ca, Mg, K, Na, Ba, Hg,
Zn, Pb, Ag, As, Sb, Se, Co, Ni, Cr, V, Cu, and Cd were
analysed in the first acidified (pH = 2) aliquot by AAS and
ICP-AES methods. The second un-acidified aliquot was
used to determine major anion concentrations (SO



, Cl





) by standard colorimetric, volumetric and gravi-

Fig. 1. Location of the Smolník mine (SM-2) and the monitoring points in the
Smolník Creek selected in 2002—2003.

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metric methods. Fe


 was determined in the third stabilized

aliquot by redox titration (KMnO


). The values of total dis-

solved solids (TDS) were expressed as a sum of analysed ions.

Suspended solids and precipitates

The preliminary distribution of two grain-size fractions

of suspended solids was determined. Weight suspension
was captured by continual filtration of creek and river wa-
ter in June 2002. Waters were pumped and filtered through
1  m cellulose filters and through standard 0.45  m mem-
brane at the SM-4, SM-6, SM-8, H-1 and H-3 sites.
Samples H-1 and H-3 were taken from the Hnilec River at
the creek confluence (H-1) and near the point where the
Hnilec River flows into the water reservoir Ružín (H-3).
The pre-weighed filters with captured solids were dried at
105 ºC and were weighed again. The first result was used
to find out the two effective methods – decantation for
suspended solids collection in large volume and mem-
brane filtration for quantitative evaluation (Pontér et al.
1992; Brake et al. 2001; Hren et al. 2001; Rhoton et al.
2002; Miller et al. 2003).

Depending on suspension quantity, 30 to 140 l of water

was taken from the creek. The suspension was decanted for
24 hours. The obtained samples were dried at 40 ºC (for min-
eralogical characterization) or at 105 ºC (for chemical analy-
ses) and homogenized. Besides the mass content, the mineral
composition, organic matter content and acid insoluble resi-
due (IR) of suspended solids were determined. This method
was applied in August and October to check different hydro-
logical conditions and two sets of the creek site samples
(SM-1, SM-4, SM-6, SM-8, SM-9) were collected.

Amounts of suspended solids were evaluated by

0.45  m membrane filtration simultaneously with water
sampling. Because of very low total mass the cumulative
suspended solid samples were collected in 3—5 days by
filtration of 10 to 20 l of water depending on the sus-
pended amounts. Wet samples were stored in acid
leached plastic bottles and transported to the laboratory.
The accumulated samples were dried at 105 ºC and used
for chemical analyses.

Fe oxyhydroxide precipitates were collected in the

Smolník Creek (in the vicinity of the mine water effluent)
and in tailings channels. Mineralogical analyses were per-
formed on samples dried at room temperature and on
samples dialysed in de-ionized water. The same precipitate
samples dried at 105 ºC were used for chemical analyses.

The mineralogical analyses of suspended solids and pre-

cipitates were carried out by X-ray diffraction technique
on the Philips powder diffractometer (model PW 1710, us-
ing Ni-filtered CuK  radiation at 20 mA and 40 kV).
Phase mineral analyses and chemical composition of pre-
cipitated particles were determined using transmission
electron microscope (TEM) Jeol JSM equipped with an
energy disspersive X-ray detector (LINK 1060).

The total content of organic carbon (TOC) was deter-

mined using C-MAT 550 Ströhlein equipment. The stan-
dard EGME (ethyleneglycol monomethylether) method
was used to determine the specific surface area of sus-
pended solids and precipitates.

For chemical analyses, dry samples of suspended solids

and precipitates were digested in concentrated HNO



85 ºC for two hours (Pontér et al. 1992; Rhoton et al. 2002
and others). The contents Fe, Al, Ca, Mg, Na, K, Cu, Mn,
Zn, Pb, As in the supernatant were determined by the stan-
dard AAS and ICP AES methods. IR was determined in
both cumulative and decanted samples by standard gravi-
metric method. IR determination allows recalculation of
metal concentrations on acid dissolved base (ADB) and
identification of the amount of metals released from the
mine in different sampling periods.

