Method for measuring respiration and nitrous oxide emission of facility greenhouse ecosystem

Abstract

The invention belongs to the technical field of gas emission of terrestrial ecosystems, and particularly discloses a method for measuring respiration and nitrous oxide emission of a facility greenhouse ecosystem, which comprises the following steps: selecting a sampling point at the middle position in a facility greenhouse according to the layout and structural characteristics of the facility greenhouse; a ventilation opening of the facility greenhouse is closed and covered with a heat preservation cotton quilt, so that the facility greenhouse is in a dark closed environment, and gas in the greenhouse is collected through an injector and then stored through a gas bag; collecting the gas sample for multiple times within several hours to form a time gradient; measuring the concentration of carbon dioxide and the concentration of nitrous oxide in the gas sample to obtain gas concentration data, and recording the gas concentration data; according to the gas concentration data and the environment information of the facility greenhouse, the ecological system respiration and nitrous oxide emission rate of the facility greenhouse are determined. The method is suitable for measuring the respiration rate and the nitrous oxide emission rate of the ecological system in the facility greenhouse, the operation is simple and convenient, and the accuracy of obtained data is relatively high.

Description

Technical Field

[0001] The invention belongs to the technical field of quantitative determination of gas emissions from terrestrial ecosystems, and in particular relates to a method for determining the respiration and nitrous oxide emissions of a greenhouse ecosystem. Background Art

[0002] Greenhouses are important facilities for agricultural production. They can provide a suitable growth environment for plants, extend the growth time of crops, achieve off-season production, provide fresh vegetables and fruits for urban and rural residents, improve people's living standards, and increase farmers' income. In the past 30 years, the planting area of ​​greenhouses in my country has increased year by year, reaching 800,000 hectares, accounting for more than 60% of the global greenhouse area. Due to long-term unreasonable fertilization and irrigation, greenhouse gas emissions from greenhouse cultivation have also increased year by year, exacerbating global warming. The greenhouse gases directly emitted by greenhouses are mainly carbon dioxide and nitrous oxide. Unlike nitrous oxide emissions, carbon dioxide emitted by greenhouses is mainly reflected through ecosystem respiration, but carbon dioxide emitted by greenhouses can be recovered through plant photosynthesis. Therefore, to determine whether an ecosystem is a source or sink of carbon dioxide, it is mainly to compare the relative size of ecosystem respiration and photosynthesis (total productivity), that is, if the ecosystem respiration is greater than the total productivity, it is a carbon source, otherwise it is a carbon sink. Exploring the laws of ecosystem respiration and nitrous oxide emissions in greenhouses is of great significance for developing fertilization and irrigation control strategies and achieving greenhouse gas emission reduction goals in greenhouses.

[0003] At present, the methods for measuring greenhouse ecosystem respiration and nitrous oxide emissions mainly include the following:

[0004] Static box sampling-gas chromatography analysis: A static box is set up inside the greenhouse. First, the gas sample in the static box is collected by a syringe, and then the gas concentration is detected using gas chromatography and other analytical equipment. The disadvantages of this method are: the base area of ​​the static box is limited, which blocks the flow of roots and water nutrients, and interferes with the changes in local environmental factors in the box. For example, the ridge cultivation pattern and uneven fertilization and irrigation of crops in the greenhouse cause a large spatial variation in water and nutrients in the soil, and the bottom of the static box is often insufficient, resulting in a large spatial variation in the monitoring results, strong uncertainty, and difficulty in guiding actual production. In addition, the static box method is also time-consuming and labor-intensive when sampling.

[0005] Sensor monitoring and analysis: Install relevant gas sensors in the greenhouse to monitor gases such as carbon dioxide and nitrous oxide in real time. Although sensor technology can provide continuous data, the accuracy and stability of the sensor are affected by environmental factors and require regular calibration and maintenance. This method requires a high purchase cost and is not convenient for grassroots application.

[0006] Model simulation analysis: By building a mathematical model, the generation and emission process of greenhouse gases in the greenhouse is simulated. This method requires a large amount of field data for model verification, and the accuracy and applicability of model parameters are key issues. At present, there is no widely recognized greenhouse gas emission prediction model suitable for greenhouses.

