Ecological effect assessment method based on pollution index method cluster and index covariance

Abstract

The invention discloses an ecological effect assessment method based on a pollution index method cluster and index covariance, and particularly relates to the field of pollutant ecological risk assessment. Comprising the following steps: S1, constructing a multi-element pollution index method cluster; s2, performing data standardization assignment on the multi-element pollution index in the step S1; s3, multi-element pollution index fluctuation accounting is carried out; s4, multi-element pollution index correlation degree accounting is carried out; s5, calculating an index weight value according to the volatility in the step S3 and the correlation degree in the step S4; and S6, calculating the risk value of the research area according to the standardized copy obtained in the step S2 and the weight value in the step S5. By adopting the technical scheme, the problems of single evaluation angle and non-uniform results of a traditional pollution index method are solved, and a technical support and a scientific means are provided for ecological risk evaluation of heavy metal pollution of different regional producing areas.

Description

Technical Field

[0001] The invention relates to the field of pollutant ecological risk assessment, and in particular to an ecological effect assessment method based on pollution index cluster and indicator covariance. Background Art

[0002] Soil health is closely related to human and environmental health. Healthy soil quality and production environment are essential to ensure global food security. Due to the strong impact of human activities on the production environment, the exposure rate of potentially toxic elements such as heavy metals has accelerated. According to the 2014 National Soil Pollution Survey Bulletin, the number of points where inorganic pollutants exceeded the standard accounted for 82.8% of all points that exceeded the standard. Therefore, the health of my country's soil is not optimistic, especially pollutants such as heavy metals pose a major threat to the soil ecological environment. In order to maintain soil health and agricultural product quality, it is necessary to reasonably assess the pollution risk of the soil in the production area before planting to avoid unnecessary economic losses.

[0003] Ecological Risk Assessment (ERA) is an assessment of the possibility of adverse ecological consequences after an ecosystem is subjected to one or more environmental stressors. Ecological risk assessment can quantify the degree of pollution and ecological harm of pollutants to the ecosystem, help environmental management departments better understand and grasp the ecological environment, and provide a strong basis for the formulation of scientific ecological environment control measures.

[0004] The pollution index method is the most commonly used ecological risk assessment method, including single factor pollution index (PI), geological accumulation index (Igeo), potential ecological risk index (Er), etc. The pollution index method provides a simple and convenient way to quickly grasp the ecological risk of heavy metal pollution in the study area, but using different pollution index methods in the same study area will produce different assessment results, which brings certain decision-making troubles to policy makers. In addition, different pollution index methods can only be evaluated from a certain perspective, making the results relatively one-sided. Therefore, some scholars began to explore comprehensive assessment methods, by assigning different weights to target risks, making the assessment results more objective and comprehensive.

[0005] Scientifically evaluating the ecological risks caused by heavy metals in soil and the risks of heavy metal pollution faced by soil is the basis for risk space analysis and analysis of influencing factors. As an important part of regional land resource planning, protection and management, ecological risk assessment is to quantitatively, objectively and accurately evaluate soil environmental quality through relevant theoretical methods, thereby providing a theoretical basis for formulating reasonable risk management strategies. Summary of the invention

[0006] The present invention aims to provide an ecological effect assessment method based on pollution index cluster and index covariance, which solves the problems of single assessment angle and inconsistent results in traditional pollution index method.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows: an ecological effect assessment method based on pollution index cluster and index covariance, comprising the following steps:

[0008] S1, construct multivariate pollution index method cluster;

[0009] S2, performing data standardization and value assignment on the multivariate pollution index of step S1;

[0010] S3, volatility accounting of multivariate pollution index;

[0011] S4, calculation of correlation of multiple pollution indices;

[0012] S5. Calculate the indicator weight value according to the volatility of step S3 and the correlation degree of step S4;

[0013] S6. Calculate the risk value of the study area based on the standardized replication obtained in step S2 and the weight value in step S5.

[0014] Furthermore, the construction method of step S1 is as follows: Calculate the single factor pollution index PI and geoaccumulation index I of different heavy metals in the soil at each point in the study area. geo and potential ecological hazard index E r .

