An assessment method for multi-level regional soil ecological risk

Abstract

The present invention provides a method for evaluating the multi-level regional soil ecological risk. The evaluation method is based on the regional rare earth exposure data and species toxicity data, and through the mutually coupled screening risk assessment, semi-probability risk assessment and probability risk assessment, the rare earth elements that need to be prioritized in the region are screened out, and the ecological risk of the prioritized rare earth elements is used to represent the comprehensive ecological risk of the rare earth element mixture. The present invention establishes a set of evaluation methods from qualitative to quantitative, which accurately reflects the ecological risk of regional rare earth pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring, and relates to a method for evaluating ecological risks, in particular to a method for evaluating the ecological risks of multi-level regional soil. Background Art

[0002] Rare earth resources are important strategic resources in China. However, the exploitation of rare earths has brought significant impacts on the environment. There are few relevant studies on the ecological risk assessment of rare earth elements in Chinese soil, and the ecological risks caused by rare earth elements in soil have not been deeply understood. The ecological risk assessment of the vast majority of rare earth elements only uses a simple quotient index method for screening assessment, and only relying on the screening assessment cannot accurately and quantitatively obtain the ecological risk level of pollutants. Since rare earth elements are a combination of 17 elements, rare earth pollution is usually mixed pollution. It is not rigorous to only evaluate the ecological risks of individual rare earth elements. Therefore, for mixed pollution, it is necessary to comprehensively evaluate the attention levels of different elements and screen out the elements that need to be prioritized for attention.

[0003] In view of this, the present invention is specifically proposed to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for evaluating the ecological risks of multi-level regional soil, which establishes a set of evaluation methods from qualitative to quantitative, screens out the rare earth elements that need to be prioritized for attention in the region, and uses the ecological risks of the prioritized rare earth elements to represent the comprehensive ecological risks of rare earth element mixtures, thereby accurately reflecting the ecological risks of regional rare earth pollution.

[0005] To achieve the purpose of this invention, the following technical solutions are adopted:

[0006] The present invention provides a method for evaluating the ecological risks of multi-level regional soil, characterized in that the evaluation method is based on regional rare earth exposure data and species toxicity data, and through mutually coupled screening risk assessment, semi-probability risk assessment and probability risk assessment, screens out the rare earth elements that need to be prioritized for attention in the region, and uses the ecological risks of the prioritized rare earth elements to represent the comprehensive ecological risks of rare earth element mixtures.

[0007] Compared with the traditional evaluation method that only uses screening assessment, the present invention couples semi-probability risk assessment and probability risk assessment on this basis, and then obtains the probability value of the ecological risks of rare earth elements in regional soil, thereby screening out the rare earth elements that need to be prioritized for attention in the region, and using the ecological risks of the prioritized rare earth elements to represent the comprehensive ecological risks of rare earth element mixtures. Compared with the quotient value obtained by screening assessment, using the probability value to represent the ecological risk is more scientific and accurate, and is convenient for subsequent risk management. This evaluation method from qualitative to quantitative more accurately reflects the ecological risks of regional rare earth pollution.

[0008] Preferably, the regional rare earth exposure data includes the exposure concentration.

[0009] Preferably, the screening risk assessment combines the regional geochemical baseline concentration and the exposure concentration to calculate the ecological risk index for each rare earth element, which is used to evaluate the soil ecological risks of each rare earth element and the rare earth elements as a whole.

[0010] Preferably, the regional geochemical baseline concentration includes the background concentration.

[0011] Preferably, the ecological risk index includes an exposure concentration-related index and an ecology-related index.

[0012] Preferably, the calculation process of the exposure concentration-related index combines the background concentration and the exposure concentration.

[0013] Preferably, the exposure concentration-related index includes any one or at least two combinations of the geoaccumulation index, the pollution index, or the pollution load index. Typical but non-limiting combinations include the combination of the geoaccumulation index and the pollution index, the combination of the pollution index and the pollution load index, the combination of the geoaccumulation index and the pollution load index, or the combination of the geoaccumulation index, the pollution index, and the pollution load index.

[0014] In the present invention, the formula for calculating the geoaccumulation index (I geo ) is as follows:

[0015]

[0016] Wherein, C n represents the exposure concentration of the rare earth element (mg / kg), B n represents the background concentration of the rare earth element (mg / kg), and the constant 1.5 is a factor to minimize the possible change in the background concentration due to petrogenetic effects.

