Ref ID : 6759
Silvia M. Contreras-Ramos, Dioselina Alvarez-Bernal, Joaquin A. Montes-Molina, Oswald Van Cleemput, and Luc Dendooven; Emission of nitrous oxide from hydrocarbon contaminated soil amended with waste water sludge and earthworms. Applied Soil Ecology 41:69-76, 2009
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Soils in Mexico are often contaminated with hydrocarbons and addition of waste water sludge and earthworms accelerates their removal. However, little is known how contamination and subsequent bioremediation affects emissions of N2O and CO2. A laboratory study was done to investigate the effect of waste water sludge and earthworm Eisenia fetida on emission of N2O and CO2 in a sandy loam soil contaminated with the polycyclic aromatic hydrocarbons (PAHs): phenanthrene, anthracene and benzo(a)pyrene. Emissions of N2O and CO2, and concentrations of inorganic N (ammonium (NH4+), nitrite (NO2-) nitrate (NO3-)) were monitored after 0, 5, 24, 72 and 168 hr. Adding E. fetida to the PAHs contaminated soil increased CO2 production rate significantly 2.0 times independent of the addition of sludge. The N2O emission rate from unamended soil expressed on a daily base was 5 µgN kg-1 day-1 for the first 2 hr and increased to a maximum of 325 µgN kg-1 day-1 after 48 hr and then decreased to 10 µgN kg-1 day-1 after 168 hr. Addition of PAHs, E. fetida or PAHs + E. fetida had no significant effect on the N2O emission rate. Adding sludge to the soil sharply increased the N2O emission rate to >400 µgN kg-1 day-1 for the entire incubation with a maximum of 1134 µgN kg-1 day-1 after 48 hr. Addition of E. fetida, PAHs or PAHs + E. fetida to the sludge-amended soil reduced the N2O emission rate significantly compared to soil amended with sludge after 24 hr. It was found that contaminating soil with PAHs and adding earthworms had no effect on emissions of N2O. Emission of N2O, however, increased in sludge-amended soil, but addition of earthworms to this soil and contamination reduced it.