| Bioremediation was reported as safe and environmental friendly technique to clean contaminated soil and water resources.Various plants and bacterial strains was utilized to remediate various chemicals.But main approaches of bioremediation were bio-stimulation and bio-augmentation.Bio-stimulation addressed the addition of different nutrients to degrade pollutants.These nutrients could add up in degradation in many ways;could enhance the microbial population of specified microbes could eat pollutants as a food or could enhance the number of indigenous microbial population adding in degradation of pollutants.On other hand bio-augmentation was addition of bacterial strain to enhance degradation process;these strains could be local or cultured.Local strains could be isolated from polluted sites;which could degrade pollutants in simpler forms that plants could utilize easily.For this purpose many researches were conducted in past and various bacterial strains were identified to remediate various pollutants.Atrazine was identified as herbicide and was utilized in maize crops to control weeds at initial stages.Atrazine mainly composed of N and some of the bacterial strains were also using this nitrogen as resource.Atrazine has almost 60 years of production history and being widely used as herbicide in all over the world.United States was at first rank in using of atrazine in the world,the annual amount of more than 30000t.Because the United States Environmental Protection Agency(EPA)had thought that economic benefits of atrazine usuage was more than the negative impacts of atrazine.So,to prohibit atrazine use was no issue in United States few years back.But in recent era,more and more herbicide because of security issues has been questioned and was prohibited under the environment of use but usage of atrazine increased year by year.European countries such as France and Germany were the first country to use atrazine as herbicide since early 1960s to the 1990s.But in 1991.scientist detected atrazine in tap water of Germany and other parts of world.Most awakening poinbt was that atrazine concentration in ground water was increasing year by year even after prohibition of atrazine use;the majority of water samples had a major metabolite of atrazine product.Over the same period.Atrazine metabolite DEA was detected in Paris ground water for seven years.French scientists found that Paris groundwater have been more than the parent atrazine content.So,Europe was the first region which started efforts to reduce atrazine use in agricultural lands and gradually reduced and eliminated reliance on atrazine.Many studies were reported to adopt various bioremediation strategies for ayrazine removal but no study was reported till date to analyze impact of various bioremediation techniques on soil and leachate in combination.Present study was conducted to design different bioremediation treatments and to check their efficiency in extensively polluted soil and leachate.Furthermore study also focused on significance of soil pH and temperature on atrazine bioremediation.Impact of each designed treatment was also observed on soil microbial communities.Treatments were designed under natural attenuation:bio-stimulation,bio-augmentation and combined bio-stimulation and bio-augmentation procedures.Animal manure,sawdust,sodium citrate and Arthrobactor sp.Strain DNS 10 were the basic elements used in all 15 treatments including control sample.Designed treatments were as natural attenuation(no addition of any element),bio-augmentation(addition of Arthrobactor sp.Strain DNS 10),bio-stimulation(addition of sawdust,animal manure' sodium citrate,AM+SD,AM+SC,SD+SC.AM+SC+SD)and combined bio-augmentation with bio-stimulation(DNS10+SD+AM,DNS10+AM+SC,DNS10+SD+SC,DNS10+SD,DNS10+AM,DNS10+SC,).On other hand.Sodium citrate,Arthrobactor sp.Strain DNS10,sawdust and animal manure was selected to analyse their impact on atrazine remediation under pH 5,7 and 9 and temperatures 20?,30?,and 40?respectively.Results concluded that atrazine remediation was generally optimized at pH 7 and 30? for all treatments except sodium citrate as soil treated with SC was not temperature dependant but at pH 5 remediation process was determined slower.Atrazine remediation in soil with no additional amendment was only 34%while in soil treated with Sawdust.DNS 10,sodium citrate and animal manure was 75.17%,89%,74.17%,and 76.83%at optimized pH and temperature.Overall atazine removal rate was significantly(?0.01)higher with increase in temperature at all selected pH.Different bioremediation strategies(Natural attenuation,bio-augmentaion,bio-stimulation and bioaugmentaion+biostimulation)were adapted to measure atrazine biodegradation potential of sodium citrate,sawdust,animal manure and Arthrobactor sp.strain DNS 10 solely and in combination as mentioned earlier.For this purpose initial atrazine concentration mixed in soil was double than normal application in field.Results concluded that Arthrobactor sp.strain DNS 10(bioaugmentaion)remediated 79%of atrazine while animal manure,sawdust and sodium citrate(biostimulation)degraded 74-74.4%of atrazine.When contaminated soil was treated with combined bioaugmentaion and stimulation;atrazine remediation potential was increased 74 to 84%.Addition of two nutrients alongwith Arthrobactor sp.strain DNS10 significantly(?0.05)enhanced its degradation ability as compared to single nutrient.Highest bioremediation rate(88.5%)was observed in soil microcosm treated with mix animal manure,sodium citrate and Arthrobactor sp.strain DNS10.But atrazine concentration in leachate was slightly lower thyan the atrazine concentration in soil samples.R square value for all bioremediation treatments between soil and leachate was 4-7.That means atrazine transfer rate from soil to leachate was very lower but could be long term and its proliferation could be more serious than atrazine pollution in soil. |
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