Contaminants can be categorized into organic and inorganic groups. Organic contaminants are carbon based, and their presence in waste forms may be as a single contaminant associated with inorganic contaminants, or a suite of complex mixtures which may be toxic at very low concentrations. Organics of greatest environmental concern are usually refined petroleum products, chlorinated and non-chlorinated solvents, manufactured biocides, organic sledges and substances from manufacturing processes. Most contamination due to organics are associated with accidental spills and leaks, originating from equipment cleaning, maintenance, storage tanks, residue from used containers and outdated material (Yong and Mulligan, 2004). Transport and fate of organic contaminants are important. Organic contamination migrations are due to advection (by fluid flow through soil) and diffusion, but other forms of transport e.g. infiltration may also contribute to migration (Environment Agency, 2002). The response of the soil to a contaminant depends upon the type of soil and the nature of the contaminant. The sensitivity of soil to contaminants depends upon the type of soil (such as particle size, mineral structure, bonding characteristics between particles and ion exchange capacity) and the nature of contaminants. Fang (1997) defined a sensitivity index (ranging from 0 to 1) to different types of soil. Sensitivity of sand and gravel (0.01 to 0.1) is much lower than clay particles (0.6-0.9). There are a number of techniques for remediation of contaminated land. These include physical (washing, flushing, thermal, vacuum extraction, solvent extraction), chemical (stabilization and solidification) and bioremediation techniques. However, the applicability and feasibility of different methods for remediation are dependent on many factors such as soil characteristics (soil type, degree of compaction and saturation), site geology, depth of contamination, extent of contaminant in lateral direction, topography, surface and ground water and the type and amount of contaminants. Thermal treatment and using surfactants are the most popular methods for remediating the soil contaminated with petroleum compounds. In this research remediation of a soil contaminated with different percentages of gasoline was studied through physical techniques in laboratory. The applied physical techniques were thermal technique and use of two different kinds of surfactants. The obtained results were compared with each other and discussion was performed.
Material and Soil, gasoline and surfactant are the basic materials that were used in this work. The soil that was used in this testing program was a clayey soil. Two different types of ionic and nonionic surfactant, namely Tween 80 and SDS, were used in this work for remediating soil, contaminated with gasoline. Contaminated soil was prepared by adding 5 and 10 % weight (to air dried soil) of gasoline. 6 kg air dried soil was selected and the desired amount of gasoline was weighted, then it was sprayed on the soil and thoroughly mixed by hand for about 2 hours. The prepared mixture was kept inside a covered container for a week in order to come to equilibrium with the soil. For thermal remediation the contaminated soil with a specific percent of gasoline was kept inside a constant convection oven at 50, 100, and 150oC for about one week to desorb the contaminating compound. Tween 80 and SDS were used for remediation of the contaminated soil. The amount of used Tween 80 was 25% weight of contaminating compound and selection of SDS amount was based on 50% weight of contaminating matter. The samples for the main tests were prepared by static compaction according to the optimum water content and maximum dry unit weight that were obtained from standard compaction tests. Atterberg limits, grain size distribution, compaction and unconfined compression tests were performed on samples of natural, contaminated and remediated soil according to the ASTM standard.
The results of Atterberg limits (LL, PL and PI) for the contaminated soil (with 5 and 10 % gasoline) indicated that the values of them are increased with increasing the percent of gasoline. These values are nearly the same as natural soil after remediation with thermal method and surfactants. The grain size distribution curves were determined for the natural soil, contaminated soil with 5% and10% gasoline and soil remediated by thermal and surfactant techniques. The results showed that by using thermal technique the percent of clay is decreased and the percent of sand and particularly silt is increased by increasing temperature. The results of grain size distribution for the soils remediated by SDS and Tween 80 showed that the percent of clay is reduced but the percent of silt and sand are increased. Comparing the results of the two surfactants shows that the effect of Tween 80 in reduction of the percent of clay is more than SDS. The results showed that after thermal treatment, the maximum dry unit weight decreases and the optimum water content increases. For the contaminated soil with gasoline a reduction in maximum dry unit weight is observed compared with natural soil. The effect of SDS and Tween 80 on soil remediation is reduction in maximum dry unit weight and optimum water content. The results of compression strength showed that adding gasoline to soil causes a reduction in final strength and this reduction is a function of gasoline percent. The results also indicated that the strength of remediated soil by thermal or surfactant techniques, is reached nearly to the strength of natural soil. Scanning electron microscopy (SEM) tests were performed on the samples in order to observe the microstructure of the samples in different conditions (natural and contaminated with different percent of gasoline). The results of SEM showed that the structure of soil is changed by contamination to gasoline. It can be said that the gasoline causes reduction in the thickness of DDL because of low dielectric constant and hence a flocculated structure is formed. In the flocculated structure due to attractive forces, the fine particles paste to each other and form coarse particles. Therefore, variations in the Atterberg limits and compaction parameters can be resulted from forming new structure by adding gasoline. These results of compression strength are not in agreement with the theory of diffuse double layer (DDL). The reduction in dielectric constant would cause a flocculated structure in soil and the strength of the contaminated soil should be increased in comparison with the natural soil. It can be said the viscosity of gasoline cause reduction in the strength of contaminated soil.
In this experimental work a cohesive soil was contaminated with 5% and 10% of gasoline. The experimental tests showed that the properties of contaminated soil are different from natural soil and the change in the properties is a function of gasoline percent. The contaminated soil, was remediated by thermal treatment and also using two surfactants. The results also showed that using surfactants is more effective than using thermal method in soil remediation, and can treat the soil nearly to its original condition.
-Base on the SEM analysis results, adding gasoline to the soil, will change the soil micro structure to a flocculated one.
-The gradation curves show that adding gasoline to the soil will change the gradation from finer to coarser.
- Contamination to gasoline will change the compaction parameters of the soil, and will reduce the soil final strength significantly.
- The results show that using thermal method and surfactants is effective in remediating the soil, but it is more effective to use surfactants.

