Cost-efficient approaches to measure carbon dioxide (CO2) under different environmental factors such as temperature and humidity using mini loggers

• Main Author: Lander, Jasmine
• Format: Others
• Language: English
• Published: Linköpings universitet, Institutionen för tema 2020
• Subjects: Mini logger; CO2 sensor; CO2 measuring device; carbon dioxide; greenhouse gas; Natural Sciences; Naturvetenskap
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165993

Fluxes of carbon dioxide (CO2), being a major greenhouse gas, are of great importance to understand and monitor. Findings have shown that while CO2 emissions enhanced by humans triggered the greenhouse gas effect, several significant CO2 fluxes in nature that are climate sensitive may still be poorly constrained, especially those from inland waters and its surrounding soils and sediments. This including different processes such as decomposers degrading organic material. At present, direct measurements of CO2 from soils, waters or CO2 concentrations in surface water, are typically labour intensive or require costly equipment. Therefore, small inexpensive CO2 mini loggers, originally made for indoor air quality monitoring, are for this project being developed further for field use, as a convenient equipment to measure CO2 emissions. However, a requirement is that the mini loggers are stable and robust against interference by other air components, including water vapour, and physical factors such as temperature. Therefore, the mini loggers were for this project studied further under different environmental conditions such as temperature and humidity in a controlled environment. The results were analysed using multiple regression analysis where the CO2 concentration (CO2), measured by the LGR instrument, versus the logger IR signal (IR), temperature (T) and relative humidity (RH) were studied. Unlike some previous studies, this project studied a large CO2 concentration interval (400 – 10 000 ppm).  The results show that there was a strong regression for IR versus CO2. The regression for both RH and the T was on the other hand very weak. However, there were factors that could have affected the mini logger. This since it was noticed that the mini loggers’ ability to calculate the CO2 concentration was worsened when the humidity was increased during the experiments. It is believed that the cause was condensed water, gathering in the inner parts of the mini logger. This because the sensor chamber had a lower temperature than the hot air entering the sensor chamber from the humidity bottle, together with the CO2, leading to condensation. Hence, prevention of condensation inside the measurement cell is important. However, the results from the analysis shows that the factors; RH and T do not need to be taken into account when studying the CO2 concentration over a larger interval, as long as the conditions are not condensing.