Method for heavy metal pollution, risk evaluation and source analysis of waste factory soil

Abstract

The invention relates to a method for heavy metal pollution, risk evaluation and source analysis of waste factory soil. Comprising the steps of collection and treatment of soil sample sampling points, soil sample heavy metal determination, soil heavy metal pollution status evaluation, soil heavy metal potential ecological risk evaluation, soil heavy metal human health risk evaluation and soil heavy metal pollution source analysis. According to the method, the defects of one-sidedness, singleness and unconformity in a traditional evaluation method are overcome. The vertical pollution degree and risk level of the soil, the actual environment background value, multiple risk evaluation criteria and traceability analysis are comprehensively considered, an effective way is provided for waste factory soil environment quality evaluation, and the practicability, comprehensiveness and accuracy of the evaluation method are improved.

Description

Technical Field

[0001] The invention relates to a method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil, and belongs to the technical field of soil environment detection. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of heavy metal pollution in soil has become increasingly serious, posing a serious threat to the ecological environment and human health. Abandoned factories are important carriers of industrial production activities, and their soils often carry a large amount of heavy metal pollutants, posing a potential threat to the surrounding environment and residents' health. Therefore, risk assessment and source analysis of heavy metal pollution in abandoned factory soils are of great significance for formulating targeted governance measures and protecting the environment. However, many scholars use the content of heavy metals in the surface soil as the research basis for risk assessment and source analysis of heavy metals in soil. Since the vertical migration of heavy metals is related to the physical and chemical properties of the soil, the properties of the metal occurrence form, and the action of soil microorganisms, the content of heavy metals may increase and the pollution intensifies with the depth of the soil. Therefore, the content of heavy metals in the surface soil alone cannot fully reflect the overall pollution status and risk level of the study area; traditional evaluation methods mostly use the soil background values ​​of the local province as a reference for pollution indicators and risk indicators, rather than the measured values ​​of the control points in the study area. The actual background values ​​in the study area are affected by the geographical environment, climate, etc., so the soil background values ​​of the local province are difficult to represent the actual background values ​​in the study area. In addition, most studies use the potential ecological risk index as the basis for risk assessment, and no human health risk assessment research has been conducted. In summary, a comprehensive investigation of the status of heavy metal pollution in abandoned factory soils, an assessment of risk levels, and an in-depth analysis of pollution sources have important practical significance and theoretical value. However, the current evaluation method does not fully consider the status of vertical soil pollution, actual environmental background values, and human health risk assessment, and there are problems such as incomplete assessment and inaccurate results. Therefore, it is necessary to develop a more accurate and comprehensive method for soil heavy metal pollution, risk assessment, and source analysis. Summary of the invention

[0003] In order to solve the above problems, the present invention discloses a method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil, and its specific technical scheme is as follows:

[0004] A method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil, comprising the following steps:

[0005] Step 1: Arrangement of soil sampling points and collection and processing of soil samples: Arrange several sampling points in plots in the abandoned factory, and then arrange several sampling points in control soil plots. The sampling points in each plot are sampled at four sampling depths of 0-0.5m, 1.5-2m, 3-4m, and 5-6m. After removing debris from the sampled soil, dry it, grind and sieve the dried sample to use it as a soil sample;

[0006] Step 2: Determination of heavy metals in soil samples: Determine the mass content of heavy metals such as Cu, Pb, Zn, As, Ni, Hg, and Cd in soil samples;

[0007] Step 3: Evaluation of the current status of soil heavy metal pollution: The pollution load index and geoaccumulation index method were used to comprehensively evaluate the degree of soil multiple metal pollution at different depths;

[0008] Step 4: Comprehensive potential ecological risk assessment of soil heavy metals: The calculation formula for the comprehensive potential ecological risk index RI of soil heavy metals is:

[0009]

