Baltic Sea Centre, Stockholm University, 106 91 Stockholm, Sweden.
Baltic Sea Centre, Stockholm University, 106 91 Stockholm, Sweden.
J Environ Manage. 2024 Nov;370:122478. doi: 10.1016/j.jenvman.2024.122478. Epub 2024 Sep 19.
We have constructed a nutrient fate model for the Baltic Sea that links anthropogenic nitrogen and phosphorus inputs to the catchment to the dynamics of waterborne loads to the Baltic Sea, covering the time-period from 1900 to present. During this period, nutrient inputs to the drainage basin approximately tripled to a peak in the 1980s, after which they declined. Our model accounts for temporary nutrient storage on land and in inland waters, forming active legacy pools that contribute to nutrient export to the Baltic Sea, and for nutrient removal by terrestrial and aquatic sinks. The model indicates that response times to changes in anthropogenic nutrient inputs to the drainage basin are approximately 4 years for riverine nitrogen and 6-18 years for riverine phosphorus loads. Mineral fertilizer use in agriculture dominates nutrient inputs to the drainage basin, whereas the composition of riverine loads also depends on the collection and treatment of domestic sewage. Removal by terrestrial and aquatic nutrient sinks was the dominant fate of both nitrogen and phosphorus in our model. The amount of nutrients currently stored in legacy pools is therefore much smaller than what the difference between cumulative nutrient inputs to the catchment and the export to the sea suggests. Nevertheless, mobilization from these storage pools is the primary contribution to current anthropogenic riverine nutrient loads to the Baltic Sea. For phosphorus, the legacy effects of past reductions in inputs to the catchment can entail a significant, yet unrealized contribution toward the load reductions stipulated by Baltic Sea management plans. Therefore, accounting for nutrient storage, time-lags, and legacy effects could notably reduce the need for additional future mitigation measures.
我们构建了一个波罗的海养分命运模型，将人为输入的氮和磷与流域汇水的水载负荷动态联系起来，涵盖了从 1900 年至今的时间段。在此期间，营养物质输入流域的量增加了两倍多，达到了 20 世纪 80 年代的峰值，之后开始下降。我们的模型考虑了陆地上和内陆水中暂时储存的养分，形成了活跃的遗留养分库，这些库有助于养分向波罗的海的输出，以及陆地和水生汇的养分去除。该模型表明，流域人为养分输入变化的响应时间大约为 4 年，对河流氮的影响，6-18 年对河流磷的影响。农业中矿物肥料的使用主导着流域的养分输入，而河流负荷的组成也取决于城市污水的收集和处理。陆地和水生养分汇的去除是我们模型中氮和磷的主要归宿。目前，储存在遗留库中的养分量远小于流域养分输入与海洋输出之间的差值所表明的数量。尽管如此，从这些储存库中释放出来的养分仍然是当前人为向波罗的海河流输入养分负荷的主要贡献因素。对于磷来说，过去减少输入流域的遗留效应可能会对波罗的海管理计划规定的负荷减少产生显著但尚未实现的贡献。因此，考虑养分储存、时滞和遗留效应可以显著减少未来额外缓解措施的需求。
