|Soil contamination in Spain|
|Soil Pollution in Romania (English subtitles)|
What is Soil Contamination?
Soil contamination is the occurrence of contaminants in soil above a certain level causing deterioration or loss of one or more soil functions.1 It occurs in 2 forms:
- ‘Point pollution’, caused by a specific event or series of events to a particular place, such as a former factory site. This is relatively well mapped and understood.
- ‘Diffuse pollution’, this involves low levels of contaminants spread over very wide areas that become lodged in the soil as it acts as a sink. This is difficult to analyze and track. Examples of such contaminants would be heavy metals or herbicides or pesticides used in agriculture.
Soil pollutants can consist of various forms, such as organic and inorganic or particulate pollutants.2
Where does it occur?
Heavy metal content in European soils3
As the name suggests point pollution can be found in particular places, such as ex-industrial land, or areas subject to accidental spillage of contaminants. Diffuse pollution is much more widely spread but as the maps below illustrate there is great variation between nations and areas depending on the practices that give rise to this form of contamination.
There may be as many as 2.5 million potentially contaminated sites across Europe, which need to be investigated. Of these, approximately 14% (340,000 sites) are expected to be contaminated and likely to require remediation. Approximately one-third of these contaminated sites have already been identified and around 15% have been remediated.4
What causes it?
The most important sources of contamination in soils are those connected with human activities. Examples of point pollution include metal mining and smelting, industrial production, waste disposal and diffuse pollution examples include industrial activities, car emissions, application of agrochemicals, manure containing veterinary drugs, etc.
Municipal and industrial wastes contribute most to soil contamination (37%), followed by the industrial/commercial sector (33%). Mineral oil and heavy metals are the main contaminants contributing around 60% to soil contamination. In terms of budget, the management of contaminated sites is estimated to cost around 6 billion Euros (€) annually.5
How can it be measured or assessed?
The table below shows the list of indicators for soil pollution.6, 7
|Diffuse pollution by Inorganic pollutants||Which areas show critical heavy metal contents in excess of national thresholds?||Heavy metal contents in soils|
|Diffuse pollution by Inorganic pollutants||Are we protecting the environment effectively against heavy metal pollution?||Critical load exceedance by heavy metals|
|Diffuse pollution by nutrients and biocides||What are the environmentally relevant key trends in agricultural production systems?||Area under organic farming|
|Diffuse pollution by nutrients and biocides||Is the environmental impact of agriculture developing?||Gross nutrient balance|
|Diffuse pollution by persistent organic pollutants||Which areas show critical concentration of organic pollutants?||Concentration of persistent organic pollutants|
|Diffuse pollution by soil acidifying substances||How is the environmental impact of soil acidification developing?||Topsoil pH|
|Diffuse pollution by soil acidifying substances||Are we protecting the environment effectively against acidification and eutrophication?||Critical load exceedance by sulphur and nitrogen|
|Local soil pollution by point sources||How is the management of contaminated sites progressing?||Progress in management of contaminated sites|
|Local soil pollution by point sources||Is developed land efficiently used?||New settlements established on previously developed land|
|Local soil pollution by point sources||How many sites exist which might be contaminated?||Status of site identification|
|Filtering function of soil||What is the impact on soil function?||Cation exchange capacity|
|Filtering function of soil||Is there a loss of organic matter?||Organic matter content|
|Filtering function of soil||What is the actual availability of pollutants for plants and animals?||Bioavailability of pollutants|
How can it be prevented or remediated?
Soil contamination can pose a direct threat to human well-being, with prevention being the focus of most policy measures. The table below shows a Draft outline of a strategy for sustainable land management
|Objectives (Mitigation of soil threats)||Appropriated technologies |
|Appropriated technologies |
|Soil pollution assessment||Statistical and geochemical techniques||Development of relationships between soil indicators and the numerous soil functions||Polluting Company, Regional and National Governments|
|Reduce pollutants||Sludge removal||Equipment and adequate infrastructure||Polluting Company, Regional and National Governments|
|Improve soil quality||Liming and organic amendment application||Increasing pH, decreasing metal availability and improving soil conditions for restoration and afforestation||Polluting Company, Regional and National Governments|
|Improve environmental quality||Afforestation and revegetation||Phytostabilization of soil contamination and improving soil properties and biogeochemical cycles||Polluting Company, Regional and National Governments|
|Policy recommendations||Regulation and environmental education about uses of this area||Protection of affected area and restricted uses. Public awareness.||Regional, National and European Governments|
Case Study Experiments
How does it interact with other soil threats?
Soil contamination leads to decreased activity of soil biodiversity and therefore to a decline of aggregate stability and in decomposition processes. Strong correlation can also be seen between contamination and erosion. A decline in aggregate stability and organic matter caused by soil pollutants increases the erodibility and therefore the risk of wind and water erosion. Landslides, flooding, wind and water erosion may also lead to pollutants being transported off site as solutes or particles and in turn pollute the connected aquatic environment or soils downslope.
How does it affect soil functions?
- Biomass production - a contaminated soil loses the productivity and the capacity to support plants properly.
- Storing, filtering and transforming – these functions are all disrupted or prevented in contaminated soil. In particular, organic matter decomposition can be disrupted affecting the cycling of nutrients.
- Gene pool (biodiversity) - plants, micro-organisms and enzyme activity in the soil is disrupted and lessened in contaminated soil, leading to a decline in soil biodiversity.
1 JRC.2014. Soil themes: soil contamination. http://eusoils.jrc.ec.europa.eu/library/ themes/contamination/ (last accessed at 29.07.2014)
2 Mirsal, I.A., 2008. Soil Pollution.Origin Monitoring & Remediation.2nd Edition. Springer-Verlag, Berlin
3 Lado, L. R., Hengl, T., & Reuter, H. I. 2008. Heavy metals in European soils: A geostatistical analysis of the FOREGS Geochemical database. Geoderma, 148(2), 189-199.
4 JRC. 2014. Progress in the management of Contaminated Sites in Europe. http://eusoils.jrc.ec.europa.eu/ESDB_Archive/eusoils_docs/other/EUR26376EN.pdf (last accesed at 25/02/2016).
5 Panagos P, Liedekerke MV, Yigini Y, Montanarella L. 2013. Contaminated sites in Europe: review of the current situation based on data collected through a European network. Journal of Environmental and Public Health. Article ID 158764.
6 Huber, S., Prokop, G., Arrouays, D., Banko, G., Bispo, A., Jones, R., Kibblewhite, M., Lexer, W., Möller, A., Rickson, J., Shishkov, T., Stephens, M., Van den Akker, J., Varallyay, G., Verheijen, F., 2008. Indicators and Criteria report. ENVASSO Project (Contract 022713) coordinated by Cranfield University, UK, for Scientific Support to Policy, European Commission 6th Framework Research Programme.
7 De la Rosa, D., Sobral, R., 2008, Soil quality and methods for its assessment, Land use and soil resources, Springer, pp. 167-200.
8 Shayler, H. et al , 2009 Sources and Impacts of Contaminants in Soils