Results and discussion


The Smolník Creek water from 1986 to 2000

Mining activity has decreased water quality in the

Smolník Creek, as is documented by analyses taken at the
monitoring point B-68 (SHMU monitoring net) (Table 1).

Table 1: Average, minimum and maximum (in brackets) values  of water collected in B-68 (SM-9), data in period 1986—2000 provided
by the Slovak Hydrometeorological Institute (SHMI).

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This point is identical with the point SM-9 (Fig. 1) and is
situated approximately 16 km downstream from the mine
close to the confluence of the Smolník Creek and the
Hnilec River. The water effluent from the exploited mine
seriously polluted the creek water by permanently adding
metals (Cu, Zn, Fe) and sulphate (Table 1, Fig. 2).

The analyses of water that characterize the period flood-

ing of the mine between 1991 and 1994 are shown in
Table 1, when AMD did not discharge from the mine into
the Smolník Creek. The data illustrate relative improvement
of the Smolník Creek water quality. In the flooding period
pH of stream water increased to 7.0—8.0 and concentrations
of metals and sulphate decreased. In comparison with the
previous period the average concentration of Fe, Cu, Zn and
sulphate ions decreased several times. However, Fe and Zn
contents were still higher than the limit (CD 98/83/EC). It
is possible, that these and the other metals could be exten-
sively released from polluted bank sediments or leached
from mine wastes located in the vicinity of the mine.

AMD from the mine started to penetrate into the

Smolník Creek again, after total mine flooding. A rapid
decline of water quality recorded from May 30


 to Au-

gust 10


 1994 resulted in the death of fish and the break-

down of the creek’s ecosystem (Table 2, Fig. 2). Strong
acid water mobilized Al and other metals toxic to biota
(Jaško et al. 1996; Lintnerová et al. 1999; Šottník 2000).
The metal pollution of the creek water increased sud-
denly in 1994 and it was comparable to the pollution ob-
served during the time of active mining (Table 1).
Acidity and metal contamination of the creek water re-

mained high during the following two years (1994—1995).
The chemical composition of the creek water relatively
improved in the next six years (1996—2001) and only the
Fe and Zn contents were higher than the EC limit. Gener-
ally, two processes, spontaneous change in the mine wa-
ter-rock system after mine flooding and the mine area
remediation (1997—1998) improved water quality to the
observed level.

Abandoned Smolník mine

The composition of discharged AMD from June 1994 to

July 2000 is shown in the Table 3. In June 1994 water in
the Pech shaft was strongly acidic (pH = 2.94) and had
high contents of Fe, Mg, Al, sulphate and other metals
(Jaško et al. 1996). Increased contents of Cu and Zn
(Table 3) occurred at the beginning of the “first flush”
(June—July 1994). High concentrations of sulphate in-
creased total dissolved solids (TDS) from 7 to 17 g/l in ef-
fluent AMD in October 1995 probably because the AMD
was pushed out from the mine depth. This can be sug-
gested on the basis of the water composition from Pech
shaft sampled in 1995, where the 41 g/l TDS in depth
105 m and 46 g/l in depth 265 m were determined.

The shaft was filled in 1997 and after that it was not

possible to sample deep parts of the abandoned mine. At
the same time, new drainage (SM-2) was constructed to
capture the generated AMD. TDS concentration of water
effluent from the new drainage was approximately 5 g/l
and its acidity was buffered to pH 3.8 (Table 4). Decreasing
contents of dissolved ions in comparison with 1994—1995
levels could result not only from stabilization of chemical
processes in the flooded mine but probably also from re-
duced volume and rate of movement of waters flowing
into the mine system. The improvement of the creek bot-
tom and decline of its permeability and the channelling of
meteoric water away from the mine area decreased a vol-
ume of infiltrating water. On the other hand, the aban-
doned mine produced approximately 860 m


 water per

day and it was a stable source of AMD in the area. Con-

Fig. 2. Variation in concentration of Fe and pH values in the Smolník Creek in 1986—2000 (monthly data) according to the SHMI (Slovak
Hydrometeorological Institute) data.

