Method for dividing sediment-water interface in aquatic ecosystem

Abstract

The present application relates to a kind of sediment-water interface division methods in aquatic ecosystem, comprising the following steps: step 1, utilizes gravity type sediment sampler to collect sediment columnar core sample in preset sampling point;Step 2, the sediment columnar core sample collected is placed in thermostatic water tank, and is carried out simulation culture under the condition similar to sampling point temperature;Step 3, the vertical distribution characteristics of target object concentration in sediment columnar core sample are obtained using flat plate type DGT device;Step 4, the target object concentration on adsorption film corresponds with the one-dimensional profile of sediment columnar core sample, and the one-dimensional profile concentration distribution of target object in environmental medium or micro-interface is obtained;Step 5, the concentration of target object is divided interval according to gradient limit value and is marked with different color, and completion is divided.This application can accurately divide the sediment-water interface in aquatic ecosystem, and provide scientific basis for the in-depth study of the migration and conversion rule and environmental behavior of various pollutants in sediment-water interface.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, specifically to a method for defining the sediment-water interface in an aquatic ecosystem. Background Technology

[0002] The sediment-water interface (SWI) in aquatic ecosystems is a habitat for benthic organisms and a crucial component of the aquatic ecosystem. It also represents the most significant environmental boundary in terms of physical, chemical, and biological characteristics of natural water bodies. This interface is a "hotspot" for material participation in environmental geochemical cycles and biological coupling. With the involvement of microorganisms, a series of physicochemical and biological reactions occur near the sediment-water interface (such as migration, transformation, adsorption / desorption, diffusion, burial, and bioturbation), serving as a vital pathway for regulating and controlling the exchange and transport of matter between sediments and water.

[0003] Macroscopically, the sediment-water interface refers to the "interface" or transition zone formed by the physical contact between two solid-liquid media, the sedimentary phase and the overlying water phase. However, in reality, there is no contacting "surface" between the sedimentary and water phases. The sediment-water interface is usually defined as a layer with a certain thickness and complex structure. From a microscopic perspective, the sediment-water interface is the mutual permeation and inclusion of the two media in a certain space, causing the "interface" to be stretched vertically, giving it a three-dimensional scale. However, the academic community currently lacks an accurate and reliable method for determining the three-dimensional scale of this interface. This results in a lack of scientific basis when constructing related models of the sediment-water interface and when studying the physical, chemical, and biological reactions of various substances in the interface region within aquatic ecosystems.

[0004] Therefore, accurately defining the sediment-water interface is of great significance for in-depth research on the migration and transformation patterns and environmental behavior of various pollutants at the sediment-water interface. Summary of the Invention

[0005] To address the above technical problems, the main objective of this invention is to provide a method for defining the sediment-water interface in aquatic ecosystems. This method can accurately define the sediment-water interface in aquatic ecosystems, which is of great significance for in-depth research on the migration and transformation patterns and environmental behavior of various pollutants at the sediment-water interface. It provides a scientific basis for in-depth research on the migration and transformation patterns and environmental behavior of various pollutants at the sediment-water interface.

[0006] To achieve the above objectives, the present invention employs the following technical solutions.

[0007] A method for delineating the sediment-water interface in an aquatic ecosystem includes the following steps:

[0008] Step 1: Collect sediment core samples at preset sampling points using a gravity sediment sampler;

[0009] Step 2: Place the collected sediment core samples in a constant temperature water tank and conduct simulated culture under conditions similar to the temperature at the sampling point;

[0010] Step 3: Use a flat-plate DGT device to obtain the vertical distribution characteristics of the target concentration in the sediment core sample. The flat-plate DGT device includes a DGT probe and an adsorption membrane. The DGT probe is used to fix the adsorption membrane, and the adsorption membrane is used to adsorb and fix the target.

