乌梁素海长时序水质变化及其驱动因子

Long-term changes of water quality and the driving factors of Wuliangsuhai Lake

为了解乌梁素海长时间的水质变化规律,本文基于1999—2019年乌梁素海水质数据,采用幂函数加和型普适指数EI进行富营养化评价,并利用Mann-Kendal与STARS突变检验法,研究乌梁素海水质突变。结果表明:乌梁素海富营养化程度总体呈波动下降趋势,入口、湖中、出口区域水质突变年份分别为2012年、2014年和2016年,突变时间相继后推;3个区域中,入口区总体处于中度和重度富营养化水平,水质突变前后营养盐浓度显著下降,EI下降20.56%,但仍为藻型浊水状态,外源输入与内源富集是造成入口区严重污染的主要原因;湖中及出口区处于轻度富营养化水平,总体呈下降趋势,在草藻共存与藻草共存状态之间波动,湖中区主要受沉积物的内源营养物释放影响,而出口区主要受植物数量减少与鱼类消化代谢影响;乌梁素海3个区域中氮磷比>16的采样占比分别为44.2%、65.7%、72.8%,为典型的磷限制湖泊。本研究为乌梁素海治理及水质突变预警提供科学依据,为干旱区浅水富营养化湖泊水质变化研究提供参考。

In order to understand the long-term variations of water quality in Wuliangsuhai Lake,we used the power function summation type universal index(EI)for eutrophication evaluation based on water quality data of Wuliangsuhai Lake during 1999-2019,and used the Mann-Kendal and STARS mutation test to examine the mutation of water quality in Wuliangsuhai Lake.The results showed that the eutrophic level in Wuliangsuhai Lake showed a fluctuating decreasing trend.Water quality mutation at inlet,center and outlet areas of the lake occurred in 2012,2014 and 2016 respectively,with a postponed occurrence of mutation time one after another.Among the three areas,the inlet was generally at medium and heavy eutrophic level,the nutrient concentrations decreased significantly before and after the mutation of water quality,EI decreased by 20.56%,but it was still in algae-type turbid water state.External inputs and autochthonous enrichment were the main reasons for the serious pollution of the inlet area.The center and outlet areas of the lake were at a light eutrophic level,with an overall decreasing trend,fluctuating between grass-algae and algae-grass coexistence.The center area of the lake was mainly influenced by the release of autochthonous nutrients from the sediments.In the outlet area,the trend was mainly affected by the decrease of plant quantity and the digestion and metabolism of fish.The sampling rates with nitrogen/phosphorus ratios greater than 16 in three areas of Wuliangsuhai Lake were 44.2%,65.7%,and 72.8%respectively,indicating that Wuliangsuhai Lake was phosphorus-limited.Our results provide scientific basis for the management and water quality mutation warning in Wuliangsuhai Lake,and a reference for assessing the changes of water quality in shallow eutrophic lakes in arid areas.