Heavy metals in China's local soil exceed the standard, endangering the safety of agricultural products

The reporter learned from the fourth China Environmental Restoration Forum held a few days ago that the current situation of soil pollution in China is grim, and the hidden dangers of soil pollution in local and local areas are prominent, which has posed a threat to the safety of agricultural products, and soil pollution remediation is extremely urgent. there is an urgent need to strengthen legislation, improve standards, improve technology and other aspects to effectively promote the implementation of soil pollution remediation.

The hidden danger of soil pollution is prominent.

Endanger the safety of agricultural products

According to the National soil pollution investigation Bulletin recently issued by the Ministry of Environmental Protection and the Ministry of Land and Resources, the total over-standard rate of soil pollution in the country is 16.1%. The mild, mild, moderate and severe pollution points were 12.1%, 2.3%, 1.5% and 1.1%, respectively. The first and second types of soils suitable for agricultural cultivation in China account for 87.9%, and those with potential ecological risks account for 12.1%, of which moderately and heavily polluted soils account for about 3.0%.

Land pollution is mainly manifested in soil acidification and the decrease of organic matter. Wei Fusheng, academician of the Chinese Academy of Engineering, said that most of the soils in the south were acidic, but due to the massive application of chemical fertilizers and the influence of acid rain, the acidity further increased. In some areas, the soil PH value decreased by an average of 0.5-0.7 PH units, and some even decreased by 2.1 PH units. For example, the strongly acidic soil in Hunan (PH 4.5-5.5) decreased from 491300 hectares in the mid-1980s. It will increase to 1.4567 million hectares by 2006-2010.

Soil acidification and the decrease of soil organic matter are not conducive to the complex fixation of heavy metals. The organic matter in the northeast black soil area has decreased from 8% Mel 10% at the time of reclamation to 2% Mel 3% at present, and the application of organic fertilizer has generally decreased, resulting in soil degradation.

According to expert research, the aggravation of soil pollution in China over the years is mainly due to excessive application of chemical fertilizers, excessive and unscientific use of pesticides, resulting in excessive agricultural residues. Since 1984, the amount of chemical fertilizer (nitrogen fertilizer and phosphate fertilizer) in China has continued to increase, with an average consumption of 400 kg per hectare at present, and 600 kg per hectare in the eastern region, which is more than 1.8 times the world's generally recognized warning limit (225 kg per hectare). It is more than four times the average consumption in Europe and the United States.

In addition, although highly toxic and residual pesticides (organochlorine and organophosphorus) have been eliminated and banned in China in recent years, new varieties of pesticides have been continuously put on the market, resulting in a significant decrease in the incidence of human and animal poisoning and an increase in the qualified rate of grain and vegetable farmers. however, at present, the amount of pesticides in China is still twice the world average, the technical guidance for scientific and rational use of agricultural diseases and insect pests is insufficient, and green methods are adopted to prevent and control agricultural diseases and insect pests. For example, the research and promotion of physical and biological control methods are not enough to reduce the use of pesticides, antibiotics and plant growth regulators.

Soil pollution poses a threat to the safety of agricultural products. In 2013, the China Environmental Monitoring Station collected 4910 sites in vegetable growing areas, and found that 1188 sites exceeded the standard, accounting for 24.3%, of which mild pollution accounted for 16.8%, mild pollution accounted for 5.3%, moderate and severe pollution accounted for 2.1% and 1.0%, respectively. Heavy metal pollution accounted for 17.5%, organic pollution accounted for 7.9%, and compound pollution accounted for 1.3%.

It is amazing that the local heavy metals exceed the standard.

Restoration faces multiple challenges

Wei Fusheng said: at present, the overall situation of land pollution in China is that soil pollution is relatively serious in some areas. especially in local and local areas such as heavily polluted enterprise land and its surrounding areas, industrial wasteland, industrial parks, sites for centralized treatment and disposal of solid waste, oil production areas, mining areas, sewage irrigation areas, and both sides of trunk roads, the main pollutants are cadmium, arsenic, lead, mercury, chromium, copper, and so on.

The results of soil investigation and monitoring of 284 industrial and mining enterprises by China Environmental Monitoring Station in 2011 showed that clean and still clean soil accounted for 68.1%, mild pollution accounted for 13.1%, moderate pollution accounted for 3.3%, and severe pollution accounted for 13.5%.

