Device for monitoring methane emission of wetland by adopting electric signals generated by soil

Abstract

The utility model discloses a device for monitoring wetland methane emission by adopting a soil electric signal. The device comprises an anode electrode group, an external resistor, a reference electrode, a reference electrode chamber, a data collector and a monitoring terminal, the anode electrode group consists of a plurality of anode electrodes and an anode seat, the anode electrodes are inserted into wetland bottom mud, and the top ends of the anode electrodes are fixedly connected with the lower surface of the anode seat; the reference electrode chamber is of a hollow cylindrical structure with an open bottom and a sealed top, the bottom of the reference electrode chamber is isolated from overlying water by adopting a proton exchange membrane, an electrolyte solution is filled in the reference electrode chamber, and the reference electrode penetrates through the top of the reference electrode chamber and is inserted into the electrolyte solution; the external resistor is connected with a data collector in parallel, and the data collector is connected with a monitoring terminal through an electric signal. The device disclosed by the utility model is divided into a fixed methane monitoring sensor and a floating methane monitoring sensor according to the position of the reference electrode chamber, so that the device can meet the detection requirements of wetlands with different overlying water depths.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of environmental protection technology, more particularly to a device for monitoring wetland methane emission by using soil electricity generation signal. BACKGROUND

[0002] Methane is an important greenhouse gas, mainly produced in wetland environment. Detecting wetland methane emission helps to accurately assess carbon emission, and the commonly used methane detection methods include static box method (PLOS ONE, 2021, e0256796), infrared spectroscopy method (Journal of Agricultural Meteorology, 2021, 77:160-165), gas flux tower positioning monitoring method (Environmental Research Letter. 2021, 044038) and the like. The collected gas needs to be detected by gas chromatography, which has the problems of high labor cost and high detection cost.

[0003] Previous studies have found that electricity-producing bacteria are ubiquitous in wetland sediments, and their number is highly significantly correlated with the number of methanogens, and the electrical signal intensity of electricity-producing bacteria is also highly significantly correlated with methane emission flux (FEMS Microbiology Ecology, 2019, 95:fiz018). In the previous study, the inventors designed a reference electrode as a cathode to construct a sediment microbial fuel cell to monitor methane emission, but this scheme requires the reference electrode chamber to float on the surface of the overlying water, and the anode is buried in the sediment. For wetlands with deep overlying water such as lakes, the reference electrode chamber and the anode need to be separated because the reference electrode chamber floating on the surface of the overlying water is far away from the anode in the sediment. For wetlands with shallow overlying water, such as rice fields, the water depth is not enough to make the reference electrode chamber float, and the reference electrode chamber will sink into the sediment, affecting the detection, so the reference electrode chamber needs to be fixed above the anode in the overlying water to keep the proton exchange membrane below the water surface of the overlying water.

[0004] Based on the above, the utility model designs a detachable sensor structure that can adapt to different overlying water depths, thereby meeting the detection needs in different wetlands. SUMMARY

[0005] The utility model aims at providing a device for monitoring wetland methane emission by using soil electricity generation signal, comprising an anode electrode group, an external resistance, a reference electrode, a reference electrode chamber, a data collector and a monitoring terminal.

[0006] The anode electrode group is composed of a plurality of anode electrodes and an anode seat, the anode electrodes are inserted into the wetland sediment, the top end of the anode electrode is fixedly connected with the lower surface of the anode seat, the anode seat is a circular ring, screw holes B are formed in the circular ring, and the anode electrode is connected with the external resistor and the reference electrode in series through a wire;

[0007] The reference electrode chamber is provided with a float, the reference electrode chamber has a hollow cylindrical structure with an open bottom and a sealed top, the bottom is isolated from overlying water by using a proton exchange membrane, and the reference electrode chamber is provided with an electrolyte solution, the reference electrode is inserted into the electrolyte solution through the top of the reference electrode chamber;

[0008] The bottom outside of the reference electrode chamber is provided with a circular ring A which is matched with the size of the anode seat, screw holes A which are matched with the screw holes B are formed in the circular ring A, when the overlying water level is high, the reference electrode chamber is floated in the overlying water of the wetland sediment through the float, and when the overlying water level is low, the screw holes A in the circular ring A are fixed with the screw holes B in the anode seat through screws;

[0009] The external resistor is connected with a data collector in parallel, and the data collector is connected with a monitoring terminal through an electric signal.

[0010] Further, the material of the anode electrode is stainless steel, graphite or carbon felt.

[0011] Further, the reference electrode is a silver chloride electrode.

[0012] Further, the electrolyte solution is a saturated potassium chloride solution.

[0013] When the device is used for monitoring methane emission, the following steps are included:

[0014] Step 1, fixing a proton exchange membrane at the bottom opening of the reference electrode chamber, pouring an electrolyte solution into the reference electrode chamber, and inserting the reference electrode into the electrolyte solution through the top of the reference electrode chamber;

[0015] Step 2, suspending the reference electrode chamber on the water surface or fixing the reference electrode chamber on the anode seat according to the water level, and then burying the anode in the wetland sediment, and connecting the anode with the external resistor and the reference electrode in series through a wire;

[0016] Step 3, connecting the data collector with the external resistor in parallel, collecting the voltage data of the external resistor through the data collector, and sending the voltage data to the monitoring terminal to obtain real-time voltage data for monitoring the methane emission.

[0017] The device of the utility model can be divided into a fixed methane monitoring sensor and a floating methane monitoring sensor according to the position of the reference electrode chamber. The key of the utility model lies in that the reference electrode chamber can be fixed or separated from the anode seat, so that the wetland detection needs of different overlying water depths can be met.

