CN103858552B - Build method and the application thereof of topsoil in coarse sand earth's surface with heavy metal polluted bed mud - Google Patents

Abstract

The invention discloses a method for constructing plow layer soil on a coarse sand surface with heavy metal polluted bottom mud, which comprises the following steps: 1) loosening the coarse sand surface to be treated and leveling the ground; 2) spreading the heavy metal polluted bottom mud on the ground On the surface of coarse sand; 3) Sprinkle the stabilizer on the heavy metal-contaminated sediment; 4) The first rotary tillage; 5) After 15 days of alternating dry and wet treatment, 7 days of exposure to the sun, the second rotary tillage, the direction of the rotary tillage and the The second time is the opposite; after the rotary tillage, the mass moisture content of the mixture of sediment, coarse sand and stabilizer is naturally reduced to 25-30%, and the third rotary tillage is performed, and the direction of the rotary tillage is perpendicular to the second; 6) The third After the first rotary tillage, one crop of leguminous green manure was planted, and the green manure was returned to the field after the fourth rotary tillage, and the plow layer soil was obtained after 2 months. The soil heavy metal stabilization effect of the plow layer obtained by the method is obvious, and the heavy metal content of the planted vegetable crops meets the national standard.

Description

Method and Application of Constructing Plow Layer Soil on Coarse Sand Surface Using Heavy Metal Contaminated Sediment

technical field

The invention belongs to the field of land improvement engineering, and in particular relates to a method for constructing plow layer soil on a coarse sand surface with heavy metal polluted bottom mud and its application.

Background technique

Land remediation is an activity to improve the efficiency of land use by renovating land that is inefficiently used, irrationally used, unused, and damaged by production and construction activities and natural disasters; important means of productivity. Among them, the requirements for the cultivated layer soil in the land improvement project are particularly high, that is, the quality of the cultivated land after the improvement is at least one level higher than the quality of the cultivated land before the improvement. The specific indicators are that the thickness of the remediation soil layer is more than 15-20cm, the nutrients are complete, the organic matter is rich, the aggregate structure is good, the soil environment is good, and it is suitable for long-term cultivation. In the current land consolidation project, the sources of the cultivated layer soil mainly include the following modes: (1) backfilling of stripped topsoil; (2) backfilling of alien soil in development and construction projects; (3) applying soil to the existing cultivated layer soil Fertilizer improvement and other three main modes of plow layer soil sources, but the above modes are based on the fact that the areas with rich soil resources in the renovation project can be realized, and some modes cannot be realized due to the high economic and technical costs due to the distance of soil transport .

Coarse sandy land is a land degraded in which silt and clay particles in the soil structure are gradually lost under the conditions of artificial unreasonable planting management and natural rainfall erosion for a long time, and the land appears sandy. Finally, the plow layer soil of this kind of land is destroyed, the soil water and water retention is poor, the soil fertility is poor, and normal agricultural planting and production activities cannot be carried out. In the worst case, land resources may be completely lost. It is very important to solve the problem of plow layer soil in the land consolidation project in the coarse sand area, and the lack of soil is also the main economic and technical factor that limits the rapid progress of the land consolidation project in the coarse sand area.

Sediment is an important part of the water body, mainly composed of clay minerals, organic matter, and active metal oxides. This natural particle has a huge specific surface area and plays an important role in the water environment. It is a source of various pollution in the water. source and sink of matter. Sediment dredging is an effective measure to improve lake water quality, and the disposal of dredged sediment needs to meet the requirements of safety, rationality and economy at the same time. The resource utilization of sediment has attracted more and more people's attention. In the way of resource utilization of dredged sediment with light and moderate pollution, land use has the advantages of large amount, simple technology and good economy. The dredged sediment The utilization of agricultural resources can not only turn waste into wealth, but also reduce environmental pollution.

Since lake sediments are rich in organic matter, nitrogen, phosphorus and other nutrient elements, their resource utilization has become a research hotspot today, but excessive heavy metal elements have become a key factor restricting their agricultural resource utilization. Many scholars have carried out extensive research on how to reduce and reduce the toxic effect of heavy metals in dredged sediment, but the system, economy and practicability are not up to the requirements. Therefore, it is of great significance to study how to make rational resource utilization of lake sediment and avoid pollution of heavy metals to the soil-plant system. In addition, due to the high content of clay minerals in the bottom mud, the dehydrated bottom mud is easy to form hard lumps, and its physical structure is not suitable for plant growth. Therefore, while solving heavy metal pollution, it is also necessary to adjust and improve the physical and chemical properties of the soil.

