CN113340691B - Method for extracting phosphorus with different occurrence forms in marine sediment - Google Patents

Abstract

The present invention provides a method for extracting phosphorus in different forms of occurrence in marine sediments. The extraction method of the present invention is to carry out continuous graded leaching of marine sediment samples, and use different extractants to extract phosphorus in the samples step by step, so as to Obtain phosphorus in different forms. The extraction method of the present invention can comprehensively extract phosphorus in different forms of occurrence in marine sediments, has a high extraction rate, and facilitates systematic research on phosphorus forms in the ocean.

Description

A method for extracting different forms of phosphorus in marine sediments

Technical field

The present invention relates to the field of environmental technology, and in particular to a method for extracting phosphorus in different forms present in marine sediments.

Background technique

Phosphorus is an essential component for the growth and reproduction of marine plankton and is the basis of marine primary productivity and the food chain. River input is the main source of phosphorus in the ocean, and sediments are an important reservoir of phosphorus in the water body. The exchange of phosphorus between the two is significant. However, the amount of bioavailable phosphorus that can participate in the exchange depends on the form of phosphorus in the sediment. When the temperature, pH value, bioturbation and other factors of the sedimentary environment change, only weakly adsorbed phosphorus, occluded phosphorus, iron/aluminum adsorbed phosphorus, and organic phosphorus can diffuse from the sediment to the overlying water body and be absorbed by organisms. utilization, thereby affecting the phosphorus content in the marine water environment. Therefore, the occurrence form of phosphorus in marine sediments is of great significance for quantifying the upper limit of potential biologically available phosphorus, obtaining relevant information about the sedimentary environment, understanding the recycling of phosphorus in the ocean, and controlling endogenous pollution.

The existing technology discloses a variety of methods for separating and quantifying phosphorus forms in marine sediments. The most ideal is the chemical reagent extraction method, which mainly includes: Rutternberg method, Jensen (1998) method, and Kaarina's improved method. However, the Rutternberg method only focuses on the separation of detrital phosphorus and authigenic phosphorus. This method is not enough to separate other forms of phosphorus. For example, what is extracted in the second step is actually aluminum-bound phosphorus (Al-P), iron-bound phosphorus ( Fe-P) and the sum of occluded phosphorus, if it is only considered to be Fe-P, it would be too biased; Jensen (1998) improved it based on the Rutternberg method and further refined the form of phosphorus in sediments, dividing the main sedimentary phosphorus into Divided into six parts: weakly adsorbed phosphorus (Lsor-P), iron-bound inorganic phosphorus (Fe-P), extractable organic phosphorus (Lea-OP), authigenic apatite (CAFP), and detrital apatite (FAP) and stabilized organophosphorus (Ref-OP); Kaarina’s improved method separated phosphorus and alumina in the iron-manganese bound state that is sensitive to the redox environment, phosphorus and organophosphorus in irreducible iron oxides, but failed to distinguish the native Detrital phosphorus and authigenic phosphorus in sedimentary environments.

Since many existing hierarchical leaching methods of phosphorus forms fail to systematically and completely extract and analyze the existing forms of phosphorus in sediments, based on this, the present invention combines the advantages of various previous hierarchical leaching methods and proposes a method for extracting marine phosphorus. Methods for different forms of phosphorus in sediments to refine bioavailable phosphorus, further improve and focus on the research requirements of environmental geochemistry.

Contents of the invention

In view of this, in order to solve the technical problem that existing extraction methods cannot completely extract phosphorus in different forms of occurrence in sediments, the present invention provides a method for extracting phosphorus in different forms of occurrence in marine sediments, with the purpose of being able to systematically and completely Extraction of different forms of phosphorus in marine sediments.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for extracting phosphorus in different forms of occurrence in marine sediments, including the following steps:

1) Use MgCl ₂ solution with a pH value of 8 as an extractant to extract marine sediment samples, and obtain residue a and an extract containing weakly adsorbed phosphorus after centrifugal separation;

2) Use a CDB solution with a pH value of 7.6 as an extractant to extract the residue a in step 1). After centrifugation, obtain the residue b and the supernatant. After digesting the supernatant with strong acid at high temperature, cool it to obtain a transparent solid. , and use water to dissolve the transparent solid, and adjust the pH value to 3.0~3.1 to obtain an extract containing occluded phosphorus;

3) Use NaOH solution as the extractant to extract the residue b in step 2), and obtain the residue c and the extract containing iron/aluminum adsorbed phosphorus after centrifugation;