[0010] Where, Ci is the measured content of heavy metal i in soil; Bi is the measured average value of metal elements at the control point; Eri is the single factor potential ecological risk index; RI is the comprehensive potential ecological risk index of heavy metals in soil; Tri is the heavy metal toxicity coefficient, Zn = 1, Ni = Pb = Cu = 5, As = 10, Cd = 30, Hg = 40; when RI is less than 150, or Eri is less than 40, the soil is at a mild ecological risk, and the larger the RI and Eri values, the more serious the pollution;

[0011] Step 5: Human health risk assessment of heavy metals in soil: The formula for calculating the human health risk assessment index is:

[0012]

[0013]

[0014]

[0015] Wherein, ADDing is the daily hand-mouth contact intake, ADDinh is the daily respiratory inhalation intake, ADDderm is the daily skin contact intake, Ci is the measured value of heavy metal i in soil, and the meanings of other letters refer to the table below - Name;

[0016] Table-Name

[0017]

[0018] Step 6: Analysis of sources of soil heavy metal pollution:

[0019] 6.1: SPSS26.0 software was used to analyze soil elements using the Pearson correlation method. If there was a significant positive correlation between elements, it indicated that there was a high possibility of homology, and the accumulation index was relatively low and did not exceed the measured value of the control point. It was preliminarily judged that it was related to the output of local soil parent material. To explore its specific source, it was necessary to further combine the results of principal component analysis;

[0020] 6.2: The principal component analysis method PCA was used to analyze the sources of heavy metals in the soil of the study area. After testing, if KMO is greater than 0.5 and Bartlett's sphericity test is less than 0.05, then the principal component analysis method PCA is applicable. After dimensionality reduction, factors with eigenvalues ​​greater than 1 are extracted. If the element load rate on a factor is greater than or equal to 70%, and the accumulation index is greater than or equal to 0 and the coefficient of variation is greater than or equal to 0.3, then the factor is of human origin; if the element load rate on a factor is greater than or equal to 70%, and the accumulation index is less than 0 and the coefficient of variation is less than 0.3, then the factor is of natural origin.

[0021] Furthermore, the sampling points in the soil sample plots are arranged in the functional areas of the enterprise, distributed in the production area, temporary storage area for domestic waste, and paint workshop. The control points are arranged in the upstream area of ​​the groundwater flow of the plot, and the exposed soil without external disturbance is selected without involving industrial enterprises in the points and surrounding areas. On sunny days, RTK is used on-site to verify the points, and drilling is carried out by GP special drilling rigs. Before drilling each sampling hole during construction, the drilling rig, drilling tools, and tools are cleaned again to ensure the cleanliness of the tools. The construction workers wash their hands and change latex gloves to avoid mutual contamination between the drilling sampling holes. The drilling is completed within 2 days with a bamboo knife. For all sampling and soil sample collection work, 500 grams of soil samples were collected each time. To avoid the influence of disturbance, samples were taken one by one from shallow to deep. After the sampling container was sealed, the sample number and sampling date information were recorded on the label paper, which was affixed to the sampling container, and then placed in the sample box with frozen blue ice on site for temporary storage. After the sample entered the laboratory, it was air-dried to a dry matter mass content of 78%, then ground and passed through a 100-mesh sieve. According to the adopted detection method, the soil sample was weighed with a ten-thousandth balance for pretreatment. The pretreatment specifically included adding a strong acid with good oxidizing property (such as nitric acid, hydrochloric acid, hydrofluoric acid, etc.) to the soil sample, and decomposing the soil sample by heating.

[0022] Furthermore, the As and Hg contents in the heavy metals of the soil samples were determined by atomic fluorescence spectrophotometry;

[0023] The contents of Ni, Zn, and Cu were determined by flame atomic absorption spectrophotometry;

[0024] The contents of Cd and Pb were determined by graphite furnace atomic absorption spectrophotometry.

[0025] Furthermore, the calculation formula of the dye load index in step 3 is:

[0026]

[0027] Where PLI is the pollution load index, Ci is the measured value of the i-th heavy metal element at a certain sampling point, the unit of the measured value is mg / kg, Co is the measured average value of the metal element at the control point, and n is the type of heavy metal element;

[0028] When PLI is greater than 1, it means that the soil is polluted, and the larger the PLI value, the more serious the pollution.

