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Atmospheric Environment 39 (2005) 7570–7579

www.elsevier.com/locate/atmosenv

Current and past mercury distribution in air over theIdrija Hg mine region, Slovenia

Joze Kotnika,�, Milena Horvata, Tatjana Dizdarevicb

aDepartment of Environmental Sciences, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniabIdrija Mercury Mine, Arkova 43, SI-5280 Idrija, Slovenia

Received 7 December 2004; received in revised form 30 June 2005; accepted 30 June 2005

Abstract

Mercury in air over the Idrija region, where the world’s second largest mercury (Hg) mine is located, decreased

significantly in the last decade, from more than 20,000 ngm�3 in the early 1970s to values below 100 ngm�3 in the

1980s, and finally reached a level of 10 ngm�3 or even lower at the summer of the year 2004.

The air concentration of Hg was continuously monitored after closure of the Hg mine. Hg0 in air was mapped in

November 2003 at over 100 locations in the Idrija region during a 3-day period under different weather conditions, and

the concentrations found were between 2.5 to over 2000 ngm�3. The Hg concentration in air was mostly below

10 ngm�3. The highest values were observed in the near vicinity of the former smelting plant, as well under its chimney.

Elevated concentrations were also observed at some other locations in Idrija town. Mercury evaporation from topsoil

was measured continuously for a 24 h period at two heavily polluted locations in Idrija and 50 km downstream the

River Idrijca at Baca pri Modreju. The average Hg concentration in air at Baca pri Modreju was 5.5 ngm�3, with an

average Hg flux from soil to atmosphere of 34 ngm�2 h�1. At the site in Idrija the average Hg concentration in air was

11 ngm�3 with an average Hg flux from soil to the atmosphere of 84.4 ngm�2 h�1.

r 2005 Elsevier Ltd. All rights reserved.

Keywords: Mercury; Air; Evasion; Flux chamber; Idrija

1. Introduction

In over 500 years of Hg mining history in Idrija, over

12 million tons of Hg ore was excavated, from which

100,000 tons of elemental Hg and 7618 tons of cinnabar

was extracted (Mlakar and Drovenik, 1971; Mlakar,

1974; Cigale, 1997). During smelting of Hg ore more

than 35,000 tons of Hg was lost into the environment,

mostly to the atmosphere as Hg0 vapour was deposited

on the banks or into the River Idrijca as smelting

residues. High-Hg concentrations were found in all

e front matter r 2005 Elsevier Ltd. All rights reserve

mosenv.2005.06.061

ing author.

ess: joze.kotnik@ijs.si (J. Kotnik).

environmental compartments such as water, air, soil,

sediments and vegetation. The first extensive research on

Hg cycling in Idrija town and its vicinity started in the

early 1970s of the past century (Kosta et al., 1974). At

the beginning of the 1980s Hg production rapidly

decreased; at the same time there was an increase in

investigations of Hg cycling in Idrija. In the 1980s very

few measurements of Hg concentrations in air or other

environmental compartments were made. After 1990

Miklavcic and Horvat started systematic Hg measure-

ments in air over Idrija. In 1994 Gosar (1997) and

coworkers started the first geochemical mapping of Hg

concentrations in air. In the last decade many researches

on Hg were carried out. Hg cycling was studied in the

d.

ARTICLE IN PRESSJ. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–7579 7571

whole environment, together with its impacts on humans

and their health (Biester et al., 1999, 2000; Falnoga

et al., 2000; Gnamus et al., 2000; Gosar et al., 1997a, b,

2002; Horvat et al., 2003; Kobal et al., 2004; Kocman

et al., 2004).

In the initial mining activities in the Idrijca Valley

(1490–1508) only carboniferous schist containing

elemental Hg was excavated. Hg was extracted by

panning. It is estimated that about 180 tons of Hg was

lost to the environment, mostly to the River Idrijca.

After the discovery of cinnabar ore (1508), panning was

completely replaced by smelting the ore in simple clay

vessels. The Hg ore was smelted at several locations

around Idrija until 1652, when a new smelting plant was

built on the left bank of the Idrijca. Smelting residues

were discarded into the river. The smelting recovery was

around 65%. It is estimated that in that period around

13,000 tons of Hg was lost to the environment, mostly to

the atmosphere and into the River Idrijca. After 1868

smelting facilities were gradually moved to the right

bank of the river; up to the end of the Second World

War the smelting furnaces were changed several times.

