Management of Contaminated Sites and Land in Central and Eastern Europe

Poland

Country Characterisation

In Poland, contaminated land is not related only to industrial activity but is also the legacy of the former communist regime. The former regime supported inefficient technologies as well as inefficient production systems consuming energy and natural resources. The priority of industrial production over human needs and environmental requirements resulted in uncontrolled emissions and environmental pollution. The collapse of the communist system and the transition of the economy revealed a critical need for technology innovation as well as environmental clean-up programmes. The legacy of the past left a great number of contaminated sites encompassing large areas. Many of these contaminated sites are former military bases.

Up to the year 1993 the Soviet army occupied 59 sites, covering an area of approximately 70000 hectares. Most sites are situated in the North and in the Northwest of the country. The systematic assessment of former Soviet military sites started in 1991 and major work was carried out between 1992 and 1993. In May 1992, an agreement concerning the withdrawal of the Soviet forces was signed. After this date, sites were assessed by committees with both Polish and Russian representatives. The resulting protocols concerning the state of the environment were later used as official documents when the sites were handed over to the Polish authorities. The major goals of this project were to identify contaminated areas, the need for clean-up, and the potential clean-up costs. With respect to the Polish National Army sites investigations have been limited to a few sites, being fuel and chemical storage facilities and air bases.

Land contamination is regarded in Poland as the presence in the environment of a substance or other agent, which might cause harm, or as one of the land degradation forms e.g. erosion, changes in geology and hydrology, and depletion of soil resources [5]. Land contamination per se does not always pose a threat to the environment, and the importance of the contamination can only be determined following detailed investigation and site specific evaluation of risks.

The present Polish legal system does not offer any binding regulations neither for risk assessment nor for land recovery procedures or standards. The Act on Environmental Protection and Management from January 1980 classifies areas with chemically degraded soils as lands subject to special protection. The category embraces areas degraded due to industrial, agricultural or any other activities. The protection of degraded areas involves, in particular, counteracting negative impacts of polluting objects and pollutants, and restoration of ecological and productive values of the land.

The Mining and Geological Law from February 1994 states that restoration of damaged agricultural or forest land shall proceed in conformity with the Law on the Protection of Agricultural and Forest Land (as of February 1995). The latter contains only very general provisions concerning reclamation of degraded land.

This gap in legal system has been partially filled in by the Guidelines for classifying contaminated land and risk assessment in grounds and groundwater contaminated by petroleum derivatives and other chemical substances, issued by the State Inspectorate for Environmental Protection in 1995 [6].

Other important legal documents relevant for the management of contaminated sites are:

	The Water Act of 1974, which regulates the use of water resources and also water protection.
	The Act on Regional Development of 1995, which regulates specific land uses.

It is noted that waste management was regulated by a separate Waste Act adopted in June 1997. Major elements of the Polish law on waste management are:

	Permits for waste generators.
	Permits for hazardous waste recipients.
	Waste classification (including hazardous waste).
	Waste (quantity and quality) records.
	Action hierarchy: waste prevention and minimisation, utilisation (recycling), disposal.
	Regulations for responsibilities of landfill managers.
	Ban on hazardous waste import.

The environmental policy and consequently the environmental acts are broadly based on the use of environmental impact assessment (EIA) as method for assessing new investments, which are regarded as harmful or potentially harmful of the environment. Public consultations are also required in the permitting process for building of installations.

The Polish standards for environmental protection are based on fixed regulatory limits. However, the regulations do not include threshold (permissible) values for soil contamination i.e. there are no specific generic values or regulations establishing admissible contaminant concentrations in soil nor any binding classifications of contaminated land.

Soil is regulated with respect to regulations concerning "raw sewage sludge for agricultural purposes" given in a decree on agricultural use of sludge and manure mixture issued by the Ministry of Environmental Protection, Natural Resources and Forestry (decree of 1986).

