Ultrasonic rapid determination method for mercury, arsenic, copper, zinc, lead and cadmium in soil

Abstract

The invention provides an ultrasonic rapid determination method for mercury, arsenic, copper, zinc, lead and cadmium in soil, and relates to the technical field of detection of heavy metal elements in a soil environment, and the operation steps of the method are as follows: weighing [0.1, 1.0] g of a soil sample, placing the soil sample in a digestion container, adding a digestion solution in which the volume ratio of nitric acid to hydrochloric acid is (3-5): 1 and the mass of the digestion solution is (8-15) times that of the sample, carrying out [10, 30] mi n ultrasonic treatment by [20, 50] kHz and [200, 500] W, stirring [1, 3] mi n every [3, 8] mi n during the period, then heating to [120, 1.0] m < 2 >, and carrying out ultrasonic treatment by using the digestion solution; the method comprises the following steps: carrying out digestion at 180 DEG C for [1, 3] h, heating at a heating rate of [5, 10] DEG C / min, cooling to a constant volume of [20, 50] mL, determining by using an atomic absorption spectrometer or an inductively coupled plasma mass spectrometer, determining by using an atomic absorption spectrometer or an inductively coupled plasma mass spectrometer, selecting internal standard elements such as scandium, and the concentration of an internal standard solution of [10, 50] [mu] g / L, and clearly stipulating standard curve drawing, detection limit, recovery rate and the like. The method is simple and convenient to operate, rapid in determination, accurate and sensitive, can effectively determine the content of various heavy metals in soil, and provides powerful support for soil quality evaluation and pollution abatement.

Description

Technical Field

[0001] The present invention belongs to the technical field of detecting heavy metal elements in the soil environment. More specifically, it particularly relates to a method for rapidly determining mercury, arsenic, copper, zinc, lead, and cadmium in the soil by ultrasound. Background Art

[0002] As an important part of the ecosystem, the quality of the soil is directly related to ecological balance, agricultural production, and human health. In the assessment of soil quality, the determination of heavy metal content is a key indicator. The excessive accumulation of heavy metal elements such as mercury, arsenic, copper, zinc, lead, and cadmium in the soil will pose a serious threat to the soil ecosystem and human health.

[0003] With the acceleration of industrialization and urbanization processes and the extensive use of agricultural chemicals, the problem of soil heavy metal pollution has become increasingly prominent. Accurately and rapidly determining the content of these heavy metal elements in the soil is of great significance for timely understanding the soil pollution status, formulating reasonable soil remediation strategies, and ensuring the safety of agricultural products.

[0004] However, traditional methods for determining heavy metals in the soil often have many limitations. For example, some methods require complex sample pretreatment processes, including long-term high-temperature digestion, multiple reagent additions, and filtration operations, etc. This not only takes time and effort but also easily leads to sample loss and contamination, affecting the accuracy of the determination results.

[0005] Common digestion methods such as dry digestion and wet digestion. Dry digestion usually requires a high-temperature furnace device, with harsh operating conditions and is prone to the loss of some volatile elements; wet digestion often uses a strong acid system, with violent reactions, high risks, and there are also problems of incomplete digestion.

[0006] In the determination process, traditional instrumental analysis methods such as atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS), etc., although having high accuracy, often have the disadvantages of long analysis time, relatively high detection limits, expensive instruments, and high maintenance costs.

[0007] In addition, when traditional methods are used to determine multiple heavy metal elements, different pretreatment and determination steps may be required respectively, increasing the complexity and workload of the operation. Moreover, for some heavy metal elements with low contents, the detection sensitivity of traditional methods often cannot meet the requirements, easily leading to missed detections or misjudgments.

[0008] Therefore, in order to meet the urgent needs of soil pollution monitoring and treatment, there is an urgent need to develop a method for determining heavy metals in soil that is simple to operate, fast, efficient, accurate, sensitive and low-cost. Based on this background, the present invention proposes a method for rapidly determining mercury, arsenic, copper, zinc, lead and cadmium in soil by ultrasound, aiming to overcome the deficiencies of traditional methods and provide more powerful technical support for soil environmental monitoring and quality assessment. Summary of the Invention

[0009] In order to solve the above technical problems, the present invention provides a method for rapidly determining mercury, arsenic, copper, zinc, lead and cadmium in soil by ultrasound to solve the above problems.

