In-situ determination method of marine sediment sulfate reduction rate

Abstract

The invention relates to the field of detection, in particular to an in-situ determination method for the reduction rate of marine sediment sulfate. According to the in-situ determination method provided by the invention, a certain amount of < 34S > stable isotope labeled SO4 < 2-> (wherein the abundance of < 34S > is far higher than the abundance of < 34S > in SO4 < 2-> under natural conditions by 4.2%) is injected into the sediment, when SO4 < 2-> is reduced, labeled SO4 < 2-> and non-labeled SO4 < 2-> are converted into S < 2-> in equal proportion, and at the moment, the abundance of < 34S > in the generated S < 2-> is increased. The 34S abundance difference of S < 2-> in the sediment before the SO4 < 2-> is marked (contrast CK) and after the SO4 < 2-> is marked for a period of time (delta T) is measured, and the reduction rate of the sulfate can be calculated in combination with measurement of other related parameters. The method can be used for in-situ determination of the marine sediment sulfate reduction rate, the determination result accords with objective laws and is high in accuracy, and the determination process is simple, safe and stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of detection, and particularly to a method for in-situ determination of sulfate reduction rate of marine sediments. BACKGROUND

[0002] Sulfur is an essential element for life and plays a key role in the global carbon and sulfur cycles. 32 S、 33 S、 34 S、 36 S There are four stable isotopes of sulfur, S, S, S, and S, with natural abundances of 95.02%, 0.75%, 4.21%, and 0.02%, respectively. Sulfate reduction to sulfide is one of the main processes of sediment metabolism and diagenesis in most sediments, and it plays an important role in regulating the physical, chemical, and biological processes of marine sediments. The chemical equation of sulfate reduction can be expressed as: .

[0003] The surface layer of marine sediments is usually in an anaerobic state, and the metabolic activity of anaerobic microbial communities is dominant, including denitrification, methanogenesis, and sulfate reduction, of which sulfate reduction is the most important. Sulfate-reducing bacteria are obligate anaerobes and play a key role in the anaerobic mineralization of organic matter. In some coastal sediments, sulfate-reducing bacteria catalyze more than 50% of the organic matter respiratory oxidation. This emphasizes the importance of accurately measuring this process in nature.

[0004] Sulfate reduction in marine sediments is an important biogeochemical process in anaerobic environments, which dominates organic matter mineralization and sulfur cycling, and the determination of its rate is crucial for understanding the carbon and sulfur cycles. The traditional method for determining the rate of sulfate reduction is to measure the consumption rate of the substrate (SO4 2- ) or the generation rate of the product (S 2- ). The problem with using the substrate consumption method is that there is a large amount of SO4 2- in the marine environment, and after the anaerobic consumption of SO4 2- , it can be replenished through diffusion, interstitial water exchange, etc., so it is not possible to accurately measure the consumption of SO4 2- . The problem with using the product generation method is that the anaerobic reduction rate of marine sediments is usually low, generally less than 1 μmol·cm -3 ·day -1 , and the current method for analyzing the content of sulfides in sediments cannot accurately determine such a low difference in sulfide content, resulting in a large error in the measurement results.

[0005] The current commonly used method is to use radioactive 35S to measure the sulfate reduction rate of sediments (literature "Study on sulfate reduction rate of salt marsh soil in the Waste Yellow River Estuary (Sun Bingyin and Jing Meide, 1990)"), the process is to inject radioactive labeled 35 SO4 2- , after incubation (several hours to several days), the generated 35 S 2- (hydrogen sulfide H2S or chromium-reduced sulfide) is measured, and the reduction rate is calculated by radioactivity. This method has high accuracy, but it must use radioactive isotopes 35 S, so there is a risk of radioactive hazards to health and safety, and the test conditions and detection conditions are high, the determination process needs strict protection and waste treatment, which limits the field application. SUMMARY

[0006] Therefore, the technical problem to be solved by the present application is to provide an in-situ determination method for the sulfate reduction rate of marine sediments. The in-situ determination method provided by the present application can determine the sulfate reduction rate of marine sediments in-situ, the determination result conforms to the objective law and has high accuracy, the determination process is simple, safe and stable.

[0007] The present application provides an in-situ determination method for the sulfate reduction rate of marine sediments, comprising the following steps:

[0008] S1) sampling the marine sediments at the detection site of marine sediments to obtain a control sample of the detection sediments and a detection sample of the detection sediments after standard addition and incubation;

[0009] The detection sample of the detection sediments after standard addition and incubation is obtained by the following steps:

[0010] 34 S labeled Na2SO4 is added to the marine sediments at the detection site of marine sediments, and then incubated to obtain the detection sample of the detection sediments after standard addition and incubation; the 34 S labeled Na2SO4 has a 34 S abundance of more than 4.2%, and the 34 S labeled Na2SO4 is added in an amount not more than 10 wt% of the background value of sulfate content of the detection sample of the detection sediments;

[0011] S2) obtaining the abundance of sulfide 34 S in the control sample of the detection sediments of step S1), and the content of sulfide, the abundance of sulfide 34 S and the abundance of sulfate 34 S in the detection sample of the detection sediments after standard addition and incubation;

[0012] S3) according to the abundance of sulfide 34 ​S abundance and sulfide content in the spiked cultured sediment sample, sulfide 34 S abundance and sulfate 34 S abundance yields the sulfate reduction rate of the sediment.

