Role of Soil pH, Lipases and Catalase Activities in the Degradation of Spent Engine Oil and Crude Oil Pollution on Agricultural Soil

The activities of soil pH, lipases and catalase is prominent to oil degradation in the soil and their concentration gives useful information on soil’s the microbial activities. Six lots research site were polluted with spent engine oil and bonny light crude oil as follows A1 = 60cm3 farmland + 2dm3 of spent engine oil; A2 = 60cm3 farmland + 4dm3 of spent engine oil; A3 = 60cm3 farmland + 6dm3 of spent engine oil; B1 = 60cm3 farmland + 2dm3 of spent engine oil; B2 = 60cm3 farmland + 4dm3 of spent engine oil; B3 = 60cm3 farmland + 6dm3 of spent engine oil. Soil samples were collected at specified periods and analyzed for soil pH, catalase and lipase activity. Highest soil pH for topsoil (4.950 ± 0.025) was observed in weeks 2 A2, while at 15cm depth, the highest soil pH (4.390 ± 0.033) was observed in weeks 6 A3. At 30 cm depth, the highest soil pH was 5.385 ± 0.062 for weeks 6 B3. Lipase activity for topsoil was highest in weeks 8 A3 with a value of 3.460 ± 0.038 Unitsml-1. At 15cm depth, highest lipases activity was also observed in weeks 8 A3 with a value of 5.751 ± 0.037 Unitsml-1, while that of 30cm depth was observed in week 7 A2, with a value of 5.050 ± 0.047 Unitsml-1. Highest catalase activity for topsoil was observed in weeks 6 A3 with a value of 0.594 ± 0.047 X102µgml-1, while 15cm depth was 0.534 ± 0.012 X10-2 µgml-1 for week 2 B2 and 30cm depth was 0.472 ± 0.060 X10-2 µgml-1 for weeks 1 A1. The sensitivity of these soil enzymes to petroleum hydrocarbon pollution as observed in this study makes them early sensitive bioindicators of soil quality and soil health.