西湖湖水碱化对水体理化性质的影响

Effects of Alkalinization on Physical and Chemical Properties of Water in the West Lake

通过对西湖流域内土壤、入湖径流及西湖沉积物、间隙水、湖水中有关指标项目的采集测定,研究了西湖湖水碱化的原因及对水体理化性质的影响。结果表明,西湖沉积物中碳酸钙含量18.6%(10.7%～26.3%)高于西湖流域土壤的碳酸钙含量6.89%(6.38%～7.65%)。西湖湖水长年处于弱碱性状态(pH为8.0～9.6),与藻类活动和补给水向上覆水补充碳酸氢盐直接相关。湖水的碱化延长了再悬浮沉积物在水中的滞留时间,增加了湖水对可见光的吸收,降低了湖水的透明度,从而降低了西湖作为风景旅游湖泊的价值。藻类大量繁殖季节,湖水的pH值高达9.6。湖水碱化促进水层中颗粒磷解吸成为水溶性磷。

Soil in the West Lake basin contains high content of calcium of carbonate and bicarbonate. In addition, erosion and leaching of soil around the lake make enormous amount of carbonate and bicarbonate enter the West Lake every year, resulting in Alkalinization of water in the West Lake. pH values of water varies from 8.0 to 9.6. Furthermore, the alkalinized water makes phosphorus to be released and water color change. In basic solution, resuspended sediment may stay longer than that in neutral solution. Alkalinized water increases colored organic matter in the water from the sediment and reduces transparency of the water. Alkalinized water makes the volume of sediment larger. High pH of lake water makes phosphorus to be desorbed from suspended particle.