Hexadecane mineralization and denitrification in two diesel fuel-contaminated soils

• Published in: FEMS microbiology ecology 2000, Vol.32 (1), p.17-23
• Main Authors: Roy, Réal, Greer, Charles W.
• Format: Article
• Language: English
• Subjects: Ammonium; ammonium salts; Bacteria; Bacterium; Denitrification; Hexadecane; Nitrate; Nitrous oxide; Soil; urea
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1016/S0168-6496(99)00103-8

The effect of nitrate, ammonium and urea on the mineralization of [ 14C]hexadecane (C 16H 34) and on denitrification was evaluated in two soils contaminated with diesel fuel. In soil A, addition of N fertilizers did not stimulate or inhibit background hexadecane mineralization (4.3 mg C 16H 34 kg −1 day −1). In soil B, only NaNO 3 stimulated hexadecane mineralization (0.91 mg C 16H 34 kg −1 day −1) compared to soil not supplemented with any nitrogen nutrient (0.17 mg C 16H 34 kg −1 day −1). Hexadecane mineralization was not stimulated in this soil by NH 4NO 3 (0.13 mg C 16H 34 kg −1 day −1), but the addition of NH 4Cl or urea suppressed hexadecane mineralization (0.015 mg C 16H 34 kg −1 day −1). Addition of 2 kPa C 2H 2 did not inhibit the mineralization process in either soil. Denitrification occurred in both soils studied when supplemented with NaNO 3 and NH 4NO 3, but was not detected with other N sources. Denitrification started after a longer lag in soil A (10 days) than in soil B (4 days). In soil A microcosms supplemented with NaNO 3 or NH 4NO 3, rates of denitrification were 20.6 and 13.6 mg NO 3 − kg −1 day −1, respectively, and in soil B, they were 18.5 and 12.5 mg NO 3 − kg −1 day −1, respectively. We conclude that denitrification may lead to a substantial loss of nitrate, making it unavailable to the mineralizing bacterial population. Nitrous oxide was an important end-product accounting for 30–100% of total denitrification. These results indicate the need for preliminary treatability studies before implementing full-scale treatment processes incorporating commercial fertilizers.