天山天池水体季节性分层特征

Seasonal characteristics of thermal stratification in Lake Tianchi of Tianshan Mountains

于2014年6—10月，对高山深水湖泊天山天池水温、电导率、溶解氧、pH值、叶绿素a浓度和蓝绿藻细胞密度进行垂直剖面的连续监测，通过对其季节动态和垂直分层结构的分析，探讨天池水体季节性分层特征．天池出现明显水温分层的时间短（6—9月），夏季温跃层变化范围为2～18m，而秋季温跃层不断下移，10月在18m水深以下；受水温分层影响，天池水体溶解氧浓度、电导率、pH值、叶绿素a浓度和蓝绿藻细胞密度在垂直剖面表现出明显的季节性分层，尤其是夏季水温分层影响溶解氧浓度、叶绿素a浓度和蓝绿藻细胞密度在水体中的分布，对天池水质变化产生重要影响．天池浅水层（水深小于10m）溶解氧浓度较高（大于8mg／L），而深水层（水深超过18m）溶解氧浓度9月接近4mg／L，季节性缺氧导致底泥营养盐向上扩散，对水体水质产生不利影响．所以，应在夏、秋季节加强水质监测，以防止天池水华发生；天池叶绿素a浓度与蓝绿藻细胞密度的垂直剖面变化趋势相似，均随水深增加呈先增加后减小的趋势，但叶绿素a浓度在2～12m水深处较高，蓝绿藻细胞密度在5～15m水深处较高，表明5～15m深度适合藻类生长，同时，电导率、pH值的垂直变化也说明藻类的生长情况，这为监测天池水体富营养化取样和分析提供依据．

In order to obtain the characteristics of seasonal stratification of Lake Tianchi of Tianshan Mountains, an alpine deep lake, continuous monitoring on vertical dynamics of hydrochemical parameters （water temperature, conductivity, dissolved oxygen （DO） , pH, chlorophyll-a） and algae cell density were conducted from June to October 2014. Lake Tianchi had a short-term of thermal stratification（ from June to September）. The depth of thermocline ranged from 2 m to 18 m in summer, however, it moved down continuously as the time progressed in autumn, and was below 18 m in October; The hydrochemical parameters and algae cell density showed significant seasonal stratification caused by thermal stratification, especially to the distribution of DO and chloro- phyU-a in summer, which had a significant impact on water quality. Besides, from June to October, the concentration of DO de- creased gradually, with 〉 8mg/L in the epilimnion （0 - 10 m） and about 4 mg/L in the hypolimnion （deeper than 18 m） in Sep- tember. As a result, seasonal hypoxia caused nutrients in the sediment moving upward and made water quality worse. Hence, it is necessary to strengthen water quality monitoring in Lake Tianchi to prevent the algal bloom in summer and fall; Chlorephyll-a and algae both increased firstly and then decreased along with depths. However, concentration of chlorephyll-a was higher in the depth of 2 - 12 m than the water surface, and algae cell density was higher in the depth of 5 - 15 m, indicating that the depth of 5 - 15 m was suitable for algae growth. Meanwhile, the vertical change of conductivity and pH value also illustrated the algae growth, which may provide theoretical support for the sampling and analysis of eutrophication in Lake Tianchi.