Soil risk evaluation method for acid wastewater sediment pollution

Abstract

The invention discloses a soil risk evaluation method for acidic wastewater sediment pollution, and belongs to the technical field of soil risk evaluation, and the method specifically comprises the following steps: collecting a plurality of sequences of soil samples according to the distance from near to far from a pollution source; selecting a plurality of soil samples from each sequence, and measuring a humidity value H1; fitting a fitting function that the humidity values H of all the soil samples change along with the distance l according to the measured humidity values H1; calculating actual humidity values of all the soil samples based on the fitting function; calculating a humidity difference value between each actual humidity value H and the appropriate humidity value; according to the humidity difference value, the set air speed for reducing the actual humidity value to the appropriate humidity value within the set time t is calculated, and the air speed of the corresponding air drying device is controlled to be the set air speed; after reaching a set time length t, respectively measuring the pH value of each sequence of soil, and drawing an acid-base contour map of the polluted area according to the pH values; the accuracy and efficiency of soil acidity and alkalinity measurement are improved.

Description

Technical Field

[0001] The invention relates to the technical field of soil risk assessment, and in particular to a soil risk assessment method for acidic wastewater sludge pollution. Background Art

[0002] In modern industrial activities, wastewater sludge produced by mineral processing often contains a variety of heavy metal elements, which can cause serious pollution to the environment if not treated. In particular, when such wastewater sludge comes into contact with soil, heavy metals can enter the food chain through the soil, posing a potential threat to human health and the ecosystem. Therefore, risk assessment of soil heavy metal pollution caused by acidic mineral wastewater sludge is of great significance for environmental protection and human health. Traditional soil heavy metal pollution risk assessment methods usually rely on the collection and laboratory analysis of soil samples, and assess the degree of pollution by measuring the content of heavy metals in the soil.

[0003] The moisture content in the soil affects the concentration of hydrogen ions and hydroxide ions, thus affecting the pH of the soil; for neutral and acidic soils, the thinner the soil suspension, the higher the measured pH value. This is because the concentration of clay particles decreases, resulting in a decrease in the chance of adsorbed hydrogen ions contacting the electrode surface, and the dilution effect of the electrolyte causes more cations to dissolve in the solution, thereby increasing the pH value of the solution.

[0004] If the soil test sample absorbs too much water, or does not have enough water, the test results may be inaccurate. Therefore, when conducting soil pH tests, it is necessary to control the moisture of the test soil to avoid affecting the pH measurement. Summary of the invention

[0005] The purpose of the present invention is to provide a soil risk assessment method for acidic wastewater sludge contamination to solve the following technical problems: If the soil test sample absorbs too much water or not enough water, the test result will be inaccurate. Therefore, when conducting soil pH test, it is necessary to control the moisture of the test soil.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A soil risk assessment method for acidic wastewater sludge pollution comprises the following steps: Several sequences of soil samples were collected according to the distance from the pollution source from near to far. The distance of each sequence of soil samples from the pollution source l Arranged in an arithmetic sequence; Select several soil samples from each sequence and measure the humidity value. When the measured humidity value is higher than the appropriate humidity value of the test pH, the humidity of the soil sample is marked as H1; when the humidity value of the soil sample is lower than the appropriate humidity value of the test pH, add water to all the soil samples and select several soil samples again to measure the humidity and mark them as H1; According to the measured humidity value H1, the humidity value H of all soil samples is fitted with the distance l The fitting function is varied; the actual moisture values ​​of all soil samples are calculated based on the fitting function; Generate a sequence of actual humidity values, and calculate the humidity difference between each actual humidity value H and the appropriate humidity value H2; each soil sample corresponds to an air-drying device, and a set wind speed is calculated according to the humidity difference to reduce the actual humidity value to the appropriate humidity value within a set time t, and the wind speed of the corresponding air-drying device is controlled to be the set wind speed; When the set time t is reached, the pH value of the soil in each sequence is measured respectively, and the acid-base contour map of the contaminated area is drawn according to the pH value, and the abnormal pH is screened out and marked.