Utilizing considerablepetroleum products، increasing soil contamination and need to its clean-up is one of serious environmental issues. Soil vapor extraction is a common and very wide used method for soil remediation because of its Easy operation، low cost and high efficiency. In this paper، influence of soil type and heating، as two important parameters in efficiency of soil vapor extraction method is examined. The used soil is blown sand، which is mixed with different percentages ofkaolinite clay. Establishing pilot and running experiments، the result of soilsremediationout of aliphatic hydrocarbons in gas-oil is reported. The results indicate thatenhancement of clay percentage leads to great reductioninclean-up efficiency. After 24 hours test running،removal efficiencyreached to 78. 4%for the soil with 20% clay content، while this efficiency fell down to 23. 75% for the soil with 40%of clay content. Having no clay within the soil، soil-heated vapor extractionmethod did not causenoticeable increasing in clean-up efficiency. However، heating has the most influence and increases clean-up efficiency for 20. 6%with presence of 20% clay within the soil، while presence of %40 clay decreasesthe efficiency to 12. 57%.

Nowadays soil contamination by oil production due to leakage of fuel storage and transition hazards is an important environmental problem. Due to the additional hazard of transition to the human food chain, there is the possibility for pollution of ground water. Therefore in situ remediation of oil contaminated soil is very important. In this investigation the effective parameters on diesel soil remediation by soil washing using SDS surfactant were investigated. For modeling of contaminated land remediation the contaminated soil columns was used. Soil columns were contaminated with diesel in amount of 10000 ppm and 20000 ppm. In this study the effect of pH, surfactant concentration in washing solution and initial contamination amount were investigated. Results showed that in all states the quantity of remediation for acidic states is very low and efficiency of remediation when using only water is (1:3) of maximum amount. For soil with initial contamination amount of 10000 ppm the maximum efficiency is for surfactant in concentration of 0.3 and pH=11 and for soil with initial contamination amount of 20000 ppm the maximum efficiency is for surfactant in concentration of 0.1 and pH=11. By increasing the amount of surfactant concentration the permeability of soil decrease and in pH=11 the amount of permeability is maximum. With increasing initial contamination quantity, the velocity of increasing of remediation and permeability decreased. Consequently in the low level of contamination the effect of washing solution pH in soil remediation is greater in comparison with high levels of contamination.

One of the method to clean up contaminated soil is growing a hyper accumulator plant which is named phytoremediation. Some of hyper accumulator plants are proper host for mycorrhizal fungi.In this relationship, fungus, consume a part of organic carbon from the plant and by developing its mycelium network help plant to uptake more mineral nutrients from the soil. By doing a greenhouse research tried to determine the mycorrhizal efficiency to increase plant ability in mineral nutrient and heavy metal uptake from a contaminated soil with a high level of Cr, Ni and Cd .In this exam two hyper accumulator plants , sunflower and corn and also 4 species of mycorrhizal fungi, including, Glomus mosseae , Glomus intraradices ,Glomus etunicatum and Glomus sp and one treatment without fungi as blank, with 5 replications per treatment were used. Results showed that mycorrhizal inoculation in two plants , sunflower and corn by increasing mycorrhizal colonization enhanced aerial part growth of plant and also macro and micro nutrient uptake. T4 treatment, including G.mosseae and G.intraradices in corn growth had the highest capacity for Cd, Ni and Cr uptake from the soil, so that it increased the uptake of these three elements in corn stalks react, 1.57, 3.79 and 4.18 micrograms per pot. In sunflower this treatment was able to increase Cd and Ni uptake, react 0.21 and 0.23 micrograms per pot. Finally if we want to use these two plants for phytoremediation, the use of these two fungi will be proposed.

