CN113720844A - Quantitative analysis method for soil micro-plastics in biological soil crust layer - Google Patents
Quantitative analysis method for soil micro-plastics in biological soil crust layer Download PDFInfo
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- CN113720844A CN113720844A CN202111180528.8A CN202111180528A CN113720844A CN 113720844 A CN113720844 A CN 113720844A CN 202111180528 A CN202111180528 A CN 202111180528A CN 113720844 A CN113720844 A CN 113720844A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
- G01N1/08—Devices for withdrawing samples in the solid state, e.g. by cutting involving an extracting tool, e.g. core bit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/38—Diluting, dispersing or mixing samples
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- G—PHYSICS
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- G01N25/00—Investigating or analyzing materials by the use of thermal means
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Abstract
Biological soil crust is a complex formed by bonding micro organisms and soil particles on the surface of an arid and semiarid region, and organic substances and micro plastics are easily adsorbed by the complex due to the special physical structure and chemical composition of the complex. Because organic matters and the micro-plastics have similar properties and structures, the micro-plastics are not easy to separate from a biological soil crust layer with concentrated organic matter content and carry out quantitative analysis during detection. The invention relates to a step-by-step dilution method for extracting soil micro-plastics in a biological soil crust layer according to the proportion of 2ml of maize germ oil/g of biological soil crust, wherein the extraction solution is diluted by 2 times per step and is 3 steps in total, and a high-temperature probe is used for heating to promote the structure and the form of the micro-plastics to be changed, so that the problem that the quantitative analysis of the micro-plastics is interfered by organic matters in the crust layer is effectively solved, and the quantitative analysis precision and the efficiency of the soil micro-plastics in the biological soil crust layer are improved. The method is simple to operate, low in cost and high in accuracy.
Description
Technical Field
The invention belongs to the technical field of environmental engineering, and particularly relates to a quantitative analysis method for soil micro-plastics in a biological soil crust layer.
Background
With the rapid development of the plastic industry, plastic products have become an indispensable class of products in daily life. The plastic product can exist in the environment for a long time, and is easily decomposed into small blocks with the grain diameter smaller than 5mm under the action of external force in the environment. The micro plastic has the characteristics of large specific surface area, difficult degradation and the like, can adsorb a plurality of pollutants to become a main pollution carrier, and some impurities enter soil to become novel pollutants, so that the soil structure is changed, the biological development of the soil is influenced, and the stability of the structure and the function of an ecological system is directly and indirectly threatened.
Biological soil crust is a main covering of the earth surface in arid and semi-arid regions and is one of main markers of earth surface stability and health. Biological soil crust can obviously affect a plurality of links of energy flow, logistics and different ecological processes of an ecological system, is a main contributor to surface soil stabilization, water retention and fertility improvement of natural vegetation and artificial vegetation areas in arid and semi-arid regions, and has irreplaceable effect on the whole structure and function maintenance of the ecological system. However, due to the special physical structure and chemical composition of the biological soil cortex, the biological soil cortex has great potential of absorbing and enriching the micro-plastics in the soil, and becomes a main path, carrier and action object of the micro-plastics in surface aggregation, migration and the like of arid and semi-arid regions. Therefore, the separation and quantitative analysis of the micro-plastics in the biological soil crust layer are important prerequisites for evaluating the micro-plastic pollution condition in the soil environment of arid and semi-arid regions. However, there is no quantitative analysis method for the micro-plastics in the biological soil cortex at present. Particularly, under the condition that soil micro-plastics and organic matters coexist in the biological soil crust layer and are gathered in a large amount, the properties of the organic matters and the micro-plastics are similar, and the difficulty of separating and quantitatively analyzing the micro-plastics in the biological soil crust layer from the organic matters is greatly increased.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for quantitatively analyzing soil microplastics in a biological soil cortex layer. The method is simple to operate, low in cost and high in accuracy, and provides technical support for ecological effect evaluation and restoration of soil micro-plastics in the biological soil crust layer.
