摘要
自20世纪60年代以来,人们一直在研究随着输入的减少韦特恩湖、维纳恩湖、梅拉伦湖以及哈马伦湖中磷(P)和氮(N)的浓度变化。在前两个水更新速度较慢的深水、贫营养湖中,自70年代以来磷输入的急剧减少只是造成较长一段时间内磷浓度的少量减小。同时在水团中出现了非有机氮的积累现象,本文对这一现象的可能原因进行了探讨。在后两个中等营养到高营养的湖中,哈马伦湖中的两个浅盆地由于沉积物释放的氮而显示出恢复较慢。这两个盆地以及梅拉伦湖中的两个盆地有氮缺乏现象,特别是在磷输入减少之前的数年中,而且表明存在固氮现象。在梅拉伦湖的两个盆地中,湖内磷浓度的恢复与用于湖泊从营养物污染中恢复的IMSA模型相比较预期的要好。在其他的5个湖泊/盆地中,20年之后的叶绿素浓度与那些模拟的情况相比类似。
In-lake concentration changes of phosphorus (P) and nitrogen (N) in lakes Vattern, Vanern, Malaren, and Hjalmaren in response to diminished input has been examined from the mid-1960s onwards. In the former two deep and oligotrophic lakes with slow water renewal, drastic reductions in P-input from the middle of 1970s caused just minor reductions in P-concentration over a very long time. At the same time accumulation occurred in the water mass of inorganic N and possible reasons are discussed. In the latter two mesotrophic to hypertrophic lakes, two shallow basins in L. Hjalmaren showed slow recovery due to release of P from sediments. The same basins and two basins in L. Malaren have suffered from N-deficiency, particularly during the pre-phosphorus reduction years, and nitrogen fixation was indicated. In two L. Malaren basins recovery of in-lake P concentrations was better than expected in comparison to the so-called IMSA-model for lake recovery from nutrient pollution. In the other five lakes/basins chlorophyll concentrations after 20 years were similar compared to those modeled.