[0029] Furthermore, the calculation formula of the cumulative index method in step 3 is:

[0030] Igeo=log 2 [C i / (K×C 0 )]

[0031] In the formula, Igeo is the geoaccumulation index, Ci is the measured value of the i-th heavy metal element at a certain sampling point, Co is the measured average value of the metal element at the control point, and K is the correction index, which is taken as 1.5;

[0032] When Igeo is greater than 0, it means that the soil is polluted, and the larger the Igeo value, the more serious the pollution.

[0033] Furthermore, the human health risk assessment index includes non-carcinogenic effects, and the calculation formula for non-carcinogenic risk is:

[0034]

[0035] In the formula, ADDi is the non-carcinogenic average daily exposure measurement of heavy metal i; HQ is the non-carcinogenic risk; HI represents the total non-carcinogenic effect of pollutants under all pathways, that is, the non-carcinogenic risk;

[0036] When HI is greater than 1, it means that heavy metals pose a non-carcinogenic risk to the surrounding population; when HI is lower than 1, it means that there is no obvious non-carcinogenic risk for the time being.

[0037] Furthermore, the human health risk assessment index includes carcinogenic effect, and the calculation formula of carcinogenic risk is:

[0038] TCR=∑CR=∑ADD i ×SF i

[0039] Where SF iis the slope factor of the carcinogenic risk of each heavy metal; CR is the carcinogenic effect; TCR represents the comprehensive carcinogenic effect of pollutants under all pathways, that is, the carcinogenic risk. When TCR is higher than 10 -4 , there is a risk of cancer.

[0040] Furthermore, the soil heavy metal risk assessment adopts the potential ecological risk index RI and human health risk assessment (carcinogenic risk TCR and non-carcinogenic risk HI), and comprehensively considers the metal content, actual measured values ​​of the control points, heavy metal toxicity coefficient Tri, carcinogenic risk TCR and non-carcinogenic risk HI levels.

[0041] The beneficial effects of the present invention are:

[0042] Traditional soil pollution degree assessment methods mostly use the soil background value of the province where the study area is located as the environmental background, which is different from the actual environmental background value of the study area. Therefore, the method of the present invention sets up soil control monitoring points in the external area of ​​the plot, and uses the actual measured values ​​of the control points as the background value of the study area.

[0043] Traditional soil evaluation methods mostly use the heavy metal content of a single surface layer of soil as a data set for evaluating the degree of pollution. However, the vertical migration of heavy metals is affected by multiple factors such as physical, chemical, and biological factors, and the content may decrease or increase with the depth of the soil. Therefore, the method of the present invention takes into account the vertical pollution of soil pollution, and samples are collected at four sampling depths of 0-0.5m, 1.5-2m, 3-4m, and 5-6m to evaluate the soil pollution characteristics and risk levels at different depths.

[0044] Traditional soil evaluation methods mostly use potential ecological risk assessment as a risk assessment indicator, and do not take human health risk assessment into consideration. Therefore, the method of the present invention not only uses potential ecological risk assessment as a risk assessment indicator, but also includes carcinogenic effects and non-carcinogenic effects in the calculation range. Metal content and control points are used to calculate the geoaccumulation index, and the pollution level can be seen in the geoaccumulation index classification; metal content and toxicity coefficient are used to calculate the potential ecological risk level, and the risk level can be seen in the classification index; the carcinogenic risk TCR calculation result is greater than 10 -4 There is a carcinogenic risk. The calculated result of the non-carcinogenic risk is greater than 1, indicating there is a non-carcinogenic risk.

[0045] The present invention overcomes the one-sidedness, singularity and incompatibility of traditional evaluation methods. It comprehensively considers the vertical soil pollution degree and risk level, the actual environmental background value, multiple risk assessment standards and traceability analysis, provides an effective way for the environmental quality evaluation of abandoned factory soil, and improves the practicality, comprehensiveness and accuracy of the evaluation method.