[0011] Step 4: Correspond the concentration of the target substance on the adsorption membrane with the one-dimensional profile of the interface between the sediment phase and the water phase in the sediment column core sample to obtain the one-dimensional profile concentration distribution of the target substance in the environmental medium or micro-interface.

[0012] Step 5: Divide the concentration of the target analyte into intervals according to gradient limits and mark them with different colors to complete the division of the sediment-water interface.

[0013] Preferably, step 3 includes the following sub-steps:

[0014] Sub-step 3.1: Insert the DGT probe vertically into the interface between the sediment phase and the aqueous phase, and protrude it upwards by 3-5 cm. After standing for 24-48 hours, retrieve the DGT probe and remove the adsorption membrane.

[0015] Sub-step 3.2 involves horizontally cutting the adsorption membrane into multiple small pieces arranged vertically.

[0016] Sub-step 3.3: Elute each small adsorption membrane to obtain the eluent, and determine the cumulative amount M of the target analyte in the eluent;

[0017] Sub-step 3.4: Calculate the concentration or flux measured by DGT using formula (1) to obtain the concentration C of the target analyte measured by DGT. DGT (mg / L);

[0018]

[0019] In the formula:

[0020] C DGT (mg / L) represents the concentration of the target substance determined by DGT;

[0021] M is the cumulative amount (mg) of the target analyte in DGT;

[0022] Δg is the total thickness (cm) of the diffusion membrane and the filter membrane;

[0023] D is the diffusion coefficient of the target substance in the diffusion film (cm).2 ·s -1 );

[0024] A is the window area of ​​the DGT device (cm²) 2 );

[0025] T is the placement time (s).

[0026] Preferably, the target substances are soluble phosphate SRP and ammonia nitrogen NH4. + -N.

[0027] Preferably, the method for dividing the target concentration gradient limit interval in step 5 is as follows: when soluble phosphate SRP and ammonia nitrogen NH4 + -N meets one of the following three conditions,

[0028] Condition 1: Soluble phosphate SRP ≤ 0.01 and ammonia nitrogen NH4 + -N≤0.1;

[0029] Condition 2: 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 + -N < 30;

[0030] Condition 3: Soluble phosphate SRP ≥ 5.2 and ammonia nitrogen NH4+ + -N≥30;

[0031] The target analyte concentration gradient limit intervals are divided as follows:

[0032] When condition 1 is met, it is an overlying aqueous phase, marked in blue;

[0033] When condition 2 is met, it is a sediment-water interface region, marked in yellow;

[0034] When condition 3 is met, it is a sedimentary phase and is marked in brown.

[0035] Preferably, another method for dividing the target concentration gradient limit interval in step 5 is as follows: when soluble phosphate SRP and ammonia nitrogen NH4 + -N does not meet one of the following three conditions,

[0036] Condition 1: Soluble phosphate SRP ≤ 0.01 and ammonia nitrogen NH4 + -N≤0.1;

[0037] Condition 2: 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 + -N<30;

[0038] Condition 3: Soluble phosphate SRP ≥ 5.2 and ammonia nitrogen NH4+ + -N≥30;

[0039] The target analyte concentration gradient limit intervals are divided as follows:

[0040] When the soluble phosphate SRP is ≤0.01, it is the overlying aqueous phase and is marked in blue;

[0041] When 0.01 < soluble phosphate SRP < 5.2, it is the sediment-water interface region, marked in yellow;

[0042] When the soluble phosphate SRP is ≥ 5.2, it is a sedimentary phase and is marked in brown.

[0043] Preferably, the gravity sediment sampler has dimensions of L50cm × Φ8.4cm.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] This invention can accurately delineate the sediment-water interface in aquatic ecosystems, providing a scientific basis for in-depth research on the migration and transformation patterns and environmental behavior of various pollutants at the sediment-water interface. Attached Figure Description

[0046] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0047] Figure 1 This is a flowchart of the partitioning method of the present invention;

[0048] Figure 2 A schematic diagram of the vertical structure of the sediment-water interface in an aquatic ecosystem;

[0049] Figure 3 This is a schematic diagram of a flat-panel DGT device.