In that period recovery was about 75%: most Hg

(around 20,000 tons) was lost into the atmosphere,

and some of it sank into the ground or was dumped as a

byproduct into the river. In the period 1963–1968

new modern rotatory furnaces were built and the

smelting recovery increased to 92%. Smelting residues

contained 0.005% (Fig. 1). In the period between 1960

and 1995 more data about Hg production and smelting

recovery exist (Fig. 2). During that period 4.2� 106 tons

of Hg ore was excavated from which 9777 tons of

commercial Hg was produced. About 243 tons of Hg

was lost into the environment. Of that amount 168 tons

of Hg was deposited in landfill as smelting residue, 60

tons was emitted into the atmosphere by flue gases, and

15 tons of Hg was released to the River Idrijca in

condensation water. In 1995 the last rotary furnace

ceased operation.

Hg production during Idrij

0

10

20

30

40

50

60

70

1490-1508

1509-1785

1786-1945

1946-196

Am

ount

(×

106

kg)

Fig. 1. Production of Hg d

Nowadays, the main sources of Hg in air in Idrija are

two still active mine ventilation shafts, evaporation of

Hg from the heavily polluted surroundings of the former

smelting plant, mineralized rock dumps of primary or

partially exploited ore, outcrops of the ore deposit, and

ore residues treated in various ways (Car, 1996).

After the Hg mine and the smeltery closure, Hg

concentrations in air have been continuously monitored

at several locations in Idrija and its surroundings.

Monitoring is mostly performed by the Mercury Mine

Research Unit.

The aim of this study was to establish the past and

current extent of Hg pollution in air over the town of

Idrija, its temporal trends and its evaporation rates.

Since Hg sources are spread all around Idrija town and

its near surroundings detailed Hg air concentration

mapping was performed to establish the main polluted

areas in the town. Temporal trends of Hg concentrations

in air were established by regular monitoring of two

locations in the centre of the town and near the two

main mine ventilation shafts. Mercury vapour flux from

ground to atmosphere was measured in order to

establish the rate of Hg exchange between soil and the

atmosphere in the main polluted areas in Idria and its

surroundings.

2. Methods

2.1. Site description

The world’s second largest mercury deposit is located

in the very narrow Idrijca Valley, in the town of Idrija,

50 km W of Ljubljana. Along the valley the River Idrijca

flows through the town of Idrija and merges with the

River Soca (Isonzo in Italy) about 40 km downstream

from Idrija. The River Idrijca joins the River Soca in the

middle stretch at the village of Most na Soci. Both rivers

have torrential characteristics. As the mountains (Julian

a Hg mine operation

0

1961-1977

1983-1995

0102030405060708090100

% r

ecov

eryHg extracted

Hg lost

Recovery

uring mine operation.

ARTICLE IN PRESS

Fig. 2. Losses of Hg during smelting of Hg ore in the period between 1961–1995 (estimated from Idrija Hg mine archives).

Fig. 3. Sampling and measurement locations.

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–75797572

Alps) block air circulation from the northern Adriatic

Sea to the north, annual precipitation is very high and

ranges between 2400 and 5200mmyr�1. The average

winter temperature (between 1960 and 1995) is �5.4 1C,

average summer temperature 10.4 1C and average yearly

temperature in the valley 2.7 1C.

High peaks and steep mountain slopes prevent air

circulation in the valley. The most common winds follow

the geography of the valley. In its upper part the most

common wind direction is S–N and in the lower parts

the prevailing wind direction is E–W. Due to the steep

mountain slopes severe erosion occurs.

Total Hg concentration in air was measured at several

locations in the town of Idrija, and downstream the

River Idrijca to Most na Soci. The study area and

locations are presented in Fig. 3.

The Idrija Hg deposit extends in a NW–SE direction

for 1500m. It is 300–600m wide and 450m thick. In the

period of 500 years of its exploitation 156 ore bodies

were found, 15 in carboniferous shales and 141 in

Permian and Lower and Middle Triasic beds. Cinnabar

is the main ore mineral. In carboniferous shales native

mercury occurs in significant amounts.

