东太湖茭黄水发生原因与防治对策探讨

YELLOW WATER" IN EAST TAIHU LAKE CAUSED BY ZIZANIA LATIFOLIA AND ITS PREVENTION

东太湖茭草分布面积35．47km2，年生长量（鲜重）127600t，收割利用率9．7％，残留量高达115204t，折合单位湖面干物质残留量1774g／m2,这些茭草残体遇高温时迅速腐烂分解，向湖水中释放大量有机污染物质和氮、磷等生物元素，引起水质腐败．腐烂后的茭草残骸沉积在湖底，加速了湖泊的淤积变浅．收割利用茭草可在一定程度上减轻茭黄水，剔除茭草、以沉水植物取而代之，则是根治茭黄水的有效途径．

In the period from 1992 to 1993. field surveys were carried out in East Taihu Lake on the distribution. productivity and harvest of emerged macrophyte Zizania latifolia. At the same time,the sediment in the distributing zone of the plant was sampled at 15 points. the depth of saft mud was measured and the sediment samples of differet depth were analyzed on the contents of nitrogen, phosphorous and organic carbon. Experimental study was proceeded to reveal the decaying process of the plant material and its pollution to the water.About 35. 47km2 of the lake surface of East Taihu Lake was covered by an emerged plant species Zizania latifolia. Its net productivity was 127 600 t/a(fresh weight). Only 9. 7% of the product was harvested and 115 204t of the product was left in the lake. It added 1774g dry plant materiel to every square meter of lake bottom. In the beginning of next summer when the water temperature went up, the remained plant materiel fell into decay and caused serious secondary-pollution to the lake water, forming 'Yellow Water'. After one year's decaying. large amount of the indecomposable vascular skeleton of Zizania latifolia was left and became the component of the sediment.Intensive harvest of Zizania latifolia may, to a certain extent, resist 'Yellow Water' in the lake, but the best measure is to replace it with submerged plant.