Soil is a very specific component of the biosphere as it is a natural geochemical sink for contaminants and acts as a natural buffer controlling the transport of chemical substances to the atmosphere, hydrosphere and lithosphere.
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It is being over exploited due to rapid growth in industrial development, intensive agriculture and other anthropogenic activities that have led to land degradation, environmental pollution and decline in crop productivity and hence causing a great concern to human health.
Sources of Soil Pollution
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Soil contamination results when hazardous substances are either spilled or buried directly in the soil. Prominent sources contributing to increasing load of soil contamination are mining, smelting, vehicle emissions, and indiscriminate use of agricultural chemicals and disposal of municipal and industrial sludge.
Once pollutants enter into the soil, their concentrations continuously increased and accumulate through food chain.
Type of pollutants
The different kinds of soil pollutants are:
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i) Pesticides
ii) Inorganic pollutants (Hg, As, Ni, Cd, Pb etc.)
iii) Radio nucleotides
iv) Organic wastes (detergents, borates, agricultural wastes, crop residues, sewage effluents)
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v) Air borne contaminants (gaseous emissions from industrial areas, burning fuels, smelting and mining)
Effects of soil pollution
i) Health effects
There is a very large set of health consequences from exposure of soil contaminants especially volatile compounds. Health hazards depend on pollutant type, pathway of attack and vulnerability of the exposed population.
ii) Ecosystem
The soil contaminants can alter metabolism of endemic microorganisms and arthropods resident in the soil environment, even at low concentrations and hence can affect primary food chain (in turn major consequences for predator or consumer species). Contaminants typically alter plant metabolism and reduce crop yield. This has given rise to soil erosion.
Control of soil pollution
The major concern of soil pollution is that there are many sensitive land uses where people are in direct contact with soil such as residence, parks, schools and playgrounds. Hence, it is necessary to cleanup or •remediates polluted soil. The principal remedial strategies are:
i) Aeration of soil at contaminated sites.
ii) Bioremediation, involving microbial digestion of certain organic chemicals, heavy metals and land farming, biostimulation and bioaugmentation of soil biota with flora.
iii) Extraction of groundwater or soil vapors with active electromechanically system (by using single extraction method or fractionation schemes).
iv) Excavate soil and remove it to a disposal site away from sensitive ecosystem contact.