CN107737805A - A kind of ecological restoring method of zinc cadmium heavy-metal contaminated soil - Google Patents

Abstract

The invention discloses an ecological restoration method for zinc-cadmium heavy metal-contaminated soil. By intercropping moso bamboo and sedum sedum with ore, since the root growth layers of the two plants intersect, there is no obvious nutrient competition relationship, and the root systems of the two plants are intercropped. Different depths have different characteristics of fertilizer requirements. The root system of Sedum sedatus generally reaches the soil surface. When the depth reaches 30-40cm, the heavy metals in the soil, such as zinc and cadmium, cannot be absorbed by the roots of Sedum sedum, but the root system of Moso bamboo It can reach 30-40cm, and carry out ecological restoration of heavy metals in the soil below the surface of the polluted soil.

Description

A kind of ecological remediation method of ZnCd heavy metal polluted soil

technical field

The invention relates to the regeneration technology of polluted soil in the field of agricultural soil, in particular to a method for ecological restoration of zinc-cadmium heavy metal polluted soil.

Background technique

The discharge and diffusion of heavy metals into the soil system has brought about increasingly serious pollution problems. How to use environmentally friendly technologies to eliminate heavy metals in soil has become a worldwide problem. According to statistics, there are 150 million mu of land polluted by heavy metals in my country, and the direct loss of crops polluted by heavy metals reaches more than 20 billion yuan every year. Soil Heavy metals accumulate in organisms through the food chain, thus posing a threat to food safety and human health. Phytoremediation is to use the absorption, transformation and storage functions of plants and related soil microorganisms to reduce the concentration or toxicity of pollutants in the environment, so as to achieve the purpose of cleaning the soil. Compared with traditional restoration techniques such as physics, chemistry, and engineering, phytoremediation has the advantages of in-situ restoration, low investment and maintenance costs, environmental friendliness, no secondary pollution, and beautifying the landscape.

Phytoremediation of heavy metal pollution in soil requires a long-term process, and most of the plants used for remediation are of no use value and cannot bring economic income to local farmers. Therefore, some crops have received extensive attention in the application of phytoremediation of soil heavy metal pollution due to their large biomass and certain economic value. Moso bamboo (Phyllostachyspubescens) is one of the most widely distributed and most valuable giant bamboo species in southern my country. It has the characteristics of high biomass energy, convenient cultivation, strong competitiveness, and wide range of uses. and decoration, considered to be the most promising species for carbon sequestration. Moso bamboo can be used as a potential species for phytoremediation because of its high biomass accumulation capacity and high durability to heavy metal-contaminated soil. Sedum plumbizincicola is a Cd/Zn hyperaccumulative plant with strong shade tolerance, and has the characteristics of perennial, large biomass and fast growth.

The existing disclosed technology includes some methods for ecological restoration of soil by intercropping some plants with Sedum sedum, but when Sedum sedum is intercropped with crops such as wheat or rice, due to the intersection of the root growth layers of the two plants , there is an obvious nutrient competition relationship, and due to the activation of the heavy metals in the soil by the roots of Sedum sedum, it may lead to an increase in the absorption of heavy metals in the intercropping crops.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for ecological restoration of soil contaminated with zinc and cadmium heavy metals in view of the deficiencies in the prior art. , there is no obvious nutrient competition relationship, and the root system of the two is different, and the characteristics of fertilizer requirements are also different. Among them, the root system of Sedum sedum is generally the depth of the soil surface. When the depth reaches 30-40cm, the zinc and cadmium in the soil Heavy metals cannot be absorbed by the root system of Sedum sedum, but the root system of moso bamboo can reach 30-40cm, and the ecological restoration of heavy metals can be carried out on the soil below the surface of the polluted soil.

To solve the deficiencies of the above-mentioned technologies, the present invention takes the following technical solutions: a method for ecological restoration of zinc-cadmium heavy metal polluted soil, the steps of which include the following;

(1) Seed selection: Select moso bamboo and select the 2-year-old mother bamboo with strong growth, luxuriant branches and leaves, no pests and diseases, and well-developed fibrous roots to transplant afforestation, in order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots from mother bamboo; For transplantation, select seedlings with the same size and good growth;

(2) Soil preparation: clear up the weeds on the ground before afforestation, and dig the afforestation land to a depth of 30-40cm,

(3) Planting: intercropping moso bamboo and Sedum sedum with ore, wherein the row spacing of moso bamboo is 2m×2.5m, and the planting points are arranged according to rectangles to dig and plant holes. The size of the holes is 60cm×60cm×60cm. balanced growth;

(4) Fertilizer and water: In order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots and bamboo shoots, the bamboo forests are regularly irrigated, weeded, loosened and protected, and late-acting organic fertilizers are applied in autumn and winter, and ditches are opened near the bamboo plants. Cover the soil after fertilization, and apply 20t/ha of slow-acting organic fertilizers such as barn manure and soil miscellaneous fertilizer.

