Ground-based imaging of NO2 emission plumes from Bełchatów Power Station using a hyperspectral camera

Nitrogen oxides (NO_x  = NO + NO₂) are atmospheric pollutants that are detrimental to air quality and human health and play a major role in tropospheric ozone chemistry. Combustion processes produce NO_x; thus, coal-fired power plants contribute significantly to the emission total (EEA 2017). Imaging atmospheric NO_xcolumns with the Differential Optical Absorption Spectroscopy (DOAS) method is a well-established tool for NO_x  emission monitoring (e.g. Lohberger 2004; Manago 2018).

During field measurements in June 2022, we deployed a ground-based hyperspectral camera (HySpex) for the visible to near-infrared (VNIR) spectral range at a distance of 6 km from the largest coal-fired power plant in Europe, the Bełchatów Power Station in Poland. We present preliminary results of NO₂  emission plume images using sky-scattered sunlight as the light source. Our HySpex VNIR-1800 hyperspectral camera records spatially highly resolved images with 2400 pixels horizontally and 1800 pixels vertically covering a 22°x16.5° field of view at a temporal resolution of ∼1 minute. The camera covers the spectral range between 400 nm and 1000 nm with a spectral resolution of ∼5 nm and sampling intervals of 3.2 nm. We retrieve pixel-wise differential slant column densities of NO₂  using DOAS in the 420 - 550 nm spectral interval. Despite the low spectral resolution, NO₂  absorption structures can be identified and fitted, as we demonstrate by lab measurements with pre-calibrated NO₂  cells.

We examine the performance of the NO₂  camera and the potential for combining it with a co-deployed carbon dioxide (CO₂) HySpex camera that operates in the shortwave-infrared spectral range. Simultaneous observations of NO₂  and CO₂  might enable insights into plume dynamics, photochemical processing in the plume and the emission ratio of the two species.

 

References:

European Environment Agency, 2017. Releases of pollutants to the environment from Europe’s industrial sector – 2015. url: https://www.eea.europa.eu /publications/releases-of-pollutants-to-the/releases-of-pollutants-from-industrial-sector (visited on 01/04/2023).

Lohberger, Falko et al.,  Aug. 2004. “Ground-based imaging differential optical absorption spectroscopy of atmospheric gases”. In: Applied Optics 43.24, p.4711. doi: 10.1364/ao.43.004711. url: https://doi.org/10.1364/ao.43.004711.

Manago, Naohiro et al.,  July 2018. “Visualizing spatial distribution of atmospheric nitrogen dioxide by means of hyperspectral imaging”. In: Applied Optics 57.21, p. 5970. doi: 10.1364/ao.57.005970. url: https://doi.org/10.1364/ao.57.005970.