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ENGLISH VERSION: IMPROVEMENT OF SANITARY STATE OF SOILS IN THE POPULATED AREAS USING BIOREMEDIATION METHOD*
Kulahin O.O.
SE "Dnipropetrovsk Medical Academy of Ministry Public Health of Ukraine", Dnepropetrovsk
The aim of the research. Evaluation of the effectiveness of different types of biological products for purification of the soil, contaminated by oil products (OP) in the laboratory experiment and field conditions. Materials and methods. To achieve this aim, the experiment was performed in laboratory and field condttions, using two different types of biological preparations - a soiid mix (No.1) and an aqueous solution for irrigation (No.2). In the field experiments, the destructive activity of the preparation was studied on the industrial sttes of power electric substations in Dnepropetrovsk, polluted with booster oil (BO). In the laboratory experiment 3 variants of soil pollution with disel fuel (DF) with adding of different concentrations of the sorbent were used. Research results. During the research tt was found that on the sites of power substations, BO contents in all investigated samples taken from the surface (0-30 cm) and from deeper (30-60 cm) soil layers significantly decreased and made up 895.52-3988.03 mg/ kg, as compared with the analysis of samples taken in autumn of 2015 - 10 978.04-94 715.85 mg/kg, respectively. During the laboratory experiment, it was found that the greater the concentration of the sorbent, the more effective is its destructive activity, as a result of which on the 60h day of the experiment, the residual concentration of DF was 11.66-53.29% of the initial one. Conclusions. The use of biological products in the iiquid form, considering regularities of processes of fluid filtration in soils is appropriate in the contamination of surface layers (0-30 cm), in low - up to 12 000 mg/kg, concentrations of OP. In significant amounts of OP (up to 94.7 g/kg) and contamination of deeper soil layers, the most effective is the use of destructors on a solid matrix. Application of preparations No.1 and No.2 into the soil, contaminated with OP, in exposure of 2-9 months ensures its purification with the efficiency from 95.8 to 46.3°%.
Keywords: soil, diesel fuel, booster oil, bioremediation.
Relevance of the research
Over the recent decade, oil and oil products (OP), along with pesticides became one of the most common environmental pollutants. Considering the very rapid development of industry, increase of transport loads, global oil production on average increases by almost 2% yearly. At the same time, in the process of production, transportation and storage of OP, a great number of them penetrates into the environment [1, 2].
Almost 50% of oil and OP from all losses penetrate into the ground. Pollution of soil with OP affects all the components of ecosystem: soil microflora, fauna and flora [3]. Oil and OP are severely subjected to biological oxidation in soil environment [4]. It is highly important that in modern cities it is an additional factor of degradation of unstable artificial ecosystems and growth of risks in thr development of ecologically-caused diseases among the population [5].
Natural recovery of soil ecosystems, contaminated with oil and OP, is a long and difficult process [6]. Soils, under the influence of contamination with OP recover much worse than water and air environment, because they can accumulate and consolidate toxic substances [7]. It has been studied that natural transformation of OP in the soil as a result of accidental spills is a quite prolonged process, and amounts to 45 years or more [8].
For today, there is a number of methods for purification of soil, contaminated with oil and OP, namely: mechanical, physical, chemical, biological and integrated methods [9, 10]. Among them, biological method is the most promising, the essence of which is the use of microorganism-destructors (oil-oxidating bacteria). Surface-active substances of microbial origin (bio-SAS, biosurfactants) are also used - products of synthesis of oil-oxidating bacteria, mechanism of action of the latter is in the desorption and solubilization of hydrocarbons, as well as in stimulation of oil destructors activity [11]. The effectiveness of biological soil remediation method depends on many factors - the initial level of soil
contamination, type of bacteria-destructors, method of their application, time of exposure, external climatic factors and so on. Thus, the study of optimal conditions for the application of biological methods of soil purification from OP in the field and experimental conditions is an important ecological and hygienic task.
The aim of the research. Evaluation of the effectiveness of different types of biological products for purification of soil, contaminated with OP in laboratory experiments and field conditions.
Materials and methods of the research
To achieve this aim, the experiment was performed in laboratory and field conditions, using two different types of biological preparations - a solid mixture (No.1) and an aqueous solution for irrigation (No.2).
In the field experiment preparation No.1 was used, which includes active strains of carbohydrate-oxidative actinobacteria belonging to the species Dietzia maris, Gordonia rubripertincta, Rhodococcus erythropolis immobilized on oil-absorption sorbents (crushed charcoal, fraction of 1-5 mm). Destructive activity of the preparation was studied on the industrial sites of power electric substations in Dnepropetrovsk, contaminated with booster oil (BO) resulting from discharging-filling operations and leakage of BO through the cracks in the junction points of the separate gas point units. For the application of the biological product we selected 9 samples to determine the concentration of OP in the contaminated soils of the industrial sites. In mid-September of 2015, the experiment on purification of the contaminated with OP areas was launched. During this experiment, contaminated areas were dug up at the depth of 40 cm and hydrated. In the process of digging up, biological preparation No.1 of 2-4 kg per 1m2 was applied. Nine months later - in the middle of May 2016, 9 soil samples to establish the concentration of OP were selected again. Defining OP content was carried out by means of MBB 081 / 12-0116-03 [12].
* To cite this English version: O.O. Kulahin Improvement of sanitary state of soils in the populated areas using bioremediation method // Problemy ekologii ta medytsyny. - 2016. - Vol 20, № 1-2. - P. 23-25.
