Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK
Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK
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DOI：
10.5194/acp-16-10543-2016
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发表时间：
2016-08-24
影响因子：
6.3
通讯作者：
Nemitz, Eiko
中科院分区：
文献类型：
--
作者：
Helfter, Carole;Tremper, Anja H.;Nemitz, Eiko
本文报道了在英国伦敦中心用涡动协方差法对甲烷（CH 4）、一氧化碳（CO）和二氧化碳（CO 2）通量进行的3年多的测量结果。2012-2014年期间CO2年平均排放量（39.1 +/- 2.4千吨km（-2）yr（-1））和（89 +/- 16吨/平方公里/年）（分别在1%和5%以内），数值来自伦敦大气排放清单，但测得的甲烷排放量（72 +/- 3吨km（2）yr（-1））比清单值大两倍多。季节性变化是大的CO与冬季到夏季减少69%，每月通量强烈反相关的平均气温。冬季CO排放量的增加主要归因于车辆冷启动和燃料燃烧效率降低。冬季CO2通量比夏季高33%，与平均气温反相关，尽管程度低于CO。这是由于冬季对天然气供暖的需求增加。CH 4通量表现出温和的季节性（21%以上的冬季），和空间变化的线性反相关与空气温度。通量足迹内的居民人口的差异解释了高达90%的空间变异的年度CO2通量和高达99%的CH 4。此外，我们认为，生物源的CH 4，如废水，这是不占的大气排放清单，作出了重大贡献的整体预算和通勤动态进出中央商务区可以解释一些空间和时间的变化CO2和CH 4排放。据我们所知，这项研究是独特的，因为所提供的数据集的长度，特别是CO和CH 4通量。这项研究提供了一个独立的评估“自下而上”的排放清单，并表明，城市来源的CO和CO2的特点是在伦敦。然而，CH 4排放量的情况并非如此，清单办法严重低估了CH 4排放量。我们的研究结果和其他人指出，在英国和国外的机会，以确定和量化城市甲烷的“失踪”的来源，修改排放清单的方法，并制定这种强大的温室气体减排战略。
We report on more than 3 years of measurements of fluxes of methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) taken by eddy-covariance in central London, UK. Mean annual emissions of CO2 in the period 2012-2014 (39.1 +/- 2.4 ktons km(-2) yr(-1)) and CO (89 +/- 16 tons km 2 yr(-1)) were consistent (within 1 and 5% respectively) with values from the London Atmospheric Emissions Inventory, but measured CH4 emissions (72 +/- 3 tons km(2) yr(-1) were over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69 %, and monthly fluxes were strongly anti-correlated with mean air temperature. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33% higher in winter than in summer and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. CH4 fluxes exhibited moderate seasonality (21% larger in winter), and a spatially variable linear anti-correlation with air temperature. Differences in resident population within the flux footprint explained up to 90% of the spatial variability of the annual CO2 fluxes and up to 99% for CH4. Furthermore, we suggest that biogenic sources of CH4, such as wastewater, which is unaccounted for by the atmospheric emissions inventories, make a substantial contribution to the overall budget and that commuting dynamics in and out of central business districts could explain some of the spatial and temporal variability of CO2 and CH4 emissions. To our knowledge, this study is unique given the length of the data sets presented, especially for CO and CH4 fluxes. This study offers an independent assessment of "bottom-up" emissions inventories and demonstrates that the urban sources of CO and CO2 are well characterized in London. This is however not the case for CH4 emissions which are heavily underestimated by the inventory approach. Our results and others point to opportunities in the UK and abroad to identify and quantify the "missing" sources of urban methane, revise the methodologies of the emission inventories and devise emission reduction strategies for this potent greenhouse gas.