JPH07136632A - Method of recovering soil by microorganism - Google Patents

Abstract

PURPOSE:To provide a method of recovering soil wherein the viability, growth and decomposing abilities of the anaerobic bacteria in the contaminated soil are enhanced. CONSTITUTION:A method of recovering soil by microorganism featuring the implantation into the contaminated soil of a solution having reducing power, a solution having oxygen dissolving ability or gas comprises scattering the aforesaid material over the surface of the contaminated soil for dispersion therein or drilling a well in the soil to disperse the aforesaid material therein through its bore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to purification of contaminated soil using microorganisms, and more particularly to a soil remediation method using anaerobic bacteria in contaminated soil.

[0002]

2. Description of the Related Art In recent years, with the progress of various industrial activities, waste water and waste materials have leaked to the soil and cause pollution. For example, as seen in hydrocarbon compounds such as petroleum and organic chlorine compounds such as trichlorethylene, soil pollution has become a serious problem as one of environmental pollution. Therefore, it is strongly desired to establish a technique for preventing the spread of pollution and regenerating the polluted environment. As an example of environmental restoration technology, there is a technology that decomposes and detoxifies pollutants by utilizing the function of microorganisms in soil, and aims to promote the decomposition of pollutants by strengthening the self-cleaning ability of the ecosystem. I am trying.

Gas production plant site, refinery contaminated soil, oil refinery site, fuel base site, pulp factory site,
There is a great need for soil restoration such as in semiconductor factories, and soil pollution not only hinders the reuse of land, but also poses a risk of causing pollution to spread further by flowing into the groundwater. As a soil pollution restoration means, there is a vacuum extraction method in which a pollutant is sucked from the soil. However, in consideration of cost, sensitivity, operability, and in the soil, decomposition by microorganisms is strongly desired.

[0004]

It is well known that microorganisms that decompose persistent compounds such as aromatic hydrocarbons and organochlorine compounds causing pollution in contaminated soil exist in the soil. ing.

In fact, the treatment of soil pollution using microorganisms has recently been carried out in various forms. However, most of them use aerobic bacteria, and decomposition by anaerobic bacteria is mainly in the form of closed system by bioreactor, and there are almost no examples of application to repair in-situ soil pollution. . The only thing that is exceptionally well known is the decomposition of TCE (trichloroethylene) using methane-utilizing bacteria. In this example, methane, which can be a nutrient, is introduced into the soil in order to enhance the activity of methane-utilizing bacteria.

As described above, there are very few cases where the anaerobic bacterium is used for repairing soil pollution, but this does not mean that the anaerobic bacterium is inferior to the aerobic bacterium in terms of decomposition of pollutants. On the contrary, anaerobic bacteria are more effective in decomposing certain pollutants (eg, tetrachloroethylene).

Therefore, in order to more effectively use the ability of these anaerobic bacteria, it is required to develop a technique for promoting the maintenance / improvement of the survival / proliferation and decomposing ability of the anaerobic bacteria in contaminated soil.

As described above, the degrading ability of many anaerobic bacteria is not sufficiently utilized for repairing soil pollution.
Therefore, first of all, it is necessary to investigate the reason why anaerobic bacteria are difficult to grow in soil and devise a measure to promote the growth.

FIG. 1 is a diagram showing the distribution of degrading bacteria in soil. (A) is an aerobic bacterium, and (b) is an anaerobic bacterium, which were measured by the dilution plate method. The data.

The environment for the growth of anaerobic bacteria is not necessarily suitable for these bacteria. As shown in FIG. 1, aerobic bacteria are considerably distributed to a relatively deep part in soil, but it was found that it is not necessarily a good environment for anaerobic bacteria.

The present inventors have found that the above-mentioned soil is unexpectedly in an environment where it is difficult for anaerobic bacteria to grow, and have completed the present invention.

[0012] It is an object of the present invention to provide a soil remediation method which enhances the ability of anaerobic bacteria to survive / grow and decompose in contaminated soil.

