Ship emissions of SO2 and NO2: DOAS measurements from airborne platforms
Ship emissions of SO2 and NO2: DOAS measurements from airborne platforms
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DOI：
10.5194/amt-5-1085-2012
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发表时间：
2012-01-01
影响因子：
3.8
通讯作者：
Balzani, J.
中科院分区：
文献类型：
--
作者：
Berg, N.;Mellqvist, J.;Balzani, J.
本文介绍了一种利用光学遥感测量船舶SO2和NO2气体通量的独特方法，并在可行性研究中进行了论证。该测量系统基于差分光学吸收光谱，以水面反射的天窗为光源。光栅光谱仪分别记录311 nm和440 nm左右的光谱，望远镜向下指向地平线30度角。从每个光谱中提取SO2和NO2的质量柱值，并在整个羽流中进行整合。一个简单的几何近似被用来计算光程。为了得到以kg h（-1）为单位的总辐射，将羽流的总质量乘以视风，即对应于风与航速之间矢量的稀释系数。该系统在波罗的海和卡特加特的两次可行性研究中进行了测试，2008年在CASA-212飞机上进行了测试，2009年在欧盟战役中在鹿特丹附近的北海由海豚直升机进行了测试。波罗的海22艘船舶SO2的平均排放量为（54 +/- 13）kg h(-1)， NO2的平均排放量为（33 +/- 8）kg h（-1）。在北海，21艘船舶的平均SO2排放量为（42 +/- 11）kg h(-1)，此处没有测量NO2。当使用所述方法时，该系统的检测限使得在60%的测量中检测到船舶羽流中的二氧化硫成为可能。我们在客轮上同时进行空中光学测量和船上测量，以作比较。对比结果表明，2天的测量精度分别为（-30 +/- 14）%和（-41 +/- 11）%，相同的测量精度约为20%。这说明了在不同条件下，光路的简单几何近似忽略了光在海浪中的散射和在排气羽流中的直接散射和多重散射所引起的测量不确定度。暂定误差预算表明不确定性在30-45%之间，但为了可靠的误差分析，需要对光学光路进行建模。船舶排放模型FMI-STEAM与光学测量结果进行了比较，结果显示高估了18%，相关系数（R-2）为0.6。结果表明，将光学方法与模拟功率消耗相结合，可以估计出40%以内的硫燃料含量，这将足以检测出在IMO规定区域内适用的1%和0.1%限制下运行的船舶之间的差异。
A unique methodology to measure gas fluxes of SO2 and NO2 from ships using optical remote sensing is described and demonstrated in a feasibility study. The measurement system is based on Differential Optical Absorption Spectroscopy using reflected skylight from the water surface as light source. A grating spectrometer records spectra around 311 nm and 440 nm, respectively, with the telescope pointed downward at a 30A degrees angle from the horizon. The mass column values of SO2 and NO2 are retrieved from each spectrum and integrated across the plume. A simple geometric approximation is used to calculate the optical path. To obtain the total emission in kg h(-1) the resulting total mass across the plume is multiplied with the apparent wind, i.e. a dilution factor corresponding to the vector between the wind and the ship speed. The system was tested in two feasibility studies in the Baltic Sea and Kattegat, from a CASA-212 airplane in 2008 and in the North Sea outside Rotterdam from a Dauphin helicopter in an EU campaign in 2009. In the Baltic Sea the average SO2 emission out of 22 ships was (54 +/- 13) kg h(-1), and the average NO2 emission was (33 +/- 8) kg h(-1), out of 13 ships. In the North Sea the average SO2 emission out of 21 ships was (42 +/- 11) kg h(-1), NO2 was not measured here. The detection limit of the system made it possible to detect SO2 in the ship plumes in 60% of the measurements when the described method was used.A comparison exercise was carried out by conducting airborne optical measurements on a passenger ferry in parallel with onboard measurements. The comparison shows agreement of (-30 +/- 14)% and (-41 +/- 11)%, respectively, for two days, with equal measurement precision of about 20%. This gives an idea of the measurement uncertainty caused by errors in the simple geometric approximation for the optical light path neglecting scattering of the light in ocean waves and direct and multiple scattering in the exhaust plume under various conditions. A tentative error budget indicates uncertainties within 30-45% but for a reliable error analysis the optical light path needs to be modelled.A ship emission model, FMI-STEAM, has been compared to the optical measurements showing an 18% overestimation and a correlation coefficient (R-2) of 0.6. It is shown that a combination of the optical method with modelled power consumption can estimate the sulphur fuel content within 40%, which would be sufficient to detect the difference between ships running at 1% and at 0.1%, limits applicable within the IMO regulated areas.