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Incomplete combustion processes lead to the formation of many gaseous byproducts that can be challenging to monitor in flue gas released via chimneys. This study presents ground-based remote sensing approaches to make greenhouse gas (GHG) flux measurements of methane (CH 4 ) and nitrous oxide (N 2 O) from a waste incineration chimney at distances of 150–200 m. The study found emission of N 2 O (corresponding to 30–40 t yr −1 ), which is a consequence of adding the reduction agent urea to decrease NO X emissions due to NO X regulation; a procedure that instead increases N 2 O emissions (which is approximately 300 times more potent as a GHG than CO 2 on a 100-year time scale). CH 4 emissions of 7–11 t yr −1 was also detected from the studied chimney despite the usage of a high incineration temperature. For this particular plant, local knowledge is high and emission estimates at corresponding levels have been reported previously. However, emissions of CH 4 are often not included in GHG emission inventories for waste incineration. This study highlights the importance of monitoring combustion processes, and shows the possibility of surveying CH 4 and N 2 O emissions from waste incineration at distances of several hundred meters. [ABSTRACT FROM AUTHOR]

The calibration and validation of remote sensing land cover products are highly dependent on accurate field reference data, which are costly and practically challenging to collect. We describe an optical method for collection of field reference data that is a fast, cost-efficient, and robust alternative to field surveys and UAV imaging. A lightweight, waterproof, remote-controlled RGB camera (GoPro HERO4 Silver, GoPro Inc.) was used to take wideangle images from 3.1 to 4.5m in altitude using an extendable monopod, as well as representative near-ground (< 1 m) images to identify spectral and structural features that correspond to various land covers in present lighting conditions. A semi-automatic classification was made based on six surface types (graminoids, water, shrubs, dry moss, wet moss, and rock). The method enables collection of detailed field reference data, which is critical in many remote sensing applications, such as satellite-based wetland mapping. The method uses common non-expensive equipment, does not require special skills or training, and is facilitated by a step-bystep manual that is included in the Supplement. Over time a global ground cover database can be built that can be used as reference data for studies of non-forested wetlands from satellites such as Sentinel 1 and 2 (10m pixel size). [ABSTRACT FROM AUTHOR]

Methane (CH 4 ) and nitrous oxide (N 2 O) are two very potent greenhouse gases, with highly heterogeneous distributions in both space and time. Mapping hot-spots and source areas, and measuring fluxes in different environments has so far not been possible on a local scale using direct measurements. We have developed a method for simultaneous mapping of methane (CH 4 ) and nitrous oxide (N 2 O), also including water vapor (H 2 O), using ground-based remote sensing on a landscape-sized scale by utilizing Imaging Fourier Transform Spectrometers (IFTS) with high spectral resolution and imaging rates. The approach uses calculated libraries of transmission spectra at the spectroscopic resolutions of the IFTS, based on the HITRAN database of spectroscopic lines and our own line-by-line radiative transfer model (LBLRTM). For each species, 1024 spectra have been made, resulting in 1024 3 combinations of column densities. Using an adaptive grid, solutions are found for each line of sight at a spectral resolution of up to 0.25 cm − 1 using the full spectral region of the detector. The modeling is multi-layered, calculating temperatures of the background, air, and any additional gas layers, also accounting for reflected cold sky. Background distances can be mapped from the amount of water vapor in each line of sight. The described approach can be used to identify sources, quantify gas distributions, and to calculate fluxes. Visualizations can produce gas distribution images, as well as air motion videos, which are used to map fluxes using the same data set, without the need for additional instruments for wind measurements. [ABSTRACT FROM AUTHOR]