Soil Heavy Metal Levels Exceeding Standards Endanger Agricultural Product Safety, Situation Severe in Some Local Areas of China
Reporters learned from the recently held Fourth China Environmental Remediation Forum that the current soil pollution situation in our country is severe, with prominent soil pollution hazards in local and partial areas, already posing a threat to agricultural product safety. Soil pollution remediation is urgent, and it is imperative to start from strengthening legislation, improving standards, and raising technical levels to effectively advance the implementation of soil pollution remediation work.
Prominent Soil Pollution Hazards
Endangering Agricultural Product Safety
The "National Soil Pollution Survey Bulletin" recently released by the Ministry of Environmental Protection and the Ministry of Land and Resources shows that the overall exceedance rate of soil pollution nationwide is 16.1%, among which slightly, mildly, moderately, and severely polluted sites account for 12.1%, 2.3%, 1.5%, and 1.1% respectively; Class I and Class II soils suitable for agricultural cultivation in our country account for 87.9%, those with potential ecological risks account for 12.1%, among which soils under moderate and severe pollution account for about 3.0%.
Land pollution is mainly manifested in soil acidification and decline in organic matter. Wei Fusheng, an academician of the Chinese Academy of Engineering, said that soils in the south are naturally mostly acidic, but due to massive application of chemical fertilizers, combined with the impact of acid rain, acidity has further increased. In some areas, soil pH has dropped by an average of 0.5-0.7 pH units, and some even by 2.1 pH units. For example, strongly acidic soil in Hunan (pH 4.5-5.5) increased from 491,300 hectares in the mid-1980s to 1,456,700 hectares in 2006-2010.
Soil acidification and decline in soil organic matter are not conducive to the complexation and fixation of heavy metals. Organic matter in the black soil region of Northeast China has dropped from 8%-10% at the time of reclamation to the current 2%-3%. The application of organic fertilizer has generally decreased, leading to soil degradation.
Expert research suggests that the main reasons for the intensification of soil pollution in our country over the years are mainly excessive application of chemical fertilizers, as well as excessive and unscientific use of pesticides, causing pesticide residues to exceed standards. Since 1984, the use of chemical fertilizers (nitrogen fertilizer and phosphate fertilizer) in our country has continued to increase, currently averaging 400 kg per hectare, with the eastern region reaching as high as 600 kg per hectare, more than 1.8 times the internationally recognized warning upper limit (225 kg per hectare), and more than 4 times the average use in Europe and America.
In addition, although in recent years our country has eliminated and banned highly toxic and high-residue pesticides (organochlorines and organophosphates), and new pesticide varieties have been continuously introduced to the market, greatly reducing poisoning incidents among humans and livestock and raising the qualification rate of grain and vegetable pesticide residues, the current pesticide use in our country is still twice the world average. Technical guidance for scientific and rational pesticide use in agricultural pest early warning and forecasting is insufficient. Research and promotion of green pest control methods, such as physical and biological control methods, are insufficient, and cannot reduce the use of pesticides, antibiotics, and plant growth regulators.
Soil pollution poses a threat to agricultural product safety. In 2013, the China National Environmental Monitoring Centre collected 4,910 sites in vegetable growing areas and found 1,188 sites exceeding standards, accounting for 24.3%, among which slight pollution accounted for 16.8%, mild pollution 5.3%, and moderate and severe pollution 2.1% and 1.0% respectively; heavy metal pollution accounted for 17.5%, organic pollution 7.9%, and compound pollution 1.3%.
Alarming Heavy Metal Exceedances in Local and Partial Areas
Remediation Faces Multiple Challenges
Wei Fusheng said that the overall situation of land pollution in our country is that soil pollution is relatively severe in some areas, especially in local and partial areas such as land used by heavily polluting enterprises and surrounding areas, industrial waste land, industrial parks, centralized solid waste treatment and disposal sites, oil extraction areas, mining areas, sewage irrigation areas, and both sides of trunk highways. The main pollutants are cadmium, arsenic, lead, mercury, chromium, copper, etc.
The results of the China National Environmental Monitoring Centre's 2011 survey and monitoring of soil around 284 industrial and mining enterprises show that clean and still-clean soil accounted for 68.1%, mild pollution 13.1%, moderate pollution 3.3%, and severe pollution 13.5%.
