Why is farmland soil remediation still a blank slate?

Current situation: domestically, the reserve of farmland remediation technologies or the accumulation of applied engineering case studies is currently very limited; the so-called farmland soil remediation demonstration projects generally suffer from many problems such as undisclosed processes, undisclosed technologies and unclear costs, and are of little value for reference and promotion

Suggestions: the state should introduce preferential incentive policies in agriculture, grant enterprises longer-term land management rights, and guide and support the cultivation of high-value cash crops or eco-friendly green food to raise the output of each mu of farmland soil

Liu Yangsheng, secretary-general of the Heavy Metal Pollution Prevention and Soil Remediation Professional Committee of the China Association of Environmental Protection Industry and a professor at the College of Environmental Sciences of Peking University, said in an exclusive interview with our newspaper's reporter a few days ago that he is currently not worried about urban industrial site remediation, because "standards are becoming increasingly standardized, technologies are relatively mature, and a market has already formed driven by the value of land redevelopment." By contrast, he is more concerned about the issue of farmland soil remediation. "From the feedback we get from enterprises, the most concentrated voices come from several aspects: first, a lack of remediation standards; second, a lack of project demonstrations; third, a lack of business models."

It is suggested that the new standards shift toward a method based mainly on controlling pollutant activity, and that the relevant basic data census be improved before they are issued

At the beginning of this year, when the Ministry of Environmental Protection decided to solicit public opinions on revising the current "Environmental Quality Standard for Soils" into the "Environmental Quality Standard for Agricultural Land Soils," Liu Yangsheng submitted dozens of specific suggestions in total. In his view, the "Environmental Quality Standard for Soils," implemented since 1995, can no longer adapt to current requirements.

Liu Yangsheng believes that "unlike industrial sites, where solidification and stabilization remediation technologies can be used to prevent the risk of pollutants being exposed in the environment, farmland is a living entity, and plants will change the forms in which various heavy metal pollutants exist around their root systems during the growth process. Therefore, there are phenomena in which the soil in some areas does not exceed the standard, but the grain grown is above the standard; and in some areas the soil exceeds the standard value by dozens of times, but the grain is still safe."

He stated that this is closely related to the activity of pollutants, "for example, chromium is difficult for crops to absorb under inert conditions." He also found in his own experiments that in the same plot of soil with excessive heavy metals, the absorption conditions of different crops are also different.

"The current standard's approach of total amount control has many problems, and the newly revised standard should shift toward a method based mainly on controlling pollutant activity." However, Liu Yangsheng also admitted that such a control method has a certain degree of difficulty in specific operation. "For example, the acidity and alkalinity of soil differ between the north and the south, and issues such as which crops to choose to plant on different types of polluted farmland without affecting food security all require systematic research." Therefore, he suggested that the relevant basic data census should be improved before the new standard is issued.

There are no successful cases abroad for reference, and domestic farmland soil remediation demonstration projects generally have problems, so they are of little value for reference and promotion

"Abroad, no country like China has such a large area of farmland heavy metal pollution. Therefore, no real farmland remediation industry has formed abroad, and there are no ready-made successful cases for us to refer to." Liu Yangsheng pointed out that domestically, the reserve of farmland remediation technologies or the accumulation of applied engineering case studies is currently very limited, and the so-called farmland soil remediation demonstration projects generally suffer from many problems such as "undisclosed processes, undisclosed technologies and unclear costs," and are of little value for reference and promotion.

He believes that the basic principle of farmland soil prevention and control should put protection first; unpolluted farmland must be prevented from being threatened by pollution again, and differentiated remediation technologies and plans should be adopted for lightly polluted and heavily polluted farmland soil.

"For farmland soil with relatively light pollution, strengthening and promoting farmland management may be more important than applying remediation agents, and farmers are more likely to accept low-cost plans." Liu Yangsheng said: "Take wheat as an example. During the entire growth process, the ability of roots, stems and leaves to absorb heavy metals from the soil is different, so if at the stage when absorption capacity is particularly strong, the degree of waterlogging tolerance in the farmland soil is changed, for example, to keep it in an anaerobic environment, then the amount of heavy metals absorbed by the plants at that time will be smaller."

As for farmland soil with relatively heavy pollution, Liu Yangsheng believes that the urgent task should be to develop relatively mature, stable and low-cost green remediation technologies, and to pay attention to the resource utilization of soil. "The surface soil was formed over thousands of years; if soil remediation does not consider resource utilization, it is a huge waste of resources."

There is an urgent need to explore feasible business models, guide social capital to participate, and it is suggested that the state issue preferential incentive policies in agriculture

"In cities, a remediation market driven by the value of land redevelopment has already formed, and industrially polluted sites are monetized through bidding, auction and listing after remediation. Farmland is different; compared with remediation costs, its output value is relatively low. Therefore, the source of funding for farmland soil remediation is a problem." Liu Yangsheng stated that because the sources of farmland pollution are complex and the responsible parties are difficult to determine, farmers are also unable to bear the remediation costs, so at the present stage remediation funds mainly come from state finances.

"It is also unrealistic to let the state bear everything. At present, there is an urgent need to explore feasible business models and guide social capital to participate. However, all business models involve the return of benefits, and if there is no return, it is unrealistic to ask enterprises to invest money in remediation." He suggested that the state should introduce preferential incentive policies in agriculture, grant enterprises longer-term land management rights, and guide and support the cultivation of high-value cash crops or eco-friendly green food to raise the output of each mu of farmland soil.

Because food security is involved, Liu Yangsheng does not approve of easily changing the properties of farmland soil. He believes: "The core of the business model can only be to take from the soil and use it for the soil."