南海水体三项无机氮含量的垂直变化特征及与其他环境要素的相关性

Vertical variations of three nitrogen in water column of South China Sea and their relations to environmental factors

据南海环境调查资料，研究了南海水体NO3-N、NO2-N、NH4-N、DIN含量及无机氮组成的垂直变化规律．结果表明：NO3-N、NO2-N、NH4-N、DIN含量范围和均值分别为0．00～43．9，12．32；0．00～1．69，0．07；0．17-14．87，1．32；0．35～45．92，13．73μmol／dm^3．其含量分布与垂直变化特征与深海、大洋的相似，表明南海水是太平洋的变性水体．NO3-N、DIN含量的垂直分布跃层出现于75～500m间，夏季的跃层强度分别为6．61X10-’、6．68×1012Ixmol／（dm’·m），冬季的均为5．65×10^-2μmol／（dm^3·m）；NO2-N含量的最大值多出现于75～100m之间，NH4-N含量的最大值出现在0m层．在浮游植物活动较旺盛的真光层中，NH4-N为无机氮的主要存在形态（平均占比为64．4％）．真光层以下NO3-N为无机氮的主要存在形态（平均占比≥90．8％）．对三项无机氮含量与其他生源要素、水文因子的相关分析结果表明，NO3-N含量与PO4-P、TDP、TP、SiO3-Si、S均呈显著正相关，与pH、DO、O2％、t则呈显著负相关．

The investigation of the comprehensive survey for marine environment in the South China Sea from June to December, 1998,indicated that the concentration of NO3-N ranges from 0. 00 to 43.9 with a mean 12.32μmol/dm^3, of NO2-N ranges from 0. O0 to 1. 69 with a mean 0. 07μmol/dm^3 ; of NH4-N, from 0. 17 to 14. 87 with a mean 1.32μmol/dm^3 ;of DIN ,from 0.35 to 45.92 with a mean 13.73μmol/dm^3. The vertical distribution of 3 nitrogen are characterized of oceanic waters of deep sea and oceanic water, suggested that the water in the South China Sea are the modified water mass of Pacific Ocean. NO3-N and DIN contents increased with depth, and the vertical gradients in depth of 75 -500m were 6.61 × 10^-2μmol/（dm^3 · m） for NO3-N,6.68 × 10^-2μmol/（dm^3 · m） for DIN in summer. The contents of NO2-N and NH4-N varied little vertically, and the maximum NO2-N and NH4-N appeared at layers of 75 - 100m and 0m,respectively. In euphotic zone ,which was mostly located at surface layer to 75m depth ,NH4-N was the primary form of 3 nitrogen ,and the average percentage of NH4-N/DIN content was around 64.4%. Beyond the euphotic zone, NO3-N was the primary form of 3 nitrogen and the average percentage of NO3-N/DIN content was larger than 90. 8%. The results show that the hydrological and biological factors are the main influencing factors for the vertical variations of 3 nitrogen in the water column. In water layer of 0 - 300m depth, there were existed significant positive correlations of NO3-N content with PO4-P ,TDP, TP, SiO3-Si and salinity, and significant negative correlations with pH, DO, 02 % and temperature.