Hg evaporation from the ground was measured at two

heavily contaminated locations shown in Fig. 3. The

location in Idrija was chosen in the close vicinity of the

former smelting plant on a meadow, which was heavily

polluted by airborne Hg originating from the smelting

ARTICLE IN PRESS

Table 1

Average agronomic characteristics of the topsoils where Hg flux

measurements were conducted (adopted from Gosar et al.,

1996; Gnamus et al., 2000; Horvat et al., 2002; Kocman et al.,

2004)

Location/parameter Baca pri Modreju Idrija

pH in KCl (�) 7.3 7.2

pH in water (�) 7.6 7.6

Phosphorus—P2O5/mg 100 g�1 5.1 8.6

Potassium—K2O/mg100 g�1 5.0 10.8

Organic matter (%) 3.9 7.9

Total N (%) 0.18 0.54

C/N ratio (�) 12.6 8.5

H+/meqv 100 g�1 1.91 5.04

Na+/meqv 100 g�1 0.0015 0.0018

K+/meqv 100 g�1 0.036 0.105

Ca+/meqv 100 g�1 19.3 24.8

Mg+/meqv 100 g�1 4.33 8.46

Cationic exchange capacity 25.5 38.4

Org. C (%) 2.3 4.6

% sand 72.8 39.1

% silt 15.5 36.7

% clay 11.7 24.2

T–Hg (mgHg g�1) 76.0 333

MeHg (ng g�1) 3–6 65–97

Cinnabar Up to 10%

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–7579 7573

plant. The second location was approximately 40 km

downstream the Idrijca at Baca pri Modreju, in a

meadow, regularly flooded by the river, which carries a

significant amount of eroded Hg to the River Soca and

further to the Gulf of Trieste (Biester et al., 2000;

Bonzongo et al., 2002; Covelli et al., 1999, 2001;

Faganeli et al., 2003; Gosar et al., 1997a, b; Hines

et al., 2000; Horvat et al., 1999, 2002; Kocman et al.,

2004; Rajar et al., 2000; Sirca et al., 1999; Zagar et al.,

2001).

Topsoil from alluvial plains (at the Baca pri Modreju

site) contains less potassium, organic carbon and

organic matter, have a higher C/N ratio and somewhat

lower cation exchange capacity compared to soil at the

site in Idrija. As regards texture, alluvial soil is coarse-

grained, while fine-grained material prevails at the site in

Idrija. As regards to macroelements, calcium is the most

abundant, followed by magnesium and sodium in soils

at both locations (Kocman et al., 2004). Inorganic

parameters and Hg concentrations of soils collected at

both locations are presented in Table 1 (adopted from

Gosar et al., 1997a; Gnamus et al., 2000; Horvat et al.,

2002; Kocman et al., 2004).

2.2. Analytical devices

Total Hg concentrations were continuously measured

since 1999. Measurements were performed by a GAR-

DIS Mercury Analyzer—1A+. The instrument is an

atomic absorption spectrometer using a two-stage gold

amalgamation system. The detection limit of the

analytical device is 1 ngm�3 with a precision of 1%.

The upper limit of detection is 1000 ngm�3.

Mercury mapping and flux measurements were

performed using a Zeeman Mercury Analyzer RA-

915+. The analyzer operation is based on differential

atomic absorption spectrometry using high-frequency

modulation of light polarization. The detection limit of

the instrument for ambient air, industrial and natural

gases is 2 ngm�3 at a flow rate through the instrument of

20 lmin�1. The accuracy of the method is 20%.

2.3. Mercury mapping

The mapping of air Hg concentrations in Idrija town

was performed during 30 October to 4 November 2003.

The weather conditions during the period of Hg

measurements were not very favourable. Wind speeds

were very low in the prevailing S–N direction. Heavy

rainfall and associated low temperatures decreased Hg

evaporation from the ground, which consequently lead

to very low-Hg concentrations at certain locations.

Hg mapping over the town of Idrija was performed

using a portable Zeeman RA-915+ Hg analyzer

installed in a car traversing the roads of the area. The

geometrical coordinates were given by a Magellan

Meridian portable GPS receiver. Both values (Hg

concentration and geographical coordinates) were re-

corded by a portable computer through a appropriate

software. The concentration values recorded at indivi-

dual points were further smoothed into a map using a

computer routine (Golden Software Surfer v. 8.0).

The data sampling times lasted from 2 to 7 h. Air

temperatures were between 6 and 15 1C at the time of

sampling. It should be noted that the measured values

refer to 1.5m above the road surface.

