جستجوی مقالات مرتبط با کلیدواژه « زیست پالایی » در نشریات گروه « آب و خاک »

Enzyme activity measurement is one of the significant methods in the bioremediation of soils contaminated with petroleum compounds. Biostimulation, bioaugmentation and their integration are among the types of bioremediation methods used in this experiment. For this purpose, to reduce light naphtha pollution (1%) in a sandy loam soil, a variety of bioremediation treatments, including providing NP elements, adding cow manure and Tween 80 surfactant, bioaugmentation, and integrated treatment were used. This experiment was carried out in a pot (containing 3 kg soil) based on split plot factorial design (pollution factor, bioremediation factor and time) with 3 replications, at room temperature, for 120 days. On days 0, 5, 10, 15, 30, 45, 60, 90 and 120, subsamples were taken from each pot to measure the activity of dehydrogenase and lipase enzymes. The results of the experiment showed that bioremediation treatments led to the reduction of oil pollutants. Likewise, dehydrogenase activity had a completely downward trend from the beginning of the experiment, and the changes of lipase activity in contaminated soil increased until day 10, decreased slightly from day 10 to 15, then, progressed with slight fluctuations until day 60 and decreased again from day 60 onward. Dehydrogenase activity changes in cow manure treatment during the experiment was from 3.39 to 0.35 (μg TPF g-1 h-1), and lipase activity in integrated treatment dropped from 57 to 33.56 (mU g-1). In addition to increasing the active microbial population involved in the decomposition of petroleum compounds and providing optimal conditions for their activity, the use of integrated treatments and cow manure is a suitable method to reduce the concentration of light naphtha.

Oil contamination can be treated by physical, chemical and biological approaches. The first two methods have limitations such as high costs, inefficacy and altering natural ecosystem. Today, biological treatment is a more interesting process to remove petroleum contamination. Bioremediation is a technique in which biological systems such as microorganisms are applied to degrade or transform harmful chemicals. In recent years, employing hydrocarbon degrading bacteria to cleaning a petroleum contaminated soil has become a prevalent, efficient and cost effective technique that converts toxic wastes to non-toxic end products. Soil contamination with oil compounds such as heavy naphtha can threaten soil, environmental and human health. In bioremediation process, soil microorganisms use these hydrocarbons as a carbon source and, while making a microbial biomass, play a role in its decomposition and conversion to carbon dioxide. Furthermore, this type of contamination can affect soil microbial population and its enzyme activity. Soil microbiome, in turn, has effect on this contamination using relevant enzymes. Application and comparison of various bioremediation methods such as biostimulation, bioaugmentation and integrated treatment were the main aims of this study to bio-remove heavy naphtha from contaminated soil. Moreover, mmonitoring of soil enzyme activity changes (including dehydrogenase and lipase) in this condition under different bioremediation treatments was another goal of this research. For this purpose, in a heavy naphtha-contaminated sandy loam, a variety of bioremediation treatments, including biostimulation (including supply of nitrogen and phosphorus elements, addition of manure and Tween 80), bioaugmentation treatment (using a consortium of efficient bacteria) and integrated treatment (including all biostimulation and bioaugmentation treatments together) were tested.

In this study, a sandy loam soil was used. Heavy naphtha was applied at a rate of 7% V/W to soil samples and various bioremediation treatments were performed as mentioned above. This experiment was carried out in a pot scale (containing 3 kg soil) based on split plot factorial design (pollution factor, bioremediation factor and time) with 3 replications, at room temperature for 120 days. During the experiment, the pots were aerated once a week and the soil moisture content was adjusted to 70-80% (W/W) of the soil water holding capacity twice a week. For bioaugmentation of bacterial isolates, a bacterial suspension (108 cfu mL-1) having a consortium of Arthrobacter sp. COD2-3, Stenotrophomonas nitritireducens COD5-6، Stenotrophomonas asidamainiphila COD1-1 with a ratio of 5% V/W were used. In biostimulation treatment, cow manure with 5% W/W was used. In NP treatment, N and P elements from ammonium nitrate and potassium phosphate (K2HPO4), were used with a ratio of 20:5:1 (C: N: P), considering soil organic carbon. Tween 80 as surfactant in the relevant treatments, was used at a rate of 0.3% V/W. In the integrated treatment, all the mentioned treatments were used together. On days 0, 5, 10, 15, 30, 45, 60, 90 and 120, subsamples were taken from each pot to measure the activity of dehydrogenase and lipase enzymes.

The results showed that during the experiment, bioremediation treatments reduced heavy naphtha contamination and the highest value for removal rate of this compound was 81% in the integrated treatment. Contamination also affected the enzymatic activity of soil so that the activity of dehydrogenase and lipase in all bioremediation treatments showed a decreasing trend. Dehydrogenase enzyme activity in cow manure treatment decreased from 1.67 to 0.59 (μg TPF g-1 h-1) and activity of soil lipase enzyme decreased from 33.82 to 26.24 (mU g-1) in the integrated treatment during the experiment. Among the bioremediation treatments, cow manure and integrated treatment had a greater effect on the elimination of heavy naphtha contamination than other treatments (p <0.01). It seems that the use of the above treatments were able to remove more heavy naphtha by providing optimal nutritional, moisture and aeration conditions while intensifying the activity of soil microorganisms.

In this study, to reduce heavy naphtha contamination in the soil, bioremediation treatments including biostimulation, bioaugmentation and integrated approaches were used. According to the results of changes in dehydrogenase and lipase activity in naphtha-contaminated soil, each treatment was able to reduce contamination individually, while the integrated treatment was both biostimulatory and bioenhancing treatments. However, in the integrated treatment, the efficiency of bioremediation process was higher, due to the simultaneous use of biostimulation and bioaugmentation treatments. The use of integrated treatment in soils contaminated with petroleum compounds, including heavy naphtha, can help to biologically eliminate these contaminants.