4) Use NaAC-HAC buffer as the extraction agent to extract the residue c in step 3), obtain the residue d and the supernatant after centrifugation, adjust the pH value of the supernatant to 3.0-3.1, and obtain autogenous phosphorus-containing phosphorus. Extracts of stone and calcium-bound phosphorus;

5) Use HCl solution as the extractant to extract the residue d in step 4), obtain the residue e and the supernatant after centrifugation, adjust the pH value of the supernatant to 3.0-3.1, and obtain detrital apatite-containing Extract;

6) After burning and cooling the residue e in step 5) at high temperature, use HCl solution as the extractant to extract, obtain the residue f and the supernatant after centrifugation, and adjust the pH value of the supernatant to 3.0-3.1 , to obtain an extract containing organophosphorus;

7) After high-temperature digestion and cooling of the residue f in step 6), use HCl solution as the extraction agent for extraction. After centrifugation, adjust the pH value of the supernatant to 3.0~3.1 to obtain silicate-containing debris. Phosphorus extract.

Preferably, the concentration of the MgCl ₂ solution in step 1) is 1 mol/L, and the preparation method is: dissolve 203.3g MgCl ₂ ·6H ₂ O in 1 L of ultrapure water, and adjust the pH to 8 with 10% NH ₄ OH.

Preferably, the CDB solution in step 2) is prepared by dissolving 32.4g C ₆ H ₅ Na ₃ O ₇ ·2H ₂ O, 42g NaHCO ₃ , and 2.87g Na ₂ S ₂ O ₄ in 500 mL of ultrapure water, and is prepared on the same day.

Preferably, step 2) high-temperature digestion is to take part of the supernatant in a 100ml digestion tube and use a mixed solution of sulfuric acid, perchloric acid and nitric acid in a volume ratio of 1:2:7 as the digestion agent, in which sulfuric acid is superior grade. Pure, with a sulfuric acid content of 95% to 98%, and a density of 1.84g/cm ³ ; nitric acid is superior grade pure, with a nitric acid content of 65% to 68%; perchloric acid is produced by Tianjin Dongfang Chemical Plant.

Preferably, the concentration of the NaOH solution in step 3) is 0.1 mol/L.

Preferably, the pH value of the NaAC-HAC buffer in step 4) is 4, and the concentration is 1 mol/L.

Preferably, the concentration of HCl solution used in step 5), step 6) and step 7) is 1 mol/L.

Preferably, the temperature of high-temperature burning in step 6) is 550°C, and the burning time is 4 hours.

Preferably, the acid enhanced for digestion in step 7) is concentrated sulfuric acid and perchloric acid.

Preferably, the present invention uses the ascorbic acid reduction phosphomolybdenum blue method (GB/T 12763.4-2007) to respectively measure the content of weakly adsorbed phosphorus in the phosphorus form extraction solution in the first step and the occluded phosphorus in the phosphorus form extraction solution in the second step. content, the content of iron/aluminum adsorbed phosphorus in the phosphorus form extraction solution in the third step, the content of authigenic apatite and calcium-bound phosphorus in the phosphorus form extraction solution in the fourth step, the detrital phosphorus in the phosphorus form extraction solution in the fifth step The content of limestone, the content of organic phosphorus in the phosphorus form extraction solution in the sixth step, and the silicate detrital phosphorus content in the phosphorus form extraction solution in the seventh step.

Compared with the existing technology, the present invention has the following beneficial effects: the present invention extracts and analyzes phosphorus forms in marine sediments through a continuous graded leaching method, and can fully obtain phosphorus in different forms from marine sediments. Accurately reflects the presence and bioavailability of phosphorus in marine sediments. The extraction method of the present invention requires a small amount of marine sediment samples, and the chemical reagents used are simple and low in cost.

Description of drawings

Figure 1 is a sampling station location map of Embodiments 1-12 of the present invention;

Figure 2 is a flow chart for extracting phosphorus in different forms of occurrence in marine sediments according to the present invention;

Figure 3 is a schematic diagram of the distribution of phosphorus in different forms in Examples 1-12 of the present invention.

