滇池湖滨带沉积物氮形态的空间分布

Spatial distribution of nitrogen species in sediment of lakeside zone of Lake Dianchi

2008年4月在滇池全湖湖滨带布设23个采样点并采样,通过测量该23个表层沉积物样和16个柱状沉积物样（0-15cm）的总氮、氨氮、硝氮和有机氮质量分数,揭示滇池湖滨带沉积物氮的空间分布。研究表明：滇池湖滨带各点位表层沉积物总氮平均质量分数为1667mg·kg^-1,低于湖区沉积物,湖滨带对湖水中氮的吸收与净化是重要原因之一。草海的污染水平高于外海,滇池外海湖滨带沉积物污染状况由北向南衰减,但南部海口出湖区湖滨带属于滇池出水口区域,其沉积物氮质量分数高于中度富营养的外海,而低于重度富营养的草海。草海和外海湖滨带沉积物总氮质量分数在2008-1992、1992-1975、1975-1960年3个时间段平均值分别为2889.07、3343.68、4010.20和896.57、655.37、845.01mg·kg^-1,草海湖滨带沉积物中有机氮是总氮的主要组成部分,总氮与氨氮、硝氮、有机氮之间的相关性良好,各种形态的氮与总氮在分布情况上密切相关。而外海湖滨带沉积物中总氮仅与有机氮的相关性很好,两者的分布趋于一致,但各种形态的氮间相关性较弱、分布差异较大。

23 surface sediments and 16 core sediments （depth between 0 and 15 cm） were sampled from various sections in lakeside zone of Lake Dianchi at April 2008. The mass fraction of total nitrogen, ammonia nitrogen, nitrate nitrogen and organic nitrogen in these samples had been determined. The spatial distributions of nitrogen species in the sediments of the lakeside zone of Lake Dian- chi were made. The results showed that the average mass fraction of total nitrogen in the surface sediments of the lakeside zone of Lake Dianchi was 1 667 mg/kg, less than that of the lake zone. This was because the absorption and purification properties towards aqueous nitrogen of the lakeside zone. The situation of Caohai lakeside was more serious than that of Waihai lakeside. In Waihai lakeside zone, the contamination was gradually declined from north to south. The total nitrogen average mass fraction of surface sediment in Haikou, the southern lakeside zone and the outlet of the whole Dianchi, was higher than that in Lake Waihai in the moderate eutrophic condition, but lower than that in Lake Caohai under severe eutrophic conditions. During the following three periods, i.e. 2008-- 1992, 1992-- 1975, 1975-- 1960, the total nitrogen average mass fraction in the sediments were 2 889.07, 3 343.68, and 4 010.20 mg/kg in Caohai lakeside, while 896.57, 655.37 and 845.01 mg/kg in Waihai lakeside. The organic nitrogen accounted for the majority constituent of total nitrogen. In Caohai lakeside, the total nitrogen, ammonia nitrogen, nitrate nitrogen and organiC ni- trogen mass fraction in sediments had good correlation, which meant they had a close relationship of distribution. However, in Wai- hai lakeside, the total nitrogen in sediments only had a good correlation with the organic nitrogen, which meant they had a close relationship; while the ammonia nitrogen, nitrate nitrogen and organic nitrogen mass fraction had poor correlations among them, which were quite different in the aspects of distributions.