[0013] This invention first samples marine sediments from a test site to obtain a control sample and a spiked, cultured sample for analysis. Specifically, a control sampling tube and a analysis tube are simultaneously inserted into the test site, allowing the marine sediments to enter both tubes. The control sampling tube is then sealed and removed from the test site to obtain the control sample. 34 S-labeled Na2SO4 is added to the marine sediment at the test site in the sediment sampling and testing tube, and then cultured. After the sediment sampling and testing tube is sealed, it is taken out from the test site to obtain the spiked and cultured sediment sample.

[0014] This invention requires ensuring the integrity of the marine sediments at the test sites within the sediment sampling control tube and sediment sampling measurement tube. The invention employs a sealing process for the sediment sampling control tube and sediment sampling measurement tube to prevent oxygen from entering and affecting sulfide oxides. The sampling interval between the control sample and the spiked, cultured sample should not exceed 1 meter to ensure, as far as possible, the physicochemical properties of the same layer within both tubes are consistent.

[0015] After obtaining the control sample of the sediment to be tested, the present invention further includes freezing the control sample; specifically, the sediment sampling control tube taken directly from the marine sediment testing site is sealed and then frozen; the freezing temperature is below -15°C. The freezing treatment of the present invention can reduce the activity of internal microorganisms and stop the biochemical reactions within the tube.

[0016] This invention will 34 S-labeled Na₂SO₄ is added to the marine sediments at the target testing site, followed by incubation to obtain a spiked sediment sample. This allows for in-situ reduction of sulfate in the marine sediments at the target testing site, reducing interference factors and ensuring accurate measurement results. The spiked sediment sample is obtained through the following steps: using a specially designed injection needle... 34S-labeled Na2SO4 is added to the marine sediment at the target site, the specially designed injection needle remains in the marine sediment at the target site and is sealed, and then cultured to obtain the spiked cultured sample.

[0017] The specially designed injection needle of this invention has a length comparable to that of the sediment sampling control tube and the sediment sampling measurement tube. The tube wall of the specially designed injection needle is uniformly provided with multiple small holes, allowing the entire needle tube to be injected. 34 S-labeled Na2SO4.

[0018] The present invention 34 S-labeled Na2SO4 specifically refers to 34 S-labeled Na2SO4 solution, more specifically, solution after thoroughly purging with a protective gas to remove dissolved oxygen. 34 S-labeled Na₂SO₄ solution. The present invention... 34 S-labeled Na2SO4 34 S abundance is higher than 4.2%, preferably higher than 10%. The present invention describes... 34 The amount of S-labeled Na2SO4 added does not exceed 10% of the background value of sulfate content in the sediment sample to be tested, to avoid significantly altering the substrate level. The background value of sulfate content in the sediment sample to be tested is also the sulfate content at the test site. This invention selects to use... 34 S isotopes as SO4 2- Markers were used to measure sulfur in sediments before and after labeling. 2- of 34 The reduction rate of sulfate is calculated using the abundance difference of S, a method that poses no risk of radioactivity. 34 S is a stable isotope, requiring no special protection or waste disposal, making it suitable for use in the field and sensitive areas (such as protected areas and aquaculture areas). Laboratories do not need to construct radioactive operating areas, lowering the research threshold.

[0019] The culture described in this invention is a pressureless culture, which means that it can be cultured under natural conditions. This invention is based on the use of... 34 S spikes the sample, allowing for pressureless culture of the spiked sample. If using... 35 The S-law typically requires low-pressure sealing and radiation protection to maintain the original pore structure of sediments, reduce human impact on sediments, and improve the accuracy of natural condition simulation. This invention, after culturing the spiked sample for a certain period, when the SO4 content in the sediment... 2- When reduced, SO4 is marked 2- Unlabeled SO4 2- Converted proportionally to S 2- At this time, S generated in the sediment 2- middle34 The abundance of S will increase.

[0020] The marine sediments used for testing in this invention include one or more of the following: sediments from aquaculture areas, salt marsh wetlands, seagrass beds, estuaries, tidal flats, mangrove areas, or sandy areas. The incubation time described in this invention is based on the environmental type of the marine sediment testing site and should not be too long to avoid complete consumption of the added labeled sulfate, which would lead to lower measured values. Specifically, the incubation time is 0.5 to 3 days.

[0021] After obtaining the spiked cultured sample, this invention further includes freezing the spiked cultured sample. Specifically, the sediment sampling tube containing the spiked cultured sample, taken directly from the marine sediment testing site, is sealed and then frozen. The freezing process described in this invention is the same as described above and will not be repeated.

[0022] This invention requires obtaining sulfides from the control sample of the sediment to be tested. 34 S abundance and sulfide content in the spiked cultured sediment sample, sulfide concentration, and sulfide content. 34 S abundance and sulfate 34 S abundance. Specifically, in this invention, after thawing the control sample of the sediment to be tested, the control sample is mixed under anaerobic conditions, and then the sulfides in the control sample are obtained. 34 S abundance; After thawing the spiked cultured sample, mix the spiked cultured sample under anaerobic conditions, and then obtain the sulfide content and sulfide concentration in the spiked cultured sediment sample. 34 S abundance and sulfate 34 S abundance. More specifically, the bulk density and water content of sediments from a portion of the control sample and a portion of the spiked cultured sediment sample are measured, and then the sulfide content in the control sample is obtained. 34 S abundance and sulfide content in the spiked cultured sediment sample, sulfide concentration, and sulfide content. 34 S abundance and sulfate 34 S abundance.

