Nitrification and N mineralization in chemical demulsifier (Separol NF.36 and Servo C.6602) contaminated soil

A sandy loam soil from a mangrove freshwater environment was contaminated with 0, 25, 50, 100 and 1000 ppm concentrations of chemical demulsifiers to determine their effect on nitrogen transformation. Changes in nitrification and N mineralization rates were determined by monitoring the changes in the levels of NH₄⁺-N, NO₂⁻-N and NO₃⁻-Nin the treated soilsfor a period of 28 days. Application of Separol NF.36 and Servo C.6602 inhibited ammonfication as shown by the increase in NH₄⁺-Nlevels in the treated soil above the untreated control, though not significantly. A demulsifier concentration of 1000 ppm inhibited ammonfication most, as shown by the high level of NH₄⁺-N, while a 25 ppm concentration showed the least adverse effect on NH₄⁺-N reduction in the contaminated soils. Separol NF.36 and Servo C.6602 at the concentrations used did not result in the complete inhibition of nitrification rates. Nitrate-N levels were very minute; the effect of different concentrations of demulsifiers on NO₂⁻-N levels did not vary significantly, the NO₂⁻-N being rapidly converted to NO₃⁻-N accounting for the increases in the NO₃⁻-N levels throughout the period of investigation.

However, all concentrations of the chemical demulsifier used depressed NO₃-N levels until the 14th day in Separol NF.36 and the 7th day in the Servo C.6602 treated soils. Treatments with 1000 and 100 ppm of demulsifier depressed nitrification and N mineralization most, while 25 and 50 ppm concentrations stimulated nitrogen transformation most, especially after the 14th day in the Separol NF.36 treated soil and after the 7th day in the Servo C.6602 treated soils. The effect of Separol NF.36 and Servo C.6602 when compared, did not vary significantly. Changes in total mineral nitrogen level in the treated soils exhibited the same trend as NO₃⁻-N.