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A Portable Laser Spectroscopic System for Measuring Nitrous Oxide Emissions on Fertilized Cropland

In July of 2023 researchers from the Fraunhofer Institute for Physical Measurement Techniques IPM and Laboratory for Gas Sensors, Germany, published in Sensors, MDPI, an article where they describe a portable laser spectroscopic system for measuring nitrous oxide emissions on fertilized cropland containing a VIGO Photonics photodetector. 

Nitrous oxide (laughing gas, NO) is produced by plants after nitrogen fertilization. This gas is a relevant greenhouse gas. As nitrogen fertilization has been identified as one of the main sources of NO, controlled application and reduction of the amount of fertilizer adapted to crop demand is essential to reduce NO emissions. That’s why the research conducted on this topic is so important.

Researchers build two setups: laboratory and portable system. In both, they used a three-stage thermoelectrically cooled MCT (Mercury Cadmium Telluride) VIGO detector. NO in air was detected via tunable diode laser absorption spectroscopy (TDLAS). The authors used QCL (quantum-cascade lasers) with an emission wavelength of 4.5 µm in the laboratory system and energy-saving ICL (interband cascade laser) with an emission wavelength of 4.524 µm in the portable setup as a light source. A multi-reflection long-path cell with an optical path length of 720 cm was used in both setups.

During measurements using VIGO Photonics detectors, scientists have achieved an absolute measurement uncertainty of ±1 ppb due to the reference concentration (333 ppb as a reference) leading to a relative measurement uncertainty of the NO concentration of almost 0.3%. The standard deviation is about 0.2 ppb for the laboratory setup and about 8 ppb for the portable setup.

In the described article setups containing VIGO Photonics three-stage thermoelectrically cooled MCT detectors enabled measurements of NO concentration of the collected gas from the croplands and determination of NO flux diffusing out of the soil. We are pleased that VIGO’s equipment supports work on reducing greenhouse gases.

Link to the article