Soil iron isotope determination sample sampling method and iron isotope composition determination method

Abstract

The invention provides a soil iron isotope determination sample sampling method and an iron isotope composition determination method.The sampling method comprises the steps that stratum scale samples are collected, and samples which are high or low in iron content and can represent the overall characteristics of stratums are selected from different stratums from top to bottom according to the total iron content; collecting a generation layer scale sample; micro-domain scale samples are collected, and iron isotope determination samples in a micro-domain high iron leaching zone, a micro-domain low iron leaching zone, a micro-domain high iron enrichment zone and a micro-domain low iron enrichment zone in pairs are collected according to different iron leaching and enrichment degrees; collecting a new body scale sample, collecting iron-manganese nodules in an area in which rich iron-manganese nodules are distributed, synchronously collecting matrix soil around the iron-manganese nodules, and determining iron isotope composition of the iron-manganese nodules and the matrix around the iron-manganese nodules; transporting the collected samples into a room, and air-drying the samples in a shady and dry place. The device has the technical effects that the design is reasonable, and the accurate determination of the iron isotope in the soil is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of iron isotope determination, and particularly relates to a soil iron isotope determination sample sampling method and an iron isotope composition determination method. Background Art

[0002] According to the research scale or research object of predecessors, the research on soil iron isotopes can be summarized into two aspects: on the one hand, it is a larger scale, taking strata or profiles of different geological ages as the research objects, measuring and analyzing the distribution and fractionation characteristics of iron isotopes in the entire profile, revealing the fractionation mechanism of iron isotopes, and exploring paleoclimate and environmental changes; on the other hand, it is a smaller scale, taking a certain soil layer or local soil material enrichment or leaching micro-domain in the profile as the research object, measuring and analyzing the fractionation characteristics of iron isotopes in the soil from a soil science perspective, revealing the fractionation mechanism of iron isotopes, and exploring paleoclimate and environmental evolution.

[0003] At present, existing studies have mainly focused on the first aspect, the distribution and fractionation characteristics of iron isotopes in geological strata or sections as a whole, and there is a lack of discussion on the principle of soil micro-domain iron isotope fractionation. Studies have reported that the iron isotope composition of different layers between large-scale strata or sections as a whole is not very different, and there is basically no or very little iron isotope fractionation. From the point of view of no or very little iron isotope fractionation, it is not that there is no iron isotope fractionation, but that there is iron isotope fractionation, but the degree of fractionation is small, and short-distance migration at the millimeter or centimeter level has not yet occurred. In addition, the sampling method of stratum or occurrence layer sampling, which collects a certain area of ​​samples on the layer surface and mixes them evenly as representative samples of the layer for the determination and analysis of iron isotopes, conceals the micro-domain migration characteristics of iron enrichment (concentration) and depletion (depletion) formed by alternating redox in the soil, and conceals the short-distance fractionation signal of iron isotopes, resulting in the illusion that there is no iron isotope fractionation in the geological section.

[0004] To this end, we hypothesize that during the formation of the loess-paleosol sequence profile, alternating redox cycles caused iron migration and transformation, resulting in micro-domain enrichment and leaching characteristics, which resulted in differences in iron concentration within soil micro-domains, accompanied by micro-domain fractionation of iron isotopes, but had not yet reached obvious migration. The stronger the degree of soil weathering development, the greater the enrichment / leaching iron isotope fractionation. The degree of fractionation may become a potential indicator of soil weathering development intensity.

[0005] Therefore, it is urgent to innovate the soil iron isotope sample collection method and develop a soil iron isotope sample sampling method and an iron isotope composition determination method. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art and provide a new technical solution for a soil iron isotope determination sample sampling method and a method for determining the iron isotope composition.

