The Kavčnik homestead (Zavodnje, Slovenia) is a rear example of an old Slovene rural architecture where a tradition of herbalism is maintained. Pollution of the soil and vegetation there is increased because of the Šoštanj Thermal Power Plant impact and intensification of agricultural practices.

Cultivation of medicinal plants Achillea millefolium, Alchemilla xanthochlora, Althea officinalis, Calendula officinalis, Hypericum perforatum, Plantago lanceolata, Ruta graveolens, Thymus serpyllum, Valeriana officinalis and Arnica montana on small plots has been performed there for five years. Analyses of heavy metal contents in the plant and soil materials by atomic absorption spectrometry and essential oil contents analyses by hydrodistillation were done. The results were compared to legislative values valid in Slovenia and recommended values in EU.

The yield and the content of essential oils as quality indicators were good for all cultivated plants. Contents of Cd were increased in more than a half of plants, especially in Hypericum perforatum and Althea officinalis (ł 0.5 mg/kg). Preliminary results reveal that Valeriana officinalis and Ruta graveolens could be recommended for cultivation in this area.

Zavodnje village is situated in an area affected by the Šoštanj Thermal Power Plant (TPP) where also aerosols are emitted. In our research soil pollution and accumulation of trace elements in medicinal plants were investigated near the Kavčnik homestead. The Kavčnik smokehouse is a pearl of Slovene rustic architecture. It is nowadays known as the southernmost example of smokehouse in the European Alpine area. The research project, in which the traditional herbs are cultivated, started in the beginning of the year 1995. At the same time some opportunities for nearest farmers for medicinal plants field production were studied. Simultaneous monitoring of soil and vegetation was performed before and after the desulfurisation device in TPP Šoštanj was installed.

The herb of Achillea millefolium, Alchemilla xanthochlora, Althea officinalis, Calendula officinalis, Hypericum perforatum, Plantago lanceolata, Ruta graveolens, Thymus serpyllum, Valeriana officinalis and Arnica montana was cultivated on small plots. The herbs were collected in the optimal picking period and dried on 36°C. Plant samples were homogenized with Büchi B-400 equipped with ceramic knife and passed trough 1 mm plastic sieve. A CEM MSP 1000 microwave digestion system was used for acid digestion. The heavy metal content was determined using a Perkin Elmer SIMAA 6000 atomic absorption spectrometer. The electro-thermal technique was used for the determination of lead and cadmium, the cold vapour AAS technique was used for Hg determination, while hidride generation AAS technique was used for As determination. Standard reference material was used for analytical quality assurance. Analyses of the essential oil content were done by steam distillation according to Ö.A.B.9. Results were compared to Slovene regulations (Off. Gaz. SFRJ 59/83) and Recommendation on Heavy Metals in Herbal Drugs issued by the German Federal Ministry of Health (Kabelitz 1998).

Many heavy metals are natural components of the earth surface and are taken up by plants from the air, water and soil (Bergmann 1992). They can be harmful to man, animals and plants, since they become concentrated in the tissue and are only eliminated very slowly. Especially As, Hg, Cd and Pb could be deleterious to the human health.

The uptake of heavy metals and their compounds from soils depends on their concentrations and solubility in soils and on soils properties (Kabata-Pendias/Pendias 1984). Our research proved that concentrations of heavy metals in the soil were under allowed maximum levels. Also the pH, the content of organic matter and content of clay in the soil could not suggest that plants accumulate heavy metals from the soil (Table 1).

The heavy metals uptake through the leaf surface can derive in elevated amounts of heavy metals accumulated in the plant. It depends on the plant species, its nutritional status, the thickness of its cuticle and the age of leaf (Alloway 1990). Results of our research revealed that the content of Pb in almost all herbs was below the officially determined level 3 mg/kg (Graph 1), while the contents of As and Hg in all herbs were below the determined level defined as 1 mg/kg and 0,1 mg/kg, respectively (Off. Gazz. SFRJ 59/83).

Increased amounts of Cd in herbs tissues indicated that herbs, especially Hypericum perforatum, Althea officinalis, Thymus serpyllum, Taraxacum officinalis are polluted. There were no big differences between the amounts of Cd during last five growing seasons (Graph 2).

Graph 1. Content of Pb in herbs in the period 1995 - 1999.


Graph 2. Content of Cd in herbs in the period 1995 - 1999.

The yield and the content of the essental oil depend on the soil properties, root systems in the soil, climate and fertilization. The results confirm that in most plants yield and essential oil content were in accordance with pharmacopoeia or commercial demand (Graph 3).

Graph 3. Content of essential oils in herbs in the period 1995-1999.


CONCLUSION

Contents of cadmium were increased in more than a half of plants. Especially high amounts were found in Hypericum perforatum and Althea officinalis in which maximum recommended level (0.5 mg/kg), defined by the German Federal Ministry of Health, were exceeded. While the soil was not polluted with heavy metals, the main sources of Cd in plants were probably inputs through airborne emissions in this area. Considering the results of the yield, quality tests and those of potential heavy metal pollution Valeriana officinalis and Ruta graveolens could be recommended for cultivation in impact area of the Šoštanj Thermal Power Plant. These preliminary results should be tested on bigger cultivation plots.

The research was financially supported by the Šoštanj Thermal Power Plant and Cultural Centre "Ivan Napotnik" Velenje, the owner of Kavčnik homestead. We thank Boštjan Pokorny, who helped us with the translation.

1. Alloway B.J. (1990): Heavy Metals in Soils, Blackie, John Wiley & Sons, Inc. London and Glasgow, New York.

2. Bergmann W. (1992): Nutritional Disorders of Plants, Gustav Fisher Verlag, Jena-Stuttgart-New York.

3. Kabelitz L. (1998): Zur Schwermetallbelastung von Arznei - und Kräuterdrogen, Pharm. Ind. 60, 444-451.

4. Kabata-Pendias A. and Pendias H. (1984): Trace elements in Soils and Plants, CRC Press, Inc. Boca Raton, Florida.

5. Official Gazzete RS 68/96: Degree of input of dangerous substances and plant nutrients into the soil, 1996, 5769-5773.

6. Official Gazette SFRJ 59/83: Ordinance of maximum allowed value of pesticides, another toxic substances, hormones, antibiotics and micotoxines in food stuff, 1983, 1635-1651.