[0015] Furthermore, the method of step S2 is as follows: construct a standardized value assignment strategy based on the grading standards for cultivated land soil environmental quality in the "Technical Guidelines for Delineation of Agricultural Land Soil Environmental Quality Categories (Trial)".

[0016] Furthermore, the volatility of the multivariate pollution index in step S3 is expressed in the form of standard deviation S. The larger the standard deviation, the higher the weight. The calculation formula is as follows:

[0017]

[0018] In the formula, R represents PI, I geo and E r The value assigned after standardization in step S2.

[0019] Furthermore, the correlation R between the multivariate pollution index indicators in step S4 is calculated using the Pearson correlation coefficient. The higher the correlation, the higher the correlation between the indicators, and the lower the weight of the indicators. The calculation formula of the Pearson correlation coefficient and the correlation R between the two indicators X and Y is as follows:

[0020]

[0021] Furthermore, the method of step 5 is as follows: the index information amount I is calculated based on the volatility S between the pollution indices calculated in step S3 and the correlation R in step S4, and the index weight value W is further calculated:

[0022] I jk =S jk ·A jk

[0023]

[0024] Furthermore, the method of step S6 is as follows:

[0025] According to the R obtained after standardization ijk And the weight value W jk Calculate the risk value using the following formula:

[0026]

[0027] Finally, based on the calculated risk value of the study area, the risk level of the study area is given, that is, when 1≤CompERA≤1.5, the corresponding level is low risk; when 1.5<CompERA<2.5, the corresponding level is medium risk; when 2.5≤CompERA≤3, the corresponding level is high risk.

[0028] Compared with the prior art, this solution has the following beneficial effects:

[0029] In order to take into account the differences between different evaluation methods in the process of ecological risk assessment, this scheme proposes a comprehensive soil pollution ecological risk assessment method (CompERA) based on the pollution index method cluster and indicator covariance. CompERA can determine the weights through certain mathematical methods according to the relationship between the original data. Its judgment results do not depend on people's subjective judgment and have a strong mathematical theoretical basis. CompERA mainly uses two objective indicators to calculate the weights: one is the volatility of the indicator, which indicates the size of the difference between the values ​​of the same indicator and different evaluation objects, expressed in the form of standard deviation. The larger the standard deviation, the greater the difference between the values ​​of the sample points; the second is the correlation between indicators. The correlation between indicators is based on the correlation between indicators. If there is a strong positive correlation between two indicators, it means that the correlation between the two indicators is high. The comprehensive ecological risk of the study area is determined by scientifically assigning weights to three typical evaluation methods: single factor pollution index, geoaccumulation index, and potential ecological hazard index. CompERA can comprehensively consider PI, I geo and E r The evaluation results solved the problem of inconsistent evaluation standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a flow chart of an ecological effect assessment method based on pollution index cluster and index covariance. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below through specific embodiments:

[0032] Example 1

[0033] like Figure 1 As shown, an ecological effect assessment method based on pollution index cluster and indicator covariance includes the following steps:

[0034] S1. Construct a multivariate pollution index method cluster. The construction method is as follows: Calculate the single factor pollution index PI and geoaccumulation index I of different heavy metals in the soil of each point in the study area. geo and potential ecological hazard index E r .

[0035] The single factor pollution index PI is a method to evaluate the accumulation level of pollutants based on pollutant limits or geochemical background values, which can evaluate the pollution degree of specific pollutants. The specific calculation formula is as follows:

[0036] PI=C / B

[0037] Where C represents the concentration of heavy metals in the soil (mg.kg -1 ), B is its corresponding geochemical background value.

[0038] Geoaccumulation Index I geo It is a quantitative pollution assessment method proposed by Muller. This method comprehensively considers the background value changes caused by human pollution, environmental geochemical background and natural diagenesis, and can study the pollution level of elements in soil and sediments. geo It is used to assess heavy metal pollution in soil by comparing current and pre-industrial concentrations. The specific calculation formula is as follows:

[0039] I geo =log2[C / (K×B)]

[0040] Where K is a correction exponent (=1.5), which takes into account that the background value may change due to diagenesis and is usually used to characterize sedimentary characteristics, rock geology and other influences.

