Method for improving rainfall leaching efficiency of coastal saline-alkali land by using garden waste
Technical Field
The invention belongs to the field of saline-alkali soil treatment, and particularly relates to a method for improving rainfall leaching efficiency of coastal saline-alkali soil by using garden wastes.
Background
In coastal areas in northern China, particularly at river estuaries, underground water is shallow in buried depth and high in mineralization degree, the invasion effect of seawater is obvious, large-area land is formed by river flow silt sedimentation and seabed silt hydraulic filling, the soil texture is extremely poor, the soil structure is not provided, the volume weight is large, the pores are small, the effect of soil capillary tubes is strong, and the underground water with high mineralization degree is easy to migrate to the surface soil layer under the evaporation effect, so that the formation of saline-alkali soil is caused. And the soil permeability is poor, rainfall is relatively concentrated, the total infiltration amount of the soil is small after single rainfall, and the soil surface runoff is formed and runs off after a large amount of rainfall does not participate in the leaching of saline-alkali soil, so that the separate leaching efficiency of the soil salt of the atmospheric rainfall is very low, the infiltration amount of the rainfall is far less than the evaporation amount of the soil, and the soil salt content of the saline-alkali soil is continuously increased after the rainfall is not sufficiently leached.
Along with the gradual acceleration of urbanization process and the high requirement of people to city ecology, city afforestation's area is constantly increased, and the quantity of gardens discarded object such as the trees clipping thing that produces in the vegetation process, lawn clipping thing, withered branches and fallen leaves is also more and more, and the simplest processing mode of gardens discarded object is directly burning now, and direct combustion not only causes the atmosphere pollution easily, is a waste of resources moreover.
Disclosure of Invention
In order to improve the rainfall leaching efficiency of the coastal saline-alkali land and complete the resource recycling of garden wastes, the method for improving the rainfall leaching efficiency of the coastal saline-alkali land by using the garden wastes is provided, the method can improve the rainfall leaching efficiency of the coastal saline-alkali land, enable the atmospheric rainfall infiltration amount to be equal to or larger than the soil evaporation amount, increase the content of organic matters in the saline-alkali land soil, enable the saline-alkali soil to form aggregates, have a soil structure, gradually improve the saline-alkali land, and perform resource utilization on the garden wastes.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method for improving rainfall leaching efficiency of coastal saline-alkali land by using garden wastes comprises the following steps:
(1) classifying the garden waste into substances which can be composted and substances which are not suitable for composting;
(2) composting the substances which can be composted and are obtained in the step (1);
(3) simply processing the substances which are not suitable for composting and obtained in the step (1) into a form of only one trunk, and binding the substances after shearing the substances until the length of the substances is less than 50 cm;
(4) paving the bound substances which are not suitable for composting and obtained in the step (3) into a salt isolation layer;
(5) and (3) carrying out layered blending on the compost material obtained in the step (2) and saline-alkali soil, and paving a blended soil layer from bottom to top, wherein the proportion of the compost material is increased in a gradient manner from bottom to top.
Preferably, in step (1), the substances which can be composted include, but are not limited to, petals, leaves, weeds, and substances which are not suitable for composting include, but are not limited to, branches and twigs.
The invention comprises two levels of garden waste treatment and application. The first level is to treat garden waste, including classification of garden waste, composting of garden waste and simple treatment; the second layer is used for applying the treated garden waste, and comprises a compost layered mixing and saline-alkali soil salt isolation layer. The garden waste mainly comprises two main types, namely flowers, leaves and branches, wherein the branches have extremely high lignin and cellulose content and are difficult to decompose and not easy to compost. The branch garden waste has certain strength, can be used as a filling material of a salt-separating layer after being treated, can play a role of the salt-separating layer, and can be slowly and naturally degraded within 4-6 years. The method is used for improving the soil texture of coastal saline-alkali soil after treating garden waste, improving the rainfall infiltration rate, fully leaching the saline-alkali soil by natural rainfall, enabling the natural rainfall infiltration amount to be equal to or more than the soil evaporation amount, gradually improving the saline-alkali soil under natural leaching, setting branches which are difficult to decompose in the garden waste as salt isolation layers, isolating underground water on one hand, increasing the hydraulic gradient of the soil above the salt isolation layers on the other hand, improving the leaching efficiency, and naturally degrading tree branches for a long time without causing environmental pollution.
