CN112285096B - Heavy metal contaminated soil ecological risk assessment method - Google Patents
Heavy metal contaminated soil ecological risk assessment method Download PDFInfo
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Abstract
The invention relates to the field of soil pollution risk management and control and ecological risk evaluation, and discloses a heavy metal polluted soil ecological risk assessment method, which comprises the following steps: firstly, constructing a functional relation C1 (pH) between the leaching concentration of heavy metals in a soil sample and the pH value of an extractant; then, constructing a functional relation C2 (pH) between the acid soluble state concentration of the heavy metal in the soil sample and the pH value of the leaching agent; then, calculating the heavy metal risk concentration C in the soil sample risk ：C risk =0.5 xc 1 (pH) +0.5 xc 2 (pH); subsequently, determining the total concentration C3 of heavy metals in the soil sample; and finally, calculating the ecological risk R of the heavy metal polluted soil: r = C risk and/C is 3 multiplied by 100%, and the risk grade is divided according to the ecological risk R of the heavy metal polluted soil. The assessment method provided by the invention is more strict, scientific and reasonable, and is more beneficial to protecting the ecological environment.
Description
Technical Field
The invention belongs to the field of soil pollution risk control and ecological risk evaluation, and particularly relates to an ecological risk evaluation method for heavy metal polluted soil.
Background
Along with the accelerated urbanization process and industrial structure transformation in China, urban land resources are more scarce, land cost is continuously increased, and a large number of industrial enterprises originally located in a city center area are forced to be transferred to suburbs of cities; with the adjustment of industrial structure, the conventional falling-behind capacity enterprises and old factories face the shut-down or relocation situation. According to incomplete statistics, more than 10 thousands of enterprises in China need to be shut down or moved in recent years, and more than 2000 polluted enterprises which have been or are to be moved in recent years in the Yangtze delta region only. The enterprises are mostly engaged in the industries of electroplating, printing and dyeing, chemical fertilizers, pesticides and the like, and a large amount of heavy metals enter the soil due to the old equipment of the enterprises, the discharge of three industrial wastes, the running, the overflowing, the dripping, the leaking and the like in the production process, so that the site soil of the original industrial enterprises becomes the high-risk soil polluted by the heavy metals. More seriously, because of the large population density of China and the shortage of urban land resources, the polluted site soil can be rapidly re-developed and utilized to construct new plants, residential areas, commercial areas and the like, if the polluted site soil can not be effectively managed and risk-assessed, the polluted site soil becomes a chemical timed bomb, threatens the ecological environment safety of the reuse area, and also brings serious influence to the subsequent development and utilization.
The heavy metal contaminated soil can be reused after being repaired. The current common heavy metal contaminated soil remediation method mainly comprises the following steps: physical repair techniques, chemical repair techniques, phytoremediation techniques, and the like. The physical remediation technology comprises treatment technologies such as washing, excavation, transportation, landfill and the like aiming at heavy metal contaminated soil, can thoroughly remove heavy metal pollutants in a field, but is difficult to apply on a large scale due to potential secondary pollution, high treatment cost and limited landfill field quantity; the chemical remediation technology is mainly an in-situ solidification/stabilization method of heavy metals, and the form or structure of the heavy metals is changed by applying a stabilization/solidification treatment material, so that the purpose of reducing the mobility of the heavy metals is achieved, and the method is also the most widely applied remediation technology of the heavy metal contaminated soil at present; plant restoration, as a green restoration technology, can largely prevent the destruction of surface landscape and protect the original appearance of soil, however, the application of the technology is also limited by low efficiency, long restoration time and the vulnerability of plants to specific climatic conditions, and is difficult to be widely popularized. Therefore, chemical remediation of heavy metal contaminated soil by solidification/stabilization methods remains the most efficient and practical method at present. In the in-situ stabilization/solidification method of heavy metal, the high-temperature solidification treatment technology is widely applied in practice due to high solidification rate of heavy metal and stable and reliable effect. The high-temperature curing technology is mainly characterized in that heavy metal contaminated soil is fully mixed with auxiliary reaction materials such as coal gangue, fly ash and shale for reaction through a high-temperature sintering method, a spinel structure is formed after sintering, and heavy metals are firmly fixed in the stable spinel structure. Spinel is commonly denoted "AB 2 O 4 ", wherein A represents, for example, zn 2+ 、Cu 2+ 、Cd 2+ And Ni 2+ Divalent heavy metals, B being e.g. Cr 3+ And Al 3+ Iso-trivalentHeavy metals. Spinel has good structural stability, and can stably consolidate polluted heavy metal ions in a sintered body for a long time without generating secondary pollution even under the conditions of strong acid and strong alkali, so the spinel is widely considered as a promising method for repairing heavy metal polluted soil.
Soil is an important component of the ecosystem and is also the material foundation on which humans rely for survival. The recycling of the heavy metal contaminated soil after remediation is an effective means for relieving the serious shortage of soil resources in China. However, since the high-temperature curing technology is not a heavy metal pollution reduction technology in general, the total amount of heavy metals in the soil after remediation is not reduced per se. The core mechanism of the method is to stabilize the heavy metal by changing the morphological structure of the heavy metal, reduce the possibility of releasing the heavy metal into the environment and be a risk control technology. Therefore, after the heavy metal contaminated soil is repaired by the high-temperature curing technology, the long-term stability of the heavy metal and the possible ecological risks directly influence the acceptance and application range of the technology, and are also the problems which need to be considered when the repaired soil is reused. As a typical soil heavy metal pollution risk control technology, the high-temperature curing technology changes the occurrence form of heavy metals in soil, thereby achieving the purpose of reducing the migration and bioavailability of the heavy metals. However, since the polluted heavy metals are not completely eliminated, there still exists a certain question and risk if the heavy metals in the soil repaired by high-temperature curing are further released under the complicated practical application environmental conditions in the future, and a corresponding quantitative evaluation method is also very lacking.
