A method for assessing the impact of mechanized harvesting on carbon sink of bottom-sowing shellfish farming

Abstract

The present application relates to a kind of method for evaluating the influence of mechanized harvesting on bottom sowing shellfish culture carbon sink, belong to marine carbon sink evaluation technical field, the method with mechanized harvesting link as key variable, can simulate, whole-process tracking, quantitative qualitative evaluation mechanized harvesting link influence on bottom sowing shellfish culture carbon sink, fill the technical gap, not only can the carbon source, carbon sink effect of this link be clear, but also can provide important basic data and methodological support for marine aquaculture carbon footprint evaluation, provide scientific basis and technical support for the green intelligent transformation of emission reduction and carbon sink and marine shellfish culture.

Description

Technical Field

[0001] This invention belongs to the field of marine carbon sink assessment technology, and relates to a method for assessing the impact of mechanized harvesting on carbon sinks in bottom-seeded shellfish aquaculture. Background Technology

[0002] Bottom-seeded shellfish aquaculture is an important blue carbon sink system in my country's coastal waters. Shellfish influence the biogeochemical cycle of carbon through processes such as filter feeding, calcification, and biological deposition, affecting phytoplankton, particulate organic debris, seawater carbonate systems, and sediment burial. With the increasing scale and mechanization of bottom-seeded shellfish aquaculture, raking and rotary-tooth mechanized harvesting have become the mainstream methods. However, the agitation, scraping, and movement of mechanized harvesting equipment can cause strong resuspension of surface sediments in the aquaculture area, leading to rapid release of sedimentary carbon pools, altered carbon migration pathways, and fluctuations in inert carbon formation efficiency, directly impacting the carbon emission intensity and stability of the bottom-seeded aquaculture system. To achieve higher-level and higher-quality energy conservation and carbon reduction, and effectively reduce carbon emissions at the source, this assessment can reveal the driving mechanism of harvesting disturbances on carbon sinks, establish a standardized evaluation system, and provide a scientific basis for optimizing mechanized operation parameters in bottom-seeded aquaculture, achieving synergy between increased aquaculture production and enhanced carbon sinks, and improving the assessment of the carbon footprint of marine aquaculture.

[0003] Currently, there are significant technical shortcomings in assessing the carbon sequestration impact of mechanized harvesting on bottom-seeded shellfish aquaculture: First, traditional studies only focus on the carbon sequestration of shellfish themselves, failing to consider mechanized operations as a core intervention variable, thus making it impossible to quantitatively analyze the driving effect of harvesting disturbances on carbon sequestration; second, there is a lack of sediment resuspension simulation devices adapted to the mechanized harvesting process of bottom-seeding, making it difficult to reproduce the intensity, depth, and range of disturbances in real operations, resulting in a lack of representative experimental data; third, it is impossible to dynamically track the harvesting process, carbon component release, migration and transformation, and component quantification, implicitly smoothing out the disturbance effects generated by mechanized operations, and existing technologies have also failed to include the mechanized harvesting process as an independent key intervention variable in carbon footprint analysis; fourth, there is a lack of environmental simulation devices for the degradation of organic carbon in sediments, making it impossible to accurately measure the degradation characteristics of organic carbon and the amount of inert carbon generated, and thus impossible to construct a complete causal relationship for carbon sequestration. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide an apparatus and method suitable for assessing the impact of towed and rotary toothed mechanized harvesting on carbon sinks in bottom-seeded shellfish aquaculture. This method uses the mechanized harvesting process as a key variable, is simulable, allows for full-process tracking, and provides quantitative and qualitative evaluation of the impact of mechanized harvesting on carbon sinks in bottom-seeded shellfish aquaculture. This fills a technological gap, not only clarifying the carbon source and carbon sink effects of this process but also providing crucial basic data and methodological support for assessing the carbon footprint of marine aquaculture. Furthermore, it offers scientific basis and technical support for emission reduction, carbon sink enhancement, and the green and intelligent transformation of marine shellfish aquaculture.

[0005] The present invention adopts the following technical solution.