[0017] For the geoaccumulation index, a positive value of I geo usually indicates the impact of human activities on soil ecology, and based on I geo , the pollution level can be divided into the following seven categories: unpolluted (I geo ≤0); unpolluted to moderately polluted (0 < I geo ≤1); moderately polluted (1 < I geo ≤2); moderately to severely polluted (2 < I geo ≤3); severely polluted (3 < I geo ≤4); severely to extremely polluted (4 < I geo ≤5); extremely polluted (I geo >5).

[0018] In the present invention, the pollution index (PI) and the pollution load index (PLI) are effective indices for determining the pollution level, and their calculation formulas are as follows respectively:

[0019] PI = C n / B n

[0020]

[0021] where C n represents the exposure concentration (mg / kg) of rare earth elements, B n represents the background concentration (mg / kg) of rare earth elements, and N represents the number of types of rare earth elements.

[0022] Based on the PLI, the pollution degree can be divided into the following five categories: low pollution degree (PLI < 1); medium pollution degree (1 < PLI ≤ 2); heavy pollution degree (2 < PLI ≤ 5); severe pollution (PLI > 5).

[0023] Preferably, in the calculation process of the ecological correlation index, the toxicity coefficient and the exposure concentration are combined.

[0024] Preferably, the calculation of the toxicity coefficient is based on the Hakanson principle.

[0025] Preferably, the ecological correlation index includes the potential ecological risk index and / or the potential ecological risk factor.

[0026] In the present invention, the potential ecological risk index (RI) is the sum of the potential ecological risk factors (E ri ) of each rare earth element, and the calculation formulas are as follows respectively:

[0027]

[0028] E ri = T i ×PI i

[0029] where T i represents the toxicity factor of rare earth elements, and PI i represents the pollution index of rare earth elements.

[0030] Based on E ri the risk level can be divided into the following five categories: slight risk (E ri ≤ 17); medium risk (17 < E ri ≤ 34); relatively severe risk (34 < E ri ≤ 68); severe risk (68 < E ri ≤ 136); very severe risk (E ri> 136).

[0031] Based on the RI, the risk levels can be divided into the following four categories: low ecological risk (RI ≤ 90); moderate ecological risk (90 < RI ≤ 180); relatively high ecological risk (180 < RI ≤ 360); very high ecological risk (RI > 360).

[0032] Preferably, the semi-probabilistic risk assessment is based on the screening risk assessment, and calculates the proportion of the ecological risk index of each rare earth element at different pollution levels.

[0033] Preferably, the probabilistic risk assessment combines the exposure concentration distribution and the species sensitivity distribution, and through modeling, evaluates the soil ecological risks of each rare earth element and the overall rare earth elements from a probabilistic perspective.

[0034] Preferably, the establishment of the exposure concentration distribution is based on the exposure concentration.

[0035] Preferably, the establishment of the species sensitivity distribution is based on the species toxicity data.

[0036] Preferably, the modeling process includes the following steps:

[0037] (1) According to the environmental protection objectives and the species sensitivity distribution, obtain the ecological risk threshold of rare earth elements;

[0038] (2) According to the exposure concentration and the species sensitivity distribution, obtain the potential species impact proportion as the risk value, and evaluate the soil ecological risk of each rare earth element;

[0039] (3) Using the effect addition model, according to the potential species impact proportion obtained in step (2), obtain the potential species impact proportion of the mixture as the risk value, and evaluate the overall ecological risk of rare earth elements;

[0040] (4) Using the joint probability curve, combine the exposure concentration distribution and the species sensitivity distribution, and calculate the overall risk probability and safety threshold;

[0041] (5) Combining the potential species impact proportion obtained in step (2) with the overall risk probability and safety threshold obtained in step (4), screen out the rare earth elements that need to be prioritized in the region.

[0042] In the present invention, the species sensitivity distribution (SSD) is a community-level dose-effect ecological risk assessment model, and the joint probability curve (JPC) is a curve representing the relationship between species and the environment constructed by combining the distribution functions of effect concentrations and exposure concentrations. By combining the SSD and the JPC, the actual risks of rare earth elements are obtained, and the potential species impact proportion (PAF) is calculated through the SSD model.

