洪湖营养盐时空分布特征及成因分析

洪湖是江汉平原重要的淡水水体。为了揭示洪湖营养盐时空分布特征和原因,开展了对洪湖为期一年的采样调查,连续采集12个月水样和一次沉积物样品,测定样品中营养盐含量。结果表明:(1)洪湖水体营养盐污染水平较高,除氨氮(NH_4~+-N)外,总氮(TN)、总磷(TP)和高锰酸盐指数(CODMn)难以达到Ⅱ类。(2)空间上有机物污染浓度呈现南高北低的特征,氮磷呈现西高东低的特征;时间上冬季水体氮磷平均浓度最高,夏季氮磷平均浓度最低; COD_(Mn)和氮磷变化相反。(3)表层沉积物有机质(OM)、总氮(TN)、总磷(TP)含量范围分别是16.3～180 g/kg,0.704～7.64 g/kg,0.312～0.801 g/kg。总氮和有机质空间分布相似,南部东北部西北部;总磷空间分布特征,西北部东北部南部。洪湖水质时空变化受内源和外源共同影响。内源主要来自沉积物和水生植物,外源输入主要包括四湖总干渠汇入和人类活动产生的污染。

Research on Spatio-temporal Variation and Causes of Nutrients in Honghu Lake

Honghu Lake is an important fresh water body in the Jianghan Plain. In order to explore the spatial and temporal distribution characteristics of nutrient in the overlying water and sediment in Honghu Lake, and to reveal the causes, a one-year sampling survey was carried out in Honghu Lake, with 12 successive monthly water samples and one time sediment sample collected and determined for the nutrient content. The main conclusion was as follows, (1) The level of nutrient pollution in Honghu Lake was relatively high. Except for ammonia nitrogen, the total nitrogen, total phosphorus, and permanganate indexes in water were difficult to reach category II of surface water criterion. (2) The organic matter pollution was high in the south and low in the north, and the nitrogen and phosphorus content were high in the west and low in the east; the average concentration of nitrogen and phosphorus in the water was highest in winter, and the average concentration of nitrogen and phosphorus was lowest in summer; The changes of these two type nutrients were opposite. (3) The content of TN, TP, and OM in the surface sediments of Honghu Lake was relatively high. The contents of OM,TN, and TP,in the sediment were 16.3-180 g/kg, 0.704-7.64 g/kg, 0.312-0.801 g/kg, respectively.The spatial distribution of total nitrogen and organic matter was similar, with south > northeast > northwest; the spatial distribution of total phosphorus showed a trend of northwest > northeast > south. The temporal and spatial changes of water quality of Honghu Lake were affected by both internal and external sources. The internal sources mainly came from the sediments and aquatic plants, and the external sources mainly include the inflow of the Four Main Canal and the pollution caused by human activities.