[0010] The method for rapidly determining mercury, arsenic, copper, zinc, lead and cadmium in soil by ultrasound includes the following steps:

[0011] S1: Weigh a soil sample within a certain mass range, and the mass range is [0.1, 1.0] g;

[0012] S2: Place the soil sample in a digestion container, and add a certain volume of digestion solution. The digestion solution is a mixed solution of nitric acid and hydrochloric acid, where the volume ratio of nitric acid to hydrochloric acid is (3 - 5):1, and the added volume of the digestion solution is 8 - 15 times the mass of the soil sample;

[0013] S3: Perform ultrasonic treatment on the digestion container, with an ultrasonic frequency of [20, 50] kHz, an ultrasonic power of [200, 500] W, and an ultrasonic time of [10, 30] min;

[0014] S4: After the ultrasonic treatment, heat the digestion solution to a certain temperature for digestion. The temperature range is [120, 180] °C, and the digestion time is [1, 3] h;

[0015] S5: After digestion is completed, cool to room temperature and make up the volume to a certain volume. The volume range is [20, 50] mL;

[0016] S6: Use an atomic absorption spectrometer or an inductively coupled plasma mass spectrometer to determine the contents of mercury, arsenic, copper, zinc, lead and cadmium in the solution.

[0017] Preferably, the concentration of nitric acid is [65,68]%, and the concentration of hydrochloric acid is [36,38]%. Nitric acid and hydrochloric acid in a specific concentration range can effectively decompose various organic and inorganic components in soil samples, so that heavy metal elements such as mercury, arsenic, copper, zinc, lead, and cadmium are fully released to achieve the purpose of accurate determination. The appropriate acid concentration can ensure that the digestion reaction is carried out at an appropriate intensity, which can not only fully digest the sample, but also avoid excessive reaction leading to sample loss or dangerous situations. By limiting the concentration range of these two acids, more optimized experimental conditions can be determined, so that the determination method can obtain more reliable and consistent results in different laboratories and operating environments. The appropriate concentration of acid can reduce the interference of impurities, making the instrument more accurate and sensitive in detecting the target heavy metal elements during the determination process.

[0018] Preferably, during the ultrasonic treatment process, the digestion container is stirred at regular intervals, wherein the stirring interval is [3,8] min and the stirring time is [1,3] min, which helps to make the soil sample contact the digestion solution more fully and evenly, avoid incomplete local digestion, and thus ensure that the heavy metals in the entire sample can be effectively digested, thereby improving the uniformity and completeness of the digestion. Stirring can break the local stable area that may be produced by ultrasound, so that ultrasound can act more effectively on the entire digestion system, improve the digestion efficiency, reduce the difference in the degree of digestion of different parts, make the digestion effects of different batches of experiments and different samples in the same batch more consistent, and improve the repeatability and accuracy of the measurement results. Through appropriate stirring intervals and stirring times, the progress of the digestion reaction can be better controlled, so that the digestion is carried out under more optimized conditions, and achieve better digestion effects.

[0019] Preferably, during the heating digestion process, the heating rate is controlled to be [5,10]℃ / min. The slow and steady heating rate can prevent the digestion solution from boiling violently or splashing due to too fast heating, reduce potential safety risks, and avoid harm to operators. The appropriate heating rate helps to gradually decompose the components in the soil sample, avoiding incomplete digestion due to some components not having enough time to react due to too fast heating, or too long digestion time due to too slow heating, thereby ensuring sufficient and effective digestion. The steady heating process can reduce the volatilization or loss of the sample caused by sudden temperature changes, ensure that the heavy metal elements can be completely retained in the digestion solution, and improve the accuracy of the measurement results. The standardized heating rate helps to keep the digestion conditions of each experiment consistent, thereby improving the reproducibility and reliability of the measurement results, and making the experimental results of different batches comparable.

[0020] Preferably, the solvent used for volume fixation is deionized water or ultrapure water, which contains almost no impurity ions such as metal ions and anions. Using such water for volume fixation can avoid introducing additional impurities, thus ensuring the accuracy of the measurement results. It will not affect the detection of target heavy metal elements due to the impurities in the volume fixation solvent, and helps to maintain the purity of the solution after digestion. When using an instrument for subsequent measurement, it will not generate interference signals or affect the reaction process due to the impurities in the solvent. Pure water can reduce the pollution and damage to the measuring instrument (such as atomic absorption spectrometer or inductively coupled plasma mass spectrometer), extend the service life of the instrument, and ensure the normal operation and measurement accuracy of the instrument.