[0043] When each component in the rare earth element mixture has the same toxic mode of action (TMoAs), the potential species impact fraction (msPAF) of the mixture is calculated by the CA model, and the relevant calculation formula is as follows:

[0044]

[0045]

[0046]

[0047] When the TMoAs of each component in the rare earth element mixture are different or unknown, msPAF is calculated by the IA model, and the relevant calculation formula is as follows:

[0048]

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] Compared with the traditional evaluation method that only adopts screening evaluation, the present invention couples semi-probability risk assessment and probability risk assessment on this basis, and then obtains the probability value of the ecological risk of rare earth element regional soil, thereby screening out the rare earth elements that need to be prioritized in the region, and using the ecological risk of the prioritized rare earth elements to represent the comprehensive ecological risk of the rare earth element mixture. Compared with the quotient value obtained by screening evaluation, using the probability value to represent the ecological risk is more scientific and accurate, and is convenient for later risk management. This evaluation method from qualitative to quantitative more accurately reflects the ecological risk of regional rare earth pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a flowchart of the evaluation method for multi-level regional soil ecological risk provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0053] Example 1

[0054] This example provides an evaluation method for multi-level regional soil ecological risk. In order to specifically describe the implementation process of the evaluation method, this example conducts risk assessment based on rare earth elements in the Ganzhou area, and all data are collected from databases such as WOS and CNKI.

[0055] The research area of this embodiment is eight counties in Ganzhou. The average exposure concentration (mg / kg) of rare earth elements in the soil of each county is shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] According to the exposure concentration (C n ) of rare earth elements in Table 1, combined with its background concentration (B n ), the geo-accumulation index (I geo ) of rare earth elements in the soil of each county in Ganzhou is calculated and shown in Table 2. The relevant calculation formula is as follows:

[0060]

[0061] Table 2

[0062]

[0063] According to the exposure concentration (C n ) of rare earth elements in Table 1, combined with its background concentration (B n ), the pollution index (PI) of rare earth elements in the soil of each county in Ganzhou is calculated and shown in Table 3. The relevant calculation formula is as follows:

[0064] PI = C n / B n

[0065] Table 3

[0066]

[0067] According to the pollution index (PI) of rare earth elements in Table 3, the pollution load index (PLI) of rare earth elements in the soil of each county in Ganzhou is calculated and shown in Table 4. The relevant calculation formula is as follows:

[0068]

[0069] Table 4

[0070]

[0071] Combined with the ecological risk index in Tables 1 - 4, it can be seen that Eu, Pr, and Nd are the three rare earth elements that cause the greatest ecological risk in the Ganzhou area. Moreover, the spatial distribution of rare earth elements determines their risk distribution. Rare earth elements may cause a certain degree of ecological risk in Longnan, Dingnan, and Xunwu, and there is almost no risk in other places.

[0072] According to the pollution index (PI) of rare earth elements in Table 3, combined with their toxicity factors (T i ), the potential ecological risk factors (E ri ) of rare earth elements in the soil of each county and district in Ganzhou are calculated as shown in Table 5. The relevant calculation formula is as follows:

[0073] E ri = T i ×PI i

[0074] Table 5

[0075]

[0076] According to the potential ecological risk factors (E ri ) of rare earth elements in Table 5, the potential ecological risk index (RI) of rare earth elements in the soil of each county and district in Ganzhou is calculated as shown in Table 6. The relevant calculation formula is as follows:

[0077]

[0078] Table 6

[0079]

[0080] According to the risk level judgment criteria of the potential ecological risk factors (E ri ) of rare earth elements in Table 5, the proportion of the evaluation results of each rare earth element is shown in Table 7.

[0081] Table 7

[0082]

[0083] According to the risk level judgment criteria of the potential ecological risk index (RI) of rare earth elements in Table 6, the proportion of the overall evaluation results of rare earth elements is shown in Table 8.

[0084] Table 8

[0085]

[0086] Combined with the ecological risk index in Tables 5 - 8, it can be seen that Eu, Lu, and Tb are the three rare earth elements that cause the greatest ecological risk in the Ganzhou area, and the RI evaluation results are basically consistent with the PLI. The areas with the greatest ecological risk are both Longnan and Xunwu. In addition, the ecological risk level evaluated by PLI for each area in Ganzhou is generally smaller than that evaluated by RI for each area in Ganzhou because PLI is a relatively simple calculation model that only considers the exposure concentration, and the risk judgment criteria established by it are often too conservative.