Periphyton is a complex biological community comprising microorganisms and organisms from different physiological groups that collectively attach to various submerged surfaces in wetland ecosystems. Periphytic biofilms play a critical role in the wetland ecosystem’s dynamicity and possess a considerable capacity for decontamination. The following article examines the various aspects of periphytic biofilms’ capacity for removing some of the most critical environmental pollutants, including organic pollutants, pharmaceuticals, heavy metals, microplastics, and excess nutrients. The paper provides comprehensive discussions on the critical pollutant removal mechanisms employed by the periphytic communities. Additionally, the paper endeavors to contribute to the available knowledge regarding utilizing and developing periphyton-derived bioremediation technologies by presenting the most recent research findings, discussing common challenges in periphyton’s biotechnological application, and delineating crucial research gaps to postulate future research questions. Applying periphyton in pollutant removal aligns with the most recent paradigm of bioremediation technologies advocating the use of microbial consortia instead of single microbial species. In this regard, research results convey that the simultaneous presence of multiple microbial groups together in a biological community (such as periphyton) increases the microorganisms’ resistance to unfavorable environmental conditions and enhances the biological community’s capacity for decontamination. Based on the studies presented in this article, periphytic biological communities can employ different mechanisms to transform and biodegrade a wide array of pollutants.

Petroleum contamination is treated by physical, chemical and biological approaches. The first two methods have limitations such as high costs, inefficacy and altering natural ecosystem. Today, biological treatment is a more interesting process to remove petroleum contamination. Bioremediation is a technique in which biological systems such as microorganisms are applied to destroy or transform (degrade) harmful chemicals. In recent years, employing hydrocarbon degrading bacteria to clean a petroleum contaminated soil has become a prevalent, efficient and economical technique that converts toxic wastes to non-toxic end products. This technique has reduced the harmful effects on health and ecology. Soil contamination with petroleum compounds such as heavy naphtha can threaten soil, environmental and human health. In bioremediation process, soil microorganisms use these hydrocarbons as a carbon source and, while making a microbial biomass, play a role in its decomposition and conversion to carbon dioxide. Bioremediation methods include biostimulation and bioaugmentation, which are promising methods for treating oil pollution. Application and comparison of various bioremediation methods such as biostimulation, bioaugmentation and integrated treatment was the main aim of this study to bio-remove heavy naphtha from contaminated soil. For this purpose, in a heavy naphtha-contaminated sandy loam, a variety of bioremediation treatments, including biostimulation (including supply of nitrogen-phosphorus elements, addition of manure and Tween 80 surfactant), bioaugmentation treatment (using a consortium of efficient bacteria) and integrated treatment (including all biostimulation and bioaugmentation treatments) were tested.

In this experiment, sandy loam soil was used. Heavy naphtha contamination was applied at a rate of 7% in soil samples and various bioremediation treatments were performed as mentioned above. This experiment was carried out in a pot scale (3 kg pots) based on split plot factorial design (pollution factor, bioremediation factor and time) with 3 replications, at room temperature for 120 days. During the experiment, the pots were aerated once a week and the soil moisture content was adjusted to 70-80% of the soil water holding capacity twice a week. For bioaugmentation of bacterial isolates, a consortium of Arthrobacter sp. COD2-3, Stenotrophomonas nitritireducens COD5-6، Stenotrophomonas asidamainiphila COD1-1 with a ratio of 5% V/W were used. In biostimulation treatment, cow manure with 5% W/W ratio was used. In NP treatment, which was related to the supply of nitrogen and phosphorus elements, N and P elements from sources of ammonium nitrate and potassium phosphate with a ratio of 20:5:1 (C: N: P) were used. Also, to use Tween 80 surfactant in the relevant treatments, a rate of 0.3% V/W was used. In the integrated treatment, all the mentioned treatments were used together to remediate oil contamination. On days 0, 5, 10, 15, 30, 45, 60, 90 and 120, samples were taken from each pot to measure the biological activity of basal respiration (BR) and substrarte-induced respiration (SIR).

The results showed that the bioremediation treatments reduced heavy naphtha contamination. Contamination also affected soil microbial activity, so that BR and SIR increased in all bioremediation treatments in the early days, but over time they decreased, due to the reduction of carbon source and also the reduction of soil nutrients. The amount of BR and SIR in the combined treatment changed from 0.67 to 0.53 and 3.30 to 2.73 (mg CO2 g-1 h-1), respectively. Also, the amount of petroleum compounds before and after bioremediation treatments showed that 81% of heavy naphtha was decomposed by the integrated treatment. Among the bioremediation treatments, the integrated treatment had a greater effect on the elimination of heavy naphtha contamination than the biostimulation and bioaugmentation treatments (p <0.01). The use of integrated methods not only increases the active population of microorganisms in the decomposition of petroleum compounds and provides optimal conditions for their activity, but also stimulates the native population of microorganisms and is convenient for removing petroleum compounds. It seems to be a good method.

According to the microbial respiration results in naphtha-contaminated soil, each treatment was able to reduce contamination on its own, while the integrated treatment was biostimulatory and bioenhancing treatment. However, in the integrated treatment, the efficiency of bioremediation process was higher, due to the simultaneous use of biostimulation and bioaugmentation treatments. The use of integrated treatment in places contaminated with petroleum compounds, including heavy naphtha, can help to biologically eliminate these contaminants.

Crude oil is a complex combination of many hydrocarbon and non-hydrocarbon compounds, including heavy metals, which affect the physical and chemical properties of the soil, cause the soil particles to stick and connect and then cause the soil to become stiff and impenetrable. Contamination of soil with petroleum hydrocarbons is a significant environmental problem, which has received remarkable attention in recent decades. Petroleum hydrocarbons are resistant and hazardous pollutants. Some petroleum hydrocarbons such as benzene are mutagenic and carcinogenic materials for humans. There are many physical and chemical methods to remediate oil-contaminated soils. Phytoremediation is a relatively new technology for refining contaminated soils in which resistant plants are used to remove or reduce the concentration of inorganic, radioactive, and organic pollutants, especially petroleum compounds, from the environment.

