Cleaning up heavily polluted soils in China
Extensive areas of land in China are contaminated with heavy metals. The main sources of this pollution are past and present mines and mining activities, other industries and diffuse pollution caused by industry and agriculture. Soils contaminated with heavy metals, but not at extreme concentrations, can no longer be used for a range of different uses, e.g. agricultural use is ruled out because the level of contamination in crops grown on such soils makes them unfit for human consumption. Soils that are very heavily contaminated with heavy metals become largely denuded of vegetation, leading to erosion and increased leaching of heavy metals to the groundwater. Eroded material carries the contamination to neighbouring areas.
In recent years the Environmental Sciences Group has gained considerable knowledge about the transfer of heavy metals between soil particles and soil pore water and their uptake by plants. Our expertise covers both the processes involved and application of this knowledge in:
- determining quality standards based on risks, specified per soil type and land use;
- manipulating the uptake of heavy metals by crops, both to reduce levels of uptake (to minimise heavy metal pollution in agricultural produce) and to increase uptake (for phytoremediation, in which plants are used to remove the heavy metals from the soil);
- actively managing heavily polluted soils, with particular attention to using plants to control erosion and leaching of contaminants to the groundwater.
The process research and the first-mentioned application are financed primarily by the Netherlands Ministry of Agriculture, Nature and Food Quality. The last two applications are financed mainly through the EU PhytoDec project (completed in 2004) and through projects funded by Bodembeheer de Kempen, Tilburg Municipal Council and Stichting Bodembeheer Krimpenerwaard.
Cooperation with China
Our Chinese partner (ISSCAS) is coordinating a major national multidisciplinary programme (with a budget of about 3 million euros) to map and contain the environmental risks in the Yangtze delta and the Pearl River delta. Three of the projects within this programme may be considered to be ‘mirror projects’ of the projects listed in the previous paragraph. The goal of this collaborative project is to link together the various projects and enhance the scientific input. Joint research is being conducted into the use of crops to reduce the risks posed by areas of land contaminated with heavy metals.
The main objective of the study is to forge a strategic alliance that is ‘sustainable’. At the moment research is being carried out in the following areas (simultaneously in Wageningen and China):
- using plants to clean up land contaminated with copper. To improve this process tests are being conducted on the use of decomposable chemical substances that increase the availability of copper for uptake by plant roots;
- testing crops that are able to grow on heavily contaminated land. Development of a dense plant cover can halt erosion and thus prevent pollutants from spreading to other areas (especially to surface waters). Additional funds are obtained through an ISOM subsidy to hold trials with energy crops on polluted soil in China, with a view to their commercial use.
Partners
- Soil Science Centre, Soil Chemistry and Nature team, Alterra (coordination)
- Soil Quality chair section, Environmental Sciences Department, Wageningen University
- Institute of Soil Science of the Chinese Academy of Sciences (ISSCAS), Nanjing, China
- Czech Academy of Sciences, Prague, Czech Republic (informal participation with own national budgets)