Plant Traits for Phytoremediation in the Tropics

Abstract

Water is a limited and valuable resource. Singapore has four national sources of water supply, one of which is natural precipitation. Pollutants collected in stormwater runoff are deposited into drainage systems and reservoirs. Major nutrient pollutants found in local stormwater runoff include nitrate and phosphate, which may cause eutrophication. Bioretention systems are efficient in removing these pollutants in the presence of plants. This paper discusses plant traits that can enhance the phytoremediation of nutrient pollutants in stormwater runoff for application in bioretention systems. The plant species studied showed variations in chlorophyll florescence, leaf greenness, biomass production, and nitrate and phosphate removal. In general, dry biomass was moderately correlated to nitrate and phosphate removal (r = 0.339–0.501). Root, leaf, and total dry biomass of the native tree species showed a moderate to strong correlation with nitrate removal (r = 0.811, 0.657, and 0.727, respectively). Leaf dry biomass of fast-growing plants also showed a moderate to strong relationship with the removal of both pollutants (r = 0.707 and 0.609, respectively). Root dry biomass of slow-growing plants showed a strong relationship with phosphate removal (r = 0.707), but the correlation was weaker for nitrate removal (r = 0.557). These results are valuable for choosing plants for application in bioretention systems. Keywords: Nitrogen, Phosphorus, Plant traits, Bioretention system, Stormwater, Tropical plant, Nutrient pollutant, Native plants