Ideris, Alan J (Atmospheric Science, University of California, Atmospheric Science, Univ. of California, One Shields Ave., Davis, CA, 95616; Phone: 530-752-1868; Fax: 530-752-1793; Email: ajideris@ucdavis.edu)

Pressure pumping effects on soil efflux measurements of CO₂

Alan Joseph Ideris *, K. T. Paw U, John Kochendorfer, Liyi Xu

Carbon Dioxide is the major trace gas responsible for predicted global climate change. Anthropogenic CO₂ is believed to be the major constituent to the steady rise in the mean CO₂, which has been rising more rapidly than the biometeorological system has experienced in recent geological history. The approach of measuring the soil CO₂ efflux due to pressure pumping will give us a better understanding of the soil-atmosphere interfacial, which will consequently allow for better development of instrumentation, measurement techniques, and adequate theoretical equations. In our study, we measured the barometric pressure (10 Hz) at depths of 40cm, 20 cm, 10 cm, and the surface by use of fast response pressure transducers and examined a possible relationship with the amount of soil CO₂ efflux from the total net ecosystem exchange. The soil CO₂ efflux was measured by use of an eddy-covariance system composed of a sonic anemometer and Licor-7500 infrared CO₂ and H₂O gas analyzer. In addition, coefficients for pressure attenuation with depth have been determined. We report on the relationship between pressure measurements and soil CO₂ efflux, which could have several implications. Such implications include improving measurement techniques and instrumentation by accounting for some of the errors associated with using soil chambers to measure CO₂ efflux.