CC BY
50
UDC 574.34: 579.64: 631.95 MICROBIOLOGICAL REMEDIATION OF PESTICIDE TERRITORIES IN OREL REGION
Gurin A.G., Doctor of Agricultural Sciences Burkov V.V., Post-graduate student Orel State Agrarian University, Orel City, Russia E-mail: brk eco@bk.ru
ABSTRACT
The article presents research data of the ability of microorganisms to remediate areas contaminated by pesticides on the example of the pesticide label Pivot (herbicide). Change of microorganism population's dynamics at various concentrations of pesticide is identified. It is concluded about the possibility of using microorganisms for reduction negative impact of pesticides on agro ecosystems, environment.
KEY WORDS
Micro-organisms; Remediation; Pesticides; Actinomycetes.
Farming for men is the main source of food and many types of technological resources. With the increasing demand of the population of the planet the need of this form of national economic activity has been increasing year by year. And, as we all know, the obtaining of large volumes of production leads to an increase in the number of chemicals employed in agriculture. Pesticides, fertilizers, desiccants, defoliants and other derivative chemicals are produced and used in large quantities, thereby greatly increasing the load on the environment, and as a consequence on the human body.
Pesticides occupy one of the first places on the toxicity and its effects on human being. Pesticides are very stable chemical compounds; they can persist in nature for a long time, being absorbed and accumulated in living tissues. The concentration of pesticides in organisms of predators, compared with the levels in water, soil and plants can grow in the hundreds of thousands and millions of times, due to the cumulative effect of these pollutants. As a result, even low concentrations of pesticides in the environment are harmful to organisms. Pesticides are found not only where they were used, but in all parts of the world -from North to South Pole. The negative effect of these substances on organisms is not immediate, but it is so powerful that many of the drugs have been banned by the international community. However, until now the use of pesticides is one of the most serious toxic impacts on human biosphere, and thus by human being himself [4].
Pesticides have high ability to migrate into the surrounding environment. The main methods for transferring are the following: adsorption by soil colloids, evaporation, dispersion transport, transport to surface waters, leaching [8].
Pesticides inevitably cause profound changes in the ecosystems in which they implement, as they have a wide range of toxic effects on all living organisms. In places where the treatment by massive pesticides was carried out the extinction of many species of animals and plants against which these treatments have not been targeted is usually marked. At the same time, there has not been a single case of a radical solution to the problem of a "pest" with pesticides. Usually there is a rapid development of pest resistance to any pesticide. Besides, the treatments are destroyed not only the pest, but also its natural enemies, which promotes rapid recovery of the pest population and its further build-up. In addition, the destruction of natural predators and parasites zoocenoses always causes outbreaks of pests that previously did not show themselves. Thus, the overall economic component of the use of pesticides turns out to be false, as it requires a huge cost to the synthesis of new drugs and the elimination of the consequences of their use [1].
It is natural that the issue of land clearing contaminated by pesticides is a priority in the greening of human activity.
The most appropriate method of cleaning of areas contaminated by pesticides is bioremediation, i.e. the use of living organisms to inhibit concentration and exposure to the toxicant. Application of microorganisms as destructors has shown a relatively high efficiency against pesticides [9].
In connection with the above stated the objective of the study is to assess the ability of groups of microorganisms to remediation of areas contaminated by synthetic pesticides.
Based on the objective the study has the following aims:
1. Determination of the species composition of soil micro-organisms;
2. The study of the influence of investigated pesticides on soil microflora;
3. Determination of microbial decomposers of pesticides;
4. Determination of absolute and relative absorption of pesticides by microorganisms;
5. Development of measures aimed at increasing the activity of the microorganisms destructors.
MATERIALS AND METHODS
The experiment was conducted at the laboratory of the Department of Agroecology and Environment of the Orel State Agrarian University in the period from 2010 to 2013. The selection of soil samples was carried out by the All-Russian Scientific Research Institute of leguminous and cereal crops.
The soil used in the experiment is gray forest medium loamy. Before laying of experience in the arable horizon it is characterized by the following indicators: potassium chloride - 5.55 H - 2.3, EKO - 19.3 mg-g soil ekv/100; V - 88,1%; Sorgue - 2.5, available phosphorus - 5.2 mg exchangeable potassium - 14.5 mg per 100 g of soil.
The selection of soil samples was carried out by the "envelope" method [2]. Instrumentation was sterilized before sampling.
To determine the species composition of microbial communities the method of dilution of suspensions was used [3], followed by plating on nutrient media MPA and SAA and the determination by microscopy [7].
As a test drug pesticide "pivot" was selected, referring to the herbicides used for growing other crops against monocotyledonous and dicotyledonous weeds.
Table 1 - Pivot product characteristics [5]
The name of the drug The active substance Hazard Class Application rate, l / ha
Pivot Imazethapyr, 100 g / l 3 0,8
The experimental setup was the following: Control; 1 IC - 0.8 l/ha; 10 IC - 8 l/ha; 100 IC - 80 l/ha. Repetition - 3. (PC - industrial concentration, converted to a Petri dish). Search of destructor microorganisms was carried out in the laboratory on M9 medium.
