丰水期鄱阳湖氮磷含量变化及来源分析

通过系统测定丰水期鄱阳湖湖水、主要支流水、长江水及部分农田水、地下水及城市污水的氮磷含量，对其氮磷含量变化及来源进行了分析，结果表明，鄱阳湖水体中主要的氮素形式是硝酸盐氮（090 mg/L），赣江是其主要贡献者。鄱阳湖五大支流氮磷含量存在着较大的差异，赣江NO-3 N含量明显高于鄱阳湖其它主干流，而NH+4 N和TN含量以饶河的最高，TP以信江的最高。农田水、城市废水以及地下水含有较高的氮磷含量，是鄱阳湖及其五大支流氮磷的主要来源。农田水TN和TP含量最高，分别为1347、2863 mg/L。高含量的NO-3 N（735 mg/L）和NH+4 N（548 mg/L）分别出现在地下水和城市污水中。鄱阳湖水体氮负荷较大，N/P比值远大于7〖DK〗∶1。受滞留区及赣江和修水补给的影响，鄱阳湖主河道氮含量变化从上游至下游呈总体上升趋势。鄱阳湖湖体氮含量以下游最高，滞留区次之，上游主河道最低，TP含量呈相反的趋势变化。底层沉积有机物的降解和扰动导致鄱阳湖水体底层NO-3 N、NH+4 N、TN、TP的含量高于表层。

CONCENTRATION VARIATIONS OF N AND P IN POYANG LAKE DURING HIGH WATER PERIOD WITH ANALYSIS ON THEIR SOURCES

Based on the systematic determination of nitrogen (N) and phosphorus (P) concentrations in Poyang Lake water, the main river water, Yangtze River water,and some agricultural drainage, groundwa- ter and urban sewage at August 2005 (high water period), the concentration variations of nitrogen and phosphorus and their sources were investigated. The results showed that NO_3~--N dominated in the forms of nitrogen in Poyang Lake,most of those came from Ganjiang River. The mean concentration of NO_3~--N was 0.90 mg/L and the mean content of total nitrogen (TN) was 1.04 mg/L in Poyang Lake. Among the main five river,the highest concentration of NO_3~--N was found in Ganjiang River,the highest concentrations of NH_4~ -N and TN were found in Raohe River and the concentrations of TP is highest in Xinjiang River. The nitrogen and phosphorus concentrations of agricultural drainage,groundwater and urban sewage were very high,which were the main sources of Poyang Lake catchments. The mean concentration of TN and total phosphorus (TP) was 13.47 and 28. 63 mg/L respectively in agricultural drainage. The mean content of NO_3~--N was 7.35 mg/L in groundwater and the mean concentration of NH_4~ -N was 5.48 mg/L in urban sewage. The loads of nitrogen were very high in Poyang Lake water,and the ratio of N/P more than 7. The content of nitrogen was increasing along the water flow direction in the main riverway of Poyang Lake, which is due to the recharge from the stagnant area and the inflow of Ganjiang River and Xiushui River. The highest nitrogen concentration was in the downflow water, followed by in the stagnant area,and the lowest was in the main upstream riverway. But the content of phosphorus showed an adverse trend, the lowest was in the downflow water. The concentrations of NO_3~--N,NH_4~ -N,TN and TP were higher in sur- face water than in bottom water due to the degradation of sedimentary organic matters and disturbance.