Background technology
The efficient of plant extract recovery technique depends on the absorption to the heavy metal biological available state to a great extent.Available state is meant that part of heavy metal that can be absorbed by the biology of surviving on this soil (being generally plant).In general, the available state content of heavy metal in the middle of soil is lower, make it can not be repaired plant absorbing and transfer effectively, and chemical enhanced method mainly is meant by add foreign substance in contaminated soil, perhaps directly combine with heavy metal, thereby the form of change heavy metal and biological effectiveness etc., final fortification of plants is to the absorption of heavy metal.Surfactant-chelating agent synergy recovery technique is to carry out in the later stage nineties 20th century, its essence is and utilize the solubilising of surfactant pollutant, incremental effect and chelating agent remove in the environment indissoluble to the chelation of pollutant and separate, difficult degradation, the difficult organic pollution that utilizes utilizes surfactant lubricated, solubilising, disperse, characteristics such as washing, change the soil surface electric charge and absorb potential energy, or heavy metal is cemented out from soil surface, with complexing, the form of chelate is present in the soil liquid, accelerate the flowability [document 1: Wang Liwei of heavy metal in the soil liquid, Chen Yucheng, Dong Shan swallow .2004. surfactant and chelating agent are to the influence of plant absorbing Cd and Cu. Agricultural University Of Southwest's journal (natural science edition), 26 (6): 745-749].
Surfactant mainly contains two kinds to the solubilizing mechanism of pollutant in soil: a kind of is when its concentration is lower than CMC, its hydrophobic side is wrapped in pollutant in the surfactant molecule, make the outside and soil particle thing surface generation repulsive interaction of water-wet side, the surface area that convection current in the solution simultaneously, the motion of migration equimolecular provide enough energy to increase nonaqueous phase makes nonaqueous phase disengaging soil particle thing and plays solubilization; Another kind is to form micella during greater than CMC when surfactant concentration, pollutant enters the hydrophobic center of micella by distributional effects and enters liquid phase, make and be adsorbed pollutant and enter water [document 2:DoongR A, Wu Y W, Lei W is enhanced remediation of cadmiumcontaminated soils.Water Science and Technology G.1998.Surfanctant, and 37 (8): 65-71].Surfactant promotes the mechanism of action of plant absorbing heavy metal to destroy the relevant [document 3: Chen Yucheng of cell leakage with surfactant, Xiong Shuanlian, Xiong Zhi prolongs the feasibility that the .2004. surfactant is strengthened the heavy metal pollution phytoremediation. ecological environment, 13 (2): 243-246].Surfactant is a kind of solubility, amphipathic special lipoid substance, be different from the expansile lipoid substance of insoluble and tool that constitutes the biomembrane composition, it has higher monomer solubility in water, it is amphipathic make it with film in the hydrophilic and lipophilic group of composition interact, thereby change the structure and the saturating property of film, impel the absorption of plant heavy metal.Discover that surfactant has solubilization and incremental effect to micro heavy cation in the soil, and the chain of surfactant is long more, its effect is high more.