[0023] The anaerobic mixing process in this invention is primarily to prevent the oxidation of sulfides in marine sediment samples. In this invention, the mixing of the control sediment sample and the spiked cultured sample can be performed by layering and cutting the sediment according to a custom layering method, or by mixing all the sediments together. The advantage of layering and cutting the sediment according to a custom layering method is that it allows for the simultaneous measurement of sulfate reduction rates at different depths within the marine sediment profile, thus improving measurement efficiency.

[0024] This invention obtains sulfides from the sediment control sample to be tested. 34 S abundance and sulfide content in the spiked cultured sediment sample, sulfide concentration, and sulfide content. 34 S abundance and sulfate 34 After determining the S abundance, the sulfides in the control sediment sample to be tested were used as a basis. 34 S abundance and sulfide content in the spiked cultured sediment sample, sulfide 34 S abundance and sulfate 34 The abundance of S yields the sulfate reduction rate of the sediment.

[0025] Specifically, this invention calculates the sulfate reduction rate of sediments at each layer / depth using the following formula 1, denoted by R, with units of nmol·cm⁻¹. -3 ·day -1 If the thickness of the sediment layer is specified, nmol·cm⁻¹ can also be used. -2 ·day -1 The unit is nmol·g; if the bulk density of the sediment has been determined, it can also be expressed as nmol·g. -1 ·day -1 Units.

[0026] Formula 1;

[0027] Formula 1 Explanation: C Sulfide, T0 —sulfides in pre-cultivation sediments 34 S abundance (%); C Sulfide, T1 —Sediments after cultivation 34 S abundance (in %); [S 2- ] T1 —Sulfide content of sediments after cultivation (unit: nmol·cm⁻¹) -3 ); C Sulfate, T1 —Sulfate in post-cultivation sediments 34 S abundance (%); ΔT—incubation time (ΔT, day).

[0028] This invention provides an in-situ method for determining the sulfate reduction rate of marine sediments. The in-situ method provided by this invention involves injecting a certain amount of [unspecified substance] into the sediment.34 S stable isotope labeled SO4 2- (in 34 S abundance was much higher than that of SO4 under natural conditions. 2- middle 34 The abundance of S was 4.2%, when SO4 2- When reduced, SO4 is marked 2- Unlabeled SO4 2- Converted proportionally to S 2- The S generated at this time 2- middle 34 The abundance of S will increase. Determination of labeled SO4 2- Before (control CK) and marked SO4 2- - After a period of time (ΔT), S in the sediment 2- of 34 By measuring the sulfate abundance difference and other relevant parameters, the sulfate reduction rate can be calculated. This invention enables in-situ measurement of sulfate reduction rates in marine sediments, yielding results that conform to objective laws and are highly accurate. The measurement process is simple, safe, and stable. Attached Figure Description

[0029] Figure 1 This is a flowchart of the in-situ determination method for sulfate reduction rate in sediments according to the present invention;

[0030] Figure 2 This is a schematic diagram of the sediment sampling tube described in this invention;

[0031] Figure 3 This is a schematic diagram of the syringe and its needle described in this invention;

[0032] Figure 4 A diagram illustrating the changes in sulfide abundance in sediments during the labeling process. Detailed Implementation

[0033] This invention discloses an in-situ method for determining the sulfate reduction rate of marine sediments. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0034] like Figure 1 As shown, Figure 1 This is a flowchart of the in-situ determination method for sulfate reduction rate in sediments according to the present invention, which is specifically carried out according to the following steps:

[0035] 1. Determine the measurement site.

[0036] 2. Place two sediment sampling tubes at close proximity at the same measurement site, keeping them as close as possible (no more than 1 meter, to ensure consistent physicochemical properties within the same layer). One tube serves as a control tube, and the other as the measurement tube. Figure 2 As shown, Figure 2 This is a schematic diagram of the sediment sampling tube described in this invention.

[0037] 3. Seal the top of the control tube with a flexible rubber cap, dig it out (or pull it out), ensuring the soil column inside the tube remains intact. Seal the other end as well, and freeze it in a -20℃ freezer for later use. (Note: Sealing prevents oxygen from entering the sulfide oxide; freezing reduces the activity of internal microorganisms and stops the biochemical reactions inside the tube).

[0038] 4. Insert several injection needles into the sediment in the test tube. Be careful during the operation to avoid disturbing the sediment.

[0039] 5. Add a certain mass of labeled sodium sulfate (Na2SO4, 34 Sodium sulfate (S) with an abundance higher than 4.2% was dissolved in deionized water to obtain a labeled sodium sulfate solution of a certain concentration. 34 SO4 2- The addition amount is typically ≤10% of the ambient sulfate concentration to avoid significantly altering substrate levels. The solution is thoroughly purged with nitrogen to remove dissolved oxygen.

