Agricultural land pollution risk evaluation method based on heavy metal occurrence form and total amount

Abstract

The invention belongs to the technical field of pollution prevention and control, and particularly discloses an agricultural land pollution risk evaluation method based on the occurrence form and total amount of heavy metal. The evaluation method comprises the following steps: measuring the heavy metal concentration Cn of a sample, obtaining a heavy metal element background value Bn of a region where the sample is located, and calculating a heavy metal total amount evaluation index S1; the S1 is compared with a preset heavy metal total amount pollution grade value range, and a heavy metal total amount pollution grade N1 is obtained; determining the heavy metal occurrence F1, F2, F3 and F4 states of the sample by adopting a preset method, and calculating a heavy metal form index S2; s2 is compared with a preset heavy metal form active grade value range, and a heavy metal form active grade N2 is obtained; and calculating a heavy metal pollution risk coefficient R, and comparing the R with each preset heavy metal pollution risk grade numerical range to obtain heavy metal pollution risk evaluation and control measures. The method has the characteristics of simple and convenient determination process, quantitative heavy metal form and capability of comprehensively reflecting pollution risks.

Description

Technical Field

[0001] The present invention belongs to the technical field of pollution prevention and control, and specifically relates to an agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals, which has a simple measurement process, quantifies the form of heavy metals, and can comprehensively reflect the pollution risk. Background Art

[0002] With the continuous advancement of industrialization, heavy metals produced in industrial production pollute agricultural land through sewage, dust, etc. Heavy metals in soil have the characteristics of non-degradability, low self-purification ability, concealment and high toxicity, which have a huge impact on agricultural output and agricultural product quality, and thus pose a major threat to human health and ecological security. In view of the core role of soil in agricultural production and ecological environment, there is an urgent need to conduct a comprehensive and objective ecological risk assessment of heavy metals in farmland soil to effectively guide the prevention and control of soil heavy metal pollution.

[0003] Existing studies have found that the total content of heavy metals in soil is not enough to fully reveal its pollution status; on the contrary, the form of heavy metals is the key to determining their migration, transformation ability, toxicity and bioavailability in soil. However, most of the current heavy metal pollution risk assessment methods only consider the total amount of heavy metals. In cases where the heavy metal background value of a site is high due to geological causes, or in cases of heavy metal contaminated sites that have been treated, the total amount assessment may lead to an overestimation of the risk to human health, thus failing to fully reflect the real pollution risk, resulting in some agricultural resources being abandoned and unable to be used. To this end, there is also an assessment method in the prior art that divides the risk level according to the ecological risk R of the heavy metal contaminated soil by constructing a functional relationship C1 (pH) between the leaching concentration of heavy metals in the soil sample and the pH value of the leaching agent, and then constructing a functional relationship C2 (pH) between the acid-soluble state concentration of heavy metals in the soil sample and the pH value of the leaching agent, and then calculating the risk concentration Crisk of the heavy metals in the soil sample: Crisk = 0.5 × C1 (pH) + 0.5 × C2 (pH), and then determining the total concentration C3 of the heavy metals in the soil sample, and finally calculating the ecological risk R of the heavy metal contaminated soil: R = Crisk / C3 × 100%; although the assessment method takes into account the relationship between the heavy metal concentration in different dissolved states and the total concentration, making the risk level division more strict and scientific and reasonable, and more conducive to the protection of the ecological environment; however, the division of this method is relatively rough, and does not fully consider the large differences in soil pollution under different occurrence forms of heavy metals, resulting in the risk level division result is not accurate enough, and cannot reflect the comprehensive impact of contaminated soil on the ecological environment. In addition, there is also a method of determining the heavy metal elements in soil samples, then extracting the occurrence forms of heavy metals to determine the bioavailable content of heavy metals, then determining the exposure concentration of heavy metals based on the bioavailable content of heavy metals, and then conducting health risk assessment analysis based on the exposure concentration of heavy metals. This assessment method combines the bioavailability of heavy metals with the health risk assessment model of heavy metals, which can reduce the uncertainty of the health risk model from the perspective of reasonable estimation of heavy metal exposure doses, thereby making the risk assessment more scientific and less error-prone; however, this method pays more attention to the comprehensive assessment of carcinogenic risks caused by oral ingestion, skin contact and respiratory inhalation, and only uses the occurrence forms of heavy metals in farmland soil as one of the intermediate indicators of the assessment, so it cannot comprehensively and objectively assess the ecological risks of heavy metals in farmland soil. For this reason, it is particularly important and urgent to develop an evaluation method that can comprehensively evaluate the heavy metal pollution risk of agricultural land and is applicable to various soil conditions. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals, which has a simple measurement process, quantifies heavy metal forms, and can comprehensively reflect pollution risks.

