Comprehensive environmental risk evaluation method based on tunnel hole slag heavy metal occurrence form and total amount

Abstract

The invention provides an environmental risk comprehensive evaluation method based on tunnel hole slag heavy metal occurrence form and total amount, and the method comprises the following steps: S1, tunnel hole slag pretreatment and sample preparation: carrying out representative sample collection on tunnel hole slag, and carrying out crushing, grinding and drying pretreatment operation to prepare a sample meeting detection requirements; s2, carrying out tunnel hole slag heavy metal occurrence form analysis and tunnel hole slag heavy metal total analysis, and carrying out corresponding tunnel hole slag heavy metal pollution bio-availability evaluation and tunnel hole slag heavy metal pollution total evaluation; and S3, based on the evaluation results of the bio-availability evaluation and the total evaluation of the tunnel hole slag heavy metal pollution, systematically analyzing the harmfulness of the tunnel hole slag heavy metal to complete the comprehensive evaluation of the tunnel hole slag heavy metal environmental risk. The method is wide in applicability, high in operability and reliable in evaluation effect aiming at the tunnel hole slag.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental pollution prevention and control, and particularly relates to a comprehensive environmental risk assessment method based on the occurrence forms and total amounts of heavy metals in tunnel muck. Background Art

[0002] With the improvement of infrastructure in various regions of China, a large amount of tunnel muck has been generated during road construction. Taking the Sichuan-Tibet Railway as an example, the total length of the railway is 1,838 km, and the proportion of tunnels and bridges in the total length is 81%. Roughly estimated, about 240 million cubic meters of tunnel muck will be generated during the construction of the entire Sichuan-Tibet Railway. According to statistics, the total stockpile of tunnel muck in China has exceeded 500 million tons. During the stockpiling process, tunnel muck may be affected by comprehensive environmental effects: oxidation, rainwater scouring, rainwater immersion, etc. If there are associated heavy metal elements in the tunnel muck, they may be leached out, and the leached pollutants will cause groundwater pollution and soil pollution. Therefore, analyzing the harmfulness of heavy metals in tunnel muck is a prerequisite for the safe stockpiling and subsequent utilization of muck.

[0003] At present, the output and stockpile of tunnel muck are relatively large, which has exerted great pressure on the environment. Affected by geology, some rocks may contain harmful elements such as heavy metals, and relevant studies have also found that the rocks and muck excavated from tunnels contain heavy metal elements such as Cu, Pb, Cd, and Zn. Since the harmfulness of heavy metals in the environment is relatively large, it is necessary to evaluate the harmfulness of heavy metals in tunnel muck before its treatment and disposal.

[0004] In addition, the harmfulness of heavy metals in the environment is mainly closely related to the heavy metal content and its bioavailability. In the existing technology, there are relatively many studies on the occurrence forms and harmfulness of heavy metals in soil, water, and the atmosphere. The total amount of heavy metals is mainly analyzed through digestion and detection, and the pollution degree of soil heavy metals is analyzed and judged by referring to the standard values of heavy metal pollutants in each medium; bioavailability is also an important index to characterize the harmfulness of heavy metals, which can directly reflect the ability of heavy metals to be absorbed, utilized, or cause toxic effects by organisms in the environment. It is characterized by various occurrence forms of heavy metals, and there are few studies and applications on the bioavailability related to the occurrence forms of heavy metals, and there is generally a lack of comprehensive and systematic characterization and analysis of the harmfulness of environmental heavy metals.

[0005] In view of the continuous increase in the subsequent stockpile of tunnel muck brought about by the development of relevant tunnel engineering construction work, it is urgent to comprehensively and effectively analyze the harmfulness of heavy metals in tunnel muck before its treatment and disposal. Summary of the Invention

[0006] In view of the above situation, the present invention provides a comprehensive environmental risk assessment method that combines the bioavailability assessment based on the occurrence forms of heavy metals and the environmental hazard assessment based on the total amount of heavy metals, which can achieve a comprehensive and systematic assessment of the heavy metal hazards of industrial solid wastes represented by tunnel muck.

[0007] Example 1, according to one aspect of the present invention, provides an integrated environmental risk assessment method for the occurrence forms and total amounts of heavy metals in tunnel muck, including the following steps:

[0008] Step S1. Pretreatment and sample preparation of tunnel muck: Collect representative samples of tunnel muck and perform pretreatment operations such as crushing, grinding, and drying to prepare samples that meet the detection requirements.