For a long time, the benefit-related parties in the process of restoring the heavy metal contaminated soil pay more attention to the effect evaluation of the soil contaminated restoring technology, and the recycling direction of the restored soil and the possible ecological risks generated in the process of recycling under different environmental conditions are less concerned. The current common methods for evaluating the remediation effect of heavy metal contaminated soil comprise a TCLP toxicity leaching method for simulating landfill leachate, an SPLP leaching method for simulating acid rain leaching, an MEP multistage leaching method for simulating multiple acid rain erosion of a landfill and the like, which are provided by the United States Environmental Protection Agency (USEPA). The solid waste leaching toxicity leaching method proposed by the department of ecological environment in China comprises a horizontal oscillation method (HJ 557-2010), a sulfuric acid-nitric acid method (HJ/T299-2007), an acetic acid method (HJ/T300-2007) and the like. The method takes the leaching content of the heavy metal of the repaired soil under a certain specific pH condition (usually a strong acid condition) and within a specific reaction time period as an evaluation standard, and does not consider the influence of the morphological change characteristics of the heavy metal on the release of the heavy metal in the repaired soil. The commonly used leaching toxicity evaluation methods are mainly applied to the evaluation of the remediation effect of the heavy metal contaminated soil, but due to the limitations of the methods, the methods cannot completely simulate different situations of pollutant release to the environment after remediation in practice, and the long-term risks in the complex and variable environment are difficult to characterize. Particularly, different environments have complicated and variable pH conditions, and different pH conditions directly influence the release amount of heavy metals in the repaired soil, so that the ecological risks are different. If, for example, under acidic conditions, most heavy metals (Zn, cu, pb, etc.) exhibit stronger release characteristics compared to those under more alkaline conditions, it is clear that the actual ecological risks in the application scenarios of neutral and more alkaline environments are significantly overestimated if all post-remediation soil application scenarios are evaluated using only traditional solid waste leaching toxicity leaching methods, such as the nitric sulfate process (HJ/T299-2007) and the acetic acid process (HJ/T300-2007). Meanwhile, the high-temperature curing and repairing process of the heavy metal contaminated soil is accompanied by the change of the morphological structure of the heavy metal, the acid-soluble state of the heavy metal in the soil has the highest bioavailability and is the most harmful to the environment, and the acid-soluble state heavy metal in the contaminated soil can be effectively converted into the reduction-state, oxidation-state and residue-state heavy metal with high stability after being repaired by the high-temperature curing technology, so that the aim of effectively reducing the ecological risk of the heavy metal contaminated soil is fulfilled. However, the traditional toxic leaching method usually ignores the aspect of the morphological change of the heavy metal, so that the ecological risk of the soil under the neutral or alkaline condition after high-temperature curing and restoration is underestimated, the ecological risk of the soil without high-temperature curing and restoration under the neutral or alkaline condition is overestimated, and the uncertainty of the evaluation of the ecological risk of the soil after restoration is increased. The current prospect of safe recycling of the restored soil is directly influenced by the lack of the ecological risk assessment system of the restored soil, and the actual risk possibly generated by the restored soil under the complex pH conditions of different recycling situations can be more scientifically and reasonably evaluated by considering the leaching concentration and the acid dissolution state concentration of the restored soil at the same time. Therefore, development of an appropriate ecological risk assessment method for recycling heavy metal contaminated soil after remediation is urgently needed.
Disclosure of Invention
In order to overcome the defects of the existing heavy metal contaminated soil ecological risk assessment method, the first aspect of the invention aims to provide the heavy metal contaminated soil ecological risk assessment method.
The second aspect of the invention aims to provide an application of the method for evaluating the ecological risk of the heavy metal contaminated soil in the field of environmental detection.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a method for evaluating ecological risks of heavy metal contaminated soil, which comprises the following steps:
(1) Respectively placing the soil sample in extracting agents with different pH values to extract heavy metals in the soil sample, measuring the leaching concentration C1 of the heavy metals in the soil sample under the extracting agents with different pH values, and constructing a functional relation C1 (pH) between the leaching concentration of the heavy metals in the soil sample and the pH value of the extracting agent;
(2) Measuring the acid soluble state concentration C2 of the heavy metal in the soil sample leached in the step (1), and constructing a functional relation C2 (pH) between the acid soluble state concentration of the heavy metal in the soil sample and the pH value of the leaching agent;
(3) Calculating the heavy metal risk concentration C in the soil sample risk ：C risk ＝0.5×C1(pH)+0.5×C2(pH)；
(4) Determining the total concentration C3 of heavy metals in the soil sample;
(5) Calculating the ecological risk R of the heavy metal contaminated soil: r = C risk and/C is 3 multiplied by 100%, and the risk grade is divided according to the ecological risk R of the heavy metal polluted soil.
The leaching time in the step (1) is preferably more than or equal to 7 days; more preferably 7 to 14 days; most preferably 14 days.
The soil sample in the step (1) is preferably a repaired soil sample, and more preferably a soil sample repaired by a high-temperature curing technology.
The high-temperature curing technology comprises the following steps: mixing Cr 2 O 3 Mixing with heavy metal contaminated soil, adding auxiliary material, and sintering at 900-1200 deg.C for 2-5 hr.
The auxiliary materials include coal gangue and shale.
The particle size of the soil sample in step (1) is preferably <45um.
The heavy metal in step (1) is preferably at least one of copper, zinc, lead, cadmium, nickel and chromium.
The preparation method of the leaching agent in the step (1) refers to a solid waste leaching toxicity leaching method-sulfuric acid-nitric acid method (HJ/T299-2007), and specifically comprises the following steps: concentrated sulfuric acid and concentrated nitric acid are prepared into an initial solution according to the mass ratio of 2.
The pH gradient of the leaching agent in the step (1) is preferably more than or equal to 5; more preferably 6 or more.
The pH value of the leaching agent is preferably in the range of 2 to 12.
The leaching agent comprises at least two alkaline leaching agents and at least two acidic leaching agents.
The pH of the lixiviant may be: 2.4, 6, 8, 10; 3.5, 7, 9, 11; 2.4, 6, 8, 10, 12, etc.
The preferable mass-to-volume ratio (g: mL) of the soil sample and the leaching agent in the step (1) is 1 (15-25); more preferably 1 (15 to 20).
