Challenges associated with the atmospheric monitoring of areal emission sources and the need for optical remote sensing techniques—an open-path Fourier transform infrared (OP-FTIR) spectroscopy experience report

In recent years, OP-FTIR spectrometry has been successfully used to monitor hazardous air pollutants, greenhouse gases and other emission products. This ground-based remote sensing method has proven itself to be a flexible long-path technique for the characterization of large atmospheric volumes, enabling simultaneous detection of various volatile atmospheric compounds relevant for environmental assessment via a single rapid measurement. Within our research, we applied both active and passive ground-based OP-FTIR spectroscopy as a screening tool for the detection of fugitive greenhouse gas emissions. The method was proven as offering a suitable ‘compliance toolbox’ for continuous monitoring of the complex systems at the ground surface–atmosphere boundary, allowing large-scale identification and quantification of atmospheric composition over large areas to be achieved, in terms of identifying zones of higher leakage vulnerability. In this paper, we compiled our research results and highlight the adaption options of the field technology, illustrated measuring options and case studies at urban, natural and industrial sites. Furthermore, this technology was validated regarding its applicability in environmental atmospheric monitoring. The results show that passive OP-FTIR measurements offer the chance to achieve robust and reliable surveys in various arbitrary measurement directions to gain a comprehensive overview. However, to improve quantitative analysis in the case of weak sources, the application of an active open-path spectrometer is recommended. It should be noted that our investigations demonstrate that site-specific parameters such as prevailing wind directions, meteorological conditions, topographic influences, infrastructure, other artificial emission sources, and biological background need to be measured both prior to and during atmospheric monitoring and should be taken into account for comprehensive interpretation.