One of the most critical discussions about environmental pollution is soil pollution. Contaminated soil can endanger the life of organisms. For this reason, removing all types of soil contamination and even reducing the types of soil contamination is a fundamental and critical issue. One of the ways to clean and improve contaminated soils is the electrokinetic method; The principle of this method is to transfer the contaminated ions in the soil by an electric field and to eliminate and neutralize the contaminated ion or remove them from the soil. This practical method can remove various contaminants such as petroleum products and heavy metals. In some cases, this method can be seen along with other methods of soil improvement or even combining this method with some other methods to see a much better result. The present study will present the research on soil contamination by the electrokinetic method and its limitations.

Aim & back ground: Nowadays, one of the major issues in the world is cleaning up soils contaminated with inorganic pollutants. Phytoremediation is one of the methods that due to economic reasons and environmental friendly action which attracted much attention in recent decades. The aim of this study: To assess the potential Zn accumulation in different parts of ornamental palm. In this study one year old ornamental palm seedlings in a randomized design with three repetition, were exposed to ZnSO4 in 4 different concentrations: 0, 50, 250 and 500 (mg Zn2+ L-1) for 45 days. Subsequently Zn2+ uptake was quantified in roots, shoots and leaves of the seedlings by Atomic Absorption Spectroscopy (AAS). In addition, some morphological and physiological parameters such as biomass production, shoots and roots length, plant appearance and some other elements were measured. The results of analysis of variance (ANOVA) showed that the traits such as fresh and dry weight tolerance value, collar diameter, plant height, tolerance stress, index of plant resistance, relative water content and deficiency saturated absorption cell, had been significantly effected by Zinc treatments. The results also showed that ornamental Palm seedlings have the ability to accumulate zinc manifold in roots than shoots and leaves. In addition, the species has the coefficients of bioaccumulate more and transport factors less than one unit. Based on these results, we can recommend the ornamental Palm as stabilizer species for the cleanup of contaminated soils with zinc heavy metal.

The explosives, in manufacturing, transporting and using at military installations, caused to pollution of ground and subground waters, soils and sediments. Soil is posed as a relationship between water, weather and plants and animals existence of a zone. Therefore, soil health is a necessary matter. So, in order to suppression from environmental issues and human detriment, polluted soil improvement form these materials are required. This improvement can be done by physical, chemical and biological routes. In early decades, bio-improvement is more considered, due to environment friendly, health and safety. Bio-improvement processes if explosives are implemented by two routes: biological stimulus and biological amplification. In this paper, methods of green improvement for polluted soil refinement such as composting, utilizing of transgenic plant, microbes and etc. from common energetic materials such as TNT, RDX, HMX AND Cl-20 are investigated.

Soil pollution by petroleum compounds is one of the most common environmental problems, which causes soil contamination during extracting, transferring and refining. Bioremediation is an economic technology that makes use of plants to reduce oil pollution in soil. The aim of this study was to evaluate growing ability of Lathyrus sativus, Lens culinaris, Trigonella foenum and Glycyrrhiza glabr of the Fabaceae family in the soil contaminated with light crude oil. Also potential oil removal from soil by these species through bioremediation was shown. In this study, after examining the developmental stage of 4 samples of Fabaceae plant family, potential of removing hydrocarbons from the soil contaminated by light crude oil with different concentrations (1, 2, 3, and 4%) at 40 days in Completely Randomized Design (CRD) was investigated. The result shows that the maximum possibility of pollution reduction is in lathyrus sativus with 73.3% in sample (1%) and the minimum possibility of pollution reduction is in Trigonella foenum with 38.6 in sample (4%). Moreover, Person's correlation coefficient showed that by increasing dry weight of the plant, the amount of pollution reduction in the soil increases. Given the acceptable performance of oil pollution cleanup by these species and economic saving as compared to other methods, the use of this method is recommended for the contaminated areas in Iran.

Phytoremediation as a cost-effective and environmental friendly technique used to polluted soils with heavy metals contamination. The present study was aimed to evaluate the resistance and remediation of Tamarix aphylla calli affected by in vitro mutagenesis with. In the first step, optimization of callus induction and mutation in media with different concentrations of -2,4 was performed. The third experiments involved the evaluating of resistance and remeditaion rate of callus to cadmium at the concentrations of 0-40 mg L-1 in both treated and untreated explants with Ethyl methanesulfonate in medium. The highest survival and induction of callus was induced by the concentration of 1 mg L-1 2,4-D during the short time. Ethyl methanesulfonate at concentration of 0.2 percentage and 30 minutes made the maximum survival and minimum blacking phenomenon of explants. The highest accumulation of cadmium was obtained 1053.56 mg kg-1 dry weight in callus treated by 40 mg L-1 cadmium.