[0021] Preferably, the wavelengths for the determination of mercury, arsenic, copper, zinc, lead, and cadmium by atomic absorption spectrometer are as follows:

[0022] Mercury [253.7, 254.0] nm, arsenic [193.7, 194.0] nm, copper [324.7, 325.0] nm, zinc [213.9, 214.0] nm, lead [283.3, 283.5] nm, cadmium [228.8, 229.0] nm. Selecting these specific wavelength ranges can enable the atomic absorption spectrometer to have higher detection sensitivity for the corresponding elements, which helps to more accurately detect these heavy metal elements at low concentrations. The specific wavelength can reduce the interference of other elements or substances, enabling the instrument to more precisely capture the absorption signal of the target element, thereby improving the accuracy of the measurement results. The unified wavelength range helps to obtain relatively consistent measurement results under different laboratory and different instrument conditions, enhancing the universality and comparability of the method.

[0023] Preferably, when using an inductively coupled plasma mass spectrometer to determine mercury, arsenic, copper, zinc, lead, and cadmium, one or more of scandium, rhodium, and indium are selected as internal standard elements, and the concentration of the internal standard solution is [10, 50] μg / L.

[0024] Preferably, during the measurement process, the detection limit of the instrument satisfies the following formula: Where L is the detection limit, σ is the standard deviation of multiple measurements of the blank solution, and S is the slope of the standard curve.

[0025] Preferably, the standard curve is drawn using a series of standard solutions with a concentration range of mercury [0.01, 1.0] μg / L, arsenic [0.1, 5.0] μg / L, copper [0.5, 50.0] μg / L, zinc [0.5, 50.0] μg / L, lead [0.1, 50.0] μg / L, and cadmium [0.01, 1.0] μg / L.

[0026] Preferably, the relative standard deviation of the measurement results is less than [5,10]%, and the spike recovery rate is between [80,120]%, indicating that the degree of dispersion of the measurement results is small, the data repeatability is good, indicating that the experimental method has high stability and repeatability, increasing the credibility of the measurement results, reflecting that the measurement method can provide relatively consistent results in multiple measurements, and helping to accurately evaluate the heavy metal content in the soil.

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

[0028] 1. Significantly shorten the measurement time: The traditional method for measuring heavy metals in soil usually takes several hours or even longer to complete the entire measurement process. However, the present invention optimizes the digestion and treatment steps, such as using ultrasonic treatment combined with specific heating digestion conditions, greatly improving the work efficiency. Taking Example 1 as an example, it only takes 45 minutes to complete the entire measurement; Example 2 takes about 55 minutes; Example 3 takes about 65 minutes. Compared with the traditional method, the measurement time is significantly shortened, providing convenience for obtaining soil heavy metal content data in a timely manner and helping to make relevant decisions quickly.

[0029] 2. Improve the detection sensitivity and accuracy: The method of the present invention significantly reduces the detection limits of various elements. In Example 1, the detection limit of mercury is as low as 0.005 μg / L, arsenic is 0.05 μg / L, copper is 0.1 μg / L, zinc is 0.1 μg / L, lead is 0.05 μg / L, and cadmium is 0.005 μg / L. Similar low detection limit effects are also shown in Example 2 and Example 3. This means that trace heavy metal elements in the soil can be detected more precisely, and even in the case of extremely low content, they can be accurately measured, thus more accurately evaluating the pollution degree and potential risks of the soil.

[0030] 3. Enhance the repeatability and stability of the measurement results: It can be seen from the data of the relative standard deviation (RSD) that the repeatability of the measurement results of the present invention is good. The RSD of Example 1 is 3.5%, that of Example 2 is 2.8%, and that of Example 3 is 2.2%, all of which are less than the set 5-10%. This indicates that under the same experimental conditions, the differences between the results of multiple repeated measurements are small, and the data is reliable, providing a stable and reliable basis for soil quality assessment.

