Urban nitrogen biogeochemistry

城市化是全球变化中最显著的组成部分之一。在加拿大，城市人口超过80%，而在安大略，这一比例甚至更高（85%），预计未来几乎所有的人口增长都将主要通过“郊区化”过程或在城市外围的扩张而发生在城市地区。虽然从本地到农业土地利用的变化的地球化学影响已经得到了很好的研究，转换为城市土地利用的影响得到了相对较少的研究关注。特别值得关注的是城市土地利用变化对氮素地球化学的影响。氮的输入和输出在城市系统中的自然土地利用类型相比，大大修改和N的保留往往是减少在城市河流，由于他们的“flasperous”水文，减少水力停留时间和改变河岸带连接。相反，一些独特的热点氮储存和反硝化可能存在于城市地区，包括草坪，雨水滞留池和路边沟渠。这项研究计划的长期目标是评估土地利用变化对加拿大人口最多的地区--安大略南部城市化流域内生态地球化学循环的影响。这项为期5年的研究计划将集中在土地利用变化对氮（N）循环在南部安大略大都市区的影响。具体而言，本建议的短期目标是（a）调查N循环沿着城市-郊区-农村边缘梯度;（B）表征热点（即雨水池塘，草坪和路边沟渠）的N循环，（c）量化N释放在炎热的时刻（风暴和春季融化）沿着梯度。这些短期目标将通过1个博士，3个硕士来实现。和4个本科生荣誉论文项目，结合城市梯度，补丁动态和小流域（质量平衡）的方法联合收割机。

Urbanization is one of the most conspicuous components of global change. In Canada, the urban population exceeds 80%, whereas the proportion is even higher in Ontario (85%) and virtually all future population growth is expected to occur in urban areas primarily through the process of 'suburbanization', or expansion at their outer margins. While the biogeochemical impacts of changes from native to agricultural land-use have been well studied, the effect of conversion to urban land use has received relatively little research attention. Of particular concern, is the effect of urban land use change on N biogeochemistry. Nitrogen inputs and outputs are greatly modified in urban systems compared with natural land use types and N retention is often reduced in urban streams due to their 'flashier' hydrology, reduced hydraulic residence times and altered riparian zone connections. Conversely, a number of unique hotspots for N storage and denitrification may exist in urban areas, including lawns, storm water detention ponds and roadside ditches. The long-term goal of this research program is to evaluate the impacts of land use change on biogeochemical cycling within urbanizing watersheds in southern Ontario - the most populated region in Canada. This 5-year research program will focus on the impacts of landuse change on nitrogen (N) cycling in a southern Ontario metropolitan area. Specifically, the short-term objectives of this proposal are to (a) investigate N cycling along an urban-suburban-rural edge gradient; (b) characterize the hot spots (i.e. storm water ponds, lawns and roadside ditches) of N cycling and, (c) quantify N release during hot moments (storms and spring melt) along the gradient. These short-term objectives will be met through 1 PhD, 3 MSc. and 4 undergraduate Honours thesis projects that combine the urban gradient, patch dynamic and small catchment (mass balance) approaches.