The leaching method in step (1) is preferably as follows: the soil sample and the leaching agent are shaken up and then turned over at the speed of 20-50 rpm.
The leaching concentration in step (1) is preferably determined by inductively coupled plasma emission spectroscopy.
The leaching concentration in the step (1) is preferably an average value of the heavy metal leaching concentrations on the 7 th and 14 th days.
The method for measuring the acid dissolution state concentration of the heavy metal in the step (2) is as follows: and (2) mixing the soil sample leached in the step (1) with acetic acid, oscillating, centrifuging to obtain a supernatant, and measuring the acid dissolution state concentration of the heavy metal.
And (2) cleaning and drying the extracted soil sample in the step (1) to obtain the extracted soil sample.
The shaking is preferably carried out at 23 to 28 ℃ for 15 to 20 hours.
The centrifugation condition is preferably 8000-10000 r/min for 15-25 minutes.
The acid dissolved state concentration is preferably determined by inductively coupled plasma emission spectroscopy.
The acid soluble state concentration in the step (2) is preferably the average value of the heavy metal acid soluble state concentrations of the soil samples leached for 7 days and 14 days in the step (1).
The total concentration of heavy metals in the soil sample in step (4) is preferably determined by: adding concentrated nitric acid, hydrofluoric acid and perchloric acid into a soil sample in sequence, digesting for 3-7 days at 150-200 ℃, and determining the total concentration of heavy metal after complete digestion.
The soil sample, the concentrated nitric acid, the hydrofluoric acid and the perchloric acid are preferably mixed according to a mass-volume ratio (g: mL: mL) of 1: (55-65): (55-65): (16 to 24).
The risk grade division standard in the step (5) is as follows: when R is less than or equal to 1%, the safety level is set; when R is more than 1% and less than or equal to 10%, the risk is low; when R is more than 10% and less than or equal to 30%, the risk grade is medium; when R is more than 30% and less than or equal to 50%, the risk is high; when R is more than or equal to 50 percent, the product is in an ultrahigh risk level.
The second aspect of the invention provides an application of the method for evaluating the ecological risk of the heavy metal contaminated soil in the field of environmental detection.
The invention has the beneficial effects that:
1. the method adopts two procedures of lixiviation by an lixiviant and acid-soluble extraction, comprehensively considers the lixiviation concentration of the soil and the acid-soluble concentration, and effectively overcomes the defect that the traditional heavy metal leaching toxicity leaching evaluation method only considers the lixiviation concentration of the heavy metal as an evaluation standard under a specific pH condition (usually a strong acid condition) and within a specific reaction time period. The method effectively avoids the possibility of underestimating the ecological risk of the restored soil under the neutral or slightly alkaline condition and overestimating the ecological risk of the unrepaired soil under the neutral or slightly alkaline condition, which are possibly generated by the traditional heavy metal leaching toxicity leaching evaluation method, and effectively reduces the uncertainty of the ecological risk evaluation of the restored soil.
2. According to the method, the risk concentration of the heavy metal in the repaired soil can be effectively calculated by constructing the functional relationship C1 (pH) between the leaching concentration of the heavy metal in the soil sample and the pH value of the leaching agent and the functional relationship C2 (pH) between the acid dissolved state concentration of the heavy metal in the soil sample and the pH value of the leaching agent, so that the ecological risk of the heavy metal in the repaired soil can be further quantitatively calculated. The method is based on the heavy metal solidification mechanism, comprehensively considers the leaching concentration and the acid dissolution state concentration of the soil, is stricter and more accurate compared with the traditional single toxicity leaching evaluation method, can effectively evaluate the possible ecological risks of the repaired soil under the complex pH environmental conditions of different practical recycling situations, and realizes the dynamic evaluation of the ecological risks of the repaired heavy metal polluted soil under different pH environmental conditions.
3. According to the method, the ecological risk possibly generated in the soil recycling process after restoration is obtained by a two-step method of sequentially obtaining the leaching concentration and the acid soluble concentration of the restored soil and calculating the ratio of the risk concentration obtained by combined analysis of the leaching concentration and the acid soluble concentration to the total concentration of the heavy metals, and the method is simple, clear in process, short in treatment period, high in efficiency, more scientific and reasonable, and more beneficial to ecological environment protection. The method has wide applicability, and can be suitable for quantitative evaluation of ecological risks of heavy metals in soil and unrepaired soil after remediation under different pH value environmental conditions in different regions of the country.
Drawings
FIG. 1 is a graph of the change in leaching concentration of Zn at different pH of leaching agents for soil after remediation and soil without remediation in example 1: wherein A is a leaching concentration change chart of Zn of the repaired soil under leaching agents with different pH values; and B is a graph of the leaching concentration change of Zn of the unrepaired soil under leaching agents with different pH values.
FIG. 2 is a graph of the change in acid dissolved state concentration of Zn at different pH of lixiviants for the soil after remediation and for the soil without remediation of example 1: wherein A is an acid soluble state concentration change diagram of Zn of the repaired soil under leaching agents with different pH values; and B is a graph of the change of the acid soluble state concentration of Zn of the unrepaired soil under leaching agents with different pH values.
FIG. 3 is a graph of the second order polynomial fit of the Zn leaching concentration and the acid dissolved state concentration, respectively, to the leaching agent pH in example 1: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Zn in the repaired soil and the pH value of the leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Zn in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Zn in the restored soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Zn in the unrepaired soil and the pH value of the leaching agent.
Fig. 4 is an ecological risk plot of Zn at different pH in the soil after remediation and in the soil without remediation of example 1.
FIG. 5 is a graph of the change in leaching concentration of Cu at different pH of lixiviants for soil after remediation and for unrepaired soil of example 2: wherein A is a leaching concentration change diagram of Cu of the repaired soil under leaching agents with different pH values; and B is a leaching concentration change graph of Cu of unrepaired soil under leaching agents with different pH values.