Detailed ways

The present invention proposes a method for extracting phosphorus in different forms of occurrence in marine sediments, which includes the following steps:

1) Mix the marine sediment and 1 mol/L magnesium chloride solution with a pH value of 8 evenly using a vortex mixer. After shaking and extracting the mixture at room temperature for 2 hours, centrifuge at a speed of 5000 r/min for 15 minutes to obtain residue a and the first One-step phosphorus form extraction solution. The first step of the phosphorus form extraction solution obtained in this step contains weakly adsorbed phosphorus (Lsor-P). The marine sediments in this step are collected from the surface layer of about 10cm in the sea area under study through a grab sampler. For the sample, add dropwise ammonia water with a mass concentration of 10 wt% into the 1 mol/L magnesium chloride solution to adjust the pH value of the magnesium chloride solution to 8.

2) Mix the residue a and the CDB solution with a pH value of 7.6 evenly. After shaking and extracting for 6 hours, centrifuge at a speed of 5000r/min for 15 minutes to obtain the residue b and the supernatant. Measure 5 ml of the supernatant into the digestion tube and press Sulfuric acid, perchloric acid, and nitric acid were added at a volume ratio of 1:2:7, followed by high-temperature digestion. The sulfuric acid was of superior purity, with a sulfuric acid content of 95% to 98% and a density of 1.84g/cm ³ ; nitric acid It is superior grade pure, with a nitric acid content of 65% to 68%; perchloric acid is produced by Tianjin Dongfang Chemical Factory. It will be used until the perchloric acid and nitric acid are completely decomposed and sulfuric acid is refluxed. After cooling, a transparent solid will appear. After adding water to dissolve The liquid is the second step phosphorus form extraction liquid, which can also be dissolved by adding water and boiling.

The CDB solution is prepared by dissolving 32.4g C ₆ H ₅ Na ₃ O ₇ ·2H ₂ O, 42g NaHCO ₃ , and 2.87g Na ₂ S ₂ O ₄ in 500 mL ultrapure water.

In this step, use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extraction solution in the second step to 3.0-3.1 to obtain occluded phosphorus (Oc-P). Extract liquid.

3) Mix residue b with 0.1 mol/L sodium hydroxide solution evenly, shake and extract for 18 hours, and then centrifuge at 5000 r/min for 15 minutes to obtain residue c and the third step phosphorus form extraction solution.

4) Mix the residue c with 1 mol/L NaAC-HAC buffer with pH=4, shake and extract for 5 hours, and then centrifuge at a speed of 5000 r/min for 15 minutes to obtain the residue d and the fourth step phosphorus form extract;

In this step, 1 mol/L hydrochloric acid is used to adjust the pH of the phosphorus form extraction solution in the fourth step to 3.0-3.1 to obtain an extract solution containing authigenic apatite and calcium-bound phosphorus (Ca-P).

5) Mix the residue d with 1 mol/L hydrochloric acid evenly, shake and extract for 16 hours, and then centrifuge at a speed of 5000 r/min for 15 minutes to obtain the residue e and the fifth step phosphorus form extraction solution;

In this step, use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extraction solution in the fifth step to 3.0-3.1 to obtain detrital apatite (De-P). of the extract.

6) Transfer all the residue e to the crucible, place it in a muffle furnace, and ashe it at 550°C for 4 hours. Mix the ashed and cooled residue e with 1 mol/L hydrochloric acid evenly. After shaking and extracting for 15 hours, centrifuge at a speed of 5000 r/min for 15 minutes to obtain the residue f and the phosphorus form extract in step 6.

In this step, use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extraction solution in the sixth step to 3.0-3.1 to obtain an extract solution containing organophosphorus (OP).

7) Transfer the entire amount of the residue f to the digestion tube, add 4 ml of high-grade pure concentrated sulfuric acid with a sulfuric acid content of 95% to 98%, and 5 drops of perchloric acid, and perform high-temperature digestion until all the residue turns white, then continue digestion for 20 minutes; naturally After cooling, mix it evenly with 1mol/LHCl, oscillate and extract for 8 hours, and centrifuge at 5000r/min for 15min to obtain the phosphorus form extraction solution in the seventh step.

In this step, use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extraction solution in the seventh step to 3.0-3.1 to obtain silicate crumb state phosphorus (SIF- P) extract.

By using the above method to extract phosphorus in different forms of occurrence in marine sediments, the present invention can systematically and completely analyze and study the existence forms and bioavailability of phosphorus in the ocean.