[0046] The significance of testing the element Ni is that the presence of Ni in the environment is usually related to specific pollution sources, such as industrial waste gas, automobile exhaust sedimentation, etc. Through testing, the source of Ni can be traced, the root cause of environmental pollution can be identified and controlled, and an important reference basis can be provided for environmental management departments; secondly, long-term exposure to heavy metal Ni is closely related to human health problems, such as skin allergies, respiratory irritation, and impaired lung function. By testing the Ni content in the soil of factory land, the risk of human exposure to Ni can be assessed, providing a basis for the formulation of health protection strategies. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0049] Combined with Figure 1 It can be seen that the method of heavy metal pollution, risk assessment and source analysis of the abandoned factory soil includes the collection and processing of soil samples, heavy metal determination of soil samples, evaluation of the current status of soil heavy metal pollution, potential ecological risk assessment of soil heavy metals, human health risk assessment and pollution source analysis steps.

[0050] 1. Collection and processing of soil samples. Sampling points are arranged according to the actual situation of the abandoned factory. A suitable number and location of control soil sampling points are set up inside the abandoned factory. Sampling is carried out at four sampling depths of 0-0.5m, 1.5-2m, 3-4m, and 5-6m. An appropriate amount of mixed soil samples are taken back in a cloth bag; the samples after removing debris are dried in an oven, and the oven temperature is maintained at 40°C; the dried samples are ground and passed through a nylon sieve. The detection method of the control soil sampling points is the same.

[0051] 2. Determination of heavy metals in soil samples. The contents of As and Hg were determined by atomic fluorescence spectrophotometry; the contents of Ni, Zn and Cu were determined by flame atomic absorption spectrophotometry; the contents of Cd and Pb were determined by graphite furnace atomic absorption spectrophotometry.

[0052] 3. Evaluation of the current status of soil heavy metal pollution. The pollution load index and geoaccumulation index method are used to evaluate the degree of soil pollution. The calculation formula of the pollution load index is:

[0053]

[0054] Where PLI is the pollution load index, Ci is the measured value of the i-th heavy metal at a certain sampling point, Co is the measured average value of the metal element at the control point, and n is the type of heavy metal element. When PLI is greater than 1, it means that the soil is polluted, and the larger the PLI value, the more serious the pollution (see Table 1 for the PLI classification standard).

[0055] Table 1 Pollution load index evaluation criteria

[0056]

[0057] The calculation formula of geoaccumulation index method is:

[0058] Igeo=log 2 [C i / (K×C 0 )]

[0059] Where Igeo is the geoaccumulation index, Ci is the measured value of the metal element, Co is the measured average value of the metal element at the control point, and K is the correction index, which is 1.5. When Igeo is greater than 0, it means that the soil is polluted. The larger the Igeo value, the more serious the pollution (see Table 2 for Igeo evaluation criteria).

[0060] Table 2 Evaluation criteria for geoaccumulation index

[0061]

[0062]

[0063] 4. Potential ecological risk assessment of heavy metals in soil. Calculation method of potential ecological risk assessment:

[0064]

[0065] Where Ci is the measured content of heavy metal i in soil; Bi is the measured average value of metal elements at the control point; Eri is the single factor potential ecological risk index; RI is the comprehensive potential ecological risk index; Tri is the heavy metal toxicity coefficient, Zn = 1, Ni = Pb = Cu = 5, As = 10, Cd = 30, Hg = 40. When RI is less than 150 and Eri is less than 40, the soil is at a mild ecological risk. The larger the RI and Eri values, the more serious the pollution. The potential ecological risk assessment standards are shown in Table 3.