[0007] In summary, the above methods are not conducive to the determination of ecosystem respiration and nitrous oxide emission rates in greenhouse facilities. There is a large gap between the simulated situation and the actual situation. The data are not representative enough. Some methods are cumbersome to operate and have high requirements for tools and equipment, which have certain limitations. Summary of the invention

[0008] In view of the above-mentioned problems, the purpose of the present invention is to provide a method for measuring the ecosystem respiration and nitrous oxide emissions in a greenhouse facility, which is suitable for measuring the ecosystem respiration and nitrous oxide emission rate in a greenhouse facility. The obtained data has high accuracy and can conveniently, quickly and accurately measure the ecosystem respiration and nitrous oxide emissions in the greenhouse facility in real time.

[0009] The technical solution of the present invention is: a method for measuring the respiration and nitrous oxide emission of a greenhouse ecosystem, comprising the following steps:

[0010] S1. Selection of sampling points

[0011] According to the layout and structural characteristics of the facility greenhouse, a sampling point was selected in the middle position inside the facility greenhouse.

[0012] S2. Sampling

[0013] Close the vents of the greenhouse and cover it with a thermal blanket to keep the greenhouse in a dark and closed environment. Use a syringe to collect the gas in the greenhouse and then store it in an air bag. Collect gas samples multiple times over several hours to form a time gradient.

[0014] S3. Sample testing

[0015] The concentration of carbon dioxide and the concentration of nitrous oxide in the gas sample in step S2 are measured by a gas chromatograph to obtain gas concentration data, and the gas concentration data are recorded.

[0016] S4. Data Analysis

[0017] According to the gas concentration data in step S3 and the environmental information of the greenhouse, the ecosystem respiration and nitrous oxide emission rates of the greenhouse are determined.

[0018] Furthermore, the sampling frequency of the time gradient in step S2 is 2 to 5 times, that is, the gas samples are collected 2 to 5 times according to a certain time period to form a time gradient.

[0019] Furthermore, in step S2, the gas in the greenhouse is collected after the greenhouse has been in a dark and closed environment for 1 hour to 1.5 hours.

[0020] Furthermore, before collecting the gas with a syringe in step S2, the syringe needs to be pretreated, and the pretreatment is to rinse the syringe.

[0021] Furthermore, the specific steps of pretreatment are: after arriving at the sampling point, repeatedly pull out the syringe 3 to 5 times, and use the air in the facility greenhouse to rinse the lumen and wall of the syringe.

[0022] Furthermore, in step S2, the air bag needs to be pretreated before storing gas. The pretreatment is to clean the air bag. The specific steps are: use high-purity nitrogen to clean the air bag, and use a vacuum pump to evacuate the air bag. After repeating this operation 2-3 times, the air bag is evacuated to vacuum for standby use.

[0023] Furthermore, the environmental information of the facility greenhouse collected in step S4 includes the volume of the facility greenhouse, the planting area of ​​plants in the facility greenhouse, and the air temperature in the facility greenhouse.

[0024] Furthermore, the emission rate of carbon dioxide in step S4 is Calculated according to formula (1).

[0025]

[0026] in, represents the emission rate of carbon dioxide, in kgCO2-C / ha / d; ΔC1 / Δt1 represents the rate of change of carbon dioxide gas concentration in the greenhouse, in ppm / h; V represents the volume of the greenhouse, in m 3 ; S represents the planting area of ​​plants in the greenhouse, in ha; T represents the air temperature in the greenhouse; e represents the unit conversion coefficient.

[0027] Furthermore, the emission rate of nitrous oxide in step S4 is Calculated according to formula (2).

[0028]

[0029] in, represents the emission rate of nitrous oxide, in gN2O-N / ha / d; ΔC2 / Δt2 represents the rate of change of nitrous oxide gas concentration in the greenhouse, in ppm / h; V represents the volume of the greenhouse, in m 3; S represents the planting area of ​​plants in the greenhouse, in ha; T represents the air temperature in the greenhouse; e represents the unit conversion coefficient.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention is suitable for measuring the ecosystem respiration and nitrous oxide emission rate in a greenhouse facility, and there is no environmental separation with the greenhouse facility during sampling. The environmental conditions during sampling are the environmental conditions of the greenhouse facility, and the obtained data has high accuracy, and can more accurately measure the ecosystem respiration and nitrous oxide emission of the greenhouse facility in actual production. In addition, the sampling steps of the present invention are simple, the requirements for tools and equipment are less professional, and the limitations are relatively small. When sampling, the gas in the greenhouse is collected by a syringe and then stored in an air bag, which will not affect the plants in the greenhouse facility, that is, it will not interfere with the changes in environmental factors in the test site, and the farmers have a high degree of acceptance, which is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a process module diagram of the present invention;

