Polynuclear aromatic hydrocarbons (PAHs) differentially influence growth of various emergent wetland species

The growth of emergent wetland plants may be influenced by toxic organic pollutants, which would influence the extent of phytoremediation when used in constructed wetlands. A series of glasshouse experiments were conducted to investigate the influence of polynuclear aromatic hydrocarbons (PAHs) on the growth of various emergent wetland species. The response of species to PAHs varied significantly. A significant interaction (species × PAH treatment) was observed for relative growth rates (RGRs) of Baumea juncea, Baumea articulata, Schoenoplectus validus and Juncus subsecundus in hydroponics with naphthalene, and of B. juncea and J. subsecundus in soils freshly spiked with phenanthrene and pyrene. In hydroponics, biomass of B. articulata significantly increased in the treatments with relatively low addition of naphthalene, whereas that of S. validus significantly increased with all naphthalene additions. In both hydroponics and soils, the growth of B. juncea increased with the PAH (phenanthrene and pyrene) additions, whereas that of J. subsecundus decreased in the treatments with relatively high concentrations of PAHs. The removal of PAHs from soil was not affected significantly by J. subsecundus after 70 days of growth and B. juncea after 150 days of growth. The growth of J. subsecundus was slightly (but not significantly) influenced by the PAH residues in soil. The effect of PAHs on wetland plant growth could be species-specific regardless of PAH types and media. The response of species to PAHs needs to be taken into account when selecting species for wetlands constructed for phytoremediation.