Preferably, in the step (2), before composting, the substances which can be composted and are obtained in the step (1) are crushed to be less than 10mm and are stacked for 2-4 weeks.
The materials harmful to the earthworms, such as organic acid in the raw materials, can be eliminated after the compost is piled for 2 to 4 weeks, and the later-period compost is facilitated.
Preferably, in the step (2), the composting comprises the following steps: mixing compostable substances with cow dung according to a dry mass ratio of 95-90:5-10, adding 60-80 earthworms into each 1kg of raw materials for composting, wherein the humidity of the materials is kept at 55% -65% and the temperature is kept at 16-22 ℃ in the composting process; continuously taking off compost products in the composting process, and adding new substances capable of composting and cow dung according to the dry mass ratio of 95-90: 5-10.
The cow dung can increase the growth speed of earthworms and improve the processing capacity. The coastal saline-alkali soil is formed by river sediment sedimentation and seabed sediment hydraulic filling, so that the soil particle size is small, and the number of gap channels in the soil formed by small particle sizes is very small, so that rainwater is difficult to infiltrate, the rainwater cannot infiltrate during rainfall, the porosity of the earthworm compost products is high, the gaps of the whole soil are improved after the earthworm compost products are mixed, and an infiltration channel is provided for rainwater infiltration. The earthworm compost product is not a substance for desalting and alkalizing, soil salinization removal or rainfall elution by atmosphere, and the earthworm compost product provides a channel for rainfall elution just like opening the conception and governor vessels of soil. In addition, the earthworm compost product has high organic matter content, the organic matter can agglomerate tiny soil particles to form aggregates, and the aggregates with large volume can form pores, so that the soil porosity is improved, and the rainwater infiltration rate is increased.
Preferably, in step (3), the diameter of the bundled non-compostable material is between 6 and 10 cm.
The bundled substances which are not suitable for composting are made into salt isolation layers, the minimum thickness of the salt isolation layers is 10cm, so the diameter of the salt isolation layers cannot be larger than 10cm, the diameter of the salt isolation layers is not too small, a water passing channel cannot be formed well if the diameter of the salt isolation layers is too small, and the salt isolation layers are easy to compact after being pressed by the upper soil layer if the diameter of the salt isolation layers is too small, so the water passing capacity is reduced.
Preferably, in step (4), the salt-separating layer comprises the following steps: and (3) paving a layer of water-permeable non-woven fabric at the position with the depth of 110-120cm of the soil layer, paving the bound substances which are not suitable for composting obtained in the step (3) on the water-permeable non-woven fabric, wherein the paving thickness is 10-20cm, leveling the working surface after paving, and then paving a layer of water-permeable non-woven fabric on the upper part.
The water-permeable non-woven fabric is high-strength water-permeable non-woven fabric, and the purchasing manufacturer is limited company of Texas moist geotechnical materials.
The thickness of the salt isolation layer is easily 10-20 cm. The salt separation layer is of a large-pore structure, and the larger the thickness is, the larger the surface sedimentation risk is. If the salt-separating layer is arranged to be too small, the infiltration water is easy to fill the salt-separating layer, so that the effect of the salt-separating layer is lost.
Preferably, in the step (5), 4-8 layers of soil layers are laid, the thickness of each soil layer is the same or different, and the difference of the proportion of the compost materials of the adjacent soil layers is 5% -10%.
Preferably, in the step (5), when the soil layer is laid, 600cm is filled every 300-2The underground water level monitoring column is arranged at the central position, the change conditions of the underground water level and the mineralization degree are sampled and monitored through the underground water level monitoring column from time to time, and underground water pumping and drainage are performed through the underground water level monitoring column after the underground water level rises to the top elevation of the salt separation layer.
Preferably, the underground water level monitoring column comprises a hollow column body with an upper end opening and a bottom sealed, a seepage hole section is arranged at the lower part of the hollow column body, a plurality of seepage holes are uniformly distributed in the seepage hole section, the underground water level monitoring column is buried in a specified position in the layered laying process, and the depth of the seepage hole section of the underground water level monitoring column is ensured to coincide with the depth of the salt isolation layer in the burying process.