The present invention adopts the ascorbic acid reduction phosphomolybdenum blue method (GB/T 12763.4-2007) to respectively measure the content of weakly adsorbed phosphorus (Lsor-P) in the phosphorus form extraction solution in the first step, and the content of occlusion in the phosphorus form extraction solution in the second step. The content of phosphorus (Oc-P), the content of iron/aluminum adsorbed phosphorus (Fe/Al-P) in the phosphorus form extraction solution in the third step, authigenic apatite and calcium-bound phosphorus in the phosphorus form extraction solution in the fourth step (Ca-P) content, the content of detrital apatite (De-P) in the phosphorus form extraction solution in the fifth step, the organic phosphorus (OP) content in the phosphorus form extraction solution in the sixth step, the phosphorus form in the seventh step The content of silicate fragment phosphorus (SIF-P) in the extract.

Use Excel, Origin, Surfer and other data statistics, analysis software and drawing software to further analyze its relative content and spatial distribution.

The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. The marine sediment samples used in the following examples of the present invention were sediment samples with a surface thickness of about 10 cm that were collected using grab samplers at 12 stations in the coastal waters of Bohai Bay in October 2019, and were mixed on site and sealed. Store in a polyethylene sealed bag at 4°C. The sampling station is as shown in Figure 1.

Example 1

A method for extracting different forms of phosphorus in marine sediments is described with reference to Figure 2. The specific steps are as follows:

In October 2019, the inventor of the present invention used a grab sampler to collect sediment samples with a surface thickness of about 10cm at 12 stations in the coastal waters of the Bohai Bay. They mixed them on site and sealed them in polyethylene sealing bags. , stored at 4°C.

The 12 sediment samples collected above were extracted and measured in different forms of phosphorus according to the following steps. The specific implementation flow chart is shown in Figure 2. The detailed steps are as follows:

Step 1: Add 20ml of 1mol/L MgCl ₂ (pH=8) to the 1# wet sediment sample equivalent to 1g of dry sample, place it on a vortex mixer, mix the sediment sample and the extractant evenly, and mix at 25 ℃, place it on a Conis shaker and oscillate at 200r/min for extraction for 2h, centrifuge at 5000r/min for 15min to obtain residue a and supernatant, and take the supernatant to obtain the first step of phosphorus form extraction solution. The content of weakly adsorbed phosphorus (Lsor-P) in the phosphorus form extraction solution in the first step was measured.

Step 2: Add 20 ml of a mixed solution of C ₆ H ₅ Na ₃ O ₇ ·2H ₂ O, NaHCO ₃ and Na ₂ S ₂ O ₄ with a pH of 7.6 to residue a, mix evenly, and shake and extract at 25°C for 6 hours. Centrifuge at 5000r/min for 15min to obtain residue b and supernatant. Take 5ml of the supernatant and put it into a 100ml digestion tube. Add 5ml of strong acid with a volume ratio of sulfuric acid, perchloric acid and nitric acid of 1:2:7. Then the digestion is carried out on the digestion instrument, and the temperature is gradually increased until the perchloric acid and nitric acid are completely decomposed. The digestion ends when sulfuric acid refluxes. After cooling, a white and transparent solid will appear. The liquid after adding water to dissolve it is the second step phosphorus form extraction solution. Add a drop of 2,4-dinitrobenzene, mix well, use 0.1mol/L sodium hydroxide solution or 10mol/L sodium hydroxide solution to adjust the pH of the second step phosphorus form extraction solution to 3.0-3.1, and measure the The content of occluded phosphorus (Oc-P).

Step 3: Add 20 ml of 0.1 mol/L NaOH to residue b, mix evenly, shake and extract at 25°C for 18 hours, and centrifuge at 5000 r/min for 15 minutes to obtain the extract of residue c and the third step of phosphorus form. The content of iron/aluminum adsorbed phosphorus (Fe/Al-P) in the phosphorus form extraction solution in the third step was measured.

Step 4: Add 20ml of 1mol/L NaAC-HAC buffer with a pH of 4 to the residue c, mix evenly, shake and extract at 25°C for 5 hours, and centrifuge at 5000r/min for 15min to obtain the extract of the residue d and the phosphorus form in the fourth step. , use 1 mol/L hydrochloric acid to adjust the pH of the phosphorus form extraction solution in the fourth step to 3.0-3.1, and measure the content of autogenous apatite and calcium-bound phosphorus (Ca-P).

Step 5: Add 20ml of 1mol/L HCl to the residue d, mix evenly with a vortex mixer, oscillate and extract at 25°C for 16 hours, and centrifuge at 5000r/min for 15min to obtain the extract of the residue e and the phosphorus form in the fifth step. Use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extraction solution in the fifth step to 3.0-3.1. The content of detrital apatite (De-P) in the phosphorus form extraction solution in the fifth step was measured.

