Regional scale soil heavy metal pollution area identification method based on grids

Abstract

The invention discloses a grid-based regional scale soil heavy metal pollution area identification method. The method comprises the following steps: S1, generating a target region sampling grid and pre-distributed sampling points; s2, adjusting the position of a pre-distributed sampling point; s3, collecting surface soil samples and deep soil samples; s4, processing and combining the soil samples and measuring the heavy metal content; s5, evaluating soil heavy metal pollution of the target area; s6, generating a target area soil heavy metal pollution distribution rough graph; s7, determining a detailed investigation area, extracting a single-point sample, and determining the heavy metal content; s8, evaluating the heavy metal pollution of the soil in the detailed investigation area; and S9, generating a soil heavy metal pollution distribution detailed drawing of the target area. According to the method, the problems that the real condition of soil heavy metal pollution on the area is difficult to reflect when a single reference value is used for evaluation and the soil heavy metal pollution area is difficult to accurately identify through a spatial interpolation mode are solved, and the more accurate and accurate soil heavy metal pollution area can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of soil heavy metal pollution investigation and evaluation, and in particular to a grid-based regional scale soil heavy metal pollution area identification method. Background Art

[0002] Excessive accumulation of heavy metals in soil will not only cause serious damage to the ecological environment, but also threaten human health. Soil heavy metal pollution has become a hot issue that has attracted widespread attention around the world.

[0003] The existing identification of soil heavy metal pollution areas is mainly through the evaluation of the heavy metal pollution of each sample point, and then the spatial distribution of heavy metal pollution in the entire target area is obtained by spatial interpolation, and then the soil heavy metal pollution area is identified. Commonly used heavy metal pollution evaluation methods mainly include single factor pollution index method, Nemerow pollution index method, geoaccumulation index method, pollution load index method, etc. These evaluation methods all involve a very critical issue, that is, the selection of reference background values. Existing methods mostly use the soil heavy metal background value of a single region as the reference background value. However, the soil heavy metal background value in the region should actually be a range, not a single value. Moreover, the geological background between different regions is often different, and the soil heavy metal background value will also vary greatly. Therefore, this method of taking a single reference background value for evaluation is difficult to reflect the true soil heavy metal pollution situation at the regional scale. In addition, there are many ways of spatial interpolation, and the commonly used ones are inverse distance weighted method, Kriging method, radial basis function method, etc. The spatial distribution of heavy metal pollution obtained by using different interpolation methods is also different. Therefore, it is difficult to accurately identify soil heavy metal pollution areas by spatial interpolation. Summary of the invention

[0004] The purpose of the present invention is to provide a grid-based regional-scale soil heavy metal pollution area identification method to solve the problems proposed in the above background technology that taking a single reference value for evaluation is difficult to reflect the actual situation of soil heavy metal pollution in the region and that it is difficult to accurately identify soil heavy metal pollution areas through spatial interpolation.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for identifying soil heavy metal pollution areas at a regional scale based on a grid comprises the following steps:

[0007] S1. Generate the target area sampling grid and pre-distribute sampling points:

[0008] GIS software is used to generate surface sampling small grids, surface sampling large grids, deep sampling small grids and deep sampling large grids according to the scope of the target area; GIS software is used to generate a surface sampling pre-distribution point in the center of each surface sampling small grid, and a deep sampling pre-distribution point in the center of each deep sampling small grid;

[0009] S2. Adjust the position of the pre-arranged sampling points:

[0010] Adjust the location of pre-deployed sampling points according to the following principles: a) place them in areas where soil is easy to gather or develop; b) place them in the middle of the grid as much as possible; c) keep the sampling points as uniform as possible;

[0011] S3. Collect surface and deep soil samples:

[0012] Surface soil samples are collected in an "S" or "Z" shape at 3-5 locations within 100m of the pre-deployed sampling points, and deep soil samples are collected at a single point within 200m of the pre-deployed sampling points;

[0013] S4. Process and combine soil samples and determine heavy metal content:

[0014] The collected soil samples were dried and then passed through a 20-mesh nylon sieve; the four surface soil samples in each surface sampling grid were combined with equal weight to form a surface composite sample, and the four deep soil samples in each deep sampling grid were combined with equal weight to form a deep composite sample; the remaining uncombined single-point soil samples were bottled separately and stored in a warehouse; the heavy metal element content of the composite samples was determined;

[0015] S5. Evaluate the heavy metal pollution in the soil of the target area:

[0016] The heavy metal element content of the deep composite sample was used as the heavy metal element background value of the corresponding surface composite sample, and the heavy metal pollution of each surface composite sample was evaluated;

[0017] S6. Generate a general map of soil heavy metal pollution distribution in the target area:

[0018] GIS software is used to connect the heavy metal pollution evaluation results of each surface layer combination sample to the surface layer sampling grid to generate a general distribution map of soil heavy metal pollution in the target area;

[0019] S7. Determine the detailed investigation area and extract single-point samples to determine the heavy metal content:

[0020] According to the distribution map of heavy metal pollution in the target area, the surface sampling grids contaminated by heavy metals were selected as detailed investigation areas, and single-point surface soil samples and single-point deep soil samples in the detailed investigation areas were extracted to determine the content of heavy metal elements;

[0021] S8. Evaluate the heavy metal pollution in the soil of the detailed investigation area:

[0022] The heavy metal element content of the single-point deep soil sample was used as the heavy metal element background value of the corresponding single-point surface soil sample, and the heavy metal pollution of each single-point surface soil sample was evaluated;

[0023] S9. Generate a detailed map of soil heavy metal pollution distribution in the target area:

[0024] GIS software was used to connect the heavy metal pollution evaluation results of each single-point surface soil sample to the corresponding surface sampling grid to generate a detailed distribution map of heavy metal pollution in the target area.