The underground water level monitoring column is provided with a seepage hole section and other parts are non-seepage hole sections. The purpose of ground water level monitoring post is to survey ground water level, the infiltration hole segment length is the same with salt-separating layer thickness, the material of laying of salt-separating layer is branch strip class gardens discarded object, have stronger water capacity of crossing, after the groundwater level rises to salt-separating layer degree of depth, moisture can get into ground water level monitoring post through the infiltration hole fast, so that discover, later usable suction pump will rise to the groundwater of salt-separating layer bottom height through the infiltration hole and take out, in order to reduce groundwater, make salt-separating layer upper soil not receive the influence of groundwater, avoid appearing the salinization phenomenon. The length of the non-seepage hole section is the same as the thickness of the soil above the salt isolation layer, the non-seepage hole section can prevent a large amount of water from leaking from the underground water level monitoring column in the rainfall infiltration process, and the soil on the upper layer of the salt isolation layer is prevented from being polluted by the underground water when the underground water is pumped out.
Compared with the prior art, the method for improving the rainfall and showering efficiency of the coastal saline-alkali land by using the garden waste has the following beneficial effects:
1. the garden waste after composting has the advantages of high porosity, strong water retention, high organic matter content and the like, and can be used as a saline-alkali soil admixture for improving the soil structure of saline-alkali soil and improving the leaching effect. The integral porosity of the soil is improved by blending garden waste earthworm compost products, the infiltration rate of the saline-alkali soil is increased, and the rainfall leaching efficiency is improved.
2. The porosity is gradually decreased from the surface soil layer to the bottom soil layer by layered mixing, the step-shaped infiltration rate is formed, the infiltration rate of the upper soil is higher than that of the lower soil due to the large mixing amount of compost products, water can quickly infiltrate when the water passes through the upper soil during rainfall, the infiltration rate of the lower soil is lower than that of the upper soil, part of water is partially throttled into the upper soil, and the fact that the salt content of the upper soil can be better infiltrated after being dissolved by the water is guaranteed. When the soil water salt evaporates, the soil water salt migrates to the surface layer of the soil under the capillary action, the porosity of the soil increases from the bottom layer of the soil to the surface layer by layer, the capillary action can be weakened, the migration of the soil water salt to the surface layer of the soil is inhibited, and the surface soil salt accumulation is slowed down.
3. According to the invention, the branches which have certain strength and are difficult to carry out earthworm composting are arranged as salt-isolating layers, and underground water is isolated by combining the underground water level monitoring columns, so that the underground water is prevented from rising to the mixed soil layer. The salt separation layer is communicated with the atmosphere by utilizing the underground water level monitoring column, so that a free drainage boundary is formed on the bottom surface of the soil at the upper part of the salt separation layer, the air permeability of the soil can be increased, the hydraulic gradient in the leaching process is increased, and the leaching efficiency is improved.
4. The invention fully applies the garden waste to the improvement of the saline-alkali soil, and greatly improves the utilization value of the garden waste.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a flowchart of a method of example 1 of the present invention;
FIG. 2 is a schematic diagram showing the use of example 1 of the present invention;
FIG. 3 is a schematic structural view of a ground water level monitoring column according to embodiment 1 of the present invention;
FIG. 4 is a graph showing a comparison of the salt rejection of soil in examples of the present invention and comparative examples.
Description of reference numerals:
1. mixing the soil layer I; 2. mixing the soil layer II; 3. mixing a soil layer III; 4. mixing the soil layer four; 5. mixing the soil layer five; 6. a salt-separating layer; 7. a high-strength water-permeable nonwoven fabric; 8. a ground water level monitoring column; 9. a non-porous section; 10. and (5) a porous section.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
The present invention will be described in detail with reference to the following examples and accompanying drawings.
As shown in fig. 1-3, a method for improving the rainfall leaching efficiency of coastal saline-alkali land by using garden wastes mainly comprises the steps of treatment and application of the garden wastes. The treatment of the garden waste mainly comprises classification of the garden waste, earthworm composting and simple treatment (cutting and binding of branch trimmings). The application of the garden waste mainly comprises the steps of mixing earthworm compost in a layering manner and binding the earthworm compost with a branch salt isolation layer.