[0040] 6. Take a certain volume of labeled sodium sulfate solution and inject it into the sediment using a syringe and a needle already inserted into the sediment. After injection, remove the syringe and plug the needle hole with a needle plug, but do not remove the sediment. This is to prevent oxygen from entering the sediment through the needle hole. Figure 3 As shown, Figure 3 This is a schematic diagram of the syringe and its needle described in this invention.

[0041] 7. After incubation for a certain period of time (ΔT, in days), seal with an elastic rubber cap, dig out (or pull out), ensuring the soil column inside the tube is intact, seal the other end as well, and freeze in a -20℃ freezer for later use.

[0042] 8. Take the control tube and test tube back to the laboratory and let them thaw at room temperature.

[0043] 9. Remove the rubber cap and pull out the injection needle from the measuring tube; use the piston to slowly push out the internal sediment, and cut it into sections according to the set layers (depths), and take a portion of the sediment to measure the bulk density and water content.

[0044] 10. Thoroughly mix each section of sediment to be tested.

[0045] Note: Steps 9 and 10 are performed in a nitrogen anaerobic environment to prevent oxidation of sulfides in the sediment.

[0046] 11. Take a certain amount of the mixed sediment and perform the following measurements:

[0047] 1) Determination of sulfides in sediments from control tubes 34 The abundance of S is expressed by C. Sulfide, T0 (Unit: %) indicates;

[0048] 2) Determination of sulfide content in sediments within the test tube; sulfide content... 34 The abundance of S and in sulfate 34 S abundance, respectively, is represented by [S] 2- ] T1 (Unit: nmol·cm) -3 C Sulfide, T1 (unit %) and C Sulfate, T1 (Unit: %) indicates.

[0049] The relevant measurement methods for 1) and 2) above are as follows:

[0050] The determination of sulfide content in sediments was carried out in accordance with the methods specified in "Marine Monitoring Standard Part 5: Sediment Analysis" (GB 17378-2007).

[0051] Sediment sulfides 34 The abundance of sulfur (S) was determined using the "acid hydrolysis distillation-precipitation purification method": A certain amount (5 g) of sediment was placed in a semi-micro Kjeldahl still, excess dilute hydrochloric acid was added, and steam was passed through to convert all the sulfides into hydrogen sulfide, which was then distilled out with the steam. The hydrogen sulfide was absorbed at the end by excess zinc acetate solution, forming a white zinc sulfide precipitate. The precipitate was filtered (using a 0.45 μm cellulose acetate microporous membrane), dried, and then the abundance of zinc sulfide was determined using a stable isotope abundance mass spectrometer. 34 The abundance of S is the amount of sulfides in the sediment. 34 abundance of S.

[0052] sulfate in sediments 34 S abundance was determined using a "barium sulfate precipitation-high temperature pyrolysis-isotope mass spectrometry" method: A certain amount (5 g) of sediment was placed in an Erlenmeyer flask, and deionized water was added at a water-to-soil ratio (mass) of 10:1. The sediment was shaken for 1.5 h to extract sulfate ions. After filtration through a 0.45 μm cellulose acetate microporous membrane, excess barium chloride solution was added to convert soluble sulfate ions into barium sulfate precipitate. The precipitate was then filtered again through a 0.45 μm cellulose acetate microporous membrane. After drying the filter cake, barium sulfate was determined using a stable isotope abundance mass spectrometer. 34 The abundance of sulfur (S) is the amount of sulfate in the sediment. 34 abundance of S.

[0053] 12. Calculate the sulfate reduction rate of sediment at each layer / depth using Formula 1 below, expressed as R (unit: nmol·cm³). -3 ·day -1 )express:

[0054] Formula 1;

[0055] Formula 1 Explanation: C Sulfide, T0 —sulfides in pre-cultivation sediments 34 S abundance; C Sulfide, T1 —sulfides in post-cultivation sediments 34 S abundance; [S 2- ] T1 —Sulfide content in post-cultivation sediments; C Sulfate, T1 —Sulfate in post-cultivation sediments 34 S abundance; ΔT—culture time.

[0056] The derivation of Formula 1 above is as follows:

[0057] (1) Explanation of abbreviations

[0058] A soil column of a certain volume (V, unit cm) 3 Na2 for internal use 14 SO4 is used to label sediments, with a start time of T0 and an end time of T1, and the time interval is ΔT (T1 minus T0, in days). Figure 4 As shown, Figure 4 A diagram illustrating the changes in sulfide abundance in sediments during the labeling process.

[0059] ① Before marking, sediment sulfides 34 S 2- Abundance C Sulfide,T0 equal[ 34 S 2- ] T0 / [S 2- ] T0 Sediment sulfate 34 SO4 2- Abundance C Sulfate,Before injection equal[ 34 SO4 2- ] Before injection SO4 2- ] Before injection .

[0060] ② Add marker Na2 34 SO4, in markers 34 SO4 2- Sulfate abundance C Sulfate,Marked equal[ 34 SO42- ] Marked SO4 2- ] Marked .

[0061] ③ After instantaneous marking, sediment sulfides 34 S 2- Abundance unchanged, C Sulfide,T0 Still [ 34 S 2- ] T0 / [S 2- ] T0 Sediment sulfate 34 SO4 2- Abundance C Sulfate,After injection equal[ 34 SO4 2- ] After injection SO4 2- ] After injection .