[0025] Preferably, in step S1, the sizes of the surface sampling small grid, the surface sampling large grid, the deep sampling small grid and the deep sampling large grid are 1km×1km, 2km×2km, 2km×2km and 4km×4km respectively.

[0026] Preferably, in step S3, the sampling depth of surface soil samples is 0-20 cm, and the sampling depth of deep soil samples is below 150 cm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] By taking the content of heavy metal elements in deep soil as the background value of heavy metal elements in the corresponding surface soil, it can better reflect the actual soil heavy metal pollution situation compared with the traditional method of taking a single reference background value; by dividing the target area into regular grid units and sampling evenly, the content of heavy metal elements in the soil sample points in the grid is used to represent the content of heavy metal elements in the soil in the grid area, which can more accurately identify the soil heavy metal pollution area compared with the commonly used spatial interpolation method; by combining the samples for analysis, the soil heavy metal pollution overview of the entire target area can be quickly obtained while saving costs; by extracting single-point samples for detailed investigation, a more accurate soil heavy metal pollution area can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 It is a schematic diagram of the steps of the present invention;

[0031] Figure 2 is a schematic diagram of a sampling grid and pre-arranged sampling points according to an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of a sample assembly of an embodiment of the present invention;

[0033] Figure 4 It is a general map of the pollution distribution of the heavy metal element zinc (Zn) in the soil of the target area of ​​the embodiment of the present invention;

[0034] Figure 5 It is a detailed map of the pollution distribution of the heavy metal element zinc (Zn) in the soil of the target area of ​​the embodiment of the present invention. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, the present invention provides a grid-based regional scale soil heavy metal pollution area identification method, comprising the following steps:

[0038] S1. Generate the target area sampling grid and pre-distribute sampling points:

[0039] GIS software was used to generate surface sampling grids, surface sampling grids, deep sampling grids and deep sampling grids according to the scope of the target area, with sizes of 1km×1km, 2km×2km, 2km×2km and 4km×4km respectively; GIS software was used to generate one surface sampling pre-distribution point in the center of each surface sampling grid, and one deep sampling pre-distribution point in the center of each deep sampling grid. Figure 2 A schematic diagram of a sampling grid and pre-arranged sampling points according to an embodiment of the present invention is shown;

[0040] S2. Adjust the position of the pre-arranged sampling points:

[0041] Load the pre-deployed sampling points, sampling grids and remote sensing images in the GIS software, and adjust the positions of the pre-deployed sampling points according to the sampling grids and remote sensing images and refer to the following principles: a) deploy them in areas where soil is easy to gather or develop; b) deploy them in the middle of the grid as much as possible; c) maintain the uniformity of the sampling points as much as possible;

[0042] S3. Collect surface and deep soil samples:

[0043] Surface soil samples are collected at 3-5 locations within 100m of the pre-deployed sampling points in an "S" or "Z" shape with equal weight and multiple points, with a sampling depth of 0-20cm; deep soil samples are collected at a single point within 200m of the pre-deployed sampling points, with a sampling depth of 150cm-200cm;

[0044] S4. Process and combine soil samples and determine heavy metal content:

[0045] The collected soil samples were dried and then passed through a 20-mesh nylon sieve; Figure 3 As shown, the four surface soil samples in each surface sampling grid are combined into one surface composite sample with equal weight, and the four deep soil samples in each deep sampling grid are combined into one deep composite sample with equal weight; the remaining uncombined single-point soil samples are bottled separately and stored in a warehouse; the heavy metal element zinc (Zn) content of the composite sample is determined;

[0046] S5. Evaluate the heavy metal pollution in the soil of the target area:

[0047] The content of heavy metal element zinc (Zn) in deep composite samples was used as the background value of heavy metal element zinc (Zn) in the corresponding surface composite samples, and the heavy metal pollution of each surface composite sample was evaluated. The heavy metal pollution evaluation method used was the geoaccumulation index method (I geo ), and its calculation formula is:

[0048] I geo =log2[C / (1.5×B)]

[0049] Where, C is the measured content of heavy metal element zinc (Zn) in the surface soil; B is the measured content of heavy metal element zinc (Zn) in the deep soil; according to the geoaccumulation index (I geo ) The heavy metal pollution degree in soil is divided into 7 levels: no pollution (I geo ≤0), mild pollution (0 geo ≤1), moderate pollution (1 geo ≤2), moderate to severe pollution (2 geo ≤3), heavy to very heavy pollution (3 geo ≤4) and extremely severe pollution (4 geo ≤5);

