Impact of soil amendment on phytotoxicity of a 5-month old waste engine oil polluted soil

Abstract

The present study investigated the effects of soil amendment on the remediation of waste engine oil (WEO) polluted soil, as well as the eventual phytotoxic effects of remediated amended soil on some growth parameters of cowpea. There was significant decrease in heavy metal concentration of the polluted soil more than average, nine months after amendment. There was also total remediation of some PAH compounds (benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benezo(g,h,i)perylene, benzo(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, fluoranthene, fluorene and Indeno(1,2,3-c,d)pyrene). Achromobacter sp, Clostridium sp,Sarcina sp and Micrococcus sp were prevalent bacteria species found in the polluted soils, while prevalent fungi species included Aspergillus niger, Penicillium sp,Geotrichum sp and Trichoderma sp. The actinomycete Nocardia sp was prevalent as well. Ecological risk factor initially posed by the presence of heavy metals in the unamended soil was significantly reduced to safe levels. Phyto assessment of the polluted soil was carried out just before soil was amended with saw dust and results showed that virtually all the cowpea seedlings died within 2 weeks; only those seedlings in unpolluted soils survived. Nine months after soil was amended, all cowpea plants survived up to fruiting. The present study also showed that cowpea was able to bioaccumulate heavy metals into harvestable parts, though bioaccumulation quotients calculated showed that these accumulations were not significant. Key words: Penicillium sp, Geotrichum sp, phytotoxic, fluoranthene, fluorine