The research on resource utilization of river bottom sediment can not only solve the problem of bottom mud outlet, but also produce certain economic benefits. Sediment resource utilization technologies mainly include: brick making, ceramsite making, adsorbent, land utilization, etc. Many studies have shown that after land use of lake sediment, the total aggregate structure and water-stable aggregate structure increase; at the same time, the soil water content, field water holding capacity, soil porosity and capillary porosity also increase. After the application of sediment with high organic matter content and high decomposing degree, the soil bulk density can be reduced, the volume of soil solid phase will gradually decrease, and the volume of liquid phase and gas phase will gradually increase; but the sediment with high content of clay minerals and low decomposing degree will May increase soil bulk density and cause compaction. Therefore, the application of bottom mud can significantly improve various physical and chemical properties of the soil, thereby improving the ability of soil water retention, fertilizer retention, water supply, and fertilizer supply. The bottom mud and the bottom mud granular fertilizer prepared by it contain a certain amount of nutrients, which is higher than that of pig manure, and has a certain fertilizer effect. This shows that the soil nutrient content level can be increased after the land use of the bottom mud. Land use of bottom mud can not only bring in a large amount of organic matter and mineral nutrients to provide nutrients for microorganisms in the soil, but also the bottom mud itself is rich in microorganisms, which increases the number of soil microorganisms. At the same time, the application of municipal sludge can change the population structure of soil microorganisms, increase the proportion of soil nitrifying bacteria, increase enzyme activity, and improve the basic fertility of soil and the content of soil humus. The bottom mud contains a lot of nitrogen and phosphorus, as well as trace elements such as potassium, calcium, iron, sulfur, magnesium, zinc, copper, manganese, boron, molybdenum, etc., which can slowly supply the nutrients needed for plant growth.

At the same time, the risk of land use of sediment is mainly heavy metal pollution. There are many kinds of heavy metals in sediment, mainly including Cu, Pb, Zn, Ni, Cr, Hg, Cd, etc., which are important factors that limit their large-scale land use. At present, there are many studies on the pollution of heavy metals in soil, mainly focusing on the changes of heavy metals in the soil plow layer after the use of bottom mud, the accumulation of heavy metals in various parts of crops, their existing forms and their impact. Reasonable agricultural use of sediment will not cause heavy metal pollution to soil and agricultural products, but long-term application will increase the content of heavy metals in soil. Therefore, long-term application of lake sediment and its fertilizers requires necessary monitoring. The bottom mud contains a variety of organic pollutants, which can reach a higher level in the organism through bioaccumulation, resulting in strong toxic effects, and may also endanger human health through the food chain.

In addition, the sediment texture after natural dehydration is very compact, with a bulk density as high as 1.89g/cm ³ and a porosity of only 23.8%. The soil porosity range suitable for good plant growth is generally 55% to 65%. Soils with low porosity are very compact and hard, which affects the growth and respiration of plant roots. Therefore, if the texture of the dredged sediment is not adjusted, it cannot become a medium for plant growth, which will affect its large-scale use in land.

Contents of the invention

In view of the deficiencies of the existing soil remediation technology in the coarse sand area and the deficiencies of the sediment agricultural resource utilization technology, the purpose of the present invention is to provide a method for constructing plow layer soil on the coarse sand surface with the heavy metal contaminated sediment.

A kind of method that the present invention provides with heavy metal pollution bottom mud builds plow layer soil on coarse sand surface, comprises the steps:

1) Loosen the surface of coarse sand to be treated and level the ground;

2) Spread the heavy metal contaminated sediment on the coarse sand surface described in step 1);

3) Sprinkle the stabilizer on the heavy metal-contaminated bottom mud described in step 2);

4) Carry out the first rotary tillage on the ground where step 3) has been completed;

5) Alternate dry and wet treatment for 15 days, expose to the sun for 7 days, and perform the second rotary tillage, the direction of which is opposite to the second; after rotary tillage, the mass moisture content of the mixture of sediment, coarse sand, and stabilizer is naturally dehydrated to 25-30%, carry out the third rotary tillage, the direction of rotary tillage is perpendicular to the second;

6) After the third rotary tillage, plant one crop of leguminous green manure. When the plant height of the green manure reaches 30-35cm, carry out the fourth rotary tillage and return the green manure to the field. After 2 months, the plow layer soil is obtained.