[0006] An apparatus for assessing the impact of mechanized operations on carbon sequestration in bottom-seeded shellfish aquaculture, the apparatus comprising two parts: an acrylic sampling tube and a long-term indoor dark culture bottle, as detailed below:

[0007] The acrylic sampling tube, with stoppers at both ends, is used for collecting and preserving sediment samples from bottom-sown shellfish aquaculture areas. It is 15cm in length. The long-term dark culture bottle is made of opaque material and has a sampling port on its body. It is used for long-term dark culture of sediment from bottom-sown shellfish aquaculture areas. The dark culture bottle is made of high-density polyethylene, with a maximum volume of 5L. Its mouth is covered with a sterile, breathable sealing film, and the sampling port is a drain valve embedded 10cm from the bottom of the bottle.

[0008] A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the aforementioned device, the method comprising the following steps: S1 Sample Collection: Before mechanized harvesting, bottom seawater and sediments of the bottom-seeded shellfish aquaculture area were collected; based on the disturbance depth h of the bottom sediments in the aquaculture area caused by mechanized harvesting, sediments at depths of 0-h were obtained and their volume V1 and wet weight W were recorded; at the same time, based on the harvester's tillage width L, disturbance depth h, harvesting time T, and travel speed N, the sediment disturbance volume V0 of mechanized harvesting was calculated. S2. Indoor dark culture: The sediment obtained in step S1 and the bottom seawater were placed in a dark culture bottle in proportion and shaken thoroughly to simulate the disturbance of the bottom sediment caused by mechanized harvesting. An experimental group and a blank control group were set up and cultured for a long time in a dark environment at room temperature. S3. Periodic sampling and analysis: At different time points during the cultivation period, water and sediment samples were collected, and the concentrations of colored dissolved organic matter optical index, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC) in the water samples, as well as the concentration of particulate organic carbon (POC) in the sediments, were measured. S4. Qualitative Assessment: Based on the absorption spectrum of the colored dissolved organic matter measured in step S3, calculate the specific UV absorbance (SUVA). 245 Based on its changing trend during the incubation period, the characteristics of the transformation of dissolved organic matter into inert organic matter during sediment degradation were qualitatively evaluated. S5. Quantitative Assessment: Based on the carbon concentration data measured in step S3 and the total sample volume collected in step S1, the dissolved inorganic carbon M formed by the long-term degradation of sediments is quantified using a calculation model. DIC Inert dissolved organic carbon M RDOC Inert particulate organic carbon M RPOC and carbon dioxide emissions M CO2 ; S6. Comprehensive Carbon Effect Assessment: Combine the carbon component formation amounts calculated in step S5 with the diesel consumption carbon emissions from mechanized harvesting, and calculate the comprehensive effect value C of mechanized harvesting on the carbon sink of bottom-seeded shellfish aquaculture according to the following formula. T : C T =M h +44 / 12×(M CO2 -(M DIC +N DIC + M RDOC )) ×10 -6 / W d ; In the formula, M h The carbon dioxide emissions from diesel fuel consumed per unit weight of shellfish harvested are calculated by multiplying the diesel fuel consumption per ton of shellfish harvested by the greenhouse gas emission factor of the diesel fuel; W d The total wet weight of shellfish harvested by mechanized operations (V0 volume); When C T When the value is positive, the impact of mechanized operations on the carbon sink of bottom-seeded aquaculture is determined to be a net carbon source; otherwise, it is a net carbon sink.

[0009] Furthermore, in step S1, the formula for calculating the sediment disturbance volume V0 is: V0 = L × T × N × h.

[0010] Furthermore, in step S2, the long-term culture time is at least 200 days, and the sampling time points include days 0, 1, 5, 10, 30, 50, 100, and 200.

[0011] Furthermore, in step S3, the optical index of the colored dissolved organic matter is a UV-Vis absorption spectrum, and the specific UV absorbance SUVA is... 254 The value was calculated by the ratio of the absorption coefficient at a wavelength of 254 nm to the DOC concentration of the solution.

