PLANT-MICROBIAL INTERACTIONS IN THE ASSISTED BIOREMEDIATION OF A PETROLEUM HYDROCARBON-POLLUTED SOIL AFTER BIOAUGMENTATION WITH PLEUROTUS TUBERREGIUM

Abstract

The plant-microbial interactions in the assisted bioremediation of a petroleum hydrocarbon-polluted soil after bioaugmentation with Pleurotus tuberregium were investigated. Top soils were collected from a fallow plot on the campus of the University of Benin, Nigeria. A list of all weeds growing on the plot was taken, with a bid to determine the soil seeds bank (Table 2). The soils were then polluted with different concentrations of waste engine oil (1.0, 2.5, 5.0 and 10.0% w/w oil in soil) on weight basis. The polluted soils were then left for five months (SPi). The unpolluted soil (0 %) was designated as control experiment. Result shows that concentration of Mn prior to augmentation of the control experiment (5MAP) was 28.5mg/kg as against 29.6mg/kg and 30.8 mg/kg in the weeded and unweeded bioaugmented treatments respectively. There were significant reductions in soil content of Zn at 10 MAA. Zn concentration in the weeded buckets ranged from 12.2 – 36.9 mg/kg compared to 10.6 – 30.8 mg/kg in the buckets with weeds. Concentration of Ni was 2.52 4.12mg/kg at 5 MAP compared to 0.72 – 1.15 mg/kg in the weeded buckets and 0.07 – 0.13mg/kg in the unweeded buckets 10 months after bioaugmentation. Hydrocarbon degrading bacteria count for SP0 were 1.81 x105 cfu/g in the presence of weed in soil (WW) and 1.65 x105 cfu/g in the absence of weeds in soil (NW) whereas SPA0 were 2.65 x105 cfu/g in the presence of weeds in soil (WW) and 2.04 x105 in the absence of weeds in soil (NW). The total fungi count for SP5 were 1.64 x105 weed presence in soil (WW) and 0.80 x105 cfu/g in no weed presence in soil (NW) for five months after pollution (5MAP) even as SPA5 were 2.08 x105 cfu/g for weed presence in soil (WW) and 1.22 x105 cfu/g for no weed presence in soil (NW) for ten month after bioaugmentation (10MAB) respectively. The most dominant bacteria were Clostridium sp. while the less dominant were Bacillus subtilis. For that of the fungi Aspergillus niger were dominant whereas Aspergillus flavus were the least.