Rapid identification method for soil iron-manganese nodule enrichment area based on soil geochemical data

Abstract

The invention belongs to the technical field of soil environment identification, and particularly relates to a rapid identification method for a soil iron-manganese nodule enrichment area based on soil geochemical data. Comprising the following steps: S1, screening soil geochemical element indexes of an iron-manganese nodule enrichment area and other areas in a to-be-identified area according to a soil forming mother rock, a soil forming environment and a soil forming process, and screening out index elements for distinguishing the iron-manganese nodule enrichment area from the other areas; s2, determining a threshold value of soil geochemical element indexes screened in S1; and S3, verifying the geochemical element index threshold value of the iron-manganese nodule enrichment area. According to the method, the iron-manganese nodule enrichment region can be effectively divided through area survey data quickly, the geological high-background ecological low-risk region can be divided quickly and accurately, and the method has a good market application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil environment identification, and particularly relates to a rapid identification method of soil iron-manganese nodule enrichment area based on soil geochemical data. BACKGROUND

[0002] Guangxi is one of the 14 key provinces for heavy metal pollution prevention and control in China. According to the latest national soil environmental quality standard for agricultural land (GB 15618-2018), the overall situation of heavy metal content in the soil of agricultural land in Guangxi is not optimistic, and the pollution of heavy metals such as cadmium, chromium and arsenic is serious.

[0004] According to the results of previous investigation and research, under the current soil environmental quality standard for agricultural land (GB 15618-2018), the geological high background of soil heavy metals has become a nationwide problem that restricts the division of soil environmental quality of cultivated land and the classification management of agricultural land. At present, the geological high background of heavy metals in Guangxi is mainly caused by carbonate rocks and black rocks. In the carbonate rock area of Guangxi, iron-manganese nodules are commonly found in the surface soil of the soil heavy metal anomaly enrichment area. A large amount of heavy metals in the soil are hosted in iron-manganese nodules. The iron-manganese nodule enrichment area is one of the main factors that lead to the need to complete the largest area of soil pollution prevention and control target in China. How to quickly identify the iron-manganese nodule enrichment area has become a major scientific problem that needs to be solved urgently for the classification and management of cultivated land and the production of food safety in Guangxi.

[0005] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the application, and should not be regarded as an acknowledgment or any form of suggestion that this information forms prior art that is publicly known. SUMMARY

[0006] The purpose of the present application is to provide a rapid identification method of soil iron-manganese nodule enrichment area based on soil geochemical data, so as to quickly identify the iron-manganese nodule enrichment area through area investigation data.

[0007] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: The rapid identification method of soil iron-manganese nodule enrichment area based on soil geochemical data comprises the following steps: S1, screening soil geochemical element indexes for distinguishing the iron-manganese nodule enrichment area from other areas according to the soil-forming parent rock, soil-forming environment and soil-forming process in the to-be-identified area; S2, determining the threshold value of the soil geochemical element indexes screened in S1; S3, verifying the geochemical element index threshold value of the iron-manganese nodule enrichment area.

[0008] As preferred, the soil geochemical element indicators of the iron-manganese nodule enrichment area and other areas in the to-be-identified region in S1 are screened, including the following steps: S11, selecting eight surface soil main element indicators in typical carbonate rock distribution areas and clastic rock distribution areas in the to-be-identified region, and calculating the elements with A>1.5 as the index elements in this time; the carbonate rock distribution area is the iron-manganese nodule enrichment area, and the elements selected for parameter calculation are: Al2O3, CaO, K2O, MgO, Na2O, SiO2, Mn, and Fe2O3, and the calculation formula is as follows: A=

[0009] C i =

[0010] In the formula, A represents the difference between the element scores of different rock series areas i, Ci T is the standardized parameter of element i in the carbonate rock distribution area, Ci S is the standardized parameter of element i in the clastic rock distribution area, Xi is the content of element i in the surface soil, and Ti represents the average content of element i in the national soil; The index elements with A>1.5 are Fe2O3 and Mn; S12, the Fe2O3 and Mn contents of the soil in the clastic rock distribution area with developed manganese-siliceous rock are high, in order to effectively distinguish the manganese-siliceous rock area from the carbonate rock distribution area, four surface soil trace element indicators of the carbonate rock distribution area and the manganese-siliceous rock area are selected to calculate the above formula, and the element with the largest A value is selected as the index element; the elements selected for parameter calculation are: Cd, Pb, Se, and Zn; The index element with the largest A value is Cd; The soil geochemical element indicators finally used to distinguish the iron-manganese nodule enrichment area from other areas are Fe2O3, Mn, and Cd.