[0005] The present invention is implemented as follows: including obtaining a heavy metal total amount evaluation index S1, a heavy metal total amount pollution level N1 classification, obtaining a heavy metal form index S2, a heavy metal form active level N2 classification, and a heavy metal pollution risk assessment step, and the specific contents of each step are as follows; A. Obtaining the total amount of heavy metal evaluation indicators S1: Collect soil samples and then measure the heavy metal concentration C of the soil samples n , obtain the heavy metal element background value B in the area where the soil sample is located n , calculate the total amount of heavy metal evaluation index S1: (1); B. Classification of heavy metal total pollution level N1: Compare the heavy metal total evaluation index S1 with the preset numerical range of each heavy metal total pollution level to obtain the corresponding heavy metal total pollution level N1; C. Obtaining the heavy metal form index S2: First, the preset method is used to determine the heavy metal occurrence F1, F2, F3 and F4 of the soil sample, and then the heavy metal form index S2 is calculated: (2); D. Classification of heavy metal form activity level N2: Compare the heavy metal form index S2 with the preset value range of each heavy metal form activity level to obtain the corresponding heavy metal form activity level N2; E. Heavy metal pollution risk assessment: First calculate the heavy metal pollution risk coefficient R: (3), Then compare the heavy metal pollution risk coefficient R with the preset numerical range of each heavy metal pollution risk level to obtain the corresponding heavy metal pollution risk assessment and control measures.

[0006] Furthermore, in step A, the soil sample is tested for heavy metal concentration C n The method is to take a preset mass of soil sample, add a preset volume of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid for digestion, filter to obtain an extract after digestion, use the preset acid solution to clean the digestion container, combine the washing solution with the extract after filtration, and determine the heavy metal concentration C after the mixed solution is fixed to the predetermined scale. n .

[0007] Furthermore, in step A, 1.0 g of soil sample is placed in a polytetrafluoroethylene digestion tank, 60 mL of a hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid is added, and then the sample is placed in a microwave digestion instrument and digested at 180° C. for 20 to 40 min. After digestion, the sample is cooled to room temperature, filtered using filter paper to obtain an extract and collected in a volumetric flask. The digestion tank is cleaned with 20 to 30 mL of dilute nitric acid for no less than 3 times, and the washings are combined and filtered and collected in a volumetric flask containing the extract. Subsequently, distilled water is added to make up the volume to the scale of the volumetric flask, and the heavy metal concentration C is determined using ICP-MS. n .

[0008] Furthermore, the numerical ranges of the total amount of heavy metal pollution levels preset in step B are shown in Table 1: Table 1 Classification of total heavy metal pollution level N1 .

[0009] Furthermore, the determination of the heavy metal occurrence forms of the soil sample in step C comprises the following steps: C10, Heavy metal occurrence F1 state determination: First, take 1.0g soil sample and add 40mL of 0.11mol·L -1 The acetic acid solution was then placed in a water bath oscillator and shaken at 240-300 r / min at room temperature. -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F1 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue I; C20, heavy metal occurrence F2 state determination: First, add 40mL of 0.5mol·L -1 Hydroxylamine hydrochloride solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F2 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue II; C30, heavy metal occurrence F3 state determination: First, add 10mL of 0.1mol·L -1Potassium permanganate solution was kept at room temperature for 0.8 to 1.2 h; then 10 mL of 0.1 mol·L -1 The potassium permanganate solution was kept at room temperature for 0.8 to 1.2 hours. Then, 50 mL of 1 mol·L -1 Ammonium acetate solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F3 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue III; C40. Determination of heavy metals in F4 state: First, add 60 mL of a mixed acid of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid to the residue III, and then use ICP-MS to determine the heavy metal concentration of the solution as the heavy metal in F4 state.