[0050] Figure 4 A schematic diagram showing the results of sediment-water interface delineation in an aquatic ecosystem;

[0051] Figure label:

[0052] A-DGT device base plate, B-DGT device cover plate, C-Combined device, D--DGT device bottom cross-sectional structure. Detailed Implementation

[0053] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0054] refer to Figure 1 The flowchart of the delineation method of the present invention. A method for delineating the sediment-water interface in an aquatic ecosystem includes the following steps:

[0055] Step 1: Collect sediment core samples at preset sampling points using a gravity sediment sampler;

[0056] Two sediment core samples were collected at the sampling point using a gravity sediment sampler with dimensions of L50cm × Φ8.4cm, at a sampling depth of 30–35cm. One of the two core samples was kept as a backup. The collected core sample was wrapped in a black plastic bag to avoid light exposure. During sampling and transportation, the suspended layer at the top of the sediment core was kept undisturbed, and in-situ overlying water was included to maintain the integrity of the sediment-water interface.

[0057] Step 2: Place the collected sediment core samples in a constant temperature water tank and conduct simulated culture under conditions similar to the temperature at the sampling point;

[0058] The collected sediment column samples were placed in a glass water tank with a constant temperature water bath to allow the column samples to undergo static release simulation culture under the same temperature conditions as the in-situ water environment. The culture time needs to reach 72 hours to ensure that the column sample sediment and the overlying water interface reach a dynamic equilibrium.

[0059] Step 3: Use a flat-plate DGT device to obtain the vertical distribution characteristics of the target concentration in the sediment core sample. The flat-plate DGT device includes a DGT probe and an adsorption membrane. The DGT probe is used to fix the adsorption membrane, and the adsorption membrane is used to adsorb and fix the target.

[0060] For environmental media with high spatial heterogeneity, such as sediments and wetland soils, flat-panel DGT devices are required to obtain vertical or two-dimensional profile information of the target. This device can be inserted into sediments for sampling or deployed in situ in the field by divers or using a DGT delivery system.

[0061] The vertical distribution characteristics of target analyte concentrations in sediment core samples were obtained using a flat-plate DGT device, including the following sub-steps:

[0062] Sub-step 3.1: Insert the DGT probe vertically into the interface between the sediment phase and the aqueous phase, and protrude it upwards by 3-5 cm. After standing for 24-48 hours, retrieve the DGT probe and remove the adsorption membrane.

[0063] refer to Figure 2 This is a schematic diagram of the vertical structure of the sediment-water interface. Specifically, the DGT probe was placed at the clearly visible interface between the sediment and water phases. Using this interface as a reference, the probe was inserted vertically through the interface, leaving a 4cm section exposed above the interface. The DGT probe exposure window was 15cm deep and 1.8cm wide. The DGT probe was left at the sediment-water interface for 35 hours. After placement, the DGT probe was retrieved, and the adsorption membrane was removed. Figure 3This is a schematic diagram of a flat-panel DGT device.

[0064] Sub-step 3.2 involves horizontally cutting the adsorption membrane into multiple small pieces arranged vertically.

[0065] After sequentially cutting the adsorption membrane along the longitudinal direction in one dimension, small sheet-like adsorption membranes are obtained, with a longitudinal precision of 1–5 mm. In this embodiment, the longitudinal precision is 5 mm.

[0066] Sub-step 3.3: Elute each small adsorption membrane to obtain the eluent, and determine the cumulative amount M of the target analyte in the eluent;

[0067] The target compounds are soluble phosphate SRP and ammonia nitrogen NH4. + -N, respectively, determined the ammonia nitrogen (NH4) in the eluent. + The cumulative amounts of -N and soluble phosphate SRP were determined. Ammonia nitrogen was determined using Nessler's reagent spectrophotometry (GB 7479-87), and soluble phosphate was determined using ammonium molybdate spectrophotometry (GB 11893-89).