Example 1
The Tianjin south harbor industrial area is formed by land reclamation by sea mud, the initial soil has high salt content, the underground water level of the area is shallow, the soil has poor water permeability, the infiltration of rainfall is difficult, and the evaporation action strongly ensures that salt is continuously accumulated to the earth surface. The method for improving the rainfall leaching efficiency of the coastal saline-alkali soil by using the garden wastes can change the original salt accumulation condition, the regional saline-alkali soil is in the desalting condition under the rainfall action by improving the natural leaching efficiency, the bare heavy saline-alkali soil is selected for testing, the initial salt contents of 0-20, 20-40, 40-60, 60-80 and 80-100cm soil layers of the test site are respectively 33.5, 36, 35, 33.4 and 27.6g/kg, and the implementation comprises the following steps:
(1) classifying garden wastes: the garden waste is classified into substances which can be composted by earthworms such as petals, leaves and weeds, and substances which are not suitable for composting such as branches and branches.
(2) Garden waste earthworm composting: garden wastes such as petals, leaves, weeds and the like are crushed to be less than 10mm and stacked for 2 weeks, substances harmful to earthworms such as organic acid and the like in the raw materials are eliminated, then the raw materials are mixed with cow dung according to the dry mass ratio of 95:5, 60-80 Eiseniafetida (Eiseniafetida) are added into each 1kg of the raw materials for composting, the humidity of the materials is kept between 55% and 65% in the composting process, and the temperature is kept between 16 ℃ and 22 ℃. Continuously taking away the compost product in the composting process and adding new raw materials.
(3) Simple treatment of branch wastes: processing the branches into a form of only one trunk, bundling the branches, and binding the branches to be between 6 and 10cm in diameter.
(4) The salt isolation layer is arranged: and laying a high-strength water-permeable non-woven fabric layer at the position of 120cm of the depth of the soil layer, flatly laying the bundled branches on the non-woven fabric layer with the laying thickness of 20cm, leveling the working surface after laying is finished, and then laying a high-strength water-permeable non-woven fabric layer on the upper part.
(5) Layering and blending earthworm compost products: the method comprises the steps of carrying out layered blending on compost materials and saline-alkali soil, carrying out soil layer laying from bottom to top, firstly carrying out soil layer laying with the number 5, carrying out blending and mixing on soil compost products and the saline-alkali soil according to the mass ratio of 5:95, then laying with the thickness of 20cm, then carrying out soil layer laying with the number 4, carrying out blending and mixing on the soil compost products and the saline-alkali soil according to the mass ratio of 10:90, then laying with the thickness of 20cm, then carrying out soil layer laying with the number 3, carrying out blending and mixing on the soil compost products and the saline-alkali soil according to the mass ratio of 15:85, then laying with the thickness of 20cm, then carrying out soil layer laying with the number 2, carrying out blending and mixing on the soil compost products and the saline-alkali soil according to the mass ratio of 20:80, laying with the thickness of 20cm, finally carrying out topsoil layer laying with the number 1, carrying out blending and mixing and laying with the saline-alkali soil according to the mass ratio of 25:75, the laying thickness is 20 cm.
(6) The underground water level monitoring column is arranged: every 400cm2The underground water level monitoring column is arranged at the central position, is buried at a designated position in the layered laying process, and ensures the depth of the seepage hole section of the underground water level monitoring column and salt separation in the burying processThe layer depths coincide. The change conditions of the groundwater level and the mineralization degree are monitored by frequently sampling through the groundwater level monitoring column, and groundwater pumping and drainage are carried out when necessary.
(7) The technical implementation was performed by taking soil samples after one year of rainfall, the soil sampling was performed in layers, three repeated samplings were randomly performed on the test plots, the average value was taken as the final result, and the final result is shown in table 1 below.