[0007] As a further solution of the present invention: the number of soil collection points in each sequence is N, the actual humidity value sequence of any array is obtained, and the actual humidity value sequence is fitted using the least squares parabola, and the parabola fitting function formulas are respectively: H=al 2 +bl+c ; Where H represents the actual humidity value, l represents the distance from the pollution source, then the solution formulas for a, b, and c are: ; ; ; where i∈[1,2,...,N].

[0008] As a further solution of the present invention: the process of calculating the set wind speed is: The humidity difference ΔH=H-H2. When the required humidity change per unit time t is ΔH, the formula for the final wind speed V0 required at any detection point is: , Wherein, S represents the cross-sectional area of ​​the air outlet corresponding to the air drying device, E represents the evaporation heat of water, T represents the temperature value of the corresponding soil sample, and f is the preset temperature correction coefficient; The calculation formula for the set wind speed V at the air outlet is: , Where e is the natural constant, d is the distance from the air outlet to the soil sample, and k is the correction coefficient.

[0009] As a further solution of the present invention: the output air volume Q of the air outlet is VS.

[0010] As a further solution of the present invention: the cross-sectional area S of the air outlet is the cross-sectional area of ​​the container where the soil sample is located.

[0011] As a further solution of the present invention: the collection point sequence of each sequence of soil samples is arranged circumferentially with the pollution source as the center.

[0012] As a further solution of the present invention: the process of screening abnormal pH is: Draw the curve F1 of the change of pH value with distance for each sequence, select the curve F2 in the relative direction of the sequence, overlap F1 and F2, extract the difference between the two pH values ​​corresponding to the same position, and if there are two pH values ​​with a difference greater than the threshold, obtain the slopes k1 and k2 of the tangents corresponding to the two pH coordinate points respectively, calculate the mean of the slopes of the tangents of the pH coordinate points adjacent to k1 and k2 respectively, and calculate the slope difference between k1 and k2 and the corresponding slope mean respectively. If there is a slope difference greater than the preset threshold, the corresponding pH value will be marked as an abnormal humidity value.

[0013] Beneficial effects of the present invention: (1) Traditional soil heavy metal pollution assessments often ignore the effect of humidity on pH testing. The present invention eliminates the error caused by humidity differences by accurately controlling the humidity of each soil sample, thereby improving the accuracy of pH measurement. Specifically, the wind speed and air volume of the corresponding air-drying device are accurately regulated according to the humidity difference of each soil sample, and the humidity of each soil sample is quickly adjusted to the same suitable test level, ensuring that all samples are tested for pH under the same humidity conditions, thereby improving the accuracy and efficiency of soil pH measurement. (2) The present invention collects several sequences of soil samples from near to far according to the distance from the pollution source, and the distance of each sequence of soil samples from the pollution source is arranged in an arithmetic sequence; this systematic sampling can comprehensively cover the pollution areas at different distances, ensure the representativeness and integrity of the data, and thus more accurately assess the scope and degree of pollution; the measured humidity values ​​are used to fit the function of the humidity values ​​of all soil samples changing with distance, and the actual humidity values ​​are calculated based on this; this data fitting and analysis method can reveal the regularity of humidity distribution and provide a scientific basis for the subsequent wind speed setting. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings.

[0015] Figure 1It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] See also Figure 1 As shown, the present invention is a soil risk assessment method for acidic wastewater sludge pollution, comprising the following steps: 1. Collect soil samples: Several sequences of soil samples were collected from near to far according to the distance from the pollution source. These sequences were arranged in an arithmetic sequence to ensure that the distance of the soil samples in each sequence from the pollution source was l This layout helps to systematically study the distribution and impact of pollutants at different distances.

[0018] 2. Measure humidity value: Several soil samples are selected from each sequence and their moisture values ​​are measured. When the measured moisture value is higher than the appropriate moisture value for testing pH, the moisture of the soil sample is marked as H1. This means that the moisture of the soil sample exceeds the optimal moisture condition required for pH testing.

[0019] If the humidity value of the soil sample is lower than the appropriate humidity value for the test pH, all soil samples need to be treated with water to ensure that the appropriate humidity conditions are reached. After adding water, select several soil samples again to measure the humidity and also mark them as H1.