The purpose of the invention is realized by the following technical scheme:
a quantitative analysis method for soil micro-plastics in a biological soil crust layer comprises the following steps:
a. sample collection and processing
Collecting the biological soil crust layer by adopting a cutting ring made of aluminum or glass after raining or on the wet biological soil crust layer, drying the collected soil sample in a shady and cool place in the dark, and storing the dried soil sample in a 4 ℃ dark place at constant temperature for later use;
b. stepwise dilution
After the wet biological soil crust layer is dried in the air, 2.5g of a biological soil crust layer sample is weighed and added into a 250ml conical flask, 100ml of deionized water and 5ml of vegetable oil (corn germ oil) are added, and the mixture is manually shaken for 1min and then kept stand for 30min;
when the sediment is completely precipitated at the bottom of the flask, taking supernatant of an oil layer and a water layer in the conical flask, pouring the supernatant into a suction filtration funnel with a microporous filter membrane for suction filtration, washing the suction filtration funnel, the microporous filter membrane and a glass rod by using 2-3ml of absolute ethyl alcohol in the suction filtration process, and pouring washing liquid into the conical flask; taking 2-3ml of absolute ethyl alcohol again, washing again until no oily liquid drops exist on the suction filter funnel and the glass rod, and standing the filtrate in the conical flask again and layering;
and adding the obtained oil layer solution into corn germ oil for dilution, and fixing the volume to 25 ml. 12.5ml of the solution after the volume fixing is taken out and added into a 25ml volumetric flask, and the volume is fixed to 25 ml. Repeating the step for 3 times, diluting for 3 times to form 3 dilution grades with the concentration of 1 grade, 2 grade and 3 grade, wherein the concentration of each grade is one half of the concentration of the previous grade, and finally obtaining a sample with the concentration of 3 grade;
c. heating probe
Quantitatively measuring the extracted liquid drops of the 3 rd-level dilution grade on a glass slide, observing under a microscope, heating by using a high-temperature probe at 140 ℃, recording the number of objects with changed morphological structures, and quantitatively measuring the volume of 25 ml/glass slide liquid drops and 8/2.5 g of the volume of the objects with changed morphological structures, wherein the volume of the objects is the content of the micro-plastics in the biological soil cortex.
The advantages and the beneficial effects of the invention are as follows:
diluting the obtained extractive solution at 2 times of dilution ratio for each stage for 3 times; then, heating the diluted extracting solution of the last stage by a high-temperature probe to change the structure of the micro plastic, and screening and counting by a microscope; and finally, the content of the micro-plastic in the soil can be obtained through conversion. The method is simple and rapid to operate, low in cost and high in accuracy, and can be used for carrying out quantitative analysis on the micro-plastics in the complex biological soil crust layer, so that the interference of organic matters, indissolvable compounds and the like in the soil on the identification of the micro-plastics is avoided.
Drawings
FIG. 1 is a graph comparing the change in area of the microplastic and the amount of unknown increase in carbon black under different heating temperature conditions.
FIG. 2 is a graph showing the change in area of the micro-plastic under different heating temperature conditions.
FIG. 3 is a comparison graph of the content of the micro-plastics in the 50 mul determination liquid under different dilution levels and the content of the soil micro-plastics obtained through calculation.
Detailed Description
A quantitative analysis method for micro-plastics in a biological soil crust layer comprises the following steps:
a. sample collection and processing
After raining or wetting the biological soil crust layer by using ultra-pure water contained in a glass ware, collecting the biological soil crust layer by using an aluminum or glass ring cutter, and putting on cotton clothes instead of chemical fiber clothes by an operator;
and (3) collecting a soil sample, drying the soil sample in a shade and light-proof place, and placing the dried soil sample in a 4 ℃ light-proof place for constant-temperature storage for later use.