[0012] Furthermore, in step S5, the calculation model is as follows: M RDOC = V0×(C 200 DOCt - C 200 DOCc )×V / V1; M DIC = V0×(C 200 DICt - C 200 DICc )×V / V1; M RPOC = V0×(W×C 200 st ×Rt +(C 200 POCt - C 200 POCc )×V) / V1; M CO2 = (V0×R0×C0×W / V1)-M RDOC -M DIC - M RPOC ; Where: M DIC —DIC (mg) formed from long-term degradation of sediments; M RDOC —RDOC (mg) formed by long-term degradation of sediments; M RPOC —RPOC (mg) formed by long-term degradation of sediments; M CO2 —The amount of carbon dioxide released from the long-term degradation of sediments (mg, in C). V0—The volume of sediment disturbed during mechanized harvesting of bottom-sown shellfish aquaculture (m³) 3 ); C 200 DOCt —DOC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 DOCc —DOC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. V—Initial volume of seawater in the dark culture bottle (L); V1—Volume of deposits in the plexiglass tube (m³) 3 ); W—Wet weight (mg) of sediment added to the dark culture flask; C 200 DICt —DIC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 DICc —DIC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. C 200 POCt —POC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 POCc —POC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. C200 st —The carbon content of sediments in the long-term dark culture experimental group on day 200; R t —The wet-dry ratio (dimensionless) of the sediments from the long-term dark incubation experimental group on day 200 was 0.79; R0—the wet-dry ratio of the sediment (dimensionless), with a measured value of 0.79; C0—The carbon content of the sediment (dimensionless), with a measured value of 0.0009.

[0013] Furthermore, in step S6, the carbon dioxide emissions M from the diesel fuel consumed per unit weight of shellfish harvested are... h Calculate M using the following formula: h =α×β; In the formula, α represents the diesel consumption per ton of shellfish harvested, which is obtained based on actual measurements at the harvesting site, and β represents the greenhouse gas emission factor of diesel.

[0014] Furthermore, the bottom-sown shellfish is the four-cornered clam.

[0015] Furthermore, in step S1, the disturbance depth h is 9 cm, the harvester tillage width L is 1.2 m, and the travel speed N is 1.5 m / s.

[0016] Furthermore, in step S2, the dark culture bottle is made of high-density polyethylene with a maximum volume of 5L. Its mouth is covered with a sterile, breathable sealing film, and the bottle body is equipped with a discharge valve for sampling.

[0017] Furthermore, in step S3, before collecting the water sample, the dark culture bottle needs to be manually shaken and left to stand for 72 hours.

[0018] The beneficial effects of this invention compared to the prior art (1) The present invention designs a device for evaluating the impact of mechanized harvesting on carbon sequestration in bottom seeding shellfish aquaculture. The indoor dark long-term culture device can carry out multiple parallel experiments at the same time. It integrates shaking and mixing and convenient sampling modules. The device creates a long-term stable dark environment through a breathable and light-shielding design, effectively avoiding the interference of light on the long-term degradation process. It truly simulates the long-term degradation and carbon migration and transformation process of sediments in seawater, providing reliable experimental conditions for accurately evaluating the carbon fate of sediments after the severe disturbance during bottom seeding operations.

[0019] (2) This invention establishes an assessment method for the impact of mechanized harvesting on carbon sinks in bottom-seeded shellfish farming. Through qualitative and quantitative assessment, this invention combines key parameters such as the tillage width, harvesting depth, and travel speed of the bottom-seeded shellfish harvester, and comprehensively considers evaluation indicators of various carbon components such as DIC, RDOC, RPOC, and CO2. This avoids the bias of single indicators in the calculation of the impact of mechanized harvesting on carbon sinks in bottom-seeded shellfish farming, and maximizes the comprehensive impact of mechanized harvesting on carbon sinks in bottom-seeded shellfish farming. It can comprehensively and accurately quantify the carbon emissions or removal of bottom-seeded shellfish farming by mechanized harvesting, and clarify its carbon source and sink effect. It can provide methodological support for the evaluation of carbon footprint of bottom-seeded shellfish farming based on mechanized harvesting. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an indoor dark long-term incubation device. 1. Acrylic glass sampling tube; 2. Dark incubation bottle; 3. Discharge valve; 4. Sealing film. Figure 2 SUVA of water in dark culture flasks for sediment 254 The long-term dynamic changes. Detailed Implementation

[0021] The technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Example 1 like Figure 1 As shown, an apparatus for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture consists of two parts: an acrylic sampling tube and a long-term indoor dark culture bottle, as detailed below: Acrylic sampling tube 1, made of acrylic material, with plugs at both ends, has dimensions of height × diameter = 15cm × 2.9cm, and is used for the collection and preservation of sediment samples in bottom-seeded shellfish farming areas; The indoor dark long-term incubation module includes: Dark culture bottle 1 is made of opaque material and has a sampling port on its body for long-term dark culture of sediments. As a specific implementation, the dark culture bottle 1 is made of high-density polyethylene (HDPE) with a volume of 5L and dimensions of: height × bottom diameter = 25cm × 16cm, bottle mouth diameter of 10cm (the bottle mouth is covered with a sterile and breathable sealing film 4), and an outlet valve 3 is embedded 15cm from the bottom of the bottle body. The outlet valve 7 has a 10mm diameter threaded outlet for the discharge and collection of cultured seawater samples.