Wherein, the standard for leveling the ground in step 1) is that the slope ratio is ≤3:1000.

Wherein, the heavy metal-polluted sediment in step 2) is heavy-metal-polluted river sediment and/or heavy-metal-polluted lake sediment.

Wherein, in step 2), the thickness of the heavy metal-contaminated sediment is 24 cm.

Wherein, the stabilizer described in step 3) is a heavy metal treatment stabilizer, preferably a stabilizer comprising the following components in parts by weight: 5 parts of calcium magnesium phosphate fertilizer, 5 parts of calcium oxide, and 1-3 parts of lightly burned dolomite.

Wherein, the amount of the stabilizer described in step 3) is: 0.8-1.2 parts by weight of the stabilizer per 100 parts by weight of the bottom sludge, preferably 1 part by weight of the stabilizer per 100 parts by weight of the bottom sludge.

Wherein, step 5) described alternating dry and wet treatment for 15 days, spraying water once to wet the bottom mud and then drying for 5 days, repeated 3 times for a total of 15 days.

Wherein, the depth of the first rotary tillage is 24cm; the depth of the second rotary tillage is 27cm; the depth of the third rotary tillage is 30cm; the depth of the fourth rotary tillage is 30cm; All are in the form of spiral forward rotary tillage.

Wherein, the leguminous green manure is preferably one or more of stylo, lentil, and quince.

The invention also provides the application of the method for constructing plow layer soil on the coarse sand surface with the heavy metal polluted bottom mud to the treatment of the heavy metal pollution of the bottom mud.

The invention also provides the application of the tillage layer soil obtained by the method of constructing the tillage layer soil from the heavy metal polluted sediment on the coarse sand surface in crop planting.

Compared with the prior art, the present invention has the following advantages and effects:

The present invention takes heavy metal compound polluted river bottom mud as the treatment object, adopts calcium magnesium phosphate fertilizer, calcium oxide, light burnt dolomite as heavy metal stabilizer, and uses coarse sand and returning green manure as physical and chemical property improver, so that the heavy metal in the treated bottom mud is stabilized. The effect is good, the leachable components are reduced, and it is difficult for crops to absorb. At the same time, the effect of improving physical and chemical properties is obvious, and it has a good effect of increasing production. It provides a way out for the resource disposal of polluted river sediment, and proposes a new method for the construction of plow layer soil in coarse sandy land improvement projects. Complement and organically combine with each other.

The depth of the first rotary tillage of the present invention is 24cm to ensure that the bottom mud and the stabilizer are initially mixed and contacted; 15 days of alternating dry and wet treatment, and the second rotary tillage after 7 days of exposure to the sun, the depth is 27cm, and the direction of rotary tillage is the same as that of the first time. Reverse, ensure that the sediment, stabilizer and some coarse sand are fully mixed; when the water content of the mixture of sediment, coarse sand and stabilizer is reduced to 25-30%, perform the third rotary tillage, the direction of rotary tillage is the same as that of the second The rotary tillage is vertical, with a depth of 30cm, to ensure that the bottom mud and coarse sand are mixed according to the design ratio (volume 4:1), so that the soil thickness of the constructed plow layer meets the requirements of land consolidation. The present invention realizes the amount of bottom mud and coarse sand and the mixing ratio of bottom mud and coarse sand through the laying thickness of the bottom mud and the depth of rotary plowing, and has practical production value and significance. After the first three rotary tillage soil settlements are stabilized, the soil thickness of the tillage layer is ≥ 26cm.

The diameter of the soil bottom mud particles of the cultivated layer obtained after the treatment by the method of the invention is less than or equal to 3 cm, and the bottom mud and coarse sand are evenly mixed.

