JP2015129744A - Farmland soil decontamination method and plant activation method utilizing organic acid and filamentous bacterium/actinomycete biofilm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a farmland soil decontamination method, utilizing an organic acid and a filamentous bacterium/actinomycete biofilm, which breeds filamentous bacteria, actinomycetes, etc., in an organic acid solution and extracts cesium from soil to decontaminate farm land.SOLUTION: A farmland soil decontamination method utilizing an organic acid and a filamentous bacterium/actinomycete biofilm includes: forming the biofilm consisting principally of filamentous bacteria, actinomycetes, etc., on a soil surface by impregnating soil contaminated with radioactive cesium with one of 0.1-50.0%, preferably, 0.1-10.0% lactic acid, citric acid, malic acid, tartaric acid, acetic acid, gluconic acid, oxalic acid, fumaric acid, succinic acid, mugineic acid, and glycolic acid, or a solution of a mixture thereof; and peeling the biofilm off so as to remove the cesium that plants easily absorb.

Description

  The present invention relates to an agricultural land soil decontamination method and a plant activation method using organic acids and filamentous fungi / actinomycetes biofilms.

Conventional decontamination techniques for farmland have problems such as the removal of soil, reversal tillage, spraying of adsorbents, and loss of important parts of farmland and changes in soil characteristics.
The extraction of cesium adsorbed on the soil was extremely difficult because it was finally taken into the layers and edges of clay and mica minerals and fixed electrically.

The prior art and its drawbacks are described below.
Heat treatment: The soil is heated to 1300 ° C. or higher in a rotary furnace to sublimate and separate cesium. Disadvantages of this method are extremely high cost, high temperature heat treatment, so that it is difficult to apply to farmland soil, and there is no portable type.
Classification treatment: Mixed classification involves wet classification including grinding by special pump classification, high-pressure washing, ball mill, etc. There is a case where heat treatment at about 700 ° C. is performed in a subsequent process. Disadvantages of this method are high cost, and it is difficult to apply to agricultural soil because fine particles are removed.
Chemical treatment: An organic acid such as oxalic acid is added and heat-treated at 85 to 90 ° C. to elute and recover cesium. Disadvantages of this method are high cost, and in the case of oxalic acid, it is necessary to make it harmless by post-treatment.

JP2013-217820A

  The present invention provides a farmland soil decontamination method utilizing organic acids and filamentous fungi / actinomycetes biofilm, in which fungi and actinomycetes are propagated in an organic acid aqueous solution, and cesium is extracted from the soil to decontaminate farmland. The purpose is to provide. At the same time, a plant activation method using biofilm is provided for uncontaminated soil.

Agricultural land soil decontamination method utilizing the organic acid and filamentous fungi / actinomycetes biofilm of the present invention, soaking agricultural soil such as paddy fields, fields, orchards contaminated with radioactive cesium in an organic acid aqueous solution, By forming a biofilm mainly composed of orbacteria and stripping the biofilm, cesium that is easily absorbed by plants is removed from agricultural soil such as paddy fields, fields, orchards contaminated with radioactive cesium .
The farmland soil decontamination method utilizing the organic acid and filamentous fungi / actinomycetes biofilm of the present invention is 0.1 to 50.0%, preferably 0.1 to 10.0% in soil contaminated with radioactive cesium. Soaked in an aqueous solution of any one or a mixture of lactic acid, citric acid, malic acid, tartaric acid, acetic acid, gluconic acid, oxalic acid, fumaric acid, succinic acid, mugineic acid, glycolic acid, and fungi on the soil surface By forming a biofilm mainly composed of actinomycetes and peeling off the biofilm, cesium that is easily absorbed by plants is removed from the soil.

  For paddy fields, this can be done simply by filling the organic acid solution, but for water-permeable soils such as fields and orchards, diatomaceous earth, pearlite, zeolite, zeolite water-absorbing materials, and water-soluble cellulose. A biofilm can be generated by holding an organic acid aqueous solution in a water-permeable soil by using a gelling agent of ether, carrageenan, or sodium alginate alone or in combination.

  Further, by removing the formed biofilm and then planting the plant, the biofilm and phytoremediation can be combined to efficiently absorb residual cesium in the soil.