FIG. 6 is a graph of the change in the acid solution concentration of Cu at different pH leachants for soil after remediation and for unrepaired soil of example 2: wherein A is an acid soluble state concentration change diagram of Cu of the repaired soil under lixiviants with different pH values; and B is a graph of the change of the acid soluble state concentration of Cu of the unrepaired soil under different pH lixiviants.
FIG. 7 is a second order polynomial fit of the leaching concentration and acid soluble state concentration of Cu, respectively, to the pH of the leaching agent in example 2: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Cu in the repaired soil and the pH value of the leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Cu in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of acid soluble state concentration of Cu in the repaired soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cu in the unrepaired soil and the pH value of the leaching agent.
Fig. 8 is an ecological risk plot of Cu at different pH in the soil after remediation and in the soil without remediation in example 2.
FIG. 9 is a graph of the change in Cd leach concentrations at different pH leachants for soil after remediation and for non-remediated soil of example 3: wherein A is a leaching concentration change diagram of Cd of the repaired soil under leaching agents with different pH values; and B is a leaching concentration change diagram of Cd of unrepaired soil under leaching agents with different pH values.
FIG. 10 is a graph of the change in acid soluble concentration of Cd at different pH lixiviants for soil after remediation and for unrepaired soil from example 3: wherein A is an acid soluble state concentration change diagram of Cd of the restored soil under leaching agents with different pH values; and B is a graph of the change of the acid soluble state concentration of Cd of unrepaired soil under leaching agents with different pH values.
FIG. 11 is a graph of the quadratic polynomial fit of the concentrations of Cd and acid soluble state to the lixiviant pH in example 3, respectively: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Cd in the restored soil and the pH value of a leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Cd in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cd in the restored soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cd in the unrepaired soil and the pH value of the leaching agent.
Fig. 12 is an ecological risk plot of Cd at different pH in the remediated and unrepaired soils of example 3.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments and drawings.
The materials, reagents and the like used in the present examples are commercially available reagents and materials unless otherwise specified.
Example 1 ecological Risk assessment method for Zinc (Zn) -contaminated soil
This example uses a laboratory to simulate heavy metal contaminated soil. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil with the surface layer of 30cm is adopted, the pH value of the soil is 5.4, the concentration of Zn in the pollution-free soil is 27.7mg/kg, znO powder is manually added, and the Zn content in the pollution soil reaches 3413.7mg/kg after the pollution-free soil is fully ground; by adding Cr 2 O 3 Form ZnCr 2 O 4 High-temperature solidification reaction by way of spinel, znO and Cr 2 O 3 Zn according to the mol ratio: cr =1 was prepared as follows. And then adding coal gangue and shale into the mixed contaminated soil to serve as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample for 4 hours in a muffle furnace at 1000 ℃ to obtain a soil sample repaired by a high-temperature curing technology, and using the soil sample for carrying out ecological risk assessment of the next Zn-polluted soil repairing and recycling process. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the ecological risk calculation method of the unrepaired soil is the same as the soil calculation method after the high-temperature curing repair.
The ecological risk assessment method for the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) Grinding both the remediated and the non-remediated soil samples to particle sizes<45um fine powder, 6 different pH value gradients (pH =2, 4, 6, 8, 10 and 12) of leaching agents are prepared to leach the soil after high-temperature curing and repairing. The preparation of the leaching agent refers to a leaching method of the leaching toxicity of the solid wastes in China, namely a sulfuric acid-nitric acid method (HJ/T299-2007), concentrated sulfuric acid and concentrated nitric acid adopt a mode that the mass ratio is 2. Then 0.5g of powder sample of the repaired soil and the unrepaired soil sample are respectively poured into a centrifuge tube filled with 10mL of leaching agent, the centrifuge tube is fully shaken up and then is subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially taken at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process, and the sampling is carried out for 8 times totally. Finally, the repair soil is obtainedLixiviant samples of the soil and non-remediated soil samples were filtered over 0.25um cellulose membranes and the leaching concentration of Zn in the samples was determined by inductively coupled plasma emission spectroscopy (ICP-OES) and the results are shown in figure 1: for the unrepaired soil sample, the leaching concentration of Zn increased from day 1 until day 7 gradually stabilized, and the equilibrium leaching concentration gradually decreased with the increase in pH of the leaching agent, and the equilibrium leaching concentration C1 of Zn (average of heavy metal leaching concentrations at day 7 and day 14) decreased from 1315.8mg/kg at pH =2 to 3.94mg/kg (pH = 4), 1.87mg/kg (pH = 6), 2.18mg/kg (pH = 8), 1.01mg/kg (pH = 10), and 9.06mg/kg (pH = 12) after reaching stabilization; after remediation by the high temperature curing technique, zn in the artificially prepared heavy metal heavily contaminated soil sample was well fixed, and the equilibrium leaching concentration C1 of Zn was reduced from 5.98mg/kg at pH =2 to 1.95mg/kg (pH = 4), 1.14mg/kg (pH = 6), 0.96mg/kg (pH = 8), 1.12mg/kg (pH = 10) and 1.13mg/kg (pH = 12). Compared with the sample of unrepaired soil, the average leaching concentration of Zn in the sample of restored soil is reduced by 119-432 times. The leaching concentration of Zn in the repaired soil sample is far lower than the risk screening value (Zn) for repairing the soil of the Chinese heavy metal polluted residential area<500mg/kg, DB 43/T1165). The functional relationship between the equilibrium leaching concentration of Zn in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 3-A: the specific fitting formula is as follows: c1=0.11pH 2 -1.90pH+8.78，R 2 And the fitting effect is better than that of the fitting method of 0.91. Similarly, the function relationship between the equilibrium leaching concentration of Zn in the unrepaired soil and the pH value of the leaching agent can be established by quadratic polynomial fitting, and the result is shown in FIG. 3-B: the specific fitting formula is as follows: c1= -0.03pH 2 +0.54pH+0.01，R 2 And (5) the fitting effect is better than that of the fitting method of 0.66.