Suggested standard values (or advisory standards) have been published by soil specialists in a bulletin sponsored by the State Inspectorate for Environmental Protection. At present, there are no official criteria for classifying contaminated sites, and therefore there is no impetus for corrective action.

The above-mentioned guidelines for risk assessment for soil and groundwater contaminated by petroleum derivatives and other chemical substances have a status of advisory reference standards. The guidelines are based on other European regulations including the Dutch list of standards updated in 1993, the Berlin list and the 80/68/EEC Directive of 1979 concerning the protection of groundwater. The guidelines provide a useful tool for unification of procedures for land remediation on a countrywide scale.

A decree on drinking water criteria was amended in 1994. The defined values from the decree are used as reference values for ground water quality criteria. Furthermore, groundwater quality criteria are defined within the groundwater monitoring of the State Inspectorate for Environmental Protection.

Though the Ministry of Environmental Protection, Natural Resources and Forestry, has identified a list of the 80 "worst" polluters in Poland, there is no sufficient level of enforcement for environmental audits. In some cases, contaminated sites posing extremely high risk to human health and the environment have started to be regarded as policy priorities (e.g. the Tarnowskie Góry site, a former chemical plant).

An important barrier for the implementation of clean-up strategies is the lack of regulation of the state liability for environmental damages / old pollution caused by the state owned enterprises. This makes the implementation of the "polluter pays principle" rather doubtful.

Risk assessment has not been incorporated into Polish regulations. However, full-scale risk assessments have been performed for two clean-up demonstration projects performed by US department of Energy (DoE) at the Czechowice refinery and by US DoE / Us EPA at a phytoremediation project in Piekary. Both projects were made in co-operation with the Institute for Ecology of Industrial Areas in Katowice [7].

Management of contaminated sites and land is the responsibility of:

	The State Inspectorate for Environmental Protection. The State Inspectorate for Environmental Protection carries out the control of environmental quality criteria.
	The 16 Polish provinces (voivodships). Most environmental issues are under the responsibility of the provinces (voivodships). They are also the responsible authorities for the abandoned Soviet military sites.
	An Inter-Ministry Working Group for remedial measures at former Soviet military sites. The group supervises investigations and remediation at former Soviet military sites.

It is noted that no national clean-up strategies or programmes for contaminated sites and land have been implemented. The only exception is a program outlined for the former military bases.

Some regional action plans have considered the issue; e.g. clean-up of contaminated land is stressed in the 2020 action plan for Katowice voivodship and hazardous waste management plan elaborated under the PHARE program.

Registration

As no appropriate legislation exists, there is no basis for performance of a national survey of contaminated land.

The State Inspectorate for Environmental Protection has made a preliminary identification of contaminated sites on former military bases transferred into civil use.

In 1995, the US Department of Energy (DoE) sponsored a survey of the Polish market for contaminated site characterisation and here listed several dozens of contaminated sites in need for characterisation.

Data on industrial waste producers, amount of waste generated, re-use, dumping places, and applicable technologies are collected by the Waste Management Institute in Katowice.

According to the Polish Central Statistical Office, in 1997, the amounts of industrial wastes were the following:

	Produced:124,469,500 tonne
	Utilised:80,126,100 tonne
	Neutralised:299,600 tonne
	Deposited:44,043,800 tonne

The total industrial waste landfill area was 11,172 ha.

The major regions of waste generation and dumping are Katowice, Legnica, Walbrzych, Szczecin, Tarnobrzeg and Krakow. In 1997, there were 956 municipal waste landfills (area: 3,141 ha) and about 350 so-called pesticides tombs.

Characterisation of Soil and Groundwater Contamination

Sources of Soil and Groundwater Contamination

The present state of the soil contamination is mainly caused by negative impact of past economic activity – mostly industrial activity, transportation, and public utilities. Currently, since appropriate changes in production technology and protective facilities have been applied, emission of industrial and traffic pollution (affected state of soil contamination) has radically improved. Finally, impact of various waste disposal sites on soil and water environment remains the most serious problem in the field of land protection. The issue of waste management arrangement is a priority in Poland.

