巢湖典型流域河道沉积物磷赋存形态研究

Study on phosphorus fractions in river sediments of typical watersheds of Chao Lake basin

河道沉积物磷的含量和形态可为流域磷的来源解析及评估其对下游受纳水体的影响提供重要信息。选取巢湖典型支流丰乐河和柘皋河,在平水期对两个流域共计27个采样点进行了沉积物和河水采样,沉积物采用SMT(standards measurements testing)法进行分级测定磷的不同形态,包括总磷(TP)、无机磷(IP)、有机磷(OP)、铁铝磷(Fe/Al-P)以及钙磷(Ca-P),水样测定总磷(TP)和可溶性磷(DP)。结果表明,丰乐河沉积物中TP、IP和OP的平均含量分别为522.12、323.78和140.42 mg·kg^(-1),而柘皋河分别为1060.70、755.74和125.31 mg·kg^(-1),均表现为TP>IP>OP。丰乐河IP中的Fe/Al-P平均含量高于Ca-P,而柘皋河则相反。柘皋河沉积物TP、IP、Fe/Al-P和Ca-P总体均高于丰乐河,但丰乐河OP含量略高于柘皋河。两河不同采样点沉积物不同形态磷含量均存在较大的空间差异。丰乐河和柘皋河河水TP平均值分别为0.10和0.18 mg·L^(-1),均以溶解态为主,易导致富营养化。两个流域都是农业流域,河流中磷主要来源是农业非点源和城镇生活污水的输入。柘皋河农田和村镇都相对比较集中分布在河边,不同来源的磷更容易输送到达河道。柘皋河流域距入湖口近,沉积物和河水磷含量均高于丰乐河,因此柘皋河对加剧巢湖水体富营养化的风险更大,但丰乐河沉积物Fe/Al-P和河水磷含量也比较高,依然存在一定的风险。

The contents and fractions of phosphorus in river sediment can provide important information for source analysis and the evaluation of its influence on downstream receiving water bodies.In this study,spatially distributed sampling was applied during normal-low flow period on Fengle and Zhegao,which are the two inflow rivers of Chao Lake basin.Sediment and river water samples were taken at 14 sites on Fengle river and 13 on Zhegao.The SMT(standards measurements testing)protocol was applied for the analysis of five fractions of phosphorus,including total phosphorus(TP),inorganic phosphorus(IP),organic phosphorus(OP),iron-aluminum phosphorus(Fe/Al-P)and calcium phosphorus(Ca-P);river water samples were analyzed for TP and dissolved phosphorus(DP).The results showed that the average contents of TP,IP and OP in Fengle river sediments were 522.12,323.78 and 140.42mg·kg^(-1),respectively;and which in Zhegao river sediments were 1060.70,755.74 and 125.31 mg·kg^(-1),respectively;both demonstrating an order as TP>IP>OP.For IP,the average content of Fe/Al-P in Fengle river sediment was higher than that of Ca-P,while it was the opposite for Zhegao.The average contents of TP,IP,Fe/Al-P and Ca-P in sediments of Zhegao river were higher than those in Fengle river,but the content of OP in Fengle was slightly higher than that in Zhegao.The concentrations of phosphorus fractions in sediments demonstrated large spatial variations for both rivers.The average TP concentrations in the water of Fengle and Zhegao were 0.10 and 0.18 mg·L^(-1),respectively,which were mainly composed of DP,thus at a risk of eutrophication.Both Fengle and Zhegao were of typical agricultural watersheds.Agricultural nonpoint sources inflow and the input of town sewage were the main contributions of phosphorus in river sediments and water.The crop and vegetable fields,towns or villages of Zhegao watershed were mostly located along or near the riverbanks,where phosphorus could be more easily transported to river channels.As Zhegao watershed was closer to Chao Lake and the phosphorus content in both sediment and river water was higher than that in Fengle,it had a greater risk of worsening the eutrophication status in Chaohu Lake.However,since Fe/Al-P in sediments and TP in river water of Fengle river were relatively high as well,there was still a risk of contributing to the eutrophication in the downstream reaches and finally the Chao Lake.