Sufficient amounts of about 50 kg of soil contaminated with petroleum hydrocarbons were collected from regions (0-30 cm soil depth) adjacent to the oil wells west of Kermanshah province. Uncontaminated soil samples were also taken from sites at the lowest distance to the contaminated sites. The aim of this study was to compare the efficiency of different plants to remove total petroleum hydrocarbons from oilfield soils. In this study, after determining the total amount of petroleum hydrocarbons, the contaminated and uncontaminated soils were mixed in 4 treatments with different weight ratios (0, 10, 25, and 35%). This experiment was established as completely randomized design with 3 replications for 6 different plants (Barley, Grass, Alfalfa, Hemp, Camelina, and Vicia ervilia). One treatment without plant was considered to remove soil matrix effects on petroleum hydrocarbon concentrations. Plants were harvested at the end of their growing season (90-120 days). Soils and plant samples from the experimental pots were analyzed for their important properties (including some physiological characteristics of the plants, as well as the percentage of reduced petroleum hydrocarbons in the soils). The gravimetric method was used to determine the concentration of petroleum hydrocarbons in the soil. After measuring the properties of the soil and plant, the normality of the data was checked by the Anderson–Darling test, and the homogeneity of the variance of the treatments was checked by using Levene's test. Analysis of data variance was done using ANOVA and average data comparison was done using LSD test at 5 and 1 percent probability levels (SAS 9.4 and SPSS 26).

In general, the growth of most plants showed a decreasing trend in proportion to the increase in soil pollution levels. However, the growth decline rates of different plants were not similar. Camelina was very sensitive to oil pollution and the plant could not tolerate pollution even at 10% level. After camelina, alfalfa was highly sensitive to oil pollution. The highest dry weight of the aerial parts of the hemp plant in the soil without oil contamination was observed at the rate of 111.22 grams in the pot. The leaf area of all studied plants in contaminated soils decreased compared to the control treatment (without contamination) so with the increase in the percentage of contamination, the leaf area of the plants was significantly reduced. The highest amount of leaf surface was observed in unpolluted soil and in the hemp plant. Except for the Camelina plant, which was completely destroyed at different levels of pollution, the rest of the plants showed a noticeable decrease in growth. The total petroleum hydrocarbons in soil were measured again 120 days after the start of cultivation, and its difference with the total amount of petroleum hydrocarbons at the beginning of cultivation was determined as the reduction of petroleum hydrocarbons and reported as a percentage. According to the mean comparison results, the percentage of reduced petroleum hydrocarbons was not significantly different among cultivated and non-cultivated treatments, although, it was significantly affected by soil pollution levels. Since all the studied soils contained natural bacteria and were not sterilized, the eliminated part of petroleum hydrocarbons is probably decomposed and removed by native bacteria in the soils. Therefore, the strengthening of native bacteria in these soils may increase the decomposition and degradation of petroleum hydrocarbons.

The results of this research show that the presence of petroleum hydrocarbons in the soil caused a decrease in growth and other physiological characteristics in all studied plants. Although the Camelina was able to germinate in soils contaminated with petroleum hydrocarbons, the presence of these pollutants in the soil prevented the optimum growth of the plant, so its use in subsequent studies of phytoremediation of oil-contaminated soils, was not recommended. The results showed that there is no statistically significant difference between cultivated and non-cultivated treatments at different pollution levels, and the reduction of the total petroleum hydrocarbons in the soil was probably done by native microorganisms in the soil. It is recommended to take into consideration the efficiency of the plant species used, the type of polluting hydrocarbons, and the duration of contamination in future research to obtain better results.

Phytoremediation is a method for decreasing lead contamination in soil and the use of chelates increases the efficiency of this method. In this study, phytoremediation efficiency of savory plant (Satureja hortensis L.) to remove lead from contaminated soil was investigated in the presence of chelates including ethylene-diamine tetra-acetic acid (EDTA) and diethylene diamine penta-acetic acid (DTPA) and organic acids including acetic acid (AA), citric acid (CA) and tartaric acid (TA) at concentrations of 0 and 10 mmol kg-1. The soil was amended with five levels of 0, 100, 200, 300 and 400 mg kg-1 lead from lead nitrate source. The experiment was conducted as factorial based on completely randomized design with three replications. The results showed that the shoot dry weight was higher in organic acids treatments than synthetic chelates, and increasing of lead concentration up to 300 and 400 mg kg-1 decreased shoot dry weight. Acetic acid significantly increased the available lead concentration in the soil and the highest amount was obtained at level of 400 mg kg-1 lead in soil. The highest plant extraction potential was observed with acetic acid at 100 mg kg-1. Organic acids showed more effective role in increasing the extraction of lead compared to the than chelates. The results of this study showed that Satureja hortensis had high ability to extract lead from soil at Pb levels of up to 200 mg kg-1. Due to the high translocation efficiency of lead from root to shoot, this plant can be used for soil remediation with application of organic acids.

The objective of this study was to eliminate chromium(VI) from a contaminated soil through reducing it to chromium(III) by immobilized Shewanella sp. bacteria on algae biochar and to investigate its accumulation in barley. A sandy loam soil was contaminated with 50 mg kg-1 Cr(VI) and incubated for two weeks. Then, the barley pot experiment in the contaminated soil was performed in the autumn of 1400 in the research greenhouse of University of Guilan in a completely randomized design with three replications. Treatments included Shewanella sp. (S), algae biochar (B), algae biochar + Shewanella sp. (BS), and immobilized Shewanella sp. bacteria on algae biochar (IB). Soil contaminated with Cr(VI) and non-contaminated soils were also included as positive (C+) and negative (C-) controls, respectively. After 30 days, the plant was harvested and dry weight of root and shoot were measured. Total chromium and Cr(VI) contents in the root and shoot of plant and also in the soil were measured. The Cr(III) content was calculated from the difference between the total chromium and the Cr(VI) contents. Growth ratio, Cr(VI) accumulation factor in roots and shoots and the transfer factor in plants were calculated. The highest and lowest amounts of Cr(III) in roots, shoots and soil were obtained in IB and C+ treatments, respectively. In Cr(VI) contaminated treatments, the highest and the lowest values of root and shoot dry weight were obtained in IB and C+ treatments, respectively. Cr(VI) reduction in soil in BS treatment was more than S and B treatments. The lowest and the highest plant growth ratios were obtained in C+ (23.8%) and IB (60%) treatments, respectively. The BS and IB treatments further reduced the transfer factor. Therefore, immobilized bacteria on biochar can be effective in remediation of chromium contaminated soils.