[0011] As preferred, the threshold of the soil geochemical element indicators screened in S1 is determined in S2, including the following steps: S21, according to the screened soil geochemical element indicators, and selecting typical surface soil geochemical data of the iron-manganese nodule enrichment area, the manganese-siliceous rock area, and other areas in the to-be-identified region, a three-dimensional scatter model of geochemical elements is established; S22, the threshold of the soil geochemical element indicators is determined according to the distribution of each index element in the three-dimensional scatter model; when the content of the index element in the surface soil in the to-be-identified region meets the following conditions at the same time: C Fe2O3 >7 % C Mn >3000 mg / kg C Cd >1800 ng / kg Can be identified as iron manganese nodule enrichment area; In the formula, C Fe2O3 、 C Mn 、 C Cd Respectively represent the content of Fe2O3, Mn, Cd in surface soil.

[0012] As preferred, the geochemical element index threshold of the iron manganese nodule enrichment area in S3 is verified, including the following steps: S31, select the to-be-identified area as a verification object, according to the soil geochemical element index threshold determined in S2, screen the surface points meeting the iron manganese nodule enrichment area, and then use the ordinary Kriging interpolation method to delineate the iron manganese nodule enrichment area; S32, randomly select n regions in the delineated iron manganese enrichment area for verification by using the field verification method; the index for judging whether the selected region is an iron manganese nodule enrichment area is that the proportion of surface iron manganese nodule is more than 20%.

[0013] Compared with the prior art, the present application has the following beneficial effects: (1) The rapid identification method of the soil iron manganese nodule enrichment area based on soil geochemical data of the present application can quickly divide the iron manganese nodule enrichment area through area investigation data, and effectively realize the rapid and accurate division of the geological high background and ecological low risk area.

[0014] (2) The rapid identification method of the soil iron manganese nodule enrichment area based on soil geochemical data of the present application has clear ideas and high feasibility, and has practical value for the division of the farmland soil environment quality of the iron manganese nodule enrichment area and the management of agricultural land classification. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Is the method flowchart of the present application; Figure 2 Is a two-dimensional scatter plot of soil geochemical element A value of carbonate rock distribution area (iron manganese nodule enrichment area) and clastic rock area; Figure 3 Is a two-dimensional scatter plot of soil geochemical element A value of carbonate rock distribution area (iron manganese nodule enrichment area) and manganese-containing siliceous rock area; Figure 4 is a three-dimensional scatter plot of screening iron manganese nodule enrichment area geochemical element index; Figure 5 is a spatial distribution map of iron manganese nodule enrichment points in Tendeng County, Guangxi; Figure 6 is a field verification map of the rapid identification technology of iron manganese nodule enrichment area in Tendeng County, Guangxi. DETAILED DESCRIPTION

[0016] The technical solutions of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0017] In carbonate rock area, a large number of secondary minerals (iron manganese nodules) are formed by weathering, resulting in strong secondary enrichment of heavy metals in soil, showing typical geological high background characteristics. However, the effective content of heavy metals in iron manganese nodules is very low, which is generally difficult to be released into the environment and absorbed by plants. According to the current G15618 and "Soil Ten Provisions", the land quality classification management in this area cannot guarantee the scientific management of land resources, resulting in a large waste of arable land resources.

[0018] Referring to the drawings Figure 1 The present application provides a rapid identification method of soil iron manganese nodule enrichment area based on soil geochemical data, comprising the following steps: Step one, according to the soil geochemical element index of soil iron manganese nodule enrichment area and other areas in the to-be-identified region, the soil forming parent rock, soil forming environment and soil forming process are screened, specifically as follows: A, select 8 surface soil main element indexes in the to-be-identified region, and calculate the A of each index according to formula (1) and (2), and select A>1.5 as the index element of this time; A= (1) C i = (2) In the formula, A represents the difference between the element scores of different rock series i, Ci T is the normalized parameter of element i in carbonate rock distribution area, Ci S is the normalized parameter of element i in carbonate rock distribution area, Xi is the content of surface soil element i, and Ti represents the national average content of element i.