(2) After the leaching experiment under different pH values of the leaching agent in the first step is finished, the leached repaired soil sample and the leached unrepaired soil sample are respectively washed by deionized water and dried, and then are moved into a 50ml centrifugal tube for carrying out an acid dissolution state extraction experiment. The specific extraction process is as follows: adding the leached restored soil sample and the leached unrepaired soil sample into 20mL of 0.11mol/L acetic acid solution, and oscillating at 25 ℃ and room temperature for 18 hoursThen, the mixture was centrifuged at 9000r/min for 20 minutes, and the supernatant was transferred to a 10mL centrifugal tube and the acid-soluble concentration of Zn was measured by ICP-OES. The results are shown in FIG. 2: the average concentration C2 of the acid soluble state of Zn (average of the concentration of the heavy metal acid soluble state on days 7 and 14) in the soil sample after remediation was 2.216mg/kg (pH = 2), 2.60mg/kg (pH = 4), 3.08mg/kg (pH = 6), 3.35mg/kg (pH = 8), 4.53mg/kg (pH = 10), and 3.21mg/kg (pH = 12) in this order; the unrepaired soil samples were, in order, 1282.48mg/kg (pH = 2), 1409.65mg/kg (pH = 4), 1441.02mg/kg (pH = 6), 1422.92mg/kg (pH = 8), 1448.08mg/kg (pH = 10), and 1423.09mg/kg (pH = 12). Obviously, the acid solution concentration of the soil after the high temperature curing technology is smaller than that of the soil without being repaired. The functional relationship between the average concentration of the dissolved state of Zn acid in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 3-C: the specific fitting formula is: c2= -0.03pH 2 +0.54pH+0.01，R 2 And (5) the fitting effect is better than that of the fitting method of 0.66. Similarly, the average concentration of Zn acid in the unrepaired soil in solution as a function of the lixiviant pH can be established by quadratic polynomial fitting, and the results are shown in FIG. 3-D: the specific fitting formula is as follows: c2= -3.51pH 2 +60.53pH+1193.6，R 2 ＝0.75。
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Zn in the repaired soil and the average concentration C2 of the acid dissolution state of Zn in the repaired soil to obtain the ecological risk concentration C of Zn in the repaired soil risk The specific calculation formula is as follows: c risk ＝0.5×C1+0.5×C2。
(4) 0.05g of a repaired soil sample and an unrepaired soil sample which are ground and then sieved by a 100-mesh sieve (0.149 mm) are respectively weighed and placed in beakers, and concentrated nitric acid (HNO) is added 3 ) 3mL, hydrofluoric acid (HF) 3mL, perchloric acid (HClO) 4 ) 1mL, shake the bottom sample of the beaker and soak overnight. Placing on an electric hot plate next day, adding high temperature to 180 ℃ for digestion for 3 days until the soil sample is in a semisolid rolling state, completing digestion, cooling, fixing the volume to 50mL, shaking up, taking supernatant, and measuring the total concentration C3 of heavy metals in the repaired soil sample and the unrepaired soil sample by ICP-OES; the ecological risk concentration C obtained in the step (3) risk Substituting into the ecological risk assessment model of the heavy metal contaminated soil to calculate the ecological risk R of the heavy metal contaminated soil, wherein the specific calculation formula is as follows: r = C risk /C3×100％。
The results are shown in FIG. 4: obviously, the ecological risk of the repaired sample after the high-temperature curing treatment is far lower than that of the unrepaired sample; ecological risks for Zn in the unrepaired soil samples were 27.80%, 20.08%, 19.90%, 20.09%, 20.11%, and 19.77% in order from pH =2 to pH = 12; however, the ecological risks of Zn in soil samples after high temperature curing remediation were 0.12%, 0.07%, 0.06%, 0.08%, and 0.06%, respectively.
(5) And (3) carrying out risk rating on the calculated Zn ecological risk in the soil, wherein the risk rating is divided into five risk grades in total: when R is less than or equal to 1%, the safety level is set; when the R is more than 1% and less than or equal to 10%, the risk is low; when R is less than or equal to 30% and is 10%, the risk grade is medium; when the R is more than 30% and less than or equal to 50%, the risk is high grade; when R is more than or equal to 50 percent, the product is in an ultrahigh risk level. For the unrepaired soil samples, the samples were at a medium risk level when the pH was 2-12. However, the soil samples after high-temperature curing and repairing are all safe. The high-temperature curing repair technology obviously reduces the ecological risk of Zn-polluted soil, and the application of the method effectively avoids the possibility of underestimating the ecological risk of heavy metals in the repaired soil under neutral and slightly alkaline conditions, also avoids the possibility of overestimating the ecological risk of heavy metals in the unrepaired soil under the neutral and slightly alkaline conditions, and realizes the quantitative and accurate evaluation of the ecological risk of the heavy metal-polluted soil.
Example 2 ecological Risk assessment method for copper (Cu) -contaminated soil
This example uses a laboratory to simulate heavy metal contaminated soil. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil is 30cm in surface layer, the pH value of the soil is 5.6, the concentration of Cu in the pollution-free soil is 15.2mg/kg, cuO powder is manually added, and the Cu content in the pollution soil reaches 4656.4mg/kg after full grinding; by adding Cr 2 O 3 Form CuCr 2 O 4 High-temperature solidification reaction is carried out in a spinel mode, and CuO and Cr 2 O 3 The molar ratio of Cu: cr =1. And then adding coal gangue and shale into the mixed contaminated soil as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample for 4 hours at 1000 ℃ in a muffle furnace to obtain a soil sample repaired by a high-temperature curing technology, and using the soil sample for carrying out ecological risk assessment of the next Cu-polluted soil repairing and recycling process. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the ecological risk calculation method of the unrepaired soil is the same as the soil calculation method after the high-temperature curing repair.