Table 2: Water pH, sulphate and metal concentration at site B-68
(SM-9) during 1994.

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sidering the water composition, AMD discharged from
the new drainage (SM-2) is generated in the near-sur-
face part of the mine and/or in mine waste. It is possible
that the new drainage reclaimed a large area probably
mine dumps too. Strongly acid water with high concen-
tration of dissolved metals was formed in the mine adit
Karitas (SM-Kar) as well as in other old works (SM-3 and
SM-5) (Table 4).

Tailing impoundment

Tailing impoundment is the second important source of

pollution connected with mining located in the mine vi-
cinity. The major part of tailings is milled rock material
from the deep part of the deposit where pyrite was en-
riched with As. The high As-content is a typical feature of
the discharging water and precipitates formed in tailing
drainages (Lintnerová et al. 1999). Mobilization of the re-
dox sensitive elements Fe, S, As, Mn, partially Co are ob-
served at SM-OD (Table 4). Higher contents of elements in
water and relatively low Eh (4—50 mV) were observed es-

Table 3: Values of mine water analysis in 1994—2000 (Jaško et al. 1996, 1998, and authors and other unpublished data). For 1999 and
2000 average values were used.

Table 4: Average, minimum and maximum (in brackets) values of mine water from abandoned mine (SM-2), tailings (SM-OD) and other
AMD (SM-3, SM-5, SM-Kar) contaminated sites from the Smolník Creek collected in 2002—2003.

pecially in one tailing channel. This can explained in-
creased contents of the mentioned elements as well as Ni
and Zn in water, over the 2002—2003 monitoring periods
(Fig. 3). The major portion of mobilized iron is accumu-
lated (due to air oxidation) in drainage channel sediments
and in mud reservoirs under the impoundment. The dis-
solved iron content (1.55 to 8.41 mg/l) which enters the
Smolník Creek may be a fraction of iron mobilized by tail-
ing pore water (Table 4). The relatively high sulphate



tent in the drainage water (106 to 405 mg/l) is the result of
primary pyrite oxidation in tailing and secondary anion/sul-
phate desorption from or iron oxide phases transformation in
near-neutral conditions (Rosse & Elliot 2000; Lintnerová
& Šefčíková 2002). Acid water (pH 3.4—3.9) with high sul-
phate content (1380 to 2080 mg/l) and metal concentrations
(Al 14.6—72.8 mg/l, Cu 2.1—16.8 mg/l, Mn 4.9—19.4 mg/l)
flow out continuously in small volumes from some parts of
the dam and indicate pyrite oxidation in the tailings. The
oxidation of sulphide minerals and leached, acid and ce-
mented zones were recognized in the upper layer of tailing
material in the depth of 40 to 110 cm (Lintnerová 2000).

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The point SM-4 is situated about 200 m downstream

from the site where AMD enters the creek water and is ho-
mogenized with creek water – this is the first mixing
zone.  Increased contents of Fe, Al, Cu, Zn, Mn, Cd, Co, Ni
and sulphate ion in water result from this AMD effluent
running into the Smolník Creek. SM-2/SM-4 ratios of wa-
ter concentrations were used to illustrate the relative dilution
of the AMD elements in mixing zone. The concentration of
Al decreased more than 100 times and despite this fact the
Al exceeds the 0.2 mg/l concentration lethal to fish in wa-
ters (EC limit; Croman & Schofield 1979). The contents of
iron (both Fe


, Fe


) decreased about 90 times, Mn, As,

Co and Zn decreased 38—54 times and concentrations of
other elements (Ca, Mg, Cu, Ni, Cd) were reduced less
than 30 times. The comparison of water analyses in SM-4
during a nine year period (1995—2003) shows substantial
lowering of dissolved solid concentration or water pollu-
tion over time (Jaško et al. 1996; Lintnerová et al. 1999;
Šottník 2000). The volume of effluent water (30 l/s and
more) decreased to the present level (10 l/s) approxi-
mately one year after the improvement of the drainage sys-
tem in 1997—1998.