[0066] Table 3 Potential ecological risk assessment standards

[0067]

[0068] 5. Environmental health risk assessment. Taking adults as receptors, the non-carcinogenic and carcinogenic risks of heavy metal pollution exposure in the study area were estimated through three exposure pathways: hand-to-mouth ingestion, skin contact, and respiratory inhalation. The parameters involved in the calculation process were selected from the USA-EPA model and the parameters recommended in relevant literature (see Tables 4 and 5).

[0069]

[0070]

[0071]

[0072] In the formula, ADD ing is the daily hand-mouth contact intake, ADD inh ADD is the daily intake of respiratory derm is the daily skin contact intake, C i is the measured value of heavy metal i in soil.

[0073] The non-cancer risk calculation formula is:

[0074]

[0075] In the formula, ADD i is the non-carcinogenic average daily exposure measurement of heavy metal i; HQ is the non-carcinogenic risk; HI represents the total non-carcinogenic effect of pollutants under all pathways. When HI is greater than 1, it means that heavy metals have a certain non-carcinogenic risk to the surrounding population; when HI is less than 1, it means that there is no obvious non-carcinogenic risk for the time being.

[0076] The formula for calculating cancer risk is:

[0077] TCR=∑CR=∑ADD i ×SF i

[0078] Where SF i is the slope factor of the carcinogenic risk of each heavy metal; CR is the carcinogenic effect; TCR represents the comprehensive carcinogenic effect of pollutants under all pathways. When TCR is higher than 10 -4 , there is a risk of cancer.

[0079] Table 4 Reference doses and slope factors of heavy metals in different exposure pathways

[0080]

[0081] Table 5 Model recommended parameters

[0082]

[0083] 6. Analysis of the sources of heavy metals in soil pollution. SPSS26.0 software was used to analyze soil elements using the Pearson correlation analysis method. If there is a significant positive correlation between elements, it means that there is a high possibility of homology, the accumulation index is relatively low, and it does not exceed the measured value of the control point. It can be preliminarily judged that it is related to the output of local soil parent material. To explore its specific source, it is necessary to further combine the results of principal component analysis. The principal component analysis (PCA) method was used to analyze the sources of heavy metals in the soil of the study area. After testing, KMO should be greater than 0.5 and Bartlett's sphericity test should be less than 0.05 to be applicable to the PCA method. After dimensionality reduction, factors with eigenvalues ​​greater than 1 were extracted. If the element has a high load rate on a factor, and the accumulation index and coefficient of variation are high at the same time, the factor may be of anthropogenic origin; if the element has a high load rate on a factor, and the accumulation index and coefficient of variation are small at the same time, the factor may be of natural origin.

[0084] A specific embodiment of the present invention is given below

[0085] The soil samples in this example were collected from an abandoned factory in Zhejiang Province. The descriptive analysis of the heavy metal content is shown in Table 6.

[0086] Table 6 Descriptive statistics of heavy metal content in the study area

[0087]

[0088] The overall coefficient of variation of Cu is 27%-59%, with high variation in the 0-0.5m and 3.0-4.0m soil layers, and moderate variation in the rest; the overall coefficient of variation of Ni is 17%-33%, which is moderate variation; the overall coefficient of variation of Zn and As is 16%-37%, with high variation in the 0-0.5m soil layer, and moderate variation in the rest; the overall coefficient of variation of Pb is 10-14%, which is mild variation; the overall coefficient of variation of Cd is 22%-104%, with the highest coefficient of variation reaching 104% in the 0-0.5m soil layer, and moderate variation in the rest; the overall coefficient of variation of Hg is 34%-44%, with high variation in the 3.0-4.0m soil layer, and moderate variation in the rest. In summary, compared with other soil layers, the coefficient of variation of heavy metals in the 0-0.5m and 3.0-4.0m soil layers is higher, and the degree of interference by human activities is greater.