[0020] 3. Fitting humidity value function: According to the measured humidity value H1, the humidity value H of all soil samples is fitted with the distance l This step uses a mathematical model to describe the trend of humidity changes with distance, providing a theoretical basis for subsequent humidity adjustments.

[0021] The actual moisture values ​​of all soil samples are calculated based on the fitting function. This helps to understand the actual moisture situation of each soil sample in its current state.

[0022] 4. Generate a sequence of humidity values: Generate a sequence of actual humidity values, and calculate the humidity difference between each actual humidity value H and the appropriate humidity value H2. By comparing the difference between the actual humidity value and the appropriate humidity value, the degree of adjustment required can be determined.

[0023] 5. Calculate the set wind speed: Each soil sample corresponds to an air drying device. The set wind speed that reduces the actual humidity value to the appropriate humidity value within the set time t is calculated based on the humidity difference. This calculation determines the necessary wind speed based on the humidity difference and the preset air drying time to ensure that the soil sample can reach the appropriate humidity condition within the specified time.

[0024] The wind speed of the corresponding air drying device is controlled to be the set wind speed. By accurately controlling the wind speed, the humidity of the soil sample can be effectively adjusted to meet the requirements of the pH test.

[0025] 6. Measure pH value and draw contour map: After the set time t is reached, the pH value of the soil in each sequence is measured. This step is carried out after the soil sample reaches a suitable moisture content in order to assess the acidity and alkalinity of the soil.

[0026] Draw the acid-base contour map of the polluted area according to the pH value. By connecting the pH values ​​of different sampling points, the distribution of pH in the polluted area can be intuitively displayed.

[0027] Screen out the abnormal pH values ​​and mark them. By identifying and marking the abnormal pH values, the impact of pollution sources and the pollution status of the soil can be further analyzed.

[0028] According to the above, soil samples are collected by arranging them in a distance arithmetic sequence, which fully covers areas at different distances from the pollution source, thereby improving the representativeness and accuracy of data collection. At the same time, by adjusting and controlling the humidity value in real time, it is ensured that the pH of the soil sample is measured under suitable humidity conditions, thereby improving the accuracy of the measurement results. By using the fitting function to calculate the actual humidity value, the humidity changes of the soil sample at different distances can be more accurately reflected, providing accurate data support for subsequent pH measurements. By drawing the acid-base contour map and screening the abnormal pH, the pH distribution of the polluted area can be intuitively displayed, which helps to timely discover and deal with abnormal areas and improve the effect of environmental protection.

[0029] In another preferred embodiment of the present invention, the number of soil collection points in each sequence is N, and the actual humidity value sequence of any array is obtained, and the actual humidity value sequence is fitted using a least squares parabola, and the parabola fitting function formulas are respectively: H=al 2 +bl+c ; Where H represents the actual humidity value, l represents the distance from the pollution source, a, b, c are the coefficients to be solved, and the solution formula for a, b, c is: ; ; ; where i∈[1,2,...,N], l i represents the distance between the ith sampling point and the pollution source, H i Represents the humidity value of the i-th sampling point. After calculating the three coefficients of the parabola through the above formula, we can get the fitting function of the humidity value changing with distance. This function can be used to accurately predict the soil moisture at different distances, thereby providing basic data for subsequent wind speed setting and pH value measurement.

[0030] According to the fitting function, the location and number of sampling points can be planned more reasonably to ensure that representative data is obtained throughout the study area, thereby improving the efficiency and accuracy of the entire risk assessment. The changes in soil moisture are monitored in real time, and the settings of the air drying device are adjusted as needed to maintain the best test conditions. This dynamic adjustment capability is particularly important for dealing with complex and changing environmental conditions.

[0031] Using least squares parabola fitting, the model can adapt to various nonlinear relationships and better capture the complex pattern of soil moisture variation with distance, providing a solid data basis for subsequent risk assessment. Compared with traditional point-by-point measurement and analysis, this method simplifies the data processing steps through mathematical models, reduces the possibility of manual intervention, and reduces the difficulty of operation and error rate.