Generally, most significant recognised environmental hazards related to soil contamination arise from the presence of chemical substances, but other hazards such as flammable gases, combustible and radioactive materials, and pathogenic organisms may locally be very important e.g. on former military sites. Best-recognised problems under the conditions prevailing in Poland are the presence in soil of chemical substances such as heavy metals, sulphur, oil products and pesticides [8-10].

Agricultural use is, to a large extend, responsible for land quality. Loss of organic substances and acidification are two of main problems. Acidification is regarded as a major factor responsible for chemical degradation of soils in Poland enhancing the solubility of mineral and organic soil constituents. It has been estimated that use of NPK fertilisers combined with acid deposition from man-made sources has resulted in the acidification of sandy soils, which are the dominating soil types in Poland.

In some regions, heavy metal soil contamination poses a local problem. Soil contamination by heavy metals implies that the concentration of these elements is higher than it would occur naturally. According to a study performed in industrialised and clean regions of Poland, increased soil levels of cadmium, lead, copper and zinc can be found primarily in the Katowice and Cracow regions and in the Legnica-Glogow copper mining and smelting region. Other contaminated areas are encountered in most of the larger towns such as Warsaw, Lodz, Rzeszow, Opole, Wroclaw, Walbrzych and Lublin. Contamination by heavy metals in agricultural topsoil (0-20 cm) has been thoroughly investigated during a recent countrywide agrochemical soil study performed in 1991-95. The results of the study indicate that more than 80% of the soil has natural contents of heavy metals and should be classified as non-contaminated. About 17% of the agricultural soil have slightly elevated levels of Cd, Cu, Ni, Pb and Zn. Only about 2,6% of the soils were classified into higher contamination classes. The highest average contents of heavy metals in agricultural soils were found only in close vicinity of metalliferous ore smelters.

In total, 21 abandoned Soviet military sites have been subject to the first investigations performed at military sites in Poland. The results of the detailed investigations revealed soil contamination at approximately 1% of the investigated areas and groundwater contamination corresponding to approximately 10% of the investigated areas:

	Soil contamination deriving from mineral oil products was identified at all 21 sites. Uncontrolled waste disposal of hazardous wastes was detected at 19 sites. Furthermore, in many cases soil contamination with heavy metals and contamination due to phenols, PAH and chlorinated hydrocarbons were detected.
	Groundwater and surface water contamination was detected in 20 cases, mainly due to hydrocarbons and heavy metals.
	Vegetation damage was detected especially at the test ranges. The total vegetation damage of the soil surface was assessed with 25%.

Number of Registered Contaminated Sites / Contaminated Land Areas

According to data provided by the Polish Central Statistical Office (GUS) [3], areas taken by settlements and communication lines occupy now less than 5% of the country surface while wastelands and other uses take together some 3.3%. The majority of these areas is regarded as heavily and/or moderately degraded. According to recent estimation, their total surface amounts to about 850,000 ha. These include waste dumping sites, landfills, and industrially degraded or derelict grounds where reclamation is urgently needed [11]. According to recent assessments made by the State Inspectorate for Environmental Protection (PIOS), chemically contaminated lands constitute together about 2.7% of the total surface [12].

A detailed inventory on the state of soil contamination in industrial plants and municipal plants is currently carried out mainly for privatisation purposes.

Regarding the former Soviet military sites, the sites were assigned to priority groups according to the results of the pre-assessment and the first investigation of the sites.

Identification of Potentially Contaminated Sites and Areas

It is estimated that the area of land devastated and degraded by mining industry (and raw materials extraction) is about 49,000 ha, by power industry about 1,000 ha, and by metals production industry 256 ha.

Territorial chemical-agricultural stations and institutes of agricultural and environmental protection have carried out investigations of agricultural soil contamination for many years in Poland.

Currently, in the framework of the State Environmental Monitoring, monitoring of soil contamination by heavy metals is carried out in stationary control points on the whole area of the country. Comprehensive analytic materials in this field, which enabled elaboration of maps showing the contaminated areas, are prepared.