[0031] 4. Ensure an ideal spike recovery rate: The spike recovery rate is an important indicator for evaluating the accuracy of the measurement method. In the present invention, the spike recovery rate of Example 1 is between 90-110%, that of Example 2 is between 85-115%, and that of Example 3 is between 80-120%, all within the ideal range of 80-120%. This indicates that the loss of heavy metal elements during the measurement process is less, and the measurement results can accurately reflect the actual heavy metal content in the soil, ensuring the accuracy and reliability of the measurement method.

[0032] 5. Wide range of applications: By adjusting the mass of the soil sample, the dosage and ratio of the digestion solution, ultrasonic and heating parameters, etc., the present invention can adapt to soil samples of different types and contents. Whether it is farmland soil with low heavy metal content or industrial area soil with heavy pollution, accurate determination can be achieved, providing a general and effective means for the monitoring and evaluation of various soil environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the determination process of the present invention;

[0034] Figure 2 is a schematic diagram of the components of the digestion solution in the present invention;

[0035] Figure 3 is a schematic diagram of the steps of S3 in the present invention;

[0036] Figure 4 is a schematic diagram of the components of the solvent used in S5 of the present invention;

[0037] Figure 5 is a schematic diagram of the wavelengths for the determination of mercury, arsenic, copper, zinc, lead, and cadmium by atomic absorption spectrometer in the present invention;

[0038] Figure 6 is a schematic diagram of the experimental materials in the present invention;

[0039] Figure 7 is a schematic diagram of the experimental equipment in the present invention;

[0040] Figure 8 is a schematic diagram of the experimental steps in the present invention;

[0041] Figure 9 is the present invention Figure 6 in the schematic diagram of the components of the reference material and reagent;

[0042] Figure 10 is the schematic diagram of the concentration range used for the drawing of the standard curve in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0044] Please refer to Figures 1 - 10 , the contents of elements such as mercury, arsenic, copper, zinc, lead, and cadmium in the soil are of great significance for evaluating soil quality and environmental health. Traditional determination methods are often complex in operation and time-consuming. The ultrasonic rapid determination method provided by the present invention aims to improve the determination efficiency and accuracy, providing strong support for soil pollution monitoring and treatment.

[0045] 1. Experimental materials and equipment:

[0046] Experimental materials:

[0047] Soil samples: Collected from farmlands, industrial areas, and urban green belts in different regions respectively, and after pretreatment such as air-drying, grinding, and sieving, they are stored for later use.

[0048] Reference materials: Standard solutions of mercury, arsenic, copper, zinc, lead, and cadmium, and the concentration range is selected according to the regulations in the claims.

[0049] Reagents: Nitric acid (concentration [65, 68]%), hydrochloric acid (concentration [36, 38]%), deionized water or ultrapure water, internal standard element solutions (such as scandium, rhodium, indium).

[0050] Experimental equipment:

[0051] Electronic balance: With a precision of 0.0001 g, used to accurately weigh soil samples.

[0052] Ultrasonic cleaner: Frequency range [20, 50] kHz, power range [200, 500] W.

[0053] Hot plate: Can control the heating temperature and heating rate.

[0054] Atomic absorption spectrometer: Has the function of measuring mercury, arsenic, copper, zinc, lead, and cadmium, and can set the corresponding wavelengths.

[0055] Inductively coupled plasma mass spectrometer: Can be used for elemental analysis and can add internal standard elements.

[0056] Glassware such as volumetric flasks and pipettes.

[0057] 2. Experimental procedures:

[0058] Weighing of soil samples: Accurately weigh 0.1 g, 0.5 g, and 1.0 g of soil samples respectively, three portions each, accurate to 0.0001 g.

[0059] Addition of digestion solution: According to the mass of the weighed soil samples, add the corresponding volume of digestion solution (the volume ratio of nitric acid to hydrochloric acid is (3 - 5):1) at a ratio of (8 - 15) times the mass ratio of the digestion solution to the soil sample.

[0060] Ultrasonic treatment: Place the digestion container in the ultrasonic cleaner for ultrasonic treatment, and set the ultrasonic frequency, power, and time. Stir the digestion container every [3, 8] minutes, and the stirring time is [1, 3] minutes.

[0061] Heating digestion: After the ultrasonic treatment, the digestion solution is heated on a hot plate to [120, 180] °C for a digestion time of [1, 3] h, and the heating rate is controlled at [5, 10] °C / min.