[0032] In another preferred embodiment of the present invention, the process of calculating the set wind speed is: First, calculate the humidity difference ΔH=H-H2. The humidity difference represents the humidity change that needs to be adjusted. When the humidity change required per unit time t is ΔH, the formula for the final wind speed V0 required at any detection point is: , Wherein, S represents the cross-sectional area of ​​the air outlet corresponding to the air drying device, E represents the evaporation heat of water, that is, the heat absorbed by a unit mass of water when it is completely evaporated, T represents the temperature value of the corresponding soil sample, and the temperature affects the evaporation rate, and f is the preset temperature correction coefficient, which is used to adjust the change of the evaporation rate at different temperatures; According to the final wind speed V0 calculated by the above formula, the calculation formula for the set wind speed V of the air outlet can be further determined as follows: , Where e is a natural constant, d is the distance from the air outlet to the soil sample. The longer the distance, the greater the wind speed attenuation. k is a correction coefficient used to adjust the rate of wind speed attenuation. The output air volume of the air outlet is Q=VS.

[0033] By accurately calculating the required wind speed, soil samples can be quickly and effectively adjusted to the optimal test humidity, shortening preparation time and improving the efficiency of the entire assessment process. Ensuring that all soil samples are measured for pH under the same humidity conditions eliminates variability caused by humidity differences, thereby ensuring data consistency and comparability. Accurate humidity control helps to better understand the impact of humidity changes on soil pH, significantly improves the efficiency and accuracy of soil heavy metal pollution risk assessment, and has important practical significance for environmental protection and sustainable development.

[0034] In another preferred embodiment of the present invention, the collection point sequence of each sequence of soil samples is arranged circumferentially with the pollution source as the center to ensure comprehensive coverage of the entire polluted area and avoid missing areas that may be polluted. This method can capture pollution conditions at different distances and directions, thereby providing more complete data support. Through circumferential arrangement, the position and spacing of the sampling points can be more accurately controlled to ensure the consistency and comparability of the data. It is helpful to analyze the diffusion pattern of pollutants in different directions and understand the spatial distribution characteristics of pollution.

[0035] In another preferred embodiment of the present invention, the process of screening abnormal pH is: 1. Draw a curve: First, the pH curves of each sequence are plotted as a function of distance. These curves reflect the pH changes of different sampling points at different distances.

[0036] 2. Select the relative direction curve: Select the curve F2 of the relative direction of the sequence. The curve of the relative direction refers to another curve that is relative to the current curve in space and is used for comparison and analysis.

[0037] 3. Curve overlap: Overlap curve F1 with curve F2. By overlapping, the pH difference of the two curves at the same position can be intuitively compared.

[0038] 4. Extract the difference: Extract the difference between the two pH values ​​corresponding to the same position. Calculate the pH difference between F1 and F2 at each position to identify possible abnormal points.

[0039] 5. Set the threshold: If there are two pH values ​​with a difference greater than a preset threshold, it is considered that the two pH values ​​may be abnormal. The threshold is set based on experience and experimental data to distinguish between normal and abnormal pH differences.

[0040] 6. Get the slope: Obtain the slopes k1 and k2 of the tangent lines corresponding to the two pH coordinate points. The slope of the tangent line reflects the rate at which pH changes with distance and is an important indicator for determining abnormalities.

[0041] 7. Calculate the mean slope: Calculate the mean of the tangent slopes of the adjacent left and right pH coordinate points of k1 and k2. By calculating the mean of the slopes of adjacent points, a relatively stable slope reference value can be obtained.

[0042] 8. Calculate the slope difference: Calculate the slope difference between k1 and k2 and the corresponding slope mean. The slope difference reflects the difference between the current slope and the surrounding slopes.

[0043] 9. Determine abnormality: If there is a slope difference greater than the preset threshold, the corresponding pH value is marked as an abnormal humidity value. If the slope difference exceeds the threshold, it means that the pH change at this point is significantly different from that at other points, and there may be an abnormality.

[0044] By comparing the pH differences at the same location in different directions through the above steps, abnormal humidity values ​​can be effectively identified. This comparison method helps to find abnormal data points that may be caused by local environmental factors, thereby eliminating the impact of these abnormal values ​​on the overall evaluation results.