[0033] Figure 2 It is the result of the nighttime ecosystem respiration monitoring in the greenhouse facility of the application example of the present invention;

[0034] Figure 3 This is the nighttime nitrous oxide emission monitoring result of the greenhouse facility in the application example of the present invention. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below. In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0036] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0037] Example

[0038] like Figure 1A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions shown in the present invention comprises the following steps:

[0039] S1. Selection of sampling points

[0040] Select a greenhouse where common crops are grown, and select a sampling point in the middle of the greenhouse according to its layout and structural characteristics. It should be noted that the selected greenhouse needs to be well-sealed, otherwise gas leakage will cause concentration accumulation deviations, which will affect the final calculation results.

[0041] S2. Sampling

[0042] Close the vents of the greenhouse and cover it with a heat-insulating blanket to keep the greenhouse in a dark and closed environment. Collect the gas in the greenhouse with a syringe and store it in an air bag. Collect gas samples several times within several hours to form a time gradient. The air bag in this embodiment uses an aluminum foil air bag with good sealing performance, with a specification of 0.3L to 1L.

[0043] S3. Sample testing

[0044] The carbon dioxide concentration and nitrous oxide concentration in the gas sample of step S2 are measured by a gas chromatograph to obtain gas concentration data, and the gas concentration data are recorded; wherein, the change of carbon dioxide concentration over time is used to calculate the ecosystem respiration of the greenhouse facility, the carbon dioxide concentration is used to characterize the ecosystem respiration of the greenhouse facility, and the change of nitrous oxide concentration over time can calculate its emission rate.

[0045] S4. Data Analysis

[0046] The gas concentration data of step S3 and the environmental information of the greenhouse are used to determine the ecosystem respiration and nitrous oxide emission rate of the greenhouse.

[0047] According to the experimental results, relevant analysis results can be issued, including the changing patterns of carbon dioxide concentration and nitrous oxide concentration, peak period and emission rate, etc. The analysis results can be used for subsequent research and can also serve as an important basis for improving greenhouse fertilization and irrigation strategies.

[0048] Preferably, the sampling frequency of step S2 according to the time gradient is 2 to 5 times. That is, 2 to 5 gas samples are collected regularly according to a certain time period to form a time gradient. It should be noted that the sampling frequency should be planned according to the actual conditions such as season, climatic conditions and crop growth stage to ensure the representativeness and effectiveness of the gas concentration data. For example, in winter, because the vents of the greenhouse facilities are closed for a long time, 4 or 5 samplings can be set, and in spring and autumn, it can be reduced to 2 or 3 times depending on the situation.

[0049] Preferably, step S2 collects the gas in the greenhouse after the greenhouse is in a dark and closed environment for 1h to 1.5h. It should be noted that: after the greenhouse vent is closed for 1h to 1.5h, enter the greenhouse through the buffer room of the greenhouse for sampling. Traditional greenhouses generally have a buffer room to meet the needs of normal agricultural production, and entering through this can reduce the impact of air circulation on the experimental results due to opening the door. Usually the roller shutter of the greenhouse is closed at 16:00-17:00 in the afternoon and opened at 07:00-08:00 the next day. Therefore, it is recommended to sample from 18:00 in the afternoon to 06:00 in the morning.

[0050] Preferably, the syringe in step S2 can be a disposable syringe with a specification of 50ml-200ml. In actual use, the disposable syringe is connected to the air bag inlet through a connecting pipeline, and a three-way valve is set on the connecting pipeline. When sampling, the gas in the greenhouse is extracted using the syringe and the connected three-way valve. After adjusting the three-way valve, the gas extracted by the syringe is injected into the air bag again, and this is repeated several times until the air bag is full, and multi-point sampling is performed.