[0019] In the present embodiment, the selected elements for parameter calculation are: Al2O3, CaO, K2O, MgO, Na2O, SiO2, Mn, Fe2O3. The A value distribution of the eight soil geochemical element indicators of the carbonate rock salt distribution area (iron-manganese nodule enrichment area) and the clastic rock distribution area is shown in the attached Figure 2 , and the index elements with A>1.5 are Fe2O3 and Mn.

[0020] B. The Fe2O3 and Mn contents of the soil developed in the manganese-containing siliceous rock in the clastic rock distribution area are relatively high. In order to effectively distinguish the manganese-containing siliceous rock from the carbonate rock distribution area (iron-manganese nodule enrichment area), four surface soil trace element indicators in the two areas are selected and substituted into formulas (1) and (2), and the index element with the maximum A value is selected.

[0021] The A value distribution of the four soil geochemical element indicators of the carbonate rock salt distribution area (iron-manganese nodule enrichment area) and the manganese-containing siliceous rock distribution area is shown in the attached Figure 3 , and the selected elements for parameter calculation are: Cd, Pb, Se, Zn; and the index element with the maximum A value is Cd.

[0022] The soil geochemical element indicators finally used to distinguish the iron-manganese nodule enrichment area from other areas are Fe2O3, Mn, and Cd.

[0023] Step two, determine the threshold value of the soil geochemical element indicators screened in step one, as follows: A. According to the selected soil geochemical element indicators, and selecting typical surface soil geochemical data of the iron-manganese nodule enrichment area, the manganese-containing siliceous rock area, and other areas in the to-be-identified area, a three-dimensional scatter model of geochemical elements is established; B. The threshold value of the soil geochemical element indicators is determined according to the distribution of each index element in the three-dimensional scatter model; The three-dimensional scatter plot of the iron-manganese nodule enrichment area, the manganese-containing siliceous rock area, and other areas is shown in the attached Figure 4 , and finally it is determined that the to-be-identified area can be identified as the iron-manganese nodule enrichment area when the content of the index element in the surface soil of the to-be-identified area meets the conditions in formula (3) at the same time; C Fe2O3 >7 % C Mn >3000 mg / kg (3) C Cd >1800 ng / kg In the formula, C Fe2O3 , CMn 、 C Cd Respectively represent the content of Fe2O3, Mn, Cd in surface soil.

[0024] Step three, the threshold of geochemical element index of iron and manganese nodule enrichment area is verified, and the specific steps are as follows: A, select the to-be-identified area as the verification object, screen the surface points of the iron and manganese nodule enrichment area according to the geochemical element index threshold in step two, and then use the ordinary Kriging interpolation method to delineate the iron and manganese nodule enrichment area; B, using the method of field verification, randomly select n regions in the delineated iron and manganese enrichment area for verification, and the verification method is to select the surface soil iron and manganese nodule proportion in the region to be more than 20%.

[0025] In this embodiment, Guangxi Tiandeng County is selected as an example for verification: A, select 5670 geochemical data of surface soil in Tiandeng County, wherein 732 points meet the conditions in formula (3), and the specific point distribution is shown in the attached Figure 5 ; B, according to the iron and manganese nodule enrichment point, the ordinary Kriging interpolation method is used to delineate the iron and manganese nodule enrichment area in Tiandeng County, and 10 regions are randomly selected for field verification, and the verification results are shown in the attached Figure 6 and Table 1.

[0026] Table 1

[0027] From the data in Table 1, it can be seen that the accuracy rate of field verification is 90%, which shows that the rapid identification method of soil iron and manganese nodule enrichment area based on soil geochemical data according to the present application has the effect of rapidly identifying the iron and manganese nodule enrichment area through area investigation data, and the verification result also proves the accuracy of the method for identifying the iron and manganese nodule enrichment area.

