阅读说明：本技术 一种土壤金属物质的现场检测方法 (On-site detection method for soil metal substances ) 是由 张亚国 钟杰玲 郑丹霞 陈金松 杨振雄 黄思华 黄敏杏 于 2020-12-21 设计创作，主要内容包括：本发明涉及土壤检测技术领域,公开了一种土壤金属物质的现场检测方法,包括以下步骤,S1,采集土壤样品,测量土壤样品中的水分的质量分数,判断水分的质量分数是否大于1％,如果大于1％,进入步骤S2,否则,进入步骤S3；S2,对土壤样品进行烘干,直至土壤样品的水分的质量分数不大于1％,进入步骤S3；S3,对土壤样品进行焙烧,直至土壤样品的质量恒定；S4,对步骤S3中的土壤样品在粉碎机内进行粉碎、研磨、过滤；S5,对土壤样品进行压实处理,制取试样压片,利用X射线荧光光谱仪对试样压片进行检测。采用不同的方式消除样品的颗粒效应、矿物效应、均匀性等影响,提高土壤样品的制作精度,从而提高使用X射线荧光分析土壤金属物质时的准确性。(The invention relates to the technical field of soil detection, and discloses a field detection method of soil metal substances, which comprises the following steps of S1, collecting a soil sample, measuring the mass fraction of water in the soil sample, judging whether the mass fraction of the water is more than 1%, if so, entering S2, and if not, entering S3; s2, drying the soil sample until the mass fraction of the water in the soil sample is not more than 1%, and entering the step S3; s3, roasting the soil sample until the quality of the soil sample is constant; s4, crushing, grinding and filtering the soil sample in the step S3 in a crusher; and S5, compacting the soil sample to prepare a test sample tablet, and detecting the test sample tablet by using an X-ray fluorescence spectrometer. The method adopts different modes to eliminate the influences of particle effect, mineral effect, uniformity and the like of the sample, and improves the manufacturing precision of the soil sample, thereby improving the accuracy when the X-ray fluorescence is used for analyzing the soil metal substances.)

1. The field detection method of the soil metal substance is characterized by comprising the following steps of S1, collecting a soil sample, measuring the mass fraction of moisture in the soil sample, judging whether the mass fraction of the moisture is more than 1%, if so, entering S2, and if not, entering S3;

s2, drying the soil sample, detecting the mass fraction of the water in the soil sample at intervals of a first time period until the mass fraction of the water in the soil sample is not more than 1%, and entering the step S3;

s3, roasting the soil sample until the quality of the soil sample is constant;

s4, crushing, grinding and filtering the soil sample in the step S3 in a crusher, wherein the diameter of the filtered soil sample is 200-400 meshes, and the soil sample conforms to a cutting and Job sampling formula: q is not less than kd²Wherein d (mm) is the maximum diameter of the soil sample, Q is the reliable quality of the soil sample, k is the reduction coefficient, and the numerical value of k is 0.05-1.0;

s5, compacting the soil sample to prepare a sample tablet, detecting the sample tablet by using an X-ray fluorescence spectrometer, scanning to obtain excited X-rays with different wavelengths, obtaining the types of the metal substances in the soil according to the types of the wavelengths of the X-rays, and obtaining the quantity of the metal substances in the soil according to the intensities of the X-rays with different wavelengths.

2. The method for on-site testing of soil metal substances according to claim 1, wherein in step S1, soil samples are taken from at least 20 different locations simultaneously, the soil samples are divided into at least three parts, one part of each soil sample is taken from each location and mixed, at least three mixed soil samples are obtained, and the moisture content is measured separately.

3. The method for on-site testing of soil metal substances according to claim 2, wherein when soil samples of different locations are taken, the locations of the soil samples are uniformly distributed in the form of a matrix, and the locations of the soil samples are located by using a GPS locating device.

4. The method for in-situ testing of soil metal material as claimed in any one of claims 1-3, wherein in step S2, when drying the soil sample, the soil sample is placed in an electric oven for drying at a temperature of 100 ℃ to 120 ℃.

5. The method for the in-situ measurement of soil metal substances as set forth in claim 4, wherein the first period of time is 20 minutes in step S2.

6. The method for on-site detection of a soil metal material as claimed in any one of claims 1 to 3, wherein the calcination temperature is 1000-1300 ℃, and the calcination time at the calcination temperature is 50-70 minutes.

7. The method for on-site detection of soil metal substances according to claim 6, wherein the temperature is increased to 1200 ℃ by gradient increase during firing, the first gradient is 300 ℃, the firing time is 20 minutes, the second gradient is 700 ℃, the firing time is 20 minutes, the third gradient is 1200 ℃, and the firing time is 60 minutes.

