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Estimating diesel degradation rates from N 2 , O 2 and CO 2 concentration versus depth data in a loamy sand
Author(s) -
Van De Steene J.,
Verplancke H.
Publication year - 2007
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2006.00813.x
Subject(s) - loam , diesel fuel , chemistry , soil water , zoology , environmental chemistry , soil science , environmental science , organic chemistry , biology
Summary The degradation rate of the pollutant is often an important parameter for designing and maintaining an active treatment system or for determining the rate of natural attenuation. A quasi‐steady‐state gas transport model based on Fick’s law with a correction term for advective flux, for estimating diesel degradation rates from N 2 , O 2 and CO 2 concentration versus depth data, was evaluated in a laboratory column study. A loamy sand was spiked with diesel fuel at 0, 1000, 5000 and 10 000 mg kg −1 soil (dry weight basis) and incubated for 15 weeks. Soil gas was sampled weekly at 6 selected depths in the columns and analysed for O 2 , CO 2 and N 2 concentrations. The agreement between the measured and the modelled concentrations was good for the untreated soil ( R 2 = 0.60) and very good for the soil spiked with 1000 mg kg −1 ( R 2 = 0.96) and 5000 mg kg −1 ( R 2 = 0.97). Oxygen consumption ranged from −0.15 to −2.25 mol O 2 m −3 soil day −1 and CO 2 production ranged from 0.20 to 2.07 mol CO 2 m −3 soil day −1 . A significantly greater mean O 2 consumption ( P < 0.001) and CO 2 production ( P < 0.005) over time was observed for the soils spiked with diesel compared with the untreated soil, which suggests biodegradation of the diesel substrate. Diesel degradation rates calculated from respiration data were 1.5–2.1 times less than the change in total petroleum hydrocarbon content. The inability of this study to correlate respiration data to actual changes in diesel concentration could be explained by volatilization, long‐term sorption of diesel hydrocarbons to organic matter and incorporation of diesel hydrocarbons into microbial biomass, aspects of which require further investigation.