It is typical that the concentration of As, Ca, Mg, K, Na,

sulphate as well as some other metals (Cd, Zn, Ni and Mn)
increased in the second mixing zone (SM-6) below the site
where tailing drainage flows into the Smolník Creek water
(Table 5 and Fig. 4). The decrease of the water element con-
centrations can be seen between SM-6 and SM-8. These
points are 10 km apart. Changes in the creek bottom mor-
phology, small tributaries and leaching of old mine wastes
can affect the creek water composition. It was found that re-
dox conditions in the water changed from point SM-6, and
more reducing condition in the downstream water could re-
sult in the higher mobilization of redox sensitive elements
and increased relative contents of dissolved metals ob-

Fig. 3. Metals and sulphate concentrations in tailing water (SM-OD)
in the 2002—2003 period.

Fig. 4. The average values of metals in the Smolník Creek water in 2002—2003 calculated from analyses obtained during the five monitor-
ing periods.

The Smolník Creek water in 2002—2003

The composition of creek water from five monitoring

points according to observation in periods from June 2002 to
July 2003 are presented in Table 5 and are plotted in Fig. 4.

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Table 5:  Non-contaminated (SM-1) and contaminated creek water substantiate as the average, minimal and maximal (in brackets) values
performed in 2002—2003 in five sampling periods.

served at SM-8 and SM-9 (Cornnell & Schwertmann 1996;
Nickson et al. 2000). Old rock-wall dumps and weathered
piles of metallurgic slag can be another potential source of
toxic elements (Cu, As, Cd, Se) (Šoltés et al. 2003). Sample
H-0 was taken from the River Hnilec above the confluence.
Water samples from the third mixing zone (H-1, below the
confluence of Hnilec River and Smolník Creek) docu-
mented an overall decrease in metals concentrations and
their variations below the river and creek confluence. Only
Fe and Zn exceed the limit in the river. However, the water
in the confluence is not mixed enough, which is clearly vis-
ible, and metal contents change within a small distance.

Mine and tailing precipitates

The typical ochre iron oxyhydroxides were accumulated

in drainage channelling water from the mine and tailing and
they coat the bottom of the Smolník Creek. Jarosite








), schwertmannite (Fe








) and

goethite (FeOOH) were the principal phases identified in the
precipitates generated from the effluent AMD (Lintnerová
1996; Lintnerová et al. 1999). These mineral phases were

identified in samples collected at SM-2 and SM-5 sites in
2002—2003 (Fig. 5). The white precipitates occurred in nar-
row parts of the first mixing zone near the abandoned mine.
Basaluminite (Al









0) was identified in precipi-

tates sampled in a white strip earlier  (Šottník 2000). In spite
of this and theoretical calculations (not presented in this pa-
per) no Al-oxyhydroxide phases were identified in the white
precipitates by TEM/LINK analyses. Phases were unstable,
released sulphate ions and changed to (low-crystalline) goet-
hite in a 4—6 month span of time. Transformation could be
followed by increase of specific surface area. Ferrihydrite







O) and goethite are common phases identified in

tailing precipitates, occasionally found with gypsum
(Lintnerová et al. 1999; Lintnerová 2000). Two X-ray bands
of ferrihydrites were seen in low crystalline solids collected
in various periods (Fig. 5; Bigham et al. 1990, 1996; Rhoton
et al. 2002). The specific surface area values of the
ferrihydrite/goethite precipitates were in the range 500 to
700 m


/g. However, the highest values were determined in

dialysed samples. The specific surface areas of AMD-precipi-
tates (schwertmannite, jarosite, goethite) were in the range
150 to 400 m


/g with a tendency to increase with decrease

of sulphate content (Lintnerová & Šefčíková 2002).

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The ochre accumulations were sometimes observed in

various distances downstream from the mine and at the
creek-river confluence. The intermittent precipitation of
solids indicated dependence on changes in water pH-Eh
and temperature conditions in various climatic and hydro-
logical seasons. Low crystalline ferrihydrite and goethite
were identified in the X-ray profile of samples collected in
SM-8 and SM-9 and indicated decreases of acidity and
sulphate content.