[0007] According to a first aspect of the present invention, a soil iron isotope determination sample sampling method is provided, comprising the following steps:

[0008] Collect stratigraphic scale samples to select samples with higher or lower iron content from top to bottom in different strata based on the total iron content, which can represent the overall characteristics of the strata, and use them to determine the iron isotope composition of the stratigraphic scale samples;

[0009] Collect samples at the level of the soil layer to divide the soil genetic layers in each layer according to soil characteristics, and collect soil genetic layer samples from bottom to top;

[0010] Collect micro-scale samples to collect paired iron isotope determination samples from micro-domain high iron leaching area, low iron leaching area, high iron enrichment area and low iron enrichment area according to the different degrees of iron leaching and enrichment;

[0011] Collect new body-scale samples to collect ferromanganese nodules in areas with abundant ferromanganese nodules, and simultaneously collect matrix soil around the ferromanganese nodules to determine the iron isotope composition of the ferromanganese nodules and their surrounding matrix;

[0012] After transporting the collected samples indoors, place them in a cool and dry place to air-dry, pass them through a 100-mesh nylon sieve, and set aside.

[0013] Optionally, stratigraphic scale samples are collected, including: first, determining stratigraphic boundaries with time control significance based on soil color, texture, structure, and profile morphological characteristics of new bodies, and collecting dating samples at the stratigraphic boundaries, and using luminescence dating to determine the formation age of the soil to obtain soil age boundaries; second, based on the differences between the profile morphological characteristics of the soil and the age boundaries, different strata are divided according to stratigraphic division standards to construct a sequence.

[0014] Optionally, collecting stratigraphic scale samples also includes:

[0015] Use a hard plastic shovel to remove about 5 cm thick topsoil from top to bottom, remove the loose soil, and collect samples at equal intervals of 20 cm from top to bottom to determine the content of iron in different forms.

[0016] Optionally, collecting micro-scale samples includes:

[0017] Based on the color, texture, structure, and morphological characteristics of the new bodies in the soil profile, the characteristic layers of the iron-rich leaching area and the iron-enriched area below are determined.

[0018] Optionally, the color of the iron-leaching area is mainly light yellow or white, and the lighter the color, the higher the degree of leaching; the color of the iron-enriched area is mainly rust or red, and the redder the color, the higher the degree of iron enrichment.

[0019] Optionally, collect neonate-scale samples, including:

[0020] Large original soil samples enriched with iron-manganese film were collected, and the film on the surface of the soil block was scraped off with a rustless steel blade indoors to collect the film samples. At the same time, soil matrix samples with the film scraped off were collected to determine the iron isotope composition of the iron-manganese film and its soil matrix.

[0021] Optionally, when scraping the rubber film on the surface of the soil block, the scraped thickness does not exceed 1 mm.

[0022] Optionally, the ferromanganese nodules include 0.5-1 mm ferromanganese nodules and 1-2 mm ferromanganese nodules.

[0023] According to a second aspect of the present invention, there is provided a method for determining iron isotope composition, which is used to determine the iron isotope composition of a soil sample collected by the soil iron isotope determination sample sampling method as described in the first aspect, comprising:

[0024] First, each soil sample was weighed and HNO 3 -HCl-HClO 4 Digest with mixed acid, evaporate the digestion solution to dryness and dissolve with 6N HCl;

[0025] Secondly, cation exchange resin is used to purify the iron to a recovery rate of 99.5%;

[0026] Finally, 2% HNO 3 The purified iron solution was diluted to prepare the test solution, and the iron isotope composition was determined by multi-acceptor inductively coupled plasma mass spectrometry; the DCB method was used to extract the iron isotopes of free iron and silicate-bound iron, and the iron isotope composition was calculated by the ratio of the measured value to the standard value of the international standard material IRMM-014.

[0027] Alternatively, the iron isotope composition is calculated using the following formula:

[0028]

[0029] In the above formula, ( 56 Fe / 54 Fe) Sample is the measured value; ( 56 Fe / 54 Fe) IRMM-014 It is the standard value of the international standard material IRMM-014.

