BREUS, Vladimir Andreevich (ul. Chuikova, 16-29Kazan, 6, 42013, RU)
NEKLYUDOV, Sergey Alexandrovich (ul. Krasnaya Pozitsiya, 15-52Kazan, 3, 42007, RU)
BREUS, Irina Petrovna (ul. Khasana Tufana, 27-7Kazan, 9, 42003, RU)
BREUS, Vladimir Andreevich (ul. Chuikova, 16-29Kazan, 6, 42013, RU)
NEKLYUDOV, Sergey Alexandrovich (ul. Krasnaya Pozitsiya, 15-52Kazan, 3, 42007, RU)
| What is claimed is: 1. The method of creation of protective hydrocarbon-impervious screen (barrier) preventing downward migration of hydrophobic contaminants in soils / subsoils, comprising the formation of liquid capillary screen wherein natural mineral and/or organic sorbents with high water retention ability are inserted into the upper layer of a soil / subsoil which is subsequently wetting up to field capacity. 2. The method of creation of protective hydrocarbon-impervious screen (barrier) as is claimed in claim 1 wherein used mineral sorbents are zeolites, clays or diatomite in quantities of 1-33% from the mass of a dry soil. 3. The method of creation of protective hydrocarbon-impervious screen (barrier) as is claimed in claim 2 wherein sorbents are inserted in the mixture with a soil as a layer of 20- 25 cm. 4. The method of creation of protective hydrocarbon-impervious screen (barrier) as is claimed in claim 2 wherein the organic sorbents are peat, cellulose, lignin, sawdust, crushed bark, straw, biomass of crop and wild plants or rubber powder. 5. The method of creation of protective hydrocarbon-impervious screen (barrier) as is claimed in claim 4 wherein sorbents are inserted as a separate layer of 5-20 cm under the soil layer or under the soil-mineral sorbent mixture as claimed in claim 2 with thickness of 5-20 cm. |
The invention relates generally to the methods of soil / subsoil and groundwater protection from contamination by oil and petroleum products and particularly, to the methods of creation of protective hydrocarbon-impervious screens (barriers) under construction of oil storages, petroleum pipelines, sludge collectors and others.
The methods of restriction of migration of liquid contaminants in a soil / subsoil are known based on formation of solid or liquid impervious screens, impermeable or semipermeable.
The solid impervious screens are formed on the basis of solutions / suspensions of chemicals capable to harden or suspensions capable to clog soil pore space.
The method of creation of an impervious screen using water compositions of chemicals capable to gelling or Portland cement grout, is disclosed (U.S. Pat. No. 5002431 , publ. 26.03.1991 ).
The soil treatment process providing usage of a cross-linked foamed polymer gel for blocking the flow of a fluid migrating in a soil is known (U.S. Pat. No. 5462390, publ. 31.10.1995). Like the method described above, here the created protective screen practically completely stops the migration both hydrophilic (water and water solutions) and hydrophobic (hydrocarbons) fluids.
The method of creation of an impervious screen by clogging soil / subsoil pore space using water mixture of clay and waste products from mining industry is known (USSR Pat. No. 1749349, publ. 23.07.1992).
All above-mentioned methods are directed on the formation of screens (barriers) impermeable or semi-permeable for fluids, including water and water solutions. This causes changing physical properties of soils / subsoils and their water regime as a consequence. As a result, over-wetting and water-logging of a soil are possible which lead to depression of indigenous microflora and fauna and therefore to the loss of soil fertility.
The methods of prevention of fluid migration by means of formation of a hydraulic barrier were also proposed (USSR Pat. No. 2141441 , publ. 20.11.1999; U.S. Pat. No. 6688812, publ. 10.02.2004). Such a barrier is formed by water injecting into the treated contaminated zone through the system of pipes or wells. Disadvantages of these methods are the necessity to have engineering equipment for the treated site and to keep permanently the required pressure in the hydraulic barrier; the dramatic increase watering of a treated soil / subsoil is the additional disadvantage.
In U.S. Pat. No. 5988950, publ. 23.11.1999, the method nearest to the proposed subject of invention is described. In that method a hydrophobic liquid barrier created for blocking vertical migration of pollutants is based on action of capillary forces. In the soil a system is formed consisting of soil itself and of hydrophobic substance entering soil capillaries. Thereby the barrier is formed preventing upward migration of water soluble contaminants through soil pores. Unfortunately this barrier cannot block migration of hydrophobic contaminants. Moreover it itself may cause secondary soil and groundwater pollution, because for its forming environmentally hazardous compounds (petroleum and mineral oils) are used.
The aim of the present invention is the creation of a barrier preventing downward migration of hydrophobic contaminants in a soil / subsoil.
This result is achieved by inserting into the subsoil natural mineral and organic sorbents followed by soil wetting up to the field capacity. Hereby the sorbents with high water retention ability are chosen. Further keeping the soil field capacity is realized by periodic wetting soil surface depending on the intensity and quantity of atmospheric precipitation.
The created sorption-capillary screen (barrier) blocks the downward migration of liquid and volatile hydrophobic fluids into the lower soil layers and groundwater but remains permeable for water and water solutions. It has the following advantages as compared with barriers - analogues of invention: high retention efficiency in regard to hydrophobic contaminants; preservation of soil / subsoil water-physical properties; low cost and environmental safety owing to usage of inexpensive and environment friendly materials and low expenditures under realization of this method.