Regarding the abandoned Soviet military sites, all the 59 sites were pre-assessed between 1991 and 1993. Of these, 35 sites were classified as potentially contaminated. Of the 35 sites, 21 sites were selected for further investigations. The selected 21 sites cover an area of approximately 60000 hectare, which corresponds to 86% of the total area of all the former Soviet military sites. The selected sites included the following:

	All airbases with major fuel stocks.
	All major fuel stocks.
	All test ranges.
	All ammunition stocks.
	All marine harbours.
	Selected garrisons.

Investigation of Contaminated Sites and Areas

Investigation methods of soil contamination used in Poland deal with determination of total content of the pollutants regardless of their existence in the form available for plants (by roots) – thus in form, which determines their contamination state, or their existence in other forms.

Guidelines for risk assessment for soil and groundwater contaminated by petroleum derivatives and other chemical substances exists.

Site assessments and investigations are carried out according to the guidance document [6], which defines three major steps:

The pre-assessment of sites has the objective to identify actually contaminated spots or areas, and includes the following activities:

	The collection of relevant information concerning land use, geology and hydrogeology, and general environment conditions of a site.
	An on-site visit.
	The evaluation of aerial photos (usually scale 1:10 000)

The first investigation includes limited sampling at the identified contaminated areas and spots:

	Limited number of soil, groundwater, surface water and wastewater sampling.
	Systematic screening for subsoil storage tanks.
	Geophysical analysis with screening for metal objects in the subsoil.

The detailed investigation is carried out to further specify the need for remedial measures. This step includes:

	Additional sampling for specific investigation.
	Detailed hydro-geological investigations.
	Modelling of potential contamination migration pathways.
	Risk assessment.

For the assessment of risks Poland partly applied and tested the methodology of the US EPA on hazard ranking called HRS Hazard Ranking System. For the assessment of risks at sites contaminated with mineral oil products, the State Inspectorate for Environmental Protection recommends the methodology elaborated by the American Kerosene Institute, the "Exposure and Risk Assessment Decision Support System, DSS".

At the former Soviet military sites, the technical investigations usually included the following activities:

	Drillings and sampling at the identified most likely contaminated areas.
	Physical and chemical analysis of the collected samples.
	Soil gas analysis.
	Groundwater monitoring.
	Measurements for radioactivity.

Handling and Treatment of Excavated Contaminated Soil

Chemical contamination of land within the immediate impact of chemical industry and in urbanised areas has been identified and inventoried. There are numerous cases where appropriate remediation technologies and programmes were developed but not implemented due to lacking legal and structural regulation [11].

Treatment methods for contaminated soil in Poland depend on the kind and state of contamination, occurrence depth of the contamination, geological conditions, and predicted economic use method of the soil, and other economic and technical factors.

Contaminated soil is excavated in order to treatment or disposal in (protected) landfill sites exclusively in particularly reasonable cases.

Various Polish and foreign companies carry out soil treatment (including treatment of oil contamination). The most frequently applied remediation technologies include washing pollutants away from the soil and biological treatment in-situ. In some particularly difficult cases, other, more complicated chemical and physical-chemical technologies are applied with use of various stationary and mobile facilities.

Measures Used by Remediation of Soil and Groundwater Contamination

Most clean-up technologies on the Polish market are offered by western companies (joint ventures and representatives) or Polish companies acting on licence or contractual basis. The market for services is not yet developed. This is due to the lack of a legal framework, e.g. defining risk assessment, and the lack of demands in respect to the problem holders. The real market competition has only occurred for the remediation of former military bases. The majority of the remediation projects performed in Poland have focused on the remediation of oil spills.

