Abstract

MALDONADO-CHAVEZ, E; RIVERA-CRUZ, MC; IZQUIERDO-REYES, F  and  PALMA-LOPEZ, DJ. Effects of rizosphere, microorganisms and fertilization on bioremediation and phytoremediation of soils with new and weathered crude oil. Universidad y ciencia [online]. 2010, vol.26, n.2, pp.121-136. ISSN 0186-2979.

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 250x10⁶ CFU mL^-1 + 40x10⁵ 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 promoted new oil degradation and weathering. The greatest degradation after 158 days was of 47% in the soil with 50 000 mg kg^-1 of PN, and the lowest was that in soils with 78 000 and 79 457 mg kg^-1 of PN and PI respectively. The leguminous guaje inoculated with the consortium and fertiliser has a great potential for use in phytoremediation of soils with 50 000 mg kg^-1 of HTP and PN. The degradation of HTP was promoted up to 81%, 9% more than in the Egypt grass rhizosphere. In soils with PI, the Egypt grass was the best with a degradation of 44%.

Keywords : Aspergillus; Brachiaria; Leucaena; Pseudomonas; Serratia; Trichoderma; microbial consortium; degradation; fertiliser; total oil hydrocarbons.