8. The method for on-site testing of soil metal substances as claimed in any one of claims 1 to 3, wherein in step S4, the diameter of the filtered soil sample is 300 mesh.

9. The method for on-site testing of soil metal material according to any one of claims 1 to 3, wherein the step S5 is a step of adding a binder to the soil sample during compaction, wherein the binder is added at a constant temperature, and the temperature is controlled to be 20-25 ℃.

10. The method of claim 9, wherein the binder is selected from the group consisting of microcrystalline cellulose, low pressure polyethylene, paraffin, boric acid, and stearic acid.

Technical Field

The invention relates to the technical field of soil detection, in particular to a field detection method for soil metal substances.

Background

With the continuous development of modern industrial technology and the aggravation of environmental pollution, various soil pollution problems are more and more concerned by people. Particularly, heavy metal element pollution is harmful to human health through food chain accumulation, so that the method for detecting the content of heavy metal in soil in time has important significance for controlling the heavy metal to enter human bodies.

When heavy metal detection is carried out on soil, the detection method mainly comprises an atomic absorption spectrophotometry, an X-ray fluorescence analysis method, an inductive coupling plasma analysis method and the like. The atomic absorption spectrophotometry is mainly used for qualitative and quantitative detection of one element, and various measuring methods are needed for different elements, so that the requirements on operators are high; the inductively coupled plasma analysis method can detect the content of various elements at one time, but the instrument is expensive, has high requirements on environment, and is generally only suitable for laboratory analysis.

The X-ray fluorescence analysis method is a method for performing substance composition analysis and chemical state research by exciting atoms in a substance to be detected by using primary X-ray photons or other microscopic ions to generate fluorescence (secondary X-rays), is sold in mature handheld commodities on the market, can quickly perform multiple element analysis at the same time, and is convenient to use on site. However, due to the limited nature of X-ray, when the soil metal location is detected on site, if the accuracy of laboratory level is to be achieved, the preparation of the sample for on-site detection has certain requirements, including the moisture content and particle size of the sample, which all affect the accuracy of the detection result.

Disclosure of Invention

The purpose of the invention is: a method for on-site detection of a soil metal substance is provided to improve the accuracy of analysis of the soil metal substance using X-ray fluorescence.

In order to achieve the above object, the present invention provides a method for on-site testing of a soil metal substance, comprising the steps of, S1, collecting a soil sample, measuring the mass fraction of moisture in the soil sample, judging whether the mass fraction of moisture is greater than 1%, if so, proceeding to step S2, otherwise, proceeding to step S3;

s2, drying the soil sample, detecting the mass fraction of the water in the soil sample at intervals of a first time period until the mass fraction of the water in the soil sample is not more than 1%, and entering the step S3;

s3, roasting the soil sample until the quality of the soil sample is constant;

s4, crushing, grinding and filtering the soil sample in the step S3 in a crusher, wherein the diameter of the filtered soil sample is 200-400 meshes, and the soil sample conforms to a cutting and Job sampling formula: q is not less than kd²Wherein d (mm) is the maximum diameter of the soil sample, Q is the reliable quality of the soil sample, k is the reduction coefficient, and the numerical value of k is 0.05-1.0;

s5, compacting the soil sample to prepare a sample tablet, detecting the sample tablet by using an X-ray fluorescence spectrometer, scanning to obtain excited X-rays with different wavelengths, obtaining the types of the metal substances in the soil according to the types of the wavelengths of the X-rays, and obtaining the quantity of the metal substances in the soil according to the intensities of the X-rays with different wavelengths.

Preferably, in step S1, soil samples of at least 20 different locations are collected simultaneously, the soil samples of each location are divided into at least three parts, one part of each soil sample is taken out from each location and mixed, at least three parts of the mixed soil samples are obtained, and the mass fractions of the water are respectively detected.

Preferably, when soil samples at different positions are taken, the positions of the soil samples are uniformly distributed in a matrix form, and the positions of the soil samples are positioned by a GPS positioning device.

Preferably, in step S2, when the soil sample is dried, the soil sample is placed in an electric oven for drying, and the drying temperature is 100-120 ℃.

Preferably, in step S2, the first period of time is 20 minutes.

Preferably, the calcination temperature is 1000-1300 ℃, and the calcination time at the calcination temperature is 50-70 minutes.