[0023] Example 2 This example provides a method for using the device described in the example, the method steps include: Step 1: In the field of bottom-seeded shellfish farming, the four-cornered clam is one of the varieties with relatively mature and widespread large-scale, standardized, and mechanized harvesting applications. Therefore, this embodiment takes bottom-seeded four-cornered clams as an example to calculate the carbon emissions from the mechanized harvesting of 1 ton of four-cornered clams using a drag-and-plow method. Before mechanized harvesting, seawater and sediment from the bottom of the bottom-seeded shellfish farming area are collected using a water sampler and a box-type sediment sampler. Based on the 9cm disturbance depth of the bottom sediment caused by mechanized harvesting of bottom-seeded shellfish, a pre-prepared plexiglass tube is vertically inserted into the box-type sediment sampler to obtain sediment at a depth of 0-9cm. Based on the inner diameter of the plexiglass tube and the 9cm depth of the obtained columnar sediment, the volume of the collected sediment is calculated as V1 = 5.941 × 10⁻⁶. - 5 m 3 The average wet weight of the sediment in the plexiglass tube was W=93.17g. The surface seawater was filtered through a 200 μm sieve (to remove larger impurities from the seawater) and then set aside for use. Step 2: By conducting on-site investigations of the shellfish harvester's tillage width L (i.e., the operating range of the harvesting equipment in contact with the sediment), the harvester's disturbance depth h, the harvesting time T, and the harvester's travel speed N, the sediment disturbance volume V for the entire mechanized harvesting of bottom-seeded shellfish is calculated. 0； V0 = L × T × N × h; In the formula, V0 represents the sediment disturbance volume during mechanized harvesting of bottom-seeded shellfish. Calculations show that the sediment disturbance volume during one hour of mechanized harvesting of four-cornered clams is 583.20 m³. 3 L is the tillage width of the shellfish harvester, with a measured value of 1.2m; T is the mechanized harvesting time for shellfish, with a measured value of 60 minutes (3600 seconds); N is the traveling speed of the shellfish harvester, with a measured value of 1.5m / s; h is the disturbance depth of the harvester, with a field survey value of 9cm. Step 3: Take the columnar deposit from the above-mentioned plexiglass tube and place it in dark culture bottle 2 of the indoor dark long-term culture module (see...). Figure 1As the experimental group, seawater samples were collected and thoroughly shaken to simulate the disturbance of the bottom sediment in the bottom-seeded shellfish farming area caused by mechanized harvesting. The final seawater volume of each dark culture bottle 2 was 4L. Each experimental group was set up with 5 replicates, and 3 blank control groups were set up (only 4L of bottom seawater from the four-cornered clam farming area before mechanized harvesting was added). 200ml water samples were collected from the dark culture bottles 2 on days 0, 1, 5, 10, 30, 50, 100, and 200 for DIC, DOC, POC content, and C content. For DOM optical index analysis, 10g of sediment from the acrylic tube in step 1 and 10g of sediment from the experimental group's dark incubation flask 2 on day 200 were taken for analysis of sediment organic carbon content. All samples were filtered through a 0.7μm glass fiber membrane (GF / F, 25mm) into 30ml amber glass reagent bottles that had been ignited at 450℃, acid-washed, and rinsed; these bottles were then frozen for later analysis of DIC and DOC content. The filter membranes were wrapped in foil, numbered, and frozen for later analysis of POC content. The long-term dark incubation flasks were placed in a dark environment at room temperature to eliminate interference from light during the dark incubation experiment.

[0024] Example 3 The method for assessing the impact of mechanized harvesting on carbon sequestration in clam farming, as described in Example 2, includes the following steps: Step A: The CDOM optical indexes at the above sampling time points were measured using a Shimadzu UV-2550 UV-Vis spectrophotometer to conduct a qualitative assessment of the impact of mechanized harvesting on carbon sequestration in clam farming.