[0062] ④ After in-situ cultivation for a certain period of time, sediment sulfides 34 S 2- Abundance C Sulfide,T1 equal[ 34 S 2- ] T1 / [S 2- ] T1 Sediment sulfate 34 SO4 2- Abundance C Sulfate,T1 equal[ 34 SO4 2- ] T1 SO4 2- ] T1 .

[0063] The above [S] 2- ]、[ 34 S 2- SO4 2- ]、[ 34 SO4 2- The unit is nmol·cm. -3 .

[0064] The rate of sulfate reduction is denoted as R, and the unit is nmol·cm. -3 ·day -1 , 34 S abundance C is expressed as a percentage.

[0065] (2) Derivation process

[0066] according to 34 S 2- Atom conservation, i.e., the reduction of atoms in the sediment before and after cultivation.34 S 2- The difference in value equals the sulfate reduction rate multiplied by the amount of sulfate in the sediment after instantaneous labeling. 34 SO4 2- Abundance, yielding the following equation 1:

[0067] Equation 1;

[0068] The sulfate reduction rate R can be calculated from the above equation, as shown in Equation 2 below:

[0069] Equation 2;

[0070] according to Figure 4 The intermediate expression description yields:

[0071] ① Before marking (T0), sediment sulfides 34 S 2- content([ 34 S 2- ] T0 ) equals sediment S 2- Content ([S) 2- ] T0 Multiply by 34 S 2- Abundance (C) Sulfide,T0 Equation 3 is as follows:

[0072] Equation 3;

[0073] ② After in-situ cultivation for a certain period of time (T1), sediment sulfides 34 S 2- content([ 34 S 2- ] T1 ) equals sediment S 2- Content ([S) 2- ] T1 Multiply by 34 S 2- Abundance (C) Sulfide,T1 Equation 4 is as follows:

[0074] Equation 4;

[0075] ③ Due to 34 SO4 2- and SO4 2- Reduced proportionally to sulfides, and then instantly labeled with sulfates in the sediment. 34 SO4 2- Abundance C Sulfate,After injection and sulfate in post-cultivation sediment 34 SO4 2- Abundance CSulfate,T1 They are equal, as shown in Equation 5 below:

[0076] Equation 5;

[0077] By combining and converting equations 2 through 5 above, we can obtain the following equation 6:

[0078] Equation 6;

[0079] In addition, before cultivation ([S 2- ] T0 ) and after cultivation ([S 2- ] T1 Sediment S 2- The change in sulfate content is equal to the sulfate reduction rate (R) multiplied by the time interval (ΔT), as shown in Equation 7 below:

[0080] Equation 7;

[0081] Equation 7 is transformed to obtain the following equation 8:

[0082] Equation 8;

[0083] Substituting equation 8 into equation 6 and simplifying, we obtain the aforementioned formula 1:

[0084] Formula 1.

[0085] Therefore, according to the final formula, the parameters that need to be measured to calculate the sulfate reduction rate R in sediments are:

[0086] ① Sulfides in sediments before cultivation 34 S abundance C Sulfide, T0 ;

[0087] ② Sulfide content of sediments after cultivation [S] 2- ] T1 and 34 S abundance C Sulfide, T1 ;

[0088] ③ Sulfate in the sediment after cultivation 34 S abundance C Sulfate, T1 .

[0089] ④ At the same time, the training period needs to be clearly defined.

[0090] The present invention will be further described below with reference to the embodiments:

[0091] Example 1

[0092] Determination of sulfate reduction rate in the top 5 cm sediment of aquaculture areas:

[0093] (1) Sediment sampling tube parameters: inner diameter 4 cm, length 7 cm, reserved depth 1 cm both above and below, sampling depth 5 cm above the surface, sampling volume 62.8 cm³. 3 .

[0094] (2) 34 S-labeled sulfate solution: 34 S abundance 23.8%, sulfate content 1 mol / L (96 mg / cm³) 3 The total injection volume is 1 cm. 3 (Cross-shaped marking, 4 needles per sediment tube, 0.25 cm injection volume per needle) 3 ).

[0095] (3) Culture time (ΔT) 1 day.

[0096] (4) Sampling stratification: Fully mixed, without stratification.

[0097] (5) Sulfate in the sediment after cultivation 34 S abundance (C Sulfate, T1 The figure was 15.1%.

[0098] (6) Sulfides in sediment before culture (control tube) 34 S abundance (C Sulfide, T0 The figure is 4.03%.

[0099] (7) Sulfide content after cultivation (test tube) ([S 2- ] T1 The concentration was 6487.47 nmol / cm³. 3 .

[0100] (8) Sulfides in the sediment after incubation (test tube) 34 S abundance (C Sulfide, T1 The percentage is 4.25%.

[0101] (9) The sulfate reduction rate (R) was calculated to be 128.93 nmol / (cm). 3 ·day).

[0102] Example 2

[0103] The study investigated the sulfate reduction rate in the top 10 cm of sediments from the upper, middle, and lower reaches of mangrove forests along the river.

