沱江流域沉积物中氮赋存状态及其垂向分布特征

Nitrogen Species and Vertical Distribution Characteristics in the Sediment of the Tuo River

2004年2月发生在沱江的特大水污染事故给沱江流域的生态环境造成了严重的危害,近年来受工农业和沿岸居民生活的影响,沱江的生态环境依然遭受着一定程度的污染,但对沱江流域氮的地球化学研究甚少。沉积物是水环境中污染元素的重要蓄积库或释放源,为揭示沉积物中氮赋存状态迁移转化特征,并评估该地区生态环境修复状况,本文参照Mackin应用的沉积物中吸附态氨氮提取方法和Smart建立的沉积物中总氮提取方法,采用分光光度法针对沱江流域金堂地区冬季沉积物,开展了河流沉积物中总氮(TN)、可交换态氨氮(AN)、有机氮(ON)赋存状态分析,并对比了十年前后该地沉积物中氮赋存状态的变化情况。实验结果表明:TN含量为518.913~4386.899 mg/kg,ON含量为101.531~3793.683 mg/kg。在-3 cm以上,TN和ON含量较高,且ON是TN的主要组成部分;随着深度增加,两者含量迅速减少,AN含量略有降低。与十年前该地区沉积物中氮的相关数据对比,TN含量增加,其中AN含量增加明显;在-3 cm以上,ON、TN在表层沉积物中增加明显。研究认为:沱江流域沉积物中的氮已经作为内源氮释放至间隙水甚至上覆水中,同时存在外源污染,致使沉积物表层有机氮以及总氮含量升高明显。

BACKGROUND： The serious water pollution accident that occurred in the Tuo River in February 2004 caused serious harm to the ecological environment. In recent years, the ecological environment of the Tuo River has suffered from some degrees of pollution through industrial,agricultural and the life of coastal residents,but the geochemical study of nitrogen in the Tuo River is scarce.OBJECTIVES： To reveal the vertical distribution and temporal and spatial variation characteristics of nitrogen in river sediments and assess the ecological restoration in the area by analyzing the total nitrogen（ TN）,exchangeable ammonia nitrogen（ AN） and organic nitrogen（ ON） in the winter sediments of the Jintang Section of the Tuo River and to compare the results with the records of nitrogen species in the same sediments 10 years ago.METHODS： Based on the method of Mackin＇s extraction method of adsorbed ammonia nitrogen in sediments and Smart＇s method for total nitrogen extraction in sediments,spectrophotometry is used to analyze the occurrence of TN,AN and ON in winter sediments in the Jintang area of the Lancang River Basin.RESULTS： The concentrations of TN range from 518. 913 to 4386. 899 mg/kg,whereas ON range from 101. 531 to3793. 683 mg/kg. The concentrations of TN and ON were above-3 cm,and ON was the main form of TN. With the increased depth,the concentrations of TN and ON decreased rapidly,and the concentrations of AN decreased slightly.A comparison between the results of nitrogen species in sediments and the records of 10 years ago shows that the concentration of AN increased significantly and the concentrations of ON and TN increased significantly above-3 cm.CONCLUSIONS： The nitrogen in the sediments of the Tuo River had been released upward to the porewaters and even overlying waters as endogenous nitrogen. Combined with external pollution in this area,the concentrations of ON and TN in the surface of the sediment have increased significantly.