Weighing 2.5g of a sample of the biological soil cortex, adding the sample into a 250ml conical flask, adding 100ml of deionized water and 5ml of corn germ oil, manually oscillating for 1min, and standing for 30 min. After standing, the soil has large particle aggregates or clods, and the soil can be stirred again for 2-3min by a magnetic stirrer until the large particle aggregates or clods are completely dispersed, and then the soil is stood again for 30min to precipitate the bottom of the conical flask;
b. stepwise dilution
Taking supernatant of the oil layer and the water layer in the conical flask, pouring the supernatant into a suction filtration funnel with a microporous filter membrane for suction filtration, washing the suction filtration funnel, the microporous filter membrane and a glass rod by using 2-3ml of absolute ethyl alcohol in the suction filtration process, and pouring washing liquid into the conical flask. Taking 2-3ml of absolute ethyl alcohol again, washing again until no oily liquid drops exist on the suction filter funnel and the glass rod, and standing the obtained filtrate in the conical flask again and layering;
and adding the obtained oil layer solution into corn germ oil for dilution, and fixing the volume to 25 ml. 12.5ml of the solution after the volume fixing is taken out and added into a 25ml volumetric flask, and the volume is fixed to 25 ml. Repeating the step for 3 times, setting the concentration of 3 grades to be 1, 2 and 3 grades, wherein the concentration of each grade is one half of the concentration of the previous grade, and finally obtaining the sample with the concentration of 3 grades.
Heating probe
Dropping 50 mu l (0.05ml) drops of liquid for extraction at different dilution levels on a glass slide, observing under a microscope, and firstly observing by adopting a 10-time ocular lens and a 4-time objective lens, wherein in figure 3, a comparison graph of the content of micro-plastics in 50 mu l determination liquid and the content of micro-plastics in soil at different dilution levels is shown in the graph: the content of soil micro-plastics in the tertiary biological soil crust layer is 2035.2/g, and the quantity of the micro-plastics in the 50 mul measuring solution is 1.27.
Selecting four top points of two diagonal lines of the oil drop and five areas of the intersection point for observation, and respectively recording the quantity of the micro-plastics; and switching the objective lens to a 40-time oil lens, subdividing each observation area into five sub-areas according to the dividing method, observing and respectively recording the quantity and the area of the micro-plastics, heating by using a high-temperature probe at 140 ℃ after recording, observing and recording the quantity of the objects with changed morphological structures by using a microscope, recording the quantity of the micro-plastics, and completing quantitative analysis of the soil micro-plastics in the biological soil cortex through conversion.
In the heating process of the high-temperature probe, setting an experiment group every 20 ℃ from 100 ℃, recording the deformation quantity of the micro-plastic, analyzing and comparing the obtained individual size and quantity of the micro-plastic at different temperatures, establishing the quantity relation between the temperature and the extraction rate of the micro-plastic, and obtaining the optimum temperature for observing the morphological change of the micro-plastic.
Fig. 1 shows that during the temperature rise, the area of the micro-plastic gradually decreases and gradually stabilizes around 140 ℃, and the amount of unidentified carbon black under a microscope gradually increases with the temperature rise and exceeds the counting range at 180 ℃. Therefore 140 degrees celsius was chosen as the optimum heating temperature for the micro-plastic.
FIG. 2 is a graph showing the change of the area of the micro-plastic under different heating temperature conditions. As can be seen from fig. 2: as the heating temperature increases, the micro plastic area gradually decreases.
Computing
The formula of the concentration of each stage is as follows:
wherein c is0The volume is 1 grade to 25ml of initial concentration.
The calculation formula of the original solution concentration c is as follows:
wherein m is the total number of the micro-plastics obtained by observation, and a is the sampling observation frequency of each stage of sample. n is the dilution rating. The unit of c is one/ml.
The calculation formula of the content C of the micro-plastics in the soil is as follows:
wherein C is the concentration of the original solution, and the unit of C is unit/g.
In the process of stepwise dilution, small black particles appear in observation of each stage of dilution, and the frequency is fixed in the observation process of each stage of dilution, so that the frequency-fixed small particles are used as organic matters, and the interference of substances except micro-plastics on the measurement method is reduced through the stepwise dilution process.