[0045] By calculating the tangent slope and its mean, and further analyzing the slope difference, this method can accurately locate the difference in the degree of diffusion of the pollution source in different directions. This helps to more accurately assess the scope and severity of the pollution. Understanding the diffusion of pollution in different directions can provide a basis for formulating targeted remediation strategies. For example, if the pollution diffusion in a certain direction is more serious, more intensive or deeper remediation measures may be required in that direction.

[0046] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A soil risk assessment method for acidic wastewater sludge contamination, characterized in that: The following steps are involved: Several sequences of soil samples were collected according to the distance from the pollution source from near to far. The distance of each sequence of soil samples from the pollution source l Arranged in an arithmetic sequence; Select several soil samples from each sequence and measure the humidity value. When the measured humidity value is higher than the appropriate humidity value of the test pH, the humidity of the soil sample is marked as H1; when the humidity value of the soil sample is lower than the appropriate humidity value of the test pH, add water to all the soil samples and select several soil samples again to measure the humidity and mark them as H1; According to the measured humidity value H1, the humidity value H of all soil samples is fitted with the distance l The fitting function is varied; the actual moisture values ​​of all soil samples are calculated based on the fitting function; Generate a sequence of actual humidity values, and calculate the humidity difference between each actual humidity value H and the appropriate humidity value H2; each soil sample corresponds to an air-drying device, and a set wind speed is calculated according to the humidity difference to reduce the actual humidity value to the appropriate humidity value within a set time t, and the wind speed of the corresponding air-drying device is controlled to be the set wind speed; When the set time t is reached, the pH value of the soil in each sequence is measured respectively, and the acid-base contour map of the contaminated area is drawn according to the pH value, and the abnormal pH is screened out and marked.

2. The soil risk assessment method for acidic wastewater sludge contamination according to claim 1 is characterized in that: The number of soil collection points in each sequence is N. The actual humidity value sequence of any array is obtained, and the actual humidity value sequence is fitted using the least squares parabola. The parabola fitting function formulas are: H=al 2 +bl+c ； Where H represents the actual humidity value, l represents the distance from the pollution source, then the solution formulas for a, b, and c are: ； ； ； where i∈[1,2,...,N].

3. The soil risk assessment method for acidic wastewater sludge contamination according to claim 2 is characterized in that: The process of calculating the set wind speed is: The humidity difference ΔH=H-H2. When the required humidity change per unit time t is ΔH, the formula for the final wind speed V0 required at any detection point is: ； Wherein, S represents the cross-sectional area of ​​the air outlet corresponding to the air drying device, E represents the evaporation heat of water, T represents the temperature value of the corresponding soil sample, and f is the preset temperature correction coefficient; The calculation formula for the set wind speed V at the air outlet is: ； Where e is the natural constant, d is the distance from the air outlet to the soil sample, and k is the correction coefficient.

4. The soil risk assessment method for acidic wastewater sludge contamination according to claim 3 is characterized in that: The output air volume of the air outlet is Q=VS.

5. The soil risk assessment method for acidic wastewater sludge contamination according to claim 3 is characterized in that: The cross-sectional area S of the air outlet is the cross-sectional area of ​​the container where the soil sample is located.

6. The soil risk assessment method for acidic wastewater sludge contamination according to claim 1 is characterized in that: The collection point sequence of each sequence of soil samples is arranged circumferentially with the pollution source as the center.

7. The soil risk assessment method for acidic wastewater sludge contamination according to claim 6 is characterized in that: The process of screening for abnormal pH is: Draw the curve F1 of the change of pH value with distance for each sequence, select the curve F2 in the relative direction of the sequence, overlap F1 and F2, extract the difference between the two pH values ​​corresponding to the same position, and if there are two pH values ​​with a difference greater than the threshold, obtain the slopes k1 and k2 of the tangents corresponding to the two pH coordinate points respectively, calculate the mean of the slopes of the tangents of the pH coordinate points adjacent to k1 and k2 respectively, and calculate the slope difference between k1 and k2 and the corresponding slope mean respectively. If there is a slope difference greater than the preset threshold, the corresponding pH value will be marked as an abnormal humidity value.

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