[0041] Potential ecological damage index E r It represents the sensitivity of the biological community to the pollutant and illustrates the potential ecological risk resulting from it. This method is a method for assessing heavy metal pollution in soil or sediment from a sedimentological perspective. r The calculation formula is as follows:

[0042] Where, T r is the heavy metal toxicity coefficient (dimensionless), and the corresponding T of Cd, Pb, Cr, As and Hg r The values ​​are 30, 5, 2, 10 and 40 respectively. According to the classification standard defined by Hakanson, the potential ecological hazard index E r It can be divided into five levels: low risk, medium risk, medium-high risk, high risk and extremely high risk. The specific classification standards are shown in Table 1 below.

[0043] Table 1 Classification criteria of pollution index method

[0044]

[0045]

[0046] S2. Perform data standardization and assignment of the multivariate pollution index of step S1. The corresponding assignment method is as follows: To facilitate the subsequent soil control and pollution control, a standardized assignment strategy is constructed based on the grading standards for cultivated land soil environmental quality in the "Technical Guidelines for Delineation of Agricultural Land Soil Environmental Quality Categories (Trial)" (as shown in Table 2 below).

[0047] Table 2 Standardization process of typical ecological risk assessment methods

[0048]

[0049] According to the assignment strategy given in Table 2, PI, I geo and E r The results are standardized and assigned to eliminate the problem of inconsistent evaluation results and standards by different methods. After data standardization, the risk matrix of a single heavy metal pollutant can be obtained. ij )m*n, element r in the matrix ij Indicates the result of the jth evaluation method for the ith point. The values ​​1, 2, and 3 represent low risk, medium risk, and high risk, respectively.

[0050] S3. Calculation of volatility of multivariate pollution index. The volatility between multivariate pollution indexes is expressed in the form of standard deviation S. The larger the standard deviation, the higher the weight. The calculation formula is as follows:

[0051]

[0052] In the formula, R represents PI, I geo and E r The values ​​after standardization in step S2 are as follows: i, j and k represent the sampling point, heavy metal element and pollution index method respectively, and n represents the number of sampling points. ijkrepresents the standardized value of the kth pollution index assessment result of the jth heavy metal element at the i-th sampling point; Represents the mean of the standardized values ​​of the kth pollution index assessment results of the jth heavy metal element.

[0053] S4. Calculation of the correlation between the multiple pollution indexes. The correlation R between the multiple pollution index indicators is calculated using the Pearson correlation coefficient. The higher the correlation, the higher the correlation between the indicators, and the lower the weight of the indicators. The calculation formula of the Pearson correlation coefficient and the correlation R between the two indicators X and Y is as follows:

[0054]

[0055] In the formula, X and Y represent PI, I geo and E r Any two of the three evaluation indicators, in this study, need to calculate the Pearson correlation coefficient between the three evaluation indicators (a total of 3, including PI and I geo Pearson correlation coefficient, PI and E r The Pearson correlation coefficient between geo and E r Pearson correlation coefficient between .

[0056]

[0057] C jk is the kth Pearson correlation coefficient of the jth heavy metal element (3 in total, including PI and I geo Pearson correlation coefficient, PI and E r The Pearson correlation coefficient between geo and E r Therefore, A jk Corresponding to C jk The correlation degree of the jth heavy metal element represents the kth correlation degree (a total of 3, including PI and I geo Correlation between PI and E r The correlation between geo and E r between them).

