鄱阳湖富营养化时空变化特征及其与水位的关系

The Spatial-Temporal Characteristics of Eutrophication in Poyang Lake and Its Relationship with the Water Level

为了研究鄱阳湖水体的富营养化状态与水位变化的响应关系,基于2009—2016年鄱阳湖15个长期监测点的调查数据,采用TLI (综合营养状态指数)法评价了鄱阳湖水体的富营养化状态,并应用主成分分析(PCA)探讨了鄱阳湖富营养化状态的时空变化特征及其与水位的关系.结果表明:①从年内变化来看,鄱阳湖除冬季(1月)处于轻度富营养化状态,其余3个季节均处于中营养状态,其中,夏季(7月)富营养化程度最低是由于其水位较高、换水周期快所致,冬季处于轻度富营养化是由于水位降低导致的营养盐浓度升高以及湖泊沉淀物的再悬浮和营养盐的释放;从年际变化来看,除2011年、2012年及2014年鄱阳湖处于轻度富营养化状态外,其余年份均处于中营养状态.②从空间上来看,鄱阳湖湖区整体处于中营养状态,空间差异不大,湖区中部东侧富营养化程度最高.③在年内季节变化上富营养化程度与水位呈负相关,富营养化的空间分布特征与水位关系较小.研究显示,鄱阳湖整体富营养化程度不高,但有向富营养化湖泊发展的趋势,建议通过控制湖区污染源来减轻其富营养化程度.

In order to investigate the eutrophication of Poyang Lake and its variety characteristics under the change of water level,the eutrophication level of water body in the Poyang Lake region was appraised by TLI based on the periodical survey data from 15 long-term monitoring sites in Poyang Lake region during 2009-2016. At the same time,principal component analysis(PCA) was adopted to discuss the spatial-temporal characteristics of eutrophication in the Poyang Lake region as well as the relationship between the eutrophication state and water level. The results show that:(1) From the point of view of the change in one year,Poyang Lake was at the light eutrophic level in winter(January) while was at the mesotrophic level in the other three seasons,among which the summer(July) eutrophication degree was the lowest,due to the high water level in summer. The water changing period is fast. The decrease in water level in winter lead to the increase in nutrient concentration and the re-suspension of sediment and release of nutrients. In terms of annual changes,Poyang Lake in2011,2012 and 2014 was at the light eutrophic level,while at the mesotrophic level for the rest years.(2) In space,the Poyang Lake regions are integrally at the level of mesotrophic with little difference. Eutrophication was the highest in the eastern part of the middle lake district.(3) The change of water level in Poyang Lake had the most significant effect on eutrophication in seasonal changes during the year. The spatial distribution of eutrophication has little relation with the water level. The research shows that Poyang Lake is not at the eutrophic level on the whole,but it has the trend to become eutrophic. It is suggested that the degree of eutrophication should be reduced by controlling the pollution sources.