[0010] Furthermore, in the steps C10, C20 and C30, the residue after the supernatant is extracted is washed with high-purity water, and then the residue and the washing solution are kept at room temperature for 240 to 300 r·min. -1 The speed level oscillates for 15 to 25 minutes, then increases to 3500 to 4500 r / min. -1 After centrifugation for 15 to 25 minutes, the washing solution is removed; hydroxylamine hydrochloride solution is added to the residue I of C20, potassium permanganate solution is added to the residue II of C30, and ammonium acetate solution is added to the residue, and the pH is adjusted to 1.5 to 2.5 after adding.

[0011] Furthermore, it is characterized in that the numerical ranges of the activity levels of each heavy metal form preset in the step D are as shown in Table 2: Table 2 Classification of heavy metal forms and activity levels N2 .

[0012] Furthermore, the numerical ranges of the heavy metal pollution risk levels preset in step E are shown in Table 3: Table 3 Heavy metal pollution risk assessment and control measures .

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention obtains the background value B of heavy metal elements in the area where the soil sample is located. n and the measured heavy metal concentrations in soil samples C nThe functional relationship is formed to obtain the total heavy metal evaluation index S1, and the total heavy metal pollution level N1 is divided. The division of the total heavy metal pollution level N1 can avoid the high heavy metal background value of the site caused by geological causes, or the excessively high risk assessment results of the heavy metal contaminated site after treatment, thereby avoiding the aforementioned problem of agricultural land being unusable due to the excessively high heavy metal pollution level, and improving the utilization rate of agricultural land resources.

[0014] 2. The present invention aims to solve the problems of single analysis indicators and incomplete analysis results in existing heavy metal pollution risk assessment. Based on the fact that the occurrence form of heavy metals determines the migration characteristics and toxicity of heavy metals, the present invention comprehensively considers the total amount of heavy metals in agricultural land and their different occurrence forms. The final risk assessment results can comprehensively reflect the degree of harm of heavy metals in agricultural land, thereby effectively guiding the prevention and control of heavy metal pollution in agricultural land and making the entire evaluation process simple and reliable.

[0015] 3. The present invention classifies and quantitatively analyzes heavy metals in different occurrence forms in agricultural land, which can avoid the influence of human factors on the accuracy of evaluation results; and for areas with high background values ​​due to geological causes, evaluation areas after heavy metal pollution remediation, and areas with inaccurate geological background values, the present invention divides the heavy metal forms into active levels, fully considering the situation where the heavy metal background values ​​in the existing heavy metal pollution risk assessment are quite different from the geological conditions of the study area. It can effectively reflect the risk of pollution migration, and provide a reference for heavy metal pollution risk assessment of polluted agricultural land in different periods and the restoration effect after pollution control.

[0016] In summary, the present invention has the characteristics of simple determination process, quantification of heavy metal forms, and the ability to comprehensively reflect pollution risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The heavy metal concentration C is determined in the embodiment of the present invention. n And heavy metal storage form flow chart. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention belong to the protection scope of the present invention.

[0019] The present invention includes the steps of obtaining a heavy metal total amount evaluation index S1, dividing the heavy metal total amount pollution level N1, obtaining a heavy metal form index S2, dividing the heavy metal form active level N2, and heavy metal pollution risk assessment. The specific contents of each step are as follows; A. Obtaining the total amount of heavy metal evaluation indicators S1: Collect soil samples and then measure the heavy metal concentration C of the soil samplesn , obtain the heavy metal element background value B in the area where the soil sample is located n , calculate the total amount of heavy metal evaluation index S1: (1); B. Classification of heavy metal total pollution level N1: Compare the heavy metal total evaluation index S1 with the preset numerical range of each heavy metal total pollution level to obtain the corresponding heavy metal total pollution level N1; C. Obtaining the heavy metal form index S2: First, the preset method is used to determine the heavy metal occurrence F1, F2, F3 and F4 of the soil sample, and then the heavy metal form index S2 is calculated: (2); D. Classification of heavy metal form activity level N2: Compare the heavy metal form index S2 with the preset value range of each heavy metal form activity level to obtain the corresponding heavy metal form activity level N2; E. Heavy metal pollution risk assessment: First calculate the heavy metal pollution risk coefficient R: (3), Then compare the heavy metal pollution risk coefficient R with the preset numerical range of each heavy metal pollution risk level to obtain the corresponding heavy metal pollution risk assessment and control measures.