[0062] Cooling and volume fixation: After digestion is completed, it is cooled to room temperature and fixed to [20, 50] mL with deionized water or ultrapure water.

[0063] Instrument determination:

[0064] Determination by atomic absorption spectrometer: Set the determination wavelengths of mercury, arsenic, copper, zinc, lead, and cadmium, and determine the content of each element in the solution respectively.

[0065] Determination by inductively coupled plasma mass spectrometer: Select one or more of scandium, rhodium, and indium as internal standard elements, add the internal standard solution, and determine the content of each element.

[0066] Example 1:

[0067] Weigh 0.1 g of soil sample, accurate to 0.0001 g.

[0068] Add 0.8 mL of digestion solution (volume ratio of nitric acid to hydrochloric acid is 3:1).

[0069] The ultrasonic frequency is set to 20 kHz, the power is 200 W, the ultrasonic time is 10 min, the stirring interval time is 3 min, and the stirring time is 1 min.

[0070] The heating digestion temperature is 120 °C, the digestion time is 1 h, and the heating rate is 5 °C / min.

[0071] After cooling, it is fixed to 20 mL.

[0072] Determination is carried out using an atomic absorption spectrometer. The wavelength of mercury is 253.7 nm, the wavelength of arsenic is 193.7 nm, the wavelength of copper is 324.7 nm, the wavelength of zinc is 213.9 nm, the wavelength of lead is 283.3 nm, and the wavelength of cadmium is 228.8 nm.

[0073] Example 2:

[0074] Weigh 0.5 g of soil sample, accurate to 0.0001 g.

[0075] Add 4 mL of digestion solution (volume ratio of nitric acid to hydrochloric acid is 4:1).

[0076] The ultrasonic frequency is set to 35 kHz, the power is 350 W, the ultrasonic time is 20 min, the stirring interval time is 5 min, and the stirring time is 2 min.

[0077] The heating digestion temperature is 150 °C, the digestion time is 2 h, and the heating rate is 7 °C / min.

[0078] Make up the volume to 35 mL after cooling.

[0079] Determine using an inductively coupled plasma mass spectrometer. The internal standard element is scandium, and the concentration of the internal standard solution is 20 μg / L.

[0080] Example 3:

[0081] Weigh 1.0 g of soil sample to an accuracy of 0.0001 g.

[0082] Add 12 mL of digestion solution (volume ratio of nitric acid to hydrochloric acid is 5:1).

[0083] Set the ultrasonic frequency to 50 kHz, the power to 500 W, the ultrasonic time to 30 min, the stirring interval time to 8 min, and the stirring time to 3 min.

[0084] The heating digestion temperature is 180 °C, the digestion time is 3 h, and the heating rate is 10 °C / min.

[0085] Make up the volume to 50 mL after cooling.

[0086] Determine using an atomic absorption spectrometer. The wavelength of mercury is 254.0 nm, the wavelength of arsenic is 194.0 nm, the wavelength of copper is 325.0 nm, the wavelength of zinc is 214.0 nm, the wavelength of lead is 283.5 nm, and the wavelength of cadmium is 229.0 nm.

[0087] To verify the advantages of the method of the present invention, the following comparative examples are set:

[0088] Treat the same soil sample according to the traditional digestion method (without ultrasonic treatment), and other steps are the same as those of the method of the present invention.

[0089] Experimental example:

[0090] Carry out a comparative analysis on the measurement results of the above Examples 1 - 3 and the comparative examples, including indicators such as measurement time, detection limit, relative standard deviation, and spike recovery rate. The results are shown in the following table:

[0091]

[0092] It can be seen from the data in the above table that the ultrasonic rapid determination method of the present invention is significantly shorter than the traditional method in terms of measurement time, and also shows better performance in terms of detection limit, relative standard deviation, and spike recovery rate.

[0093] The differences between Examples 1, 2, and 3 are mainly reflected in the following aspects:

[0094] First, different masses of soil samples were weighed. In Example 1, 0.1 g of soil sample was weighed; in Example 2, 0.5 g; and in Example 3, 1.0 g. This was to investigate the effects of different sample amounts on the measurement results and digestion effects.

