phytovolatilization

Phytovolatilization is a process within phytoremediation in which plants take up contaminants from soil or water and release them to the atmosphere in volatile forms. In many cases, metals or metalloids are converted inside plant tissues to volatile species and then emitted through stomata or plant surfaces. The approach is mainly studied for elements such as mercury, selenium, and arsenic, but can involve organic contaminants under certain conditions.

Mechanisms include reduction of metal ions to elemental or volatile forms (e.g., Hg2+ to Hg0), methylation or demethylation steps that yield volatile organometallics (such as dimethyl selenide from selenium compounds), and transport from roots to shoots before emission. The overall efficiency depends on plant species, contaminant speciation, environmental conditions, and plant metabolic capacity.

Plant systems studied include woody species such as willow (Salix) and poplar (Populus) for mercury volatilization, and herbaceous crops such as Brassica juncea for uptake and volatilization of several elements. Selenium hyperaccumulator plants such as Astragalus and Stanleya have been used to demonstrate selenium volatilization. Measurement typically relies on enclosure chambers around the canopy and analysis of emitted gases by gas chromatography–mass spectrometry or related techniques.

Phytovolatilization can reduce contaminant concentrations in soil or water but transfers pollution to the atmosphere, raising questions about air quality and regional transport. It is generally most useful as part of a broader remediation strategy rather than a stand-alone solution, and its effectiveness is limited by climate, plant growth, and contaminant load.

Research continues to identify plant traits that enhance volatilization, to quantify fluxes in field settings, and to assess environmental trade-offs and safety considerations.