ABSTRACT

Concepts of material flow and mass consistency of nitrogen compounds have been used to elucidate nitrogen’s fate in an urban environment. While reactive nitrogen commonly is associated to agriculture and hence to large areas, here we have compiled scientific literature on nitrogen budget approaches in cities, following the central role cities have in anthropogenic activities generally. This included studies that specifically dealt with individual sectors as well as budgets covering all inputs and outputs to and from a city across all sectors and media. In the available data set, a clear focus on Asian cities was noted, making full use of limited information and thus enable to quantitatively describe a local pollution situation. Time series comparisons helped to identify trends, but comparison between cities was hampered by a lack of harmonized methodologies. Some standardization, or at least improved reference to relevant standardized data collection along international norms was considered helpful. Analysis of results available pointed to the following aspects that would reveal additional benchmarks for urban nitrogen budgets: analysing the share of nitrogen that is recycled or reused, separating largely independent sets of nitrogen flows specifically between food nitrogen streams and fossil fuel combustion-related flows, and estimating the stock changes for the whole domain or within individual pools.

摘要

氮化合物的物质流动和质量一致性的概念已被用来阐明城市环境中氮的命运。尽管反应性氮通常与农业有关，因此与大片地区有关，但在这里，我们根据城市在人为活动中的核心作用，汇编了有关城市氮预算方法的科学文献。这包括专门针对各个部门的研究以及涵盖所有部门和媒体进出城市的所有投入和产出的预算。在现有的数据集中，我们注意到了对亚洲城市的明确关注，充分利用了有限的信息，从而能够定量描述当地的污染状况。时间序列比较有助于确定趋势，但是城市之间的比较因缺乏统一的方法而受阻。一些标准化，或者至少是沿国际准则对相关标准化数据收集的改进参考，被认为是有帮助的。对现有结果的分析指出了以下方面，这些方面将揭示城市氮预算的其他基准：分析回收或再利用的氮的份额，将很大程度上独立的氮流分离开，特别是在食物氮流和化石燃料燃烧相关流之间，并估算整个域或单个池中的库存变化。