[0009] Step S2. Analyze the occurrence forms of heavy metals in tunnel muck and the total amounts of heavy metals in tunnel muck, and conduct corresponding bioavailability assessments of heavy metal pollution in tunnel muck and total amount assessments of heavy metal pollution in tunnel muck.

[0010] Step S3. Based on the evaluation results of the bioavailability assessment and total amount assessment of heavy metal pollution in tunnel muck, systematically analyze the hazards of heavy metals in tunnel muck to complete a comprehensive assessment of the environmental risks of heavy metals in tunnel muck.

[0011] In an optional implementation manner, the step S2 further includes:

[0012] Step S2a1. Analysis of the occurrence forms of heavy metals: Use the chemical sequential extraction method to analyze the pretreated tunnel muck samples to obtain the occurrence forms C n of various heavy metals in tunnel muck.

[0013] Step S2a2. Bioavailability assessment of heavy metal pollution: Based on the risk assessment coding method, analyze and evaluate the heavy metal occurrence form data obtained in step S2a1 based on the bioavailability of heavy metals to obtain the bioavailability assessment index N 1 of heavy metal pollution in tunnel muck.

[0014] In an optional implementation manner, the step S2 further includes:

[0015] Step S2b1. Total amount analysis of heavy metals: Use the total amount digestion method of heavy metals to perform total amount detection on the pretreated tunnel muck samples to obtain the total amount D 1 of heavy metals in tunnel muck.

[0016] Step S2b2. Total amount assessment of heavy metal pollution: Based on the single factor assessment method, analyze and evaluate the heavy metal total amount data obtained in step S2b1 based on the total amount of heavy metals to obtain the total amount assessment index N 2 of heavy metal pollution in tunnel muck.

[0017] In an alternative embodiment, in step S2a1, obtaining the occurrence forms C of heavy metals in tunnel muck n further includes first using the collected and stockpiled tunnel muck as the raw material for test analysis, further using equipment such as a jaw crusher and a ball mill to crush and grind the tunnel muck to prepare a test analysis sample, and then further using the sequential extraction procedure to analyze the occurrence forms of the muck, and dividing the occurrence forms of heavy metals into C 1 form, C 2 form, C 3 form, and C 4 form.

[0018] In an alternative embodiment, the extraction method for the C 1 form includes: taking 1.000 g of the tunnel muck sample and placing it in a 100 mL round-bottom centrifuge tube. Then add 40 mL of acetic acid with a concentration of 0.11 mol / L, cover the tube and place it on a shaker at room temperature for 16 - 20 hours. After shaking, place the centrifuge tube in a centrifuge, set the rotation speed to 4000 - 4500 r / min, and the centrifugation time to 20 - 30 minutes. Take the supernatant, add one drop of nitric acid (1+1), and prepare for measurement. Use ICP-MS to detect and analyze the sample to be measured, and obtain that the content of heavy metal C 1 in the form is C 10 (mg / kg). The remaining tunnel muck sample in the centrifuge tube is rinsed with 20 mL of deionized water and then centrifuged and washed again. After pouring out the supernatant, leave the tunnel muck for the next test.

[0019] In an alternative embodiment, the extraction method for the C 2 form includes: adding 40 mL of hydroxylamine hydrochloride solution with a concentration of 0.5 mol / L to the tunnel muck that has been rinsed with deionized water, placing it on a shaker at room temperature for 16 - 20 hours. After shaking, place the centrifuge tube in a centrifuge, set the rotation speed to 4000 - 4500 r / min, and the centrifugation time to 20 - 30 minutes. Take the supernatant, add one drop of nitric acid (1+1), and prepare for measurement. Use ICP-MS to detect and analyze the sample to be measured, and obtain that the content of heavy metal C 2 in the form is C 20 (mg / kg). The remaining tunnel muck sample in the centrifuge tube is rinsed with 20 mL of deionized water and then centrifuged again. After pouring out the supernatant, leave the tunnel muck for the next test.

[0020] In an alternative embodiment, the C 3The extraction method of the state includes: adding 10 mL of 8.8 mol / L hydrogen peroxide to the tunnel muck in the previous step, placing the centrifuge tube in a constant temperature water bath and continuously heating it at 85 °C for 1 - 1.5 hours, with intermittent oscillation. When the volume of the solution in the centrifuge tube is less than 2 mL, add another 10 mL of 8.8 mol / L hydrogen peroxide, and repeat the above operation. After the centrifuge tube cools, add 50 mL of ammonium acetate with a concentration of 1.0 mol / , and let it stand in a constant temperature water bath at room temperature for 16 - 20 hours. Then centrifuge again, take the supernatant and filter it through a filter membrane, add a drop of nitric acid (1 + 1) to prepare for testing, and use ICP-MS to detect and analyze the test solution to obtain that the content of heavy metal C 3 is C 30 (mg / kg). The remaining tunnel muck in the centrifuge tube is washed and centrifuged for the next test.

