Contaminated land can be located in urban or rural zones, in active or abandoned industrial sites. Contamination can be the result of deliberate or accidental release or disposal of substances in, on or under the land. There are also sites that are affected by contamination that do not meet this strict definition. Also, not all land that is derelict or has been previously used (brownfield) is necessarily contaminated.
The immision of organic or metallic contaminants into the soil may result in damage to, or loss of some or several functions of soils and possible cross contamination of water. The occurrence in soils of contaminants at concentrations above certain levels can result in multiple negative consequences for the food chain and thus for human health, and for all types of ecosystems and other natural resources.
To assess the potential impact of soil contaminants, account needs to be taken not only of their concentration but also their environmental behaviour and the exposure mechanism for human health. Often a distinction is made between soil contamination originating from clearly confined sources (local or point source contamination) and that caused by diffuse sources.
1. General Issues and Good Practice
Estimates of the number of contaminated sites in the European Union range from 300 000 to 1.5 million. This wide range in estimation is due to the lack of a common definition for contaminated sites and relates to different approaches to acceptable risk levels, targets to be protected and exposure parameters. Although the largest and most affected areas are concentrated around the heavily industrialised regions, contaminated sites exist everywhere throughout the continent . Nowadays, most countries approach is risk assessment and management based upon different principles such as "pollutant-payer" and "fit for use". The process of contaminated site management should follow methodical and standardised practice.
Contaminants may be organic (e.g. dioxins, polycyclic aromatic hydrocarbons) or inorganic (e.g. metals, nitrogen, asbestos, sulphuric acid) elements or compounds. They demonstrate varying mobility properties in soils, and from soils towards water resources. Potentially organic compound biodegradation and the variable degree of oxidation of metals may produce compounds that are less or more toxic or mobile. Contaminated land management requires various approaches depending on the different kind of contaminant sources, impacted media, contaminants distribution and the present or future targets potentially submitted to hazards.
3. Cost benefit analysis
Cost benefit analysis assists decision-making for contaminated site management and identification of the eventual remediation options. The analysis should take into account the whole environmental and socio-economic context of the contaminated sites and its surroundings. Cost benefit tools allow a quantitative evaluation of a complex decision that integrates the historical, ecological, patrimonial and social aspects and the planned future use of the site. Decisions concerning the environment always involve costs and benefits some with monetary values and some without. Ideally decisions are made such that the benefits outweigh the costs.
4. Information management system
Many government and private organisations have developed or are developing site specific data management and display systems for decision support. Through the visualisation and graphical representation of data these systems can enable a more thorough conceptual understanding of the site and the risks involved than is possible from the written report. Great advantage can be drawn from the use of information management systems to collect, store and interpret the considerable quantity of data amassed during studies and analysis. Electronic databases can be crossed-referenced in order to identify correlation between parameters. Geographical information systems can be used to overlay figures and text on maps where topography, geology, geography, vegetation, roads, rivers and other data are represented. Predictive modelling is used to determine the location of contaminants in soils and groundwater or to predict the effect of alternative remediation options.
Mega-sites are large scale contaminated sites, which pose a large potential or an actual risk of deterioration to groundwater, sediment, soil and surface-water quality. They require complicated and costly remediation (e.g.: mine sites, asbestos sites or more frequently large industrial installations). They may have very complicated histories with several owners (past and present), development or recession periods, accidents and multiple contamination sources. They require long and complicated studies, the input and agreement of many diverse stakeholders and may therefore take many years to remediate.
6. Remediation options
Remediation technologies are directed at immobilising pollutants or bringing back their concentrations below acceptable thresholds. Resulting of the risk assessment recommendations, and depending of the results of cost benefit and technical analyses, contaminant treatment may be performed in situ or ex situ. In situ technologies avoid expensive excavation of soils but may not be practical or effective in all situations. In these circumstances, ex situ technologies have to be used on-site or at an off-site specialised installation.
