Preface Soil is a country's most important natural resources.It is the material basis of agricultural development, if there is no soil ,there would be no agriculture, no survival of the people’s food and clothing and other basic raw materials. Once the soil suffer from pollution, especially heavy metal pollution, it is difficult to repair Heavy metal pollution is one of the most damaging environmental problems and the most widely in area tody. It is not only reduces the soil fertility and crop yields and quality, and the deterioration of the environment, and through the food chain to threaten human life and health
What is heavy metal pollution of soil 1.What is heavy metal ？ Heavy metal refers to the proportion of heavy metal more than 4 or 5,about 45 species,such as copper,lead,zinc,iron,cobalt,nickel,vanadium, niobium,tantalum,titanium,manganese,cadmium, mercury,tungsten,molybdenum,gold,silver and so on. What we often say that heavy metal pollution is the increase of heavy metals in the environment, which outside the normal range, and leading to the deterioration of environmental quality caused by human activities.
Heavy metal pollution of soil Heavy metal pollution due to waste excessive deposition of heavy metals in the soil caused by soil pollution. Heavy metal polluted soils include mercury, cadmium, lead, chromium and arsenic and other metalloid elements of significant toxicity, as well as certain toxicity of zinc, copper, nickel and other elements. They mainly from agricultural chemicals, waste water, sludge and atmospheric deposition, such as mercury mainly from the mercury-containing waste ,and cadmium, lead pollution from car exhaust emissions and smelting settlement, and a large number of arsenic were used as insecticides, fungicides, rodenticides and herbicides. Excessive heavy metals can cause plant physiological disorders and nutritional disorders. Cadmium, mercury and other elements in the crop seed in the high enrichment factor, even over food hygiene standards,it does not affect crop growth, development and production, In addition to mercury, arsenic can be reduced and inhibited soil nitrification, ammonification bacteria activities, and impact of nitrogen supply.Mobility of heavy metal pollutants in the soil is very small and difficult to filter with water washout, and not for microbial degradation.There is potentially lethal to human body through the food chain, so particular attention shoud be made to prevent heavy metals on soil pollution.
Soil Heavy Metal Pollution Soil is one of the major natural resources of human life, and an important part of the human environment.With the increased species of industrial, urban pollution and agricultural chemicals , the increasing number of heavy metal pollution is worsening, the current world average of about 1.5 thousand tons per year emissions of Hg, Cu 3.4 million tons, Pb 5 million tons, Mn15 million tons, Ni 1 million tons.According to the Ministry of Agriculture of the National Sewage Irrigation survey, about 1.4 million hectares of waste water irrigation in heavy metal pollution of the land area being accounted for 64.8% of the sewage irrigation area, which accounted for 46.7% of light pollution, accounting for 9.7 % of moderate pollution, and8.4% serious pollution.
Characteristics of Heavy Metal Pollution The main features of heavy metal pollution: pollution of a wide range of long duration, pollution hidden and can not be biodegradable, and may continue through the food chain accumulation in vivo, and even more can be transformed into toxic methyl compounds in the food chain toxicity of certain organisms, or eventually accumulate in the body which is hazardous to health
The hazards of heavy metal pollution Soil pollution makes more intense of the already intense shortage of land resources Soil pollution brings great threat to the health of the people Soil pollution has brought great negative impact to the agricultural development Soil pollution is also the important reasons of causing other environmental pollution Pollutants in soil pollution also has the mobility and retention,which is possible to create new land contamination Soil pollution seriously endangers the interests of future generations and goes against to the sustainable development of rural economy
Control method and characteristics Control method and characteristics: including project management, biological control, chemical management and agricultural management methods. Engineering control effect completely, stable, but the implementation of complex, high cost of treatment, can lead to declining soil fertility; biological control implementation simple, low investment and little damage to the environment, but management is not satisfied; chemical treatment effects and costs are moderate, but easy re-activation; agricultural management methods and easy to operate, low cost, but the cycle is long, the effect is not significant
Agro-ecological restoration Agro-ecological restoration includes two aspects ： The first is agricultural rehabilitation measures.Including changes in farming systems, adjustment of crop varieties, planting the plants do not enter the food chain, choose to reduce heavy metal pollution of soil fertilizer, or increase the facilities enough to get a fixed metal organic fertilizer and other measures to reduce heavy metal pollution.The second is ecological restoration.By adjusting such as soil moisture, soil nutrients, soil ph values and soil redox conditions and temperature, humidity and other ecological factors, to achieve the environmental media in which the regulation of pollutants.In our country many studies do in this area , and have achieved some results. However, remediation of contaminated soil using the technology cycle is long, and the effect is not significant.