[0068] Sub-step 3.4: Calculate the concentration or flux measured by DGT using formula (1) to obtain the concentration C of the target analyte measured by DGT. DGT (mg / L).

[0069]

[0070] In the formula:

[0071] C DGT (mg / L) represents the concentration of the target substance determined by DGT;

[0072] M is the cumulative amount (mg) of the target analyte in DGT;

[0073] Δg is the total thickness (cm) of the diffusion membrane and the filter membrane;

[0074] D is the diffusion coefficient of the target substance in the diffusion film (cm). 2 ·s -1 );

[0075] A is the window area of ​​the DGT device (cm²) 2 );

[0076] T is the placement time (s).

[0077] Step 4: Correspond the concentration of the target substance on the adsorption membrane with the one-dimensional profile of the interface between the sediment phase and the water phase in the sediment column core sample to obtain the one-dimensional profile concentration distribution of the target substance in the environmental medium or micro-interface.

[0078] Step 5: Divide the concentration of the target analyte into intervals according to gradient limits and mark them with different colors to complete the division of the sediment-water interface.

[0079] The one-dimensional concentration profile obtained through the above steps is uploaded to a computer for demonstration. Different concentration gradient limits are displayed in different colors, enabling the delineation of the sediment-water interface. Figure 4 The diagram shown illustrates the sediment-water interface delineation results. Table 1 details the different concentration gradient limits and their corresponding colors.

[0080] Table 1. Limits for different concentration gradients and their corresponding colors.

[0081]

[0082] There are two methods for dividing the target analyte concentration gradient limit interval:

[0083] Method 1: When soluble phosphate SRP and ammonia nitrogen NH4 + -N meets one of the following three conditions:

[0084] Condition 1: Soluble phosphate SRP ≤ 0.01 and ammonia nitrogen NH4 + -N≤0.1;

[0085] Condition 2: 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 + -N < 30;

[0086] Condition 3: Soluble phosphate SRP ≥ 5.2 and ammonia nitrogen NH4+ + -N≥30;

[0087] The method for dividing the target analyte concentration gradient limit interval is as follows:

[0088] When condition 1 is met, it is an overlying aqueous phase, marked in blue;

[0089] When condition 2 is met, it is a sediment-water interface region, marked in yellow;

[0090] When condition 3 is met, it is a sedimentary phase and is marked in brown.

[0091] Method 2: When soluble phosphate SRP and ammonia nitrogen NH4 + -N does not meet one of the following three conditions:

[0092] Condition 1: Soluble phosphate SRP ≤ 0.01 and ammonia nitrogen NH4 + -N≤0.1;

[0093] Condition 2: 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 +-N < 30;

[0094] Condition 3: Soluble phosphate SRP ≥ 5.2 and ammonia nitrogen NH4+ + -N≥30;

[0095] The method for dividing the target analyte concentration gradient limit interval is as follows:

[0096] When the soluble phosphate SRP is ≤0.01, it is the overlying aqueous phase and is marked in blue;

[0097] When 0.01 < soluble phosphate SRP < 5.2, it is the sediment-water interface region, marked in yellow;

[0098] When the soluble phosphate SRP is ≥ 5.2, it is a sedimentary phase and is marked in brown.

[0099] By using the two methods described above, the concentration of the target analyte is divided into intervals according to gradient limits and marked with different colors, thus completing the delineation of the sediment-water interface in the aquatic ecosystem. This invention's accurate delineation of the sediment-water interface in aquatic ecosystems provides a scientific basis for in-depth research on the migration and transformation patterns and environmental behavior of various pollutants at the sediment-water interface.