2.4. Mercury flux measurements

Hg evasion was measured using the ‘‘flux chamber’’

technique (Schroeder et al., 1989; Xiao et al., 1991; Kim

and Lindberg, 1995; Ferrara et al., 1998). The increase

of mercury concentration inside the chamber was

measured as a function of time. The flux chamber was

constructed from a 5-mm-thick Plexiglas, which allows a

low-chamber blank and good penetration of solar

radiation. Dimensions of the flux chamber were

60� 60� 30 cm with a removable bottom plate. All

fittings and tubing were made from Teflon and were acid

pre-cleaned. A teflon tube for sampling the external air

was fixed on the upper part of the chamber. The external

and internal air was measured at a constant flow rate of

2 lmin�1. Three inlet ports allowed ambient air to enter

the chamber. The lower edges of the chamber were

sealed using surrounding soil to limit the infiltration of

ARTICLE IN PRESS

Average Hg concentration in air over Idrija

1

10

100

1000

10000

100000

1970 1975 1980 1985 1990 1995 2000 2005

Hg

conc

entr

atio

n (n

g m

-3)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Am

ount

(×

106

kg y

-1)

Idrija town Near smeltery Hg production

Smelting of

contaminated material

Fig. 4. Average Hg concentrations in air over Idrija Town since 1970 (adopted from. Kosta et al., 1974; Gnamus et al., 2000; Gosar et al.,

1997a, b).

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–75797574

outside air. The chamber blank was around 3 ngm�3.

The external air concentration was measured every

15min, while the internal chamber concentration was

measured and recorded every second. The average

concentration for the 15min period was then calculated.

The rate of mercury exchange was calculated using the

following equation (Ferrara and Mazzolai, 1998;

Ferrara et al., 2000; Poissant and Casimir, 1998):

F ¼ðCi � CeÞ �Q

A,

where F is the Hg flux (ngm�2 h�1), Ci and Ce are the

chamber internal and external Hg concentrations in

ngm�3, Q is the flow rate through the chamber (m3 h�1)

and A is the chamber surface area. A very similar

approach using the’’flux chamber’’ technique is de-

scribed in more detail by Ferrara and Mazzolai (1998)

and Ferrara et al. (1998).

3. Results and discussion

3.1. Past Hg distribution in air over Idrija town

High emissions of Hg into the environment resulted in

elevated Hg levels in all parts of the environment in the

Idrijca Valley. The main reason for high-Hg concentra-

tions in air during Hg mine operation was insufficient

smelting of cinnabar ore. In the period between 1961

and 1995 it is estimated that more than 60 tons of Hg

was lost to the atmosphere due to smelting activities

(Fig. 2) (estimated from the archives of the Idrija Hg

mine). The average Hg concentration in smelting plant

flue gases was 17.9mgm3 (20 kg day�1). In the early

1970s, when Hg production was the highest, Hg

concentration in air in Idrija town could reach even

20,000 ngm�3 (Kosta et al., 1974) (Fig. 4). In the late

1970s and 1980s the Hg concentrations in air in the town

decreased rapidly to values below 100 ngm�3 with the

same downward trend of Hg production. The Hg

concentration in air reached levels of over 1000 ngm�3

in 1995 during smelting of heavily contaminated soils

and residue material. After that time, when Hg

production stopped, the Hg concentration in air

decreased dramatically and reached a level of 10 ngm�3

or even lower at the summer of the year 2004.

As a consequence of smelting activities all the

surroundings of the former smelting plant are heavily

contaminated with Hg. Since the beginning of 1970s the

Hg concentration in air near the smeltery decreased

significantly but still remains high and even today it can

reach a value of 3000 ngm�3 (Fig. 4).

Hg concentrations in air in the town of Idrija have

been continuously monitored since the beginning of

1999 by the Idrija Mercury Mine Research Unit. The Hg

concentration is measured once per month at two

locations in the town and near the two Hg mine

ventilation shafts (Fig. 5). Since 1999 Hg concentrations

exceeded 100 ngm�3, and even in two cases 1000 ngm�3,

but only near the Inzaghi shaft. The general trend at all

four locations is the same. Concentrations were only

slightly higher near the ventilation shafts than in the

town, due to closing-down work in the mine. A

significant decrease of average concentrations near the

shafts was observed in 2002 and 2003. At all four

locations higher concentration levels were observed

in summer, most probably due to higher soil and

air temperatures, and stronger solar radiation, and

consequently higher evaporation rates of Hg from

polluted soils. Unfortunately, the wind speed and

ARTICLE IN PRESS

Fig. 5. Hg concentrations in air near Hg mine ventilation shafts and in Idrija Town.

