Effects of Soil Amendments on the Intrinsic Qualities and Development of Soil Seed Bank of a Monitored Naturally Attenuated Petroleum Hydrocarbon-Polluted Soil

Abstract

A record of the soil seed bank in oil polluted areas is necessary to assess their capacity for tolerance and phytoremediation potentials of such polluted sites. The present study investigated the effect of soil amendments on the development of soil seed bank of a waste engine oil polluted soil. Top soil (0- 10cm) was collected from an area of known soil seed bank and physiochemical parameters. The soil was then contaminated at 5 % w/w oil-in-soil and immediately amended with poultry manure, sawdust and dried leaves of Vernonia amygdalina and a combination of any of the amendments. Results showed that at 3 months after pollution (MAP), there was general reduction in heavy metal composition and polyaromatic hydrocarbon (PAH) contents of the soil. This content significantly reduced to 46.85 mg/kg 3 months after pollution using treatment SD. The heavy metal content of Fe was 3250.1 mg/kg. This reduced to 934.5 mg/kg using treatment SD with similar reductions in Mn, Zn, Cu, Cr, Cd, Pb, Ni and V contents. Euphorbia spp were the most prevalent weeds. Soil amendment of waste engine oil polluted soil showed the influence on the enhancement of the soil seed bank. Weed diversity was also affected with significant improvement recorded in the polluted soil which probably resulted from enhanced biodegradation activities. Indigenous plant species (particularly Euphorbia spp. and Cyperus sp.) should be used together with soil amendments in phytoremediation following results from present study.

Keywords: attenuation, bioremediation, heavy metals, petroleum hydrocarbons, soil amendment, soil seed bank.