جستجوی مقالات مرتبط با کلیدواژه « bioremediation » در نشریات گروه « محیط زیست »

Soil pollution by heavy metals, especially in industrial regions is one of the main environmental problems. Cadmium (Cd) is a heavy metal that causes oxidative stress in plants and has many destructive effects on product quality. Nowadays, various methods are used to reduce the negative effects of high concentrations of heavy metals in the soil. In this regard, using biochar is a cost-effective and environmentally-friendly method and its influence on the reduction of heavy metals bioavailability of soil is an important advantage. Biochar is a carbon-rich material obtained by pyrolysis of biomass, such as agricultural residues and manures in conditions without oxygen or with limited oxygen content.

In this study, a factorial experiment was conducted in a completely randomized blocks design with three replications on Marigold (Calendula officinalis L.) medicinal plant with six levels of Cd (0, 1, 3, 5, 7, and 10 mg/l) and three levels of biochar (0, 1.5, and 3 w/w). The effect of experimental treatments was investigated separately and combined on the morphological (wet and dry weights of aerial parts and roots), physiological (the amount of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid), and biochemical (soluble sugar, catalase, peroxidase, and proline) characteristics of this medicinal plant. Means comparisons were done by Duncan's multiple range test at a probability level of 5%.

The results showed that different concentrations of Cd decreased the wet and dry weights of roots and aerial parts of the plant. The most reduction effect was related to the concentration of 10 mg/l of Cd. The interaction effect of biochar and Cd was significant only on the dry weight of aerial parts. The effect of stress caused by increasing the concentration of Cd on the plant's physiological processes was different. Considering that the first effect of Cd on the plant is the reduction of photosynthesis and chlorosis of the leaves, at the highest level of Cd, the amount of total chlorophyll decreased by 40% compared to the control sample, but the amount of carotenoid increased by 50% (p<0.05). The reduction of chlorophyll content under Cd stress can be due to oxidative damage and inhibition of different stages of chlorophyll synthesis. However, the increase in carotenoids in response to heavy metal stress occurs because these molecules, as part of the non-enzymatic antioxidant defense system, play a protective role against oxidative stress. In contrast, the use of biochar treatment caused a significant increase in the wet weight of aerial parts, the amount of chlorophyll a and carotenoid. Also, the interaction effect of the treatments indicated that at different levels of Cd, the characteristics of the dry weight of aerial parts, the amount of chlorophyll b, and the total chlorophyll increased with the increase in the biochar level. Among the investigated biochemical traits, the interaction effect of the treatments was significant only on the amount of soluble sugar (p<0.05) and catalase (p<0.01). This means that the absorption of Cd by biochar and the reduction of its toxicity effect on seedlings provided the conditions for more production of soluble sugar and catalase. In fact, biochar had high adsorption of Cd due to its high cation exchange capacity, high specific surface, and presence of functional groups.

In total, the results showed the biochar capacity to stabilize and inactivity Cd absorption. Therefore, the incorporation of biochar to soil can improve Cd bioavailability by plants in the phytoremediation, although the effect of type and plant variety on the amount of decreasing Cd stress should not be ignored.

An alternative and environmentally friendly method for purifying the environment from pollution is the use of biosurfactant derived from microorganisms. The advantage of biosurfactant is biodegradability, low toxicity, and effectiveness in increasing biological decomposition. Unlike chemical surfactants, surface active substances produced by microbes are easily decomposed, and for this reason, they are very suitable for environmental applications, especially bioremediation. The aim of this study was bioremediation and investigation of the absorption kinetics of heavy metals and Rhodamine B from water by biosurfactant produced from Pseudomonas aeruginosa bacteria.

In this study, a biosurfactant-producing bacterium that was isolated and identified as Pseudomonas aeruginosa HAK02 from the Kahrizak waste site in the south of Tehran was used to produce a surface bioactive agent to remove pollutants. Zeta potential test was performed to detect the load of biosurfactant produced and used in bioremediation. The amount of color removal was done by UV device and the removal of heavy metals was done by ICP_AES analysis.

Due to the negative charge of the substance, it was used to remove heavy metals and Rhodamine B cationic dye. Biosurfactant produced with Pseudomonas aeruginosa was able to remove 95% rhodamine B, 43% Cd2+, and 35% Co2+. Examining the kinetic model of absorption showed that better correlation with pseudo-second order kinetic model.

Bioremediation using surfactants to remove heavy metals and dyeing is a fast and environmentally friendly method. This sample is very suitable for the removal of Rhodamine B and has the moderate ability for heavy metals Cd2+ and Co2+.

In the last few decades, contamination of the environment especially the soil by toxic metals has been increased extremely at worldwide. Entrance of toxic metals into the soil from various sources is a constant and serious threat to the health of plants, animals and human societies. Bioremediation by using of the beneficial soil microorganisms improves the remediation efficiency of the metal contaminated areas and is a suitable alternative method for substitution of current physico-chemical strategies.