[0013]

The present invention is a microbial soil remediation method characterized by introducing a solution having a reducing power into a contaminated soil, and introducing a solution having an oxygen-dissolving ability into a contaminated soil. Is a method for remediating soil with microorganisms, and a method for remediating soil with microorganisms is characterized by introducing gas into contaminated soil. Both of these are methods for repairing contaminated soil, which makes the soil environment anaerobic and enhances the survival / proliferation and decomposing ability of anaerobic bacteria.

The soil remediation method having each characteristic will be described in detail. The soil remediation method uses a solution containing one or more of a salt containing Fe ²⁺ , formic acid, and oxalic acid as the solution having a reducing power.

This is a soil remediation method in which a solution having a reducing power is introduced into the soil to make the soil environment anaerobic and enhance the survival / proliferation and decomposing ability of anaerobic bacteria to remediate soil pollution.

The solution having reducing power used in the present invention may be any solution as long as it does not damage the ecosystem. For example, Mg, Ca, Zn, Fe ²⁺ , Sn, formic acid, oxalic acid and the like are included. Solutions etc.

As a method of introduction, a solution having a reducing power may be diffused into the soil from a well hole drilled in the soil, or a solution having the reducing power may be sprayed on the surface area of the soil to diffuse into the soil. You may let me. Nutrients or the like may be mixed and introduced into these solutions, or degrading bacteria may be mixed.

The decomposing bacteria and the substances to be decomposed are not particularly limited in kind, but the decomposing bacteria are anaerobic bacteria. The degrading bacterium already existing in the soil may be the target, or the bacterium introduced from the outside may be used. There is no problem even with unidentified bacteria, bacteria that have not been isolated, and symbiotic systems. For example, as a compound that decomposes an aromatic hydrocarbon compound, an organic solvent, an organic chlorine compound, etc., for example, "ANAERO
BIC TRANSFORMATION PROCESSES ； A REVIEW OF THE MICR
OBIOLOGICAL LITERATURE by John E. Rogers, Biology
Branch, Environmental Research Laboratory, August
1986. "p. 48-p. 61. According to Acetobacterium wo
odii, PelobacTer acidigallici, Proteus vulgaris, P
seudomonas sp. strain PN-1, Rhodopseudomonas palu
Others such as stris are known, and these can be used. Alternatively, the substance to be decomposed may be mixed with the medium and newly screened from soil or the like for use.

The above description of the degrading bacterium and the degrading object is the same in the case of the soil remediation method in which a solution having an oxygen-dissolving ability is introduced and a gas is introduced.

Next, a method of repairing soil contamination by introducing a solution having an oxygen-dissolving ability into the contaminated soil to make the soil environment anaerobic to enhance the survival / proliferation and decomposing ability of anaerobic bacteria will be described.

The solution capable of dissolving oxygen used in the present invention is
Any material may be used as long as it does not damage the ecosystem. For example, water, especially deaerated water is preferable.

As a method of introduction, a solution having an oxygen-dissolving ability may be diffused into the soil from a well hole drilled in the soil, or the solution having the oxygen-dissolving ability may be provided in the soil surface region. The solution may be sprayed and dispersed in the soil.
Nutrients or the like may be mixed and introduced into these solutions, or degrading bacteria may be mixed.

Furthermore, it is a soil restoration method of introducing a gas so as to make the soil anaerobic, and in particular, the soil restoration method is characterized in that the gas is nitrogen.

Any gas may be used as the gas for making the soil environment anaerobic in the present invention as long as it does not damage the ecosystem. Examples of the gas include nitrogen, other inert gases and carbon dioxide. . Of course, in some cases, these gases may be used in combination with the atmosphere.

Any method may be used for introducing the gas. For example, gas may be diffused into the soil through a well hole excavated in the soil.

The present invention is described in detail below with reference to examples, but these do not limit the scope of the present invention in any way.

