CN104126405B - The fixing restorative procedure of plant of heavy metal copper, lead contamination calcareous soil - Google Patents

Abstract

The present invention relates to the fixing restorative procedure of plant of a kind of heavy metal copper, lead contamination calcareous soil, the method refers to that first on heavy metal copper, lead contamination calcareous soil, being deeply not less than 0.8m kind according to the density of 1.5 × 1.5m, planting hole plants arbor, and intercropping shrub and herbaceous plant, build the tall careless three-dimensional reparation pattern of filling with; Then described arbor is cultivated according to a conventional method; Finally, in the time of described Tree growth to 5 ~ 7 year according to by material object, it being carried out to intermediate cutting or clear felling. The present invention's safety, green, non-secondary pollution, easily accepted by the public, can be applicable to pollution of area source reparation, and can increase the soil organism, increase soil fertility and bring economic benefit.

Description

Phytofixation method of heavy metal copper and lead polluted calcareous soil

technical field

The invention relates to a phytoremediation technology for polluted environment, in particular to a phytofixation and remediation method for heavy metal copper and lead polluted calcareous soil.

Background technique

Sewage irrigation, sludge agricultural use, and extensive application of pesticides and fertilizers have resulted in the widespread pollution of copper (Cu), lead (Pb) and other heavy metals in farmland in arid areas. According to the survey results of the soil status of the Ministry of Environmental Protection, the area of cultivated land polluted by heavy metals in China has reached 20 million hm ² , which accounts for about 14.8% of the existing cultivated land area of 2.027 billion mu in China announced by the Ministry of Land and Resources in 2012. As a result, my country's annual grain production reduction due to heavy metal pollution exceeds 10 million tons, resulting in a total economic loss of at least 20 billion yuan. Oasis is the basic unit of industrial and agricultural production in arid areas. Its area only accounts for 3-5% of the total area of arid areas, but it has raised more than 90% of the population in arid areas and created more than 95% of industrial and agricultural output value. my country's arid areas are rich in mineral resources, but the oasis farmland around the mining area has generally been seriously polluted by heavy metals during the development of mineral resources. For heavy metal polluted farmland, continuing to plant food crops or pastures will threaten the safety of agricultural products; if the heavy metals in the abandoned soil will cause secondary pollution with wind erosion and water erosion, it will also threaten the red line of my country's 1.8 billion mu of cultivated land. Therefore, the restoration of heavy metal-contaminated cultivated land in arid areas is an urgent environmental problem to be solved.

Phytoremediation is a heavy metal-contaminated soil remediation technology that has emerged in recent years. Compared with traditional physical and chemical remediation technologies such as soil, landfill and leaching, it is economical, environmentally friendly, does not damage soil properties, The ability to restore and improve soil quality is an effective means of remediating soil non-point source pollution, especially heavy metal polluted farmland soil. Phytoextraction and phytofixation are two important aspects of phytoremediation. However, based on the alkaline pH and high calcium carbonate content of soil in arid areas, the content of metal ions in soil solution in arid areas is usually low, which in turn limits the extraction and restoration of heavy metals in soil by plants. Therefore, considering the low bioavailability of heavy metals in soils in arid regions, phytofixation is the preferred technology for remediation of heavy metal-contaminated soils in arid regions.

The tree-shrub-grass plant system is a three-dimensional restoration model with a specific community structure and function formed by mixing trees, shrubs and herbs in different proportions and ways. Compared with a single arbor forest, in terms of ecological function, the three-dimensional restoration model can increase the tree height, diameter at breast height and stand biomass of the arbor; improve the physical and chemical properties of the soil, and increase the accumulation of organic matter and nutrients (N, P, K) in the surface soil; Increase the soil moisture content to make the tree root distribution deeper and more evenly. In terms of fixed restoration of heavy metals, the three-dimensional restoration mode can prevent the migration of heavy metals caused by soil diffusion induced by wind erosion, water erosion, and leaching in the early stage of the establishment of a single arbor forest; the three-dimensional restoration mode is also more conducive to absorption and enrichment through the root system, Adsorption on the surface or precipitation in the root zone fix heavy metals in the soil. Therefore, it is of great scientific value and practical significance to carry out research on the three-dimensional restoration model of trees, shrubs and grasses in heavy metal-contaminated soils.

Contents of the invention

The technical problem to be solved by the present invention is to provide a safe, green and non-secondary pollution-free plant fixation method for calcareous soil polluted by heavy metal copper and lead.

