Soil contagion or soil pollution as part of land degradation is instigated by the presence of xenobiotic human made chemicals or another alteration in the natural soil environment. it's usually caused by industrial activity, farming chemicals, or improper disposal of waste. The common chemicals involved are petroleum hydrocarbons, polynuclear fragrant hydrocarbons like naphthalene and benzo a pyrene, solvents, pesticides, lead, and other heavy metals. contagion is correlated with the degree of industrialization and intensity of chemical handling.
The concern over soil contagion stems mainly from health risks, from direct contact with the contaminated soil, vapors from the contaminants, and from secondary contagion of water supplies inside and fundamental the soil. Mapping of contaminated soil sites and the ensuing cleanup are time consuming and costly tasks, requiring broad amounts of geology, hydrology, chemistry, computer modeling expertise, and GIS in Environmental contagion, also as an appreciation of the history of industrial chemistry.
In North America and Western Europe the extent of contaminated land is best recognized, with many of countries in these regions having a legal framework to recognize and deal with this environmental problem. Developing countries tend to be less tightly regulated in spite of some of them having went through important industrialization.
The common chemicals involved are petroleum hydrocarbons, solvents, pesticides, lead, and other heavy metals.
In a wider sense, genetically changed plants GMP can count as a risk factor for soils, because of their possible to influence the soil fauna. Any activity that leads to other forms of soil degradation wearing away, compaction, etc. May indirectly worsen the contagion effects in that soil remediation becomes more tedious.
Historical deposition of coal ash used for residential, commercial, and industrial heating, also as for industrial processes like ore smelting, were a common supply of contagion in regions that were industrialized before about 1960. Coal naturally concentrates lead and zinc throughout its formation, also as other heavy metals to a lesser degree. When the coal is burned, most of these metals become concentrated in the ash the principal exemption being mercury. Coal ash and slag may contain enough lead to meet the criteria as a "characteristic hazardous waste", defined in the USA as containing more than five mg/l of extractable lead using the TCLP procedure. also to lead, coal ash usually holds variable but important concentrations of polynuclear fragrant hydrocarbons PAHs, e.G., benzo a anthracene, benzo b fluoranthene, benzo k fluoranthene, benzo a pyrene, indeno cd pyrene, phenanthrene, anthracene, and others. These PAHs are recognized human carcinogens and the satisfactory concentrations of them in soil are usually around one mg/kg. Coal ash and slag may be recognised by the presence of off white grains in soil, gray heterogeneous soil, or coal slag bubbly, vesicular pebble sized grains.
Treated sewage sludge, recognized in the business as biosolids, became controversial as a "fertilizer". As it's the byproduct of sewage treatment, it usually holds more contaminants like life forms, pesticides, and heavy metals than other soil.
In the European Union, the Urban Waste Water Treatment Directive lets sewage sludge to be covered onto land. The volume is projected to double to 185,000 tons of dry solids in 2005. This has good farming properties caused by the high nitrogen and phosphate content. In 1990/1991, 13 wet weight was covered onto 0.13 of the land, but, this is projected to rise 15 fold by 2005. Advocates say there's a have to control this so that pathogenic microorganisms don't get into water courses and to ensure that there's no buildup of heavy metals in the top soil.