Preferably, the temperature is increased to 1200 ℃ by adopting a gradient increasing mode during roasting, the first gradient is 300 ℃, the roasting time is 20 minutes, the second gradient is 700 ℃, the roasting time is 20 minutes, the third gradient is 1200 ℃, and the roasting time is 60 minutes.

Preferably, in step S4, the diameter of the filtered soil sample is 300 mesh.

Preferably, in step S5, the soil sample is compacted while adding the binder, and the addition of the binder is performed at a constant temperature, and the temperature is controlled to be 20-25 ℃.

Preferably, the binder is microcrystalline cellulose, low-pressure polyethylene, paraffin, boric acid or stearic acid.

Compared with the prior art, the field detection method for the soil metal substances has the beneficial effects that: detecting the mass fraction of water in the soil sample, classifying the soil samples with different water contents, drying the soil samples when the water content is high, reducing the water content, improving the sample preparation precision, reducing the steps when the water content is low, and improving the detection speed; roasting can change the mineral structure, remove crystal water and carbonate in the mineral, thus overcome the mineral effect; the particle effect is reduced along with the reduction of the granularity of the sample, and the soil sample is crushed and ground to the diameter of 200-400 meshes, so that the nonuniformity of the soil sample and the particle effect of the soil sample can be eliminated; the tabletting can reduce the intensity change of X-rays caused by uneven thickness, eliminate the influences of particle effect, mineral effect, uniformity and the like of the sample in different modes, and improve the manufacturing precision of the soil sample, thereby improving the accuracy of the X-ray fluorescence analysis of the soil metal substances.

Drawings

FIG. 1 is a schematic flow chart of the method for on-site detection of a soil metal substance according to the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

In the preferred embodiment of the method for on-site detection of a soil metal substance according to the present invention, as shown in fig. 1, a portable X-ray fluorescence spectrometer is used for detecting the types and contents of heavy metal substances in soil, the X-ray fluorescence spectrometer is an existing product, and an X-ray spectrum of heavy metals in a soil sample under a preset detection condition is contained in the X-ray fluorescence spectrometer, and an X-ray excited by the soil sample is obtained by scanning and compared with a preset X-ray spectrum, so as to detect the heavy metals in the soil.

The field detection method of the soil metal substance comprises the following steps:

s1 collecting a soil sample, measuring the mass fraction of the water in the soil sample, judging whether the mass fraction of the water is more than 1%, if so, entering the step S2, otherwise, entering the step S3. Whether to carry out drying treatment or not is selected according to the mass fraction of the moisture in the soil sample, and when the mass fraction of the moisture is low, the detection speed can be improved.

Preferably, in step S1, soil samples of at least 20 different locations are collected simultaneously, the soil samples of each location are divided into at least three parts, one part of each soil sample is taken out from each location and mixed, at least three parts of the mixed soil samples are obtained, and the mass fractions of the water are respectively detected.

In this example, 20 soil samples of different positions were collected, the soil samples of each position were divided into four equal parts by weight, one part of each soil sample was taken out from each position and mixed, at least four mixed soil samples were obtained, that is, each mixed soil sample contained 20 soil samples collected from different positions, and then the moisture content of each four soil samples was measured. The soil samples at multiple positions are adopted for uniform mixing, so that the diversity of the samples can be reduced, the specificity of the samples caused by region difference can be reduced, and the accuracy of the detection result can be improved.

Preferably, when soil samples at different positions are taken, the positions of the soil samples are uniformly distributed in a matrix form, and the positions of the soil samples are positioned by a GPS positioning device. The matrix form can evenly adopt the soil sample of different positions, keeps fixed law, and GPS positioner location sampling position simultaneously is convenient for confirm new sampling position when carrying out next soil testing, improves sampling efficiency.

S2, drying the soil sample, detecting the mass fraction of the water in the soil sample at intervals of a first time period until the mass fraction of the water in the soil sample is not more than 1%, and entering the step S3. The drying can reduce the moisture in the soil sample and improve the sample preparation precision.

Preferably, in step S2, when the soil sample is dried, the soil sample is placed in an electric oven for drying, and the drying temperature is 100-120 ℃. In this example, the first period of time was 20 minutes and the temperature of drying was 110 ℃. The drying speed can be accurately obtained by detecting every first time period, and the drying operation can be stopped in time when the weight fraction of the moisture is less than 1%, so that the time waste is avoided.

In other embodiments, the first time period for moisture detection during drying is 30 minutes, 25 minutes. The drying temperature may be 100 ℃ or 120 ℃.