Step 6: Transfer all the residue e to a porcelain crucible, place it in a muffle furnace, burn it at 550°C for 4 hours, transfer it all back to the centrifuge tube after cooling, add 20ml 1mol/L HCl, mix evenly, and heat at 25°C Extract with oscillation for 15 hours, and centrifuge at 5000r/min for 15 minutes to obtain the residue f and the sixth step phosphorus form extract. Use 0.1 mol/L sodium hydroxide solution or 10 mol/L sodium hydroxide solution to separate the sixth step phosphorus form extract. Adjust the pH to 3.0-3.1. Determine the content of organophosphorus (OP) in the phosphorus form extraction solution in the sixth step.

Step 7: Transfer the entire amount of residue f to the digestion tube, add 4 ml of concentrated sulfuric acid and 5 drops of perchloric acid, and digest it until everything turns white. Continue the digestion for 20 minutes. After natural cooling, add 20 ml of 1mol/L HCl and transfer it back to the centrifuge tube. , shake and extract for 8 hours, and centrifuge for 15 minutes to obtain the phosphorus form extract in the seventh step. Use 0.1mol/L sodium hydroxide solution or 10mol/L sodium hydroxide solution to adjust the pH of the phosphorus form extract in the seventh step to 3.0-3.1 . The content of silicate fragment phosphorus (SIF-P) in the phosphorus form extraction solution in the seventh step was measured.

Example 2-12

Marine sediment samples 2#-12# were processed in the same manner as in Example 1, and phosphorus in different forms was obtained.

The measurement results of Examples 1-12 are shown in Figure 3.

It can be seen from Figure 3 that using the hierarchical extraction method of the present invention, seven different forms of phosphorus can be obtained from marine sediment samples. At the same time, there are significant differences in the phosphorus content of various forms. As shown in Figure 3, the changes in the phosphorus content of each form are in the order of detrital apatite (De-P) > organic phosphorus (OP) > occluded phosphorus (Oc-P) > silicate detrital phosphorus (SIF- P)> Iron/aluminum adsorbed phosphorus (Fe/Al-P)> authigenic apatite and calcium-bound phosphorus (Ca-P)> weakly adsorbed phosphorus (Lsor-P), while the crushed phosphorus in samples 1-12 Detrital apatite (De-P), organic phosphorus (OP), occluded phosphorus (Oc-P), silicate detrital phosphorus (SIF-P), iron/aluminum adsorbed phosphorus (Fe/Al- The average proportions of P), authigenic apatite and calcium-bound phosphorus (Ca-P), and weakly adsorbed phosphorus (Lsor-P) are: 53.95%, 15.89%, 11.78%, 9.01%, 5.66%, 2.80 respectively %, 0.91%.

Among them, the weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus ( The proportions of Ca-P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) are respectively: 0.76%, 18.99%, 8.22%, and 2.69 %, 49.19%, 12.30%, 7.85%.

In sample 2#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 0.85%, 6.25%, 3.37%, and 2.28% respectively. , 69.09%, 10.56%, 7.61%.

In sample 3#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 1.16%, 16.24%, 5.87%, and 5.76% respectively. , 42.51%, 20.75%, 7.72%.

In sample 4#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 1.04%, 16.21%, 8.08%, and 3.28% respectively. , 45.27%, 18.93%, 7.19%.

In sample 5#, the above-mentioned weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 1.01%, 8.95%, 7.60%, and 2.47% respectively. , 52.86%, 16.94%, 10.16%.

In sample 6#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 1.26%, 17.06%, 3.90%, and 3.04% respectively. , 54.34%, 13.05%, 7.34%.

In sample 7#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 0.93%, 9.97%, 7.26%, and 3.00% respectively. , 51.55%, 19.87%, 7.43%.

In sample 8#, the above-mentioned weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) are respectively: 0.52%, 9.72%, 3.35%, and 1.75% , 68.02%, 9.43%, 7.21%.

In sample 9#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 0.90%, 11.56%, 5.84%, and 1.63% respectively. , 54.47%, 17.28%, 8.32%.

In sample 10#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) are respectively: 0.95%, 7.28%, 5.80%, and 2.53% , 54.64%, 16.65%, 12.14%.

In sample 11#, the above weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 0.76%, 10.06%, 4.64%, and 2.42% respectively. , 49.24%, 19.48%, 13.39%.

