太湖西部河网中沉积物氮的空间分布特征

选取太湖主要入湖水系(西苕溪水系和宜溧-洮滆水系)为研究对象,于2014年1月完成水体及表层沉积物各102个样品的采集,分析了沉积物中氮(N)不同形态的空间分布特征及其影响因素.结果表明,西苕溪水系表层沉积物总氮(TN)含量高于宜溧-洮滆水系,均值分别为2164.91 mg·kg~(-1)和983.52 mg·kg~(-1),两个水系间沉积物TN含量存在显著差异.西苕溪和宜溧-洮滆两个水系沉积物中无机氮(IN)以氨氮(NH+4-N)为主,平均含量分别为120.90 mg·kg~(-1)和49.85 mg·kg~(-1),而硝态氮(NO_3~--N)平均含量仅为9.60 mg·kg~(-1)和13.95 mg·kg~(-1).沉积物中有机氮(ON)含量及分布与TN相似,西苕溪和宜溧-洮滆水系ON均值分别为2034.41 mg·kg~(-1)和917.77 mg·kg~(-1),占各自TN的百分比分别为93.90%和92.99%.表层沉积物各形态N之间及与上覆水体之间均具有显著的相关性,表明沉积物与上覆水之间的浓度梯度可能会驱动IN向上覆水体进行释放.

The spatial distribution of nitrogen species in surface sediment in the west river networks of the Taihu Lake Basin, China

The objectives of this study were to evaluate the spatial distribution and the relationships of different nitrogen forms in water column and surface sediment in two main inflow rivers (West Tiaoxi and Yili-Taoge) of the Taihu Lake Basin, China. Water and sediment samples were collected from 102 sites, and different nitrogen forms were analyzed in laboratory. The results showed significant difference of sediment total nitrogen (TN) concentrations between the West Tiaoxi and Yili-Taoge rivers, with mean values of 2164.91 mg·kg^-1 and 983.52 mg·kg^-1, respectively. Ammonium nitrogen (NH₄⁺-N) was the main form of inorganic nitrogen in surface sediment in both rivers, with the average concentrations of 120.90 mg·kg^-1 and 49.85 mg·kg^-1. The average concentrations of organic nitrogen (ON) in sediment of the two rivers were 2034.41 mg·kg^-1 and 917.77 mg·kg^-1, and the spatial distribution pattern of ON was similar to TN. The percentage of ON in TN of the two rivers were 93.90% and 92.99%, respectively. The Spearman correlation analysis showed that there were significant correlations between different nitrogen forms in the surface sediment, and between surface sediment and overlying water columns. The results implied that surface sediment could release inorganic nitrogen to the overlying water because of their nitrogen concentration gradients.