[0027]

【Example】

Example 1 Soil in Japan's Kanto region, which had been contaminated with PCE (tetrachloroethylene) for 20 years, was sampled so as to minimize disturbance, filled in a model soil tank of 2 m by 3 m, and sealed for 1 month. I left it.

A water supply hole having a depth of 2.5 m and a diameter of 5 cm was lowered at each of the four corners of this soil tank, and each hole had a diameter of 0.
Vinyl chloride pipe 4 with many 5 cm water supply pits
A book was inserted, and the outer circumference of the pipe at the insertion portion was sealed with clay to form a water supply line. Further, a similar pipe having a diameter of 5 cm is installed in the center of the soil tank in the same manner as the water supply line to form a suction line. The water supply line is connected to a water supply pump to supply water at about 0.5 L / hr, and the suction line is connected to the pump to suck at a pump capacity of about 1 L / hr. A 0.5% FeSO ₄ .7H ₂ O solution was used as a feed solution (reducing solution).

After inoculation with the reducing solution, the soil near the water supply line was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 locations, and the test soil was suspended in the above-mentioned culture medium and suspended. The suspension was vortexed.
The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 2 shows the results of looking at the average number of bacteria and the removal rate of PCE concentration calculated in this way.

FIG. 2 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 2 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 1 The soil tank shown in Example 1 was filled with contaminated soil in the same manner as in Example 1, and then the average number of anaerobic bacteria and PCE.
The change in concentration was calculated by the method described in Example 1. The result is shown in FIG.

Example 2 Soil in Japan's Kanto region, which had been contaminated with PCE for 20 years, was sampled so as to minimize disturbance, and then filled in a model soil tank of 2 m square and 3 m deep and sealed 1
Left for a month.

At each of the four corners of this soil tank, a water supply hole having a depth of 2.5 m and a diameter of 5 cm is lowered into each of the four corners of the tank, and each hole has an outer diameter of 5 cm and a tip 1
Four vinyl chloride pipes provided with a large number of water supply pits having a diameter of 0.5 cm were inserted between m, and the outer circumference of the pipe at the insertion portion was sealed with clay to form a water supply line. Furthermore, diameter 5c
A similar pipe of m is installed in the center of the soil tank in the same manner as the water supply line to form a suction line. The water supply line is connected to a water supply pump to supply water at about 0.5 L / hr, and the suction line is connected to the pump to suck at a pump capacity of about 1 L / hr. A 0.1% formic acid solution was used as a feed solution.

After inoculation of the reducing solution, the soil near the water supply line was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 locations, and the test soil was suspended in the culture solution shown above. The suspension was vortexed.
The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. The average number of bacteria and the PCE removal rate calculated in this way are shown in FIG.
Shown in.

FIG. 3 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 3 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 2 The soil tank shown in Example 2 was filled with contaminated soil in the same manner as in Example 1, and then the average number of anaerobic bacteria and PCE.
The removal rate was calculated by the method described in Example 1. The results are shown in FIG. 3. Example 3 Soil in Japan's Kanto region, which had been contaminated with PCE for 20 years, was sampled so as to minimize disturbance, and filled in a model soil tank of 2 m square and 3 m deep and sealed. 1
Left for a month.

At each of the four corners of this soil tank, a water supply hole having a depth of 2.5 m and a diameter of 5 cm was lowered into each of the four corners of the tank, and each hole had an outer diameter of 5 cm and a tip 1
Four vinyl chloride pipes provided with a large number of water supply pits having a diameter of 0.5 cm were inserted between m, and the outer circumference of the pipe at the insertion portion was sealed with clay to form a water supply line. Furthermore, diameter 5c
A similar pipe of m is installed in the center of the soil tank in the same manner as the water supply line to form a suction line. The water supply line is connected to a water supply pump to supply water at about 0.5 L / hr, and the suction line is connected to the pump to suck at a pump capacity of about 1 L / hr. As a feed solution, a 0.1% formic acid solution and a 0.1% oxalic acid solution were used.

