Direct Measurement of Oxygen Profiles and Denitrification Rates in Soil Aggregates

作者：Alan J. Sexstone, Niels Peter Revsbech, Timothy B. Parkin, James M. Tiedje · 发表于：Soil Science Society of America Journal · 年份：1985 · DOI：10.2136/sssaj1985.03615995004900030024x · 被引用次数：734 · 研究领域：Groundwater flow and contamination studies、Urban Stormwater Management Solutions、Wastewater Treatment and Nitrogen Removal

Abstract An oxygen microelectrode was modified to measure O 2 concentrations in wet aggregates of a silt loam soil. The microelectrode tip had an O 2 ‐permeable membrane opening 3 µm in diameter, and O 2 measurements could be made in as little as 0.1‐mm increments to a depth of 12 mm. When aggregates were incubated in air, steep O 2 gradients usually occurred over very small distances from the aggregate surface. The smallest aggregate exhibiting an anaerobic center had a radius of 4 mm, although small aggregates (radius ≤ 6 mm) were generally oxic. Larger aggregates (radius ≥ 10 mm) often had measureable anaerobic centers, with the exception of those from a native prairie soil which exhibited irregular O 2 profiles and had aerobic centers, apparently due to O 2 intrusion caused by old root channels. Oxygen profiles obtained in 45 degree increments around an aggregate circumference were used to construct contour maps of O 2 concentrations within the aggregate. Oxygen gradients were somewhat asymmetric, suggesting nonuniformly distributed sites of O 2 consumption. An average intra‐aggregate O 2 diffusion coefficient of 8.5 × 10 −6 cm 2 · s −1 was measured for water‐saturated aggregates. The radii of anaerobic centers within several aggregates, measured directly with the electrode, correlated with those calculated from a model of radial diffusion using measured respiration rates and the intra‐aggregate O 2 diffusion coefficient. Anaerobic centers were present in all aggregates t...