Phytoremediation and phytomining: using plants to remediate contaminated or mineralized environments

One type of harsh environment for plants is metal-and metalloid-contaminated or mineralized soils: these exist in most countries due to geological formations or to a history of mining and/or smelting. Depending on soil pH and fertility, metal-rich soils may be barren and eroding into wider areas. Some elements present risk to humans, wildlife, livestock, plants, or soil organisms and require remediation. The engineering approach of removing the contaminated soil is extremely expensive. Thus, alternative methods for in situ remediation of element-rich soils have been developed by the agricultural sciences. These methods include phytoextraction (growing plants which accumulate high concentrations of an element in shoots for removal from the field) and phytostabilization (adding soil amendments which convert soil elements into forms with much lower phytoavailability and bioavailability so they no longer pose a risk to the environment). Phytomining is a variant of phytoextraction in which the element accumulated in plant shoots has enough value to support farming a hyperaccumulator crop to produce a commercial bio-ore. This chapter reviews these valuable phytotechnologies which have been developed in the last few decades to reduce the costs of alleviating environmental risks of contaminated soils.