[0021] In an alternative embodiment, the extraction method of the C 4 state includes: vacuum drying the centrifuge tube containing the residue in the previous step at 40 °C until constant weight, grinding and sieving it through a 80 - 100 mesh sieve, and performing total digestion of heavy metals on the remaining tunnel muck residue as a solid sample. The digestion method is to add 60 - 80 mL of a mixed acid of hydrofluoric acid - hydrochloric acid - nitric acid - perchloric acid to the residue, and perform pyrolysis on an electric hot plate to obtain a test solution. Then use ICP-MS to detect and analyze the test solution to obtain that the content of heavy metal C 4 is C 40 (mg / kg).

[0022] In an alternative embodiment, in step S2a2, based on the analysis and evaluation of the heavy metal occurrence form data, the contents of each heavy metal occurrence form are C 10 、C 20 、C 30 、C 40 , and the biological availability evaluation index N of the heavy metal pollution in the tunnel muck is obtained 1 which further includes

[0023] N 1 = C 10 / (C 10 + C 20 + C 30 + C 40 ) * 100%;

[0024] And evaluate the soil pollution degree according to the evaluation criteria of the risk assessment coding method.

[0025] In an alternative embodiment, in step S2b1, the total amount D of heavy metals in the muck is obtained 1Further comprising adding 60 - 80 mL of a hydrofluoric acid - hydrochloric acid - nitric acid - perchloric acid mixed acid to the tunnel muck raw material, performing pyrolysis on an electric hot plate to obtain a test solution, and then using ICP - MS to detect and analyze the test solution to obtain the total amount D of heavy metals in the tunnel muck 1 (mg / kg).

[0026] In an alternative embodiment, in the step S2b2, the total evaluation index N of heavy metal pollution in the tunnel muck is obtained 2 Further comprising, N 2 = D 1 / D 0 (D 1 is the measured value of the total heavy metal content in mg / kg, D 0 is the evaluation standard value of heavy metals in mg / kg), and the degree of soil pollution is evaluated according to the evaluation criteria of the single - factor evaluation method.

[0027] In an alternative embodiment, in the step S3, according to the bio - availability evaluation index N of heavy metal pollution in the tunnel muck 1 and the total evaluation index N of heavy metal pollution in the tunnel muck 2 , the harmfulness of heavy metals in the muck is comprehensively and comprehensively evaluated by combining the two evaluation indexes.

[0028] Advantages of the present invention:

[0029] In view of the current insufficient status of the environmental protection risk assessment technology for the harmfulness of heavy metals in tunnel muck, the present invention has invented a new method for evaluating the harmfulness of heavy metals in muck, providing a comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel muck, which provides a reference basis for the safe disposal of tunnel muck storage and the safe utilization of tunnel muck as solid waste resources.

[0030] The method for evaluating the harmfulness of heavy metals in tunnel muck proposed by the present invention is a comprehensive environmental risk assessment method that combines the bio - availability evaluation based on the occurrence form of heavy metals and the environmental harmfulness evaluation based on the total amount of heavy metals, which can realize a comprehensive and systematic evaluation of the harmfulness of heavy metals in industrial solid waste represented by muck. The present invention simultaneously uses these two evaluation methods to conduct an environmental risk assessment on tunnel muck, making up for the deficiencies of single - method evaluation and providing a scientific and effective evaluation method for the harmfulness of tunnel muck.

[0031] The method of the present invention is applicable to industrial solid waste such as muck, with a wide range of applicability; this method combines two evaluation methods of the bio - availability and total amount of heavy metals to evaluate the harmfulness of tunnel muck, and the evaluation results are more comprehensive and reliable; at the same time, this method is simple to operate, easy to implement and promote. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0033] Figure 1 It is a schematic flow chart of a comprehensive environmental risk assessment method for the occurrence form and total amount of heavy metals in tunnel muck provided by the present invention. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in combination with specific embodiments and corresponding drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] According to one aspect of the present invention, a comprehensive environmental risk assessment method for the occurrence form and total amount of heavy metals in tunnel muck is provided. On the one hand, by using a method combining pretreatment and sequential chemical extraction, the occurrence forms Cn of heavy metals in tunnel muck are analyzed, and the biological availability evaluation index N of heavy metal pollution in tunnel muck is obtained by combining the risk assessment coding method. 1 On the other hand, the total amount D of heavy metals in the muck is obtained by a method combining pretreatment and total heavy metal detection. 1 , and the total amount evaluation index N of heavy metal pollution in tunnel muck is obtained by combining the single factor evaluation method. 2 ; Finally, combining the heavy metal pollution indexes N 1 and N 2 , comprehensively judge and analyze the environmental harmfulness of heavy metals.