[0089] The measured values ​​of the reference control points for the heavy metal pollution evaluation of the present invention are used as the environmental soil background values. The pollution load index evaluation results show (see Table 7) that the pollution load of soil point samples is mainly non-polluted and slightly polluted as a whole; and with the depth of the soil, the heavy metal pollution load trend gradually decreases, but the heavy metal pollution in the lower soil layer is slightly higher than that in the middle layer. The geoaccumulation index evaluation results show (see Table 8) that the Igeo levels of heavy metals at different depths at most sampling points are basically less than 0, indicating that the study area is in a relatively clean state as a whole, and As and Hg are slightly to moderately polluted. With the depth, the pollution accumulation indexes of Cu, Ni, Zn, and Cd show a downward trend, while the content of Hg and As decreases first and then increases with increasing depth, which is consistent with the change in the pollution load index.

[0090] Table 7 Evaluation results of pollution load index in the study area

[0091]

[0092] Table 8 Evaluation results of geoaccumulation index in the study area

[0093]

[0094] The potential ecological risk of soil heavy metals was evaluated using the potential ecological risk index, and the evaluation results are shown in Table 9. The potential ecological risk index showed a slight downward trend with soil depth, and was less than 150, indicating that the soil in the study area was in a mild risk state. The average values ​​of the single factor potential ecological risk index were ranked from large to small as Hg, Cd, As, Ni, Pb, Cu, and Zn; the ecological risks of other elements at different depths were all in a mild risk, and the single risk index of Hg in each layer exceeded 80, which was in a strong risk; the contribution rate of Hg and Cd to the comprehensive potential ecological risk index was particularly significant, reaching 60% and more than 20%. In summary, the potential ecological risk in the study area was relatively mild, and Hg and Cd were the main ecological risk contributing factors.

[0095] Table 9 Results of potential ecological risk assessment in the study area

[0096]

[0097] The non-carcinogenic effect and carcinogenic effect of the study area. The results are shown in Table 10. The non-carcinogenic risk level of the seven elements at all depths of the sampling points to adults is less than 1, and the non-carcinogenic risk level at the 95% confidence interval is also less than 1, indicating that the non-carcinogenic risk of the abandoned factory to adults is controllable and will not pose a non-carcinogenic threat for the time being. Among the seven elements, As has the highest non-carcinogenic risk, indicating that As is the main contributing factor to the non-carcinogenic risk. The carcinogenic risk level of the three elements at all soil depths of the sampling points to adults is less than 10 -4 , the carcinogenic level is less than 10 at 95% confidence interval -4, all below the safety threshold, indicating that the carcinogenic risk in this area is controllable; at different soil depths, the carcinogenic levels of the three elements are As>Cd>Pb from high to low, and the carcinogenic level of As is significantly higher than that of other elements.

[0098] Table 10 Results of non-carcinogenic and carcinogenic levels in the study area

[0099]

[0100] The results of the correlation between heavy metal contents in the study area are shown in Table 11.

[0101] Table 11 Correlation analysis results

[0102]

[0103] (Note: *The correlation is significant at the 0.05 level (two-tailed), **The correlation is significant at the 0.01 level (two-tailed).)

[0104] Cu, Ni, Zn, Pb, and Cd showed significant positive correlation, indicating a high possibility of homology; since the average values ​​of Cu, Ni, Zn, and Pb were lower than the local control point averages, and the accumulation index was also relatively low, it can be preliminarily determined that they were related to the local soil parent material output.

[0105] The results of principal component analysis of the study area are shown in Table 12.

[0106] Table 12 Principal component analysis results

[0107]

[0108] Cd, Cu, and Zn have high loads on factor 1, which are 0.935, 0.891, and 0.896, respectively, and the pollution accumulation index of these three soil elements is low. The correlation results show that these three elements show a strong positive correlation and have strong homology, which may be related to the natural output of soil parent material. Since the content does not exceed the measured value of the control point, it shows that it is less affected by human interference. Therefore, factor 1 can be regarded as affected by the natural geographical environment and is related to soil parent material, rock weathering, and the chemical process inside the earth. The contribution rate of Hg to factor 2 is significantly higher than that of other soil elements, up to 92.8%. The Hg content in this area is significantly higher than that of the control point, and the coefficient of variation at each depth is high, which is greatly affected by human activities; at the same time, the geoaccumulation index of Hg is significantly higher than that of other elements. Combined with Hg, it is usually considered to be related to industrial activities and comes from industrial activities such as pesticides, fertilizers, construction, medicine, and textiles. Therefore, factor 2 can be determined to be an industrial source.

