Aim: Plant-microbe interactions are considered to be important processes determining the efficiency of phytoremediation of petroleum pollution. The use of legume-Rhizobium is a suitable method for modification of petroleum-contaminated soil. The aim of this study was to evaluate the phytoremediation potential of Acacia – Rhizobium symbiosis in petroleum-polluted soil.Material and methods: The three-day acacia-seedlings were transferred to hydroponic medium and inoculated with rhizobium. Then, the 13-days seedlings transferred to polluted soil with different concentration of crude oil, that is, 0% as control and 1-5% (vol. /Wight), at the start and end of the 90-days period. Soil samples were analyzed for hydrocarbon removal (total hydrocarbon, n-tridecan, n-tetradecan and n-pantadecan) by GC-FID. Contents of Pb, Zn and Cd were measured with atomic absorption from soil and plant roots. The data were statistically analyzed with the help of SPSS11 and Duncan 'test.Results: The results showed accumulation of heavy metal in plant roots and it's reducing in soil. Hydrocarbon reduction was found over the course of the experiment in all treatments. The maximum removal was obtained in plants inoculated with rhizobium at 4% treatment, in which inoculated-acacia removed 97-100% of the hydrocarbons from soil. There fore inoculation Rubinia pseudoacacia with Rhizobia are effective in removing TPHs and heavy metals from petroleum polluted soil.Conclusion: Based upon these results, Rubinia pseudoacacia L. inoculated with rhizobium can be used as lead and cadmium bioaccumulator in petroleum pollution and was selected for the phytoremediation of petroleum-contaminated soil.

PAHs are toxic compounds with carcinogenic effects on humans that are released into the environment by incomplete combustion of fossil fuels. Three methods are commonly employed for PAHs pollutant removal: physical, chemical, and biological. From among these, the biological method which typically contains microbial processes and transforms pollutants to nontoxic or less toxic substances is the most innocuous and effective solution. In this study, attempts were initially made to enrich, isolate, and purify indigenous bacteria from PAHs polluted soil. In the second stage, the PCR method was exploited to identify the bacteria that had the capability of growth and reproduction in polluted conditions. It was found that the degrading bacteria are component species of gram negative bacilli determined asShewanella, Pseudomonas, and Achromobacter. The results of the present study indicate that the bacteria have the best performance in PAHs removal from polluted environments.

Background and Objectives: The poor accessibility of microorganisms to PAHs in soil has limited success in the process of bioremediation as an effective method for removing pollutants from soils.Different physicochemical factors are effective on the rate of biodegradation. The main objective of this study is to assess effects of nutrient and salinity on phenanthrene removal from polluted soils.Materials and Methods: The soil having no organic and microbial pollution was first artificially polluted with phenanthrene then nutrients and salinity solution in two concentrations were added to it in order to have the proportion of 10% w: v (soil: water). After that a microbial mixture enable to degrade phenanthrene was added to the slurry and was aerated. Finally, the residual concentration of Phenanthrene in the soil was extracted by ultrasonic and was analyzed using GC. We measured the microbial populationusing MPN test. This study was conducted based on the two level full factorial design of experiment.Results: MPN test showed that the trend of microbial growth has experienced a lag growth. The full factorial design indicated that nutrient had the maximum effect on bioremediation; the rate of phenanthrene removal in the maximum nutrients-minimum salinity solution was 75.14%.Conclusion: This study revealed that the more nutrient concentration increases, the more degradation will be happened by microorganisms in the soils. However, salinity in the concentration used had no effect on inhabitation or promoting on the Phenanthrene removal.

Oil pollution is a worldwide threat to the environment and the remediation of oil-contaminated soils, sediments and water is a major challenge for environmental research. Bioremediation is a useful method for soil remediation, if pollutant concentrations are moderate and non-biological techniques are not economical. The bioremediation consists strategy of actively aerating the soils and adding fertilizer in order to promote oil biodegradation by indigenous microorganisms. The objective of this study was to investigate whether agricultural fertilizers (N, P, K) enhance the microbial degradation of petroleum hydrocarbons in soil. Artificially polluted soil with %1density of crude oil was used and then fertilizers were applied in 3 levels of 0, 1 and 2 ton/ha in 3 replicates. The soils were kept in 30oC and 60 percent of field capacity condition for 5 to 10 weeks. To provide the necessary aeration, the soils were tilled twice a week by shovel. Soil sample were analyzed for hydrocarbon-degrading heterophic bacteria count and some soil chemical properties. Residual oil was measured by oil soxhlet extraction method, and gas chromatography. The results showed that the hydrocarbon-degrading and heterotrophic bacteria count in all the treatments increased with time and heterotrophic bacteria population increased from 6×103 cfu/g soil to 1.4×108 cfu/g soil. Also, soil C/N ratio decreased from 6 to 3. The results indicated that the applied fertilizer increased the degradation of the hydrocarbons compared with the control. Gas chromatography results showed that normal paraffin and isopernoid (Phitane and Pristane) decreased in the range of 45 to 60 percent in all treatments. Furthermore, the results showed that the application of fertilizers at 2 ton/ha rate in oil-contaminated soil lead to greater rates of biodegradation after 5 weeks indicating the feasibility of bioremediation.

Environmental pollution by heavy metals is a growing global concern. Most heavy metals accumulate in the top soil and in the long term, increased concentrations in the soil results in increased absorption and accumulation in plants. The usual concentration of cadmium in the soil is 0.001-2.4 mg/kg of dry soil. The level of absorption and accumulation in plants depends on the type of plant, tissue make-up of the plant and physical and chemical characteristics of the soil. There is a deficit of information on the amounts of absorption and accumulation of heavy metals at different tomato growth stages. This study was conducted to analyze the impact of the level of cadmium concentration in soil on its absorption and accumulation at different stages of tomato growth using factorial experimentation in a completely randomized design with three repetitions. The variables were three Cd concentrations (control treatment with no Cd; soil with 50 mg kg-1 Cd; soil with 50 mg kg-1 Cd; soil with 50 mg kg-1 Cd). The soil samples were collected from 400 ha of farmland at the Seed and Plant Improvement Institute in Karaj, Iran. They were sifted twice using 2 mm mesh and the treatments were prepared by adding cadmium nitrate to the soil to make homogeneous mixtures. The experiments were carried out in plastic cylinders 120 cm in length and 85 cm in diameter.The depth of the solution soil was sampled hourly and tomato organs were sampled at different growth stages to record the cadmium absorption rate. SPSS software was used to perform an analysis of variance of the data and the Duncan multiple range test was used to perform a comparison of means (P ≤ 0.05 and P≤ 0.01). Results showed that cumulative cadmium concentration differs in the tissues of the leaf, root, leg, fruit and peel in decreasing order. A negligible amount of the total cadmium added to the soil was absorbed by the plant. Total cadmium absorbed in the cellular colonies of the tomato plant in the control treatment, soil with 50 ppm added Cd, and soil with 100 ppm added Cd were 0.0384, 0.564 and 0.678 g, respectively.The results indicate a direct relationship between Cd accumulation and Cd concentration in the root region.A comparison of the outcomes indicated that increasing the cadmium concentration resulted in a reduction of tomato growth and, especially, the production rate. A 20-35% decrease in production rate was seen in 50-00 ppm cadmium exposure compared to the control. These results show that strong decreases in cadmium concentrations in the solution soil did not decrease the absorption rate of cadmium at various growth stages of the tomato.