The IMPACT OF  mercury MINING on the environment and ON human health In THE wider Idrija region, SLOVENIA,  and  IN the Gulf of Trieste

 

Milena Horvat1, Vesna Jereb1, Martina Logar1, Vesna Fajon1, Vesna Miklavčič2, Alfred Kobal2, Mark Hines3, Jadran Faganeli4

 

1Department of Environmental Sciences, Jozef Stefan Institute, 1001 Ljubljana, Slovenia

2Mercury Mine Idrija, Arkova 43, 5280 Idrija, Slovenia

3University of Alaska Anchorage, Department of Biological Sciences, 3211 Providence Dr. Anchorage, AK 99508, USA

4National Institute for Biology, Marine Biological Station, Fornače 41, 6330 Piran, Slovenia

milena.horvat@ijs.si

 

ABSTRACT

A short review of the  mercury research activities carried out in the former Hg mining area of Idrija, Slovenia is provided. These studies include an assessment of the distribution and uptake of Hg in animals and humans, bioindicators, and biogeochemical cycling of mercury in  river and coastal environments.

 

Figure 1. Study area and sampling sites
 
INTRODUCTION

The Idrija mercury mine in Slovenia is the site of the second largest Hg mine in the world, which was in operation continually for 500 years until about 20 years ago. Over five million metric tonnes of Hg ore was mined, and much of the residues were spread around the town and its vicinity. It has been estimated that 73% of the Hg mined was recovered, and  the remaining 17% dissipated into the environment (Miklavčič, 1996). One unfortunate outcome of the centuries of Hg mining activity has been the constant exposure of the inhabitants of the area to Hg poisoning, including high Hg levels in miners (Kobal et al 1999).

The Idrija mine has severely enhanced the mobilisation of Hg by mining activities, and Hg-laden material remains in the region Although the source of Hg in the Idrija region is from base deposits, the majority of the material that resides in surficial materials - including deep sediments  and along the banks of the river - are derived primarily from Hg re-mobilised downstream where the river system empties into the NE Adriatic Sea (Figure 1).

Some recent studies have shown that the area around the mine, continues to supply high quantities of Hg into the Idrijca and  Soča  river systems of the and that this Hg reaches the Gulf of Trieste some hundred km downstream (Širca et al., 2000). A number of studies were conducted in recent years, each addressing a separate environmental and health related Hg problem in the area. In order to develop realistic strategies for minimizing the  effects of the Idrija mining on human  health and the environment a more integrated approach is needed. In support to this objective the present  this paper will provide a short review of mercury research activities carried out in the region.

RESULTS AND DISCUSSION

Hg transport and transformation

The tailings and contaminated soils in the Idrija region are continuously eroded and serve as a continuous source for the river, the flood plains, and the Gulf of Trieste. This is confirmed by the fact that even after 10 years of closure of the Hg mine, Hg concentrations in river sediments and water are still very high and there are no signs of  the expected decrease of Hg in the Gulf of Trieste (Horvat et al. 1999, Covelli et al. 1999, 2000,  Širca et al. 2000).  Recent studies in the Idrijca – Soča - Gulf of Trieste region are mainly directed towards the quantification of Hg fluxes and better understanding of the fate of mercury, its accumulation in the flood plain,  and its final input to the marine environment. An assessment of the extent of contamination inb the Gulf of Trieste after the closure of the Hg mine was also made (Horvat et al. 2000, Hines et al. 2000).

 

Mercury and methylmercury were measured in various environmental compartments during the period 1995-97. Some recent measurements of mercury in water, sediments and soil are shown in Figure 2.  Total Hg in the Idrijca river water  increased by a factor of 4 downstream of the mine, with methyl Hg (MeHg) accounting for 1.5 % above the town of Idrija, 0.2 to 0.7 % after Idrija, 2-3% in river reservoirs and only about 0.2% in marine waters. This clearly shows the important role of reservoirs in MeHg dydnamics. Concentrations of Hg in sediments and flood plain soils also increased by several fold downstream, with MeHg ranging from 0.01 to 0.1% in riverine and marine sediments, and  less than 0.01% of MeHg in flood plain soil.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 2. Total and MeHg concentrations in water,  sediments and  soil, August 1999.

 

 

Hg methylation and MeHg demethylation seem to be active in all compartments of the study area and must therefore be studied together in order to properly assess the fate, mass balances and fluxes of Hg. The data obtained thus far  show that even 10 years after closure of the Hg mine, Hg concentrations in river sediments and water are still very high and did not show the expected decrease of Hg in the Gulf of Trieste (Horvat et al., 1999). Recent estimates on the Hg balance in the Gulf of Trieste have shown that the annual input through the Soča River discharge is about one ton and a half (Širca et al.1999). The major source of inorganic mercury is still the Soča River, while the major source of methylmercury is the bottom sediment of the Gulf, which enters bottoms waters and presumably the marine food chain (Širca et al. 1996-2000, Hines et al, 2000, Horvat et al. 2000, Covelli et al. 1999). As a consequence Hg in fish frequently exceed the value of 0.5 mg/kg, which is set as the maximum permissible level in a number of countries (Horvat et al 1999). In addition, a mathematicall modell of mercury transport and cycling in theGulf of Trieste was also  developed in order to simulate future scenarios (Žagar et al, 2000)

 

Air

Mercury concentrations in air in the town of Idrija are still very high. They vary from 0.01 to about 0.490 µg.m-3 and did not show a significant drop during the last ten years, however they are much lower than during the active period of the mining (0.1 to 10 µg.g-1). The air concentration depends up-on the weather conditions, direction of winds, and sampling locations. There are two major sources: one is close to former smelter  and the other is close to the ventilation shaft from the mercury mine.  Biomonitoring of Hg air contamination using epyphitic lychens was developed and is succesfully used to estimate average air mercury concentrations in the study area (Lupšina et al. 1993, Horvat et al. 2000).