[0058] S5. Calculate the index weight value according to the volatility of step S3 and the correlation of step S4. The calculation method is as follows: calculate the index information amount I according to the volatility S between the pollution indices calculated in step S3 and the correlation R of step S4, and further calculate the index weight value W:

[0059] I jk =S jk ·A jk

[0060]

[0061] S6. Calculate the risk value of the study area based on the standardized replication obtained in step S2 and the weight value in step S5. The calculation method is as follows: ijk And the weight value W jk Calculate the risk value using the following formula:

[0062]

[0063] Finally, based on the calculated risk value of the study area, the risk level of the study area is given, that is, when 1≤CompERA≤1.5, the corresponding level is low risk; when 1.5<CompERA<2.5, the corresponding level is medium risk; when 2.5≤CompERA≤3, the corresponding level is high risk.

[0064] Example 2

[0065] This example uses the method of Example 1 to evaluate the soil in the study area. The specific test results are as follows:

[0066] Based on PI, I geo and E r The percentage of points with different pollution levels of heavy metals in the study area and the risk assessment results are shown in Tables 3 and 4 (field sampling data in the middle and lower reaches of the Yangtze River in 2016). As can be seen from Tables 3 and 4, there are different degrees of differences in the pollution risk assessment results of different heavy metals using the three methods.

[0067] Table 3 Statistics of ecological risk assessment results of heavy metal pollution based on pollution index method

[0068]

[0069] Table 4 Results of ecological risk assessment of heavy metal pollution based on CompERA method

[0070]

[0071]

[0072] When the single factor pollution index (PI) was used for evaluation, the percentages of Cd points in the soil at the levels of no pollution, slight pollution, moderate pollution and severe pollution were 1.3%, 21.7%, 34.5% and 42.5% respectively; the corresponding percentages of Pb points were 26.6%, 61.2%, 10.7% and 1.5% respectively; the corresponding percentages of Cr points were 26.6%, 61.2%, 10.7% and 1.5% respectively; the corresponding percentages of As points were 76.0%, 23.4%, 0.6% and 0.0% respectively; the corresponding percentages of Hg points were 20.2%, 47.9%, 32.0% and 0.0% respectively. By calculating the mean PI values ​​of the points in the study area, it can be seen that the single factor pollution indexes of the five heavy metals Cd, Pb, Cr, As and Hg are 3.06, 1.34, 1.01, 0.81 and 1.60 respectively. When PI was used as the evaluation standard, Cd in the soil of the study area was at a severe pollution level, Pb, Cr and Hg were at a light pollution level, and As was at a non-pollution level.

[0073] When using the geoaccumulation index (I geo ) was used for evaluation, the percentages of Cd points in the four levels of no pollution, no-slight pollution, slight pollution and moderate pollution of the five heavy metals in the soil of the study area were 6.7%, 50.9%, 38.8% and 3.6% respectively; the corresponding percentages of Pb points were 71.2%, 27.3%, 1.5% and 0.0% respectively; the corresponding percentages of Cr points were 93.3%, 6.7%, 0.0% and 0.0% respectively; the corresponding percentages of As points were 94.4%, 5.6%, 0.0% and 0.0% respectively; the corresponding percentages of Hg points were 46.1%, 53.9%, 0.0% and 0.0% respectively. Calculate the I of the points in the study area geo The average geoaccumulation indexes of Cd, Pb, Cr, As and Hg are 0.90, -0.27, -0.66, -1.05 and -0.05, respectively. geo When the soil in the study area was used as the evaluation standard, Cd was at the level of no pollution to slight pollution, while Pb, Cr, As and Hg were all at the level of no pollution.

[0074] When the potential ecological hazard index (E r ) were evaluated, 4.3%, 43.6%, 45.1% and 7.1% of the Cd points were at low risk, medium risk, medium-high risk and high risk respectively; 20.2%, 47.9%, 32.0% and 0.0% of the Hg points were at low risk, medium risk, medium-high risk and high risk respectively; while 100% of the Pb, As and Cr points were at low risk. Furthermore, the E of Cd and Hg r The average values ​​were 91.84 and 64.01 respectively; the E rThe mean values ​​are 6.71, 2.02 and 8.06 respectively. r When the evaluation criteria were used, Cd in the soil of the study area was at a medium-high risk pollution level, while Hg was at a moderate risk level, and Pb, Cr, and As were all at a low risk level.