The invention increases the detection precision of the micro plastic through the processes of high-temperature heating and gradual dilution, and has simple operation, high efficiency and easy implementation. The micro plastic is deformed in the high-temperature heating process, so that the counting can be more intuitively carried out in the observation; in addition, in the process of gradual dilution, organic matter particles can be easily observed, the organic matter particles are prevented from being used as micro-plastics for counting, and the interference of other substances except the micro-plastics on the measurement method is reduced.
Claims (1)
1. A quantitative analysis method for soil micro-plastics in a biological soil crust layer comprises the following steps:
a. sample collection and processing
Wetting the biological soil crust layer with ultrapure water after rain, collecting the biological soil crust layer by adopting an aluminum or glass cutting ring, drying the collected soil sample in a shady and cool place in the dark, and storing the dried soil sample in a 4 ℃ dark place at constant temperature for later use;
b. stepwise dilution
After the moist biological soil crust layer is air-dried, weighing 2.5g of a biological soil crust layer sample, adding the biological soil crust layer sample into a 250ml conical flask, adding 100ml of deionized water and 5ml of vegetable oil (corn germ oil), manually oscillating for 1min, and standing for 30min;
when the sediment is completely precipitated at the bottom of the flask, taking supernatant of an oil layer and a water layer in the conical flask, pouring the supernatant into a suction filtration funnel with a microporous filter membrane for suction filtration, washing the suction filtration funnel, the microporous filter membrane and a glass rod by using 2-3ml of absolute ethyl alcohol in the suction filtration process, and pouring washing liquid into the conical flask; taking 2-3ml of absolute ethyl alcohol again, washing again until no oily liquid drops exist on the suction filter funnel and the glass rod, and standing the filtrate in the conical flask again and layering;
diluting the obtained oil layer solution with corn germ oil to a constant volume of 25 ml; taking 12.5ml out of the solution with constant volume, adding the solution into a 25ml volumetric flask, keeping the constant volume to 25ml, repeating the step for 3 times to form 3 dilution grades, wherein the concentration of each grade is 1, 2 and 3 grades, and the concentration of each grade is one half of the concentration of the previous grade, and finally obtaining a sample with 3 grades of concentration;
c. heating probe
Quantitatively measuring the extracted liquid drops of the 3 rd-level dilution grade on a glass slide, observing under a microscope, heating by using a high-temperature probe at 140 ℃, recording the number of objects with changed morphological structures, and quantitatively measuring the volume of 25 ml/glass slide liquid drops and 8/2.5 g of the volume of the objects with changed morphological structures, wherein the volume of the objects is the content of the micro-plastics in the biological soil cortex.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110987578A (en) * | 2019-10-28 | 2020-04-10 | 天津理工大学 | Screening and extracting method for micro-plastics in vegetation cover soil |
| CN111426545A (en) * | 2020-03-25 | 2020-07-17 | 中国环境科学研究院 | Method for quickly separating micro-plastic in soil |
| CN113155558A (en) * | 2021-02-05 | 2021-07-23 | 北京市理化分析测试中心 | Method for extracting, separating and purifying micro-plastic in soil |
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- 2021-10-11 CN CN202111180528.8A patent/CN113720844A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110987578A (en) * | 2019-10-28 | 2020-04-10 | 天津理工大学 | Screening and extracting method for micro-plastics in vegetation cover soil |
| CN111426545A (en) * | 2020-03-25 | 2020-07-17 | 中国环境科学研究院 | Method for quickly separating micro-plastic in soil |
| CN113155558A (en) * | 2021-02-05 | 2021-07-23 | 北京市理化分析测试中心 | Method for extracting, separating and purifying micro-plastic in soil |
Non-Patent Citations (3)
| Title |
|---|
| 张宇恺: "土壤微塑料污染及其分析方法", 《四川环境》 * |
| 程万莉: "我国西北覆膜农田土壤微塑料数量及分布特征", 《农业环境科学学报》 * |
| 董明潭: "基于油提取的土壤与沉积物中微塑料的分离方法", 《环境科学研究》 * |
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