[0087] It can be seen that although the results of RI and PLI in evaluating the overall ecological risk of rare earth elements in Ganzhou area are similar, this is because some light rare earth elements (Eu) with relatively high exposure concentrations and non-low toxicity coefficients have a relatively high contribution rate to the overall ecological risk of rare earth elements. However, there are still significant differences when evaluating each rare earth element. That is, in addition to Eu, Tb and Sm with relatively high toxicity coefficients also show relatively high pollution levels and ecological risks. This is because Eri not only considers the exposure concentration of rare earth elements but also takes into account the certain ecologicality of rare earth elements. Starting from the abundance principle, sedimentation effect and rationality principle of sedimentology, toxicology and ecological sorting factors, Eri can more accurately combine the ecologicality of rare earth elements to conduct ecological risk assessment of rare earth elements. geo When evaluating each rare earth element, there are still significant differences. That is, in addition to Eu, Tb and Sm with relatively high toxicity coefficients also show relatively high pollution levels and ecological risks. This is because Eri not only considers the exposure concentration of rare earth elements but also takes into account the certain ecologicality of rare earth elements. Starting from the abundance principle, sedimentation effect and rationality principle of sedimentology, toxicology and ecological sorting factors, Eri can more accurately combine the ecologicality of rare earth elements to conduct ecological risk assessment of rare earth elements.

[0088] In the process of probabilistic risk assessment, 349 pieces of toxicity data of rare earth elements were screened in this embodiment for establishing the species sensitivity distribution (SSD). The data situation of each rare earth element is shown in Table 9.

[0089] Table 9

[0090]

[0091] The species sensitivity distribution (SSD) is a community-level dose-effect ecological risk assessment model. Use the BMC-SSD software to plot the SSD curve for the data in Table 9, and input the exposure concentration of the environment into the obtained SSD model to obtain the potential species impact fraction (PAF). The risk values PAF of different rare earth elements in the soils of various regions in Ganzhou are shown in Table 10.

[0092] Table 10

[0093]

[0094]

[0095] The potential species impact fraction (msPAF) of the mixture of rare earth elements in the soils of various regions in Ganzhou is shown in Table 11.

[0096] Table 11

[0097]

[0098] Risk assessment was carried out on various regions in Ganzhou based on the risk value PAF of each rare earth element in the soil of Ganzhou. The ecological risks caused by 15 rare earth elements in the soil of Ganzhou were significantly different. Among the 15 rare earth elements, Ce, Nd, Eu, Gd, Y, and La showed medium risks, with risk values ranging from 0.001 to 0.1, indicating that these rare earth elements may affect 0.1 - 10% of the species; the risk values of Ce, Nd, and Eu were greater than 0.05, suggesting that they may have relatively serious ecological impacts; the risk values of Pr, Sm, Tb, Dy, Ho, Er, Tm, Yb, and Lu in the soil of most regions were less than 10 -3 even less than 10 -6 , indicating that these rare earth elements have little or certain potential ecological risks. Based on the exposure concentrations of rare earth elements in Ganzhou and the SSD, the msPAF was obtained. Ganzhou was at a medium ecological risk level, and this conclusion was consistent with PLI and RI.

[0099] The joint probability curve (JPC) is a curve representing the relationship between species and the environment constructed by combining the distribution functions of effect concentrations and exposure concentrations. The integral area under the JPC curve - the overall risk probability is a very valuable ecological risk indicator. The JPC curve was also drawn using the BMC - SSD software. The overall risk probability results (ORP) of different rare earth elements in the soil of various regions in Ganzhou are shown in Table 12.

[0100] Table 12

[0101]

[0102] The safety threshold (MOS 10 ) is the ratio of the 10th percentile of the toxicity data SSD to the 90th percentile of the cumulative probability distribution of the exposure data. The MOS 10 results of different rare earth elements in the soil of various regions in Ganzhou are shown in Table 13.

[0103] Table 13

[0104]

[0105] Combined with Tables 10 - 13, it can be seen that: the risk assessments of PAF, ORP, and MOS 10 for each rare earth element are generally consistent, and Ce, Nd, Eu, Gd, and Y all show relatively high ecological risks. Based on the probability ecological risk results PAF, ORP, and MOS 10 of environmental concentrations and toxicity data, the priorities of rare earth elements in the soil of Ganzhou were sorted. According to PAF, ORP, and MOS 10Select the top 25% of rare earth elements with the highest risks in descending order as the priority pollutants that should receive the most attention. The relevant ranking results are summarized in Table 14 below.

[0106] Table 14

[0107]

[0108] As can be seen from Table 14, Ce, Nd, and Y should be considered as the priority pollutants among the rare earth elements in various regions of Ganzhou.

[0109] As Figure 1 shown, in this embodiment, through the exposure concentrations and toxicity data of rare earth elements in the Ganzhou area collected previously, a probabilistic ecological risk assessment of rare earth elements is carried out. Combining the exposure concentrations and SSD models in the Ganzhou region, the PAF values of the corresponding regions can be obtained, and the ecological risk levels of rare earth elements in the Ganzhou region can be judged; through JPC, combining the exposure concentration distribution of rare earth elements and the SSD of rare earth elements in the Ganzhou region, the risk probabilities of the corresponding regions are obtained; finally, supplemented by MOS 10 evaluate the relative magnitudes of the ecological risks caused by rare earth elements in various places in Ganzhou, and finally determine the pollutants to be considered as priorities.

