Reliability of the Soil Gas Profiles Measured with a Multilevel Soil Air Sampler

Abstract

The soil air samplers used in previous studies were mainly designed to collect soil gases at only a single depth. In this study, we developed a simplified multilevel sampler for extracting soil air at several depths with a single probe. Its applicability was investigated by comparison with a single-level sampler previously used and by the theoretical and practical evaluation of the reliability of the measured profiles of carbon dioxide in soil air under natural soil conditions. The profiles of carbon dioxide obtained with both types of samplers were basically the same, while the homogeneity of the extracted soil air was verified by a continuously duplicated half-volume extraction. The knotted structure of the multilevel sampler apparently controlled preferential airflow along the sampler shaft without the use of any filling substances, while the spherical distributions of the extracted soil air, which were simply evaluated from the air-filled porosity and did not overlap with each other, theoretically supported the reliability of the measured profiles. The multilevel soil air sampling provides for the installation of fewer samplers, less soil disturbance, and provides more accurate soil gas profiles compared to the previous methods.