In 2011, the Ministry of Agriculture investigated 2.372 million mu of paddy fields in 88 counties in key polluted areas of Hubei, Hunan, Jiangxi and Sichuan provinces. The over-standard area was 1.608 million mu, with an over-standard rate of 67.8%, of which cadmium pollution was the most prominent, followed by arsenic, nickel, copper, mercury and chromium. The over-standard rate of other heavy metals is low.

The reporter learned that at present, the problem of remediation of land pollution has attracted attention, and the government, the public, and scientific and technological engineers have paid attention to this, and have launched some important projects in China, such as Beijing Coking Institute, Hangzhou Pesticide Plant, and the remediation of farmland polluted by heavy metals in Changsha, Zhuzhou and Xiangtan.

In addition, the Ministry of Environmental Protection has also issued five technical documents, including "Technical guidelines for site Environmental investigation", "Technical guidelines for site Environmental Monitoring", "Technical guidelines for risk Assessment of contaminated sites", "Technical guidelines for Land Restoration of contaminated sites" and "terminology of contaminated sites", to guide the investigation and evaluation of contaminated sites.

However, many experts reflect that, on the whole, the remediation of soil pollution in China is still facing many challenges, such as the serious lag in the formulation of laws and regulations on soil environmental protection, the lag and lack of soil environmental quality standards, the lack of pollution types and concentration limits, the unclear objectives of soil remediation, the lack of research and development and reserves of soil remediation technology, equipment and chemicals, and few successful cases. How to prevent and control the secondary pollution in the remediation process.

There is an urgent need for legislation, standards, technology and other measures.

Effectively promote the remediation of soil pollution

In view of the actual situation of soil pollution mentioned above, experts and scholars interviewed suggested that more measures should be taken to improve the effectiveness of soil pollution remediation.

First, it is suggested to strengthen the legislative work related to soil environmental protection. The state has incorporated the legislation on soil environmental protection and pollution prevention into the plan, and a great deal of work has been done in the early stage. It is proposed to speed up the pace of legislation, clarify the legal responsibilities and obligations of various departments, and standardize their production and life activities, so as to achieve the cooperation of all relevant departments. Each should perform its own duties and manage together, and gas, water, solid waste and soil pollution should be prevented and treated together. Improve soil fertility and prevent pollution to ensure the double safety of quantity and quality of edible agricultural products in our country.

Wei Fusheng suggested that we should formulate "Pesticide Management Law" and "Chemical Fertilizer Management Law" at the national level, learn from the advanced experience of Europe and the United States, strengthen the management of pesticide registration and re-registration, and implement supervision over the whole process of pesticide production, operation, and use. Strengthen the scientific and rational use of chemical fertilizer and improve the utilization rate of chemical fertilizer in the current season. With reference to the practice of the European Union, we should control the total amount of chemical fertilizer, reduce the application amount of nitrogen and phosphorus fertilizer, use more organic fertilizer, improve the effective utilization rate of fertilizer, and improve the soil fertility and the quality of agricultural products.

Second, drawing lessons from the experience of foreign "double indicators" and "classification standards", the government organized to study and revise and formulate soil environmental quality standards. To study and formulate the "total" and "soluble" double index standard system of soil pollution factors, so as to provide scientific basis for risk assessment and risk management of soil pollution. On the basis of "double index", the grading standard system is established according to the national conditions and local conditions, which provides a standard basis for the graded development and utilization of soil and the remediation and treatment of soil pollution.

Hu Qing, chairman of China Energy Saving Earth Environment Restoration Co., Ltd., believes that the soil remediation standard system, which is in line with China's reality and is operable, should include political system, management system, technical system, training system, and so on.

Third, strengthen the technological research and development and demonstration of land pollution remediation, standardize the market order, raise the threshold of technological access, improve corporate social responsibility, and compile successful cases for promotion every year.

Li Guanghe, a professor at the School of Environment at Tsinghua University, said that at present, there are outstanding technological weaknesses in promoting soil pollution remediation in China, which are often solved on a case-by-case basis and lack of innovative ideas. "it is necessary to train a high-level design and planning team for land pollution remediation projects." cultivate innovative and leading engineering thinking, and be able to put forward new ideas in green remediation and low-cost remediation. "