The efficient immobilization of hydrophobic contaminants by means of such a sorption-capillary barrier is achieved owing to two simultaneous effects: a) the increase of hydraulic resistance of a water-saturated soil media towards filtration of hydrophobic fluids due to the sorbent inserting into the soil, and b) the essentially higher sorption capacity of inserting organic sorbents towards hydrophobic contaminants as compared to soil / subsoil itself. In the proposed method such mineral sorbents as zeolites, clays, and diatomites, and such organic sorbents as peat, cellulose, lignin, sawdust, crushed bark, straw, rubber powder, and biomass of crop and wild plants, are used.
The method comprises the steps of: i) applying mineral and/or organic sorbents into the upper (0-25 cm) soil layer, followed by ii) wetting of a soil surface up to the field capacity.
According to the present invention the sorbents can be inserted into the soil according to three patterns.
Pattern No.1 (Fig. 1) proposes using only mineral sorbents which are inserted as a layer (0-25 cm) (2) into the upper soil layer with h = 25 cm (1 ) as a mixture with the whole soil at sorbent/soil ratio from 1 :99 to 1 :2. The sorbents are added using two ways: by ploughing up followed by harrowing, or by inserting the mixture of previously removed soil layer (0-25 cm) with sorbents.
In accordance with Pattern No.2 (Fig. 2) the layer of organic sorbent(s) (4) (h = 5-20 cm) is placed under the upper soil layer (1). To do that, first the upper (5-20 cm) soil layer is excavated, then the layer of organic sorbent(s) is settled, and finally the removed soil layer is returned as the covering layer.
The application of Patterns No.1 and No.2 is sufficient for the complete retention of hydrophobic contaminants in the 0-25 cm layer of "heavy" (both clayey and loamy) soils.
For "light" (sandy and sandy loam) soils, the combined Pattern No.3 (Fig. 3) is recommended. It comprises the formation of upper soil layer (2) from the mixture of a mineral sorbent with soil (sorbent/soil ratio from 1 :99 to 1 :2), and the layer of an organic sorbent (4). In Fig. 3 the value h = 25 cm is the thickness of joint layer composed of two different sorbents. The sorbents are applied as following: i) previously the upper soil layer is excavated up to the depth of 5-20 cm, and the removed soil is mixed with a mineral sorbent in required proportion, ii) then the layer of an organic sorbent is laid on the bottom of pit (thickness of sorbent layer is 5-20 cm), and iii) the prepared mixture of soil with a mineral sorbent is placed on the surface of an organic sorbent as a covering layer. Irrespectively of used pattern, soil wetting by water (3) up to the field capacity is performed At this stage, in the pore space of inserted sorbents the hydrophilic capillary barrier is formed, which prevents the downward migration of hydrophobic contaminants in a soil / subsoil
Example 1 (corresponds to Pattern No 1 )
In a field stationary lysimeter filled by leached chernozem the upper soil layer (thickness 25 cm) was removed and subsequently mixed with zeolite containing material of Tatarsko-Shatrashansky deposit (soil/sorbent ratio of 99 1 ) The mineral composition of zeolite containing material clinoptilolite - 12%, montmoπllonite - 20%, quartz - 18%, calcite - 18%, opal/cπstobalite - 26% The soil-sorbent mixture was returned in the lysimeter and thereupon the soil was wetted up to field capacity Then the mixture of liquid hydrocarbons (diesel fuel, 15 L/m 2 ) was placed on the surface of the wetted soil In six months the soil from different soil layers in lysimeter was sampled Hydrocarbons contained in soil samples were extracted by tetrachlormetane The content of hydrocarbons in extracts was analyzed by gas-chromatography method As a result, there was no hydrocarbon contaminants below the soil depth of 15 cm
Example 2 (corresponds to Pattern No 2)
In a field stationary lysimeter filled by leached chernozem the upper soil layer (thickness 15 cm) was removed On the formed subsoil surface the layer (10 cm) of rubber powder (particle size of less than 2,0 mm) was placed The rubber was marked as SKMS30-ARKM15 (based on butadiene-methyl-styrene rubber) Previously removed soil was returned in the lysimeter as a covering layer Soil in lysimeter was wetted up to the field capacity The contamination of soil and analysis of hydrocarbons were carried out as in Example 1 As a result, there was no hydrocarbon contaminants below the soil depth of 15 cm
Example 3 (corresponds to Pattern No 3)
In a field stationary lysimeter filled by soddy-podzolic soil the upper soil layer (thickness 15 cm) was removed On the formed subsoil surface the layer (10 cm) of high- moor peat (size of particles less than 5,0 mm) was placed Then on its surface previously removed soil layer mixed with clay (montmoπllonite content, 90%) of Byklyansky deposit of Tatarstan republic (soil/clay ratio of 5 1 ) was placed as a covering layer Soil in lysimeter was wetted up to field capacity The contamination of soil and analysis of hydrocarbons were carried out as in Example 1. As a result, there was no hydrocarbon contaminants below the soil depth of 25 cm.