[0030] A technical effect of the present invention is:

[0031] In the examples of the present application, soil samples collected by the soil iron isotope determination sampling method and the iron isotope composition determination method were used to determine the iron isotope composition of the soil samples, and the determination results were relatively accurate. Moreover, through analysis, it was found that the iron isotope composition of the iron-enriched area and the leaching area and the iron-manganese neoformation at the micro-scale varied greatly, especially the δ 56 Fe changes greatly. The iron isotope fractionation mechanism well traces the short-distance migration of iron during the formation of the loess-paleosol sequence profile, as well as the migration path of light iron isotopes from the matrix to the iron-manganese nodules. The migration and transformation of iron mainly occur in microdomains, while iron isotope fractionation mainly occurs in microdomains within the well-developed soil layer, which helps to explore the mechanism of soil microdomain iron isotope fractionation, thereby helping to obtain the microdomain migration characteristics of iron enrichment and leaching formed by alternating redox in the soil, and then obtain the short-distance fractionation signal of iron isotopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic flow chart of a soil iron isotope determination sampling method according to another embodiment of the present invention;

[0033] Figure 2 Schematic diagram of a soil iron isotope measurement sample according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0035] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0036] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0037] According to a first aspect of the present invention, see Figure 1and Figure 2 , provides a soil iron isotope determination sample sampling method, comprising the following steps:

[0038] Step S100, collecting stratigraphic scale samples, and selecting samples with higher or lower iron content that can represent the overall characteristics of the strata from top to bottom in different strata according to the total iron content, for determining the iron isotope composition of the stratigraphic scale samples;

[0039] Step S200, collecting soil genetic layer scale samples, dividing soil genetic layers in each layer according to soil characteristics, and collecting soil genetic layer samples from bottom to top;

[0040] Step S300, collecting micro-scale samples, and collecting iron isotope determination samples in pairs of micro-domain high iron leaching area, low iron leaching area, high iron enrichment area and low iron enrichment area according to the different degrees of iron leaching and enrichment, see Figure 2 ;

[0041] Step S400, collecting new body-scale samples, collecting iron-manganese nodules in areas where there are abundant iron-manganese nodules, and simultaneously collecting matrix soil around the iron-manganese nodules, and determining the iron isotope composition of the iron-manganese nodules and the matrix around them;

[0042] Step S500, after transporting the collected samples indoors, place them in a cool and dry place for air drying, and pass them through a 100-mesh nylon sieve for later use.

[0043] In the examples of the present application, soil samples collected by the soil iron isotope determination sampling method and the iron isotope composition determination method were used to determine the iron isotope composition of the soil samples, and the determination results were relatively accurate. Moreover, through analysis, it was found that the iron isotope composition of the iron-enriched area and the leaching area and the iron-manganese neoformation at the micro-scale varied greatly, especially the δ 56 Fe changes greatly. The iron isotope fractionation mechanism well traces the short-distance migration of iron during the formation of the loess-paleosol sequence profile, as well as the migration path of light iron isotopes from the matrix to the iron-manganese nodules. The migration and transformation of iron mainly occur in microdomains, while iron isotope fractionation mainly occurs in microdomains within the well-developed soil layer, which helps to explore the mechanism of soil microdomain iron isotope fractionation, thereby helping to obtain the microdomain migration characteristics of iron enrichment and leaching formed by alternating redox in the soil, and then obtain the short-distance fractionation signal of iron isotopes.

[0044] Optionally, stratigraphic scale samples are collected, including: first, determining stratigraphic boundaries with time control significance based on soil color, texture, structure, and profile morphological characteristics of new bodies, and collecting dating samples at the stratigraphic boundaries, and using luminescence dating to determine the formation age of the soil to obtain soil age boundaries; second, based on the differences between the profile morphological characteristics of the soil and the age boundaries, different strata are divided according to stratigraphic division standards to construct a sequence.

[0045] In the above implementation, it is helpful to quickly obtain stratigraphic scale samples and can divide different strata according to stratigraphic division standards.

[0046] Optionally, collecting stratigraphic scale samples also includes:

[0047] Use a hard plastic shovel to remove about 5 cm thick topsoil from top to bottom, remove the loose soil, and collect samples at equal intervals of 20 cm from top to bottom to determine the content of iron in different forms.

[0048] In the above implementation, it helps to ensure that the content of different forms of iron in the collected formation-scale samples can be accurately determined.

[0049] Optionally, collecting micro-scale samples includes:

[0050] Based on the color, texture, structure, and morphological characteristics of the new bodies in the soil profile, the characteristic layers of the iron-rich leaching area and the iron-enriched area below are determined. This helps to accurately and quickly collect micro-scale samples and helps to determine the characteristic layers of the iron-rich leaching area and the iron-enriched area below.

