Nitrification in polluted soil fertilized with fast- and slow-releasing nitrogen: a case study at a refinery landfarming site |
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| Authors: | Peltola Rainer Salkinoja-Salonen Mirja Pulkkinen Janne Koivunen Marja Turpeinen Anna-Riina Aarnio Tuula Romantschuk Martin |
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| Affiliation: | Department of Applied Chemistry and Microbiology, P.O. Box 56, University of Helsinki, FIN-00014 Helsinki, Finland. rainer.peltrola@ppl.inet.fi |
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| Abstract: | The nitrifying activity and the effect of fertilization with urea and methylene urea were studied in a landfarming site. The site has been operative over 20 years and maintained by heavy nitrogen fertilization. The landfarming soil contained 4-6% (w/w) oil. The nitrate accumulation was 20-50mg NO3-N day(-1)kg(-1) observed after methylene urea fertilization of 889 g Nm(-2). Nitrification ex situ (in laboratory conditions) was 8.8 mg NO3-N day(-1) kg(-1) in the presence of 380 mg kg(-1) NH4+-N. The half-saturation concentration of nitrification was more than 200 mg NH4+-N kg(-1). The results show that nitrification was active in soil with high oil concentration. Urea fertilization of 893 g Nm(-2) caused an increase of soil NH4+-N concentration up to 5500 mg kg(-1) and pH>8.5. This led to inhibition of nitrification, which persisted after NH4+ concentration decreased below 200mg NH4+ kg(-1). |
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