Phthalic acid esters are synthetic compounds used as emollients in polymer and plastic compounds. The entry of these compounds into the environment and the human food cycle and the development of a variety of cancers has raised global concerns. The purpose of this research was to investigate the concentration of phthalic acid esters (PAEs) in the soil exposed to the leachate (landfill) and finding a microbial consortium capable of the degradation of these pollutants. The concentration of phthalic acid esters in the soil was measured by the ultrasonic method and GC-MS. The results showed that the concentration of diethyl hexyl phthalate (DEHP) in soil (4.52 mg/Kg) was 6 times that of its international standard (0.7 mg/Kg). Microbial enrichment was performed in a mineral salt medium containing phthalic acid esters (30 o C and 120 rpm) and a microbial consortium capable of degrading phthalic acid esters was isolated. To investigate the biodegradation of phthalic acid esters by consortium, the residual phthalate concentration was extracted with ethyl acetate and measured by GC-MS. The results showed that the this consortium was able to degrade more than 96% of low molecular weight phthalates of dimethyl phthalate, diethyl phthalate and dibutyl phthalate (medium molecular weight phthalate) (30 o C and 120 rpm). In the case of DEHP (the world's most widely used plasticizer), the consortium was able to degrade it by 55% at 400 mg/L. Besides, phthalic acid esters separately were degraded almost completely by this consortium (5 days incubation, 30 oC, 120 rpm). Our results demonstrate the biodegradation of phthalic acid esters by this consortium and recommend its use for bioremediation of phthalates in contaminated soils.

The combination of phytoremediation and porous concrete is a new technology used as a natural purification of porous concrete and resistant plants to remove or reduce the concentration of pollutants. In this study, the performance of porous concrete as a bed and plant on reduction of urban effluent pollution has been investigated. A channel with dimensions of 9 meters length, 30 cm wide and 20 cm height was constructed along with the wastewater treatment lagoon of Isfahan University of Technology. Then, blocks were made of porous concrete with dimensions of 30 × 30 × 15 cm, and placed in the channel. The vetiver grass with two different densities (12 and 27 plants) were placed between the porous concrete blocks. After 5, 7 and 9 hours, the wastewater samples were taken from the inlet and outlet basins. The reduction of BOD, COD, TSS and total coliform during the 5 hours retention time, were 16.1, 27.5, 20.6, and 19.1 percent, respectively. In the retention time of 7 hours, reduction were equal to 20.5, 33, 26.1 and 25.3 percent, respectively. The reduction of BOD, COD, TSS and total coliform during the 9 hours retention time, were 25.9, 38.5, 31.9 and 30.5 percent, respectively. In general, this research showed the performance of system was optimistic in reduction of BOD, COD, TSS and Total coliform

 Surfactants as surface-active substances with combined hydrophobic and hydrophilic properties are widely used in various fields. In soil remediation processes these substances can be used to increase the availability of organic and inorganic contaminants to improve microbial decomposition of organic pollutants or heavy metals adsorption. In recent years, researchers have been seeking to produce and use surfactants that are more environment friendly. In this regard, produced biosurfactants by microorganisms are of special importance due to their environmental benefits. Microorganisms produce a wide range of biosurfactants. Biosurfactants are extracellular compounds that can combine with metals such as zinc, copper, and cadmium and can increase the solubility of these metals and reduce their toxicity. Negatively charged anionic biosurfactants such as rhamnolipids and lipopeptides can increase heavy metals availability by combining to metals and changing the properties of soil solution. In this study, the effect of surfactant application from Pseudomonas putida and Bacillus subtilis and some chelators include sodium citrate, humic acid and Na2-EDTA on soluble cadmium in a contaminated calcareous soil was investigated.

This study was conducted as factorial in a completely randomized design in laboratory conditions at several steps separately. A calcareous soil sample was contaminated with 15 mg kg-1 cadmium from the source of Cd (NO3)2. Contaminated soil incubated for 4 weeks at field capacity. Acid deposition method was used for surfactant extraction from culture medium of Pseudomonas putida KT-2440 and Bacillus subtilis 1795. The structure of extracted biosurfactants was investigated by FTIR. Equilibrium time was obtained by determining the amount of soluble cadmium at times 6, 12, 24, 36, 72 hours by adding 1mM sodium citrate, humic acid and Na2-EDTA to the contaminated soil (ratio of 1 to 5 soil to solution).The concentrations of 0, 0.1, 0.25, 0.5, 1 and 2 mM of humic acid, sodium citrate and Na2-EDTA were used to determine the appropriate concentration of each chelator. To investigate the interaction of chelators and biosurfactants on soluble cadmium, an experimental was conducted as a completely randomized design with factorial arrangement design. Experimental treatments consisted of three types of chelating agents (sodium citrate, humic acid, Na2-EDTA and control), two types of surfactants from Pseudomonas putida and Bacillus subtilis, and five concentration levels of the biosurfactants (0, 25, 50, 100 mg L-1).

The highest amount of soluble cadmium (11.59 mg L-1) was observed in Na2-EDTA treatment at 72 hours, which was significant compared to the other treatments. The lowest amount of soluble cadmium was obtained through application of sodium citrate (0.205 mg L-1) at 36 hours. In all studied concentrations, Na2-EDTA had the greatest effect and sodium citrate had the least effect on soluble cadmium. While the use of Na2-EDTA at all concentrations caused a significant increase in soluble cadmium, sodium citrate had no significant effect on soluble cadmium at studied concentrations. Humic acid at concentrations higher than 0.5 mM significantly increased the soluble cadmium. Increasing the concentration of humic acid and citrate from 1 to 2 mM did not show any significant impact on soluble cadmium. At all levels of biosurfactant application, Na2-EDTA and humic acid caused a significant increase in soluble cadmium concentration. In control and sodium citrate treatments, application of biosurfactants did not cause significant difference in the concentration of soluble cadmium. The highest amount of soluble cadmium was obtained as a result of the application of Bacillus subtilis surfactant and Na2-EDTA. However, increasing the concentration of Bacillus subtilis surfactant from 25 to 100 mg L-1 had no significant effect on increasing the efficiency of Na2-EDTA.  Pseudomonas putida surfactant had no significant effect on soluble cadmium in Na2-EDTA application. While in humic acid treatment, the application of the Pseudomonas putida surfactant at the highest concentration (100 mg L-1) increased the concentration of soluble cadmium. Using Bacillus subtilis surfactant did not have effect on soluble cadmium in application of humic acid.