To carry out the laboratory experiment, preparation No.2 was selected, the latter was made on the basis of avirulent oil-oxidizing bacteria of the genus Pseudomonas fluorescens. In the course of the study, 3 variants of soil contamination with diesel fuel (DF) in quantities of 6.000, 12.000 and 22.000 mg / kg were used. Each of the variants was placed in a separate box, the latter in its turn was divided into four cells measuring 20*15*15 cm, in each of which 3.0 kg of soil were put. The experiment was performed using low-humus model, selected from places, remote from the roads, and from any other sources with the use of oil and OP. After distribution in a box of soil contaminated with DF into the cells, one was left without addition of the preparation (control), and into the other parts liquid preparation of bacteria-destructors in the amount of 30, 60 and 90 ml (10, 20, 30 mg/kg) with 10 g of turf was applied. Later, soil, preparation and OP were thoroughly mixed and hydrated to 60% of relative humidity. Control of OP content was performed on the 1st, 15th, 30th and 60th days by means of the method described above.
Statistical analysis was performed using software package Microsoft Excel 2010 and STATISTICA v.6.1®.
Results
During the research it was found that on the sites of electric power plants, BO contents in all investigated samples taken from the surface (0-30 cm) and deeper (30-60 cm) soil layers decreased significantly as compared with the analysis results of samples made in autumn 2015. Since spring 2016 the concentration of OP in the samples number 1, 2, 3, 4, 5, 6, 7 and 8 was 1984.12 mg/kg; 895.52 mg/kg; 3984.06 mg/kg; 2994.01 mg/kg; 3988.03 mg/kg; 2985.07 mg/kg; 1988.07 mg/kg and 996.01 mg/kg, respectively, this in its turn did not exceed the residual amount of OP from initial concentration of more than 16.6% (Table 1).
During the laboratory experiment, it was found that from the first to the fifteenth day, OP content in all investigated samples decreased significantly and made up not more than 60% of the concentration applied at the beginning of the experiment. We associate this phenomenon with the fact that volatile part of DF in surface contamination of soil evaporates actively into the atmospheric air.
Table 1
Dynamics of OP content in the soil in the field experiment.
No. of sample Depth of taking, cm Concentration of oil products, mg/kg (before bioremediation of soil) Concentration of oil products, mg/kg (after bioremediation of soil) Residual quantity from initial concentration, %
1 30-60 11 928.42 1984.12 16.6
2 30-60 10 978.04 895.52 8.1
3 30-60 94 715.85 3984.06 4.2
4 0-30 21 934.19 2994.01 13.6
5 0-30 83 000 3988.03 4.8
6 0-30 29 880.47 2985.07 9.9
7 0-30 33 932.13 1988.07 5.8
8 0-30 24 950.09 996.01 3.99
9 (background) 0-30 4990.01 3980.09 79.6
It should be noted that on the 60th day after the experiment, DF content in all control samples ranged from 54.11 to 49.07% of the initial concentration. The most notable effect of the destructive action of the sorbent was noted in the contamination of soil with the least studied concentrations of DF (6000 mg/kg), where the remaining amounts of OP as compared with the baseline were 31.64; 18.33 and 11.66% in concentrations of the sorbent of 30, 60 and 90 ml respectively. Variant
with 90 ml of sorbent also should be noted, where DF content decreased to 26.65% as compared with the initial concentration in soil contamination of 12000 mg/kg. In the relatively higher soil contamination with DF (22.000 mg/kg), destructive action of the sorbent was less effective and made up 50.87; 44.52 and 36.79% of the initial concentration in the content of sorbent of 30, 60 and 90 mL, respectively (Table 2).
Table 2
nics of OP content in the soil in the laboratory experiment, mg/kg.
№ Variants Day Residue, %
1 15 30 60
1 Control (6000) 5198.44 3598.92 3398.64 3098.76 51.64
2 Sorbent 30 ml 4997.00 3399.32 2499.25 1898.48 31.64
3 Sorbent 60 ml 5099.49 2997.60 1898.48 1099.89 18.33
4 Sorbent 90 ml 4898.04 2899.42 1598.88 699.79 11.66
5 Control(12000) 10794.60 7395.56 6997.20 6494.15 54.11
6 Sorbent 30 ml 10292.79 6896.55 5195.84 4497.30 37.47
7 Sorbent 60 ml 10995.60 7497.00 6695.98 6394.88 53.29
8 Sorbent 90 ml 10891.28 6298.11 4798.56 3198.40 26.65
9 Control(22000) 24992.50 12593.70 11392.02 10795.68 49.07
10 Sorbent 30 ml 20997.90 11289.83 11995.20 11193.28 50.87
11 Sorbent 60 ml 22986.20 10994.50 10292.79 9795.10 44.52
12 Sorbent 90 ml 19984.01 10393.76 9392.48 8095.14 36.79
Conclusions.
1. Investigation of soil purification from oil products in the laboratory experiment showed, that in their relatively small amounts (up to 12 000 mg/kg) primary purification of the upper layers of 0-30 cm in the initial phase of 15 days occurs largely at the expense of native flora and processes of evaporation of volatile fractions of OP and can reach 50% of the initial concentration. The use of biological liquid (№ 2) helps initiation of the process of OP destruction, the residual concentration of which on the 60th day of the experiment made up 11.66-53.29% of the initial one. The largest dose (30 ml/kg) manifests better efficiency in all studied ranges of contamination. The use of biological products in liquid form, considering regularities of processes of fluid filtration in soils is appropriate in the contamination of surface layers (0-30 cm) by OP.
2. In contamination of deeper soil layers (30-60 cm or more) with OP, the most effective is the use of microorganism-destructors immobilized on the oil-absorption sorbent, which allows "targetly" to place the preparation at the required depth and more accurately to calculate its required amount. Research of destructive action of the preparation No.1 in the field experiment has shown, that it is more effective in larger quantities of OP (up to 94.7 g/kg), and the final concentration of BO in 9 months after application of the sorbent makes up 4.216.6% as compared with the initial one.
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