7. Risk assessment
Risk assessment is a structured method of analysis, where the data elements are collected, ordered and evaluated in order to quantify the risk in a transparent way. It allows the manager to act with the best possible visibility on the situations of pollution, by knowing the possible medical influence of the different decisions. The general approach of risk assessment is based upon the coexistence of a contaminant source (resulting in a concentration above a certain level), a potential vector for mobilisation and transfer (a pathway) of the contaminant and a target. The elimination or the absence of any one of these three components is enough to declare that there is no risk. To assess the potential impact of soil contaminants, account needs to be taken not only of their concentration but also their environmental behaviour and the exposure mechanism for human health .
8. Risk management
Risk management is a decision-making approach for historically contaminated sites where the need for action, and the nature of any possible action, is decided on the basis of risk assessment. Risk management based on risk assessment includes: site investigation, monitoring, selection of suitable remediation options and aftercare of the site.
9. Site investigation
The process of site identification and investigation follows a stepwise procedure that includes the following elements in the following order:
· Preliminary survey: Historical survey of the potential contamination. In most cases sites are defined as potentially contaminated sites;
· Preliminary site investigation: Limited technical investigation of the possible contamination. In most cases this step defines sites as contaminated;
· Main site investigation: Detailed investigation with the objective of deciding on remedial treatment.
There is general agreement on which pieces of information should be included in the preliminary survey. However, the quality, classification system, and the exact type and amount of information required varies significantly from country to country and even within countries. In general, the main principles and objectives of the preliminary investigation are very similar. For most countries, the investigation level is described as a very limited investigation where only a few samples are analysed and the main aim is confirming the presence of contamination. In all countries the basis of investigation is identification of likely spatial distribution of the contamination…/…In all countries the decision to define a site as contaminated is based on the results of technical investigations. The aim of the investigation is the risk assessment and the reduction of uncertainties, in order to make the best possible decision.
Figure 1: The major steps in the identification process .
10. Soil and groundwater processes
Contaminants behaviour and transfer from soil into ground water and subsequently into ecosystem and the food chain depends mostly on the hydrogeology, geochemistry and microbiology of soils. Studying these phenomena is a major step towards gaining understanding of the impacts and the interpretation of data. The understanding of these processes assists engineers in the prediction of the contaminant plume evolution in soil and groundwater. Numerous research programs for modelling soil and groundwater processes are in progress, details of which can be found within the relevant section of EUGRIS.
11. Wider impacts/sustainability
Study of the wider impacts study provides information on the consequences of contamination for the economy, the environment and society in the region where the contamination occurs. This process takes into account the indirect impact of contamination on employment, the health of the people living near the contaminated site, the cost of health care, the biodiversity and tourism. Each impact has to be assessed as an economic or adverse impact on public perception of an area. Wider impacts than just those immediate to the environment of a site and the health of those living and working on it have to be included into contaminated land management systems.
DARMENDRAIL D., BRUNET JF., BRGM - Environment&Process Division, www.brgm.fr
Management of contaminated sites in
to the European Union
Communication from the Commission to the Council, the European Parliament, the Economic and Social Committee and the Committe of the Regions - Towards a Thematic Strategy for Soil Protection. 16 April 2002
Ad Hoc International Working Group on Contaminated Land
meeting of the Ad Hoc International Working Group on Contaminated Land, 17th
– 18th March 2003, Montréal (Canada) – March 2004
Management of contaminated sites in
CLARINET report - Sustainable Management of Contaminated
Land: An overview - August 2002.
Common Forum on Contaminated Land in the European Union
Final Report of the
Final Report of the Larnaca
Report of the
Useful Web Links
International Working Group on Contaminated Land
(EC 4Th Framework Research Program)
Contaminated Land Reclamation Network for Environmental Technologies in
(EC 5Th Framework Research Program)
Integrated Pollution Prevention and Control Bureau
Groundwater Risk Assessment at Contaminated Sites
(EC 5Th Framework Research Program)
The Network for Industrially
Integrated Soil and Water Protection: Risks from Diffuse Pollution
(EC 5Th Framework Research Program)
United Nation Environment Program
Production and consumption Unit - Contaminated land heading