Among the studied chelators (sodium citrate, humic acid and Na2-EDTA), Na2-EDTA had the greatest effect on soluble cadmium. While sodium citrate had no significant effect on soluble cadmium. Surfactants from Pseudomonas putida and Bacillus subtilis had different effects on increasing the efficiency of studied chelators and soluble cadmium in the studied soil. In Na2-EDTA and humic acid application, surfactant from Bacillus subtilis at a concentration of 25 mg L-1 and surfactant produced by Pseudomonas putida at a concentration of 100 mg L-1 had a significant effect on soluble cadmium, respectively. It seems using biosurfactants and chelators on increasing soluble cadmium in soil can be useful for phytoremediation purposes to increase its uptake by plant. However, further research is needed.

Heavy metal pollution in soil and water resources has become a serious problem not only in the production of healthy agricultural products, but also in the ecosystem health. Microbially induced calciumcarbonate precipitation (MICP) is a low-cost and environmentally friendly methods for reducing water resources and soil pollution. The aim of this study was to isolate native and efficient bacteria in the biological production of calciumcarbonate in order to remove zinc from contaminated solution. Isolating and screening native bacteria, producing urease and L-asparaginase, was accomplished.  Then, the changes in ammonia, pH and electrical conductivity (EC), as well as removal of zinc from the contaminated solutions were studied using these two efficient isolated bacteria in the presence of sporocarsina pasteurii. The results showed that in the presence of all three bacteria, the amount of produced ammonia, pH and EC in the culture media increased significantly compared to the ones in the control (without bacterial inoculation) (p < /em>≤0.05). The efficiency of isolated urease-producing strain in removal of zinc from the contaminated solution was almost equal to that of sporosarcina pasteurii, while the efficiency of isolated L-asparaginase-producing strain was more. Sporosarsina pasteurii removed 51.32, 65.94 and 70.36% and urease producing strain removed 65.49, 68.07, and 71.46 of zinc in the solutions containing 0.5, 2 and 4 mM Zn, respectively. However, L-asparaginase-producing strain removed 96.29, 93.88, 97.06 and 97.32% of zinc in solution containing 0.5, 2, 4 and 8 mM Zn, respectively. Therefore, it seems native urease- and L-asparaginase-producing bacteria can be useful and efficient in Zn bioremediation of contaminated solutions by MICP process.

Acenaphthene, a natural component of crude oil, is a carcinogenic compound and persistent to degradation. Bioremediation, which involves the use of living microorganisms for degradation and mineralization of contaminants, used to remove persistent contaminants such as Acenaphthene. Complete degradation of hydrocarbons is the result of different species activity that is known as a bacterial consortium. On the other hand, the low solubility of oil pollutants is a limiting factor in bioremediation. So, recently biosurfactant-producing bacterial consortia have been considered in the bioremediation to increase the bioavailability of oil contaminants. In the present study, Asenaphthene degrading bacteria were isolated by enriching the oil-contaminated soil and then, the biosurfactant-producing bacteria were screened based on the surface tension of the medium containing the isolates. After bacterial identification, degradation of Acenaphthene by isolates, consortium, and extracted biosurfactants from isolates, were investigated in the aqueous medium and soil. The results showed that both AP3 and BM1 could decompose Acenaphthene and produce biosurfactants. The AP3, BM1, and their consortium degraded 72.2%, 54%, and 100% of pollutants in the aqueous medium, respectively. The effect of biosurfactant extracted from AP3 on the degradation of Acenaphthene was more than the BM1 biosurfactant. Percentage of Acenaphthene degradation in soil by AP3 and consortium was 64.7% and 75.7% respectively, and the use of AP3 biosurfactant with the consortium led to complete degradation. 16S rRNA gene sequences of isolates showed that AP3 100% was compatible with Bacillus velezensis CR-502 (T) and BM1 99.5% was compatible with Pseudomonas putida ATCC 12633. Therefore, the use of a consortium and biosurfactants improve the biodegradation of Acenaphthene compared to inoculation of individual isolates.

Petroleum products are one of the most widely used chemicals in today's modern world. Petroleum hydrocarbons have become a global problem for the environment. These compounds are highly resistant to the environment and are harmful to human health. Application of bioremediation process to remove polyaromatic hydrocarbons from contaminated soils is one of the most economical and desirable options.The purpose of this experiment was to investigate the percentage of hydrocarbon pollution remove of polluted soil with hydrocarbons (crud oil) by sorghum, barely and bermudagrass with and wihout Psudomonas putida and Azosprillum brasilense.

In this study, simultaneous efficiency of phytoremediation and bioremediation in removing crude oil from soil was investigated. For this purpose, a factorial experiment was conducted in a completely randomized design with three replications. The treatments consisted of 3 levels of soil pollution to oil (0, 4 and 8% oil), 4 treatments of plant (no plant, bermudagrass (Cynodon dactylon), sorghum (bicolor Sorghum) and barely (Hordeum vulgare() and 3 treatments of bacteria (no bacteria, Psudomonas putida and Azosprillum brasilense). To do the experiment, samples of five kilograms of soil were polluted with different amounts of crude oil and poured into plastic pots. After 6 weeks and the equilibrium of polluted soils, these soils were inoculated with Pseudomonas putida and Azospirillium brasilense bacteria, then in polluted soils of inoculated with bacteria and no inoculated three gramineae species were planted. Ninty days after planting, plants were harvested.

