Direct measurement of greenhouse gas exchange in urban ecosystems

这项研究计划将开发测量、量化和分析城市温室气体(GHG)排放的方法。直接量化社区或土地使用区规模的二氧化碳、甲烷、一氧化二氮排放量。在这些尺度上，大多数规划决策都是做出的，估计排放量(根据消费统计数据或通过建模汇总)与很大的不确定性有关。缺乏独立验证模拟排放的现场方法和数据。 我们将使用(I)城市地面上方高塔上温室气体的质量通量测量，(Ii)使用城市绿地上方的密闭室对温室气体排放进行采样，以及(Iii)使用稳定同位素来划分选定的排放和浓度测量。我们将量化不确定的扩散源(和汇)的贡献，特别是城市土壤和植被的交换。该计划将使用不列颠哥伦比亚省温哥华现有的30米研究塔、现有的激光光谱分析系统和表面特征的遥感数据，以解决以下限制和知识差距： (A)目前，对二氧化碳排放量的直接测量仅限于城市地区所有来源和汇的净交换(即建筑排放+交通排放+呼吸-光合作用)。因此，不可能对特定部门的模型进行验证。我们将使用二氧化碳稳定同位素的直接流量和浓度测量，将净交换分离到不同来源的单独排放谱中(天然气、汽油和呼吸的同位素特征不同)。 (B)我们将量化与城市土地使用有关的温室气体扩散源和汇在加拿大城市中是否相关。具体地说，政府间气候变化专门委员会的《国家温室气体清单指南》认为，缺乏估算定居点CH4和N2O排放量的方法是一个“明显的”知识差距。我们将测量主要由土地覆盖(草坪、土壤)和燃烧引起的CH4和N2O排放(和吸收)。我们将量化排放、确定污染源的属性并确定控制措施。

This research program will develop methods to measure, quantify and analyze emissions of greenhouse-gases (GHG) in cities. We will directly quantify emissions of carbon-dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at scales of neighborhoods or land-use zones. At those scales, where most planning decisions are made, estimated emissions (from consumption statistics or aggregated by modeling) are associated with large uncertainties. There is a lack of in-situ methods and data to independently validate modelled emissions. We will use (i) mass flux measurements of GHGs on towers above urban surfaces, (ii) sample GHG emissions using closed-chambers over urban green-space, and (iii) use stable isotopes to partition selected emission and concentration measurements. We will quantify the contribution of uncertain diffuse sources (and sinks), in particular exchange by urban soils and vegetation. The program will use an existing 30 m research tower in Vancouver, BC, an existing laser spectroscopy system, and remotely sensed data of surface characteristics to address the following limitations and knowledge gaps: (A) Currently, direct measurements of CO2 emissions are limited to the net-exchange from all sources and sinks in an urban area (i.e. building emissions + transportation emissions + respiration - photosynthesis). Hence, a validation of sector-specific models is not possible. We will use direct flux and concentration measurements of stable isotopologues of CO2 to separate net-exchange into individual emission profiles of various sources (isotopic signatures differ for natural gas, gasoline and respiration). (B) We will quantify whether diffuse GHG sources and sinks related to urban land-use are relevant or not in Canadian cities. Specifically, the IPCC Guidelines for National Greenhouse Gas Inventories identify the lack of a methodology for estimating emissions of CH4 and N2O from settlements as an 'obvious' knowledge gap. We will measure CH4 and N2O emissions (and uptake) caused by primarily land-cover (lawns, soils), but also combustion. We will quantify emissions, attribute sources and determine controls.