Due to the implementation of the above technical solutions, the present invention has the following advantages compared with the prior art: through the intercropping mode of Phyllostachys pubescens and Sedum sedum associated with ore, since the root growth layers of these two plants intersect, there is no obvious nutrient competition relationship, and The root systems of the two are different in depth, and the characteristics of fertilizer requirements are also different. The root system of Sedum sedum is generally as deep as the soil surface. When the depth reaches 30-40cm, the zinc and cadmium heavy metals in the soil cannot be absorbed by the roots of Sedum sedum. , but the root system of moso bamboo can reach 30-40cm, and the ecological restoration of heavy metals is carried out on the soil below the surface of the polluted soil; in addition, moso bamboo itself is one of the most widely distributed and most valuable giant bamboo species in southern my country, and it has biomass energy. High, convenient cultivation, strong competitiveness, and wide range of uses, such as bamboo used in furniture, building materials, and decoration, is considered to be the most promising carbon sequestration species. Moso bamboo can be used as a potential species for phytoremediation because of its high biomass accumulation capacity and high durability to heavy metal-contaminated soils. Moso bamboo is one of the natural resources with large biomass, fast growth, easy cultivation, high yield and strong renewable ability in the world today. Moso bamboo is also one of the most valuable bamboo plants, widely distributed in China, Japan and other regions, and is considered to be the most promising carbon sequestration species. Bamboo plants grow rapidly, and the daily growth of bamboo shoots can reach 10-20cm during the growth process. Moso bamboo reached the maximum within 2 months, with an average height of 15m and an average aboveground carbon sequestration value (8.13±2.15Mg ha ^-1 year ^-1 ). Its growing area in China exceeds 3.37Mha, accounting for 70% of the total area of bamboo species in China. At present, the average growth rate of China's artificial moso bamboo forest area is 1-2%. Moso bamboo has a huge biomass, and its aboveground biomass can reach about 25t·ha ^-1 . Moso bamboo absorbs heavy metals from polluted soil and transfers them to the body of moso bamboo. The above-ground parts can be used for bamboo processing, house construction, bridges, furniture, pulp and paper manufacturing, etc. after harvesting. Moso bamboo has a wide range of uses and high economic benefits. Bamboo is often used as a substitute for wood. Sedum sedum is a low-growing, perennial Cd/Zn hyperaccumulator, characterized by rapid growth, large biomass, and strong shade tolerance. The intercropping of moso bamboo and sedum sedum not only achieves a reasonable distribution of aboveground and underground space patterns, but also the two plants adsorb heavy metals together, so as to achieve the purpose of efficient management.

detailed description

Embodiment of the present invention is described in further detail below:

The test site is located in Fuyang District, Hangzhou City, Zhejiang Province (119°53′E, 29°52′N), which has a subtropical monsoon climate, with an annual average temperature of 16.2°C, an annual average precipitation of 1452.0mm, and an annual average sunshine duration of 1709.4h .

There are electronics factories and hot-dip galvanizing factories near the research site. The soil was seriously polluted by heavy metals due to the long-term sewage discharge from the factories to irrigate the farmland 10 years ago. This experiment was carried out on the soil compound polluted by various heavy metals (Zn and Cd). According to the soil environmental quality standard (GB 15618-1995), Cd and Zn in this test site greatly exceeded the national level Ⅲ soil pollution standard, and other metals were within the normal range.

Example 1:

Before afforestation, weeds on the ground should be cleared, and the afforestation land should be dug to a depth of 30 cm. This test sets up three sample plots, respectively randomly distributes a single species of moso bamboo (SM), wherein the row spacing of the moso bamboo in Example 1 is 2m × 2.5m, and the planting points are arranged according to rectangles to dig and plant holes, and the size of the holes is 60cm×60cm× 60cm. Phyllostachys pubescens is transplanted and planted with 2-year-old mother bamboos that grow robustly, have luxuriant branches and leaves, are free of diseases and insect pests, and have well-developed fibrous roots. In order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots and bamboo shoots, the bamboo forests are regularly irrigated, weeded, loosened and protected.