From the perspective of heavy metal storage form and crop absorption, the inventor has proved that the heavy metals in the bottom mud after treatment have a good stabilizing effect through heavy metal leaching tests, vegetable planting field tests, dry crop field tests, etc. Secondary pollution and food safety issues in the utilization of agricultural resources. The inventor has proved from the aspects of soil pH adjustment test, soil fertility improvement and yield increase test, soil mechanical composition adjustment test and other aspects that the bottom mud construction plow layer soil can improve the soil quality effect as a whole, which is an important role for the bottom mud in agriculture. It has laid a good foundation for further utilization in resource utilization.

Through actual tests, the bottom sludge treated by the method of the present invention has obvious stabilization effect of heavy metals Cr, Cu, Zn and Cd, and the content of heavy metals in the planted water spinach and green soybeans is lower than that of the latest "GB2762-2012 Food Safety Standard". The relevant limits specified in the National Standard - Limits of Pollutants in Food, and are lower than the relevant limits specified in the "GB18406.1-2001 Safety Requirements for the Safety and Quality of Agricultural Products and Pollution-free Vegetables".

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Embodiment 1 The method of constructing plow layer soil on the coarse sand surface with heavy metal polluted bottom mud

In November 2012, in Xiasi Village, Xinpo Town, Longhua District, Haikou City, Hainan Province, the surface of the coarse sandy land to be improved was loose and flat, and the standard for leveling the ground was a slope ratio ≤ 3:1000.

The dredged bottom mud from a river pond in Xinpo Town, Haikou City was naturally dehydrated and paved, and then dried and dehydrated naturally, and evenly spread on the coarse sand. The thickness of the bottom mud laying was 24cm.

Spread stabilizer evenly on the above-mentioned heavy metal contaminated bottom mud, said stabilizer includes calcium magnesium phosphate fertilizer, calcium oxide, lightly burned dolomite, the mass ratio of the three corresponding is 5:5:2, and every 100 parts by weight of bottom mud is used 1 part by weight of stabilizer.

On the ground sprinkled with stabilizer, use a rotary tiller (Dongfanghong 1GQN-125 rotary tiller, China YTO Group Co., Ltd., the same machine used for subsequent rotary tillage) to perform the first rotary tillage; dry and wet treatment for 15 days , exposed to the sun for 7 days, perform the second rotary tillage, and the direction of the rotary tillage is opposite to the second; after the rotary tillage, the water content of the mixture of sediment, coarse sand, and stabilizer will naturally decrease to 25-30%, and perform the third rotary tillage. Rotary tillage, the direction of rotary tillage is perpendicular to the second time; after the third time, plant leguminous green manure for 1 stubble, and plant the green manure as stylophyllum. After the plant height reaches 30cm, carry out the fourth time of rotary tillage and return the green manure to the field, 2 After one month, the plow layer soil was obtained. The dry-wet treatment was carried out alternately for 15 days, which was to spray water once to make the bottom mud wet and then dry for 5 days, which was repeated 3 times for a total of 15 days. The depth of the first rotary tillage is 24cm; the depth of the second rotary tillage is 27cm; the depth of the third rotary tillage is 30cm; the depth of the fourth rotary tillage is 30cm; Rotary tillage advances in a spiral shape.

Two months after the fourth rotary tillage, use EPA's Method-1311 Toxicity Characteristic Leaching Procedure (TCLP) for measurement, and set 0.3% lime + 0.3% calcium magnesium phosphate fertilizer as a stabilizer for comparison (100 parts by weight of sediment plus 0.3 parts by weight lime and 0.3 parts by weight calcium magnesium phosphate fertilizer). The leaching concentration of TCLP in the bottom mud treated by the method is obviously reduced. Among them, the leaching concentration of Cr element decreased by 46.91% compared with the unstabilized group, and decreased by 32.56% compared with the lime calcium magnesium phosphate fertilizer treatment group; the leaching concentration of Cu element decreased by 72.22% compared with the unstabilized group, and compared with the lime calcium magnesium phosphate fertilizer treatment group group decreased by 45.07%; the leaching concentration of Zn element decreased by 26.14% compared with the unstabilized group, and decreased by 24.07% compared with the lime calcium magnesium phosphate fertilizer treatment group; the leached concentration of Cd element decreased by 40.55% compared with the unstabilized group, compared with the lime Calcium magnesium phosphate fertilizer treatment group decreased by 30.41%; the concentrations of Pb, As, and Hg elements in the leachate were all lower than the detection limit.