One of the remediation technologies successfully applied on a technical scale in Poland is remediation of heavy metal contaminated soils by use of zeolite. Zeolite has been added to the soil on selected contaminated agricultural sites within the industrial regions of Katowice and Cracow and in the vicinity of the Glogow copper mining and smelting region. The minerals have been applied as granulates enabling the later removal of these again with adsorbed heavy metals. Efficiency of the soil clean-up was assessed after one and two year intervals and was shown to be dependent on the actual soil type. On average levels, the soil contents of Cd, Pb, Zn, Cu and Hg dropped by 17-18% relative to initial levels within one year, and decrease in heavy metals content reached 40% for some soil types the second year after the zeolite application. Other tests with zeolite application for cleaning heavily metal contaminated soil have also been performed [13, 14].

Remediation of sites contaminated by petroleum, petroleum derivatives and other organic compounds is still in a preliminary stage in Poland. However, technologies have been developed and applied on a technical scale for decontamination of soil and groundwater. E.g. in one case, the soil and groundwater contamination was assessed, hazards identified and remediation performed at a 50 ha site owned by the Polish railways in Wroclaw and used for oil storage. Methods for remediation included in-situ ventilation and bioventing of contaminated soil and aeration of groundwater as well as ex-situ treatment of excavated soil by biodegradation. By the remediation, the contents of hydrocarbons in soil and groundwater were reduced to levels below the advisory standards recommended by the State Inspectorate for Environmental Protection [15].

Another case of successful bioremediation of an oil contaminated ground within the Kielce Railway Station was reported by the Warsaw University of Technology jointly with the Exbud-22 Hydrogeotechnika Enterprise from Kielce. Microorganisms were applied in-situ and the clean-up effect was almost 100% reduction of oil derivatives in two months following the onset of the trial [16].

Similar problems of land decontamination are to be tackled among others in a part of sites occupied by the former Soviet army. Major hazards in those areas are linked to oil spills, illegal waste dumping and storage of toxic chemicals. It was estimated that ground contamination by petroleum and hazardous toxic chemicals is to be found on more than 500 ha. The most urgent recovery activities include removal of oils and toxic chemicals and skimming of free phase oil floating on the groundwater. A few remedial measures have been implemented at the former Soviet military sites. All measures were dedicated to avert the risks of the most urgent cases. The measures applied were usually:

	Removal of free oil phase from polluted groundwater and re-infiltration of the treated groundwater into the soil.
	Extraction of soil gas and treatment of contaminants in the extracted soil gas by filtration or incineration.

Apart from petroleum products and toxic chemical contamination, sulphur mining and processing is another source of environmental hazards and a hot spot on the land recovery map of Poland. According to recent reports, about 500 ha of grounds heavily contaminated by sulphur in the Tarnobrzeg Sulphur Mining Region have been recovered using postflotation lime and sewage sludge for soil remediation [5].

The review of methods and underlying practical and theoretical knowledge concerning biodegradation of various hydrocarbons in soils and wastes in Poland shows that there is already some domestic expertise in this field [17].

Investigation and Remediation Activities

The major financial resources for investigation and remediation activities are resources of the landowners as well as soft loans and grants from local, regional and national environmental funds (created from fees and fines). Generating funds for clean-up within the privatisation process is still unclear.

Contaminated land management is also a priority of the EcoFund created as a debt to grant swap money. The fund is dedicated to environmental measures and also the measures at heavily contaminated sites where polluters can not be held liable.

At the former Soviet military sites, the application of the polluter pays principle is hardly possible. The government finances the most urgent clean-up measures at the most contaminated sites. In the case of privatisation, the new owner has to accept the environmental liability.

In 1995, the Polish Council of Ministers approved the national clean-up programme for the abandoned Soviet military sites, which defined:

	To fund the most urgent cases with resources from the National Environment Fund.
	To oblige new owners to take care of the appropriate clean-up measures.

Legal Requirements re. Polluters and Site Owners

In the case of privatisation the new owners are in general held liable for site investigations and clean-up measures. In some cases, the new owner can be exempted from the clean-up liability. This is the case if the contamination was not evident at the time of the property transfer.