[0100] Although the present invention has been described in detail in this specification with general description and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for delineating a sediment-water interface in an aquatic ecosystem, characterized in that, The method comprises the following steps: Step 1, collecting a sediment core sample at a preset sampling point by using a gravity sediment sampler; Step 2, placing the collected sediment core sample in a constant-temperature water tank and carrying out simulation culture under the condition similar to the temperature of the sampling point; Step 3, obtaining the vertical distribution characteristics of the target substance concentration in the sediment core sample by using a flat plate type DGT device, wherein the flat plate type DGT device comprises a DGT probe and an adsorption film, the DGT probe is used for fixing the adsorption film, and the adsorption film is used for adsorbing and fixing the target substance; Step 4, corresponding the target substance concentration on the adsorption film to the one-dimensional profile of the sediment-water interface of the sediment phase of the sediment core sample, that is, obtaining the one-dimensional profile concentration distribution of the target substance in the environmental medium or micro-interface; Step 5, dividing intervals of the target substance concentration according to gradient limit values and marking different colors, and completing the division of the sediment-water interface; The target is soluble phosphate SRP and ammonia nitrogen NH4 + -N; In step 5, the method for dividing intervals of the target substance concentration gradient limit values is as follows: When the soluble phosphate SRP and ammonia nitrogen NH4 + - N meets one of the following three conditions, Condition 1, soluble phosphate SRP < 0.01 and ammonia NH4 + - N < 0.1 ; Condition 2, 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 + - N < 30; Condition 3, soluble phosphates SRP > 5.2 and ammonia NH4 + N > 30; Then the target substance concentration gradient limit value is divided into intervals as follows: When condition 1 is met, it is an overlying water phase, which is marked as blue; When condition 2 is met, it is a sediment-water interface region, which is marked as yellow; When condition 3 is met, it is a sediment phase, which is marked as brown; In step 5, another method for dividing intervals of the target substance concentration gradient limit values is as follows: When the soluble phosphate SRP and ammonia nitrogen NH4 + - N does not meet one of the following three conditions, Condition 1, soluble phosphate SRP < 0.01 and ammonia NH4 + N < 0.1 ; Condition 2, 0.01 < soluble phosphate SRP < 5.2 and 0.1 < ammonia nitrogen NH4 + - N < 30; Condition 3, soluble phosphates SRP > 5.2 and ammonia NH4 + N > 30; Then the target substance concentration gradient limit value is divided into intervals as follows: When the soluble phosphate SRP is less than or equal to 0.01, it is an overlying water phase, which is marked as blue; When 0.01 < soluble phosphate SRP < 5.2, it is a sediment-water interface region, which is marked as yellow; When the soluble phosphate SRP is greater than or equal to 5.2, it is a sediment phase, which is marked as brown.

2. The method of delimiting the sediment-water interface in an aquatic ecosystem according to claim 1, characterized in that, Step 3 comprises the following sub-steps: Sub-step 3.1, vertically inserting the DGT probe into the sediment-water interface and protruding 3-5 cm above the interface, after standing for 24-48 hours, recovering the DGT probe and taking out the adsorption film; Sub-step 3.2, cutting the adsorption film into a plurality of small pieces of adsorption film arranged longitudinally; Sub-step 3.3, eluting each small piece of adsorption film to obtain an eluent, and measuring the cumulative amount M of the target substance in the eluent; Sub-step 3.4, the concentration or flux determined by DGT is converted by formula (1) to obtain the concentration of the target determined by DGT C DGT mg / L; In the formula, M is the cumulative amount of the target analyte in the DGT, mg; Δg is the total thickness of the diffusion membrane and the filter membrane, cm; T is the standing time, s. C DGT mg / L is the concentration of the target substance determined by DGT; The gravity sediment sampler has a specification of L50 cm*Φ8.4 cm. ​ D is the diffusion coefficient of the target substance in the diffusion membrane, cm 2. s -1 ; A is the window area of the DGT device, cm 2 ; ​ 3. The method of claim 1, wherein the method is used for the determination of the sediment-water interface in an aquatic ecosystem. ​

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