[0036] Furthermore, in the process of obtaining the occurrence forms C n states of heavy metals in tunnel muck, first, the collected and stockpiled tunnel muck is used as the test analysis raw material, and equipment such as a jaw crusher and a ball mill is further used to crush and grind the tunnel muck to prepare a test analysis sample; further, the sequential chemical extraction method is used to analyze the occurrence form of the muck, and the heavy metal occurrence form is divided into C 1 state, C 2 state, C 3 state and C 4 state. Further, when using the sequential chemical extraction method to analyze the occurrence form of the muck, the heavy metal occurrence form is divided into C 1 state, C 2State, C 3 State and C 4 State.

[0037] The occurrence form C of the heavy metal described 1 -C 4 The extraction method is as follows:

[0038] C 1 Extraction method for the state: Take 1.000 g of tunnel muck sample and put it into a round-bottom centrifuge tube with a capacity of 100 mL. Then add 40 mL of acetic acid (HOAc) with a concentration of 0.11 mol / L, cover the lid and place it under room temperature conditions for oscillation (250 - 300 r / min to ensure that the mixture in the tube is in a suspended state), and the oscillation time is 16 - 20 hours. After the oscillation is completed, put the centrifuge tube into a centrifuge, set the rotation speed to 4000 - 4500 r / min, and the centrifugation time to 20 - 30 minutes. Take the supernatant (filtered through a 45 μm filter membrane), add one drop of nitric acid (1 + 1), prepare for testing, and use ICP-MS to detect and analyze the test solution to obtain the content of heavy metal C 1 The content of the state is C 10 (mg / kg). The remaining tunnel muck sample in the centrifuge tube is rinsed with 20 mL of deionized water and then centrifuged and cleaned again. After pouring out the supernatant, the tunnel muck is left for the next test.

[0039] C 2 Extraction method for the state: Add 40 mL of hydroxylamine hydrochloride solution with a concentration of 0.5 mol / L to the tunnel muck rinsed with deionized water, and place it in an oscillator under room temperature conditions for oscillation for 16 - 20 hours. After the oscillation is completed, put the centrifuge tube into a centrifuge, set the rotation speed to 4000 - 4500 r / min, and the centrifugation time to 20 - 30 minutes. Take the supernatant (filtered through a 45 μm filter membrane), add one drop of nitric acid (1 + 1), prepare for testing, and use ICP-MS to detect and analyze the test solution to obtain the content of heavy metal C 2 The content of the state is C 20 (mg / kg). The remaining tunnel muck sample in the centrifuge tube is rinsed with 20 mL of deionized water and then centrifuged again. After pouring out the supernatant, the tunnel muck is left for the next test.

[0040] C 3Extraction method of the state: Add 10 mL of 8.8 mol / L hydrogen peroxide to the tunnel muck after the above steps. Place the centrifuge tube in a constant temperature water bath and continuously heat it at 85 °C for 1 - 1.5 hours, with intermittent oscillation. When the volume of the solution in the centrifuge tube is less than 2 mL, add another 10 mL of 8.8 mol / L hydrogen peroxide and repeat the above operation. After the centrifuge tube cools, add 50 mL of ammonium acetate with a concentration of 1.0 mol / , and let it stand in a constant temperature water bath at room temperature for 16 - 20 hours. Then centrifuge again, take the supernatant and filter it through a filter membrane, add a drop of nitric acid (1 + 1) for testing, and use ICP-MS to detect and analyze the test solution to obtain the content of heavy metal C 3 The content of the state is C 30 (mg / kg). The remaining tunnel muck in the centrifuge tube is washed and centrifuged for the next experiment.

[0041] C 4 Extraction method of the state: Vacuum dry the centrifuge tube containing the residue in the previous step at 40 °C to constant weight, grind and sieve it (80 - 100 mesh), and perform total digestion of heavy metals on the residue of the remaining tunnel muck as a solid sample. The digestion method is to add 60 - 80 mL of a mixed acid of hydrofluoric acid - hydrochloric acid - nitric acid - perchloric acid to the residue, and perform pyrolysis on an electric hot plate to obtain a test solution. Then use ICP-MS to detect and analyze the test solution to obtain the content of heavy metal C 4 The content of the state is C 40 (mg / kg).