The basic principle of chelation evoked technology be the balance of disturbance pollutant between liquid phase of soil concentration and solid concentration [document 4: chelation evoked technology and environmental risk thereof that Luo Yongming .2000. fortification of plants is repaired. soil, (2): 57-61
1Chelation specifically is meant, with a kind of dentate (L
M-) add soil system, because of with chelation (pressing 1: the 1 chelatropic reaction) free metal ion (M of dentate
N+) activity low:
Because the minimizing of ion valence mumber or the variation of symbol, soil reduces greatly to the sticking intensity of metal-coordination complex, for keeping free metal (M
N+) equilibrium relation between solution and solid particle, metal is from the soil particle surface desorption.The formation constant of this chelatropic reaction (also being called stability constant) can be decided to be: K
f={ M
L N-m}/{ M
N+{ L
M-, in the formula this metal, dentate and the metal-ligand molar concentration in solution.Generally speaking, the stability constant of the chelate that certain chelating agent and heavy metal ion form is big more, and the ability that this kind chelating agent activates corresponding heavy metal is strong more, this heavy metal concentration is also just high more in the soil liquid, for Cd, and Cu, Pb, Zn, DTPA>EDTA>HEDTA>NTA; Concerning same dentate, Cu>Pb>Zn>Cd normally.As seen, the selection of success or not of using chelation evoked technology fortification of plants to extract to repair and chelating agent type is closely related.The effect of chelating agent inducing plant reparation is confirmed by a large amount of practice, wherein, existed test results shows, DTPA and EDTA be the most effective [document 5:Grcman H aspect increase plant absorbing Pb amount, Velikonja-Bolta S, Vodnik D, et al.2001.EDTA enhanced heavymetal phytoextraction:metal accumulation, leaching and toxicity.Plant andSoil, 235:105-114], EGTA is then to the most effective [the document 6:Blaylock M J of Cd, Salt DE, Dushenkov S, et al.1997.Enhanced accumulation of Pb in Indian mustard bysoil-applied chelating agents.Environmental Science and Technology, 31:860-865].
Summary of the invention
The object of the present invention is to provide a kind of under chemical intensified condition the method for repairing soil with cadmium pollution by hollyhock.
To achieve these goals, the technical solution used in the present invention is as follows:
The method of cadmium pollution soil repair: be subjected to apply in the cadmium pollution soil 0.5-2.0mmol chelating agent and 0.5-2.0mmol surfactant at every kilogram, then plant hollyhock, thereby realize removing the purpose of excessive cadmium in the soil, wherein chelating agent is ethyleneglycol bistetraacetic acid (EGTA), and surfactant is lauryl sodium sulfate (SDS).
Described ethyleneglycol bistetraacetic acid and lauryl sodium sulfate all are applied in the soil together with solid form and cadmium.The plantation hollyhock is to adopt outdoor planting in cadmium pollution soil, and the hollyhock of seedling phase is transplanted in the cadmium pollution soil that contains ethyleneglycol bistetraacetic acid and lauryl sodium sulfate, regularly waters, and makes soil moisture content remain on the 75-85% of field capacity.Behind plantation hollyhock on the cadmium pollution soil, hollyhock absorbs cadmium and shifts to overground part from contaminated soil, when hollyhock grows to florescence, plant is removed from contaminated soil, plant second batch of hollyhock again, repeat aforesaid operations, the cadmium content in soil reaches environmental safety standard.
The advantage that the present invention had:
The method of employing heavy metal cadmium accumulation of the present invention has significantly improved the total amount of hollyhock overground part accumulation Cd, has strengthened the efficient that hollyhock is repaired the Cd contaminated soil effectively.The present invention is an original position repairing polluted soil technology, does not destroy the place, and is little to the disturbance of soil, expensive less, and the technology operation is fairly simple, implements on a large scale easily.When administering the Cd contaminated soil, beautified environment again, be easy to accept into society.Adopt rehabilitating soil of the present invention, the hollyhock of results can be used as ornamental flower (commodity) and sells, when obtaining economic benefit, automatically obtain the cost free of biomass handled that (huge numbers of families can throw away separately dustbin to used flowers, along with the processing of rubbish, just solved the processing of biomass).Therefore, extensive cultivation means extensive reparation, also means by the exchange of commodities simultaneously and obtains bigger economic benefit.Certainly, if do not consider cost, can focus on, perhaps sanitary landfills is perhaps carried out resource processing and is handled, and reclaims cadmium wherein, thereby also can create some economic benefits.
