苏州河网区河道上覆水与底泥中氮素形态分布特征

以苏州河网区河道为研究对象，分布式采集10个采样点，分析水质状况和底泥中氮素形态与含量及其剖面分布，以探讨上覆水和底泥中各形态氮的相关性. 结果表明:上覆水中ρ(总氮)，ρ(总磷)及ρ(COD_Cr)均超标，水质呈弱碱性，ρ(硝态氮)(1.10～2.39 mg/L)均高于ρ(铵态氮)(0.30～1.70 mg/L)，80%的采样点水质为劣Ⅴ类，水质污染严重，且以氮污染为主；底泥中w(总氮)为2.78～6.30 g/kg，其随沉积深度的增加而减少，说明河道污染负荷有逐年加重的趋势；底泥中w(铵态氮)为37.2～228.0 mg/kg，其随沉积深度的增加而增加，说明铵态氮的沉积量在逐年减少；底泥中w(硝态氮)为13.1～69.4 mg/kg，其在各点的剖面变化趋势不尽相同，这可能与河道水体流动性较大有关. 相关性分析和空间关系分析显示，虽然上覆水中各形态氮含量和底泥表层中各形态氮含量点位对应的关系不显著，但在空间上存在一定的关联性，即由于水体的流动性，使得底泥到上覆水的氮含量高值区有从东向西迁移的趋势. 

Characteristics of Nitrogen Distribution in River Water and Sediments in the Typical River Network Region of Suzhou City

Ten selected sites were sampled in typical river network region of Suzhou City. The quality of river water and the contents of various nitrogen forms in the sediment profiles were measured. The relationship among various nitrogen forms in the water and sediment was discussed. The results showed that the contents of TN, TP and COD_(Cr) in the river water exceeded the state standard of water quality, and the water was slightly alkaline. The content of NO_3~--N (1.10-2.39 mg/L) was higher than that of NH_4~+-N (0.30-1.70 mg/L) in the water. The water, of which 80% was worse than the Ⅴ grade of water quality, was polluted seriously. The major pollution of the river water resulted from nitrogen. In the sediment, the content of TN ranged from 2.78 to 6.30 g/kg, and it decreased with increasing sediment depth, suggesting that the pollution of rivers was becoming more and more serious year after year. The content of NH_4~+-N ranged from 37.2 to 228.0 mg/kg in the sediments. It increased with increasing sediment depth, indicating that the content of NH_4~+-N decreased year after year. The content of NO_3~--N ranged from 13.1 to 69.4 mg/kg in the sediments. However, the distribution pattern of NO_3~--N in the sediment profiles in different sampling sites was different from each other. The rapid water flow may be responsible for such a result. Correlation and spatial distribution analysis showed that there was no direct corresponding relationship between the various forms of nitrogen in the overlying water and those in the sediment surface layer in situ, but there was an obvious corresponding relationship spatially. Due to the water flow characteristics, the high content of nitrogen in the sediment was reflected in the overlaying water moving from the east to the west.