  In the case of non-contaminated soil, the growth of plants can be accelerated or the yield of crops can be increased by cultivating the plant without removing it by forming a biofilm in the same way. You can also. This is due to the fact that biofilms extract active ingredients for plants such as potassium in the same way as cesium, and organic acids dissolve phosphorus and the like from soil efficiently.

  The aqueous organic acid solution also promotes strontium leaching. On the other hand, since sulfate ions supplied from fertilizers and the like are present in the soil, this is combined with strontium and precipitates as hardly soluble strontium sulfate. Thereby, absorption of radioactive strontium by a plant can be suppressed.

  The farmland soil decontamination method utilizing the organic acid and filamentous fungi / actinomycetes biofilm of the present invention can be decontaminated by immersing the soil of paddy fields, fields, orchards with an organic acid aqueous solution, Because it is the same substance as root acid (a mixture of organic acids) that comes from the roots, it is also a low environmental load. Furthermore, since the biofilm concentrates cesium, there is an effect that decontamination can be achieved if the biofilm is peeled off and removed. On the other hand, a plant can be planted after removing the biofilm and combined with phytoremediation to absorb and remove residual cesium. If sulfate ions are present in the soil as described above, strontium extraction and insolubilization can be achieved simultaneously.

  Plants can also be activated by forming biofilms by the same method on non-contaminated soil and extracting / concentrating components such as potassium that are effective for plants by the same mechanism as cesium extraction. Moreover, since this biofilm has water retention and the organic acid aqueous solution has an effect of dissolving phosphorus from the soil, these effects also work in a good direction for plant growth.

It is a photograph figure of a mode that a biofilm is peeled off. It is a photograph figure which shows the growth record of the rice of the 2nd year of organic acid treatment. It is a photograph figure which shows the difference in the yield difference of the rice of the 2nd year of organic acid treatment. It is a photograph figure which shows the difference in the yield of the rice ear of the 2nd year of organic acid treatment. It is a figure which shows the reduction | decrease of strontium in aqueous solution. It is a photograph figure which shows the growth record of the rice of the 3rd year of organic acid treatment. It is a photograph figure which shows the difference in the yield difference of the rice of the 3rd year of organic acid treatment. It is a photograph figure which shows the growth difference of the rice field demonstrated in the actual paddy field.

The farmland soil decontamination method using the organic acid and filamentous fungi / actinomycetes biofilm of the present invention will be described below.
The extraction of cesium adsorbed on the soil was extremely difficult because it was finally taken into the layers and edges of clay and mica minerals and fixed electrically.
On the other hand, if an organic acid or an ammonium salt aqueous solution is used, extraction to some extent is possible. However, for that purpose, it has to be heated to near 100 ° C., and it has been a problem that a large cost is required.
However, when soil contaminated with radioactive cesium is immersed in a low concentration of 0.1 to 50.0%, preferably 0.1 to 10.0% lactic acid or citric acid aqueous solution, filamentous fungi and actinomycetes on the soil surface A biofilm mainly composed of fungi was formed.
As shown in FIG. 1, when this biofilm was peeled off and soil particles were washed away as much as possible and the radioactivity was measured, about 300 to 1500 Bq of cesium per kg was detected.
This soil was derived from paddy fields, and the amount of radioactivity when dried was 3393 Bq / kg (1750 Bq / kg when wet).
These facts indicate that filamentous fungi and actinomycetes that cause cesium-concentrating action are efficiently propagated in the presence of a specific organic acid (root acid).
In addition, when representative filamentous fungi were identified, Penicillium svalbardense, Penicillium crustosum, Penicillium expansum, Talaromyces wortmannii and other blue molds were confirmed.

<Test 1>
In 2012, rice paddy soil was separated from Minamisoma City, Fukushima Prefecture, and rice was cultivated.
The amount of fertilizer allocated and the amount of zeolite used as a decontamination material were all set to the same conditions as in test cultivation conducted in Minamisoma City.
The soil was divided into two equal parts, one was immersed in a 5% aqueous citric acid solution at room temperature, and the supernatant was pumped out after 24 hours.
This operation was repeated once, and as much citric acid solution as possible was pumped out, and then an aqueous ammonia solution was added until neutrality.
This organic acid-treated soil continued fermentation activities with very active microorganisms for about a month, so rice was planted after waiting for its calming.
To compare the amount of cesium absorbed by rice, paddy soil in Minamisoma City, treated with citric acid, paddy soil in Minamisoma City, untreated, soil samples collected from Takatsuki Town, Yamagata Prefecture before the nuclear accident, hydroponics using liquid fertilizer Cultivation was carried out under four conditions of cultivation.
The results are as shown in Table 1 below.

