长江水体溶解态无机氮和磷现状及长期变化特点

ANALYSIS OF DISTRIBUTION,FLUX AND LONG-TERM VARIATIONS OF DISSOLVED INORGANIC NITROGEN AND PHOSPHATE IN THE CHANGJIANG RIVER

于2006年2、5、8和11月对长江从攀枝花至河口和上游的两条支流雅砻江和嘉陵江的溶解态无机氮(NO-3-N、NO-2-N和NH+4-N)和磷酸盐(PO43--P)进行了取样调查,同时结合长江营养盐的历史数据,分析了长江水体中溶解态无机氮、磷的长期变化特点。结果表明,长江NO-3-N、NH+4-N、DIN(包括NO-3-N、NO-2-N和NH+4-N)和PO3-4-P浓度从上游到下游显示出增加趋势,但存在季节差异;NO2-N浓度总体较低,在长江中下游(武汉—南京)浓度较高。长江从上游到下游DIN通量的变化主要受径流量的影响,从上游到下游单位面积年产N量逐渐升高;PO3-4-P输送通量从上游往下游呈增加趋势,也主要受径流量控制,但从季节变化来讲,PO3-4-P的月输送通量受其浓度的控制更加明显。自20世纪60年代来,长江水体中NO3--N、NO2--N、DIN和PO3-4-P的浓度都处于缓慢上升趋势,但到80年代上升速度明显加快;不同阶段DIN和34PO-P的季节变化特点也不尽相同,反映了其来源的差异。目前,长江水体中溶解态无机氮、磷浓度与国内及国际河流相比处于中等水平。

The concentrations of dissolved inorganic nitrogen （ NO3-N, NO2-N and NH4 -N） and dissolved inorganic phosphate （pO34- -P） were investigated from Panzhihua to Shanhai in the Changjiang River and two tributaries of the upper drainage （Yalongjiang River and Jialingjiang River） during February, May, August and November in 2006. The results showed that NO3-N, NH4 -N, DIN or pO34- -P concentration increased from upstream to downstream while there were seasonal differences. The concentration of NO2-N was relatively low and it was higher in the middle and lower reaches from Wuhan to Nanjing. DIN flux in the Changjiang River was mainly controlled by water discharge, however monthly pO34- -P flux was greatly influenced by the riverine concentration of PO34- -P when the seasonal variations were considered. The areal yields of DIN and PO34- -P increased obviously from upstream to downstream. The concentrations of NO3-N, NO2-N, DIN and PO34-P increased steadily since 1960s and rose greatly after 1980. The seasonal variations of DIN and PO43-P were quite different, which suggested that they might be from different sources. Compared with other large rivers in the world, the concentrations of DIN and PO34- -P were higher than those of the large and less disturbed world systems and lower than those of the eutrophic rivers in Europe and North America.