[0051] Optionally, the color of the iron-leaching area is mainly light yellow or white, and the lighter the color, the higher the degree of leaching; the color of the iron-enriched area is mainly rust or red, and the redder the color, the higher the degree of iron enrichment.

[0052] In the above embodiment, the colors of the iron-leaching region and the iron-enriching region can be accurately distinguished based on the color of the iron-leaching region and the color of the iron-enriching region.

[0053] Optionally, collect neonate-scale samples, including:

[0054] Large original soil samples enriched with iron-manganese film were collected, and the film on the surface of the soil block was scraped off with a rustless steel blade indoors to collect the film samples. At the same time, soil matrix samples with the film scraped off were collected to determine the iron isotope composition of the iron-manganese film and its soil matrix.

[0055] In the above embodiment, it is helpful to quickly collect the film sample and the soil matrix sample, thereby facilitating the accurate determination of the iron isotope composition of the iron-manganese film and its soil matrix.

[0056] Optionally, when scraping the film on the surface of the soil block, the scraped thickness does not exceed 1 mm, which helps to ensure the accuracy of the collected film sample.

[0057] Optionally, the ferromanganese nodules include 0.5-1 mm ferromanganese nodules and 1-2 mm ferromanganese nodules, which is helpful to accurately determine the iron isotope composition of the ferromanganese nodules and the matrix surrounding them.

[0058] According to a second aspect of the present invention, there is provided a method for determining iron isotope composition, which is used to determine the iron isotope composition of a soil sample collected by the soil iron isotope determination sample sampling method as described in the first aspect, comprising:

[0059] First, each soil sample was weighed and digested with HNO3-HCl-HClO4 mixed acid. The digestion solution was evaporated and dissolved with 6N HCl. Among them, the soil sample was <0.149mm (100 mesh) and contained about 50μg of total iron.

[0060] Secondly, the iron is purified using a cation exchange resin to a recovery rate of 99.5%.

[0061] Finally, the purified iron solution was diluted with 2% HNO3 to prepare the test solution, and the iron isotope composition was determined by the ThermoFisher multi-acceptor inductively coupled plasma mass spectrometer MC-ICP-MS (Neptune Plus, 2017, USA). The DCB method was used to extract the iron isotopes of free iron and silicate-bound iron, and the iron isotope composition (δ 56 Fe, ‰), and the final results were expressed as mean ± 2 sd.

[0062] In the above-mentioned embodiment, the method for determining the iron isotope composition is relatively simple, which helps to accurately determine the iron isotope composition in the soil sample, thereby helping to obtain the micro-domain migration characteristics of iron enrichment and leaching caused by alternating redox in the soil, and then obtain the short-distance fractionation signal of iron isotopes.

[0063] Alternatively, the iron isotope composition is calculated using the following formula:

[0064]

[0065] In the above formula, ( 56 Fe / 54 Fe) Sample is the measured value; ( 56 Fe / 54 Fe) IRMM-014 It is the standard value of the international standard material IRMM-014.

[0066] In the above embodiment, international standard materials andesite AGV-2 (Guano Valley, Oregon, USA) and basalt BCR-2 (Columbia River, Oregon, USA) were inserted to monitor the measurement quality. 56 The Fe determination result was 0.085±0.036‰ (n=3), which was comparable to the laboratory standard determination value of 0.061±0.060‰ (n=3) and within the recommended value of 0.105±0.011‰ (n=7) (Craddock and Dauphas, 2010). 56 The Fe determination result was 0.083±0.047‰ (n=3), which was comparable to the laboratory standard determination value of 0.085±0.019‰ (n=3) and within the recommended value of 0.091±0.011‰ (n=8) (Craddock and Dauphas, 2010). 56 The Fe determination accuracy is within the range of ±0.05‰ (2sd). Therefore, the calculation method of iron isotopes is relatively simple, which helps to accurately obtain the calculation results of iron isotopes.