[0028] The rapid identification method of soil iron and manganese nodule enrichment area based on soil geochemical data has guiding significance and practical value for the division of cultivated land soil environment quality and the management of agricultural land classification in the iron and manganese nodule enrichment area.

[0029] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A method for rapid identification of soil Fe-Mn nodule enrichment zones based on soil geochemical data, characterized in that, The method comprises the following steps: S1, screening soil geochemical element indexes of the iron-manganese nodule enrichment area and other areas in the to-be-identified region according to soil-forming parent rocks, soil-forming environments and soil-forming processes, and screening index elements for distinguishing the iron-manganese nodule enrichment area from other areas; S2, determining the threshold of the soil geochemical element indexes screened in S1; S3, verifying the geochemical element index threshold of the iron-manganese nodule enrichment area.

2. The method for rapid identification of soil iron-manganese nodule enriched area based on soil geochemical data according to claim 1, characterized in that, The screening of the soil geochemical element indexes of the iron-manganese nodule enrichment area and other areas in the to-be-identified region in S1 comprises the following steps: S11, selecting eight surface soil main element indexes in typical carbonate rock distribution areas and clastic rock distribution areas in the to-be-identified region, and calculating the elements with a screening A>1.5 as the index elements this time; the carbonate rock distribution area is the iron-manganese nodule enrichment area, and the elements selected for parameter calculation are Al2O3, CaO, K2O, MgO, Na2O, SiO2, Mn and Fe2O3, and the calculation formula is as follows: Where A represents the difference of element i scores in different lithologic zones, Ci T is the parameter of element i after standardization in carbonate rock distribution area, Ci S is the parameter of element i after standardization in clastic rock distribution area, Xi is the content of element i in surface soil, and Ti represents the national average content of element i in soil. The index elements with a screening A>1.5 are Fe2O3 and Mn; S12, the Fe2O3 and Mn contents of the soil of the manganese-bearing siliceous rock developed in the clastic rock distribution area are relatively high, in order to effectively distinguish the manganese-bearing siliceous rock area from the carbonate rock distribution area, four surface soil trace element indexes of the carbonate rock distribution area and the manganese-bearing siliceous rock area are selected to be substituted into the above formula to calculate, and the element with the largest A value is selected as the index element; the elements selected for parameter calculation are Cd, Pb, Se and Zn; The index element with the largest A value screened is Cd; The soil geochemical element indexes for distinguishing the iron-manganese nodule enrichment area from other areas are finally Fe2O3, Mn and Cd. 3.The method for rapid identification of soil iron-manganese nodule enrichment area based on soil geochemical data according to claim 1, characterized in that, The determination of the threshold of the soil geochemical element indexes screened in S1 in S2 comprises the following steps: S21, according to the screened soil geochemical element indexes, and selecting typical surface soil geochemical data of the iron-manganese nodule enrichment area, the manganese-bearing siliceous rock area and other areas in the to-be-identified region, a three-dimensional scatter model of geochemical elements is established; S22, the threshold of the soil geochemical element indexes is determined according to the distribution of each index element in the three-dimensional scatter model; when the content of the index element in the surface soil in the to-be-identified region simultaneously satisfies: It can be identified as the iron-manganese nodule enrichment area; In the formula, C Fe2O3 , C Mn , C Cd respectively represent the content of Fe2O3, Mn, and Cd in the surface soil.

4. The method for rapid identification of soil iron-manganese nodule enriched area based on soil geochemical data according to claim 1, characterized in that, The verification of the geochemical element index threshold of the iron-manganese nodule enrichment area in S3 comprises the following steps: S31, selecting the to-be-identified region as a verification object, screening surface points that satisfy the iron-manganese nodule enrichment area according to the threshold of the soil geochemical element indexes determined in S2, and then using the ordinary Kriging interpolation method to delineate the iron-manganese nodule enrichment area; S32, randomly selecting n regions in the delineated iron-manganese enrichment area for verification by using the field verification method; the index for judging whether the selected region is the iron-manganese nodule enrichment area is that the proportion of the surface iron-manganese nodule is more than 20%.

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