In addition to agricultural pesticides and animal waste, heavy metals are common sources of soil pollution. Industrial mining activities, road runoff from cars and sewage release toxic metals into nearby forests, vegetation and stream beds. Likewise, these metals can affect groundwater supplies and contribute to air pollution by emitting gaseous compounds into the atmosphere.
Some of the most common heavy metals found in polluted soil include zinc, copper, mercury, lead, iron, cadmium, aluminum, nickel and chromium.
Soils polluted by heavy metals threaten agriculture and other food sources for human populations. For example, heavy metals can seep into the soil and surrounding plants, increasing toxicity levels within the food chain. Other negative effects include poor vegetation growth and lower plant resistance against forest pests.
Common methods for removing contaminated soil include incineration or transferring it to landfills. Other decontamination techniques include washing the soil using scrubbing and wet-screening methods. Chemicals such as hydrochloric, nitric, citric and phosphoric acids are also used to remove toxic metals from soil.
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