白洋淀多种生境沉积物有机质来源解析及其演变

Source analysis and evolution of organic matter in sediments from various habitats in Baiyangdian Lake

沉积物有机质来源及其演变的解析对富营养化湖泊的防治及生态修复具有重要的意义.白洋淀是华北地区最大的淡水湖泊,由于受人类活动的影响,其生境逐渐破碎化且不同生境的有机质来源及演变过程尚不清楚.通过对白洋淀河道、湖面、鱼塘、荷塘4种不同生境沉积物岩芯正构烷烃含量与组成特征的分析,结合主成分分析-多元线性回归(PCA-MLR)模型,以解析其有机质的来源及演变.结果表明:由于受不同人类活动的影响,不同生境沉积物的有机质来源不同.鱼塘和荷塘沉积物有机质来源以藻类等水生低等生物为主,分别达到78.3%、72.7%;河道沉积物有机质来源则以陆生高等植物为主,占比为63.8%;开阔湖面沉积物中不同有机质来源所占比例分别为水生低等生物33.0%,水生高等植物26.2%,陆生高等植物40.8%.该结果与白洋淀地区人类活动变化与经济社会发展历程相对应.值得注意的是,尽管随着雄安新区一系列环境治理措施和环保工程的实施,白洋淀水质恶化趋势得到遏制,藻类等水生低等生物在河道和湖面的沉积物有机质来源占比开始缓慢降低,但是由于水体富营养化程度较深且藻类死亡后仍大量沉积于沉积物中,鱼塘和荷塘沉积物有机质来源中水生低等生物的占比仍然较高,建议辅以清淤等工程措施处理.研究表明,正构烷烃的碳数分布及其受体模型可以作为定量表征有机质来源及其演变历史的工具,对研究多生境水体环境演变和管理政策制定有着重要意义.

The understanding of the source and evolution of sediment organic matter is of great significance to the eutrophication control and ecological restoration of lakes.As the largest freshwater lake in North China,the habitat of Baiyangdian Lake is gradually fragmented due to the influence of human activities.The evolution process of organic matter in sediments of different habitats of Baiyangdian Lake are still unclear.In this study,the content and composition of n-alkanes in sediment cores of four habitats(river course,lake surface,fish pond,lotus pond)of Baiyangdian Lake were measured,and the source and historical changes of organic matter in sediments were analyzed using principal component analysis-multiple linear regression(PCA-MLR)model.The results showed that sediments from various habitats had different organic matter sources due to different human activities.Aquatic lower organisms was the dominant source of organic matter in sediments from fish pond and lotus pond,reaching 78.3% and 72.7%,respectively.higher Terrestrial plants was the main contributor to the organic matter source in sediments from river course,accounting for 63.8%.The proportions of different organic matter sources in the sediments from lake surface were 33.0% of aquatic lower organisms,26.2% of aquatic plants,and40.8% of terrestrial plants,respectively.This result is coincident with the changes in human activities and economic and social development in Baiyangdian area.In recent years,with the implementation of a series of environmental management measures and environmental protection projects,the trend of local water quality deterioration has been curbed,and thus the proportion of aquatic lower organisms in organic matter of sediments from river course and lake surface decreased.However,due to the serious eutrophication of water body and the large amount of algae deposited in sediments,the proportions of aquatic lower organisms in organic matter of sediments from fish ponds and lotus ponds were still high.Therefore,it is recommended to take engineering measures,such as dredging,to control the internal source pollution.This research indicates that the carbon number distribution of n-alkanes and their receptor models can be used as an efficient tool to quantitatively characterize the sources and evolution of sediment organic matter,which is of great significance to multi-habitat water environment evolution research and management policy formulation.