Phytovolatilisation
Phytovolatilisation involves the uptake of contaminants by plant roots and their conversion to a gaseous state, with release into the atmosphere, driven by the evapotranspiration of plants Nature. The mechanism involves contaminants partitioning into air spaces within a plant and subsequently diffusing into ambient air ACS Publications. More specifically, plants absorb contaminants from soil, then convert these harmful substances into less hazardous volatile forms, releasing them into the surrounding environment through the leaf or foliage mechanism of transpiration RSC Publishing.
Selenium (Se) and Mercury (Hg) are often removed from soil through phytovolatilisation Wikipedia. For selenium, the metal can be volatilised through conversion into dimethylselenide Nature, whilst mercury, which exists in liquid state at room temperature with high tendency to vaporise, is absorbed as methylmercury and transformed into ionic mercury, then into less hazardous elemental form released as gas RSC Publishing. The technique also works for organic contaminants: volatile organic compounds (VOCs) are passively volatilised, and hybrid poplar trees have been used to volatilise trichloroethylene (TCE) by converting it to chlorinated acetates and CO₂ Nature.
Plants with high evapotranspiration rates are sought after for phytovolatilisation Nature, with poplar trees amongst the most successful plants for removing VOCs due to high transpiration rate Wikipedia. The Brassicaceae family, specifically Brassica juncea, effectively volatilises Se RSC Publishing. Whilst this method has the advantage of not requiring plant harvesting and removal RSC Publishing, there are important environmental considerations. The process does not result in complete elimination of contaminants from the environment; it merely transfers harmful substances from soil to atmosphere RSC Publishing. Toxic volatile components can contaminate the environment through air or even return to soil through precipitation ResearchGate, and regulatory concerns exist around pollutant volatilisation and potential air quality impacts.