The results showed that interaction effects of treatments were significant on crude oil removal percentage of soil in probability level of 1%. Removal percentage of crude oil by plant cultivation alone, inoculation of bacteria alone and combined application of plant and bacteria significantly increased compared to control. Cultivation of plants was more effective than soil inoculation with bacteria in removal oil pollution and plant increased bacteria function significantly so that, there were significant difference among treatments of plant alone, inoculation with bacteria alone and plant+ bacteria. The highest removal percentage was observed in combined application of plant and bacteria. At all treatments of soil inoculation with bacteria, with increasing levels of oil pollution, dry weight of plants decreased but, at each level of crude oil pollution, inoculation of soil with bacteria, the dry weight of shoot increased. Incubated soil with bacteria improved dry weight of shoot through removal of oil pollution in soil. With increasing level of crude oil pollution, concentration of leaf chlorophyll decrease significantly but, incubation of soil with bacteria increased it in fresh leaves of plants due to reduce the negative effects of oil pollution and supply nitrogen. With increasing levels of oil pollution, the mean of proline concentration in fresh leaves of plants was significantly higher than that of control. Its highest concentration (in each plant) was obtained at 8% of crude oil pollution. Inoculation of soil with bacteria in polluted soils and non-polluted soils increases the amount of proline in the leaves of plants. In each level of crude oil pollution, inoculation of soil with bacteria, the proline concentration of leaf of plants increased. The highest concentration of proline in the treatment of the highest oil pollution level (8% crude oil pollution) and inoculation with Pseudomonas putida was measured.

Establishment of plant with microorganisms can be considered as a key component of the strategy to remove hydrocarbons. Consequently, these bacterial and plant species can be used for the biodegradation of soils contaminated with crude oil.

 Biochar is known as a widely-use amendment in improving phytoremediation efficiency through the increase of plant growth; whereas its influence (either individually or in combination with bacteria) on the reduction of heavy metals (HMs) bioavailability of soil is an important advantage. This study was planned to assess the effects of separately and combined of biochar produced by forest wood wastes of hornbeam at three levels of 0, 2.5 and 5% of soil dry weight and Pseudomonas fluorescens bacteria on growth properties of potted white willow (Salix alba L.) seedling in a HM contaminated soil (Pb, Cu, and Cd). The variation of bioavailability (BA) and removal efficiency (RE) indexes, and bioaccumulation (BCF) and translocation (TF) factors also were analyzed in the treatments. The experiment was conducted under greenhouse condition for a 160 days’ period. The results showed that the variation in most growth components of seedlings was significant in the separate and combined treatments. The combined treatment of bacteria-biochar (at 5% level) increased the dry weight of leaf, shoot, root and total plant about 59, 36, 142, and 85% in comparison to the control (without the biochar and bacteria). In the biochar treatments, the BA, RE (except Pb), BCF, and TF (only in 2.5% of biochar) for Pb, Cu, and Cd were 13-57, 4-47, 29-60, and 16-33% lower than those in control, respectively. These indexes were improved by up to 191, 79, 84, and 13% in the bacteria-biochar treatment in compared to the individual application of biochar. In overall, according to our findings, the combination of biochar-bacteria led to the HMs bioavailability and improving the white willow function to eliminate soil HMs. So that, co-application of biochar and bacteria as soil amendments can increase growth parameters in white willow seedling and improve HMs bioavailability of plant in phytoremediation process.

The present study was conducted to investigate the possibility of growth of native bacteria isolated from some kerosene-contaminated soils in Khuzestan province for degradation of oil spills. After the primary stages of enrichment, isolation, and screening, bacteria were identified based on the gene sequences of 16S rRNA gene. The ability of native bacteria as the bacteria using hydrocarbons in the presence of oil products such as kerosene and crude oil at 1% concentration of solid and liquid minimum salt medium (MSM) was measured. A split-plot experiment with a factorial design was conducted with factors such as oil (kerosene and crude oil), bacteria, and time in three replicates, using the microbial inoculation inoculum (with a population of 108 CFU/ml) in both liquid and solid growth environments. The degradation ability of hydrocarbons in solid and liquid growth environments was investigated using colony diameter assessment and turbidity, respectively. In this research, five bacteria belonging to the genera of Microbacterium phyllosphaerae (ZS1.9), Bacillus megateriuns (ZS2.12), Staphylococcus epidermidis (ZS3.170), Streptomyces albogriseolus (ZS4.9), and Bacillus subtilis (ZS5. 210) were identified. The results revealed that the bacteria had the highest and lowest growth in the presence of kerosene and crude oil, respectively. Among the oil products used in this study, kerosene had the highest degradation rate. Furthermore, the ability of bacteria for degradation oil products increased by increasing incubation period. The findings of this study revealed the ability of different bacterial species in bioremediation of environmental pollution to various hydrocarbons.

Root stabilization of toxic metals by mycorrhizal plants is one of the protective mechanisms of symbiotic arbuscular mycorrhizal (AM) fungi in response to metal stress. Role of the glomalin as a specific glycoprotein of spore and hyphal cell wall of AM fungi can be remarkable in sequestration of toxic metals and reduction of stress effects on host plant. Considering this hypothesize, the study was conducted to investigate the role of glomalin produced by Rhizophagus irregularis fungus symbiosis of clover plant in root stabilization of Pb.

A pot culture experiment was performed as completely randomized block design by two factors including AM fungus (inoculated with R. irregularis and non-inoculated) and four levels of Pb+2 (0, 150, 300 and 450 µM) with five replications. For glomalin extraction, root samples were autoclaved at 121˚C with 50 mM sodium citrate buffer for 1 hr in three cycles. Glomalin concentration in the extracted samples were determined by ELISA method using monoclonal antibody 32B11. After precipitation of the glomalin and its digestion in concentrated nitric acid, Pb-sequestrated by the glomalin were measured. Shoot and root dry weights, root colonization percentage, shoot and root P and Pb contents, and plant uptake, extraction and translocation efficiency of Pb were assessed.

