Soil contamination


Contents:
What is soil pollution?
Sources of soil contamination
Effects of soil contamination
Protection and land reclamation



What is soil contamination?

Pollution of soil and ground are all chemicals, radioactive elements and microorganisms that are present in increased quantities in the soil.

The most common contaminants of soils and land comprise:


Sources of soil contamination

The greatest amount of contaminants leak into the soil and land with sewage, dust and solid and liquid waste generated by the industry. Most frequently they comprise heavy metals and salts. Mining generates enormous quantities of highly saline mine water. Many industrial plants (eg. steel works, cement plants, power plants, chemical industry centers) emits harmful gases and dust, which then, due to the deposition of air pollute the soil.
As a result of improper farming impurities resulting from the fertilizers used in excess penetrate the soil and land. Especially dangerous compounds derived from this branch of the economy are pesticides and other plant protection products. Any contamination of fertilizers are particularly dangerous for the environment. An example is the cadmium that is found in phosphate fertilizers.
The soils located near roads and highways are particularly polluted. They contain increased amounts of hazardous lead compounds and nitrogen oxides. As a result of salting the surface of the roads , soil and land in the vicinity of transport routes are heavily salted.
Significant amounts of harmful contaminants get into the soil along with municipal wastewater. They contain detergents and pathogens.



Effects of soil contamination

Harmful substances change soil pH significantly. Increased acidification or alkalinization of soils negatively affects the condition of microfauna and microflora of soil. As a result, the rate of decomposition of organic plant and animal residues and the formation of humus are reduced. The limited growth of nitric bacteria results in a reduction in the rate of nitrification (i.e. oxidation of NH3 to NO2- mainly by Nitrosomonas) and denitrification (i.e. reduction NO2- to NH3 or N2 molecule, performed mainly by Pseudomonas or Nitrocallus). The utility value of these soils decreases. Soils with changed pH become less fertile, which results in reduced quantity and quality of crops.
Acidification (reduced soil pH) may be affected also by so-called acid rain, which is a consequence of excessive atmospheric pollution. I have described them more specifically in section Effects of air pollution. Improper alkalinization (inreased soil pH) of the soil is caused by improper liming and dust pollution.
Nitrates are very dangerous for plants soil pollution. They significantly reduce plant resistance to diseases and pests. Plants from contaminated regions contain toxic substances. After eating, they can cause food poisoning in people.
Soil contamination can be deposited into the aquatic environment by leaching of harmful substances. Therefore, they may cause water pollution.



Protection and land reclamation

Pollution change the soil chemically, physically and biologically.
To prevent the total havoc of soils, we should begin to counteract the deterioration of the soil due to human activities. Soils that are devastated by human activity need to be reclaimed, i.e. their former biological function and utility value needs to be restored. Soil degradation can be limited by appropriate agrotechnical treatments. To restore the natural proportions of original mineral content in soils, it is necessary to supplement the deficiencies of the elements that are important for life. In order to prevent excessive acidification of the soil, the pH of the soil should be adjusted accordingly, e.g. by liming. Currently in Poland about 80% of the soil requires constant liming.
Soils completely destroyed by the industry can be reconstructed by covering them with a thick layer of caries or a layer of non-toxic waste. However, in case of soils that are heavily polluted with toxic substances, it is not enough to just cover the surface with a new layer. Such soils can be restored to their former utility only by means of costly neutralization with appropriate chemicals.
Also, proper location of roads and other communication routes relative to fertile soils can be a form of soil protection.

In Poland In 1995, all agricultural and forest land was protected by a law aimed at preventing the negative impact of cities and industrial activities.