By Wu Ping & Gu Shuzhong, Research Team on "Policies of Comprehensive Prevention and Treatment for Soil Pollution", Research Institute of Resources and Environment Policies of DRC Research Report, No.234, 2013 (Total 4483)

I. The General Picture of Soil Pollution in China Looks Blue and Serious Pollution Can Be Found in Some Localities

1. The general situation of soil pollution in China is not optimistic

The southern region of China is exposed to higher ecological risks than the northern part due to soil pollution. In some places of northern China, such as Inner Mongolia and areas along the Great Wall, Loess Plateau, Gansu and Xinjiang area and northeast region, the agricultural soil environment is favorable with sound development for grain production. Due to concentrated non-ferrous metal mines and high content of background heavy metal in soil, the soil in southwestern carbonate rock areas and the central and southern China contains over standard heavy metal. Serious soil pollution can be easily found in large enterprises with high pollution, contaminated areas abandoned by industrial companies, waste yards of different kinds, large mining areas and polluted industrial parks.

2. Severely hit by the soil pollution, large areas of arable land suffer from combination of organic and inorganic pollutions and their acceptable and self-purification capacity has almost exhausted or even gone beyond.

The soil is mainly contaminated by inorganic pollutants, and organic pollutants while the combined pollution takes only a small part. Among inorganic pollutants, cadmium is a major one; and among organic pollutants, DDT constitutes the lion's share. 3. Large and medium-sized cities suffer from mercury, cadmium, selenium, lead, chrome, arsenic, nickel, antimony and zinc soil pollution as well as severe combined pollution, Attention should be paid to their ecological risks.

Relocation of polluting companies from urban industrial areas, irrational piling of residues in mining areas and relevant issues have caused severe soil pollution. The mercury and cadmium pollution has constituted medium-level pollution.

It is noteworthy that China's soil pollution begins to spread from industry to agriculture, from urban to rural areas, from the surface to the underground, from the upstream to the downstream, from water and soil pollution to the food chain. Pollution accumulation leads to frequent environmental incidents. It is urgent to intensify the prevention and treatment of soil pollution.

II. Soil Pollution Attributed to Natural Reasons and Human Activities

1. Natural reasons

The enrichment and dilution of elements in soil is closely related with many factors such as the chemical composition of the soil parent material, climate conditions and topography. The heavy metal distribution in soil depends of the geological background and soil forming weathering. The high background value of chemical elements significantly affects the soil quality and constitutes a major reason for the over-standard content of heavy metal in southwestern, central and southern China.

2. High heavy metal content in large and medium-sized cities and areas with developed industry and mining industry attributable to emissions of waste gas, waste water and waste residuals from ore smelting, coal combustion and other activities

Outdoor piling and disposal of industrial residuals severely pollutes soil in the piling area. Farm land in many places is irrigated with water from polluted river or foul water drained directly from factories and thus gets polluted. Waste gas and dust generated from industrial production fall into soil after atmospheric fallout and rainfall and cause pollution after years' accumulation. For example, atmospheric fallout brings 13.8g/hectare of cadmium to the soil each year in Changzhutan area in Hunan province, accounting for 86.8% of all cadmium imported to the soil.

3. Soil pollution due to over use of pesticides and fertilizer for a long time and non-point agricultural pollution caused by foul water irrigation

Pesticides are the major organic pollutant directly used in soil and most of them are absorbed by and remain in the soil. BHC, DDT and other pesticides remaining in the soil for a long time can concentrate in the organism and be transmitted to human body through the food chain. Fodders for livestock and poultry contain additives like copper, zinc and arsenic. Over 41 million tons of chemical fertilizers such as nitrogen and phosphate have been used each year in China, damaging the soil structure, hardening the soil, leading to farmland soil degradation and affecting the yield and quality of agricultural crops. In China, more than 3.3 million hm2 of farmland is irrigated by foul water, including domestic and industrial sewage which is not treated or below the standard for discharge and contains poisonous and harmful substances like heavy metal, phenol and cyanide. 4. Soil pollution by solid waste

Industrial solid waste and urban garbage directly disposed to soil can radiate and funnel to surrounding soil under the effects of sun baking, rainfall and water wash. Random piling and landfill not only occupies certain patches of land but also harm the soil's decay capacity, change its property and structure and severely pollute surrounding soil and underground water. Besides, radioactive substances generated from uranium and thorium mining, uranium enrichment, disposal of nuclear waste, nuclear explosion, nuclear experiment, thermal power plant and phosphate mining and processing can also pollute the soil.

III. Serious Consequences Induced by Soil Pollution

Soil pollution is a major environmental problem of the global concern, as it not only affects the soil quality and productivity, but also harms food safety, people's healthy and ecological security.

1. Affecting the yield and quality of agricultural crops and threatening food safety

The use of a large amount of chemical fertilizers and pesticides can decrease the content of organic substances in the soil, harden the soil and thus reduce the yield and quality of agricultural products. Soil pollution, especially heavy metal pollution and lasting organic pollution, can cause food safety issues through absorption by agricultural crops, enrichment or biomagnifications in the food chain. In some places in China, grains always contain over-standard heavy metal content.

2. Severe harm to people's health

Pollutants in soil can accumulate in plants and concentrate in the animal body and finally get into the human body through the food chain. In particular, heavy metal can accumulate in some human organs and cause cancer, deformity and mutation, as it can be hardly discovered with lasting and irreversible characters. In 1950s and 1960s, the heavy metal was responsible for many shocking environment incidents, such as the "itai-itai" disease in Toyama, Japan caused by "cadmium rice" and "Minamata disease" in Kumamoto prefecture in Japan due to mercury contamination. In recent years, many pollution incidents broke out such as cadmium rice, blood lead, chromic slag and arsenic poisoning, incidence rate of malignant tumors increased year by year, and "weird diseases" became more frequent. All these can be attributed to the pollution of environment including soil to a large degree.

3. Damage to eco-environment

Soil pollution not only severely harms the soil quality and productivity, but also causes the pollution of surface and underground water, degradation of the atmospheric environment and deterioration of the eco-system as well as many other secondary eco-environment problems and directly threatens ecological security.

IV. Current Issues Facing Soil Pollution Prevention and Treatment

1. Absence of relevant laws and regulations

China has no special laws and regulations concerning soil protection at present. The legal system for soil pollution prevention and treatment is lagging far behind that for water and air pollution. There are only a few provisions about soil protection in different laws and are hard for implementation due to lack of details. Take the Soil Environment Quality Standard for example. The regulation provides only a few pollutant indicators with few indicators concerning organic pollutants. It takes the aggregate of the country as the basis, without taking into account the soil types and the complexity of the soil parent material. It has neither criteria for evaluating the soil conditions in residence and industrial construction projects nor benchmarks for evaluating risks of land for residence, farming and mining.

2. Low monitoring level and inaccurate investigation

Monitoring instruments and staff are deficient in some places, and monitoring stations are insufficient in major areas such as basic farmland and concentrated drinking water sources. Problems also include the small number of monitoring projects, sluggish circulation of monitoring data, and inadequate professional staff and funds. At present, the sampling density of soil investigation conducted by the Ministry of Land and Resources is 1 point/km2, samples from each 4km2 are combined and analyzed, and encrypted sampling is only done for some places. The soil heavy metal data roughly reflect the general status of China’s soil pollution, but can hardly specify the distribution of heavy metal pollution and thus cannot clarify the accurate intensity of soil pollution in each area.

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The article was published in China Development Review, No. 1, 2014.

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