Shoot and root dry weights of mycorrhizal (M) and non-mycorrhizal (NM) plants were decreased by increasing of Pb levels. At the levels of 150, 300 and 450 μm Pb, shoot and root dry weights were decreased by 11.2%, 12.9%, 18.3% and 7.5%, 18.1%, 36.7% compared to the control (0 μm Pb), respectively. Shoot and root dry weights of M plants were increased by 24.9% and 43.2% compared to the NM ones. P contents of shoot and root were affected by AM fungus, so that the shoot and root P contents of M plants were increased by 32.2% and 45.8 % compared to the NM ones. At different levels of Pb, shoot and root Pb contents in M plants significantly were higher than NM ones. Maximum contents of Pb of shoot and root were recorded at level of 450 µM Pb in M plants which were increased by 46.5% and 80.7% compared to the NM ones at the same level. At the levels of 150, 300 and 450 µM Pb, the uptake efficiency of Pb in M plants was increased by 8%, 14.5% and 80.7% compared to the NM ones at the same levels. Based on ANOVA results, Pb-extraction and translocation efficiency were affected by Pb treatments. Pb-extraction efficiency of plants was increased as Pb concentration increased, so that the content of Pb-extraction efficiency at 450 µM of Pb was increased by 69.3% and 27.8% compared to the 150 and 300 µM of Pb, respectively. Plant Pb-translocation efficiency from root to shoot was decreased as Pb concentration increased. The percentage of root colonization was increased as the Pb concentration increased up to 300 µM Pb and then was slightly decreased as the level of Pb rose from 300 to 450 µM, but there was no significant difference between the levels of 150, 300 and 450 µM Pb. Glomalin production in root and Pb sequestrated by glomalin was significantly increased as Pb concentration increased.

Root colonization of clover plant by R. irreqularis led to improved growth and phosphorus nutrition of M plants compared to the NM ones, under Pb stress condition. Pb uptake was greater in roots than in shoots, therefore the clover plants played a more effective role in root stabilisation of Pb.

Crude oil is one of the most important sources of energy and its large scale production, transmission, consumption and disposal, making it one of the most important and common types of environmental pollution worldwide. Oil extraction and various oil products have led to spread of pollution in the soils around oil extraction and refining sites. During the production and transportation of crude oil, unsuitable operation and leakage may result in contamination of soil with petroleum hydrocarbons. Great concern in this case is the environmental risks of these pollutants. During the past decades, bioremediation of petroleum contaminated soil has been a hot issue in environmental research, and many bioremediation strategies have been developed and improved to clean up petroleum polluted soil. The aim of this study was to compare the effects of co-using of different bioremediation strategies on remediation of crude oil contaminated soil.

In order to investigate the effects of co-using phytoremediation and bioremediation in a crude oil contaminated soil, a factorial experiment in completely randomized design with three replications was conducted. The factors were three levels of crude oil contamination (0 wt% (C0), 2 wt% (C1) and 4 wt% (C2() and four treatments of remediation (Grass (B1), Alfalfa (B2), Grass + Pseudomonas Putida+ Phanerochaete Chrysosporium (B3), Alfalfa + Pseudomonas Putida+ Phanerochaete Chrysosporium (B4), control (B0)). For amendment of contaminated soil, soil samples were artificially contaminated with crude oil (from Tabriz Oil Refinery) and blended to soil (10% total quantity of soil spiked) then spiked soils were progressively mixed with unpolluted soil and homogenized. After preparation of the crude oil-spiked soil microbial inoculation were done and then the samples were packed into soil columns and then plants cultivation was done in soil columns (P.V.C pipes). At the end of growth period, some parameters were measured including residual Total Petroleum Hydrocarbons (TPHs) concentration, microbial basal respiration and dry weight of root and shoot. 

The results showed that TPHs concentration in C1 crude oil level by B3 and B4 remediation treatments decreased by 59% and 57%, respectively, and in C2 level B3 and B4 remediation treatments decreased TPHs content by 41% and 39%, respectively. B3 remediation treatment had the highest shoot and root dry weight and the lowest root and shoot dry weight observed from B2 remediation treatment. Shoot and root dry weight decreased with increasing crude oil contamination levels. The highest basal respiration rate was observed in B3 and B4 remediation treatments. In all of crude oil levels, there was not significant difference between B1 and B2 remediation treatments and control (B0) in basal respiration rate. In the highest crude oil contamination level (C2) the amount of carbon produced as CO2 increased because this level has higher concentration of oil pollutants and therefore has more required substrate for the activity of microorganisms, and consequently more microbial activities increased CO2 production. Compared to the control, the levels of crude oil contamination (C1 and C2) decreased dry weight of root by 46% and 61%, respectively and dry weight of shoot by 53% and 63%, respectively. Considering that the high concentrations of oil contaminants in the soil can lead to toxicity for plants and microorganisms and also hydrophilic properties of these compounds can decrease the availability of moisture and nutrients for plants root, therefore the growth of root decreased in oil contaminated soil. In lower level of crude contamination (C1), remediation treatments have more effective role in refining crude oil. This results from more plant growth and then more plant roots which increase the bioavailability of hydrocarbons by reducing the volume of soil micro pores. Also plants root release organic compounds which would increase the population and activity of soil microbes and these cause to increase of oil compounds degradation and elimination.

Experimental results showed that remediation treatments which contained bacteria and fungi with plants caused to more oil compounds elimination, microbial basal respiration and dry weight of root and shoot. Therefore, it can be found the importance of the presence of microorganisms and the microbial activity with plants in order to degrade and remove the soil oil compounds.
Keywords: Bioremediation, Oil pollution, Residual oil compounds, Microbial basal respiration