[0109] The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil of the present invention has strong pollution assessment consistency and accuracy, comprehensive assessment, simple source analysis, and uses the heavy metal content of soil at different depths inside and outside the abandoned factory as basic data, and adopts pollution load index, geoaccumulation index, potential ecological risk assessment model, human health risk model, correlation analysis and principal component analysis to comprehensively evaluate and analyze the pollution source on the degree of soil pollution and risk level. The present invention overcomes the singleness, bias and one-sidedness of traditional methods, and proposes a more comprehensive, accurate, comprehensive and simple soil evaluation and pollution source tracing method, which provides data support and scientific basis for soil pollution prevention and control and ecological restoration after factory abandonment.

[0110] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil, characterized in that: The steps include: Step 1: Arrangement of soil sampling points and collection and processing of soil samples: Arrange several sampling points in plots in the abandoned factory, and then arrange several sampling points in control soil plots. The sampling points in each plot are sampled at four sampling depths of 0-0.5m, 1.5-2m, 3-4m, and 5-6m. After removing debris from the sampled soil, dry it, grind and sieve the dried sample to use it as a soil sample; Step 2: Determination of heavy metals in soil samples: Determine the mass content of heavy metals such as Cu, Pb, Zn, As, Ni, Hg, and Cd in soil samples; Step 3: Evaluation of the current status of soil heavy metal pollution: The pollution load index and geoaccumulation index method were used to comprehensively evaluate the degree of soil multiple metal pollution at different depths; Step 4: Comprehensive potential ecological risk assessment of soil heavy metals: The calculation formula for the comprehensive potential ecological risk index RI of soil heavy metals is: Where, Ci is the measured content of heavy metal i in soil; Bi is the measured average value of metal elements at the control point; Eri is the single factor potential ecological risk index; RI is the comprehensive potential ecological risk index of heavy metals in soil; Tri is the heavy metal toxicity coefficient, Zn = 1, Ni = Pb = Cu = 5, As = 10, Cd = 30, Hg = 40; when RI is less than 150, or Eri is less than 40, the soil is at a mild ecological risk, and the larger the RI and Eri values, the more serious the pollution; Step 5: Human health risk assessment of heavy metals in soil: The formula for calculating the human health risk assessment index is: Wherein, ADDing is the daily hand-mouth contact intake, ADDinh is the daily respiratory inhalation intake, ADDderm is the daily skin contact intake, Ci is the measured value of heavy metal i in soil, and the meanings of other letters refer to the table below - Name; Table-Name Step 6: Analysis of sources of soil heavy metal pollution: 6.1: SPSS26.0 software was used to analyze soil elements using the Pearson correlation method. If there was a significant positive correlation between elements, it indicated that there was a high possibility of homology, and the accumulation index was relatively low and did not exceed the measured value of the control point. It was preliminarily judged that it was related to the output of local soil parent material. To explore its specific source, it was necessary to further combine the results of principal component analysis; 6.2: The principal component analysis method PCA was used to analyze the sources of heavy metals in the soil of the study area. After testing, if KMO is greater than 0.5 and Bartlett's sphericity test is less than 0.05, then the principal component analysis method PCA is applicable. After dimensionality reduction, factors with eigenvalues ​​greater than 1 are extracted. If the element loading rate on a factor is greater than or equal to 70%, and the geoaccumulation index is greater than or equal to 0 and the coefficient of variation is greater than or equal to 0.3, then the factor is of anthropogenic origin; If the element loading rate on a factor is greater than or equal to 70%, and the cumulative index is less than 1 and the coefficient of variation is less than 0.3, then the factor is of natural origin.

2. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The sampling points in the soil sample plots are arranged in the functional areas of the enterprise, distributed in the production area, temporary storage area for domestic waste, and paint workshop. The control points are arranged in the upstream area of ​​the groundwater flow of the plot, and the exposed soil without external disturbance is selected without involving industrial enterprises in the points and surrounding areas. On sunny days, RTK is used on-site to verify the points. The drilling is carried out by GP special drilling rigs. Before drilling each sampling hole during construction, the drilling rig, drilling tools, and tools are cleaned again to ensure the cleanliness of the tools. The construction personnel wash their hands and change latex gloves to avoid mutual contamination between the drilling sampling holes. Within 2 days Bamboo knives were used to complete all point sampling and soil sample collection work. 500 grams of soil samples were collected each time. In order to avoid the influence of disturbance, samples were taken one by one from shallow to deep. After the sampling container was sealed, the sample number and sampling date information were recorded on the label paper, which was attached to the sampling container. It was then placed in a sample box with frozen blue ice on site for temporary storage. After the sample entered the laboratory, it was air-dried to a dry matter mass content of 78%, then ground and sieved through a 100-mesh sieve. According to the adopted detection method, the soil sample was weighed with a ten-thousandth balance for pretreatment. The pretreatment specifically involved adding strong acid to the soil sample and decomposing the soil sample by heating.

3. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The As and Hg contents in the heavy metals in the soil samples were determined by atomic fluorescence spectrophotometry; The contents of Ni, Zn, and Cu were determined by flame atomic absorption spectrophotometry; The contents of Cd and Pb were determined by graphite furnace atomic absorption spectrophotometry.

4. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The calculation formula of dye load index in step 3 is: Where PLI is the pollution load index, Ci is the measured value of the i-th heavy metal element at a certain sampling point, the unit of the measured value is mg / kg, Co is the measured average value of the metal element at the control point, and n is the type of heavy metal element; When PLI is greater than 1, it means that the soil is polluted, and the larger the PLI value, the more serious the pollution.

5. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The calculation formula of the accumulation index method in step 3 is: Igeo=log2[C i / (K×C0)] Where Igeo is the geoaccumulation index, Ci is the measured value of the i-th heavy metal element at a certain sampling point, Co is the measured average value of the metal element at the control point, and K is the correction index, which is taken as 1.5; When Igeo is greater than 0, it means that the soil is polluted, and the larger the Igeo value, the more serious the pollution.

6. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The human health risk assessment index includes non-carcinogenic effects, and the calculation formula for non-carcinogenic risk is: Where ADDi is the non-carcinogenic average daily exposure dose of heavy metal i; HQ is the non-carcinogenic risk; HI represents the total non-carcinogenic effect of pollutants under all pathways, that is, the non-carcinogenic risk; RDFi is the non-carcinogenic standard exposure measurement of heavy metal i under the exposure pathway defined by the US Environmental Protection Agency; When HI is greater than 1, it means that heavy metals pose a non-carcinogenic risk to the surrounding population; when HI is lower than 1, it means that there is no obvious non-carcinogenic risk for the time being.

7. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The human health risk assessment index includes carcinogenic effect, and the calculation formula of carcinogenic risk is: TCR=∑CR=∑ADD i ×SF i Where SF i is the slope factor of the carcinogenic risk of each heavy metal; CR is the carcinogenic effect; TCR represents the comprehensive carcinogenic effect of pollutants under all pathways, that is, the carcinogenic risk. When TCR is higher than 10 -4 , there is a risk of cancer.

8. The method for heavy metal pollution, risk assessment and source analysis of abandoned factory soil according to claim 1, characterized in that: The soil heavy metal risk assessment adopts the potential ecological risk index RI and human health risk assessment, and comprehensively considers the metal content, the measured value of the control point, the heavy metal toxicity coefficient Tri, the carcinogenic risk TCR and the non-carcinogenic risk HI level.

Images