 

Terrestrial ecosystem

Mercury distribution and uptake by plants, including mushrooms, and various organisms of the contaminated Idrija region and control areas in Slovenia has been the subject of various studies (, Horvat et al. 2000, Byrne et al. 1970, 1995). The results confirmed the effective  transfer of Hg from soil (and air) to vegetation, herbivores and carnivores further up the food web.  Interestingly, a higher accumulation of MeHg was observed in those environments polluted with high concentrations of inorganic mercury compared to less contaminated and control areas (Gnamuš et al., 1999, 2000).

 

Drinking water and food

Mercury concentrations in drinking water (surface and groundwater) are below 0.1 µg.l-1 and are even lower away from Idrija region (Miklavčič, 1996, Doctor et al. 2000). These values are far below the permissable level of 1 µg.l-1. This also indicates that total intake of Hg by humans  through water consumption  is low. The mercury concentration in foodstuffs in the Idrija region varies considerably depending on  location and  type  (Kosta et al. 1974, Stegnar et al. 1973, Miklavčič, 1999).  However, Hg is elevated in almost all food products including meat. The highest concentration were found in fish caught in the Idrijca and Soča rivers and vary from 1.07 to 1.87 mg/kg, f.w., where the percentage of MeHg in fish increases with distance from the town of Idrija (Miklavčič, 1996).

 

Health related studies

There are two major exposure pathways for the local population. One is the exposure to atmospheric Hg in Idrija and nearby  surroundings and the other is exposure through food consumption, including fish in the coastal area of the Gulf of Trieste. Today the highest values of Hg in air are  still close to the US EPA reference concentrations for chronic inhalation exposure of 0.4 µg.m-3. This indicates that some inhabitants in is more exposed areas of the town of Idrija  are potentially at risk due to exposure to elemental mercury through inhalation. Exposure to inorganic Hg through food consumption other than fish is not considered to pose significant problems. On the contrary, the coastal population shows increased values of Hg in hair (Ingrao et al., 1993) as an indication of exposure to MeHg due to fish consumption. Further comprehensive studies conducted in the region will provide more information about possible health effects.

 

ACKNOWLEDGEMENT: The Ministry of Science and Technology of Slovenia is kindly acknowledged to support Hg research studies presented in this presentation.

 

REFERENCES

Byrne AR, Kosta L (1970) Vestn. Slov. Kem. Druš. 17: 5-11.

Byrne AR, Skreblin M, Falnoga I, Al-Sabti K, Horvat M, (1995) Acta Chim. Slov. 42/2, 175-198

Covelli S, Faganelli F, Horvat M,  Brambati A (1999) Estuar. Coast. Shelf Sci., 48(4): 415-428.

Falnoga I, Kregar I, Stegnar P, Tušek-Žnidarič M (1997) in Proc. of the Ninth Int. Symp. on Trace Elements in Man and Animals- TEMA-9,  NRC Press, Ottava, Canada, pp. 489-490.

Gnamuš A, Horvat M (1999) In Mercury Contaminated Sites : Characterization, Risk Assessment and Remediation, (Environmental Science). Berlin: Springer, 1999,pp. 281-320.

Doctor DH, Lojen S, Horvat M (2000) Acta Carsicol. 29/1, 79-92.

Hines ME, Horvat M, Faganeli J,  Bonzongo JCJ, Barkay T, Major EB, Scott KJ, Bailey EA, Warwick JJ, and Lyons WB (2000) Env. Res. 2000, in pres.

Horvat M, Covelli S, Faganeli J, Logar M, Mandić V, Rajar R, Širca A, Žagar D (1999) Sci. Total Environ., 237/238: 43-56.

Horvat M, Falnoga I, Byrne AR (1999) Proc. NIMD Forum ’99, October, 1999, Minamata, Japan, pp.94-115.

Horvat M, Jeran Z, Špirić, Z, Jaćimović R, Miklavčič V (2000) J. Environ. Monitor. 2, 139-144.

Ingrao G, Belloni P, Santorini GP (1993) Convegno Il Mercurio Neelle Lagune di Grado e Marano, Aspeti Igienico-Sanitari, 1993, Udine, pp-68-75.

Kobal A, Nanut E, Horvat M, Stegnar P, Sabadin A (1999) In Mercury Contaminated Sites: Characterization, Risk Assessment and Remediation, (Environmental Science). Berlin, Springer, 1999, pp. 271-279.

Kosta L, Byrne AR, Zelenko V, Stegnar P, Dermelj M, Ravnik V (1974) Vestn. Slov. Kem. Drus., 21: 49-76.

Lupšina V, Horvat M, Jeran Z, Stegnar P (1992) Analyst, 117: 673‑675.

Miklavčič V (1996) Idrija as a natural and anthropogenic laboratory: mercury as a major pollutant Proc. of the meeting of researchers, Idrija, Slovenia  ISDN 961-90141-1-1.

Stegnar P, Kosta L, Byrne AR, Ravnik V (1973, Chemosphere, 2, 57-63.

Širca A, Horvat M, Rajar R, Covelli S, Žagar D, Faganelli J (1999) Acta Adriat. 40/2, 75-85.

Žagar D, Rajar R, Horvat M, Širca A, Covelli S (2000) Sci. Tot. Environ., in press.