In order to solve the above problems, the plant fixation repair method of heavy metal copper and lead polluted calcareous soil according to the present invention is characterized in that: the method refers to at first on heavy metal copper and lead polluted calcareous soil according to the density of 1.5 * 1.5m 1. Planting trees with a depth of not less than 0.8m, and interplanting shrubs and herbaceous plants to construct a three-dimensional restoration model of trees, shrubs and grasses; Thinning or clearcutting can be carried out according to the purpose of timber use.

The heavy metal copper and lead polluted calcareous soil refers to one of chernozem, chestnut soil, cinnamon soil, black loam, lime calcic soil and brown calcic soil.

The arbor refers to the annual Qingpi type Xinjiang poplar seedlings or the white-bark type Xinjiang poplar seedlings.

The shrub refers to Nitraria or Hippophae rhamnoides.

The herbaceous plant refers to one of Artemisia camelus, camel's cape, and multi-lobed camel's cape.

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

1. The present invention adopts the three-dimensional restoration model of trees, shrubs and grasses. The three types of plants have different habitats, and they can have beneficial effects on each other. Among them, shrubs and herbaceous plants can shoulder the responsibility of wind erosion resistance and protection in the initial stage of arbor forest establishment. The effect of water erosion can also make the distribution of arbor roots deeper and more uniform during the growth of arbor forests, thereby preventing secondary pollution of heavy metals caused by soil diffusion caused by wind erosion, water erosion, and infiltration. Therefore, this three-dimensional restoration model is very suitable for the fixed restoration of heavy metal-contaminated soil in arid areas.

2. In the three-dimensional restoration model of trees, shrubs and grasses adopted in the present invention, the three types of plants all have very strong fixation and repair ability to heavy metals Cu and Pb. In addition, the bioavailability of Cu and Pb in the calcareous soil in arid areas is inherently low, so There is no need to add additional soil additives such as lime, phosphate, organic matter, and iron-containing minerals to inhibit the activity of heavy metals, so this three-dimensional restoration mode is a safe and economical restoration technology.

3. The three-dimensional restoration model of trees, shrubs and grasses used in the present invention belongs to the in-situ restoration technology, with little environmental disturbance and low investment in the early stage. In addition, the selected arbor Xinjiang poplar is widely planted in the arid area of Northwest my country and it has both ecological and ecological characteristics. Therefore, this three-dimensional repair model is easy to promote in arid areas and can be accepted by the public. It can also bring benefits to farmers while repairing polluted soil. It is a "remediation while production" technology that can protect polluted soil Sustainability of restoration and utilization.

4. The invention is safe, green, free of secondary pollution, easily accepted by the public, applicable to non-point source pollution restoration, and can increase soil organic matter, improve soil fertility and bring economic benefits.

detailed description

The plant fixation repair method of heavy metal copper and lead polluted calcareous soil refers to firstly planting arbors on the heavy metal copper and lead polluted calcareous soil according to the density of 1.5×1.5m and the depth of the planting hole is not less than 0.8m, and through Sowing seeds or transplanting seedlings to interplant shrubs and herbaceous plants to construct a three-dimensional restoration model of trees, shrubs and grasses; then, the trees are cultivated according to conventional methods; finally, when the trees grow to 5 to 7 years, they are cultivated according to the purpose of use. Thinning or clearcutting is sufficient.

Among them: Calcareous soil polluted by heavy metal copper and lead refers to one of chernozem, chestnut soil, cinnamon soil, black loam soil, lime calcic soil and brown calcic soil.

The arbor refers to the annual seedlings of Populus sinensis of the type of green skin or the seedlings of Populus sinensis of the type of white skin.

Shrub refers to Nitraria or seabuckthorn.

The herbaceous plant refers to one of Artemisia camelus, camel's cape, and multi-lobed camel's cape.

Application Example 1 The test site is located in Baiyin District, Baiyin City, Gansu Province (103°53′24′′~104°24′55′′E, 36°14′38~36°47′29′′N), which is my country's It is an important resource-based city mainly based on Cu resources, and it is also one of the old industrial bases that the country focused on in the 1950s. This area is located in the hinterland of the mainland, which is a continental arid and semi-desert climate zone in the middle temperate zone. The soil is lime-calcium soil, and loess is its soil-forming parent material.

In the process of resource development, the farmland around the mining area is generally seriously polluted by heavy metals such as Cu and Pb, which leads to a reduction in food production and poses a threat to animal and human health. Therefore, local farmers have changed the planting structure of heavy metal-contaminated farmland in the region, no longer planting wheat, corn and other food crops, and planting poplar and other bioenergy plants instead. After years of development, the plant community structure of "Xinjiang Poplar-Nitraria-Camelia" has gradually formed.

