A Temperature Gradient Field Compensation Method to Improve the Accuracy of the CO2 Carbon Isotope Sensor

Abstract

Accurate measurement of carbon isotope abundance is extremely important for geochemical applications. In the seismic zone, measurement error caused by variable gas temperature must be compensated. In this study, a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> carbon isotope abundance sensor using temperature gradient field compensation (TGFC) method is investigated to improve the accuracy of isotope abundance measurement. The theoretical model of sensor is combined with TGFC method to provide a theoretical method for compensating the errors caused by temperature gradient field. When measuring isotopic abundance using the TGFC method, the reference temperature gradient field of the measured gas is obtained through heat transfer analysis and indirect measurement. The reference temperature gradient field of the measured gas is obtained through heat transfer analysis and indirect measurement for sensor measurement using TGFC method. The error of the sensor in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta ^{13}\text{C}$ </tex-math></inline-formula> (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is 0.183‰. Two days of tests are conducted to verify the sensor’s performance at the Fengman seismic station. The results validate the ability of the sensor to measure gas isotope abundances in seismic regions for geochemical analysis.