Soil pollution is a serious threat to food safety and public health in China. One of the main drivers for land contamination is industrial and mining wastewater discharge.
Choose a crop Production, tonnes per hectare
The use of wastewater containing industrial discharges for agriculture leads to heavy metal accumulation in soil. The Chinese government conducted a nationwide survey between 2005 and 2013 to establish the extent of land contamination. The survey covered 6.3 million square kilometers of various land types. Around a fifth of this land was found to be contaminated.
The National Survey of Soil Pollution also indicates the extent of heavy metal contaminants in the surface soil compared to the soil quality surveyed during the 7th Five Year Plan (1985-1990). Cadmium was most prevalent in the soil sampled.
Forecasts by government-backed research institutes suggest the market for land treatment, or remediation, could generate 200 billion yuan in annual revenue by 2025. A number of technologies exist but due to the scale of the problem, a systematic and combined approach to remediation as well as selective land use is the most feasible solution. Options include:
A form of in situ contaminant immobilisation. Adding lime to soil does not completely remove the metals but reduces their activity.
Soil excavation engineering
Involves removing contaminated soil and disposing or treating off-site. Currently the most used form of soil remediation in China.
Many micro-organisms, plants and fungi are able to bind, extract or transform contaminants in soil to create a less toxic ecosystem.
Another on-site option involves heating the ground to release contaminants as gas which can then be further treated nearby.
Note: 1000 micrograms = 1 milligram
* The level of contamination ranges from slight to severe. The report defines slight contamination as one to two times above standard; mild as between two and three times above; moderate as three to five times; and severe as more than five times above the standard.
Sources: National Bureau of Statistics of China; Ministry of Environmental Protection; Ministry of Land Resources; Earth Repair; The Nature Education Knowledge Project; British Lime
Graphic by Jane Pong, Simon Scarr, Matthew Weber