Random sampling method was used to collect the three species of Populus xinjiang, Nitraria and Camelia which grew on the above-mentioned polluted soil, and the whole plant of each plant was collected, and 5 plants were collected respectively. Xinjiang poplars were divided into 3-year, 5-year-old and 7-year-old according to tree age, and collected separately. While collecting the plants, the plant root zone and bare soil are also collected, and brought back to the laboratory together with the plants for further processing and analysis.

(1) Restoration of soil quality by tree-shrub-grass plant system (see Table 1):

Table 1 Effects of tree-shrub-grass plant system on soil physical and chemical properties

It can be seen from Table 1 that the three-dimensional restoration model of trees, shrubs and grasses can increase the proportion of silt particles (0.05-0.002 mm) and clay particles (<0.002 mm) in heavy metal-polluted soil, and improve soil texture. Compared with the bare soil, the percentages of silt and clay in the root zone of the tree-shrub-grass plant system increased by 17% and 36%, respectively. The tree-shrub-grass plant system helps to increase the organic matter content of the polluted soil, which is 38% higher than that of the bare soil. In addition, the tree-shrub-grass plant system also helps to improve soil fertility and soil nutrients. The content of total nitrogen and total phosphorus in the soil increased by 29% and 15% respectively compared with the bare soil. It can be seen that the three-dimensional restoration model of trees, shrubs and grasses has a very good effect on improving soil quality.

⑵ Fixation and repair of Cu in soil by tree, shrub and grass plant system (see Table 2):

Table 2 Accumulation characteristics of Cu by different plants under field conditions

The enrichment characteristics of Cu in calcareous soil by different plants in the tree-shrub-grass plant system are shown in Table 2. It can be seen that the Cu content in the root zone soil of the three plant species is quite different, which reflects the heterogeneity of the distribution of heavy metals in the soil under natural conditions. There were great differences in the uptake of Cu among three species of trees, Populus sinkiangi, shrub Nitraria, and herbaceous plant Camelia.

The critical content of Cu in the aboveground part of the plant in the soil fixation restoration is 40mg/kg. The content of Cu in the aboveground part of the three plants in this experiment is far less than the critical value. ) are less than 1, indicating that the tree-shrub-grass plant system composed of three species of Xinjiang poplar, Nitraria and Camelia is conducive to the fixation and repair of Cu in calcareous soil.

(3) Fixation and restoration of Pb in soil by tree, shrub and grass plant system (see Table 3):

Table 3 The enrichment characteristics of Pb in different plants under field conditions

Table 3 shows the enrichment characteristics of Pb in calcareous soil by three plants in the tree-shrub-grass plant system. Like Cu, the distribution of Pb in root zone soil also showed heterogeneity. The order of the content of Pb in the roots and shoots of the three plants was the same as that of Cu, which was Camelia > Nitraria > Populus Xinjiang. According to the critical content (100 mg/kg) of Pb in the aboveground part of plants in fixed restoration, the Pb content in the aboveground part of the three plants in this experiment was all within the critical content threshold range. In addition, the BCFs of Populus xinjiang and Nitraria to Pb were less than 0.1, and the BCF of Camelia was less than 1, which indicated that the three plants had the characteristic of rejecting Pb. Although the TF of Nitraria to Pb is greater than 1, the Pb content in the body is still within the normal range of Pb content in plants. Therefore, the tree-shrub-grass plant system composed of Xinjiang poplar, Nitraria and Camelia is also conducive to the fixation and repair of Pb in calcareous soil.

⑷ Growth characteristics of poplar in tree-shrub-grass plant system:

The growth of Populus Xinjiang of different ages on Cu and Pb polluted calcareous soil is shown in Table 4. It can be seen that the total growth in DBH and plant height gradually increases with tree age. According to the planting density of 4500 plants per hectare (the distance between plants and rows is 1.5×1.5m), the total stock volume of Populus Xinjiang for 3 years, 5 years and 7 years can reach 12.704, 54.898 and 175.25m ³ /hm ² respectively. The average annual growth in diameter at breast height showed a slight decrease in 5-year-old forest age, but the plant height reached the maximum at 5-year-old forest age, indicating that this stage is the stage of rapid growth of Xinjiang poplar radial growth. For 7-year-old Xinjiang poplar, its radial growth begins to slow down, while its lateral growth accelerates, that is, the poplar begins to thicken rapidly, and the average annual stock volume of poplar at this stage is significantly higher than that of 3-year and 5-year-old poplar.