[0110] In the probabilistic ecological risk assessment, according to msPAF, Ganzhou is at a medium ecological risk level, and this conclusion is consistent with PLI and RI; according to PAF, Ce, Nd, Eu, Gd, La, and Y in the Ganzhou area have medium risks; then, taking the magnitudes of PAF, ORP, and MOS 10 as the priorities, it can be determined that the rare earth elements Ce, Nd, and Y should be considered as the priority pollutants among the rare earth elements in various regions of Ganzhou.

[0111] It can be seen that compared with the traditional assessment method that only uses screening assessment, the present invention couples semi-probabilistic risk assessment and probabilistic risk assessment on this basis, thereby obtaining the probability values of the regional soil ecological risks of rare earth elements, screening out the rare earth elements that should be prioritized in the region, and using the ecological risks of the prioritized rare earth elements to represent the comprehensive ecological risks of rare earth element mixtures. Compared with the quotient values obtained by screening assessment, using probability values to represent ecological risks is more scientific and accurate, and is convenient for subsequent risk management. This evaluation method from qualitative to quantitative more accurately reflects the ecological risks of regional rare earth pollution.

[0112] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. An assessment method for multi-level regional soil ecological risks, characterized in that, The described assessment method is based on regional rare earth exposure data and species toxicity data. Through mutually coupled screening risk assessment, semi-probabilistic risk assessment, and probabilistic risk assessment, the rare earth elements that require priority attention within the region are screened out, and the comprehensive ecological risk of the rare earth element mixture is represented by the ecological risk of the rare earth elements that require priority attention. The probabilistic risk assessment combines the exposure concentration distribution and the species sensitivity distribution. Through modeling, the soil ecological risks of each rare earth element and the overall rare earth elements are evaluated from a probabilistic perspective. The modeling process includes the following steps: (1) According to the environmental protection objectives and the species sensitivity distribution, obtain the ecological risk threshold of the rare earth element. (2) According to the exposure concentration and the species sensitivity distribution, obtain the potential species impact ratio as the risk value to evaluate the soil ecological risk of each rare earth element. (3) Using the effect addition model, according to the potential species impact ratio obtained in step (2), obtain the potential species impact ratio of the mixture as the risk value to evaluate the ecological risk of the overall rare earth elements. (4) Using the joint probability curve, combine the exposure concentration distribution and the species sensitivity distribution to calculate the overall risk probability and safety threshold. (5) Integrate the potential species impact ratio obtained in step (2) with the overall risk probability and safety threshold obtained in step (4) to screen out the rare earth elements that require priority attention within the region.

2. The evaluation method according to claim 1, wherein The regional rare earth exposure data includes the exposure concentration.

3. The evaluation method according to claim 2, wherein The screening risk assessment combines the regional geochemical baseline concentration and the exposure concentration to calculate the ecological risk index of each rare earth element, which is used to evaluate the soil ecological risks of each rare earth element and the overall rare earth elements.

4. The evaluation method according to claim 3, characterized in that The regional geochemical baseline concentration includes the background concentration.

5. The evaluation method according to claim 4, wherein The ecological risk index includes an exposure concentration-related index and an ecology-related index.

6. The evaluation method according to claim 5, wherein The calculation process of the exposure concentration-related index combines the background concentration and the exposure concentration.

7. The evaluation method according to claim 5, characterized in that The exposure concentration-related index includes any one or at least two combinations of the geoaccumulation index, pollution index, or pollution load index.

8. The evaluation method according to claim 5, characterized in that, The calculation process of the ecology-related index combines the toxicity coefficient and the exposure concentration.

9. The evaluation method according to claim 8, wherein The calculation of the toxicity coefficient is based on the Hakanson principle.

10. The evaluation method according to claim 5, characterized in that, The ecology-related index includes the potential ecological risk index and / or the potential ecological risk factor.

11. The evaluation method according to claim 1, wherein Based on the screening risk assessment, the semi-probabilistic risk assessment calculates the proportion of the ecological risk index of each rare earth element at different pollution levels.

12. The evaluation method according to claim 1, wherein The establishment of the exposure concentration distribution is based on the exposure concentration.

13. The evaluation method according to claim 1, wherein The establishment of the species sensitivity distribution is based on the species toxicity data.

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