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–7579 7575

direction was not measured together with concentration.

Low ventilation of the valley could be an important

cause of higher summer concentrations.

3.2. Mapping of air Hg concentrations

At the end of October and at the beginning of

November 2003 Hg concentrations in Idrija and its

surroundings were measured in detail. Mercury mapping

in the Idrija Valley was carried out using two different

approaches. The approach using the differential absorp-

tion lidar technique is described in detail by Groenlund

et al. (2005). The second approach was performed using

a portable absorption spectrometer installed in a car

together with GPS measurements. Hg concentrations

were measured at more than 100 locations in Idrija and

its surroundings (Fig. 6). Weather conditions for that

particular day are shown on the figure. Hg concentra-

tions were relatively low (mostly below 25 ngm�3) on all

three maps, but Hg concentrations near the former

smelting complex completely dominate the map. Ele-

vated Hg levels were found along the Idrijca Valley

(25–50 ngm�3) and near Anthony’s mine entrance (up to

200 ngm�3) in the vicinity of a carboniferous shale

natural outcrop. A similar detailed mapping was

performed by Gosar et al. in 1994 (1997). Comparison

of the results obtained in 1994 and 2003 shows a similar

spatial distribution that strongly depends on the

geography of the valley, but much lower Hg concentra-

tions in air in 2003. The dependence of Hg in air upon

wind, temperature and moisture was also observed

(Gosar et al., 1997a, b). The Hg concentration in air in

Idrija and surroundings was mostly below 10 ngm�3.

Near the former smelting plant Hg concentrations

increased rapidly, even up to 3000 ng�m3. It seems that

the former smelting plant remains the main source of Hg

in air over the Idrija Valley. The spatial and vertical

distribution of Hg in the valley depends mostly on wind

and temperature conditions. Comparison of the results

with those obtained by Gosar et al. (2002) for Hg in soil

and attic dust in the upper Idrijca Valley shows very

similar values that mostly depend on the geography of

the valley.

3.3. Soil–air Hg flux

Factors important in controlling the temporal varia-

bility of Hg emissions on a daily basis include sunlight,

temperature, precipitation and atmospheric turbulence

(Lindberg et al., 1979; Klusman and Webster, 1981; Kim

et al., 1995; Gustin et al., 1997; Zhang and Lindberg,

1999; Poissant et al., 1999; Gustin et al., 2003; Gustin,

2003). Sunlight is the dominant factor controlling Hg

emissions (Coolbaugh et al., 2002; Gustin et al., 2003).

The addition of moisture to soils has also been

demonstrated to significantly increase emissions

(Lindberg et al., 1998; Engle et al., 2001; Kocman

et al., 2004). However the dominant factor controlling

the magnitude of flux is substrate Hg concentration,

which is most often dictated by the geological setting of

the area (Gustin, 2003).

Daily Hg evaporation trends measured at Baca pri

Modreju and in Idrija are shown in Figs. 7 and 8

together with average air concentration and air tem-

peratures. Topsoil at both locations contains quite high

levels of Hg (Table 1). The chemical and physical

characteristics of soil, data on Hg content and its

speciation for both locations were described elsewhere

(Table 1) (Gosar et al., 1997a, b; Gnamus et al., 2000;

Horvat et al., 2002; Kocman et al., 2004). At the site

Baca pri Modreju (46.142871N, 13.772051E) topsoil

contains about 76mgHgkg�1. Other samples from same

site show similar values (Gosar et al., 1997a, b; Horvat

et al., 2002). Hg exchange between soil and the atmo-

ARTICLE IN PRESS

Fig. 6. Air Hg concentration maps in Idrija and its surroundings (log scale).

Fig. 7. Hg evaporation from soil at Baca pri Modreju (in ngm�2 h�1).

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–75797576

sphere was measured on 7 September, 2004, a sunny,

late summer day with an average daytime temperature

of 25 and 11 1C during the night (daily average 16.3 1C)

with a weak E wind. The average Hg concentration

during the 24 h measurements was 5.5 ngm�3

(2.0–11.5 ngm3), with an average Hg flux from soil to

atmosphere of 34.0 ngm�2 h�1 (10.0–64.7 ngm�2 h�1).