[0042] Furthermore, the biological availability evaluation index N1 of heavy metal pollution in tunnel muck is calculated according to the risk assessment coding method. The specific calculation formula is N 1 = C 10 / (C 10 + C 20 + C 30 + C 40 ) * 100%, and analyze the soil pollution degree according to the evaluation criteria of the risk assessment coding method in the following table.

[0043] Table 1 Evaluation criteria of the risk assessment coding method

[0044]

[0045] Furthermore, the method for detecting the total amount of heavy metals is specifically to add 60 - 80 mL of a mixed acid of hydrofluoric acid - hydrochloric acid - nitric acid - perchloric acid to the tunnel muck raw material, perform pyrolysis on an electric hot plate to obtain a test solution, and then use ICP-MS to detect and analyze the test solution to obtain the total amount of heavy metals D in the tunnel muck 1 (mg / kg).

[0046] Furthermore, the total amount evaluation index N of heavy metal pollution in tunnel muck 2 is calculated according to the single factor pollution index method, and the calculation formula is N 2 = D 1 / D 0 (D 1 is the measured value of the total amount of heavy metal in mg / kg, and D 0 is the evaluation standard value of heavy metal in mg / kg).

[0047] D 0 refers to the evaluation standard value in the Soil Quality Standard GB15618 - 2018. And the soil pollution degree is analyzed according to the evaluation standard of the single factor evaluation method in the following table.

[0048] Table 2 Evaluation Standards of Single Factor Evaluation Method

[0049]

[0050] Furthermore, the comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel muck is to comprehensively evaluate the harmfulness of heavy metals in muck by combining the biological availability evaluation index N 1 of heavy metal pollution in tunnel muck and the total amount evaluation index N 2 of heavy metal pollution in tunnel muck.

[0051] Example 2, according to another aspect of the present invention, in step S1, tunnel muck is collected, and equipment such as a jaw crusher and a ball mill are used to crush and grind the tunnel muck until the particle size of the muck is ground to below 80 - 100 mesh for subsequent test and detection analysis;

[0052] In step S2a1, the occurrence form of muck is analyzed by the chemical sequential extraction method, and the occurrence form of heavy metals is divided into C 1 state, C 2 state, C 3 state and C 4 state, and the content of various heavy metal occurrence forms in the tunnel muck is detected;

[0053] In step S2a2, combining the analysis results of the content of various heavy metal occurrence forms in the tunnel muck obtained in step S2a1, according to the risk assessment coding method, the biological availability evaluation index N 1 of heavy metal pollution in tunnel muck is calculated and analyzed;

[0054] In step S2b1, the tunnel muck raw material after pretreatment is subjected to total digestion of heavy metals, and the obtained digestion test solution is detected by ICP - MS.

[0055] In step S2b2, combined with the total metal content analysis results of the tunnel muck obtained in step S2b1, according to the single factor index method, the total amount evaluation index N of the heavy metal pollution of the tunnel muck is calculated and analyzed. 2 ;

[0056] In step S3, according to the biological availability evaluation index N1 of the heavy metal pollution of the tunnel muck and the total amount evaluation index N of the heavy metal pollution of the tunnel muck 2 , the harmfulness of the heavy metals in the muck is comprehensively evaluated by combining the two evaluation indexes.

[0057] Example 3, the present invention provides an environmental risk comprehensive evaluation method based on the occurrence form and total amount of heavy metals in tunnel muck, which includes tunnel muck pretreatment and sample preparation, tunnel muck heavy metal form analysis, tunnel muck heavy metal biological availability pollution evaluation, tunnel muck heavy metal total amount analysis, tunnel muck heavy metal total amount pollution evaluation, and finally forms an environmental risk comprehensive evaluation method based on the occurrence form and total amount of heavy metals in tunnel muck.

[0058] This example takes the muck of a certain railway tunnel as an example for analysis as follows:

[0059] For the tunnel muck pretreatment and sample preparation, first collect the tunnel muck, and use equipment such as a jaw crusher and a ball mill to crush and grind the tunnel muck until the particle size of the muck is ground to less than 100 mesh for subsequent test and detection analysis;

[0060] For the tunnel muck heavy metal form analysis, the chemical sequential extraction method is used to analyze the occurrence form of the muck, and the heavy metal occurrence form is divided into C 1 state, C 2 state, C 3 state and C 4 state. The extraction method of the heavy metal occurrence form C 1 -C 4 is as follows:

[0061] C 1 state extraction method: Take 1.000 g of tunnel muck sample and put it into a 100 mL round-bottom centrifuge tube. Then add 40 mL of acetic acid (HOAc) with a concentration of 0.11 mol / L, cover the lid and place it under temperature conditions, shake (250 r / min to ensure that the mixture in the tube is in a suspended state), and the shaking time is 16 hours. After shaking, put the centrifuge tube into a centrifuge, set the rotation speed to 4000 r / min, and the centrifugation time to 20 minutes. Take the supernatant (filtered through a 45 μm filter membrane), add one drop of nitric acid (1+1), prepare for measurement, and use ICP-MS to detect and analyze the test solution to obtain that the content of heavy metal C 1 in the state is C 10(mg / kg). The remaining tunnel muck samples in the centrifuge tube were rinsed with 20 mL of deionized water and then centrifuged and washed again. After pouring off the supernatant, the tunnel muck was left for the next test.

[0062] C 2 Extraction method for the C state: Add 40 mL of hydroxylamine hydrochloride solution with a concentration of 0.5 mol / L to the tunnel muck rinsed with deionized water, and place it in an oscillator at room temperature for 16 hours. After the oscillation, put the centrifuge tube into a centrifuge, set the rotation speed to 4000 r / min, and the centrifugation time to 20 minutes. Take the supernatant (filtered through a 45 μm filter membrane), add one drop of nitric acid (1+1), and prepare for measurement. The content of heavy metal C in the test solution was obtained by detecting and analyzing the test solution using ICP-MS. 2 The content of the C state is C 20 (mg / kg). The remaining tunnel muck samples in the centrifuge tube were rinsed with 20 mL of deionized water and then centrifuged again. After pouring off the supernatant, the tunnel muck was left for the next test.

[0063] C 3 Extraction method for the C state: Add 10 mL of 8.8 mol / L hydrogen peroxide to the muck after the above steps, and place the centrifuge tube in a constant temperature water bath and continuously heat it at 85 °C for 1 hour. When the volume of the solution in the centrifuge tube is less than 2 mL, add another 10 mL of 8.8 mol / L hydrogen peroxide and repeat the above operation. After the centrifuge tube cools, add 50 mL of ammonium acetate with a concentration of 1.0 mol / L and let it stand in a constant temperature water bath at room temperature for 16 hours. Then centrifuge again, take the supernatant and filter it through a filter membrane, add one drop of nitric acid (1+1) and prepare for measurement. The content of heavy metal C in the test solution was obtained by detecting and analyzing the test solution using ICP-MS. 3 The content of the C state is C 30 (mg / kg). The remaining tunnel muck in the centrifuge tube was used for the next test after cleaning and centrifugation.

[0064] C 4 Extraction method for the C state: Vacuum dry the centrifuge tube containing the residue from the previous step at 40 °C to constant weight, grind and sieve it (80-100 mesh), and perform total digestion of heavy metals on the remaining tunnel muck residue as a solid sample. The digestion method is to add 60 mL of a mixed acid of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid to the residue and perform pyrolysis on an electric hot plate to obtain the test solution, and then the content of heavy metal C in the test solution was obtained by detecting and analyzing the test solution using ICP-MS. 4 The content of the C state is C 40 (mg / kg).

[0065] The evaluation of the bioavailability pollution of heavy metals in tunnel muck is to combine the analysis results of the occurrence forms and contents of various heavy metals in the tunnel muck obtained in step S2, and it is found that only two heavy metals, Zn and Pb, are contained in the tunnel muck, and no other heavy metals are detected. The occurrence forms and contents are shown in Table 3.

[0066] The bioavailability evaluation index N of heavy metal pollution in tunnel muck is calculated according to the risk assessment coding method 1 , and the specific calculation formula is N 1 = C 10 / (C 10 + C 20 + C 30 + C 40 ). According to the evaluation criteria of the risk assessment coding method, it is calculated that the N 1 values of the railway muck are all less than 1%. Referring to the evaluation criteria of the risk assessment coding method in Table 1 above, it is obtained that the heavy metals in the muck have no environmental risk.

[0067] Table 3 Occurrence forms and contents of various heavy metals in a certain railway muck

[0068]

[0069] The total analysis of heavy metals in the tunnel muck is to perform total digestion of heavy metals on the pretreated tunnel muck raw materials. Specifically, 60 mL of a mixed acid of hydrofluoric acid - hydrochloric acid - nitric acid - perchloric acid is added to the tunnel muck raw materials, and pyrolysis is carried out on an electric hot plate to obtain a test solution. Then, ICP - MS is used to detect and analyze the test solution to obtain the total amount D 1 (mg / kg) of heavy metals in the tunnel muck. Through detection and analysis, it is obtained that the total contents of only two heavy metals, Zn and Pb, in the tunnel muck are respectively, and no other heavy metals are detected.