[0067] In the present application example, after analyzing the measurement results, it can be seen that the soil profile δ 56 Fe (0.097‰~0.167‰, average value 0.133‰) is systematically heavy, and shows an obvious fluctuation trend of increasing first and then decreasing with depth, and the coefficient of variation with profile depth is 15.66%. 56 Fe ranged from 0.048±0.01‰ to 0.168±0.03‰, with an average value of 0.102±0.03‰ and a range of 0.12‰.

[0068] Furthermore, the iron isotope composition of the microdomain in the test layer varies greatly, with a coefficient of variation of 34.2%, which is significantly larger than the iron isotope variation at the stratigraphic scale. 56 Fe ranged from 0.119±0.04‰ to 0.168±0.03‰, with an average of 0.143±0.04‰, while the enriched microdomain δ 56 Fe ranges from 0.048±0.01‰ to 0.096±0.04‰, with an average of 0.079±0.03‰. This indicates that during the formation of the leaching zone, light iron migrates preferentially while heavy iron is relatively enriched, and light iron is deposited in the enriched area. 56 Fe is between 0.119±0.04‰ and 0.128±0.03‰, which is less than that in the high leaching zone (HD) between 0.145±0.03‰ and 0.168±0.03‰, indicating that the latter is enriched in heavy iron isotopes. 56Fe ranges from 0.083±0.03‰ to 0.096±0.04‰, greater than that in the high enrichment area (HC) δ 56 Fe ranges from 0.048±0.01‰ to 0.074±0.07‰, indicating that the latter isotope is lighter. The iron isotope composition in the enrichment area is lighter than that in the leaching area, showing the rule of HD>LD>LC>HC. Contrary to the iron isotope fractionation rule, δ 26 Mg is light in the leaching area, and the magnesium isotope composition in the enrichment area is heavy, showing the rule of HD<LD<LC<HC.

[0069] In addition, the iron isotope composition of the iron-manganese neoformed body was further determined and analyzed, and it was found that δ 56 Fe in the soil matrix ranges from 0.145±0.03‰ to 0.168±0.03‰, with an average value of 0.154±0.04‰ and a coefficient of variation of 7.84%. Generally, it is comparable to continental igneous rocks. Compared with the soil matrix, δ 56 Fe of the iron-manganese film is smaller, ranging from 0.048±0.01‰ to 0.074±0.07‰, with an average value of 0.066±0.03‰ and a relatively large coefficient of variation of 16.06%. The δ 56 Fe difference between the soil matrix and the iron-manganese film indicates that the soil matrix is enriched in heavy iron isotopes while the iron-manganese film is enriched in light iron isotopes. δ 56 Fe of the iron-manganese nodules with a particle size of 0.5-1mm ranges from -0.695±0.03‰ to -0.471±0.04‰, with an average value of 0.564±0.03‰ and a coefficient of variation of 17.52%. The iron isotope composition is significantly enriched in light iron. δ 56 Fe of the iron-manganese nodules with a particle size of 1-2mm ranges from -0.746±0.02‰ to -0.591±0.03‰, with an average value of -0.673±0.03‰ and a coefficient of variation of 12.08%. The iron isotope composition is lighter. It can be seen that the iron isotope shows the trend of soil matrix>iron-manganese film>0.5-1mm iron-manganese nodules>1-2mm iron-manganese nodules. Magnesium in the iron-manganese nodules mainly comes from the pore fluid (soil aqueous solution). The ion exchange between the pore fluid and the iron oxide and clay minerals preferentially replaces the heavy magnesium isotope in the minerals, making the iron-manganese nodules enriched in light magnesium isotopes.

[0070] Different from the understanding of the prior art, using the soil iron isotope determination sample sampling method and iron isotope composition determination method proposed in this application, it is possible to find that the enrichment area and leaching area at the microscale and the iron isotope composition change of the iron-manganese neoformed body are relatively large, especially the δ 56Fe changes greatly. The iron isotope fractionation mechanism well traces the short-distance migration of iron during the formation of the loess-paleosol sequence profile, as well as the migration path of light iron isotopes from the matrix to the iron-manganese nodules. The migration and transformation of iron mainly occur in microdomains, while iron isotope fractionation mainly occurs in microdomains within the well-developed soil layer.