Scope of the Problem

Scale of the Problem and Handling Costs

Concerning the acidification of soils, it has been estimated that about 60% of the agricultural soils in Poland have pH in the range of 4.5-5.5 while the remaining 40% have pH above 5.6. Acidification is observed especially in the South-western and the central parts of Poland. Acidification of topsoil is regarded as the most widespread form of degradation of soil properties in Poland, and the extent is growing due to increasing N- and S-acid precipitation. As a basic remediation practise for counteracting the acidification of arable soils, liming have been widely used.

According to recent assessments, chemically contaminated land constitutes all in all about 2,7% (8,400 km²) of the total land area of Poland. Other areas subject to various degradation factors and areas potentially subject to degradation including motorway side zones and other diffusely contaminated areas are all in all estimated at about 17% (53,000 km²) of the total land area of Poland.

In December 1992, the first cost calculations were carried out for the remediation of the abandoned Soviet military sites. The calculations included the definition of standard clean-up costs according to the type of contamination and the type of technology applied. Ad-hoc measures to avert the highest risks at the abandoned Soviet military sites were calculated to amount to 104 million USD. The restoration of the environmental damage at all bases was calculated to amount to 2.4 billion USD.

Priority in Relation to Other Societal Problems

Results of the investigations enabled undertaking the most urgent activities aimed at prevention of impact of the soil-water environment contamination on life conditions and human health. In particularly contaminated industrialised area (Upper Silesia), a common pure water supply system (from distant not-contaminated water intakes) has been organised, and organisational activities aimed at elimination of food and fodder made of plants particularly susceptible on heavy metals accumulation have been undertaken. Environmental protection issues are significant during preparation of spatial management plans and, as a consequence, during siting of health protection objects, educational objects, recreational objects, residential building objects, etc.

Illustrative Cases

The Czechowice Oil Refinery is situated in the southern part of the Katowice Province about 45 km from the city of Katowice. The refinery is located in a small town, where land uses include residential, recreational, agricultural, and industrial areas. The refinery has been in operation for about 100 years. Catalytic cracking processes are used to refine crude oil, and waste from acid refinery processes has been disposed off in lagoons. The waste product is a viscous semi-liquid hydrocarbon mixture, which is not completely characterised.

The Czechowice Oil Refinery was selected as a demonstration site for a risk assessment project conducted by the Institute for Ecology of Industrial Areas in Katowice in co-operation with US Department of Energy (DOE) and others. The risk assessment process used for remediation purposes includes site characterisation, selection of chemical indicators, toxicity assessments, site-specific human exposure assessments, risk characterisation, and development of remedial goals. A general flow-chart representing this is shown below.

Look here!

The first step – site characterisation – has been completed. During the site characterisation, historical information and data on geology, hydrology, ecology, and local land use were collected. Mainly, the characterisation focused on soil and groundwater affected by refinery activities in the vicinity of the waste lagoons. Resulting from this, the extent of contaminants was determined.

The second step is the selection of chemical indicators, which are representative of the toxicity and environmental behaviour of the contaminants at the site. For the Czechowice Oil Refinery site, the BTEX, 6 PAH, and 9 heavy metals were selected as chemical indicators. For these chemicals, information on environmental occurrence, physical/chemical properties, and fate and transport in the environment were gathered.

By the next step – toxicity assessments – toxicological characteristics on each of the chemicals of concern were identified.

An important step of the risk assessment process is the exposure assessments. For the Czechowice Oil Refinery site, the exposure assessments have included determination of exposure scenarios, determination of factors associated with each scenario and collection of data to support each factor.

The next step is the risk characterisation, which combines the toxicity assessments with the exposure assessments in order to quantify the risks posed by a contaminated site under a given set of conditions. The risk characterisation is considered separately for carcinogenic and non-carcinogenic effects and includes the accompanying uncertainties.

If action is deemed needed as a result of the risk characterisation, site specific remedial goals (i.e. target concentration limits, TCLs) will be developed for selected environmental media. The remedial goals combined with results of feasibility studies will help to select the specific remedial technologies to be implemented at the site.

