东苕溪水体氮、磷形态分析及其空间差异性

Forms of nitrogen and phosphorus and their spatial variability in East Tiaoxi River

于2009~2011年在东苕溪开展了4次全流域野外调研,系统分析了东苕溪水体氮、磷形态特征及其空间差异性.东苕溪可分为上游、中-上游、中-下游3个河段,分别具有山溪性河流、城镇影响河流、平原型河道特征.结果表明,水体中氮以溶解态为主,硝态氮(NO_3^--N)是溶解态总氮(DTN)的主要形态;颗粒态磷比例略高,溶解态总磷(DTP)的相对贡献沿程降低.溶解态有机氮(DON)、磷(DOP)分别占DTN和DTP比例的22%、42%,且TN与DON、TP与DOP之间显著正相关.中-上游河段的氨氮(NH_4^+-N),DOP和溶解性正磷酸盐(PO_4^(3-)-P)含量最高且电导率与NH_4^+-N、DOP之间存在显著正相关,表明城镇污、废水排放影响水体氮、磷含量及形态特征;浊度与各形态磷之间均存在极显著正相关,河段下游开矿、行船及挖沙引起的矿质颗粒输入或沉积物再悬浮是磷素的重要来源,但水体中部分溶解态磷吸附在矿质颗粒表面形成胶体物质,导致中-下游河段DTP略有降低.

From 2009 to 2011, four field surveys were carried out in East Tiaoxi River watershed. The forms of nitrogen and phosphorus and their spatial variability were analyzed. East Tiaoxi River could be divided into three sections, namely upper reach, middle-up reach and middle-lower reach, and characterized by hilly river, river influenced by urban and plain river, respectively. The results showed that dissolved nitrogen was the main nitrogen species in water, and nitrate（NO_3^--N） was the major form of dissolved total nitrogen（DTN） species. Meanwhile, phosphorus in particulate form was slightly more abundant than that in dissolved form（dissolved total phosphorus（DTP）） in the samples. And the relative partition of DTP to TP decreased along the river flow. The dissolved organic nitrogen（DON） and phosphorus（DOP） accounted for 22% and 42% of DTN and DTP, respectively, with a significant positive correlations as well. The higher ammonia nitrogen（NH_4^＋-N）, DOP and orthophosphate（PO_4^（3-）-P） in middle-up reach, accompanied by the positively correlated conductivity with NH_4^＋-N and DOP, indicated that the discharge of urban sewage probably affected the contents and species of nitrogen and phosphorus. The positive correlations between turbidity and all forms of phosphorus revealed that the inputs of mineral particles or sediment resuspensions, which were induced from mining, navigation and digging in lower reach, may be important sources of phosphorus. Finally, the slight reduction of DTP in middle-lower reach was also observed, which was probably induced by adsorption of dissolved phosphorus into the surface of mineral particles.