洱海表层沉积物中总氮含量及氨氮的释放特征

通过现场调查和室内模拟试验,对洱海具有代表性的9个表层沉积物样品中w(TN)的分布特征以及沉积物中NH₄+-N释放动力学特征进行了研究. 结果表明,洱海表层沉积物中w(TN)在2.0844～6.5153g/kg之间,平均值为3.5378g/kg,北部西岸为高值区,南部(靠近大理市)为次高值区. 一级动力学模型可很好地拟合洱海表层沉积物NH₄+-N释放动力学特征,NH₄+-N最大释放量在0.1209～0.2810g/kg之间；释放主要集中在0~5min内,约占最大释放量的68%~83%；随后释放速率逐渐放缓,到120min后基本达到释放平衡.运用无限稀释法对沉积物NH₄+-N释放潜能进行测定表明,洱海沉积物NH₄+-N释放潜能在1.7001~3.5879 g/kg之间,在水土质量比约为2500时,NH₄+-N释放量达到最大,随后释放逐渐趋于平衡. 洱海沉积物NH₄+-N释放潜能及最大释放量均与其w(TN)呈显著正相关. 洱海沉积物中w(TN)与NH₄+-N释放潜能和最大释放量均高于长江中下游湖泊,具有较大的氮释放风险. 

Studying on Total Nitrogen Content and Release Characteristics of Ammonium in the Surface Sediment of Erhai Lake

The distribution status and release characteristics of nitrogen were investigated by studying on release kinetics characteristics and release potential ability change of the total nitrogen content and ammonia nitrogen (NH₄+-N) for nine sediment samples collected from Erhai Lake. The results indicated that the total nitrogen content in the sediments varied from 2.0844to 6.5153g/kg with the mean value of 3.5378g/kg. The area with the highest total nitrogen is located in the west bank of the north section and the second high area is located in the south part near Dali City. The release kinetics of NH₄+-N in the sediment surface was well simulated by the first-order kinetic equation. The greatest amount of the released NH₄+-N was between 0.1209and 0.2810g/kg. The release process of NH₄+-N was mainly occurred within the first five minutes and its amount was accounted for 68%-83% of the greatest amount. After 120minutes, this release process was gradually reached to its balance. The release potential ability of NH₄+-N was between 1.7001and 3.5879g/kg, and the release potential ability of NH₄+-N reached to the maximum value, when the ratio of water and soil approximately was 2500∶1. The total nitrogen content, the release potential ability of NH₄+-N and the greatest amount of NH₄+-N reached in sediment samples of Erhai Lake were higher than that of the sediments from the lakes in the middle and lower reaches of the Yangtze River region. This result indicated that the sediments from Erhai Lake had a risk of nitrogen release greater than those from the lakes in the middle and lower reaches of the Yangtze River region.