CO2 and O2 respiration kinetics in hydrocarbon contaminated soils amended with organic carbon sources used to determine catabolic diversity.

Multiple substrate induced respiration (MSIR) assays which assess the response of soils to carbon source amendment are effective approaches to determine catabolic diversity of soils. Many assays are based on a single short term (<6 h) time point measurement and usually limited to CO₂ production only. However, repeated measurements of both CO₂ and O₂ simultaneously can provide additional valuable information. In this study, a MSIR assay involving eight carbon sources was applied to three hydrocarbon contaminated soils using continuous CO₂ and O₂ respiration measurements. Based on cumulative CO₂ and O₂ measurements at 4, 24 and 120 h, the soils were found to be distinct in terms of their catabolic diversity. Most noteworthy, however, was the response to the addition of maleic acid which provided strong evidence of abiotic CO₂ efflux to be the overriding process, raising questions about the interpretation of CO₂ only responses from organic acid addition in MSIR assays. [Copyright &y& Elsevier]