Toxic heavy metal

===Environment===

===Environment===

Soils contaminated by heavy metals can be remediated by one or more of the following technologies: isolation; immobilization; toxicity reduction; physical separation; or extraction. ''Isolation'' involves the use of caps, membranes or below-ground barriers in an attempt to quarantine the contaminated soil. ''Immobilization'' aims to alter the properties of the soil so as to hinder the mobility of the heavy contaminants. ''Toxicity reduction'' attempts to oxidise or reduce the toxic heavy metal ions, via chemical or [[Phytoremediation|biological means]] into less toxic or mobile forms. ''Physical separation'' involves the removal of the contaminated soil and the separation of the metal contaminants by mechanical means. ''Extraction'' is an on or off-site process that uses chemicals, high-temperature volatization, or electrolysis to extract contaminants from soils. The process or processes used will vary according to contaminant and the characteristics of the site.{{sfn|Evanko|Dzombak|1997|p=1, 14–40}}

Soils contaminated by heavy metals can be remediated by one or more of the following technologies: isolation; immobilization; toxicity reduction; physical separation; or extraction. ''Isolation'' involves the use of caps, membranes or below-ground barriers in an attempt to quarantine the contaminated soil. ''Immobilization'' aims to alter the properties of the soil so as to hinder the mobility of the heavy contaminants. ''Toxicity reduction'' attempts to oxidise or reduce the toxic heavy metal ions, via chemical or [[Phytoremediation|biological means]] into less toxic or mobile forms. ''Physical separation'' involves the removal of the contaminated soil and the separation of the metal contaminants by mechanical means. ''Extraction'' is an on or off-site process that uses chemicals, high-temperature volatization, or electrolysis to extract contaminants from soils. The process or processes used will vary according to contaminant and the characteristics of the site.{{sfn|Evanko|Dzombak|1997|p=1, 14–40}}

Although heavy metals are naturally found all over the earth crust, most environmental contamination and human exposure comes from human caused activities such as mining which contaminates air quality, smelting and industrial production that poisons our air and water, and contamination of soil through agricultural equipment. Some natural phenomena are weathering and volcanic eruption that have been reported to significantly contribute to heavy metal pollution.{{Cite journal |last=Tchounwou |first=Paul B. |last2=Yedjou |first2=Clement G. |last3=Patlolla |first3=Anita K. |last4=Sutton |first4=Dwayne J. |date=2012 |title=Heavy metal toxicity and the environment |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC4144270/ |journal=Experientia Supplementum (2012) |volume=101 |pages=133–164 |doi=10.1007/978-3-7643-8340-4_6 |issn=1664-431X |pmc=4144270 |pmid=22945569}}

== Benefits ==

== Benefits ==