Tailing precipitates were enriched with Zn, Cu, Mn, Ca

and especially with As. Processing additives, like lime or al-
kali salts changed the neutralization potential of tailings,
which could be extensively leached. It is typical that in-
creased Ca content in water indicate a generation of acid
sulphate pore water (Jambor 1994; Blowes & Ptacek 1994).
Both, generated acidity and redox condition enhanced mo-
bilization of Fe


, As


 and other redox sensitive ions. This

indicated composition of precipitates enriched in As and

Mn, generated within open channels. The precipitation of
dissolved elements, complexation with or sorption on the
iron oxyhydroxide phases is pH dependent. High content of
sulphate and other inorganic and organic ligands can play
an important role in mineral phases stability and possible
release of bounded elements (Ingri & Widerlund 1994;
Lintnerová et al. 1999; Nickson et al. 2000; Lee et al. 2002;
Munk et al. 2002; Lintnerová & Šefčíková 2003). Iron pre-
cipitates originating from abandoned mine water accumu-
lated Al, Mg, Pb, As and Cu at a higher rate than tailing
precipitates. Se, Sb, Co and Cr were also detected in the pre-
cipitates generated from water, which had leached old mine
dumps and works (SM-5, SM-Kar) (Table 6).

Suspended solids

Suspended solids composed of particles above 0.45  m

grain size were captured on the membrane when water was

Fig. 5. X-ray diffraction patterns of the mine and tailing precipitates collected in June 2002. J – jarosite, Sch – schwertmannite, G – goet-
hite, F – ferrihydrite, Q – quartz, Ch – chlorite, Sl – mica.

Fig. 6. Grain size distribution of water suspended solids sampled in June 2002. B – Mass distribution of suspended solids captured on
0.45  m membrane. C  – Mass and Fe content distribution. (e.g. Jun-4 = SM-4 sampled in June 2002, etc.) D – Mass and Fe co-relation
(anomalous August 2002 values were omitted).

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filtered or were accumulated from water in the sediment
pots. Preliminary results have shown, that  the particles
from 1 to 0.45  m in size constitute a considerable mass of
suspended matter in comparison with the particles  > 1  m.
These large particles were not evaluated separately
(Fig. 6). The fraction passing through 0.45  m membrane
filter was taken as dissolved matter although it also in-
cludes a colloidal component.

The total mass of suspended solids obtained from one li-

tre of the Smolník Creek water varied from 7 to 72 mg/l
(Tables 7 and 8, Fig. 6). The amount of suspended solids in
the non-contaminated part  < 10 mg/l can increase up to
70 mg/l downstream from the mine site. However, seasonal
change of water volume in the creek is the main factor influ-

Table 6: Chemical analysis of mine drainage precipitates – not detected.

Table 7: Characteristics of suspended solid samples collected by
sedimentation and decantation in two periods (August (SM-4/Aug)
and October (SM-1/Oct) 2002). nd – not detected.

Table 8: Chemical composition of suspended solid samples (captured on  > 0.45  m membrane) in the Smolník Creek in 2002—2003.

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encing the total amount of suspended solids transported by
the creek waters. Ignoring the high water outflow values in
August 2002, the contents of suspended solids increase 2—3
times below the mine and the largest amount was captured
at SM-6 and SM-8 sites during each monitoring period
(Fig. 6B,C). Increased content in the SM-6 site recorded the
inflow of the partitioned tailing precipitates into the creek.
The interpretation of the SM-8 maximum is not simple be-
cause various old mining wastes could be leached and iron
and other metals would supply the stream water. Regardless
of that, the increased amount of suspended solids enriched
by iron at distances of 11 km to 16 km from the mine shows
that suspended solids could transport a comparable mass of
mine-derived elements as was transported in water dis-
solved form (Tables 5, 7, Fig. 7). If 30 mg/l of suspended
solids contained approximately 10 % of mine-derived Fe,
then each litre of water transported 3 mg of Fe in suspended
solids at the SM-8 site. The mine-derived content is the Fe
content at SM-8 reduced to the SM-1 value.

