Nutrient status, hydrogen peroxide content and peroxidase activity of arbuscular mycorrhizal plants of Melilotus albus grown in diesel-contaminated substrate

Background: Petroleum hydrocarbons affect plant growth, but little is known about physiological responses of mycorrhizal plants facing diesel contamination. Objective: To evaluate the effects of arbuscular mycorrhizal fungi (AMF) on the nutritional status, peroxidase activity (POX), and hydrogen peroxide content (H2O2) in leaves of Melilotus albus planted under diesel-contaminated sand (7500 mg kg-1). Methods: A 2x2 factorial experiment was set in a completely randomized design, under greenhouse conditions for 35 days. Seedlings were pre-inoculated with AMF and transplanted to sand with or without diesel, including non-AMF plants. Results and conclusions: Diesel contamination impaired plant growth; AMF plants had similar growth than non-AMF plants at diesel-contamination, but low nutrient content. Protein content decreased due to diesel in non-AMF plants, but this content was low in AMF plants regardless diesel contamination. Diesel increased POX; whereas AMF plants with or without diesel had higher POX than non-AMF plants. The H2O2 content in AMF plants with or without diesel was low than non-AMF plants. Diesel contamination diminished AMF-colonization, but AMF dissipate more diesel hydrocarbons (>40%). Overall, AMF alleviated the toxic effects of diesel on plants.

Geotechnical Evaluation of Diesel Contaminated Clayey Soil

Soil contamination by different hydrocarbons has rapidly expanded worldwide, surpassing the self-purification capacity of soils and increasing the number of contaminated sites. Although much effort has been devoted to study the effects of diesel contamination on the geotechnical properties of soil, there is still limited available information about it. Moreover, there is no available information about the maximum diesel retention that soil can have and its effect on the geotechnical behavior of the soil. Thus, in this paper, we determined the maximum diesel retention by an unsaturated clayey soil and evaluated the impact of diesel contamination on its geotechnical properties. The results showed that the soil could only retain 12.6% of the added diesel and the excess was expulsed. At such a diesel concentration, the saturation rate of the soil was lower than 80%. Diesel contamination increased the plasticity and the internal friction angle of the soil, while its cohesion was considerably decreased. It should be noted that the matric suction of contaminated soil was lower than the one obtained for natural soil. However, its osmotic suction was considerably higher. This indicates that osmotic suction must be considered to evaluate the shear strength of contaminated soils.

Comparative Bioremediation of Diesel Oil Bearing Soil by Pseudomonas aeruginosa and Pseudomonas fluorescence

The quality of life on earth is directly linked to the overall quality of the environment. The natural ecosystem encompasses all living and non-living things existing on earth naturally. It is an environment that interacts with all living species, but which may be contaminated with diesel a derivative of hydrocarbons. Diesel spills contaminate both aquatic and terrestrial environments. To prevent the environmental and health risks of this, remediation needs to be advanced. Bioremediation, degradation by microbes, is one of the suitable methods for cleaning diesel contamination. In the present work, the biodegradation of diesel oil contaminated soil has been investigated comparatively with Pseudomonas aeruginosa and Pseudomonas fluorescence coupled with fertilizer as essential nutrients. Based on observations carried out in 18 days, Pseudomonas aeruginosa alone as well as in the presence of essential inorganic nutrients was found to exhibit higher remediation potential in degrading soil contaminated with diesel oil than Pseudomonas fluorescence.