The ecological risk assessment method for the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) Firstly, both a restored soil sample and an unrepaired soil sample are ground into particle sizes<45um fine powder, 6 different pH value gradients (pH =2, 4, 6, 8, 10 and 12) of leaching agents are prepared to leach the soil after high-temperature curing and repairing. The preparation of the leaching agent refers to a leaching method of the leaching toxicity of the solid wastes in China, namely a sulfuric acid-nitric acid method (HJ/T299-2007), concentrated sulfuric acid and concentrated nitric acid adopt a mode that the mass ratio is 2. Then 0.5g of powder sample of the repaired soil and the unrepaired soil sample are respectively poured into a centrifuge tube filled with 10mL of leaching agent, the centrifuge tube is fully shaken up and then is subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially taken at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process, and the sampling is carried out for 8 times totally. Finally, the leaching agent samples of the restored soil and the unrepaired soil were filtered through a 0.25um cellulose membrane, and the leaching concentration of Cu in the samples was measured by an inductively coupled plasma emission spectrometer (ICP-OES), with the results shown in fig. 5: for the unrepaired soil samples, the equilibrium leach concentration C1 of Cu (average of heavy metal leach concentrations at day 7 and 14) was reduced from 63.94mg/kg at pH =2 to 2.85mg/kg (pH = 4), 0.18mg/kg (pH = 6), 0.15mg/kg (pH = 8), 1.09mg/kg (pH = 10) and 0.68mg/kg (pH = 12); by high temperature curing techniquesAfter remediation, the artificially prepared heavy metal heavily contaminated soil samples were well immobilized with Cu, and the average leaching concentration of Cu was reduced from 26.40mg/kg at pH =2 to 0.23mg/kg (pH = 4), 0.25mg/kg (pH = 6), 0.21mg/kg (pH = 8), 0.23mg/kg (pH = 10) and 0.56mg/kg (pH = 12). The average leaching concentration of Cu in the remediated soil sample was significantly reduced compared to the unrepaired soil sample. The functional relationship between the equilibrium leaching concentration of Cu in the soil after remediation and the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in fig. 7-a: the specific fitting formula is as follows: c1=0.59pH 2 -10.13pH+39.65，R 2 And the fitting effect is better than that of the product with the value of = 0.79. Similarly, the equilibrium leaching concentration of Cu in the unrepaired soil as a function of the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 7-B: the specific fitting formula is: c1=1.42pH 2 -24.46pH+96.62，R 2 And the fitting effect is better than that of the fitting method, namely 0.81.
(2) After the leaching experiment under different pH values of the leaching agent in the first step is finished, the leached repaired soil sample and the leached unrepaired soil sample are respectively washed by deionized water and dried, and then are moved into a 50ml centrifugal tube for carrying out an acid dissolution state extraction experiment. The specific extraction process is as follows: the leached restored soil sample and the leached unrepaired soil sample are respectively ground to 100 meshes, 20mL of 0.11mol/L acetic acid solution is added, the mixture is shaken at the room temperature of 25 ℃ for 18 hours, then the mixture is centrifuged in a centrifuge with 9000r/min for 20 minutes, the supernatant is transferred to a 10mL centrifuge tube, and the acid dissolution state concentration of Cu is measured by ICP-OES. The results are shown in FIG. 6: the acid-soluble state average concentration C2 (average of heavy metal acid-soluble state concentrations on day 7 and 14) of Cu in the soil sample after remediation was 9.21mg/kg (pH = 2), 21.91mg/kg (pH = 4), 23.34mg/kg (pH = 6), 22.90mg/kg (pH = 8), 22.33mg/kg (pH = 10), and 32.23mg/kg (pH = 12) in this order; while the unrepaired soil samples were 347.13mg/kg (pH = 2), 238.74mg/kg (pH = 4), 251.64mg/kg (pH = 6), 225.22mg/kg (pH = 8), 224.18mg/kg (pH = 10), and 257.46mg/kg (pH = 12) in that order. Obviously, the acid solution concentration of the soil after the high-temperature curing technology is smaller than that of the soil without being repaired. The Cu acid in the repaired soil can be established through quadratic polynomial fittingThe mean concentration in solution as a function of the pH of the lixiviant is shown in FIG. 7-C: the specific fitting formula is as follows: c2= -0.10pH 2 +3.03pH+6.73，R 2 And the fitting effect is better than that of the product of which the mark is 0.72. Similarly, the functional relationship between the mean concentration of the dissolved state of Cu acid in the unrepaired soil and the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 7-D: the specific fitting formula is: c2=2.91pH 2 -48.19pH+418，R 2 ＝0.82。
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Cu in the repaired soil and the acid dissolution state average concentration C2 of Cu in the repaired soil to obtain the ecological risk concentration C of Cu in the repaired soil risk The specific calculation formula is as follows: c risk ＝0.5×C1+0.5×C2。
(4) 0.05g of a restored soil sample and an unrepaired soil sample which are ground and sieved by a 100-mesh sieve (0.149 mm) are respectively weighed and placed in a beaker, and concentrated nitric acid (HNO) is added 3 ) 3mL, hydrofluoric acid (HF) 3mL, perchloric acid (HClO) 4 ) 1mL, shake the bottom sample of the beaker and soak overnight. Placing on an electric heating plate on the next day, heating to 180 ℃ for digestion for 3 days, ending the digestion when the soil sample is in a semi-solid rolling state, cooling, fixing the volume to 50mL, and measuring the total concentration C3 of heavy metals in the repaired soil sample and the unrepaired soil sample by using ICP-OES; the ecological risk concentration C obtained in the step (3) risk Substituting into the heavy metal contaminated soil ecological risk assessment model to calculate the heavy metal contaminated soil ecological risk R, wherein the specific calculation formula is as follows: r = C risk /C3×100％。
The results are shown in FIG. 8: obviously, the ecological risk of the restored sample after the high-temperature curing treatment is far lower than that of the unrepaired sample; ecological risks for Cu in the unrepaired soil samples were 4.93%, 2.65%, 2.25%, 1.98%, 2.03%, and 2.22% in order from pH =2 to pH = 12; and the ecological risk of Cu in the soil sample after high-temperature curing restoration is reduced to 0.38%, 0.23%, 0.25%, 0.24% and 0.34%.
