Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Chalmers University of Technology/FluxSense AB, SE-41296 Göteborg, Sweden.
Waste Manag. 2014 Aug;34(8):1416-28. doi: 10.1016/j.wasman.2014.03.025. Epub 2014 Apr 20.
Using a dual species methane/acetylene instrument based on cavity ring down spectroscopy (CRDS), the dynamic plume tracer dispersion method for quantifying the emission rate of methane was successfully tested in four measurement campaigns: (1) controlled methane and trace gas release with different trace gas configurations, (2) landfill with unknown emission source locations, (3) landfill with closely located emission sources, and (4) comparing with an Fourier transform infrared spectroscopy (FTIR) instrument using multiple trace gasses for source separation. The new real-time, high precision instrument can measure methane plumes more than 1.2 km away from small sources (about 5 kg h(-1)) in urban areas with a measurement frequency allowing plume crossing at normal driving speed. The method can be used for quantification of total methane emissions from diffuse area sources down to 1 kg per hour and can be used to quantify individual sources with the right choice of wind direction and road distance. The placement of the trace gas is important for obtaining correct quantification and uncertainty of up to 36% can be incurred when the trace gas is not co-located with the methane source. Measurements made at greater distances are less sensitive to errors in trace gas placement and model calculations showed an uncertainty of less than 5% in both urban and open-country for placing the trace gas 100 m from the source, when measurements were done more than 3 km away. Using the ratio of the integrated plume concentrations of tracer gas and methane gives the most reliable results for measurements at various distances to the source, compared to the ratio of the highest concentration in the plume, the direct concentration ratio and using a Gaussian plume model. Under suitable weather and road conditions, the CRDS system can quantify the emission from different sources located close to each other using only one kind of trace gas due to the high time resolution, while the FTIR system can measure multiple trace gasses but with a lower time resolution.
利用基于腔衰荡光谱（CRDS）的双物种甲烷/乙炔仪器，成功地在四个测量活动中测试了用于量化甲烷排放率的动态羽流示踪剂扩散方法：（1）具有不同示踪气体配置的受控甲烷和痕量气体释放，（2）具有未知排放源位置的垃圾填埋场，（3）具有紧密相邻排放源的垃圾填埋场，以及（4）使用多种示踪气体进行源分离与傅里叶变换红外光谱（FTIR）仪器进行比较。新型实时、高精度仪器可以测量距离小型源（约 5 公斤/小时）超过 1.2 公里的甲烷羽流，测量频率允许以正常行驶速度穿过羽流。该方法可用于量化扩散面积源的总甲烷排放量，低至每小时 1 公斤，并且可以通过选择正确的风向和道路距离来量化单个源。示踪气体的放置对于获得正确的定量很重要，如果示踪气体与甲烷源不同时定位，可能会导致高达 36%的不确定性。在更远的距离进行测量对示踪气体放置的误差不敏感，并且当测量距离超过 3 公里时，模型计算显示在城市和开阔地区，当将示踪气体放置在距离源 100 米处时，不确定性小于 5%。与在羽流中最高浓度、直接浓度比和使用高斯羽流模型相比，在不同距离处测量时，使用示踪气体和甲烷的积分羽流浓度比可以获得最可靠的结果。在适当的天气和道路条件下，CRDS 系统可以使用仅一种示踪气体来量化彼此靠近的不同源的排放，因为它具有高时间分辨率，而 FTIR 系统可以测量多种示踪气体，但时间分辨率较低。