Example 2:

Intercropping moso bamboo and sedum sedum (IMS), the row spacing of moso bamboo in Example 2 is 2m * 2.5m, and the planting points are arranged in a rectangle to dig and plant holes, the size of which is 60cm * 60cm * 60cm. Phyllostachys pubescens is transplanted and planted with 2-year-old female bamboos that grow vigorously, have luxuriant branches and leaves, no damage by diseases and insect pests, and well-developed fibrous roots. In order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots from the mother bamboo, the bamboo forest is regularly irrigated, weeded, loosened and protected; the Sedum sedum is transplanted from the nursery, and the seedlings with the same size and good growth are selected. Moso bamboo was planted in October 2012, and Sedum sedum was planted in March 2013.

Example 3:

Uncultivated crops are used as blank control (CK), and the three plots of the above three embodiments are closely adjacent, and each sample plot is an area of 10m × 20m.

Soil samples were collected from the above three test areas in August 2016. The young bamboos in the test site are grown from shoots from the mother bamboo, and the test bamboo forest is a forest of different ages. The distribution of bamboo ages is as follows: 1-year-old moso bamboos are about 70 plants/mu, 2-year-old moso bamboos are about 100 plants/mu, and 3-year-old moso bamboos are about 60 plants/mu. In each sample plot, randomly select 5 soil profiles according to the "S" shape, then take the upper 0-20cm soil, collect soil samples, and put them into sealed plastic bags. After returning to the laboratory, pick out the gravel and plant residues from the fresh soil, divide the soil samples into two parts, and store one part immediately in a sterilized ziplock bag for frozen storage, which is used to extract soil microbial DNA for the soil microbial community. For structural analysis, another soil sample was spread on kraft paper for natural air drying. After mixing thoroughly, use the quartering method to continuously sieve the samples < 2mm, 0.25mm and 0.149mm, grind them into fine powder, put them into new ziplock bags, and store them at room temperature until analysis.

It can be seen from the soil heavy metals and available heavy metal contents in the three modes (Table 1), the total and available Zn and Cd contents are the lowest in the IMS soil, followed by SM, and the heavy metal content in the control group CK is the highest. In IMS soil, the total Zn and total Cd contents were 21.6% and 23.6% lower than those in CK soil, respectively (P<0.01). Total Zn and total Cd contents were not significantly different between SM and IMS planting patterns. In IMS soil, the effective Zn content was lower than 5.2% and 28.7% in SM and CK, respectively, and the difference with SM was not significant, but the difference with CK was more obvious (P<0.01); the total Cd content was significantly lower than SM and CK were 5.3% and 48.5% respectively (P<0.01).

Table 1 Contents of total heavy metals and available heavy metals in soil under different models

Lowercase letters (a, b, c) indicate significant differences between different models (P<0.05)

Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Apparently, the technical solutions of the present invention are not limited to the above-mentioned embodiments, and many variations are possible. All deformations that those skilled in the art can directly derive or associate from the content disclosed in the present invention should be considered as protection scope of the present invention.

Claims (2)

1. an ecological restoration method of zinc-cadmium heavy metal-contaminated soil is characterized in that moso bamboo and sedum sedum associated with mine are intercropped in the soil area of zinc-cadmium heavy metal compound pollution, and harvest moso bamboo in about 6 years. The steps include the following; (1) Seed selection: Select moso bamboo and select the 2-year-old mother bamboo with strong growth, luxuriant branches and leaves, no pests and diseases, and well-developed fibrous roots to transplant afforestation, in order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots from mother bamboo; For transplantation, select seedlings with the same size and good growth; (2) Soil preparation: clear up the weeds on the ground before afforestation, and dig the afforestation land to a depth of 30-40cm, (3) Planting: intercropping moso bamboo and sedum sedum with ore. The row spacing of moso bamboo is 2m×2.5m, and the planting points are arranged according to rectangles to dig planting holes. The size of the holes is 60cm×60cm×60cm. grow; (4) Fertilizer and water: In order to improve the survival rate of moso bamboo and promote the growth of bamboo shoots and bamboo shoots, the bamboo forests are regularly irrigated, weeded, loosened and protected, and late-acting organic fertilizers are applied in autumn and winter, and ditches are opened near the bamboo plants. Cover the soil after fertilization, and apply 20t/ha of slow-acting organic fertilizers such as barn manure and soil miscellaneous fertilizer. 2. the ecological restoration method of a kind of zinc-cadmium heavy metal polluted soil according to claim 1, is characterized in that, described moso bamboo is tall and large giant bamboo species, and planting density is less.