Seasonal changes of creek outflow affected not only the

amount but also the quality of suspended solids The de-
canted samples accumulated in August and October 2002
were used to estimate, mineral composition, organic carbon
and insoluble residue (IR) in samples (Table 7). Seasonal
changes caused IR values in the range 17 to 74 % of a
sample. If the August 2002 values are omitted, IR is in the
range 17 to 40 % (Tables 7 and 8). The identical mineral as-
sociation, chlorite, mica/illite, feldspar and quartz, was
identified in all decanted samples. No well-crystallized iron
oxyhydroxide phases were found in the X-ray pattern of

Fig. 7. Geochemical co-variation in Fe, IR and selected metals in the suspended solids.

“fresh” suspended solid samples. The fine particles and the
aggregate grains (50—100 nm) of iron oxide phases were
distinguished by means of TEM investigation, on the basis
of extensive Fe content and typical acicular flocks to
needle like and short lath grains. Sulphur content was obvi-
ously low, frequently in the range of the analytical error.
We suggest that amorphous aggregates of hydrated iron ox-
ide species (like fine crystalline ferrihydrite to goethite
phases in precipitates) dominate in the suspended solid.
However, a lot of individual particles were so fine that they
passed through 0.45  m pores in the membrane filter. On
the other hand, the high “salinity” of the creek water con-
tinually supplied by AMD could elevate flocculation of hy-
drated iron oxide nano-particles or colloidal matter which
explained occurrence of the typical aggregate of iron
oxyhydroxides in suspended solids. High content of min-
eral phases in suspended solid could increase sedimentation
rate of solids and direct various sorption or dissolution pro-
cesses in the water-sediment interface.

The values generally above 200 m


/g documented a

high specific surface area of the suspended solid samples
(Table 7). Observed variance in specific surface area values
and organic carbon contents is connected to some extent
with seasonal creek outflow changes (Table 7). The samples
enriched with organic matter (7.2 to 9.1 %) were collected
in the moderate creek runoff season (October 2002). The
higher content of organic carbon may be a result of sorption
on enlarged (due to hydrated iron oxide precipitation) spe-
cific surface area of suspended solids. On the other hand, or-
ganic species with high molecular weight like humid acids

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could stabilize hydrated iron (III) oxides in dissolved or col-
loidal form in river water and prolonged iron transport
(Boyle et al. 1977; Ingri & Widerlund 1994; Zuyi et al.
2000). The organic content in precipitates could be con-
nected with microbial activity in AMD system, which sub-
stantially increased the rate of pyrite oxidation (Gould et al.
1994). However, a municipal pollution and leached organic
species from soil would be a more probable important
source of organic matter in suspended solids.

Element distributions

The results of chemical analyses documented the in-

creased content of Fe, Al, As, Pb, Cu in suspended solids
in the contaminated part of the creek (Table 8). The

Table 9: The chemical composition of suspended solids figured on acid dissolved base (ADB), average values.

samples collected in the medium creek runoff have higher
than 50 % of acid (HNO


) dissolved phases of suspended

solids mass (Tables 8 and 9). The iron oxyhydroxide
phases composed a substantial part of the acid soluble part
of the suspended solids, which document the different Fe
contents of suspended solids in contaminated and uncon-
taminated (SM-1 and H-0) streams (Fig. 7). The content of
Fe increased from 2—3 % in SM-1 to 6—20 % downstream
from the mine (SM-4, SM-8). Various factors, mainly the
pH dependence of precipitation of Fe oxyhydroxides, the
composition of water from individual mine-derived
sources, organic carbon, sulphate and alkali ion (ionic
strength – salinity) can change element contents and re-
duce geochemical correlation of Fe with other elements
(Fig. 7). However, the typical feature of systems influ-

Fig. 8. Comparison of Fe, Al, Cu and As concentration in SM-6 and SM-8 samples of suspended solids and values recalculated on acid dis-
solved basis (ADB). July 03* – analyse from SM-9 was added.