[0070] Table 4 Occurrence forms and contents of various heavy metals in a certain railway muck

[0071]

[0072] The total pollution evaluation of heavy metals in the tunnel muck, combined with the total metal analysis results of the tunnel muck obtained in step S5, is to calculate and analyze the total pollution evaluation index N 2 of heavy metal pollution in the tunnel muck according to the single - factor pollution index method; the calculation formula is N 2 = D 1 / D 0 (D 1 is the measured value of the total amount of heavy metals in mg / kg, and D 0 is the evaluation standard value of heavy metals in mg / kg).

[0073] As shown in Table 4 calculated and analyzed according to the detection results, the N 2 values of heavy metals Zn and Pb are 0.186 and 0.079 respectively, both of which are less than 1, not exceeding the standard, and not causing pollution to the soil environment.

[0074] The comprehensive environmental risk assessment method of the present invention based on the occurrence form and total amount of heavy metals in tunnel muck is based on the biological availability evaluation index N 1 of heavy metal pollution in tunnel muck of this railway and the total amount evaluation index N 2 of heavy metal pollution in tunnel muck of this railway. By combining the two evaluation indexes, a comprehensive evaluation of the harmfulness of heavy metals in muck can be carried out. It can be seen that there is no environmental risk for the heavy metals in this muck, and further treatment and disposal can be continued.

[0075] The method described in the present invention is applicable to industrial solid wastes such as muck, with a wide range of applicability; this method combines two evaluation methods of biological availability and total amount of heavy metals to evaluate the harmfulness of tunnel muck, and the evaluation results are more comprehensive and reliable, and it is also convenient to operate.

[0076] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag, characterized in that: The steps include: Step S1. Tunnel slag pretreatment and sample preparation: representative samples of tunnel slag are collected, and pretreatment operations such as crushing, grinding, and drying are performed to prepare samples that meet the testing requirements; Step S2. Performing a tunnel slag heavy metal occurrence morphology analysis and a tunnel slag heavy metal total quantity analysis, and performing a corresponding tunnel slag heavy metal pollution bioavailability evaluation and a tunnel slag heavy metal pollution total quantity evaluation, The step S2 further comprises: step S2a1, heavy metal occurrence form analysis, using a chemical continuous extraction method to analyze the pre-treated tunnel slag sample to obtain the occurrence form C of each heavy metal in the tunnel slag. n state; Step S2a2, heavy metal pollution bioavailability evaluation, based on the risk assessment coding method, the heavy metal occurrence form data obtained in step S2a1 is analyzed and evaluated based on the heavy metal bioavailability, and the tunnel slag heavy metal pollution bioavailability evaluation index N1 is obtained; Step S2b1, heavy metal total amount analysis, using heavy metal total amount digestion method to perform full amount detection on the pre-treated tunnel slag sample to obtain the total amount of heavy metals in the slag D1; Step S2b2, full evaluation of heavy metal pollution, analyzing and evaluating the full amount of heavy metal data obtained in step S2b1 based on the total amount of heavy metals according to the single factor evaluation method, and obtaining the full evaluation index N2 of heavy metal pollution of tunnel slag; Step S3. Based on the evaluation results of the bioavailability evaluation and the full evaluation of heavy metal pollution in tunnel slag, a systematic analysis is conducted on the harmfulness of heavy metals in tunnel slag to complete a comprehensive evaluation of the environmental risks of heavy metals in tunnel slag.

2. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 1, characterized in that: In the step S2a1, the occurrence forms C of each heavy metal in the tunnel slag are obtained. n The state further includes, first using the collected and stored tunnel slag as the test analysis raw material, further using jaw crusher, ball mill and other equipment to crush and grind the tunnel slag to prepare test analysis samples, and then further using chemical continuous extraction method to analyze the storage form of the slag, and the heavy metal storage forms are divided into C1 state, C2 state, C3 state and C4 state.

3. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 2, characterized in that: The extraction method of the C1 state comprises: taking 1.000g of a tunnel slag sample, placing it in a round-bottom centrifuge tube with a capacity of 100mL, then adding 40mL of acetic acid with a concentration of 0.11mol / L, covering it with a lid and placing it under room temperature for oscillation, and the oscillation time is 16-20 hours. After the oscillation is completed, the centrifuge tube is placed in a centrifuge, the speed is set to 4000-4500r / min, the centrifugation time is 20-30 minutes, the supernatant is taken, a drop of nitric acid (1+1) is added, and the supernatant is prepared for testing, and the test solution is tested and analyzed by ICP-MS to obtain the content of heavy metal C1 state. 10 (mg / kg), the remaining tunnel slag sample in the centrifuge tube was rinsed with 20mL of deionized water and then centrifuged again for cleaning, the supernatant was discarded and the tunnel slag was left for the next test.

4. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 3, characterized in that: The C2 state extraction method comprises: adding 40 mL of 0.5 mol / L hydroxylamine hydrochloride solution to the tunnel slag washed with deionized water, placing the slag in an oscillator at room temperature for 16-20 hours, placing the centrifuge tube in a centrifuge after the oscillation, setting the speed to 4000-4500 r / min, and the centrifugation time to 20-30 minutes, taking the supernatant, adding a drop of nitric acid (1+1), preparing for testing, and using ICP-MS to detect and analyze the test solution to obtain the content of heavy metal C2 state is C 20 (mg / kg), the remaining tunnel slag sample in the centrifuge tube was rinsed with 20mL of deionized water and centrifuged again, the supernatant was poured out and the tunnel slag was left for the next test.

5. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 4, characterized in that: The extraction method of the C3 state comprises: adding 10 mL of 8.8 mol / L hydrogen peroxide to the tunnel slag in the previous step, placing a centrifuge tube in a constant temperature water bath and continuously heating at 85° C. for 1-1.5 hours, intermittently shaking, and when the volume of the solution in the centrifuge tube is less than 2 mL, adding 10 mL of 8.8 mol / L hydrogen peroxide, repeating the above operation, adding 50 mL of 1.0 mol / ammonium acetate after the centrifuge tube is cooled, and standing in a constant temperature water bath at room temperature for 16-20 hours, and then centrifuging again, taking the supernatant and filtering it through a filter membrane, adding a drop of nitric acid (1+1) to prepare for testing, and using ICP-MS to detect and analyze the test solution to obtain the content of the heavy metal C3 state of C 30 (mg / kg), and the remaining tunnel slag in the centrifuge tube was used for the next test after washing and centrifugation.

6. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 5, characterized in that: The extraction method of C4 state comprises: vacuum drying the centrifuge tube containing the residue in the previous step at 40° C. to constant weight, grinding and sieving with 80-100 mesh, and performing full-quantity digestion of heavy metals on the remaining tunnel slag residue according to the solid sample, wherein the digestion method is to add 60-80 mL of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid to the residue, perform pyrolysis on a hot plate to obtain a test solution, and then use ICP-MS to detect and analyze the test solution to obtain a heavy metal C4 state content of C 40 (mg / kg).

7. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 1, characterized in that: In the step S2a2, the content of each heavy metal occurrence form is obtained by analyzing and evaluating the heavy metal occurrence form data. 10 , C 20 , C 30 , C 40 The bio-effectiveness evaluation index N1 of heavy metal pollution in tunnel slag further includes: N1=C 10 / (C 10 +C 20 +C 30 +C 40 )*100%; The degree of soil pollution is evaluated according to the evaluation criteria of the risk assessment coding method.

8. The method for comprehensive environmental risk assessment based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 1, characterized in that: In the step S2b1, obtaining the total amount of heavy metals D1 in the tunnel slag further includes adding 60-80 mL of a hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid to the tunnel slag raw material, performing pyrolysis on an electric hot plate to obtain a test liquid, and then using ICP-MS to detect and analyze the test liquid to obtain the total amount of heavy metals D1 (mg / kg) in the tunnel slag.

9. A comprehensive environmental risk assessment method based on the occurrence form and total amount of heavy metals in tunnel slag as claimed in claim 1, characterized in that: In the step S2b2, the total evaluation index N2 of heavy metal pollution in tunnel slag is obtained, further including N2=D1 / D0 (D1 is the total measured value of heavy metals in mg / kg, D0 is the heavy metal evaluation standard value in mg / kg), and the degree of soil pollution is evaluated according to the evaluation standard of the single factor evaluation method.

10. The method for comprehensive environmental risk assessment based on the occurrence form and total amount of heavy metals in tunnel slag according to claim 1, characterized in that: In the step S3, based on the bioeffectiveness evaluation index N1 of heavy metal pollution in tunnel slag and the total evaluation index N2 of heavy metal pollution in tunnel slag, a comprehensive and integrated evaluation is performed on the hazard of heavy metal pollution in tunnel slag by combining the two evaluation indexes.

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