In sample 12#, the above-mentioned weakly adsorbed phosphorus (Lsor-P), occluded phosphorus (Oc-P), iron/aluminum adsorbed phosphorus (Fe/Al-P), authigenic apatite and calcium-bound phosphorus (Ca -P), detrital apatite (De-P), organic phosphorus (OP), and silicate detrital phosphorus (SIF-P) account for 0.83%, 9.02%, 4.01%, and 2.77% respectively. , 56.18%, 15.48%, 11.71%.

In addition, a method for extracting phosphorus in different forms present in marine sediments proposed in the embodiment of the present invention was verified with a standard material (GBW07333). The improved continuous graded leaching method of phosphorus occurrence forms in marine sediments was used to analyze the phosphorus form of the Yellow Sea marine sediment standard material (GBW07333). The precision of each step in the seven-step continuous graded leaching is as follows: Step 1: 2.7%, second step: 4.5%, third step: 1.9%, fourth step: 3.2%, fifth step: 4.1%, sixth step: 1.6%, seventh step: 2.7%, measured seven-step phosphorus form The error range between the sum and the standard value is 6.3% to 10.3%. Therefore, the method proposed by the embodiment of the present invention to extract phosphorus in different forms in marine sediments through continuous graded leaching can be applied to the separation and extraction of phosphorus forms in marine sediments.

The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (6)

1. A method for extracting phosphorus in different occurrence forms in marine sediments, which is characterized by comprising the following steps:

1) Using MgCl with pH 8 ₂ Extracting a marine sediment sample by taking the solution as an extracting agent, and obtaining residue a and an extracting solution containing weakly adsorbed phosphorus after centrifugal separation;

2) Extracting the residue a in the step 1) by using CDB solution with the pH value of 7.6 as an extracting agent, centrifuging to obtain residue b and supernatant, carrying out high-temperature digestion on the supernatant by using strong acid, cooling to obtain transparent solid, dissolving the transparent solid by using water, and regulating the pH value to 3.0-3.1 to obtain an extracting solution containing closed-state phosphorus;

3) Extracting the residue b in the step 2) by using NaOH solution as an extracting agent, and centrifugally separating to obtain residue c and an extracting solution containing iron/aluminum adsorption phosphorus;

4) Extracting the residue c in the step 3) by using NaAC-HAC buffer solution as an extracting agent, centrifuging to obtain residue d and supernatant, and regulating the pH value of the supernatant to 3.0-3.1 to obtain an extracting solution containing autogenous apatite and calcium-bound phosphorus;

5) Extracting the residue d in the step 4) by using HCl solution as an extracting agent, centrifuging to obtain residue e and supernatant, and regulating the pH value of the supernatant to 3.0-3.1 to obtain an extracting solution containing clastic apatite;

6) Burning and cooling the residue e in the step 5) at high temperature, extracting by adopting an HCl solution as an extracting agent, centrifuging to obtain residue f and supernatant, and regulating the pH value of the supernatant to 3.0-3.1 to obtain an extracting solution containing organic phosphorus;

7) Digesting the residue f in the step 6), cooling, extracting by adopting an HCl solution as an extracting agent, and regulating the pH value of supernatant fluid to 3.0-3.1 after centrifugal separation to obtain an extracting solution containing silicate clastic phosphorus;

step 2) high-temperature digestion is to adopt a mixed solution composed of sulfuric acid, perchloric acid and nitric acid with the volume ratio of 1:2:7 as a digestion agent for part of supernatant;

the concentration of the NaOH solution in the step 3) is 0.1mol/L.

2. The method for extracting phosphorus in different occurrence forms from marine sediments according to claim 1, wherein step 1) said MgCl ₂ The concentration of the solution is 1mol/L, and ammonia water with the mass concentration of 10wt% is added dropwise to adjust the pH value of the extractant to 8.

3. The method for extracting phosphorus in different occurrence forms from marine sediments as recited in claim 1, wherein said CDB solution of step 2) is obtained by using 32.4gC ₆ H ₅ Na ₃ O ₇ ·2H ₂ O、42gNaHCO ₃ 、2.87gNa ₂ S ₂ O ₄ Is dissolved in 500mL of ultrapure water.

4. The method of claim 1, wherein the NaAC-HAC buffer in step 4) has a pH of 4.

5. The method for extracting phosphorus in different occurrence forms from marine sediments according to claim 1, wherein the concentration of the HCl solution adopted in the steps 5), 6) and 7) is 1mol/L.

6. The method for extracting phosphorus in different occurrence forms from marine sediments according to claim 1, wherein the high-temperature firing temperature in the step 6) is 550 ℃ and the firing time is 4 hours.