[0051] Preferably, before collecting the gas with a syringe in step S2, the syringe needs to be pretreated, and the pretreatment is to rinse the syringe.

[0052] Preferably, the specific steps of pretreatment are: after reaching the sampling point, first repeatedly draw the syringe 3 to 5 times, and use the air in the facility greenhouse to rinse the syringe lumen and tube wall. Rinsing the syringe with the air in the facility greenhouse effectively reduces the contamination of residual gas in the syringe, which is more conducive to the purity of the sample collected by the syringe during later sampling.

[0053] Preferably, in step S2, the air bag needs to be pre-treated before storing the gas, and the pre-treatment is to clean the air bag, and the specific steps are: use high-purity nitrogen to clean the air bag, and use a vacuum pump to evacuate the air bag to vacuum, repeat this operation 2-3 times, and then evacuate the air bag to vacuum for standby use. Pre-treating the air bag to ensure that there is no other gas in the air bag when storing the sample is conducive to the accuracy of the measurement result.

[0054] Preferably, the environmental information of the facility greenhouse collected in step S4 includes the volume of the facility greenhouse, the planting area of ​​plants in the facility greenhouse, and the air temperature in the facility greenhouse.

[0055] Preferably, the emission rate of carbon dioxide in step S4 is Calculated according to formula (1).

[0056]

[0057] in, Indicates the emission rate of carbon dioxide, in kgCO2-C / ha / d. ΔC1 / Δt1 indicates the rate of change of carbon dioxide gas concentration in the greenhouse, in ppm / h. V indicates the volume of the greenhouse, in m 3 . S represents the planting area of ​​the plants in the greenhouse, in ha. T represents the air temperature in the greenhouse. e represents the unit conversion factor. It should be noted that if the bottom area of ​​the greenhouse is planted with plants, V / S can be replaced by the average height H of the greenhouse, and the unit of the average height H is m.

[0058] Preferably, the emission rate of nitrous oxide in step S4 is Calculated according to formula (2).

[0059]

[0060] in, Indicates the emission rate of nitrous oxide, in gN2O-N / ha / d. ΔC2 / Δt2 indicates the rate of change of nitrous oxide gas concentration in the greenhouse, in ppm / h. V indicates the volume of the greenhouse, in m 3 . S represents the planting area of ​​the plants in the greenhouse, in ha. T represents the air temperature in the greenhouse. e represents the unit conversion factor. It should be noted that if the bottom area of ​​the greenhouse is planted with plants, V / S can be replaced by the average height H of the greenhouse, and the unit of the average height H is m.

[0061] Application Examples

[0062] The feasibility of the greenhouse ecosystem respiration and nitrous oxide emission determination method proposed in the present invention is based on the selected time period. The time period selected in this embodiment is from 18:00 to 6:00 the next day. The specific time period varies with the season and there is no fixed limit. The gas concentration in the greenhouse conforms to the linear cumulative change law, so this law needs to be verified before the method is formally implemented. The specific method is: use a gas concentration real-time monitoring instrument to monitor several traditional greenhouses in the same time period as the present invention, and select the change law of carbon dioxide concentration and nitrous oxide concentration in 6 greenhouses as an example. The results are as follows: Figure 2 , Figure 3 As shown, Figure 2 , Figure 3 The data of the six greenhouses were collected from December 2022 to March 2023. It can be seen that Figure 2 , Figure 3 The variation patterns of carbon dioxide concentration and nitrous oxide concentration in the greenhouse over time are demonstrated: under dark and closed conditions, the concentrations of the two gases show an obvious linear cumulative trend, proving that the present invention is reasonable and feasible for estimating ecosystem respiration and nitrous oxide emissions.

[0063] Furthermore, the method for measuring ecosystem respiration and nitrous oxide emissions in greenhouses proposed in an embodiment of the present invention was used to measure ecosystem respiration and nitrous oxide emissions in 10 greenhouses in different villages in Weifang from September 2023 to May 2024, specifically:

[0064] Four sampling times were determined based on the specific conditions of the greenhouse facilities during the sampling period, namely 17:00, 19:00, 21:00 on the day and 7:00 on the next day.

[0065] In each time period, a disposable syringe and an aluminum foil air bag were used to collect gas, and then the gas samples were sent to the laboratory for gas chromatography analysis. The analysis data results are shown in Table 1.

