BIOMASS AND POLLUTANT UPTAKE OF SELECTED PLANT SPECIES IN CONSTRUCTED FLOATING WETLANDS

Abstract

Constructed Floating Wetlands (CFW) is an innovative to control the pol- lution in urban lakes. A study was conducted to assess biomass production and pol- lutant uptake by Canna iridiflora and Cyperus alternifolius in CFWs in Bogambara Lake, Kandy, Sri Lanka. Tillers of both plants (20 cm height) were potted in floating PVC frame in the lake. Coconut coir was used as the media for each pot. The refer- ence experiment was conducted by maintaining terrestrial conditions nearby the lake. Reference plants were arranged in polyethylene bags and kept to represent the terres- trial condition and watered using lake water. In both experiments, plant samples were collected weekly intervals up to 8 weeks by uprooting. The height, fresh & dry weight of shoots and roots were measured. Total nitrogen (TN), and total phosphorous (TP) contents were also measured in shoot and root samples. The data were analyzed using R software. Results indicated that the biomass of both shoots and roots of Canna iridiflora were significantly higher (P<0.05) than Cyperus alternifolius in both CFWs and reference. The shoot growth was higher on CFWs, and root growth was higher on terrestrial conditions in both plants. The TN and TP contents in shoots of both plants were higher than the roots for both tested conditions. The uptakes of N (23.28 mg plant-1) and P (31.09 mg plant-1) were higher in Canna iridiflora compared to N (14.91 mg plant-1), P (7.89 mg plant-1) uptake by Cyperus alternifolius, in CFW over the terrestrial conditions. It can be concluded that growing Canna iridiflora in CFW is one of the best solutions to mitigate the pollution of polluted lakes.