(5) And (3) carrying out risk rating on the calculated ecological risk of Cu in the soil, wherein the risk rating is divided into five risk grades in total: when R is less than or equal to 1%, the safety level is set; when 1% < R ≦ 10%, it is a low risk level; when R is less than or equal to 30% and is 10%, the risk grade is medium; when R is less than or equal to 50% by 30%, the risk grade is high; when R is more than or equal to 50%, the product is in an ultrahigh risk level. For the unrepaired soil samples, from pH =2 to pH =12, at a low risk level; and the soil samples after high-temperature curing and repairing are all in safety level. The high-temperature curing restoration technology obviously reduces the ecological risk of the Cu-polluted soil, and the application of the method effectively avoids the possibility of underestimating the ecological risk of the heavy metal of the restored soil under neutral and slightly alkaline conditions, also avoids the possibility of overestimating the ecological risk of the heavy metal of the unrepaired soil under the neutral and slightly alkaline conditions, and realizes the quantitative and accurate evaluation of the soil after the heavy metal restoration in the recycling process.
Example 3 ecological risk assessment method for cadmium (Cd) polluted soil
This example uses a laboratory to simulate heavy metal contaminated soil. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil with the surface layer of 30cm is adopted, the pH value of the soil is 5.6, the concentration of Cd in the pollution-free soil is 0.019mg/kg, cdO powder is added manually, and the Cd content in the pollution soil is 8412.6mg/kg after full grinding; by adding Cr 2 O 3 Form CdCr 2 O 4 High-temperature solidifying reaction of spinel, cdO and Cr 2 O 3 The method adopts a molar ratio of Cd: cr =1. And then adding coal gangue and shale into the mixed contaminated soil to serve as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample for 4 hours in a muffle furnace at 1000 ℃ to obtain a soil sample repaired by a high-temperature curing technology, and performing ecological risk assessment of the next Cd-polluted soil repairing and recycling process. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the ecological risk calculation method of the unrepaired soil is the same as the soil calculation method after high-temperature curing repair.
The ecological risk assessment method for the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) Firstly, both a restored soil sample and an unrepaired soil sample are ground into particle sizes<45um fine powder, 6 leaching agents with different pH value gradients (pH =2, 4, 6, 8, 10 and 12) are prepared for leaching the soil after high-temperature curing and repairing. The preparation of the leaching agent refers to a solid waste leaching toxicity leaching method in China, namely a sulfuric acid-nitric acid method (HJ/T299-2007), concentrated sulfuric acid and concentrated nitric acid are prepared into an initial solution in a mode that the mass ratio is 2. Then 0.5g of powder sample of the repaired soil and the unrepaired soil is respectively poured into a centrifuge tube filled with 10mL of leaching agent, the powder samples are fully shaken up and then are subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially sampled at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process for 8 times in total. Finally, the lixiviant samples of the restored soil and the unrepaired soil are filtered by a 0.25um cellulose membrane, and the equilibrium leaching concentration of Cd in the samples is measured by an inductively coupled plasma emission spectrometer (ICP-OES), and the result is shown in FIG. 9: for the unrepaired soil samples, the equilibrium leach concentration of Cd (average of heavy metal leach concentration at day 7 and 14) was reduced from 2245.81mg/kg at pH =2 to 14.09mg/kg (pH = 4), 9.26mg/kg (pH = 6), 7.88mg/kg (pH = 8), 4.44mg/kg (pH = 10) and 16.71mg/kg (pH = 12); after remediation by the high temperature solidification technique, cd in the heavily contaminated soil sample with artificially prepared heavy metals was well immobilized, and the equilibrium leaching concentration of Cd was reduced from 6.14mg/kg at pH =2 to 4.51mg/kg (pH = 4), 1.52mg/kg (pH = 6), 1.62mg/kg (pH = 8), 2.67mg/kg (pH = 10) and 1.26mg/kg (pH = 12). Compared with an unrepaired soil sample, the equilibrium leaching concentration of Cd in the restored soil sample is obviously reduced. The functional relationship between the equilibrium leaching concentration of Cd in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in FIG. 11-A: the specific fitting formula is as follows: c1=0.08pH 2 -1.51pH+8.82，R 2 And the fitting effect is better if the fitting rate is 0.83. Similarly, a functional relationship between equilibrium leaching concentration of Cd in unrepaired soil and pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 11-B: the specific fitting formula is: c1=50.11pH 2 -861.25pH+3371.5，R 2 And the fitting effect is better than that of the fitting method, namely 0.79.
(2) After the leaching experiment under different pH values of the leaching agent in the first step is finished, the leached repaired soil sample and the leached unrepaired soil sample are respectively washed by deionized water and dried, and then are moved into a 50ml centrifugal tube for carrying out an acid dissolution state extraction experiment. The specific extraction process is as follows: respectively grinding the leached restored soil sample and the leached unrepaired soil sample to 100 meshes, adding 20mL of 0.11mol/L acetic acid solution, oscillating at 25 ℃ for 18 hours at room temperature, then centrifuging for 20 minutes in a centrifugal machine at 9000r/min, transferring the supernatant into a 10mL centrifugal tube, and determining the acid dissolution state content of Cd by using ICP-OES. The results are shown in FIG. 10: the average concentration C2 of the dissolution state of Cd acid (average of the concentration of the dissolution state of heavy metal acid on day 7 and 14) in the soil sample after remediation was 7.60mg/kg (pH = 2), 9.53mg/kg (pH = 4), 15.21mg/kg (pH = 6), 15.58mg/kg (pH = 8), 15.40mg/kg (pH = 10), and 17.52mg/kg (pH = 12), in this order; the average concentration of acid soluble state of Cd in the unrepaired soil samples was 1959.50mg/kg (pH = 2), 2484.51mg/kg (pH = 4), 2459.48mg/kg (pH = 6), 2620.53mg/kg (pH = 8), 2418.96mg/kg (pH = 10) and 2397.42mg/kg (pH = 12) in that order. Obviously, the acid solution concentration of the soil after the high temperature curing technology is smaller than that of the soil without being repaired. The functional relationship between the average concentration of the dissolved state of Cd acid in the restored soil and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 11-C: the specific fitting formula is: c2= -pH 2 +2.37pH+2.96，R 2 And the fitting effect is better if the fitting rate is 0.78. Similarly, a functional relationship between the mean concentration of Cd acid in solution and the pH of the lixiviant in the unrepaired soil can be established by quadratic polynomial fitting, with the results shown in FIG. 11-D: the specific fitting formula is: c2= -15.35pH 2 +245.7pH+1601.5，R 2 And the fitting effect is better than that of the product of which the mark is 0.66.