After inoculation of the reducing solution, the soil near the water supply line was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 locations, and the test soil was suspended in the above-mentioned culture solution. The suspension was vortexed.
The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. Changes in the average number of bacteria and the PCE removal rate calculated in this way are shown in FIG.

FIG. 4 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 4 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 3 The soil tank shown in Example 3 was filled with contaminated soil in the same manner as in Example 3, and thereafter, the average number of anaerobic bacteria and PCE.
The change in the removal rate was calculated by the method described in Example 3. The results are shown in FIG. 4. Example 4 Soil in Japan's Kanto region, which had been contaminated with PCE for 20 years, was sampled so as to minimize disturbance, and filled in a model soil tank of 2 m square and 1.5 m deep and sealed. It was left in a state and left for one month.

A 0.5% FeSO ₄ .7H ₂ O solution as a reducing solution was uniformly sprayed on the soil surface area of this soil tank at 5 L / day. After inoculating the reducing solution, the soil was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 places, the test soil was suspended in the culture medium shown above, and this suspension was shaken with vortex. Let Determine the number of anaerobic bacteria present in this suspension by MPN method 5
The average value of the points was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 5 shows the results of observing changes in the average number of bacteria and PCE removal rate calculated in this way.

FIG. 5 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 5 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 4 The soil tank shown in Example 4 was filled with contaminated soil in the same manner as in Example 4, and then the average number of anaerobic bacteria and PCE.
The change in the removal rate was calculated by the method described in Example 4. The results are shown in Fig. 5. Example 5 Soil in Japan's Kanto region that had been contaminated with PCE for 20 years was sampled so as to minimize disturbance, and then filled in a model soil tank of 2 m square and 1.5 m deep and sealed. It was left in a state and left for one month.

On the soil surface area of this soil tank, 5 L / 0.1% formic acid solution and 0.1% oxalic acid solution were used as reducing solutions.
Sprayed evenly throughout the day. After inoculating the reducing solution, the soil was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 places, the test soil was suspended in the culture medium shown above, and this suspension was shaken with vortex. Let The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 6 shows the results of observing the changes in the average number of bacteria and the PCE removal rate calculated in this way.

FIG. 6 (a) shows the culture days (days) and the PCE removal rate (%), and FIG. 6 (b) shows the culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 5 The soil tank shown in Example 5 was filled with contaminated soil in the same manner as in Example 5, and then the average number of anaerobic bacteria and PCE.
The change in the removal rate was calculated by the method described in Example 5. The results are shown in FIG. 6. Example 6 Soil in Japan's Kanto region, which had been contaminated with PCE for 20 years, was sampled to minimize disturbance and filled in a model soil tank of 2 m square and 3 m deep and sealed. 1
Left for a month.

At each of the four corners of this soil tank, a water supply hole having a depth of 2.5 m and a diameter of 5 cm was lowered into each of the four corners of the tank, and each hole had an outer diameter of 5 cm and a tip 1
Four vinyl chloride pipes provided with a large number of water supply pits having a diameter of 0.5 cm were inserted between m, and the outer circumference of the pipe at the insertion portion was sealed with clay to form a water supply line. Furthermore, diameter 5c
A similar pipe of m is installed in the center of the soil tank in the same manner as the water supply line to form a suction line. The water supply line is connected to a water supply pump to supply water at about 0.5 L / hr, and the suction line is connected to the pump to suck at a pump capacity of about 1 L / hr.

After inoculation with a solution having an oxygen-dissolving ability, the soil near the water supply line was excavated every 4 days, and 1 out of 5 locations
A 0 g soil sample was removed, the test soil was suspended in the culture medium indicated above and the suspension was vortexed. MP of the number of anaerobic bacteria present in this suspension
The average value at 5 points was calculated by the N method. Also PC
The E concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 7 shows the results of observing changes in the average number of bacteria and PCE concentration calculated in this way.