Table 1 example 1 final results of soil sampling
Depth of soil layer (cm)
|
0-20
|
20-40
|
40-60
|
60-80
|
80-100
|
Salt content (g/kg)
|
22.2
|
24.5
|
26.7
|
28.2
|
23.1
|
Salt rejection (%)
|
33.73
|
31.94
|
23.71
|
15.56
|
16.30 |
Comparative example 1
Comparative example 1 was installed at 3m north of example 1, and the natural soil leaching state was maintained without adding the garden waste earthworm compost and without installing the garden waste salt barrier. Soil sampling was performed after one year of rainfall, and the sampling results are shown in table 2 below.
Table 2 final results of soil sampling of comparative example 1
Depth of soil layer (cm)
|
0-20
|
20-40
|
40-60
|
60-80
|
80-100
|
Salt content (g/kg)
|
35.7
|
37.5
|
36.6
|
34.2
|
28.5
|
Salt rejection (%)
|
-6.56
|
-4.16
|
-4.57
|
-2.39
|
-3.26 |
Comparative example 2
Comparative example 2 was arranged at 3m south-facing direction in example 1, and the implementation included the following steps:
(1) classifying garden wastes: the garden waste is classified into substances which can be composted by earthworms such as petals, leaves and weeds, and substances which are not suitable for composting such as branches and branches.
(2) Garden waste earthworm composting: crushing garden wastes such as petals, leaves, weeds and the like to pieces with the diameter of less than 10mm, stacking for 2 weeks, eliminating substances harmful to earthworms such as organic acid and the like in the raw materials, mixing the materials with cow dung according to the dry mass ratio of 95:5, adding 60-80 earthworms into each 1kg of the raw materials for composting, and keeping the humidity of the materials at 55-65% and the temperature at 16-22 ℃ in the composting process. Continuously taking away the compost product in the composting process and adding new raw materials.
(3) Simple treatment of branch wastes: processing the branches into a form of only one trunk, and bundling the branches, wherein the bundling diameter is 6-10 cm.
(4) The salt isolation layer is arranged: and laying a high-strength water-permeable non-woven fabric layer at the position of 120cm of the depth of the soil layer, flatly laying the bundled branches on the non-woven fabric layer with the laying thickness of 20cm, leveling the working surface after laying is finished, and then laying a high-strength water-permeable non-woven fabric layer on the upper part.
(5) Layering and blending earthworm compost products: and (3) blending the compost material with saline-alkali soil, and paving the soil compost product and the saline-alkali soil in a mixed manner according to the mass ratio of 15:85, wherein the paving thickness is 100 cm.
(6) The underground water level monitoring column is arranged: every 400cm2The underground water level monitoring column is arranged at the center, and is buried at a designated position in the layered laying process, and the depth of a permeable hole section of the underground water level monitoring column is ensured to coincide with the depth of a salt isolation layer in the burying process. Through the groundThe change conditions of the groundwater level and the mineralization degree are sampled and monitored frequently when the water level monitoring column is placed, and groundwater pumping and drainage are carried out when necessary.
(7) The technical implementation was performed by taking soil samples after one year of rainfall, the soil sampling was performed in layers, three repeated samplings were randomly performed on the test plots, and the average value was taken as the final result, which is shown in table 3 below.
Table 3 final results of soil sampling of comparative example 2
The examples and comparative examples are analyzed:
and (3) according to the soil sampling and testing result, a comparison graph of the soil desalination rate of the example 1, the comparative example 1 and the comparative example 2 after natural rainfall for one year is made, and the soil desalination effect of the example 1, the comparative example 1 and the comparative example 2 is analyzed. From fig. 4, it can be seen that the desalination phenomenon occurs in the soil washed by the natural rainfall in one year in the example 1 and the comparative example 2, but the soil salt accumulation phenomenon occurs in the comparative example 1, which shows that the saline-alkali soil of the coastal region can be converted into desalination from salt accumulation by the soil mixed with the garden waste and the salt separation layer. The soil desalination rates of soil layers of 10-20cm, 20-40 cm and 40-60cm in example 1 are higher than those of comparative example 2, 60-80 cm and 80-100cm in soil layer are slightly lower than those of comparative example 2, the soil desalination effect of the overall comparative example 1 is better than that of the comparative example 2, and the fact that the layered mixing of the garden waste earthworm compost products is better than that of the overall uniform mixing is demonstrated.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.