In 2011, the Ministry of Agriculture surveyed 2.372 million mu of paddy fields in 88 counties in key polluted areas of Hubei, Hunan, Jiangxi, and Sichuan provinces. The area exceeding standards was 1.608 million mu, with an exceedance rate of 67.8%. Among these, cadmium pollution was the most prominent, followed by arsenic, nickel, copper, mercury, and chromium, while exceedance rates for other heavy metals were relatively low.
Reporters learned that the issue of land pollution remediation has attracted attention. The government, the public, and scientific and engineering personnel are concerned about it, and some important projects have been launched domestically, such as remediation of the Beijing Coking Plant, the Hangzhou Pesticide Factory, and heavy metal-polluted farmland in the Changsha-Zhuzhou-Xiangtan area.
In addition, the Ministry of Environmental Protection has also issued five technical documents for contaminated site remediation, including the "Technical Guidelines for Site Environmental Investigation," "Technical Guidelines for Site Environmental Monitoring," "Technical Guidelines for Risk Assessment of Contaminated Sites," "Technical Guidelines for Remediation of Contaminated Sites," and "Terminology for Contaminated Sites," to guide investigation and assessment of contaminated sites.
However, many experts report that, on the whole, soil pollution remediation work in our country still faces multiple challenges, such as serious lag in the formulation of soil environmental protection laws and regulations, lagging and missing soil environmental quality standards, lack of standards for pollutant types and concentration limits, unclear soil remediation targets, insufficient research and development reserves and few successful cases for soil remediation technologies, equipment, and agents, and how to prevent and control secondary pollution during the remediation process.
Urgent Need for Multiple Measures Including Legislation, Standards, and Technology
Effectively Advancing Soil Pollution Remediation
In response to the above-mentioned reality of soil pollution, interviewed experts and scholars suggest taking multiple measures to improve the effectiveness of soil pollution remediation work.
First, it is suggested to strengthen legislative work related to soil environmental protection. The state has included soil environmental protection and pollution prevention legislation in its plans and has already done a great deal of preliminary work. It is suggested to accelerate the pace of legislation, clarify the legal responsibilities and obligations of each department, regulate their production and living activities, and achieve coordinated cooperation among relevant departments, each fulfilling its duties and jointly managing, with air, water, solid waste, and soil pollution prevented and treated together. Enhance soil fertility and prevent and control pollution to ensure both the quantity and quality safety of edible agricultural products in our country.
Wei Fusheng suggested formulating a national-level "Pesticide Management Law" and "Chemical Fertilizer Management Law," drawing on the advanced experience of Europe and America, strengthening the registration and re-registration management of pesticides, and implementing supervision over the entire process of pesticide production, operation, and use. Strengthen the scientific and rational use of chemical fertilizers and improve the utilization rate of chemical fertilizers in the current season. With reference to EU practices, implement total quantity control of chemical fertilizers, reduce the application of nitrogen and phosphate fertilizers, use more organic fertilizers, improve the effective utilization rate of fertilizers, and enhance soil fertility and the quality of agricultural products.
Second, drawing on foreign experience with "dual indicators" and "graded standards," the government should organize research to revise and formulate soil environmental quality standards. Research and formulate a "dual indicator" standard system of "total content" and "soluble form" for soil pollution factors, to provide a scientific basis for risk assessment and risk management of soil pollution. On the basis of the "dual indicators," then research and formulate a graded standard system according to national conditions and local realities, to provide standard-based basis for graded development and utilization of soil and remediation and treatment of soil pollution.
Hu Qing, chairman of China Energy Conservation and Environmental Protection Group Dadi Environmental Remediation Co., Ltd., believes that a soil remediation standard system that conforms to China's reality and is operable should include political, management, technical, and training systems, among other aspects.
Third, strengthen research and development and demonstration of land pollution remediation technologies, standardize market order, raise the technical access threshold, enhance corporate social responsibility, and compile successful remediation cases each year for promotion.
Li Guanghe, a professor at the School of Environment of Tsinghua University, said that in currently advancing soil pollution remediation work in our country, technical weaknesses are prominent, and problems are often solved on a case-by-case basis with a lack of innovative thinking. "It is necessary to cultivate high-level design and planning teams for land pollution remediation projects, foster innovative and leading engineering thinking, and be able to propose new concepts in green remediation and low-cost remediation."