[0020] In step A, the soil sample is used to measure the heavy metal concentration C n The method is to take a preset mass of soil sample, add a preset volume of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid for digestion, filter to obtain an extract after digestion, use the preset acid solution to clean the digestion container, combine the washing solution with the extract after filtration, and determine the heavy metal concentration C after the mixed solution is fixed to the predetermined scale. n .

[0021] In step A, 1.0 g of soil sample is placed in a polytetrafluoroethylene digestion tank, 60 mL of a hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid is added, and then the sample is placed in a microwave digestion instrument and digested at 180° C. for 20 to 40 min. After digestion, the sample is cooled to room temperature, filtered using filter paper to obtain an extract and collected in a volumetric flask. The digestion tank is cleaned with 20 to 30 mL of dilute nitric acid for no less than 3 times, and the washings are combined and filtered and collected in a volumetric flask containing the extract. Subsequently, distilled water is added to make up the volume to the scale of the volumetric flask, and the heavy metal concentration C is determined using ICP-MS. n .

[0022] The numerical ranges of the total amount of heavy metal pollution levels preset in step B are shown in Table 1: Table 1 Classification of total heavy metal pollution level N1 .

[0023] The determination of the heavy metal occurrence forms of the soil sample in step C comprises the following steps: C10, Heavy metal occurrence F1 state determination: First, take 1.0g soil sample and add 40mL of 0.11mol·L -1 The acetic acid solution was then placed in a water bath oscillator and shaken at 240-300 r / min at room temperature. -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F1 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue I; C20, heavy metal occurrence F2 state determination: First, add 40mL of 0.5mol·L -1 Hydroxylamine hydrochloride solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F2 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue II; C30, heavy metal occurrence F3 state determination: First, add 10mL of 0.1mol·L -1 Potassium permanganate solution was kept at room temperature for 0.8 to 1.2 h; then 10 mL of 0.1 mol·L -1 The potassium permanganate solution was kept at room temperature for 0.8 to 1.2 hours. Then, 50 mL of 1 mol·L -1 Ammonium acetate solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F3 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue III; C40. Determination of heavy metals in F4 state: First, add 60 mL of a mixed acid of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid to the residue III, and then use ICP-MS to determine the heavy metal concentration of the solution as the heavy metal in F4 state.

[0024] In the steps C10, C20 and C30, the residue after the supernatant is extracted is washed with high-purity water, and then the residue and the washing solution are kept at room temperature for 240 to 300 r·min. -1 The speed level oscillates for 15 to 25 minutes, then increases to 3500 to 4500 r / min. -1 After centrifugation for 15 to 25 minutes, the washing solution is removed; hydroxylamine hydrochloride solution is added to the residue I of C20, potassium permanganate solution is added to the residue II of C30, and ammonium acetate solution is added to the residue, and the pH is adjusted to 1.5 to 2.5 after adding.

[0025] The numerical ranges of the activity levels of the heavy metal forms preset in step D are shown in Table 2: Table 2 Classification of heavy metal forms and activity levels N2 .

[0026] The numerical ranges of the heavy metal pollution risk levels preset in step E are shown in Table 3: Table 3 Heavy metal pollution risk assessment and control measures .

[0027] Example S100: Collect soil samples, take 1.0g of soil sample and place it in a polytetrafluoroethylene digestion tank, add 60mL of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid (mixed in a volume ratio of 5:3:5:1), then place it in a microwave digestion instrument and digest it at 180℃ for 30min, cool it to room temperature after digestion, filter it with filter paper to obtain the extract and collect it in a volumetric flask, use 30mL of dilute nitric acid to clean the digestion tank for no less than 3 times, combine the washings and filter them, collect them in a volumetric flask containing the extract, then add distilled water to make up to the volumetric flask scale, and use ICP-MS (inductively coupled plasma mass spectrometer) to determine the heavy metal concentration C n , obtain the heavy metal element background value B in the area where the soil sample is located n , calculate the total amount of heavy metal evaluation index S1: (1).

[0028] S200: Compare the heavy metal total amount evaluation index S1 with the preset numerical ranges of each heavy metal total amount pollution level to obtain the corresponding heavy metal total amount pollution level N1. The preset numerical ranges of each heavy metal total amount pollution level are shown in Table 1: Table 1 Classification of total heavy metal pollution level N1 .