M9 is a synthetic analytical culture medium with the absence of free carbon. To prepare the media foundation 100 ml of distilled water was added: Na2HPO4 * 12H2O - 17,19 g, KH2PO4 - 3 g, NaCl 0,5 g, NH3Cl 1 g. For pouring into Petri dishes to 100 ml of the resulting solution was further added 1 ml of thiamine and MgSO4, 0, 1 ml CaCl2, 860 ml of water and 3% of agar agar medium for thickening. In control embodiment as the carbon source glucose is used in an amount of 40 ml. These plates with the medium have been autoclaving for 30 minutes at 120 °C [6]. Further microorganisms variants of the experiment are counted.
RESULTS AND DISCUSSION
As a result of experiment it was established the following. The species composition of soil microorganisms is represented by the following genera: Bacteria - Bacilus, Pseudamonas, Arthrobactor, Azotobacter, Rhisobium, Nitrobactor, Clostridium; Fungi -
Aspergillus, Penicillium, Trichoderma, Fusarium; Actinomycetes - Streptomyces, Actinomyces.
The impact of the drug "Pivot" on microorganisms is the following:
Table 2 - The number of actinomycetes on variants of the experiment, CFU*
Year Control 1 IC 10 IC
2011 5 days. 83,4 88,5 94,2
10 days. 71,5 91,4 101,8
2012 5 days. 84,3 89,7 98,2
10 days. 74,9 94,3 105,9
2013 5 days. 80,9 86,5 91,6
10 days. 70,3 89,8 97,8
* Colony-forming unit
Table 3 shows the following: In the version of the experiment the control of microorganisms reduces their numbers. So in 2011 the number of actinomycetes decreased from 83.4 to 71.5 CFU, and in 2012: from 84.3 to 74.9 CFU, and in 2013 from 80.9 to 70.3 CFU for 5 days.
For the remaining options a steady trend of growth of micro-organisms in a toxic environment is observed. Since the number of actinomycetes in option 1 IC has increased by 3.27 - 5.12%, at 10 IC: 6.77 - 8.06%, with 100 IC: 2.53 - 4.09%.
Judging by the analysis of the relative growth rates of colonies of microorganisms it can be said that, despite the increase in the absolute terms, there is a tendency to reduce the rate of growth of the colony with increasing concentrations of the drug. The best results are observed in the IC version 10.
On this basis the use of actinomycetes as disructers preparations based on imazetopira is grounded.
Table 3 - The number of bacteria on the results of experiment, CFU
Year Control 1 IC 10 IC
2011 5 days. 65,7 60,2 43,8
10 days. 47,6 43,7 29,4
2012 5 days. 61,9 56,3 42,4
10 days. 43,8 39,1 27,5
2013 5 days. 61,6 55,2 41,8
10 days. 45,2 45,4 26,8
As far as for bacteria are concerned the gradual degradation of the bacterial colonies is seen, including both time and drug concentration. Thus, in the first variant IC it is observed reduction of CFU from 60.2 to 43.7 for 5 days (2011) from 56.3 to 39.1 (2012) and from 55.2 to 45.4 (2013). The situation is similar with options of 10 and 100 IC. A direct increasing trend of reducing the number of bacteria with increasing concentrations of the drug is established.
Table 4 - The number of fungi as a result of experience, CFU
Year Control 1 IC 10 IC
2011 5 сут. 58,8 45,3 25,7
10 days. 71,6 43,2 20,4
2012 5 days. 61,1 47,5 27,8
10 days. 73,3 43,1 23,7
2013 5 days. 65,4 50,2 29,8
10 days. 70,6 46,4 24,6
The data of the fungal microorganisms in Table 5 determine following dynamics: only in the version control the increase in the number of fungal organisms is observed, in all other cases, the number is reduced. It should be noted that the time reduction is slightly, but when
the concentration of fluorine increases colonies degradation also increases dramatically. In the first variant, the number of IC fungal organisms decreased by only 2.1 CFU (2011) from 5 to day 10, but the difference between variants 1 IC and 10 IC was already 19.6 (5 days) and 22.8 CFU (day 10) . According to the results it can be said that the fungi are resistant to the action of fluorine in time, but can not withstand higher concentrations.
Based on these data, we can draw to the following conclusions:
1. Actinomycetes are the most active in terms of acquisitions (destruction) of pesticides. The drug stimulates biological activity. Thus at high drug concentrations tendency colony growth slows;
2. Bacteria and fungi do not show their ability to absorb the drug, negative population dynamics in all variants of the experiment, except for control is also marked;
3. The use of actinomycetes for the remediation of areas contaminated with imazetopirom (drugs Tactics, Tapir, Pivot, Viaduct, Pivalt, Zeta, etc.) is justified because of their potential for accumulation of the pesticide without breaking the positive dynamics of the population.
Based on the output the following suggestions to production may be given: implementation of measures aimed at increasing the activity of soil actinomycetes, the development of drugs based on actinomycetes to remediate the areas contaminated with pesticides, biotechnology research to increase the ability of microbial remediation destructors.
REFERENCES
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