[0066] Table 1: Test results of greenhouse gas samples in rural areas of Weifang

[0067]

[0068] Through data analysis, the emission of nitrous oxide and ecosystem respiration in the greenhouses at night was confirmed, as shown in Table 1. The emission rates of nitrous oxide and ecosystem respiration in the "Zhaili Village 2" greenhouse were the lowest at night, which were 18.8gN2O-N / ha / d and 13.2kgCO2-C / ha / d, respectively; the emission rates of nitrous oxide and ecosystem respiration in the "Yangzhuang 3" greenhouse were the lowest at night, which were 140.1gN2O-N / ha / d and 105.9CO2-C / ha / d, respectively.

[0069] Subsequently, based on the above data, combined with the investigation of the fertilization and irrigation conditions of each greenhouse, corresponding optimization strategies were proposed. For example, the existing facilities of greenhouses can be used, combined with the actual production habits of farmers, to quickly and accurately measure the ecosystem respiration and nitrous oxide emissions of greenhouses in actual production, while avoiding the interference and inconvenience caused by the installation of specific equipment in conventional methods, and farmers have a high degree of acceptance.

[0070] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions, characterized in that: The following steps are involved: S1. Selection of sampling points According to the layout and structural characteristics of the greenhouse, a sampling point was selected in the middle of the greenhouse; S2. Sampling Close the vents of the greenhouse and cover it with a heat-insulating blanket to keep the greenhouse in a dark and closed environment. Collect the gas in the greenhouse with a syringe and store it in an air bag. Collect gas samples several times over several hours to form a time gradient. S3. Sample testing Using a gas chromatograph to measure the carbon dioxide concentration and the nitrous oxide concentration in the gas sample in step S2 to obtain gas concentration data, and then recording the gas concentration data; S4. Data Analysis According to the gas concentration data in step S3 and the environmental information of the greenhouse, the ecosystem respiration and nitrous oxide emission rates of the greenhouse are determined.

2. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 1, characterized in that: The sampling frequency of step S2 according to the time gradient is 2 to 5 times.

3. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 1, characterized in that: In the step S2, the gas in the greenhouse is collected after the greenhouse is in a dark and closed environment for 1 hour to 1.5 hours.

4. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 1, characterized in that: Before collecting the gas with a syringe in step S2, the syringe needs to be pre-treated, and the pre-treatment is to rinse the syringe.

5. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 4, characterized in that: The specific steps of the pretreatment are: after arriving at the sampling point, the syringe is repeatedly pulled out 3 to 5 times, and the lumen and wall of the syringe are rinsed with air in the facility greenhouse.

6. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 1, characterized in that: In step S2, the air bag needs to be pretreated before storing gas. The pretreatment is to clean the air bag. The specific steps are: use high-purity nitrogen to clean the air bag, and use a vacuum pump to evacuate the air bag. After repeating this operation 2-3 times, the air bag is evacuated to vacuum for standby use.

7. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 1, characterized in that: The environmental information of the greenhouse collected in step S4 includes the volume of the greenhouse, the planting area of ​​plants in the greenhouse, and the air temperature in the greenhouse.

8. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 7, characterized in that: The emission rate of carbon dioxide in step S4 According to formula (1), in, represents the emission rate of carbon dioxide, in kg CO2-C / ha / d; ΔC1 / Δt1 represents the rate of change of carbon dioxide gas concentration in the greenhouse, in ppm / h; V represents the volume of the greenhouse, in m 3 ; S represents the planting area of ​​plants in the greenhouse, in ha; T represents the air temperature in the greenhouse; e represents the unit conversion coefficient.

9. A method for measuring greenhouse ecosystem respiration and nitrous oxide emissions as claimed in claim 7, characterized in that: The emission rate of nitrous oxide in step S4 According to formula (2), in, represents the emission rate of nitrous oxide, in g N2O-N / ha / d; ΔC2 / Δt2 represents the rate of change of nitrous oxide gas concentration in the greenhouse, in ppm / h; V represents the volume of the greenhouse, in m 3 ; S represents the planting area of ​​plants in the greenhouse, in ha; T represents the air temperature in the greenhouse; e represents the unit conversion coefficient.

Images