太湖竺山湾沉积物碳氮磷分布特征与污染评价

为了揭示太湖竺山湾沉积物中碳、氮和磷的分布特征,本研究在太湖竺山湾设置3个断面(湖湾内,A断面;湖湾中部,B断面;开敞湖区,C断面) 10个采样点,采集沉积物柱状样,每2 cm间隔分层测定沉积物中总氮(TN)、总磷(TP)和总有机碳(TOC)含量,以揭示其水平分布和垂向分布特征.结果表明,在空间上竺山湾表层沉积物呈现开敞湖区向湖湾富集的特征,湖湾内部碳、氮和磷含量显著高于开敞湖区(P 0. 01),其中湖湾内(A断面)表层沉积物TN、TP和TOC含量分别为1. 53、1. 55和11. 31 mg·g~(-1),而靠近开敞湖区(C断面)表层沉积物TN、TP和TOC含量仅为0. 75、0. 57和6. 70 mg·g~(-1).垂向分布特征表现为表层富集,3个断面TN、TP和TOC含量随着底泥深度的增加均呈现出下降趋势,表层沉积物TN、TP和TOC含量分别是底层的2～3、2～5和2～3倍.整体而言,竺山湾沉积物TP含量均值为0. 93 mg·g~(-1),属于重度污染,而TN平均含量为1. 11 mg·g~(-1),属于轻度污染;有机氮指数和综合污染指数显示,竺山湾北部地区污染水平为重度污染区,有机污染相对较强,TP的污染指数(STP)处于1. 03～3. 87之间,属于重度污染.

Spatial Distribution and Pollution Evaluation of Carbon, Nitrogen, and Phosphorus in Sediments of Zhushan Bay at Taihu Lake

To reveal the distribution characteristics of carbon, nitrogen and phosphorus in the sediments of Zhushan Bay at Taihu Lake, sedimentary columns were collected and sliced by 2 cm vertically from ten sampling points in three sections of Zhushan Bay. The content of total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) were determined for each slice to reveal their horizontal and vertical distribution. The results showed that:spatially, the content of TN, TP, and TOC increased in the surface sediments of Zhushan Bay from the open lake area to the bay, and inside the bay these indexes were significantly higher than in the open lake area (P<0.01). The content of TN, TP, and TOC in the surface sediments in the bay (section A) were 1.53 mg·g^-1, 1.55 mg·g^-1, and 11.31 mg·g^-1, respectively, while in the surface sediments near the open lake (section C) they were only 0.75 mg·g^-1, 0.57 mg·g^-1, and 6.70 mg·g^-1, respectively. Vertically, a feature of surficial enrichment was shown, and the contents of carbon, nitrogen and phosphorus in all three sections showed a decreasing trend with increase of depth. The contents of TN, TP and TOC in the surface sediments are 2-3 times, 2-5 times, and 2-3 times those in the bottom sediments, respectively. Generally, the average TP content in the sediment of Zhushan Bay is 0.93 mg·g^-1, suggesting an apparent heavy pollution, while the average TN content is 1.11 mg·g^-1 as slight pollution. According to the organic nitrogen index and comprehensive pollution index, the northern part of Zhushan Bay is suffering from heavy pollution, where the organic pollution is relatively strong. The TP pollution index is between 1.03 and 3.87, indicating heavy pollution in Zhushan Bay.