腾冲青海酸性湖水质特征及季节性变化

The Water Quality Characteristics and Seasonal Changes of the Acidic Lake Qinghai Crater Lake in Tengchong

为认识和理解酸性湖泊水质特征的季节变化原因,本文通过对云南腾冲火山口湖青海不同部位水体温度(Temp)、pH、叶绿素(Chl-a)、溶解氧(DO)以及浊度(NTU)参数进行对比分析,初步探讨了该湖水质参数季节性(11月、次年4~6月、9~10月)变化特征。研究分析结果表明:作为我国现有报道的唯一酸性高原湖泊,青海湖水质特征受季节变化影响,冷暖季分明,呈现明显空间异质性,暖季出现热力分层现象,且水深和水温是影响变化的主因(6月水温梯度达到1.98℃/m);与其他高原湖泊相比具有独特特征:pH值在湖泊不同部位存在变化复杂性,从数据分析中发现有从酸性变弱碱性的过程,持续监测和水样化学分析是搞清这个变化过程和机理的关键。溶解氧梯度效应与其他碱性湖泊先增后减不同,呈现上层较高(11月北部测定为8.44 mg/L),中层强烈变化且逐渐减少(5月南部2~2.5 m处DO从6.01下降到0.83 mg/L),深层较低(6月南部5.5 m处为0.31 mg/L)的特点;酸性湖泊与其它湖泊一样,温跃层的存在阻止上层水体溶解氧向下层传递,使上、下层水体形成明显的溶解氧梯度。

In order to understand the relationships between water quality characteristics and seasonal changes in Tengchong Qinghai Lake, one of few acidic lakes reported in China, the water quality parameters, which including water temperature (Temp), chlorophyll-a (Chl.a), dissolved oxygen (DO), pH and turbidity (NTU) in different months of the year were measured and analyzed. The data shows a significant spatial heterogeneity and seasonal variations. Analysis results indicate that the water depth and temperature are the main factors influence the water quality characte-ristics of Qinghai acidic lake. For example, the water temperature gradient in June could be as high as 1.98?C /m. Comparing to other alkaline lakes, the pH values of the acidic Lake Qinghai show a complex variation pattern from one measure point to another, with a lowest value of 3.9 measured in May 2016, and the pH values show a change from strong acid to weak alkaline state from Spring to the Autumn. The reason for such a low pH value is unknown. Further and continuous monitoring and chemical analysis of water samples may provide the key information to understand the process and mechanism of this water quality. It was also found that different from alkaline lakes, the contents of dissolved oxygen was high in the upper part of water layer (as high as 8.44 mg/L in November) and decreased along with water depth increase, with a obvious shift at 2~2.5m in water depth. Presence of the thermocline prevents the dissolved oxygen in upper layer water from mixing with the lower layer, forming a sharp dissolved oxygen gradient.