[0029] S300: First, the F1, F2, F3 and F4 states of heavy metals in soil samples are determined using a preset method: S310, first take 1.0g of soil sample and add 40mL of 0.11mol·L -1 The acetic acid solution was then placed in a water bath oscillator and shaken at 240 r / min at room temperature. -1 The speed was oscillated horizontally for 16 h, and then at 4000 r / min -1 After centrifugation for 20 minutes, the supernatant was extracted and the heavy metal concentration was determined by ICP-MS as the heavy metal occurrence F1 state; 20 mL of high-purity water was added to wash the residue after extracting the supernatant, followed by oscillation for 20 minutes, and centrifuged again for 20 minutes to remove the washing liquid to obtain residue I.

[0030] S320, first add 40mL of 0.5mol·L -1 Hydroxylamine hydrochloride solution was maintained at 240 r / min at room temperature. -1 The speed was oscillated horizontally for 16 h, and then at 4000 r / min -1 After centrifugation for 20 minutes, the supernatant was extracted and the heavy metal concentration was determined by ICP-MS as the heavy metal occurrence F2 state; 20 mL of high-purity water was added to wash the residue after extracting the supernatant, followed by oscillation for 20 minutes, and centrifuged again for 20 minutes to remove the washing liquid to obtain residue II.

[0031] S330, first add 10mL of 0.1mol·L -1 Potassium permanganate solution was kept at room temperature for 1 h; then 10 mL of 0.1 mol·L -1 The potassium permanganate solution was kept at room temperature for 1 hour; then 50 mL of 1 mol·L -1 Ammonium acetate solution was maintained at 240 r / min at room temperature. -1 The speed was oscillated horizontally for 16 h, and then at 4000 r / min -1 After centrifugation for 20 minutes, the supernatant was extracted and the heavy metal concentration was determined by ICP-MS as the heavy metal occurrence F3 state; 20 mL of high-purity water was added to wash the residue after extracting the supernatant, followed by oscillation for 20 minutes, and centrifuged again for 20 minutes to remove the washing liquid to obtain residue III.

[0032] S340. First, add 60 mL of a mixed acid of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid (mixed in a volume ratio of 5:3:5:1) to the residue III, and then use ICP-MS to determine the heavy metal concentration of the solution as the heavy metal occurrence F4 state.

[0033] Then calculate the heavy metal form index S2: (2).

[0034] S400: Compare the heavy metal form index S2 with the preset value ranges of the activity levels of each heavy metal form to obtain the corresponding heavy metal form activity level N2; the preset value ranges of the activity levels of each heavy metal form are as shown in Table 2: Table 2 Classification of heavy metal forms and activity levels N2 .

[0035] S500: First calculate the heavy metal pollution risk factor R: (3), Then compare the heavy metal pollution risk coefficient R with the preset value range of each heavy metal pollution risk level to obtain the corresponding heavy metal pollution risk assessment and control measures. The preset value range of each heavy metal pollution risk level is shown in Table 3: Table 3 Heavy metal pollution risk assessment and control measures .

[0036] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for assessing agricultural land pollution risk based on the presence and total amount of heavy metals, characterized in that: It includes obtaining the total amount of heavy metal evaluation index S1, the total amount of heavy metal pollution level N1 classification, obtaining the heavy metal form index S2, the heavy metal form active level N2 classification, and the heavy metal pollution risk assessment steps. The specific contents of each step are as follows; A. Obtaining the total amount of heavy metal evaluation indicators S1: Collect soil samples and then measure the heavy metal concentration C of the soil samples n , obtain the heavy metal element background value B in the area where the soil sample is located n , calculate the total amount of heavy metal evaluation index S1: （1）； B. Classification of heavy metal total pollution level N1: Compare the heavy metal total evaluation index S1 with the preset numerical range of each heavy metal total pollution level to obtain the corresponding heavy metal total pollution level N1; C. Obtaining the heavy metal form index S2: First, the preset method is used to determine the heavy metal occurrence F1, F2, F3 and F4 of the soil sample, and then the heavy metal form index S2 is calculated: （2）； D. Classification of heavy metal form activity level N2: Compare the heavy metal form index S2 with the preset value range of each heavy metal form activity level to obtain the corresponding heavy metal form activity level N2; E. Heavy metal pollution risk assessment: First calculate the heavy metal pollution risk coefficient R: （3）， Then compare the heavy metal pollution risk coefficient R with the preset numerical range of each heavy metal pollution risk level to obtain the corresponding heavy metal pollution risk assessment and control measures.