References

1. UN/ECE Statistical Division (1998). Trends in Europe and North America. 1998 Statistical Yearbook of the UN/ECE. At http://www.unece.org/stats/trend/trend_h.htm. Based on figures from 1994 – 1997.
2. Information provided by Barbara Gworek at the Institute of Environmental Protection, Poland. July 7, 1999.
3. Polish Central Statistical Office, Environment, Warsaw (1998). In Polish.
4. POPIN (Population Information Network) (1999). The Demography of Countries with Economies in Transition. At gopher://gopher.undp.org/00/ungophers/popin/wdtrends.
5. Sienkiewicz, J., B. Gworek (1999). Land Contamination and Recovery Problems in Poland. Ochrona Srodowiska i Zasobow Naturalnych, 16, 59-69. In English.
6. State Inspectorate for Environmental Protection (1995). Guidelines for the assessment of chemical and groundwater contaminated by petroleum derivatives and other chemical substances. State Inspectorate for Environmental Protection, Warsaw. In Polish.
7. Wcislo, E., J.M. Cuperberg & C.M. Teaf (1996). The Role of Risk Assessment in Remediation of an Oil Refinery Site in Poland. Paper presented at the Seminar on Guiding Principles for the Assessment of Soil Contamination held in Katowice, 1996.
8. Ad Hoc International Working Group on Contaminated Land (1998). Ad Hoc CEE Forum on Contaminated Land. Report of the Warsaw Meeting, September 18, 1998. Report from the Swiss Agency for the Environment, Forests and Landscape.
9. Ad Hoc International Working Group on Contaminated Land (1998). Papers from the International Workshop on Land Recovery and Man-Made Risks held in Vienna, November 16-18, 1998.
10. Schaefer, K.W., F. Bieren, et al. (1997). Internationale Erfahrungen der Herangehensweise an die Erfassung, Erkundung Bewertung und Sanierung Militärischer Altlasten. Umweltbundesamt (Federal Environment Agency), volume 1 and 2, Berlin, Germany.
11. Siuta J. (1997). Chemical degradation and regeneration of soils and wastes. In: Element Cycling in the Environment. II International Scientific-Technical Conference. Proc. Institute of Environmental Protection, Warsaw. In Polish.
12. State Inspectorate for Environmental Protection (1998). State of the environment in Poland. Report.
    The State Inspectorate for Environmental Protection, Warsaw. In Polish.
13. Gworek, B., M. Borowiak & K. Jeske (1997). Remediation of soils polluted by heavy metals. In: Element Cycling in the Environment. II International Scientific-Technical Conference. Proc. Institute of Environmental Protection, Warsaw. In Polish.
14. Gworek, B., M. Borowiak & E. Nalborczyk (1998). Remediation of soils polluted by heavy metals. In: Race News. Contaminated Land Management in Central and Eastern Europe. Katowice, 80-81. In Polish.
15. Czajkowski, A., J. Czajkowski, B. Kolwzan, K. Piekarska & M. Pawlik (1997). Clean-up of land and groundwater polluted by petroleum products and other organic compounds. In: Technologies for deoiling of grounds, wastes and wastewaters. Polish Society of Ecological Engineering. I Scientific-Technical Conference. Proc. 59-66. In Polish.
16. Lebkowska, M., A. Marchwinska, E. Sztompka, E. Karwowska & E. Miaskiewicz (1997). Microbiological remediation of grounds polluted by petroleum products. In: Technologies for deoiling of grounds, wastes and wastewaters. Polish Society of Ecological Engineering. I Scientific-Technical Conference. Proc. 115-118. In Polish.
17. Siuta, J. (1997). Biodegradation of petroleum products in soils and wastes. In: Technologies for deoiling of grounds, wastes and wastewaters. Polish Society of Ecological Engineering. I Scientific-Technical Conference. Proc. 119-130. In Polish.