Nitrate and phosphate removal potentials of three willow species and a bald cypress from eutrophic aquatic environment

This study was aimed at examining nitrate (NO₃) and phosphate (PO₄) removal potentials of rosegold pussy willow (Salix gracilistyla), giant pussy willow (Salix chaenomeloides), Korean willow (Salix koreensis), and bald cypress (Taxodium distichum) from eutrophic aquatic environment. These plants were replanted in rubber pots 35-cm high and 30-cm diameter without holes in the bottom. Water of different concentration levels in NO₃ (5, 10, 20 ppm) or PO₄ (0.5, 1, 2 ppm) was funneled into the pots, and the residence time of inflow was controlled ranging from 1 to 4 h. Nitrate abatement of 58.9% was observed in the giant pussy willow pots with 20 ppm concentration and 4 h residence. The rosegold pussy willow pots showed the highest PO₄ removal at 20.2% at 0.5 ppm concentration and 4 h residence. Removal potentials of NO₃ and PO₄ were also investigated on the supposition that the polluted water would reside in wetlands or treatment facilities for longer than 5 days. Except that the residence time of inflow ranged from 5 to 20 days, the same experimental conditions were kept. The percentage of NO₃ removal in the rosegold pussy willow pots was higher than in those of the other two willow species, and bald cypress showed the lowest NO₃ abatement. Highest PO₄ removal was observed in giant pussy willow pots and lowest in rosegold pussy willow pots.