Table 4 Growth process of Populus xinjiang in tree-shrub-grass plant system on heavy metal-polluted calcareous soil

Therefore, according to different timber purposes, Xinjiang poplar can be thinned or cleared in 5 to 7 years, which can bring benefits while repairing heavy metal-contaminated soil. It can realize "remediation while production" of polluted soil and ensure pollution Sustainability of soil remediation and utilization.

Application Example 2 The test site is located at the Biological Experiment Station (104°09′E, 35°56′N) of Lanzhou University Yuzhong Campus. The tested Cu and Pb polluted calcareous soils were collected from farmland irrigated with sewage in the Dongdagou River Basin of Baiyin City. The calcium carbonate contents of soils with two different pollution degrees (M and S) were 69.68 and 81.03 g/kg, respectively. The annual Xinjiang poplar seedlings for testing were purchased from Gansu Greening Seedstock Base.

Add 0.25 gN/kg (in the form of NH ₄ NO ₃ ) and 0.10 gP/kg (in the form of K ₂ HPO ₄ ) to 7.5 kg of contaminated soil (on a dry weight basis) passed through a 10 mm sieve before planting plants As a base fertilizer, mix it well and put it into plastic pots (H=26.5cm, D=22.5cm); then plant 2 annual Xinjiang poplar seedlings of the same size in each pot in April. The pots were placed in an outdoor field, and the soil moisture was replenished with tap water (heavy metals were not detected) to keep it at about 60% of the field water capacity. Before the poplar leaves fell in October, they were divided into three parts: roots, trunks and leaves to collect, and brought back to the laboratory for further processing and analysis.

(1) Cu enrichment characteristics of Populus xinjiang:

The enrichment characteristics of Cu in calcareous soil of Populus Xinjiang under potted conditions are shown in Table 5. It can be seen that the contents of Cu in soil M and S are similar. On the two soils with different pollution degrees, the Cu content in different organs of Populus xinjiang was in the order of root>leaves>trunk, and the BCF of different organs to Cu was less than 0.1. In addition, the transfer ability of Cu from the roots to shoots of Populus xinjiang was weak, and the TFs of trunks and leaves were both less than 0.1 and 1 in both soils. This indicated that Populus xinjiang had a strong ability to reject Cu in calcareous soil, which was beneficial to the fixation and restoration of Cu.

Table 5 Cu enrichment characteristics of Populus Xinjiang under potted conditions

(2) The enrichment characteristics of Pb in Xinjiang poplar:

Table 6 shows the enrichment characteristics of Pb in calcareous soil of Populus Xinjiang under potted conditions. The content of Pb in soil M and S was quite different. On the two soils with different pollution degrees, the order of Pb content in different organs of Populus xinjiang was the same as that of Cu, which was root>leaves>trunk. In addition, the Pb enrichment and transfer ability of P. xinjiang was also very weak. The BCF of Pb in different organs on the two soils was less than 0.1, and the TF of Pb from the root to the shoot of P. xinjiang was also less than 1.

Table 6 The enrichment characteristics of Pb in Xinjiang poplar under potted conditions

It can be seen that Populus Xinjiang has a strong ability to reject Cu and Pb, which is beneficial to the fixation and restoration of Cu and Pb in calcareous soil. In nature, the Cu content in plants usually ranges from 5 to 20 mg/kg, and the Pb content ranges from 0.2 to 20 mg/kg. In this test, the contents of Cu and Pb in the trunk and leaves of Xinjiang poplar were within the normal range. Therefore, the trunk and leaves of Populus xinjiang grown on contaminated calcareous soil can be safely used for bioenergy, and the leaves can also be used for animal feed. Remediation of Cu and Pb polluted calcareous soils in arid regions by using Populus xinjiang is a safe, green and economical remediation technology.

Claims (1)

1. the fixing restorative procedure of the plant of heavy metal copper, lead contamination calcareous soil, is characterized in that: the method refers to first heavyOn metallic copper, lead contamination calcareous soil, be deeply not less than 0.8m kind according to the density of 1.5 × 1.5m, planting hole and plant arbor, andDo shrub and herbaceous plant, build the tall careless three-dimensional reparation pattern of filling with; Then described arbor is cultivated according to a conventional method; ?After, in the time of described Tree growth to 5 ~ 7 year according to by material object, it being carried out to intermediate cutting or clear felling; Described heavy metal copper,Lead contamination calcareous soil refers to the one in chernozem, chestnut soil, cinnamon soil, black mature soil, sierozem, brown soil; Described arbor isRefer to the Xinjiang poplar seedling of annual rascal type or the Xinjiang poplar seedling of white skin type; Described shrub refers to Bai Ci or sea-buckthorn; InstituteStating herbaceous plant is the one referring in camel wormwood artemisia, harmel, Herba Pegani harmalae.