The highest evaporation rate was observed during

evening and early night hours between 7 pm and 1 am,

when the air temperature fell and become closer to the

ARTICLE IN PRESS

Fig. 8. Hg evaporation from soil in Idrija (in ngm�2 h�1).

J. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–7579 7577

soil temperature (around 12 1C). Higher evaporation

rates during this period are also connected to the

moisture content in topsoil, which increased after sunset

due to the evening dew. These phenomena coincide with

measurements performed in wetlands of the St. Lavrence

River (Canada) (Poissant and Casimir, 1998; Poissant et

al., 2004) with similar characteristics to the site at Baca

pri Modreju (regular flooding, temperatures, solar

radiation, latitude, etc.), which shows that the Hg flux

in the studied area under dry conditions was strongly

correlated with soil temperature. They suggest that the

air–soil flux under dry conditions was more related to

thermodynamic processes such as enthalpy of volatiliza-

tion than to solar radiation and air temperature.

The weather conditions at the site in Idrija

(46.010461N, 14.029481E) were similar to those at Baca

pri Modreju, with a slight S wind that changed direction

near midnight from N to S. The average air temperature

was 15 1C (8–31 1C). In the past, the Hg concentration in

topsoil was heavily impacted by airborne Hg from the

former smelting plant (the distance from the smelting

plant is less than 200m, the former smeltery chimney is

200m above the site). The Hg concentration in topsoil

was 333mgHgkg�1 (Kocman et al., 2004). Other

authors reported similar values for the nearby area,

with the exception of the very close vicinity of the former

smelting plant (Gnamus et al., 2000; Gosar and Sajn,

2001; Gosar et al., 2002). The average Hg concentration

in air was 11 ngm�3 (2.4–33. 5 ngm�3) with an average

Hg flux from soil to the atmosphere of 84.4 ngm�2 h�1

(20.7–80.9 ngm�2 h�1) (Fig. 8). The highest flux values

were observed between 1 and 3 pm with a slight increase

during evening and early night hours. This coincides

with measurements at the Baca pri Modreju site. The

daytime peak can be related to solar radiation and

photo-reduction of HgS, Hg chloride-containing phases,

and Hg bound to Fe oxides and organic materials in soil

(Poissant and Casimir, 1998; Amyot et al., 2000;

Poissant et al., 2004; Gustin, 2003). Higher Hg evasion

during the night suggests that the air–soil Hg flux was

more related to the moisture content (evening dew) and

to the thermodynamic processes.

A comparison of these fluxes to those obtained by flux

chamber at the Hg mine of Mt. Amiata in Italy (Ferrara

et al., 1998) shows values of a similar order of

magnitude. Of course weather conditions, soil and air

temperature, air and soil Hg concentration and soil type

influence the measured results and can explain the

difference between the sites.

4. Conclusions

We can only guess the level of mercury concentrations

in air over the town of Idrija during the first four

centuries of operation of the world’s second largest Hg

mine. Nevertheless, there are some indications and old

records that allows speculations on Hg contamination in

the town of Idrija, such as the description of Theo-

phrastus von Hohenheim Paracelsus in 1572: ‘‘All who

live there are crippled and paralysed, partly asthmatic,

partly benumbed, without hope of ever being completely

healthy’’ or Walter Pope, an Oxford professor, who

wrote in 1663 about the ‘‘healing powers’’ of the waste

water: ‘‘The waste water is so saturated with mercury that

it heals itchiness and other similar discomforts’’ (cf. Car

and Dizdarevic, 2002).

ARTICLE IN PRESSJ. Kotnik et al. / Atmospheric Environment 39 (2005) 7570–75797578

In the last decade, after the final operation of the

smelting plant, concentrations of Hg in Idrija decreased

rapidly and reached levels from more than 1000 ngm�3

to values below 10 ngm�3. Seasonal variations in Hg

concentrations in air were observed during regular

monitoring. There are some locations around ventilation

shafts, natural outcrops and near the former smelting

plant where concentrations remain high. But it

seems that after more than 500 years of continuous

pollution by Hg, Idrija and its surroundings are slowly

recovering.

Acknowledgements

This research was financed by The Ministry of

Education, Science and Sport of the Republic of

Slovenia and by the European Union in the framework

of the EUROCAT project. The authors wish to thank

Dr. Antony R. Byrne for suggestions and linguistic

corrections.

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