[0050] S6. Generate a general map of soil heavy metal pollution distribution in the target area:

[0051] GIS software is used to connect the heavy metal pollution evaluation results of each surface layer combination sample to the surface layer sampling grid to generate a general distribution map of soil heavy metal pollution in the target area. Figure 4 A general diagram of the pollution distribution of the heavy metal element zinc (Zn) in the soil of the target area according to an embodiment of the present invention is shown;

[0052] S7. Determine the detailed investigation area and extract single-point samples to determine the heavy metal content:

[0053] According to the distribution map of heavy metal pollution in the target area, the surface sampling grids contaminated by heavy metals were selected as the detailed investigation area, and single-point surface soil samples and single-point deep soil samples in the detailed investigation area were extracted to determine the content of heavy metal element zinc (Zn); ​​​​​

[0054] S8. Evaluate the heavy metal pollution in the soil of the detailed investigation area:

[0055] The heavy metal element zinc (Zn) content of the single-point deep soil sample is used as the heavy metal element zinc (Zn) background value of the corresponding single-point surface soil sample, and the heavy metal pollution of each single-point surface soil sample is evaluated. The heavy metal pollution evaluation method is consistent with the evaluation method in step S5;

[0056] S9. Generate a detailed map of soil heavy metal pollution distribution in the target area:

[0057] GIS software is used to connect the heavy metal pollution evaluation results of each single-point surface soil sample to the corresponding surface sampling grid to generate a detailed distribution map of heavy metal pollution in the target area. Figure 5 A detailed map of the pollution distribution of the heavy metal element zinc (Zn) in the soil of the target area according to an embodiment of the present invention is shown.

[0058] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A grid-based regional-scale soil heavy metal pollution area identification method, characterized in that: The following steps are involved: S1. Generate the target area sampling grid and pre-distribute sampling points: GIS software is used to generate surface sampling small grids, surface sampling large grids, deep sampling small grids and deep sampling large grids according to the scope of the target area; GIS software is used to generate a surface sampling pre-distribution point in the center of each surface sampling small grid, and a deep sampling pre-distribution point in the center of each deep sampling small grid; S2. Adjust the position of the pre-arranged sampling points: Adjust the location of pre-deployed sampling points according to the following principles: a) place them in areas where soil is easy to gather or develop; b) place them in the middle of the grid as much as possible; c) keep the sampling points as uniform as possible; S3. Collect surface and deep soil samples: Surface soil samples are collected at 3-5 locations within 100m of the pre-deployed sampling points in an "S" or "Z" shape with equal weight at multiple points, and deep soil samples are collected at a single point within 200m of the pre-deployed sampling points; S4. Process and combine soil samples and determine heavy metal content: The collected soil samples were dried and then passed through a 20-mesh nylon sieve; the four surface soil samples in each surface sampling grid were combined with equal weight to form a surface composite sample, and the four deep soil samples in each deep sampling grid were combined with equal weight to form a deep composite sample; the remaining uncombined single-point soil samples were bottled separately and stored in a warehouse; the heavy metal element content of the composite samples was determined; S5. Evaluate the heavy metal pollution in the soil of the target area: The heavy metal element content of the deep composite sample was used as the heavy metal element background value of the corresponding surface composite sample, and the heavy metal pollution of each surface composite sample was evaluated; S6. Generate a general map of soil heavy metal pollution distribution in the target area: GIS software is used to connect the heavy metal pollution evaluation results of each surface layer combination sample to the surface layer sampling grid to generate a general distribution map of soil heavy metal pollution in the target area; S7. Determine the detailed investigation area and extract single-point samples to determine the heavy metal content: According to the distribution map of heavy metal pollution in the target area, the surface sampling grids contaminated by heavy metals were selected as detailed investigation areas, and single-point surface soil samples and single-point deep soil samples in the detailed investigation areas were extracted to determine the content of heavy metal elements; S8. Evaluate the heavy metal pollution in the soil of the detailed investigation area: The heavy metal element content of the single-point deep soil sample was used as the heavy metal element background value of the corresponding single-point surface soil sample, and the heavy metal pollution of each single-point surface soil sample was evaluated; S9. Generate a detailed map of soil heavy metal pollution distribution in the target area: GIS software was used to connect the heavy metal pollution evaluation results of each single-point surface soil sample to the corresponding surface sampling grid to generate a detailed distribution map of heavy metal pollution in the target area.

2. A method for identifying regional-scale soil heavy metal pollution areas based on a grid according to claim 1, characterized in that: In step S1, the sizes of the surface sampling small grid, the surface sampling large grid, the deep sampling small grid and the deep sampling large grid are 1km×1km, 2km×2km, 2km×2km and 4km×4km respectively.

3. The method for identifying regional-scale soil heavy metal pollution areas based on a grid according to claim 1 is characterized in that: In step S3, the sampling depth of surface soil samples is 0-20 cm, and the sampling depth of deep soil samples is below 150 cm.

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