[0104] (1) Sediment sampling tube parameters: inner diameter 5 cm, length 12 cm, reserved depth 1 cm both above and below, total sampling depth 10 cm, sampling volume per tube 196.25 cm³. 3 .

[0105] (2) 34S-labeled sulfate solution: 34 S abundance 20%, sulfate content 0.5 mol / L (48 mg / cm³) 3 The total sediment injection volume per tube was 1.5 cm. 3 (Each tube of sediment is evenly marked with 5 needles, and each needle injects 0.3 cm of sediment.) 3 A total of 72 mg of sulfate and 14.4 mg of labeled sulfate were injected.

[0106] (3) Culture time (ΔT) 2 days.

[0107] (4) Sampling stratification: Fully mixed, without stratification.

[0108] (5) The calculated data of sulfate reduction rate in sediments are shown in Table 1 below:

[0109] Table 1

[0110]

[0111] Example 3

[0112] Trends in sulfate reduction rate in the 100 cm soil layer of salt marsh wetlands:

[0113] (1) Sediment sampling tube parameters: inner diameter 20 cm, length 110 cm, reserved depth of 5 cm at both the top and bottom, total sampling depth of 100 cm, marked at 10 cm depth per layer, for a total of 10 layers, with a sampling volume of 3140 cm³ per layer. 3 .

[0114] (2) The physicochemical parameters of different layers of 100 cm sediment are shown in Table 2 below:

[0115] Table 2

[0116]

[0117] (3) 34 S-labeled sulfate solution: 34 S abundance 50%, sulfate content 0.1 mol / L (9.6 mg / cm³) 3 The injection volume of each sediment layer is 10 cm. 3 (A total of 10 pins were used to mark 100 cm of sediment in the entire tube, totaling 100 cm) 3 ), 96 mg of sulfate was injected into each layer (a total of 960 mg was injected into the 100 cm sediment tube), and 48 mg of labeled sulfate was injected into each layer (a total of 480 mg was injected into the 100 cm sediment tube).

[0118] (4) Culture time (ΔT) 2 days.

[0119] (5) Sampling stratification: each 10 cm layer is a layer, for a total of 10 layers.

[0120] (6) The calculated data of sulfate reduction rate in sediments are shown in Table 3 below:

[0121] Table 3

[0122]

[0123] Example 4

[0124] A seagrass bed (14.59 hm²) 2 Total sulfate reduction in sediments at a depth of 100 cm per month (based on 30 days):

[0125] Seven measurement sites were set up in an S-shape within the seagrass bed. The sulfate reduction rate at each layer was measured at each measurement site according to the method in "Example 3". The sum of the sulfate reduction rates at each layer represents the total sulfate reduction rate at a depth of 100 cm at that site. The mean value of each measurement site represents the sediment reduction rate at a depth of 100 cm in the seagrass bed. Multiplying by the area and time, the total value can be obtained after unit conversion.

[0126] The sulfate reduction rate data at different sites and levels are shown in Table 4 below:

[0127] Table 4

[0128]

[0129] The sulfate reduction rate of seagrass bed sediments at a depth of 100 cm is 144.04 nmol / (cm³). 3 ·day)=144.04mmol / (m 3 ·day);

[0130] Seagrass bed area: 14.59 hm² 2 =145900m 2 ;

[0131] The total volume of sediment at a depth of 100 cm (i.e., 1 m) is 145,900 m³. 3 The total reduction rate was 21015.436 mol / day;

[0132] The total amount of sulfate reduced over 30 days is: 63.05 × 10⁻⁶ 4 mol.

[0133] Example 5

[0134] Determination of sulfate reduction rate per unit mass (g) of sediments in estuary area (50 cm depth):

[0135] (1) Sediment sampling tube parameters: inner diameter 12 cm, length 60 cm, reserved depth of 5 cm both above and below, total sampling depth 50 cm, marked at 5 cm depths per layer, for a total of 10 layers, with a sampling volume of 565.2 cm³ per layer. 3 .

[0136] (2) 34 S-labeled sulfate solution: 34 S abundance 70%, sulfate content 0.25 mol / L (24 mg / cm³) 3 5 cm of sediment was injected into each layer. 3 (A total of 10 pins were used to mark 50 cm of sediment in the entire tube, totaling 50 cm) 3 Each layer was injected with 120 mg of sulfate and 84 mg of labeled sulfate.

[0137] (3) The properties of different layers of 50 cm sediment are shown in Table 5 below:

[0138] Table 5

[0139]

[0140] (4) Culture time (ΔT) 1 day.

[0141] (5) Sampling stratification: each 5 cm layer is a layer, for a total of 10 layers.

[0142] (6) The calculated data of sulfate reduction rate in sediments are shown in Table 6 below:

[0143] Table 6

[0144]

[0145] The following comparative examples 1-2 and example 6 respectively measured the sulfate reduction rate of the top 5 cm sediment of mangroves in the same area to verify that the present invention is superior to the sulfide formation method for determining the sulfate reduction rate. 35 The level of S-radioisotope method:

[0146] Comparative Example 1

[0147] Sulfide formation method:

[0148] (a) Measurement Procedure

[0149] 1. Determine the measurement site.

[0150] 2. Place two sediment sampling tubes at similar locations at the same measurement site, one as a control tube and the other as a measurement tube.

