Remediation of soils contaminated with petroleum hydrocarbons
Vladimir Nadykta, Cristina Negri *
All-Russian Research Institute of Biological Plant Protection of RAAS, Krasnodar, Russia
* Argonne National Laboratory, USA
The work was completed with the CRDF financial support.
(Project RBO-10118-ÌÎ-03 (ANL)
“Heavy” oil from the Anastasievsk-Troitsk oilfield in the Krasnodar Region (Horizon IV) was released into the 2m2 (2m x 1m) plots at the concentrations 25 and 50 g/kg of chernozem soil. In a number of treatments, the fungi Penicillium canescens, Aspergillus ustus, and commercial trichodermine were applied during planting to determine potential positive effects of those microbes on the development of crops under oil contamination conditions. Before planting, the seeds of the studied crops (corn, sunflower, soybean) had been kept in the suspension of a corresponding fungus for two hours. Through the spore pressure evaluation the following values were obtained: for P.canescens - 6.4 õ 107 spores per running meter and a great number of mycelium fragments; for A.ustus – 8.0 õ 106 spores/m; for trichodermine – 2.2 õ 106 spores/m. In addition to the above-mentioned treatments, the effects of mineral fertilizers and irrigation were studied during the experiment.
It was stated that the growth and development of the tested crops had a direct relationship with petroleum product levels in oil-contaminated soil. So, in the treatments with the rate of application of oil 50g/kg, the soybean plants perished at the seedling stage. Sunflower and corn were more resistant to the oil contamination: all the plants survived at that oil concentration. However, after reaching the first leaves stage, all those plants stopped their development abruptly. At the concentration of 25 g/kg, the following situation was observed: The aboveground mass reduction for soybean was no less than 80-90% of control without oil application. The corn and sunflower plants retarded growth distinctly, but then, after forming 4-5 leaves had a rather intensive growth, so that by the end of the growing season they produced high biomass, which was close to that one of the plants grown without oil.
On the whole, based on the analysis of the obtained data the following conclusion may be drawn: In sunflower, none of the tested microbes contributed to overcoming the negative impacts of oil. In corn, some trend toward it was observed. The best results were obtained for soybean: from all the tested microbes only trichodermine did not increase the biomass of this crop. In other treatments, the effectiveness increase was appreciable. Thus, as a result of the conducted research the plants were identified which had good growth even at rather high heavy oil levels, as well as the microbes, which stimulated the growth of plants in oil-contaminated soil to a certain degree. The pure cultures of those microbes were obtained, their collection is conserved and may be used for further research.
Corn and sunflower, which are petroleum-resistant and quickly accumulate biomass, may be considered as potential phytoremediators. To achieve this purpose, however, these plants must have a clearly marked ability to remove the petroleum products. The results of their determining in the soil under the named crops using the gas-liquid chromatography allow to conclude that in some treatments a noticeable increase of the removed oil amounts was observed compared to the treatment without plants. In other words, the plant component contributes to phytoremediation. The research in this area is continued to gather the factual data necessary to develop an effective restoration system for the soils contaminated with petroleum hydrocarbons
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