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enced by AMD is clearly visible. The increased content of
Al in the dissolved part of all suspended solids samples is
evidence that dissolved Al is removed either via Fe oxides
precipitation and/or sorption on re-suspended sediments
or organic matter or via flocculation into colloids
(Sholkowitz 1978; Chester 2003). The samples collected
in the mine-creek (SM-4) and the tailing-creek (SM-6) wa-
ter mixing zones have similar microelement contents of
fresh drainage precipitates and prime mine water composi-
tion (Table 8). Some enrichment with Mg and Pb could be
distinguished precisely in this mixing zone below the
mine. Analogously, increased contents of As and Ca in
suspended solids from the second mixing zone (SM-6) sig-
nalized partitioned tailing precipitates transported by
drainage water and potential change in water composition.
The contents of Ca but also of K, Na, Mn, Zn in suspended
solids are depleted in comparison with SM-1 because of
leaching and generation of dissolved species due to neu-
tralization. The element concentrations recalculated on
the acid dissolved basis (ADB) clearly eliminates seasonal
outflow changes and show variance in the amount of
mine-derived elements transported in suspended solids
(Table 9). Results indicated that more turbulent (high run-
off) water conditions diluted the content of potentially
mine-derived metals, but the total yield of metals was not
changed dramatically (Fig. 8, Table 9). The amount of
main elements (Fe, Cu Al and As) is similar in samples col-
lected in the same site of stream during the various out-
flow seasons. This could document stabilized input of the
studied elements into the stream and assumed potentially
stabilized solid flux into the river (Fig. 8).

The contents of Cu, Zn and Mn were higher in solids cap-

tured far downstream from the mine because of the pH-de-
pendent metals co-precipitation with and sorption on the Fe
oxyhydroxides or other suspended phases in more neutral
creek water (Tables 8, 9, Fig. 8). Comparison of the H-0 and
H-1 samples shows the relative content of the mine-derived
elements transported by suspended solids into the Hnilec
River. The elevated metals concentrations in solids (Zn,
Mn) below the confluence could be a sum of metals derived
from the mine and other areas transported by the Hnilec
River water. Some depletion on K, Na, Ca, Mg and Mn was
still apparent in suspended solids below the confluence.
Due to imperfect mixing and/or dilution of the creek with
river water along the creek site bank for 1 to 3 km below the
confluence there was prolonged acid reaction (pH 5.6 to
6.8) in the water and the water-sediments interface. It can be
assumed, that increased content of alkali and hydro-carbon-
ate ions in the Hnilec River water admit flocculation of col-
loids (hydrated iron, Al, Mn oxides, and other mineral
solids) and its sedimentation on the bottom (Boyle et al.
1977; Sholkowitz 1978; Chester 2003).

The amounts of metals, transported in a certain span of

time were calculated from the obtained results (Table 8). To
document the mass of metals transported to the river by av-
erage creek outflow (1 m


/s) the sampling site SM-8 was

situated near the confluence. If 30 mg/l (average amount)
of suspended solids contained 10.79 % Fe, 0.136 % Cu
and 0.055 % Zn, then it can be estimated that the creek

transported 2.590 kg/day of suspended solids with 280 kg
of Fe, 3.54 kg of Cu and 1.44 kg of Zn. If we calculate this
for the dissolved forms of metals (Table 5) we can estimate
that 238.5 kg of Fe, 13.05 kg of Zn and 1.99 kg of Cu were
transported by water per day at the point SM-8.