[0025] Step B: Using ultrapure water as a blank, a baseline scan was performed. The above sample was spectrally scanned in the range of 200–800 nm with a scan interval of 1 nm. All absorbance values ​​were subtracted from the mean value in the wavelength range of 680–700 nm for refractive index difference and baseline drift correction. The absorption coefficient was calculated using the following formula: a(λ) = 2.303 × A(λ) / L; In the formula: a(λ) — absorption coefficient at wavelength λ ( / m). A(λ) — absorbance at wavelength λ, dimensionless L — cuvette length (m).

[0026] Step C, compare UV absorbance (SUVA) 254 () refers to the ratio of the absorption coefficient at a wavelength of 254 nm to the DOC concentration in the solution, which can trace the aromaticity of CDOM in aquatic systems. SUVA 254 Calculation formula: SUVA 254 =a(254) / C DOC； Where: SUVA 254—Specific UV absorbance (L / (mg·m)); a((254) — Absorption coefficient ( / m) at a wavelength of 254 nm at each sampling time point. C DOC —DOC concentration (mg / L) of water samples at each sampling time point.

[0027] Step D: Cultivate SUVA in water at each cultivation time point. 254 The changes in the carbon sequestration of clam farming were qualitatively assessed using the SUVA method, an important indicator characterizing the dissolved organic carbon (DOC) properties of the farming system. Aromaticity of the farming water increased with increasing SUVA ratio. 254 The higher the value, the stronger the aromaticity, and the higher the content of inert dissolved organic matter, allowing for long-term storage in seawater. (SUVA value in the water of the dark culture bottle 2 in the experimental group) 254 See the dynamic changes Figure 2 ; Furthermore, the DIC and DOC contents of water samples taken at each sampling time point in the aforementioned dark culture flask 2 were determined using a total organic carbon analyzer (Elementar Vario TOC Select, Germany) via high-temperature catalytic oxidation. The carbon content of sediment samples and the POC content of the glass fiber filter membrane (GF / F, 25mm) at the aforementioned sampling time points were determined using an Elementar EL elemental analyzer (Elementar GmbH, Germany). The C content was thus determined using the above methods. 200 DICt C 200 DICc The concentrations were 21.47 mg / L and 17.96 mg / L, respectively. 200 DOCt C 200 DOCc The concentrations were 3.54 mg / L and 2.64 mg / L, respectively. 200 POCt C 200 POCc The concentrations were 0.73 mg / L and 0.67 mg / L, respectively. 200 st The value was 0.0002, which was used to quantitatively assess the impact of mechanized harvesting on carbon sequestration in clam farming.

[0028] Step E: Based on the DIC, DOC, and POC contents of water samples at each sampling time point and the organic carbon content of sediments measured above, obtain the DIC, RDOC (residual extremely stable DOC in the dark culture water), RPOC (residual extremely stable POC in the dark culture water), and carbon dioxide release (CO2) formed by long-term dark culture of sediments according to the following formulas: M RDOC= V0×(C 200 DOCt - C 200 DOCc )×V / V1; M DIC = V0×(C 200 DICt - C 200 DICc )×V / V1; M RPOC = V0×(W×C 200 st ×R t +(C 200 POCt - C 200 POCc )×V) / V1; M CO2 = (V0×R0×C0×W / V1)-M RDOC -M DIC - M RPOC ; Where: M DIC —DIC (mg) formed from long-term degradation of sediments; M RDOC —RDOC (mg) formed by long-term degradation of sediments; M RPOC —RPOC (mg) formed by long-term degradation of sediments; M CO2 —The amount of carbon dioxide released from the long-term degradation of sediments (mg, in C). V0—The volume of sediment disturbed during mechanized harvesting of bottom-sown shellfish aquaculture (m³) 3 ); C 200 DOCt —DOC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 DOCc —DOC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. V—Initial volume of seawater in the dark culture bottle (L); V1—Volume of deposits in the plexiglass tube (m³) 3 ); W—Wet weight (mg) of sediment added to the dark culture flask; C 200 DICt —DIC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 DICc —DIC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. C 200 POCt —POC concentration (mg / L) in the water of the long-term dark incubation group of sediments on day 200. C 200 POCc —POC concentration (mg / L) in the water of the blank control group after long-term dark culture of sediments on day 200. C 200 st —The carbon content of sediments in the long-term dark culture experimental group on day 200; R t —The wet-dry ratio (dimensionless) of the sediments from the long-term dark incubation experimental group on day 200 was 0.79; R0—the wet-dry ratio of the sediment (dimensionless), with a measured value of 0.79; C0—The carbon content of the sediment (dimensionless), with a measured value of 0.0009.