2. The agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals according to claim 1 is characterized in that: In step A, the soil sample is used to measure the heavy metal concentration C n The method is to take a preset mass of soil sample, add a preset volume of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid for digestion, filter to obtain an extract after digestion, use the preset acid solution to clean the digestion container, combine the washing solution with the extract after filtration, and determine the heavy metal concentration C after the mixed solution is fixed to the predetermined scale. n .

3. The agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals according to claim 2 is characterized in that: In step A, 1.0 g of soil sample is placed in a polytetrafluoroethylene digestion tank, 60 mL of a hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid mixed acid is added, and then the sample is placed in a microwave digestion instrument and digested at 180° C. for 20 to 40 min. After digestion, the sample is cooled to room temperature, filtered using filter paper to obtain an extract and collected in a volumetric flask. The digestion tank is cleaned with 20 to 30 mL of dilute nitric acid for no less than 3 times, and the washings are combined and filtered and collected in a volumetric flask containing the extract. Subsequently, distilled water is added to make up the volume to the scale of the volumetric flask, and the heavy metal concentration C is determined using ICP-MS. n .

4. The method for agricultural land pollution risk assessment based on the occurrence form and total amount of heavy metals according to claim 1 is characterized in that: The numerical ranges of the total amount of heavy metal pollution levels preset in step B are shown in Table 1: Table 1 Classification of total heavy metal pollution level N1 。 5. The agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals according to claim 1 is characterized in that: The determination of the heavy metal occurrence forms of the soil sample in step C comprises the following steps: C10, Heavy metal occurrence F1 state determination: First, take 1.0g soil sample and add 40mL of 0.11mol·L -1 The acetic acid solution was then placed in a water bath oscillator and shaken at 240-300 r / min at room temperature. -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F1 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue I; C20, heavy metal occurrence F2 state determination: First, add 40mL of 0.5mol·L -1 Hydroxylamine hydrochloride solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F2 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue II; C30, heavy metal occurrence F3 state determination: First, add 10mL of 0.1mol·L -1 Potassium permanganate solution was kept at room temperature for 0.8 to 1.2 h; then 10 mL of 0.1 mol·L -1 The potassium permanganate solution was kept at room temperature for 0.8 to 1.2 hours. Then, 50 mL of 1 mol·L -1 Ammonium acetate solution, maintained at 240-300 r·min at room temperature -1 The speed level oscillates for 14 to 18 hours, and then at 3500 to 4500 r / min -1 Centrifuge for 15 to 25 minutes, extract the supernatant, and finally use ICP-MS to determine the heavy metal concentration of the supernatant as the heavy metal occurrence F3 state; add 15 to 25 mL of high-purity water to wash the residue after extracting the supernatant, then shake for 15 to 25 minutes, centrifuge again for 15 to 25 minutes, and then remove the washing liquid to obtain residue III; C40. Determination of heavy metals in F4 state: First, add 60 mL of a mixed acid of hydrofluoric acid-hydrochloric acid-nitric acid-perchloric acid to the residue III, and then use ICP-MS to determine the heavy metal concentration of the solution as the heavy metal in F4 state.

6. The method for agricultural land pollution risk assessment based on the occurrence form and total amount of heavy metals according to claim 5 is characterized in that: In the steps C10, C20 and C30, the residue after the supernatant is extracted is washed with high-purity water, and then the residue and the washing solution are kept at room temperature for 240 to 300 r·min. -1 The speed level oscillates for 15 to 25 minutes, then increases to 3500 to 4500 r / min. -1 After centrifugation for 15 to 25 minutes, remove the washing solution; A hydroxylamine hydrochloride solution is added to the residue I of C20, a potassium permanganate solution is added to the residue II of C30, and an ammonium acetate solution is added to the residue, and the pH is adjusted to 1.5-2.5 after the addition.

7. The agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals according to any one of claims 1 to 6, characterized in that: The numerical ranges of the activity levels of the heavy metal forms preset in step D are shown in Table 2: Table 2 Classification of heavy metal forms and activity levels N2 。 8. The agricultural land pollution risk assessment method based on the occurrence form and total amount of heavy metals according to claim 7 is characterized in that: The numerical ranges of the heavy metal pollution risk levels preset in step E are shown in Table 3: Table 3 Heavy metal pollution risk assessment and control measures 。

Images