[0095] Secondly, there were differences in the dosage and ratio of the digestion solution. As the sample mass increased, the dosage of the digestion solution also increased accordingly to ensure sufficient digestion. At the same time, the volume ratio of nitric acid to hydrochloric acid also varied in different examples to explore the effects of different acid ratios on the digestion effect and element determination.

[0096] Furthermore, the parameters of ultrasonic treatment were different, including ultrasonic frequency, power, and time, as well as the stirring interval and stirring time. This helped to study the effects of different ultrasonic conditions on the digestion process and element dissolution.

[0097] Also, there were differences in the temperature, time, and heating rate of heating digestion. By changing these parameters, the effects on the degree of complete digestion and the accuracy of the measurement results were observed.

[0098] The purpose of setting these three examples was as follows:

[0099] To comprehensively and systematically investigate the effects and feasibility of the proposed measurement method of the present invention under different experimental conditions. Through the combined study of different sample amounts, digestion solution conditions, ultrasonic parameters, and heating digestion parameters, the influence laws of various factors on the determination of mercury, arsenic, copper, zinc, lead, and cadmium in soil can be understood more deeply.

[0100] To provide a wider reference for practical applications. Soils in different regions and of different types may have significant differences in quality and composition. Through these three examples, a relatively wide range of sample situations can be covered, enabling the present measurement method to have better adaptability and reliability when facing various actual soil samples.

[0101] To optimize the experimental conditions. By comparing the results of the three examples, the optimal or relatively optimal combination of experimental parameters can be determined, providing a more efficient and accurate operation guide for subsequent measurement work.

[0102] To verify the stability and repeatability of the method. The results of multiple examples can confirm each other, better proving the stability and repeatability of the measurement method of the present invention and enhancing its credibility and practicality in actual applications.

[0103] The present invention proposes an innovative ultrasonic rapid measurement method for mercury, arsenic, copper, zinc, lead, and cadmium in soil, aiming to solve the problems of complex operation and long time consumption in traditional soil heavy metal measurement methods, and providing a more efficient and accurate technical means for soil environmental monitoring and pollution control.

[0104] This method first accurately weighs a certain mass range (0.1 - 1.0 g) of soil samples into a digestion container. By adding a digestion solution with a specific volume ratio (3 - 5:1 of nitric acid to hydrochloric acid) and amount (8 - 15 times the mass of the soil sample), it provides a suitable chemical environment for the subsequent digestion process.

[0105] Next, using the key step of ultrasonic treatment, it is treated at a specific ultrasonic frequency (20 - 50 kHz) and power (200 - 500 W) for 10 - 30 minutes, which greatly improves the digestion efficiency. And during the ultrasonic process, stirring is carried out for 1 - 3 minutes every 3 - 8 minutes, promoting the full contact and reaction between the sample and the digestion solution.

[0106] Subsequently, heating digestion is carried out. The digestion solution is heated to 120 - 180 °C and digested for 1 - 3 hours, controlling the heating rate at 5 - 10 °C / min to fully dissolve the heavy metal elements in the soil sample. After digestion, it is cooled to room temperature and made up to a volume of 20 - 50 mL.

[0107] In the determination step, an atomic absorption spectrometer or an inductively coupled plasma mass spectrometer can be used. When using an atomic absorption spectrometer to determine mercury, arsenic, copper, zinc, lead, and cadmium, specific wavelengths need to be set, while when using an inductively coupled plasma mass spectrometer for determination, appropriate internal standard elements (such as one or more of scandium, rhodium, and indium) and internal standard solution concentrations (10 - 50 μg / L) need to be selected.

[0108] To ensure the accuracy and reliability of the determination results, this invention also defines the drawing range of the standard curve, such as 0.01 - 1.0 μg / L for mercury, 0.1 - 5.0 μg / L for arsenic, etc., as well as the calculation formula for the detection limit of the instrument (L = 3×σ / S). At the same time, it is required that the relative standard deviation of the determination results is less than 5 - 10%, and the spike recovery rate is between 80 - 120%.

[0109] To comprehensively verify the effectiveness and superiority of the method of this invention, three examples are set. Example 1 uses a smaller amount of soil sample (0.1 g), lower ultrasonic and heating parameters. Example 2 is at a medium level in terms of sample amount (0.5 g) and experimental parameters. Example 3 uses a larger sample amount (1.0 g) and higher ultrasonic and heating conditions. Through the systematic study of these three examples, the influence of different experimental conditions on the determination results can be clearly seen.

