Soil contamination (soil pollution)
  Soil contamination   or   soil pollution   as part of   land degradation   is caused by the presence of   xenobiotics   (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of   waste . The most common chemicals involved are   petroleum   hydrocarbons ,   polynuclear aromatic hydrocarbons   (such as naphthalene and   benzo(a)pyrene ),   solvents , pesticides,   lead , and other   heavy metals . Contamination is correlated with the degree of   industrialization   and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapours from the contaminants, or from secondary contamination of water supplies within and underlying the soil.   Mapping of contaminated soil sites and the resu...