FIG. 7 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 7 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 6 The soil tank shown in Example 6 was filled with contaminated soil in the same manner as in Example 6, and then the average number of anaerobic bacteria and PCE.
The change in concentration was calculated by the method described in Example 6. The results are shown in Fig. 7. Example 7 Soil in Japan's Kanto region, which had been contaminated with PCE for 20 years, was sampled so as to minimize disturbance, and filled in a model soil tank of 2 m square and 3 m deep and sealed. 1
Left for a month.

At each of the four corners of this soil tank, a water supply hole having a depth of 2.5 m and a diameter of 5 cm was lowered into each of the four corners of the tank, and each hole had an outer diameter of 5 cm and a tip 1
Four vinyl chloride pipes provided with a large number of water supply pits having a diameter of 0.5 cm were inserted between m, and the outer circumference of the pipe at the insertion portion was sealed with clay to form a water supply line. Furthermore, diameter 5c
A similar pipe of m is installed in the center of the soil tank in the same manner as the water supply line to form a suction line. Connect the water supply line to the water supply pump and supply deaerated water at about 0.5 L / hr.
Connect the suction line to the pump and pump capacity is about 1L / hr
Aspirate.

After inoculation with a solution having an oxygen-dissolving ability, the soil near the water supply line was excavated every 4 days, and 1 out of 5 locations
A 0 g soil sample was removed, the test soil was suspended in the culture medium indicated above and the suspension was vortexed. MP of the number of anaerobic bacteria present in this suspension
The average value at 5 points was calculated by the N method. Also PC
The E concentration was measured by the hexane extraction method and ECD gas chromatography. The results of observing changes in the average number of bacteria and PCE concentration calculated in this way are shown in FIG.

FIG. 8 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 8 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 7 The soil tank shown in Example 7 was filled with contaminated soil in the same manner as in Example 7, and then the average number of anaerobic bacteria and PCE.
The change in concentration was calculated by the method described in Example 7. The results are shown in Fig. 8. Example 8 Soil in Japan's Kanto region contaminated with PCE for 20 years was sampled so as to minimize disturbance, and filled in a model soil tank of 2 m square and 1.5 m deep and sealed. It was left in a state and left for one month.

5 L of deaerated water was added to the soil surface area of this soil tank.
/ Spread evenly every day. After that, the soil was excavated every 4 days, and 10 g of soil samples were taken out from each of the 5 locations, the test soil was suspended in the above-mentioned culture solution, and this suspension was shaken with a vortex. The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 9 shows the results of observing changes in the average number of bacteria and PCE concentration calculated in this way.

FIG. 9 (a) shows the culture days (days) and the PCE removal rate (%), and FIG. 9 (b) shows the culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 8 The soil tank shown in Example 6 was filled with the contaminated soil in the same manner as in Example 6, and then the average number of anaerobic bacteria and PCE.
The change in concentration was calculated by the method described in Example 6. The results are shown in Fig. 9. Example 9 Soils in Kanto, Japan, which had been contaminated with PCE for 20 years, were sampled to minimize disturbance and filled in a model soil tank of 2 m square and 3 m deep and sealed. 1
Left for a month.

At each of the four corners of this soil tank, a water supply hole having a depth of 2.5 m and a diameter of 5 cm was lowered into each of the four corners of the tank, and each hole had an outer diameter of 5 cm and a tip 1
Four vinyl chloride pipes provided with a large number of air supply pits each having a diameter of 0.5 cm were inserted between m, and the pipe outer periphery of the insertion portion was sealed with clay to form an air supply line. Furthermore, diameter 5c
A similar pipe of m is installed in the center of the soil tank in the same manner as the air supply line to form a suction line. Connect the air supply line to the air supply pump to supply 100% nitrogen at about 0.5 L / min, connect the suction line to the pump and pump capacity about 1
Suctioned at L / min.

After the introduction of nitrogen, the soil near the water supply line was excavated every 4 days, and 10 g of soil samples were taken from each of the 5 locations, and the test soil was suspended in the above-mentioned culture solution and suspended. The liquid was shaken with vortex. The number of anaerobic bacteria present in this suspension was determined by the MPN method, and the average value at 5 locations was calculated. The PCE concentration was measured by the hexane extraction method and ECD gas chromatography. FIG. 10 shows the results of observing changes in the average number of bacteria and the PCE concentration calculated in this way.