有機酸処理を行った土壌で、稲のセシウム含有量が著しく増加していることが確認できる。上記の結果は、有機酸が植物のセシウム吸収に影響していることを示している。

It can be confirmed that the cesium content of rice is remarkably increased in the soil treated with organic acid. The above results indicate that organic acids affect plant cesium absorption.

To confirm this, soil was collected from Fukushima Prefecture (Fukushima City, Minamisoma City, Date City), and a cesium extraction confirmation test using organic acids was performed using citric acid and lactic acid.
Each soil was immersed in a 5% aqueous organic acid solution, and after 48 days, the aqueous solution was recovered and the radioactivity concentration was measured using a Ge semiconductor detector.
Table 2 shows a list of the collected soil samples.

On the other hand, as a result of measuring the radioactivity of the biofilm formed on the soil surface, it was confirmed that cesium was concentrated as described at the beginning.
Table 3 shows the radiation measurement results of the biofilm (paddy field soil lactic acid treatment).

以上のことは、植物の根酸（有機酸）が土壌菌類の活動を活性化させ、それにより抽出されたセシウムを植物が吸収していることを示唆している。

The above suggests that plant root acid (organic acid) activates the activity of soil fungi, and the plant absorbs the extracted cesium.

The biofilm formed on the soil surface in this test is mainly composed of filamentous fungi and actinomycetes, is relatively strong, and can be easily peeled off and treated.
If this property is utilized, it becomes possible to remove from the soil cesium that is easily absorbed by plants by filling the paddy field with an organic acid aqueous solution of about 5%, forming a biofilm, and peeling it off.
By utilizing this action, soil decontamination can be carried out efficiently at low cost and efficiently.
In addition, organic acid dissolves phosphorus from the soil, and one biofilm concentrates potassium, which is the same alkali metal as cesium. Therefore, coupled with the moisturizing effect of the biofilm itself, as shown in FIG. 2 and FIG. Plant growth promoting action is also expressed as a secondary effect. In addition, when the organic acid aqueous solution immersed in the soil in which the biofilm was formed was collect | recovered and the density | concentration of phosphorus was measured, 176 ppm was contained in the citric acid aqueous solution, and 26.3 ppm was contained in the lactic acid aqueous solution.

  In the case of water-permeable soil that cannot be filled with an organic acid aqueous solution, such as fields and orchards, when water is immersed in the organic acid aqueous solution, a water-absorbing material such as diatomaceous earth, pearlite, or zeolite is laid on the soil surface. Furthermore, by making the organic acid aqueous solution viscous by using a gelling agent such as water-soluble cellulose ether, carrageenan, or sodium alginate, the organic acid aqueous solution can be retained in the soil and the formation of a biofilm can be promoted.

  As shown in Table 1, cesium is extracted from the soil in which biofilm is formed, and most of this is water-soluble. Therefore, by planting plants, residual cesium after biofilm removal is also recovered. can do. That is, the efficiency of phytoremediation can be increased.

When an organic acid aqueous solution is added to the soil, strontium dissolves simultaneously. Since this strontium is combined with sulfate ions and precipitated as poorly soluble strontium sulfate, it is also possible to suppress the transfer of strontium to plants as a secondary effect.
FIG. 4 shows how strontium is reduced in an organic acid aqueous solution on which a biofilm is formed.
One liter of 1000 ppm aqueous strontium chloride solution was gently poured into biofilm-forming soil formed with lactic acid and citric acid, and water was collected every week to measure the strontium concentration.
Initially, the decrease in strontium concentration during the first 10 to 11 days was thought to be dilution with soil-containing water, but after the final water collection, the sample was thoroughly stirred and then water was collected to measure the strontium concentration As a result, a decrease of about 40 to 50% was confirmed at this stage. This decrease is consistent with the diluting effect of soil-containing water. That is, strontium that decreases in this experiment is the amount of precipitate removed, and dilution with soil-containing water means that the sample agitated. This means that the strontium ion of strontium chloride was precipitated as hardly soluble strontium.

