Effects of rizosphere, microorganisms and fertilization on bioremediation and phytoremediation of soils with new and weathered crude oil

The bioremediation potential for a consortium including two bacteria (Pseudomonas sp and Serratia marcescens), two fungi (Aspergillus sp and Trichoderma sp) and inorganic fertiliser incorporated into the soil, and the phytoremediation potential of the Para grass (Brachiaria mutica) and the leguminous “guaje” (Leucaena leucocephala), were evaluated both in a soil polluted with fresh crude oil (PN) recently incorporated into the soil, and in a soil with 25-year old weathered crude oil (PI) from chronic oil spills. The bioassay was 4x3x2x2 factorial: with the oil [150 mg kg−1 total oil hydrocarbons (HTP) from biogenic sources, 50 000 and 78 000 mg kg−1 HTP of PN and 79 457 mg kg−1 HTP of PI], the plant (without plant, with Para grass or with guaje), the microbial consortium (without and with inoculum, 5 mL of bacterial inoculum with 250x10 CFU mL−1 + 40x10 fungal CFU mL−1) and the fertiliser (without and with fertiliser, 160-50-00 dose). Forty eight treatments were evaluated. Quantified at the start (day 1) and end (day 158) were the degradation of the HTP, and the bacteria and fungi populations. The measurement of bacteria and fungi followed the counting method in Petri dishes. HTP extraction was carried out with dichloromethane according to the EPA 418.1 method, and quantification by gravimetry followed the NMX-AA-134-SCFI-2006. The interaction among the rhizosphere, the fertiliser and the microbial consortium generated significant positive effects (Tukey p ≤ 0.05) and