2015~2016年洱海水质参数季节性变化 The Seasonal Variations of the Water Quality of Erhai during 2015-2016

随着洱海流域建设和生产、生活规模的快速扩展，对洱海水质的影响也日益增强。为了解和认识其水质现状和变化过程，我们对洱海进行了定位水质监测。通过对监测数据分析结果表明：洱海的湖水受到风浪的强烈影响，较浅的南部湖区混合度>北部湖区>中部湖区。作为高原浅水湖泊，洱海不存在温度分层现象，但是7月份在中部湖区与北部湖区出现温跃层和湖上层的混合现象；水温的季节变化影响叶绿素a的变化，较浅的南部湖区更易受到人类活动与自然因素(如风力、吹程、湖流)等多重影响；洱海水体的溶解氧含量存在季节变化，表现为1月份高而7月低；洱海的pH值季节性差异较明显，就监测月份而言，1月份的pH最低，pH值易受水生动植物的光合作用和呼吸作用的影响，7月在湖泊水体中波动较大；洱海水体10月份的叶绿素a浓度、溶解氧浓度和pH值之间均存在显著的相关性；洱海水体中的浊度在季节性变化中受水体深度以及浮游动植物量的影响较大。洱海不同湖区水体的温度(Temp)、叶绿素-a (Chll-a)、溶解氧(DO)、pH以及浊度(Turbid+)的季节性(1月、4月、7月和10月)变化特征显著，并存在明显的空间异质性，结合总氮和总磷数据进行营养化评估，结果显示洱海处于中营养化阶段。 Along with the regional economic development and urban expansion in the Erhai drainage area, the water quality of Lake Erhai has been impacted strongly. To understand the water quality status and its change processes, we have monitored the lake water recently. The analyses results of the monitoring data show that the mixedness of lake water, which is affected by the strong wind and waves in the Lake Erhai, is the highest in the south of lake where with a shallow water depth, and is the lowest in central part of lake, while it shows a moderate situation in the north of the lake. As one of the typical plateau-type shallow lakes, there is no temperature stratification observed in Lake Erhai, but a weak mixing phenomenon between thermocline and epilimnion exist in the central and north part of the lake in July. The seasonal water temperature changes affect the distribution and content of chlorophyll-a, which is also affected by human activity induced nutrient inputs, especially in the shallow area in south of the Lake Erhai, where is more sensitive to natural factors, such as wind velocity, direction and lake current. The dissolved oxygen (DO) content is not only influenced by the algae in lake water, but also the discharge of rivers into the lake. Our monitoring data reveal a seasonal variation of the DO contents, and show a highest value in January high and a lowest value in July. At the same time, the pH value shows a distinguishable seasonal variation with a lowest value in January. As pH is very sensitive to the photosynthesis and respiration of aquatic animals and plants in the lake water, it varies from one area to another abruptly in July. It has been noticed that a strong correlation exist between the chlorophyll-a content, DO and pH values in October. The seasonal change of turbidity is sensitive to water depth and zooplankton and phytoplankton amounts. The total contents of both Nitrogen (TN) and Phosphorous (TP) reveal that Lake Erhai is approaching to the middle to middle-high eutrophication situation, and strong measurements to prevent the lake from further eutrophication is necessary.