洪湖沉积物碳氮磷分布特征及污染评价

Carbon,Nitrogen,and Phosphorus in Sediments of Honghu Lake:Spatial Distribution and Pollution Evaluation

洪湖是中国第七大淡水湖,富营养化问题日益突出。全面了解洪湖沉积物氮、磷、有机质的含量及分布特征,对掌握其富营养化现状与氮磷污染生态风险具有重要意义。在湖区布设了8个采样点,2019年10月采集50 cm柱状沉积物,分别测定不同深度沉积物总氮(TN)、总磷(TP)以及有机质(OM)含量,分析了TN、TP和OM含量的空间分布特征及相关性,并运用综合污染指数法评价其对应的污染程度。结果表明:洪湖沉积物TN含量在467.8~8454.5 mg/kg之间,平均值2167 mg/kg,为重度污染,其中近一半的采样点表层沉积物TN含量>5000 mg/kg;TP含量在502.7~1252.4 mg/kg之间,平均值693.8 mg/kg,除杨柴湖为重度污染外,其他大部分地区为中度污染;有机质含量占比在5.0%~24.9%之间,平均值9.6%,为重度污染。在垂直空间上,TN、TP和OM均在沉积物表层垂向深度0~20 cm存在明显的积累,其含量随垂向深度的增加而迅速降低。研究成果可为洪湖富营养化的控制与治理提供科学数据支撑。

Honghu Lake,the seventh largest freshwater lake in China,has been undergoing serious eutrophication in recent years.Investigating into the content and distribution characteristics of nitrogen,phosphorus and organic matters in the sediment of Honghu lake is of great significance for acquiring its eutrophication status and ecological risks of nitrogen and phosphorus pollution.In the present research,we deployed eight sampling points and collected 50 cm height columnar sediments in October 2019.By measuring the content of total nitrogen(TN),total phosphorus(TP)and organic matters(OM)of sediment specimens from different depths,we examined the spatial distribution patterns of TN,TP and OM and their correlations.Furthermore,we evaluated the corresponding pollution status by using comprehensive pollution index.Results manifested that the TN content of Honghu sediments ranged from 467.8-8454.5 mg/kg,averaging 2167 mg/kg,indicating heavy pollution.Nearly half of surface sediments presented a TN content over 5000 mg/kg.TP content ranged from 502.7 to 1252.4 mg/kg,with an average value of 693.8 mg/kg.Except for Yangchai lake which suffered heavy pollution,most of the areas were subjected to medium TP pollution.The content of organic matters ranged from 5.0%to 24.9%,with an average value of 9.6%,also implying heavy pollution.In vertical scale,TN,TP and OM accumulated significantly in the surface layer of the sediments from 0 to 20 cm,and then declined rapidly with the increase of depth.