The results are shown in Table 1. The leaching of heavy metals is reduced and the stabilization effect is obvious.

Table 1 Concentration of heavy metals in sediment TCLP leachate before and after stabilization (unit: μg/L)

handle name Cr Cu Zn Cd Pb As Hg Not stable 4.37 11.23 146.68 5.08 <1.00 <0.15 <0.15 Lime + Calcium Magnesium Phosphate Fertilizer 3.44 5.68 142.69 4.34 <1.00 <0.15 <0.15 Stabilizer of the present invention 2.32 3.12 108.34 3.02 <1.00 <0.15 <0.15

Embodiment 2 The application of the plowing layer soil obtained by the present invention on crop planting

On the plow layer soil obtained by the method of the present invention from the bottom mud in Example 1, water spinach (produced respectively from Thailand's Gundam Seed Co., Ltd. and Beijing Golden Land Agricultural Technology Research Institute) and dry crop edamame were planted according to conventional methods. At the same time, 0.3% lime + 0.3% calcium magnesium phosphate fertilizer was used as a stabilizer to stabilize the test plow layer soil, and the plow layer soil covered with unstabilized bottom mud was used as a comparison. Physiological indicators and growth indicators are recorded during crop growth, yield is recorded when harvested, and heavy metal content detection is carried out on vegetables and soybeans.

As a result, the physiological indicators and growth indicators of vegetables planted in the bottom mud after treatment are better than those grown on 0.3% lime + 0.3% calcium magnesium phosphate fertilizer as stabilizer and untreated bottom mud, and the yield is also significantly higher than that of 0.3% lime + 0.3% calcium magnesium phosphate fertilizer as stabilizer soil and untreated bottom mud soil. Table 2 shows the heavy metal content of vegetables grown on the sediment before and after treatment.

Table 2 Heavy metal content in sediment planted vegetables before and after stabilization (unit: mg/kg)

After stabilization treatment, the content of heavy metals in water spinach decreased significantly. The Cr element content decreased by 43.96% compared with the unstabilized group, and decreased by 22.65% compared with the lime calcium magnesium phosphate fertilizer treatment group; the Cu element content decreased by 39.14% compared with the unstabilized group, and decreased by 23.03% compared with the lime calcium magnesium phosphate fertilizer treatment group; Cd element content has reduced 82.59% than unstabilized group, has reduced 34.52% with respect to lime calcium magnesium phosphate fertilizer treatment group; lower than the detection limit of the method; the contents of As elements were all lower than the detection limit of the method.

After stabilization treatment, the heavy metals, Pb and As elements in edamame (edible part) were lower than the detection limit of the method; 17.04% smaller; the Cu element content decreased by 50.14% compared to the unstabilized group, and decreased by 20.21% compared to the lime calcium magnesium phosphate fertilizer treatment group; the Cd element content decreased by 63.22% compared to the unstabilized group, compared to the lime calcium magnesium phosphate fertilizer treatment group increased by 48.39%.

Example 3 The application of the plow layer soil pH adjustment constructed by the present invention

In Example 1, the bottom mud was stabilized according to the present invention to construct the plow layer soil, and water spinach (produced by Thailand Gundam Seed Co., Ltd.) was planted according to the conventional method. At the same time, 0.3% lime + 0.3% calcium magnesium phosphate fertilizer was used as a stabilizer to stabilize the plow layer soil (but no green manure treatment was planted in this treatment), and the local natural farmland soil was used as a comparison. The adjustment effects of soil mechanical composition (Table 3) and fertility conditions (Table 4) were monitored after planting crops in different soil treatments.

