滇池水体和表层沉积物间隙水中氮分布特征研究

Distributive features of nitrogen in the water and the surface water poring sediments in Dianchi Lake, Kunming

以滇池表层水、中层水、上覆水及表层沉积物间隙水为研究对象,分析了其中TN、NH+4-N和NO-3-N的质量浓度及分布特征,并估算了沉积物-水界面氮的扩散通量。结果表明:在滇池水体中,草海区域氮的质量浓度最高,其次是外海Ⅰ区,区域差异特征明显;表层沉积物间隙水中的NH+4-N、TN也以草海区域的质量浓度最高,其次是外海Ⅱ区和Ⅳ区,草海间隙水的NO-3-N质量浓度仅为0.60 mg/L,与外海质量浓度无显著差别。从垂直方向看,各种形态的氮在表层水、中层水、上覆水中质量浓度相当,而表层沉积物间隙水中NH+4-N、TN质量浓度分别为上覆水平均质量浓度的14倍和6倍,间隙水中NO-3-N质量浓度与上覆水平均质量浓度差异不明显。在沉积物-水界面中,NH+4-N平均扩散通量为592.48μmol/(m2·d),呈现出表层沉积物间隙水中的氮以NH+4-N为主向上层水体释放的趋势。

The paper attempts to take the typical eutrophication of the suburban lake, Dianchi, Kunming, as a case study sample of our re search for tracing the distributive features of nitrogen in it. For our research purpose, we have tested and investigated the concentrations and the distributive features of the total nitrogen （TN）, ammonia （NH4＋ - N） and nitrate （NO3- N） on the surface of the water, the middle level of the water and the deep level of the water and the pore water from the surface sediments in the Lake as well as the diffusion flux of the inorganic nitrogen distribution of the sediment-water interface. And, for the research convenience, we have divided the lake water into five areas geographically with each divided into some sam pling areas. And, methodically, we have adopted a data-and-infor mation surfing software to our analysis of the distributive features of nitrogen nutrients in the different spatial levels of the water body. The resuhs of our analysis indicate that the highest part of the nitrogen nu-trient concentration in the water body has been found in Caohai area, much higher in Area I than that in other areas in Waihai, though there exists noticeable regional variation, which may account for its external nutritious charge in comparison with that in other parts. The concentration of NH4＋ - N and TN of the pore water from the surface sediments in Caohai has been found highest, which is followed by Area 1 and Area IV . To be accurate, the concentration of NO3- - N in Caohai Area stands for 0.60 mg/L, though no significant differ- ence has been found in the presence of NO3- - N between Caohai and Waihai Areas. Besides, we have also detected a close correlation be- tween the N concentration in the surface sediments of the pore water and that of the surface water. However, no discrepancy can be found between the distributions of netrogen in the surface, middle and overlaying water levels except for the concentrations of NH4＋ - N, TN in the pore water of the surface sediments, which prove to be 14 times and 6 times higher than those in the overlaying water of Waihai. Nev- ertheless, the concentration of NO3- - N in the pore water of the surface sediments has been found almost the same in the overlaying water level in Waihai Area. What is more, the average diffusion flux of NHn＋ - N stands for 592.48 mol/（m2.d）, with NH4＋ - N being the chief form of the nitrogen diffusion from the sediment to the pore water across the sediment-water interface.