The presence of petroleum compounds in the soil causes environmental problems. Therefore, attempting to remediate contaminated soils is important. The present study was aimed at studying the effects of (1) different levels of biochar obtained from urban wastes and (2) the bacterium that degrades petroleum hydrocarbons on levels of nutrients in amaranth. The treatments were raw oil (0 , 2.5, and 5%; weight-based), biochar obtained from urban waste compost and fresh urban wastes (0, 1, and 2 %, weight-based), and bacterium (with and without Pseudomonas ). The results showed that with increasing the biochar level, the plant growth was promoted, with the highest values for growth parameters in plants treated with highest level of biochar. The dry and fresh weights of shoots in treatments with Pseudomonas florescence had statistically considerable differences compared to those in the other treatments. Overall, with the application of biochar and Pseudomonas, the levels of nutrients studied increased, and the maximum nutrient level was observed in the plants treated with the highest level of biochar. The highest P level (0.37%) was detected in plants treated with P1B0Ba1, and the lowest (0.23%) in plants treated with P2BM2Ba1. Moreover, the highest K level (5.16%) was recorded in plants treated with P2BM2Ba1, while the lowest (2.15%) was measured in plants treated with P0BM1Ba0 (no biological factor). The highest levels of Ca and Mg were found in treatments with biochar. The highest levels of Fe (1200.33 mg/kg) and Mn (441.5 mg/kg) were found in plants treated with P0B0Ba1, which had the biological factor, while the lowest was recorded in treatments where Pseudomonas florescence was absent. Accordingly, in order to increase the efficiency of soil remediation, it is recommended that organic matters, especially biochar, and bacterial treatments be exploited so that favorable conditions could be provided for plant growth and development.

Pesticides are considered as the most important pollutants in surface water and groundwater. Neonicotinoids are new group of insecticides, derived from nicotine. Their physicochemical properties render them useful for a wide range of application techniques, including foliar, seed treatment, soil drench and stem applications. Confidor, the representative of the first generation of neonicotinoid insecticides, was patented in 1985 by Bayer and was placed on the market in 1991. The Canadian Pest Management Regulatory Agency considers confidor to have high potential for surface water contamination, leaching to groundwater and persistence in soils. Biodegradation is one of the most effective ways to destroy pesticides in the environment. The application of Bioremediation techniques is taken into consideration as an option to reduce or remove pollutants from the environment due to their low cost, high efficiency and environmentally friendly features. Bioremediation by using microorganisms has not any adverse effect after cleanup. The accumulator microorganism species, haven’t pathogenic properties and aren’t the cause of disease on the other organisms. The selection of a biomass for using in bioremediation is very important, it should be abundant in environment and adapted to environmental conditions. The aim of this study was to investigate the ability of various species of Trichoderma fungi to remove Confidor from contaminated water influenced by variables like pH, concentration of the confidor and time.
In order to conduct this study three different fungal species belonging to the genus Trichoderma were used. The samples were transferred to PDA (Potato Dextrose Agar) sterile solid media for in vitro testing usage. The samples were kept in refrigerator at 4◦C temperature, after the fungal biomass reached to maximal growth; the colonies were transferred to new media and used in our experiments as resources. After complete fungal growth on the solid media, liquid media were prepared with the formula containing 250 g/l potato extract, 20 g/l dextrose and 0.25 g/l Tetracycline antibiotic (to prevent bacteria growth) in three pH (5,7,9) and three toxicant concentrations (1, 3 and 5 mg/l). Lactic acid and KOH (3%) were used to adjust pH in the prepared media. The degradation experiments were performed in a 50 ml falcon for 1 month. All experiments were maintained under similar conditions. The samples were shacken daily. After 1 month of incubation, aliquots (2 ml) were removed; centrifuged and the supernatants were used for the estimation of concentration of residual confidor by spectrophotometer. The results were analyzed by SPSS software.
According to the results T.harzianum with 60.34% confidor removal had the highest ability and T.tomentosum with 44.60% had the lowest ability to biological degradation of confidor from the polluted waters. The maximum confidor removal (75.89%) using T.harzianum was accrued to acidic media with 5 mg/l of confidor. The minimum confidor removal (53.09%) using T.asperellum was accrued to alkaline media with 1 mg/l of confidor. Using T.tomentosum the efficiency of confidor removal in media with pH=5 and concentration of 5 mg/l was increased by 10.95% and 15.63% compared to the environments with the concentrations of 3 and 1 mg/l, respectively. In the media containing T.harzianum, the percentage of confidor removal after 4 weeks was increased by 46.21% Compared to the first week. In the media containing T.harzianum, T.asperellum and T.tomentosum, the percentage of confidor removal after 4 weeks was increased by 46.21%, 37.06% and 32.84% respectively, Compared to the first week. Totally, the results showed that all the fungi species are capable to remove confodor. Toxicant concentration increasing from 1 mg/l to 5 mg/l, results in increasing the percentage of toxicant removal. The results of confidor removal from mediums with different pH demonstrated that in all studied fungi, toxicant removal at pH=5 is higher than other pH. The results obtained from this study confirm the hypothesis of positive effect of passing the time on confidor removal efficiency by different Trichoderma species.
In general, we can conclude that three species of studied Trichoderma in this research can be applied for bioremediation of agricultural waters which are contaminated by confidor. As a result, by collecting the agricultural water that are contaminated with confider and application of these fungi as biological purifiers, we will access to a considerable amount of non-conventional water resources to irrigate of downstream. It is noteworthy that Trichoderma species in addition to the biorefinery potential of pollutants , are able to improve soil structure and increase plant resistance.

Increasing growth of population and consequent development of industries and refinery plants cause high amounts of hydrocarbon pollutants enter to environment. Bioremediation or biological removal of petroleum hydrocarbons from soil or water is more efficient than the other physical and chemical remediation technologies. Indigenous bacteria are important because of their long term exposure and compatibility to hydrocarbon contaminants. Therefore, the aim of this study was isolation and comparison of oil consuming bacteria efficiency in the oil contaminated soils in southern of Tehran oil refinery plant. Six samples from the contaminated soil were collected and then the superior oil degrading bacteria were isolated through three laboratory steps: i) Isolation and purification of indigenous oil degrading bacteria in a soil extract agar as a selective media, ii) The study of efficiency of the isolates in a liquid mineral based media with 7% (V/V) of gas oil. iii) The comparison of the respiration rates of the isolates in a media containing 3% (W/W) gas oil. At the end of three steps, among all the oil degrading isolates, two isolates of BJ.1 and BM.1 with respiration rates of 2.1 and 1.8 mg CO2 per gram sand-perlite per month, were ultimately selected as the most powerful and efficient isolates for oil degradation, respectively.