Suspended solids in environmental risk assessment

The results indicated that precipitation of iron oxide

phases in the mine-creek mixing zones and seasonal
changes of water volume in the creek are major causes influ-
encing the amount of suspended solids transported by water
in the contaminated part of the creek. The suspended solids
transported the substantial dose of iron and other elements,
which can be the same or even higher than is removed in
dissolved form. However, lot of questions concerning the
suspended solids grain-size definition (particles above
0.45  m) and importance of colloidal phase quantification,
objectivity and reliability of quantitative determination by
various methods and other problems arise. Only some as-
pects, such as the proportion of mineral and organic phase
versus seasonal outflow and/or the mine flux of Fe and
other typical mine derived elements into the creek catch-
ment, were discussed. The results indicated that the
water-suspended solids—precipitates—sediment system is
compl icated and many processes at the water-solid interface
must be understood in such a multiphase system (Boyle et
al. 1977; Sholkovitz 1978; Ryan & Gschwend 1992; Brake
et al. 2001; Hren et al. 2001). It is not optimal to use this
method in broad environmental risk assessment, because
simple and representative methods could be recommended.
However, for the quantitative evaluation of suspended sol-
ids, it is inevitable to use various geochemical, transport or
space-time models, generated according to obtained data.
Separation and analyses of suspended solids can evaluate
the immediate toxic element content in stream water
(Rhyan & Gschwend 1992; Munk et al. 2002; Rhoton et al.
2002). Since it can be exactly selected at a relatively short
distance from the sources, it can be more precise and cost
less than sequence (river) sediment analyses. Iron oxides are
common natural phases, which effectively attenuate (toxic)
element concentrations of water. However, they occur not
only in suspended solids, but also in colloids, which extend
transport and thus catchment pollution. Mixing of concen-
trated AMD with creek water, or mixing of polluted creek
water with river water, gradually changed its ionic strength
and/or the composition of the water and precipitation and
stability of particulate (and colloid) mineral phases (Ingri &
Widerlund 1994; Zuyi et al. 2000; Chester 2003). Goethite
as a widespread Fe oxide phase and end-member of various
hydrated phase transformations can serve as a pollution sig-
nal in a potential risk area (Bigham et al. 1990; Cornell &
Schwertmann 1996; Rhoton et al. 2002).


Two important conclusions concerning the composition

of the water from the abandoned mine can be presented.

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Firstly, the relative stabilization of AMD composition was
observed in a relatively short time (approximately 9—10
years) after the mine flooding. Secondly, the high pollution
potential of medium acid and mineralized AMD (pH 4 and
5 g/l TDS) was documented. AMD effluent from the mine is
relatively low (830 m


/day) in comparison with the

Smolník Creek outflow, which dilutes AMD at least one
hundred times. The dilution is not sufficient, because unac-
ceptable contents of metals (Fe, Cu, Zn) in the creek water
were detected 16 km downstream from the mine at the
confluence with the river and the metal pollution can rise
seasonally especially during dry periods. The observed
properties of water and the mine area indicated that such
processes could pollute the creek catchment for a long time.

A natural mechanism of water cleaning precipitation of

iron oxyhydroxide mineral phases was detected. Ex-
tremely fine-grained precipitates were transported by
stream water as suspended solid. Two to 3 times higher
contents of suspended solids were generated in the con-
taminated part of creek water and showed a definite ten-
dency to increase over a distance of 11 to 16 km
downstream from the mine. The suspended solids analyses
documented the immediate impact and measure of mine-
derived pollution enlargement in the catchment. Increased
contents of metals and other toxic (redox and pH sensi-
tive) elements, phase instability and enlarged specific sur-
face of suspended solids can affect water quality and biota
living conditions. The evaluation of suspended solids in-
creases the objectivity of environmental impact assess-
ment in the catchment area effected by AMD.


This research was done under the

Comenius University Bratislava subproject of program
PECOMINES directed by the Joint Research Centre Euro-
pean Commission (Ispra, Italy) with funding support from
the Slovak Ministry of Education and Slovak VEGA fund
(Project No. 1/0010/03). Analyses were performed in the
Slovak State Geological Survey Laboratory in Spišská
Nová Ves, in the Laboratory of Geological Institute of Slo-
vak Academy of Science in Bratislava and Banská
Bystrica and in the Geological Departments of Comenius
University in Bratislava. We are thankful to all these labo-
ratories for their prompt cooperation. We are also thankful
to the Slovak Hydrometeorological Institute for enabling
us to use data from their water database. We appreciated
collegial field cooperation with Vlado Jaško, Dr. Soňa
Cicmanová and Prof. Igor Rojkovič. Great thanks go to
the two anonymous reviewers  and Dr. Peter Komadel for
his helpful comments and text improvement.


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