Table 3 Adjustment effect of different stabilization treatments on soil mechanical composition of plow layer (unit: %)

As can be seen from the adjustment data of the field test soil mechanical composition in Table 3, the application of the inventive technology can make the mechanical composition of the constructed plow layer soil have a greater adjustment effect, so that the constructed soil particle structure has a very obvious improvement effect and improve Improve the effect of soil water retention and fertilizer application. Taking natural farmland soil as a comparison, this technology can increase the clay content by nearly 4%, the silt content can also be increased compared with the control, and the sand content can be reduced, which has a greater impact on the soil structure, especially through the biological improvement measures of green manure , which can make the constructed soil less prone to compaction.

Table 4 Regulating effects of different stabilization treatments on soil fertility in plow layer (unit: %)

As can be seen from the field soil fertility monitoring test data of table 4, the soil organic matter after the present invention handles has larger increase than the soil of natural farmland and other treatments, and the range of increase is more than 28%; The treatment increased 4.66 times and 1.04 times respectively compared with the natural farmland and the lime calcium magnesium phosphate fertilizer group. The inventive technology has a remarkable effect on fertility regulation, which is reflected in better production and application value.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method of constructing plow layer soil on the coarse sand surface with heavy metal polluted bottom mud, comprising the steps: 1) Loosen the coarse sand surface to be treated and level the ground; 2) spreading the heavy metal contaminated bottom mud on the coarse sand surface described in step 1); 3) Sprinkle the stabilizer on the heavy metal-contaminated bottom mud described in step 2); 4) Carry out rotary tillage for the first time on the ground of completing step 3); 5) Alternate dry and wet treatment for 15 days, expose to the sun for 7 days, perform the second rotary tillage, the direction of the rotary tillage is opposite to the first time; after the rotary tillage, the mass moisture content of the mixture of sediment, coarse sand and stabilizer is naturally dehydrated to 25-30%, carry out the third rotary tillage, the direction of rotary tillage is perpendicular to the second; 6) After the third rotary tillage, plant one crop of leguminous green manure. When the plant height of the green manure reaches 30-35cm, carry out the fourth rotary tillage and return the green manure to the field. After 2 months, the cultivated layer soil is obtained. 2. The method for constructing plow layer soil on the coarse sand surface with heavy metal contaminated bottom mud according to claim 1, characterized in that, the standard for leveling the ground in step 1) is a slope ratio≤3:1000. 3. the method for constructing plow layer soil on coarse sand surface with heavy metal polluted bottom mud according to claim 1, it is characterized in that, the heavy metal polluted bottom mud described in step 2) is heavy metal polluted river course bottom mud and/or heavy metal pollution Lake bottom mud; the thickness of the heavy metal-polluted bottom mud is 24cm. 4. the method for constructing plow layer soil on coarse sand surface with heavy metal polluted bottom mud according to claim 1, it is characterized in that, the stabilizer described in step 3) is heavy metal treatment stabilizer. 5. the method for constructing plow layer soil on coarse sand surface with heavy metal pollution bottom mud according to claim 4, it is characterized in that, step 3) described stabilizer comprises following composition by weight: 5 parts of calcium magnesium phosphate fertilizers, oxidized 5 parts of calcium, 1 to 3 parts of lightly burned dolomite. 6. the method for constructing plow layer soil on coarse sand surface with heavy metal polluted bottom mud according to claim 5, it is characterized in that, the usage amount of the stabilizer described in step 3) is: every 100 parts by weight of bottom mud uses stabilizer 1 part by weight. 7. according to claim 1 with heavy metal pollution bottom mud in the method for constructing plow layer soil on the coarse sand surface, it is characterized in that, step 5) described wet and dry alternate treatment 15 days, for spraying water once bottom mud is moistened Drying for 5 days, repeated 3 times, a total of 15 days. 8. the method for constructing plow layer soil on coarse sand surface with heavy metal pollution bottom mud according to claim 1, it is characterized in that, the depth of described rotary tillage for the first time is 24cm; The depth of rotary tillage for the second time is 27cm ; The depth of the third rotary tillage is 30cm; the depth of the fourth rotary tillage is 30cm. 9. The application of any one of claims 1-8 to the method of constructing plow layer soil on the coarse sandy surface with heavy metal-contaminated bottom mud in the treatment of heavy metal pollution in bottom mud. 10. The application of any one of claims 1-8 in crop planting using the plowing layer soil obtained by constructing the plowing layer soil method on the coarse sand surface with the heavy metal contaminated bottom mud.