[0029] Step F, based on field survey data, calculate the carbon dioxide emissions (M) of diesel fuel consumed in harvesting 1 ton of four-cornered clams. h Calculate using the following formula: M h= α×β; In the formula: α—the amount of diesel fuel consumed per ton of four-cornered clams (wet weight) by mechanized harvesting (kg / t). Field investigation showed that one harvesting machine consumes 8.3L of diesel fuel per hour, and the calculated value is 5.58. The greenhouse gas emission factor (kg CO2 / kg) of β-diesel is 3.82, according to the China Product Life Cycle Greenhouse Gas Emission Coefficient Database. Step G, the quantitative assessment of the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture is calculated using the following formula: C T =M h +44 / 12×(M CO2 -(M DIC +N DIC + M RDOC )) ×10 -6 / W d ; In the formula: C T —The total carbon emissions and removals per ton of four-cornered clams from mechanized harvesting on the carbon sink of bottom-seeded aquaculture (kg CO2 / t); W d—The total wet weight (t) of four-cornered clams harvested by mechanized operations in 1 hour was 1.25 according to field survey.

[0030] Step H, based on the qualitative and quantitative calculation results of the impact of mechanized harvesting on the carbon sink of bottom-seeded shellfish farming: (1) Qualitative analysis of the impact of sediment disturbance and resuspension caused by mechanized operations on the carbon migration and transformation characteristics of the bottom-seeded aquaculture system. The results show that the SUVA of the sediment dark culture experimental group 254 The aromaticity of the culture water initially decreased during the 0-5 day degradation process, indicating that the sediment released a high level of fulvic acid compounds into the sea under the action of microorganisms. Then, it significantly increased during the 5-30 day period, indicating an increase in the aromaticity of the culture water, suggesting that these fulvic acid compounds gradually transformed into relatively inert humic acids (see...). Figure 2 The aromaticity of the water is relatively stable during the 30-200 day cultivation period. That is, the resuspended sediment disturbed during the mechanized harvesting of bottom-seeded shellfish will form inert dissolved organic carbon with strong aromaticity in the seawater through the action of microorganisms and be stored for a long time; (2) Quantitatively assess the impact of mechanized harvesting on the carbon sink of bottom-seeded shellfish farming, as shown in Table 1. The results show that C T The value is 51.58 kg CO2 / t, which means that the carbon dioxide emissions from harvesting 1 ton of four-cornered clams (wet weight) through mechanized harvesting are 51.58 kg. Therefore, the carbon sink impact of mechanized harvesting on four-cornered clam farming is a carbon source.

[0031] Table 1. Impact of mechanized harvesting on carbon sink formation in bottom-seeded shellfish aquaculture. .

Claims

1. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the aforementioned device, characterized in that, The method includes the following steps: S1 Sample Collection: Before mechanized harvesting, bottom seawater and sediments of the bottom-seeded shellfish aquaculture area were collected; based on the disturbance depth h of the bottom sediments in the aquaculture area caused by mechanized harvesting, sediments at depths of 0-h were obtained and their volume V1 and wet weight W were recorded; at the same time, based on the harvester's tillage width L, disturbance depth h, harvesting time T, and travel speed N, the sediment disturbance volume V0 of mechanized harvesting was calculated. S2. Indoor dark culture: The sediment obtained in step S1 and the bottom seawater were placed in a dark culture bottle in proportion and shaken thoroughly to simulate the disturbance of the bottom sediment caused by mechanized harvesting. An experimental group and a blank control group were set up and cultured for a long time in a dark environment at room temperature. S3. Periodic sampling and analysis: At different time points during the cultivation period, water and sediment samples were collected, and the concentrations of colored dissolved organic matter optical index, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC) in the water samples, as well as the concentration of particulate organic carbon (POC) in the sediments, were measured. S4. Qualitative Assessment: Based on the absorption spectrum of the colored dissolved organic matter measured in step S3, calculate the specific UV absorbance SUVA. 254 Based on its changing trend during the incubation period, the characteristics of the transformation of dissolved organic matter into inert organic matter during sediment degradation were qualitatively evaluated. S5. Quantitative Assessment: Based on the carbon concentration data measured in step S3 and the total sample volume collected in step S1, the dissolved inorganic carbon M formed by the long-term degradation of sediments is quantified using a calculation model. DIC Inert dissolved organic carbon M RDOC Inert particulate organic carbon M RPOC and carbon dioxide emissions M CO2 ; S6. Comprehensive Carbon Effect Assessment: Combine the carbon component formation amounts calculated in step S5 with the diesel consumption carbon emissions from mechanized harvesting, and calculate the comprehensive effect value C of mechanized harvesting on the carbon sink of bottom-seeded shellfish aquaculture according to the following formula. T : C T =M h +44 / 12×(M CO2 -(M DIC +N DIC + M RDOC )) ×10 -6 / W d ; In the formula, M h The amount of carbon dioxide emissions from diesel fuel consumed to harvest a unit weight of shellfish, W d The total wet weight of shellfish harvested by mechanized operations (V0 volume); When C T When the value is positive, the impact of mechanized operations on the carbon sink of bottom-seeded aquaculture is determined to be a net carbon source; otherwise, it is a net carbon sink.

2. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S1, the formula for calculating the sediment disturbance volume V0 is: V0 = L × T × N × h.

3. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S2, the long-term culture time is at least 200 days, and the sampling time points include days 0, 1, 5, 10, 30, 50, 100, and 200.

4. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S3, the optical index of the colored dissolved organic matter is the ultraviolet-visible absorption spectrum, and the specific ultraviolet absorbance SUVA is... 254 The value was calculated by the ratio of the absorption coefficient at a wavelength of 254 nm to the DOC concentration of the solution.

5. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S5, the calculation model is: M RDOC = V0×(C 200 DOCt - C 200 DOCc )×V / V1; M DIC = V0×(C 200 DICt - C 200 DICc )×V / V1; M RPOC = V0×(W×C 200 st ×R t +(C 200 POCt - C 200 POCc )×V) / V1; M CO2 = (V0×R0×C0×W / V1)-M RDOC -M DIC - M RPOC ; Where: M DIC —DIC formed from long-term degradation of sediments, in mg; M RDOC —RDOC formed by long-term degradation of sediments, in mg; M RPOC —RPOC formed by long-term degradation of sediments, in mg; M CO2 —The amount of carbon dioxide released from the long-term degradation of sediments, expressed in mg (C). V0—The volume of sediment disturbed during mechanized harvesting of bottom-seeded shellfish aquaculture, in cubic meters (m³). 3 ; C 200 DOCt —DOC concentration in the water of the long-term dark incubation experiment group of sediments on day 200, in mg / L; C 200 DOCc —DOC concentration in the water of the blank control group after long-term dark culture of sediments on day 200, in mg / L; V—Initial volume of seawater in the dark culture flask, in liters (L); V1—Volume of deposits in the plexiglass tube, in cubic meters (m³). 3 ; W—Wet weight of sediment added to the dark culture flask, in mg; C 200 DICt —The concentration of DIC in the water of the long-term dark incubation group of sediments on day 200, in mg / L; C 200 DICc —The concentration of DIC in the water of the blank control group after long-term dark incubation of sediments on day 200, in mg / L; C 200 POCt —POC concentration in the water of the long-term dark incubation experiment group on day 200, in mg / L; C 200 POCc —POC concentration in the water of the blank control group after long-term dark culture of sediments on day 200, in mg / L; C 200 st —The carbon content of sediments in the long-term dark culture experimental group on day 200; R t —The wet-dry ratio of the sediment in the long-term dark culture experimental group on day 200, dimensionless, was 0.79; R0—Wet-to-dry ratio of sediments, dimensionless, measured value is 0.79; C0—The carbon content of the sediment, dimensionless, with a measured value of 0.0009.

6. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S6, the carbon dioxide emissions M from the diesel fuel consumed per unit weight of shellfish harvested are... h Calculate Mh using the following formula: Mh = α × β; In the formula, α represents the diesel consumption per ton of shellfish harvested, and β represents the greenhouse gas emission factor of diesel.

7. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, The bottom-sown shellfish is the four-cornered clam.

8. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S2, the dark culture bottle is made of high-density polyethylene with a maximum volume of 5L. Its mouth is covered with a sterile, breathable sealing film, and the bottle body is equipped with a liquid discharge valve for sampling.

9. A method for assessing the impact of mechanized harvesting on carbon sequestration in bottom-seeded shellfish aquaculture using the device according to claim 1, characterized in that, In step S3, before collecting the water sample, the dark culture bottle needs to be manually shaken and left to stand for 72 hours.

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