[0110] Compared with traditional measurement methods, the advantages of the present invention are significant. First, the measurement time is greatly shortened, from several hours or even longer in the traditional method to dozens of minutes. Second, the detection limit is significantly reduced, the sensitivity of the measurement is improved, and trace heavy metal elements in the soil can be detected more accurately. Moreover, the relative standard deviation is small, indicating good repeatability and stability of the measurement results. The spiked recovery rate is within the ideal range, ensuring the accuracy of the measurement results.

[0111] The method of the present invention is easy to operate, has low requirements for experimental equipment, and is easy to popularize and apply in various laboratories. By optimizing the digestion and measurement conditions, the contents of mercury, arsenic, copper, zinc, lead, and cadmium in the soil can be measured quickly and accurately, providing strong technical support for soil quality assessment and environmental protection. This not only helps to understand the soil pollution status in a timely manner, but also provides a scientific basis for formulating corresponding treatment measures, which is of great significance for ensuring ecological environment safety and human health.

[0112] The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limit the invention to the disclosed form. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to better explain the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A rapid ultrasonic determination method for mercury, arsenic, copper, zinc, lead and cadmium in soil, characterized in that: The following steps are involved: S1: Weigh soil samples within a certain mass range, the mass range is [0.1, 1.0] g; S2: placing the soil sample in a digestion container, adding a certain volume of digestion solution, wherein the digestion solution is a mixture of nitric acid and hydrochloric acid, wherein the volume ratio of nitric acid to hydrochloric acid is (3-5):1, and the added volume of the digestion solution is 8-15 times the mass of the soil sample; S3: The digestion container was subjected to ultrasonic treatment, with an ultrasonic frequency of [20,50]kHz, an ultrasonic power of [200,500]W, and an ultrasonic time of [10,30]min; S4: After the ultrasonic treatment, the digestion solution is heated to a certain temperature for digestion, the temperature range is [120, 180] °C, and the digestion time is [1, 3] h; S5: After digestion is completed, cool to room temperature and adjust to a certain volume, the volume range is [20,50] mL; S6: Use atomic absorption spectrometer or inductively coupled plasma mass spectrometer to determine the content of mercury, arsenic, copper, zinc, lead and cadmium in the solution.

2. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: The concentration of the nitric acid is [65,68]%, and the concentration of the hydrochloric acid is [36,38]%.

3. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: During the ultrasonic treatment, the digestion container was stirred at regular intervals, wherein the stirring interval was [3,8] min and the stirring time was [1,3] min.

4. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: During the heating digestion process, the heating rate was controlled at [5,10]℃ / min.

5. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: The solvent used for volume adjustment is deionized water or ultrapure water.

6. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: The wavelengths of mercury, arsenic, copper, zinc, lead and cadmium determined by atomic absorption spectrometer are: Mercury [253.7, 254.0]nm, arsenic [193.7, 194.0]nm, copper [324.7, 325.0]nm, zinc [213.9, 214.0]nm, lead [283.3, 283.5]nm, cadmium [228.8, 229.0]nm.

7. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: When mercury, arsenic, copper, zinc, lead and cadmium are determined by inductively coupled plasma mass spectrometry, the internal standard elements are selected as one or more combinations of scandium, rhodium and indium, and the concentration of the internal standard solution is [10,50] μg / L.

8. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: During the determination process, the detection limit of the instrument satisfies the following formula: Where L is the detection limit, σ is the standard deviation of multiple measurements of the blank solution, and S is the slope of the standard curve.

9. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 8, characterized in that: The standard curve is drawn using a series of standard solutions with concentration ranges of mercury [0.01, 1.0] μg / L, arsenic [0.1, 5.0] μg / L, copper [0.5, 50.0] μg / L, zinc [0.5, 50.0] μg / L, lead [0.1, 50.0] μg / L, and cadmium [0.01, 1.0] μg / L.

10. The method for rapid ultrasonic determination of mercury, arsenic, copper, zinc, lead and cadmium in soil according to claim 1, characterized in that: The relative standard deviation of the determination results is less than [5,10]%, and the spiked recovery is between [80,120]%.

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