  That is, the present invention includes four effects of 1) decontamination with biofilm, 2) decontamination combining biofilm and phytoreduction, 3) plant (crop) growth promotion, and 4) insolubilization of strontium. Therefore, it can be widely used for nuclear accident recovery.

<Test 2>
In order to confirm the multi-year sustainability of cesium extraction effect and plant growth promotion effect by organic acid treatment, rice cultivation in the second year was continuously cultivated in paddy soil in Minamisoma City, Fukushima Prefecture used in Test 1. .
The amount of fertilizer allocated and the amount of zeolite used as a decontamination material were all set to the same conditions as in test cultivation conducted in Minamisoma City. The results are as shown in Table 4 below.

二年目でも、藁および稲穂へのセシウムの吸収量が無処理土壌と比較して大幅に増加しているのが確認できる。

Even in the second year, it can be confirmed that the amount of cesium absorbed by straw and rice spikes has increased significantly compared to untreated soil.

<Test 3>
In order to confirm the continuation of the rice growth effect, a third year cultivation experiment was conducted. In the third year, in order to clarify the number of seedlings, seven seedlings were planted one by one, and the growth difference was confirmed. The soil used was the same as in the first and second years, but in the third year, cultivation was carried out without adding any fertilizer or zeolite.
As shown in FIG. 5 and FIG. 6, there is a difference in the harvest amount, and the weight of the rice ear is 1.5 times in the organic acid treatment section (calculated by subtracting the weight of the plastic bag). However, there is not much difference in the size of the plant itself that was confirmed by the second year, only the difference in the number of tillers.

<Test 4>
As a result of the rice cultivation experiment, a large difference in the yield was confirmed as described above. In order to obtain further confirmation, a cultivation experiment was conducted using an actual paddy field (Oga City, Akita Prefecture).
As shown in FIG. 7, there is a difference in the height of rice. The organic acid used for the main cultivation was lactic acid, and 1 liter of a 10% aqueous solution was sprayed per square meter. The yields per 36 strains in the lactic acid spray area and the control area are 1.85 kg and 1.52 kg, which is about 1.2 times.

  The present invention was carried out for the purpose of low-cost decontamination of cesium released by the accident at the Fukushima Daiichi nuclear power plant, but potassium and cesium, which are essential elements of plants, show almost the same behavior chemically. Therefore, it is effective in promoting plant growth and can be applied to the agricultural field.

Claims (7)

  Cesium that is easily absorbed by plants by soaking agricultural soil such as paddy fields, fields, orchards in organic acid aqueous solution, forming biofilms mainly composed of filamentous fungi and actinomycetes, and peeling off the biofilm A soil decontamination method using organic acids and filamentous fungi / actinomycetes biofilms, which is characterized by the removal of water from paddy fields, fields and orchards contaminated with radioactive cesium.   0.1 to 50.0%, preferably 0.1 to 10.0% lactic acid, citric acid, malic acid, tartaric acid, acetic acid, gluconic acid, succinic acid, fumaric acid, succinic acid in soil contaminated with radioactive cesium By immersing an aqueous solution in which any one of mugineic acid or glycolic acid or a mixture thereof is immersed to form a biofilm mainly composed of filamentous fungi and actinomycetes on the soil surface, A farmland soil decontamination method using organic acid and filamentous fungi / actinomycetes biofilm, characterized by removing easily absorbable cesium from soil.   A farmland soil decontamination method combining biofilm and phytoremediation, which efficiently absorbs residual cesium in soil by planting a plant after removing the biofilm formed in claim 1.   When soaking the soil with the organic acid aqueous solution of claim 1, a water-absorbing material of diatomaceous earth, pearlite, or zeolite, and a gelling agent of water-soluble cellulose ether, carrageenan, or sodium alginate are used alone or in combination. A method for forming a biofilm in which an organic acid aqueous solution is retained in a water-permeable soil.   A plant cultivation method for activating a plant by cultivating the plant with the biofilm formed by the method of claim 1, 2, or 4 as it is.   A plant cultivation method for activating a plant by cultivating the plant in the soil treated with the organic acid according to claim 1, 2 or 4.   A method for preventing elution of strontium, wherein when the soil is immersed in the organic acid aqueous solution according to claim 1, the dissolved strontium is reacted with sulfate ions to precipitate as hardly soluble strontium sulfate.

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