FIG. 10 (a) shows the number of culture days (days) and the PCE removal rate (%), and FIG. 10 (b) shows the number of culture days (days) and the number of anaerobic bacteria (Cells / g). There is.

Comparative Example 9 The soil tank shown in Example 9 was filled with contaminated soil in the same manner as in Example 9 and allowed to stand, and then changes in the average number of anaerobic bacteria and the PCE concentration were taken in Example 9. It was calculated by the method described.
The result is shown in FIG.

[0062]

Industrial Applicability As described above, the method for repairing soil by the microorganism of the present invention introduces a solution having a reducing power into a contaminated soil, introduces a solution having an oxygen-dissolving ability, or introduces it into a gas in an anaerobic state. , Which activated anaerobic bacteria in the soil, promoted the decomposition of soil pollutant compounds, and enabled the repair of contaminated soil.

[Brief description of drawings]

FIG. 1 is a diagram showing the distribution of degrading bacteria in soil.

FIG. 2 is a diagram showing the results of average number of bacteria and PCE removal rate with respect to culture days in Example 1 and Comparative Example 1.

FIG. 3 is a diagram showing the results of average number of bacteria and PCE removal rate with respect to culture days in Example 2 and Comparative Example 2.

FIG. 4 is a diagram showing the results of average bacterial count and PCE removal rate with respect to culture days in Example 3 and Comparative Example 3.

FIG. 5 is a diagram showing the results of average number of bacteria and PCE removal rate with respect to culture days in Example 4 and Comparative Example 4.

FIG. 6 is a graph showing the results of average number of bacteria and PCE removal rate with respect to culture days in Example 5 and Comparative Example 5.

FIG. 7 is a diagram showing the results of average number of bacteria and PCE removal rate with respect to culture days in Example 6 and Comparative Example 6.

FIG. 8 is a graph showing the results of average bacterial count and PCE removal rate with respect to culture days in Example 7 and Comparative Example 7.

FIG. 9 is a diagram showing the results of average bacterial count and PCE removal rate with respect to culture days in Example 8 and Comparative Example 8.

FIG. 10 is a diagram showing the results of average bacterial count and PCE removal rate with respect to culture days in Example 9 and Comparative Example 9.

Claims (11)

[Claims] 1. A method for remediating soil with microorganisms, which comprises introducing a solution having reducing power into contaminated soil. 2. The soil remediation method according to claim 1, wherein a solution containing one or more of a salt containing Fe ²⁺ , formic acid, and oxalic acid is used as the solution having a reducing power. 3. A solution having a reducing power is sprayed on the surface area of the contaminated soil to diffuse into the contaminated soil.
Or the soil restoration method of 2. 4. The soil remediation method according to claim 1, 2 or 3, wherein a well hole is excavated in the contaminated soil, and a solution having a reducing power is diffused from the well hole into the soil. 5. A method for remediating soil with microorganisms, which comprises introducing a solution having an oxygen-dissolving ability into contaminated soil. 6. The soil remediation method according to claim 5, wherein water is used as the solution having an oxygen dissolving ability. 7. The soil remediation method according to claim 5, wherein deaerated water is used as the solution having an oxygen dissolving ability. 8. The soil remediation method according to claim 5, wherein the solution having oxygen-dissolving ability is sprayed on the surface area of the contaminated soil and diffused in the contaminated soil. 9. The soil restoration according to claim 5, wherein a well hole is excavated in the contaminated soil, and a solution having an oxygen-dissolving ability is diffused from the well hole into the soil. Method. 10. A method for remediating soil with microorganisms, which comprises introducing gas into contaminated soil to make it anaerobic. 11. The soil remediation method according to claim 10, wherein the gas to be introduced is nitrogen.