[0075] In summary, when different pollution assessment methods are used for the same pollutant in the same study area, the assessment results are very different, which can easily cause decision-making difficulties for policy makers. For example, for Cd, the ecological risk presented by the PI method is higher than that of the E r and I geo ; For Hg, use E r The ecological risk presented by the method is higher than that of PI and I geo .

[0076] with PI, I geo and E r Different from the single-perspective assessment method of the evaluation, the CompERA method based on the cluster of pollution index method and the covariance of indicators proposed in this study is a comprehensive ecological risk assessment method that integrates geological background, toxicity coefficient and human influence. The evaluation results of the CompERA method are as follows: the low, medium and high levels of Cd account for 6.7%, 50.9% and 42.5% respectively; Pb accounts for 71.2%, 28.8% and 0.0% respectively; Cr accounts for 93.3%, 6.7% and 0.0% respectively; As accounts for 94.4%, 5.6% and 0.0% respectively; Hg accounts for 46.1%, 53.9% and 0.0% respectively. The results show that the pollution risk of soil Cd in the study area is medium-high, the risk of Hg and Pb is medium-low, and Cr and As are low risk levels. It can be seen that the comprehensive ecological risk assessment (CompERA) method can give a clear and objective ecological pollution risk level for the study area.

[0077] The above are only embodiments of the present invention, and the common knowledge such as the known specific structures and / or characteristics in the scheme are not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. An ecological effect assessment method based on pollution index cluster and index covariance, characterized by: The steps include: S1, construct multivariate pollution index method cluster; S2, performing data standardization and value assignment on the multivariate pollution index of step S1; S3, volatility accounting of multivariate pollution index; S4, calculation of correlation of multiple pollution indices; S5. Calculate the indicator weight value according to the volatility of step S3 and the correlation degree of step S4; S6. Calculate the risk value of the study area based on the standardized replication obtained in step S2 and the weight value in step S5.

2. The ecological effect assessment method based on the pollution index cluster and index covariance according to claim 1 is characterized by: The construction method of step S1 is as follows: Calculate the single factor pollution index PI and geoaccumulation index I of different heavy metals in the soil at each point in the study area. geo and potential ecological hazard index E r .

3. The ecological effect assessment method based on the pollution index cluster and index covariance according to claim 1 is characterized by: The method of step S2 is as follows: construct a standardized value assignment strategy based on the grading standards for cultivated land soil environmental quality in the "Technical Guidelines for Delineation of Agricultural Land Soil Environmental Quality Categories (Trial)".

4. The ecological effect assessment method based on the pollution index cluster and index covariance according to claim 1 is characterized by: The volatility of the multivariate pollution index in step S3 is expressed in the form of standard deviation S. The larger the standard deviation, the higher the weight. The calculation formula is as follows: In the formula, R represents PI, I geo and E r The value assigned after standardization in step S2.

5. The ecological effect assessment method based on the pollution index cluster and index covariance according to claim 1 is characterized by: The correlation A between the multivariate pollution index indicators in step S4 is calculated using the Pearson correlation coefficient. The higher the correlation, the higher the correlation between the indicators, and the lower the weight of the indicators. The calculation formula of the Pearson correlation coefficient and the correlation A between the two indicators X and Y is as follows:

6. The ecological effect assessment method based on pollution index cluster and index covariance according to claim 1 is characterized by: The method of step 5 is as follows: the index information volume I is calculated based on the volatility S between the pollution indices calculated in step S3 and the correlation degree A in step S4, and the index weight value W is further calculated: I jk =S jk ·A jk 7. The ecological effect assessment method based on pollution index cluster and index covariance according to claim 1 is characterized by: The method of step S6 is as follows: According to the R obtained after standardization ijk And the weight value W jk Calculate the risk value using the following formula: Finally, based on the calculated risk value of the study area, the risk level of the study area is given, that is, when 1≤CompERA≤1.5, the corresponding level is low risk; when 1.5<CompERA<2.5, the corresponding level is medium risk; when 2.5≤CompERA≤3, the corresponding level is high risk.

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