[0071] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A soil iron isotope determination sampling method, characterized in that: The steps include: Collect stratigraphic scale samples to select samples with higher or lower iron content from top to bottom in different strata based on the total iron content, which can represent the overall characteristics of the strata, and use them to determine the iron isotope composition of the stratigraphic scale samples; Collect samples at the level of the soil layer to divide the soil genetic layers in each layer according to soil characteristics, and collect soil genetic layer samples from bottom to top; Collect micro-scale samples to collect paired iron isotope determination samples from micro-domain high iron leaching area, low iron leaching area, high iron enrichment area and low iron enrichment area according to the different degrees of iron leaching and enrichment; Collect new body-scale samples to collect ferromanganese nodules in areas with abundant ferromanganese nodules, and simultaneously collect matrix soil around the ferromanganese nodules to determine the iron isotope composition of the ferromanganese nodules and their surrounding matrix; After transporting the collected samples indoors, place them in a cool and dry place to air-dry, pass them through a 100-mesh nylon sieve, and set aside.

2. The soil iron isotope determination sampling method according to claim 1, characterized in that: The collection of stratigraphic scale samples includes: first, determining the stratigraphic boundaries with time control significance based on the soil color, texture, structure, and profile morphological characteristics of the new body, and collecting dating samples at the stratigraphic boundaries, and using the optically stimulated luminescence dating method to determine the formation age of the soil to obtain the soil age limit; second, based on the differences between the profile morphological characteristics of the soil and the age limit, different strata are divided according to the stratigraphic division standards to construct a sequence.

3. The soil iron isotope determination sampling method according to claim 2, characterized in that: Collect stratigraphic scale samples, including: Use a hard plastic shovel to remove about 5 cm thick topsoil from top to bottom, remove the loose soil, and collect samples at equal intervals of 20 cm from top to bottom to determine the content of iron in different forms.

4. The soil iron isotope determination sampling method according to claim 3, characterized in that: Collect micro-scale samples, including: Based on the color, texture, structure, and morphological characteristics of the new bodies in the soil profile, the characteristic layers of the iron-rich leaching area and the iron-enriched area below are determined.

5. The soil iron isotope determination sampling method according to claim 4, characterized in that: The color of the iron-lost area is mainly light yellow or white, and the lighter the color, the higher the degree of leaching; the color of the iron-enriched area is mainly rust or red, and the redder the color, the higher the degree of iron enrichment.

6. The soil iron isotope determination sampling method according to claim 5, characterized in that: Collect newborn-scale samples, including: Large original soil samples enriched with iron-manganese film were collected, and the film on the surface of the soil block was scraped off with a rustless steel blade indoors to collect the film samples. At the same time, soil matrix samples with the film scraped off were collected to determine the iron isotope composition of the iron-manganese film and its soil matrix.

7. The soil iron isotope determination sampling method according to claim 6, characterized in that: When scraping the rubber film on the surface of the soil block, the scraped thickness shall not exceed 1mm.

8. The soil iron isotope determination sampling method according to claim 7, characterized in that: Iron-manganese nodules include 0.5-1mm iron-manganese nodules and 1-2mm iron-manganese nodules.

9. A method for determining iron isotope composition, characterized in that: The method is used to determine the iron isotope composition in a soil sample collected by the soil iron isotope determination sampling method according to any one of claims 1 to 8, comprising: First, each soil sample was weighed and digested with HNO3-HCl-HClO4 mixed acid, and the digestion solution was evaporated to dryness and then dissolved with 6NHCl; Secondly, cation exchange resin is used to purify the iron to a recovery rate of 99.5%; Finally, the purified iron solution was diluted with 2% HNO3 to prepare the test solution, and the iron isotope composition was determined by a multi-acceptor inductively coupled plasma mass spectrometer; the DCB method was used to extract the iron isotopes of free iron and silicate-bound iron, and the iron isotope composition was calculated by comparing the measured value with the standard value of the international standard material IRMM-014.

10. The method for determining the iron isotope composition according to claim 1, characterized in that: The iron isotope is calculated using the following formula composition: In the above formula, ( 56 Fe / 54 Fe) Sample is the measured value; ( 56 Fe / 54 Fe) IRMM-014 It is the standard value of the international standard material IRMM-014.

Images