The specific embodiment
Embodiment 1: at 30mg kg
-1The chemical enhanced experiment of Cd contaminated soil
Experimental design and experiment condition:
Experimental design is as shown in table 1.Wherein, testing the Cd form that adds is CdCl
22.5H
2O is AR.Experiment with soil pick up from ecological station, Chinese Academy of Sciences Shenyang (geographical position be 123 ° 41 of east longitude ', 41 ° 31 of north latitude ') fallow ground (for the pollution-free area) table soil (0~20cm), soil types is a meadow burozem, soil physico-chemical property is a pH value 6.59, organic matter 1.19%, total nitrogen 0.85g kg
-1, available phosphorus 8.96mg kg
-1, effective potassium 95.21mg kg
-1
Cd concentration is 30mg kg in table 1 soil
-1The time each chemical enhanced processing composition and concentration
Handle |
?Cd(mg?kg
-1)
|
SDS(mmolkg
-1)
|
?EGTA(mmol?kg
-1)
|
CK1 TA1 TA2 TA3 TA4 TA5 TA6 TA7 |
30 30 30 30 30 30 30 30 |
0.5 1.0 2.0 0.5 1.0 2.0 |
1.0 1.0 1.0 1.0 |
In April, 2006, will be for examination soil air-dry and cross the 4.0mm sieve after, according to the reagent mix of concentration design with respective amount, the plastic tub of packing into (Φ=20cm, H=15cm) in, every basin 2.5kg, balance one month is stand-by.Simultaneously, carry out growing seedlings of flowers, concrete grammar is: flower seed is placed the seedling-raising box of pre-installing sandy soil, and sand/soil 1: 3 is treated to be transplanted in the above-mentioned processing soil after seedling grows 5~6 leaves.Select the consistent seedling of growth to be transplanted into respectively in each basin of handling.According to the plant size, every basin is planted 3 seedlings, plant between each repeats into seedling count unanimity.
Potted plant experiment place is located in the open-air solarium of ecological institute, Chinese Academy of Sciences Shenyang, and this place is at the center, Shenyang City, the about 50m of height above sea level, and experiment does not have pollution sources around the place, is the uncontaminated district of heavy metal, belongs to partly moistening continental climate of temperate zone.According to soil moisture situation in the basin, irregularly water running water (not detecting Cd in the water), make soil moisture content often remain on 75~85% of field capacity.Plant grows in the Cd contaminated soil and gathers in the crops plant after 4 months.
Sample analysis and data analysis:
The plant sample of results is divided into root, stem and leaf 3 parts, fully washes with removal with running water and adhere to earth and dirt on the plant sample, and then use deionized water rinsing, the drop branch that anhydrates, the 20min that completes under 105 ℃ dries to constant weight under 70 ℃ then.Plant sample after the oven dry is pulverized standby.It is standby that 100 mesh sieves are crossed in the air-dry back of pedotheque.Plant and pedotheque all adopt HNO
3-HClO
4Method digestion (the two volume ratio is 1: 3).The atomic absorption spectrophotometer method is measured the content of beary metal in plant and the soil-like, and atomic absorption spectrophotometer is the 180-80 of a Hitachi type, and the wavelength of its Cd is 228.8nm.Gained The data Excel XP and DPS handle, and listed result is mean value ± standard deviation.
Experimental result:
In whole growth process, hollyhock does not show the symptom that poisoned by heavy metal Cd, has stronger patience.As shown in Figure 1, CK1 compares with control treatment, each chemical enhanced processing all increases the overground part dry weight of hollyhock, as seen the adding of EGTA and SDS has promoted the growth of hollyhock, especially handle for TA4, biomass has increased by 66.0%, and difference is tangible (P<0.05), and be single EGTA intensive treatment this moment.
As shown in Figure 2, the overground part heavy metal Cd concentration of hollyhock is all greater than root, and promptly transfer ratio is greater than 1; And all greater than Cd concentration in the corresponding soil, promptly concentration coefficient is greater than 1 for overground part heavy metal Cd concentration.In addition, the overground part Cd concentration of hollyhock is compared with control treatment CK1 all under the chemical enhanced treatment conditions significantly increases (P<0.05), and wherein, the overground part Cd concentration that TA6 and TA7 handle is respectively 119.1 and 131.9mg kg
-1, surpassed the critical content standard value 100mg kg of Cd hyperaccumulative plant
-1, the root heavy metal concentration of this moment is respectively 50.9 and 67.5mg kg
-1The result that comprehensive patience is analyzed, the EGTA of suitable concentration and SDS complex intensifying are handled and can be made the hollyhock that is grown in this soil possess the essential characteristic of Cd hyperaccumulative plant.