And S3, roasting the soil sample until the quality of the soil sample is constant. The roasting can change the mineral structure, remove the crystal water and carbonate in the mineral, thereby overcoming the mineral effect, and when the quality of the soil sample is constant, the crystal water and carbonate in the mineral can be ensured to be completely removed, the influence of the mineral effect is reduced, and the accuracy of the detection result is improved.

Preferably, the roasting temperature is 1000-1300 ℃ and the roasting time at the roasting temperature is 50-70 minutes when the soil sample is roasted.

In this example, the temperature was increased to 1200 ℃ by gradient increase during firing, the first gradient was 300 ℃, the firing time was 20 minutes, the second gradient was 700 ℃, the firing time was 20 minutes, the third gradient was 1200 ℃, and the firing time was 60 minutes. By adopting a gradient roasting mode, different impurities in the soil sample can be eliminated in a gradient manner, and the roasting energy consumption is reduced.

S4, crushing, grinding and filtering the soil sample in the step S3 in a crusher, wherein the diameter of the filtered soil sample is 200-400 meshes, and the soil sample conforms to a cutting and Job sampling formula: q is not less than kd²Wherein d (mm) is the maximum diameter of the soil sample, Q is the reliable quality of the soil sample, k is the coefficient of reduction, and the value of k is 0.05-1.0. The particle effect is reduced along with the reduction of the granularity of the sample, and after the sample is crushed and ground suddenly, the nonuniformity of the soil sample can be eliminated, and the particle effect of the soil sample can be eliminated.

Preferably, the diameter of the soil sample after filtration is 300 mesh. When the soil sample is filtered, a plurality of filter sieves are adopted for filtration in a gradient way, and the number of the holes of the filter sieves is gradually increased until the number reaches 300 meshes. The filtration can improve filterable efficiency in the echelon, avoids large-size magazine to block up the filtration pore and influence the filter effect.

The method comprises the steps of cleaning a crushing container before crushing a soil sample, cleaning the soil sample once, and then performing formal crushing to reduce pollution caused by residual samples after the previous crushing.

S5, compacting the soil sample to prepare a sample tablet, detecting the sample tablet by using an X-ray fluorescence spectrometer, scanning to obtain excited X-rays with different wavelengths, obtaining the types of the metal substances in the soil according to the types of the wavelengths of the X-rays, and obtaining the quantity of the metal substances in the soil according to the intensities of the X-rays with different wavelengths.

Preferably, the thickness of the resulting sample preform during the compaction process is more than twice the thickness of the semi-attenuating layer, which is the thickness of the absorbing material required to attenuate the transmitted X-ray intensity by half. In this example, the thickness of the formed test piece was greater than 2cm, and the surface flatness of the test piece was ensured during the compaction.

Preferably, the soil sample is compacted by adding the adhesive, and the adding of the adhesive is carried out at a constant temperature, and the temperature is controlled to be 20-25 ℃. The adhesive has good and stable cohesiveness and low impurity content, and can ensure that a soil sample is cohered into a sheet.

Preferably, the binder is microcrystalline cellulose, low-pressure polyethylene, paraffin, boric acid or stearic acid. When microcrystalline cellulose is selected as the adhesive, the proportion of the soil sample to the microcrystalline cellulose is 5g of sample and 2g of the adhesive; when low-pressure polyethylene, low-pressure polyethylene and boric acid are selected as the adhesive, the proportion of the soil sample to the adhesive is 5g and 2g of the adhesive is matched; when paraffin is selected as the adhesive, the proportion of the soil sample to the paraffin is 10g and 1g of the adhesive is added; when stearic acid is selected as the adhesive, the proportion of the soil sample to the stearic acid is 10g of sample and 0.5g of the adhesive.

To sum up, the embodiment of the invention provides a field detection method for soil metal substances, which detects the mass fraction of moisture in soil samples, classifies the soil samples with different moisture contents, performs drying treatment firstly when the moisture content is high, reduces the moisture content, can improve the sample preparation precision, and can reduce steps and improve the detection speed when the moisture content is low; roasting can change the mineral structure, remove crystal water and carbonate in the mineral, thus overcome the mineral effect; the particle effect is reduced along with the reduction of the granularity of the sample, and the soil sample is crushed and ground to the diameter of 200-400 meshes, so that the nonuniformity of the soil sample and the particle effect of the soil sample can be eliminated; the tabletting can reduce the intensity change of X-rays caused by uneven thickness, eliminate the influences of particle effect, mineral effect, uniformity and the like of the sample in different modes, and improve the manufacturing precision of the soil sample, thereby improving the accuracy of the X-ray fluorescence analysis of the soil metal substances.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.