Phytofiltration of arsenic by aquatic moss (Warnstorfia fluitans)

This work investigates whether aquatic moss (Warnstorfia fluitans) originating from an arsenic (As)-contaminated wetland close to a mine tailings impoundment may be used for phytofiltration of As. The aim was to elucidate the capacity of W. fluitans to remove As from arsenite and arsenate contaminated water, how nutrients affect the As uptake and the proportion of As adsorption and absorption by the moss plant, which consists of dead and living parts. Arsenic removal from 0, 1, or 10% Hoagland nutrient solution containing 0-100 μM arsenate was followed over 192 h, and the total As in aquatic moss after treatment was analysed. The uptake and speciation of As in moss cultivated in water containing 10 μM arsenate or arsenite were examined as As uptake in living (absorption + adsorption) and dead (adsorption) plant parts. Results indicated that W. fluitans removed up to 82% of As from the water within one hour when 1 μM arsenate was added in the absence of nutrients. The removal time increased with greater nutrient and As concentrations. Up to 100 μM As had no toxic effect on the plant biomass. Both arsenite and arsenate were removed from the solution to similar extents and, independent of the As species added, more arsenate than arsenite was found in the plant. Of the As taken up, over 90% was firmly bound to the tissue, a possible mechanism for resisting high As concentrations. Arsenic was both absorbed and adsorbed by the moss, and twice as much As was found in living parts as in dead moss tissue. This study revealed that W. fluitans has potential to serve as a phytofilter for removing As from As-contaminated water without displaying any toxic effects of the metalloid.