Soil pollution or soil erosion as a portion of land degradation is mainly caused by the presence of soil toxins (xenobiotic) or other unnatural alteration in the soil environment. These factors are either overlooked or intentionally passed off as due to natural process. In fact, there are many cases of pollution being attributed to natural processes that can be easily corrected. Nonetheless, contaminated land continues to occupy an inordinate amount of area that can be utilized for farming.
The extent of global soil pollution is becoming alarming because even small amounts of toxic wastes can lead to fatal diseases like cancer and birth defects. One of the most serious environmental problems facing us today is the proliferation of waste accumulation in urban centers due to poor design of housing, lack of open spaces and inadequate waste management. Heavy metals, which comprise a majority of the pollutants in the soil, are the result of a number of human activities including manufacturing and domestic consumption. Soil pollution resulting from the above-mentioned sources has adverse effects on the environment as a whole, and contributes to the global burden of disease, premature deaths and pollution-induced stress.
Soil pollution is one of the major causes of groundwater pollution and one of the major environmental problems faced by humanity. It can either be brought about by human activities or by natural causes. Natural causes of soil pollution include physical pollution caused by humans such as runoff from landfills, erosion and soil subsidence due to building and other constructions, geochemical pollution caused by external factors such as coal and petroleum products, and naturally occurring pollution caused by atmospheric constituents. According to estimates, around 70% of the fresh water in the world is contaminated with soil.
Human activities are considered the primary causes of soil pollution primarily because of their enormous impact on the nature and quality of the soil. Emptying lakes, rivers, and streams, burning of vegetation and animal waste results in contamination of the soil. Human activities such as clearing of forests, construction of houses and industries, and waste disposal resulting in solid waste are the major causes for the contamination of the land and water. Industrial waste, which includes toxic wastes from manufacture of finished goods and chemical products, poses as a serious threat to the environment due to its high toxic load and the effect it has on the ecosystem.
The process of degrading the soil can result in two main consequences. One is the blocking of nutrients and water needed by plants, and the other is direct damage to the ecosystems. The soil pollution caused due to these processes can seriously affect the productivity of the agricultural land. These processes include alteration of the structure of the soil, increase in the rate of organic matter decomposition, and increase in the amount of heavy metals in the soil. These processes can significantly degrade the fertility of the soil and lead to the blockage of essential nutrients.
Chemical contaminants in soil can also lead to soil pollution due to their ability to form synthetic materials when they grow in the soil. This process produces nitrates and nitrites in large quantities. These pollutants are capable of causing air-born particles that trigger release of toxic chemicals in the air. The toxic chemicals released into the air can aggravate asthma and allergies, and also cause skin and mucous membrane disorders. In case of heavy concentrations, these chemicals may even prove to be carcinogenic.
Besides these factors, soil contamination by various human health hazards can also be due to other factors such as pesticides, genetically modified food, and animal wastes. Pollution by these pollutants causes many diseases such as respiratory and gastrointestinal tract infection, infertility, and chronic obstructive pulmonary disease. These pollutants also adversely affect the human health by causing cancer, nervous system disorders, and birth defects. There is also a high risk of exposure to these pollutants during drinking water, which is used for most domestic purposes.
Soil pollution by various human health hazards can be reduced through effective management practices aimed at reducing the amount of input of inputs such as chemicals and fertilizers, and increasing the efficiency in converting these inputs to useful outputs. Strategies for reducing pollution of soils include construction of properly drained and treated sewage plants, use of organic matter for agricultural and landscape plants, and use of natural fertilizers. Another option is the removal of these contaminants through effective construction of soil and water systems, use of biological aerated systems for controlling the spread of contaminants, and protection of the soils from nutrient loss.