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Cd in the restored soil and the acid dissolution state average concentration C2 of Cd in the restored soil to obtain the ecological risk concentration C of Cd in the restored soil risk The specific calculation formula is as follows: c risk ＝0.5×C1+0.5×C2。
(4) 0.05g of a restored soil sample and an unrepaired soil sample which are ground and sieved by a 100-mesh sieve (0.149 mm) are respectively weighed and placed in a beaker, and concentrated nitric acid (HNO) is added 3 ) 3mL, hydrofluoric acid (HF) 3mL, perchloric acid (HClO) 4 ) 1mL, shake the bottom sample of the beaker and soak overnight. Placing on an electric heating plate on the next day, heating to 180 ℃ for digestion for 3 days until the soil sample is in a semisolid rolling state, completing digestion, cooling, fixing the volume to 50mL, and measuring the total concentration C3 of heavy metals in the repaired soil sample and the unrepaired soil sample by ICP-OES; the ecological risk concentration C obtained in the step (3) risk Substituting into the heavy metal contaminated soil ecological risk assessment model to calculate the heavy metal contaminated soil ecological risk R, wherein the specific calculation formula is as follows: r = C risk /C3×100％。
The results are shown in FIG. 12: obviously, the environmental ecological risk of the repaired sample after the high-temperature curing treatment is far lower than that of the unrepaired sample; ecological risk for Cd in the unrepaired soil samples was 31.07%, 17.68%, 16.76%, 17.13%, 16.56%, and 16.08% in order from pH =2 to pH = 12; and the ecological risk of Cd in the soil sample after high-temperature curing restoration is reduced to 0.11%, 0.09%, 0.12%, 0.11%, 0.12% and 0.12%.
(5) And (3) carrying out risk rating on the ecological risk of Cd in the soil obtained by calculation, wherein the risk rating is divided into five risk grades: when R is less than or equal to 1%, the safety level is set; when the R is more than 1% and less than or equal to 10%, the risk is low; when R is less than or equal to 30% and is 10%, the risk grade is medium; when R is less than or equal to 50% by 30%, the risk grade is high; when R is more than or equal to 50%, the product is in an ultrahigh risk level. For the unrepaired soil samples, pH =2, is on a high risk scale, and pH values between 4 and 12 are on a medium risk scale. And the soil sample after high-temperature curing and repairing is in a safety level when the pH value is 2-12. The high-temperature curing restoration technology obviously reduces the ecological risk of Cd polluted soil, and the application of the method effectively avoids the possibility of underestimating the ecological risk of heavy metal of restored soil under neutral and slightly alkaline conditions, also avoids the possibility of overestimating the ecological risk of heavy metal of unrepaired soil under neutral and slightly alkaline conditions, and realizes the quantitative and accurate evaluation of the soil after heavy metal restoration in the recycling process.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (9)
1. The method for evaluating the ecological risk of the heavy metal contaminated soil is characterized by comprising the following steps:
(1) Respectively placing the soil sample into extracting agents with different pH values to extract heavy metals in the soil sample, measuring the leaching concentration C1 of the heavy metals in the soil sample under the extracting agents with different pH values, and constructing a functional relation C1 (pH) between the leaching concentration of the heavy metals in the soil sample and the pH value of the extracting agent;
(2) Measuring the acid soluble state concentration C2 of the heavy metal in the soil sample leached in the step (1), and constructing a functional relation C2 (pH) between the acid soluble state concentration of the heavy metal in the soil sample and the pH value of the leaching agent;
(3) Calculating the heavy metal risk concentration C in the soil sample risk ：C risk ＝0.5×C1(pH)+0.5×C2(pH)；
(4) Determining the total concentration C3 of heavy metals in the soil sample;
(5) Calculating the ecological risk R of the heavy metal polluted soil: r = C risk 3 multiplied by 100 percent of/C, and dividing the risk grade according to the ecological risk R of the heavy metal polluted soil;
the pH gradient of the leaching agent in the step (1) is more than or equal to 5;
the leaching agent comprises at least two alkaline leaching agents and at least two acidic leaching agents;
the heavy metal in the step (1) is at least one of copper, zinc, lead, cadmium, nickel and chromium.
2. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that:
the leaching time in the step (1) is more than or equal to 7 days.
3. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that:
the pH value range of the leaching agent is 2-12.
4. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that:
the soil sample and the leaching agent in the step (1) are in a mass-volume ratio of 1 (15-25).
5. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that: the method for measuring the acid soluble state concentration of the heavy metal in the step (2) comprises the following steps: and (2) mixing the soil sample leached in the step (1) with acid, oscillating, and measuring the acid dissolution state concentration of the heavy metal.
6. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that: the total concentration of heavy metals in the soil sample in the step (4) is determined by the following steps: adding concentrated nitric acid, hydrofluoric acid and perchloric acid into a soil sample in sequence, digesting for 3-7 days at 150-200 ℃, and determining the total concentration of heavy metal after complete digestion.
7. The ecological risk assessment method for heavy metal contaminated soil according to claim 1, characterized in that:
the risk grade division standard in the step (5) is as follows: when R is less than or equal to 1%, the safety level is set; when R is more than 1% and less than or equal to 10%, the risk is low; when R is more than 10% and less than or equal to 30%, the risk is in a middle risk grade; when R is more than 30% and less than or equal to 50%, the risk grade is high; when R is more than or equal to 50 percent, the product is in an ultrahigh risk level.
8. The ecological risk assessment method for heavy metal contaminated soil according to any one of claims 1 to 7, characterized in that:
the soil sample is a heavy metal contaminated soil sample repaired by a high-temperature curing technology.
9. The use of the method of ecological risk assessment of heavy metal contaminated soil of any one of claims 1 to 8 in the field of environmental monitoring.
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