Amount of organic carbon and its fractionation dissolved from Nymphoides peltata and Phragmites australis

This study aims to clarify the possible effects of organic matter originating from asaza (Nymphoides peltata) and reed (Phragmites australis) on water quality. Leaves and petioles of asaza and leaves and stems of reed are used. The experiment was carried out for a period of 100 days, and controlled at a temperature of 20°C in dark. The amount of dissolved organic carbon (DOC) and dissolved oxygen was measured periodically during the course of the experiment. Two main sources of water were used for the experiment, Milli-Q water and water taken from Lake Teganuma. The results of fractionation is used to evaluate the composition of DOC. DOC supplied per plant carbon after 100 days in Milli-Q and lake water was 43.4±1.54 mg C g C and 43.7±1.51 mg C g C for leaf and stem of reed. Those of the petiole of asaza was 17.7±2.76 mg C g C・73.0±1.89 mg C g C, the latter was more than four times larger than former. The leaf of asaza supplied DOC with 163±5.4 mg C g C in Milli-Q water and 267 ± 7.5 mg C g C in lake water. Considering the lake water exposed condition, it was observed that asaza leaves displayed 6 times more DOC than the reeds; for a period of 100 days, and asaza petiole displayed nearly double of the reeds. Comparing the samples in terms of their DOC fractions revealed distinct differences between the samples. For reeds, it was determined that both the hydrophilic and hydrophobic acid fractions together make up 96.4% of total DOC. For the case of asaza, in terms of the DOC fraction, the petiole consisted mainly of hydrophobic acid, about 48.4% of total DOC, while the leaves consisted mainly of the hydrophilic fraction having a value of 46.2% total DOC. Keyword: purification of water quality, COD, refractory organic matter, trihalomethanes formation potential 摘 要 湖岸もしくは湖岸近傍で前年に成長・枯死したヨシやアサザから供給される溶存有機物と酸素消費が 湖沼水質に与える影響を見積もるため,20°C・100 日間・暗条件での分解・溶出実験を Milli-Q 水と手賀 沼湖水を用いて行った。また溶存有機物の分画も行った。100 日後に得られた濃度から計算した植物体