[0151] 3. First, cover the top of the control tube with an elastic rubber cap, then remove it. Cover the other end with a cap as well, and freeze it in a -20℃ freezer for later use.

[0152] 4. After culturing the test tubes for a certain period of time (ΔT, in days), remove them, seal them tightly, and freeze them for later use, following the method in step 3.

[0153] 5. Place both the control tube and the test tube at room temperature to allow the sediment to melt.

[0154] 6. Under a nitrogen atmosphere, remove the sediment and mix it thoroughly.

[0155] 7. Take a certain amount of mixed sediment and determine the sulfide content of the control tube and the test tube respectively according to the method of "Marine Monitoring Specification Part 5: Sediment Analysis" (GB 17378-2007).

[0156] 8. Calculate the sulfate reduction rate of the sediment based on the difference in sulfide content between the control tube and the test tube, in nmol / (cm³). 3 ·day).

[0157] (II) Data Measurement

[0158] 1. Sediment sampling tube parameters: inner diameter 5 cm, length 7 cm, pre-drilled depth 1 cm both top and bottom, total sampling depth 5 cm, sampling volume per tube 98.2 cm³. 3 .

[0159] 2. Incubation time (ΔT): 1 day.

[0160] 3. Sampling stratification: Fully mixed, no stratification.

[0161] 4. The measured values ​​of sulfide content and the calculated values ​​of sulfate reduction rate are shown in Table 7 below:

[0162] Table 7

[0163]

[0164] Comparative Example 2

[0165] Sulfur radioisotope method:

[0166] The method described in the literature “Study on sulfate reduction rate of waste Yellow River estuary salt marsh soil” (Sun Bingyin and Jing Meide, 1990) was used for determination.

[0167] 1. Determine the measurement site and insert one sediment sampling tube.

[0168] 2. Insert several injection needles into the sediment in the test tube. Be careful during the operation to avoid disturbing the sediment.

[0169] 3. Inject a certain volume and concentration of radioactive material through an injection needle. 35 S is injected with Na2SO4 solution. After injection, the syringe is removed, and the needle hole is plugged with a needle plug, but the deposit is not removed. The purpose is to prevent oxygen from entering the deposit through the needle hole.

[0170] 4. After cultivating for a certain period of time (ΔT, in days), cover it tightly with an elastic rubber cap, dig it out (or pull it out), ensuring that the soil column inside the tube is intact. Cover the other end tightly as well, and place it in a freezer at -20℃ for later use.

[0171] 5. Place the sampling tube at room temperature to thaw.

[0172] 6. Remove the rubber cap, pull out the injection needle from the tube, and remove the deposit under a nitrogen atmosphere, then mix thoroughly.

[0173] 7. Determination of radioactivity of sediment sulfides: A certain amount (5 g) of sediment was placed in a semi-micro Kjeldahl distillation apparatus. Excess dilute hydrochloric acid was added, and steam was passed through to convert all the sulfides into hydrogen sulfide, which was then distilled out with the steam. At the end, excess sodium hydroxide solution was used to absorb the hydrogen sulfide and generate dissolved sodium sulfide. A certain volume of sodium sulfide solution was transferred to a scintillation bottle, and its radioactivity (unit: Bq / mL) was determined using a liquid scintillation counter. The unit was then converted to per cm³. 3 Radioactivity of sediment sulfides (Bq / cm) 3 ).

[0174] 8. Determination of sulfate radioactivity and sulfate ion content in sediments: A certain amount (5 g) of sediment was placed in an Erlenmeyer flask, and dilute hydrochloric acid (0.1 mol / L) was added at a liquid-to-soil ratio (mass) of 10:1. The mixture was shaken for 1.5 h to extract sulfate ions from the sediments, during which nitrogen gas was continuously introduced to remove dissolved sulfides. The solution was filtered through a 0.45 μm cellulose acetate microporous membrane. A certain volume of sulfate extract was transferred to a scintillation bottle, and its radioactivity (unit: Bq / mL) was determined using a liquid scintillation counter. The unit was then converted to per cm³. 3 Radioactivity of sulfate ions in sediments (Bq / cm) 3 A separate volume of sulfate extract was taken, and its sulfate ion content was determined by ion chromatography, and converted to a concentration per cubic centimeter. 3 Sulfate ion content in sediments (nmol / cm) 3 ).

[0175] 9. Calculation: Since sulfate and radioactive sulfate in the sediment are converted into sulfides in equal proportions, therefore:

[0176] Sulfide formation amount / sulfate content in sediment = sulfide radioactivity / sulfate radioactivity;

[0177] Based on this, the amount of sulfide generated and the rate of sulfate reduction can be calculated.

[0178] (II) Data Measurement

[0179] 1. Sediment sampling tube parameters: inner diameter 5 cm, length 7 cm, pre-drilled depth 1 cm both top and bottom, total sampling depth 5 cm, sampling volume per tube 98.2 cm³. 3 .

[0180] 2. 35 S-labeled sulfate solution: 35 S radioactivity 10000 Bq / mL, total sediment injection volume 1 cm per tube 3 (Each tube of sediment is evenly marked with 4 needles, and each needle injects 0.25 cm of sediment.) 3 ).