Arbuscular mycorrhizal (AM) fungi are found in virtually all ecosystems worldwide, including in soil contaminated with toxic metals. AM fungi sequestrate toxic metals at fungal intra- and extracellular structures by different mechanisms, so in addition to reduce their toxic effects on host plant prevent from their entrance in the food chain. This study has been addressed the role of glomalin as an important molecule of the cell wall of AM fungi spores and hyphae in soils contaminated by toxic metals.

The results showed that glomalin as a specific product of AM fungi, is present in the role of a heat shock protein as well a critical and main component of spores and hyphal cell wall.

Glomalin plays an essential and key role in maintaining and improving the soil health by reducing toxicity and availability of metals for symbiotic partner of AM fungi and other organisms.

Natural and human activities lead to soil degradation and soil salinization. In the last two centuries, world metal pollution level has increased extremely. Presence of some heavy metals in aquatic ecosystems is a constant threat to the health of human societies. The decrease of farmlands threatens food security. There are approximately 1 billion ha salt-affected soils all over of world, which can be made available resources after chemical, physical and biological remediation. Existence of many mines in the world and also in Iran and as a result, soil erosion and dust release from waste dams is matter of concern. Bioremediation using biological agents to detoxify and degradation of environmental pollutants- provides a suitable alternative method for substitution of current heavy metals removal strategies.

Daily as a result of extraction operations by cyanidation in Mouteh gold mining complex, waste water and waste soil sediment widely achieved. In this study soil samples were collected from Mouteh Goldmine tailing damp soil in September 2018. The collected soil samples were cultured in BG11 medium and incubated for microalgae identification and biomass production. Also 5 gr soil inoculated with 0.5 gr biomass and the physico-chemical characteristics of the soil including pH, Na+ and K+, Pb and Cd, before and after the inoculation of soil with Cyanobacteria were determined.

in this study, cyanobacteria Phormidium tenue Gomont, Osillatoria tenuis C.Agardh ex Gomont, Lyngbya aestuarii Liebman ex Gomont and green Algae, Scenedesmus obliquus (Turpin) Kützing were identified. Culture results of filamentous cyanobacteria on goldmine tailing damp soil showed that cyanobacteria can grow easily and produced a surface crust significantly. The results of the Physical analysis of the soil samples showed that O. tenuis decreased Na as a salinity element, and P. tenue absorbed high amounts of Pb as a heavy metal pollution element. Probably by using Mouteh Goldmine soil cyanobacteria, Osillatoria tenuis and Phormidium tenue for mine tailingdamp soil bioremediation, could play mine recovery from salinity and heavy metals and also preventing soil erosion and dust release from waste dams.

Generally, it can be concluded thatdue to the existence of many goldmines in the word and Iran, daily as a result of extraction operations by cyanidation and high toxicity of cyanide, environmental adverse effects are observed. Dust release from waste dams can be affected health of living organisms like mining workers, plants and even soil microalgae which are close to the mine. By soil goldmine bioremediation can be processed biological resuscitation faster. The research results of African goldmine researchers on soil samples showed that cyanobacteria produced a surface crust significantly, that with the results of this research based on the growth of Phormidium tenue in the mine and producing a surface crust is consistent.

Petroleum hydrocarbon pollutants are one of the hardest compounds in terms of decomposition and control and classified as stable and important organic pollutants that have adverse effects on human health and the environment and combating environmental pollution caused by them is an important issue for the world and human societies. Although the removal of these pollutants from the environment is a major problem, biodegradation (which uses natural microbial biodegradation activity) is an ecofriendly and economical approach to control these types of contaminants and has become a pivotal method of cleaning up environments contaminated with petroleum hydrocarbons. The present study provides a comprehensive, uptodate and efficient review of the bioremediation of petroleum hydrocarbon pollutants, taking into account the hydrocarbon alterations in microorganisms with a particular focus on the new insights gained in recent years. Also, the metabolism of hydrocarbons in microorganisms has been described by reviewing research presented in recent years. The results of studies show well that petroleum hydrocarbon pollutants are biodegradable using some microorganisms such as oleophilic and their removal by this method is cost-effective and economical. Microbial biodegradation of petroleum hydrocarbon contaminants uses the enzymatic catalytic activities of microorganisms to increase the degradation of contaminants several times more than traditional methods

Bioremediation is an approach that exploits the ability of microorganisms to increase the rate and extent of degradation of pollutants and thereby removing pollutants from the environment. The moisture content and temperature are of the main environmental factors affecting growth and activity of microorganisms and accordingly affecting the efficiency of organic pollutant biodegradation.

To study the effect of these two factors a factorial experiment was carried out as completely randomized design with three replications. The factors were moisture in three levels (30%, 55% and 80% of Field Capacity), temperature in three levels (25, 30 and 35 degrees of Celsius) and inoculation with bacteria in two levels (with and without inoculation by Pseudomonas putida) which were triplicated.

The results showed that highest biodegradation rate was observed in the treatment with the moisture content of 55% F.C, temperature of 30 degrees of Celsius and inoculation with Pseudomonas putida which was 92.8% and the lowest biodegradation rate was observed in the treatment with the moisture of 30% F.C, temperature of 30 degrees of Celsius and without inoculation which was 42.3%.

These results shows that the optimization of the environmental conditions in bioremediation process may lead to 50.5% increase in the efficiency of removal.