PERSPECTIVES OF WATER QUALITY IMPROVEMENT BY AQUATIC MACROPHYTES AS NUTRIENT SINK IN THE LAKE PALDANGHO, KOREA

概要

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Improvement of water quality by aquatic macrophytes was studied at the Lake Paldangho, a reservoir supplying the service water for 15 million inhabitants in the Capital of Korea. Annual production of aboveground of emergent plants having 1800 g DW/m² for Typha angustata and 1700g DW/m² for Zizania latifolia, are 15- to 30-folds as large as those of submersed plants having 110 g DW/m² for Ceratophyllum demersum and 60 g DW/m² for Hydrilla verticillata. Although concentrations of nitrogen and phosphorus in mg per g dry matter of emergent plants are small as a half of those of submersed ones, standing nutrients in g per m² of the former are 8- to 9-folds as large as that of the latter because of large production. Annual return of nutrients from the litters are also more in emergent plants than in submersed one. In the whole Lake the uptake amounts by macrophyte (sink) are 30.3 ton of nitrogen and 4.9 ton of phosphorus, and the return amounts from the litter (source) are 18.5 ton of nitrogen and 4.3 ton of phosphorus. Difference between the sink and the source, 11.8 ton for nitrogen and 0.6 ton for phosphorus, will remain in sediment of littoral zone. If aboveground of macrohytes are weeded out on time occurring the maximum production nutrients remaining will be reduced. To increase the annual production, repetitive harvesting of Zizania latifolia is effective.
信州大学理学部の論文