[0181] 3. Incubation time (ΔT): 1 day.

[0182] 4. Sampling stratification: Fully mixed, no stratification.

[0183] 5. The calculated data for the sulfate reduction rate in sediments are shown in Table 8 below:

[0184] Table 8

[0185]

[0186] Example 6

[0187] Sulfur stability isotope method (method of this invention)

[0188] (a) Measurement Procedure

[0189] As described above, there will be no further explanation.

[0190] (II) Data Measurement

[0191] 1. Sediment sampling tube parameters: inner diameter 5 cm, length 7 cm, pre-drilled depth 1 cm both top and bottom, total sampling depth 5 cm, sampling volume per tube 98.2 cm³. 3 .

[0192] 2. 34 S-labeled sulfate solution: 34 S abundance 50%, sulfate content 0.5 mol / L, i.e. 48 mg / cm³ 3 The total sediment injection volume per tube is 1 cm. 3(Each tube of sediment is evenly marked with 4 needles, and each needle injects 0.25 cm of sediment.) 3 A total of 48 mg of sulfate and 24 mg of labeled sulfate were injected.

[0193] 3. Incubation time (ΔT): 1 day.

[0194] 4. Sampling stratification: Fully mixed, no stratification.

[0195] 5. The calculated data for the sulfate reduction rate in sediments are shown in Table 9 below:

[0196] Table 9

[0197]

[0198] Comparative analysis of accuracy and precision:

[0199] Table 10 lists the sulfate reduction rates, mean values, and standard deviations obtained by the three methods in Comparative Examples 1-2 and Example 6, and compares their differences.

[0200] Table 10

[0201]

[0202] Note: a and b represent comparisons of differences.

[0203] Table 10 shows that the standard deviation of sulfate reduction rate determined by the sulfide formation method is large between repeats, and the mean is lower than that of the isotope method. (Radioactive isotopes) 35 S and stable isotopes 34 The values ​​measured by the two methods are similar, both being 86.88 nmol / (cm). 3 day) and 84.62 nmol / (cm 3 The two methods showed no significant difference (day). Therefore, this demonstrates the reliability of the method of the present invention (stable isotope method).

[0204] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for in-situ determination of sulfate reduction rate in marine sediments, characterized in that, Includes the following steps: S1) Take samples of marine sediments at the sites to be tested to obtain control samples of the sediments to be tested and spiked and cultured samples of the sediments to be tested; The spiked and cultured sediment sample to be tested was obtained through the following steps: Will 34 S-labeled Na2SO4 was added to the marine sediments at the target sites, and then cultured to obtain spiked sediment samples for analysis. 34 S-labeled Na2SO4 34 S abundance is higher than 4.2%, the 34 The amount of S-labeled Na2SO4 added shall not exceed 10 wt% of the background value of sulfate content in the sediment sample to be tested; S2) Obtain sulfides from the sediment control sample to be tested described in step S1). 34 S abundance and sulfide content in the sediment samples after spiked culture, sulfide concentration 34 S abundance and sulfate 34 S abundance; S3) Based on the sulfides in the sediment control sample to be tested 34 S abundance and sulfide content in the spiked cultured sediment sample, sulfide 34 S abundance and sulfate 34 S abundance yields the sulfate reduction rate of the sediment.

2. The in-situ measurement method according to claim 1, characterized in that, In step S1), the 34 S-labeled Na2SO4 34 S abundance is above 90%.

3. The in-situ measurement method according to claim 1, characterized in that, In step S1), the culture is a pressureless culture.

4. The in-situ measurement method according to claim 1, characterized in that, In step S1), a special injection needle is used to inject... 34 S-labeled Na2SO4 is added to the marine sediment at the site to be tested, and the specially designed injection needle remains in the marine sediment at the site to be tested and is sealed.

5. The in-situ measurement method according to claim 4, characterized in that, The specially designed injection needle has multiple holes in its tube wall.

6. The in-situ measurement method according to claim 1, characterized in that, In step S1), the sampling interval between the control sample of the sediment to be tested and the spiked and cultured sample of the sediment to be tested shall not exceed 1 meter.

7. The in-situ measurement method according to claim 1, characterized in that, In step S1), after obtaining the control sample of the sediment to be tested, the method further includes freezing the control sample of the sediment to be tested. After obtaining the spiked cultured sediment sample to be tested, the method further includes freezing the spiked cultured sediment sample to be tested.

8. The in-situ measurement method according to claim 7, characterized in that, In step S2), after thawing the sediment control sample to be tested, the sediment control sample to be tested is mixed under anaerobic conditions, and then the sulfides in the sediment control sample to be tested are obtained. 34 S abundance; After thawing the spiked sediment sample, the sample was mixed thoroughly under anaerobic conditions. Then, the sulfide content and sulfide concentration in the spiked sediment sample were obtained. 34 S abundance and sulfate 34 S abundance.

9. The in-situ measurement method according to claim 1, characterized in that, In step S1), the marine sediments at the marine sediment detection site include one or more of the following: sediments from aquaculture areas, salt marsh wetlands, seagrass beds, estuaries, tidal flats, mangrove areas, or sandy areas.

10. The in-situ measurement method according to claim 9, characterized in that, The culture time is 0.5 to 3 days.

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