Using hyperaccumulative plant, to carry out the heavy-metal contaminated soil reparation be that the final purpose of plant extract reparation is to wish that its overground part can accumulate heavy metal as much as possible when the results rehabilitation plant, because overground part is to be easier to the position that gathers in the crops and handle.As shown in Figure 3, under each chemical enhanced treatment conditions, the Cd total amount of the overground part accumulation of hollyhock is compared with control treatment all significantly increases (P<0.05), be that the Cd total amount that hollyhock is extracted from soil increases, as seen, the adding of EGTA and SDS can improve the efficient that the hollyhock plant extract is repaired the Cd contaminated soil effectively, and maximum Cd extracted amount (TA7) is 3.95 times of control treatment.
Embodiment 2: at 100mg kg
-1The chemical enhanced experiment of Cd contaminated soil
Experimental design is as shown in table 2, and experiment condition and sample are identical with embodiment 1 with data analysis.
Cd concentration is 100mg kg in table 2 soil
-1The time each chemical enhanced processing composition and concentration
Handle |
?Cd(mg?kg
-1)
|
SDS(mmol?kg
-1)
|
?EGTA(mmol?kg
-1)
|
CK2 TB1 TB2 TB3 TB4 TB5 TB6 TB7 |
100 100 100 100 100 100 100 100 |
0.5 1.0 2.0 0.5 1.0 2.0 |
1.0 1.0 1.0 1.0 |
Experimental result:
For 100mg kg
-1Cd pollutes processing, hollyhock except that plant height than the processing that does not add heavy metal Cd short slightly, do not show the symptom that poisoned by heavy metal Cd.As shown in Figure 4, CK2 compares with control treatment, and the overground part dry weight of TB1, TB2, TB4 and TB5 all obviously increases (P<0.05), and as seen, the EGTA of suitable concentration and the adding of SDS can promote 100mg kg
-1The growth of hollyhock in the Cd contaminated soil.
As shown in Figure 5, except that TB2 and TB3 handled, the overground part heavy metal Cd concentration of all the other chemical enhanced processing all was higher than root, and promptly transfer ratio is greater than 1, and overground part heavy metal Cd concentration is all greater than Cd concentration in the corresponding soil, and promptly concentration coefficient is greater than 1; Especially, the overground part Cd concentration of these chemical enhanced processing is compared with control treatment all obviously increases (P<0.05), has surpassed the critical content standard value of Cd hyperaccumulative plant.Therefore, Ci Shi hollyhock has also possessed the essential characteristic of Cd hyperaccumulative plant.
As shown in Figure 6, except that TB3 and TB7 processing, the Cd total amount of the hollyhock overground part accumulation of all the other chemical enhanced processing is compared with control treatment all significantly increases (P<0.05), as seen, although the Cd level of pollution has reached 100mg kg
-1, the EGTA of suitable concentration and the adding of SDS also can improve the efficient that the hollyhock plant extract is repaired the Cd contaminated soil effectively, and maximum Cd extracted amount (TB5) is 2.27 times of control treatment.
Embodiment 3
Difference from Example 1 is:
Be subjected to apply in the cadmium pollution soil 0.5mmol EGTA and 1mmolSDS at every kilogram, then plant hollyhock, thereby realize removing the purpose of excessive cadmium in the soil.
Embodiment 4
Difference from Example 1 is:
Be subjected to apply in the cadmium pollution soil 2mmol EGTA and 0.5mmolSDS at every kilogram, then plant hollyhock, thereby realize removing the purpose of excessive cadmium in the soil.