[0018] The device can realize real-time online monitoring of methane emission flux of different wetlands, has simple operation, low labor demand and low detection cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 is a structural schematic diagram of the device, in which: 1 is an anode electrode, 2 is an anode seat, 3 is a wire, 4 is an external resistor, 5 is a reference electrode, 6 is a reference electrode chamber, 7 is a proton exchange membrane, 8 is a float, 9 is a data collector, and 10 is a monitoring terminal.

[0020] Figure 2 Fig. 2 is a comparison between the methane emission flux measured by the static chamber method and the voltage signal measured by the device in the waterlogged growth period of rice in Example 1, in which the error line is the standard error of three repeated samples.

[0021] Figure 3 Fig. 3 is a comparison between the methane emission flux measured by the static chamber method and the voltage signal measured by the device in Example 2 in the summer of 2024, and a comparison between the methane emission flux measured by the static chamber method and the voltage signal measured by the device in the winter of 2023, in which the error line is the standard error of three repeated samples. DETAILED DESCRIPTION

[0022] The preferred embodiments of the device will be described in detail below with reference to the examples. It should be understood that the following examples are given only for the purpose of illustration and are not intended to limit the scope of the device. Those skilled in the art can make various modifications and replacements to the device without departing from the spirit and principles of the device.

[0023] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0024] The materials and reagents used in the following examples can be obtained from commercial channels unless otherwise specified. Example 1

[0025] In a rice field in Qixia District, Nanjing City, gas collection was performed by the static chamber method from the first day after transplanting. A total of three chambers were arranged as three replicates, each chamber was inserted into the soil about 5 cm, and the rice plants were covered. Gas was collected every 6 days, and three repeated gas samples were collected each time. The sampling time was fixed at 14:00-16:00, and the gas collection work ended on the 71st day after transplanting. The collected gas was stored in a 20 mL vacuum gas collection bottle, and the methane concentration was determined by a gas chromatograph.

[0026] Meanwhile, three above-mentioned fixed methane monitoring sensors are constructed as three repetitions near the position of collecting gas by static box on the 3rd day after transplanting. Specifically, three stainless steel rods (φ1.0 cm×20 cm) are fixed on a plastic anode seat 2 as an anode electrode 1, then the whole anode seat 2 is completely inserted into the bottom mud, and a titanium wire lead 3 is drawn out; the inner diameter and height of a reference electrode chamber 6 are both 5 cm, a proton exchange membrane 7 is fixed at the bottom of the reference electrode chamber 6, and a circular ring A which is suitable in size for the anode seat 2 is sleeved on the outside of the bottom, and the circular ring A and the anode seat 2 are fixed and connected together by screws. 95 mL saturated potassium chloride solution is contained in the closed reference electrode chamber 6, and the diaphragm end of a reference electrode 5 is soaked in the saturated potassium chloride solution. The reference electrode 5 is connected in series with the anode electrode 1 through a 20000 Ω external resistance 4; a data collector 9 is used to record and remotely send a voltage data to a monitoring terminal 10 at 15:00 every day, and the monitoring lasts until the 71st day after transplanting.

[0027] As shown in Figure 2 , the voltage of the sensor constructed by the utility model and the methane emission flux have extremely significant correlation. Example 2

[0028] Three above-mentioned floating methane monitoring sensors are constructed in the center of Xianlin Lake in Xianlin Campus of Nanjing Normal University. Specifically, an anode electrode 1 composed of three stainless steel rods (φ1.0 cm×20 cm) is fixed on a plastic anode seat 2, then the whole anode seat 2 is completely inserted into the bottom mud, and a titanium wire lead 3 is drawn out; the inner diameter of a reference electrode chamber 6 is 5 cm, the height is 5 cm, and 95 mL saturated potassium chloride solution is injected from the top opening after the bottom is sealed by a proton exchange membrane 7, and the diaphragm end of a reference electrode 5 is soaked in the saturated potassium chloride solution. A float 8 is installed on the outer wall of the reference electrode chamber 6 so that the reference electrode chamber 6 can change with the water level and can be kept floating on the water surface for a long time. The reference electrode 5 is connected in series with the anode electrode 1 through a 20000 Ω external resistance 4; a data collector 9 is used to record and remotely send a voltage data every 15 minutes. Meanwhile, the static box method is used to collect gas, three box bodies are arranged as three repetitions, each box body is inserted into the wetland sediment about 5 cm, and gas is collected 5 times in 40 hours in each of a summer day and a winter day, 3 gas samples are collected for each time, the gas is stored in a 20 mL vacuum gas collection bottle, and the methane concentration in the collected gas is determined by using a gas chromatograph.

[0029] As shown in Figure 3 , the voltage of the sensor constructed by the utility model in summer and the methane emission flux are both obviously higher than those of the sensor in winter; and in the same day, the methane emission flux is also higher in the period when the voltage of the sensor is higher, which indicates that the voltage of the sensor and the methane emission flux have good correlation, and can be used as an index for monitoring the methane emission flux.

Claims

1. A device for monitoring methane emission from wetlands using soil-generated electrical signals, characterized by, Anode electrode group, external resistance, reference electrode, reference electrode chamber, data collector and monitoring terminal are included. The anode electrode group is composed of a plurality of anode electrodes (1) and an anode seat (2), the bottom end of the anode electrode (1) is inserted into the wetland sediment, the top end of the anode electrode (1) is fixedly connected with the lower surface of the anode seat (2), the anode seat (2) is in the shape of a circular ring, a screw hole B is formed on the circular ring, the anode electrode (1) is connected in series with the external resistance (4) and the reference electrode (5) through a wire; The reference electrode chamber (6) is provided with a float (8), the reference electrode chamber (6) is in the form of a hollow cylinder with an open bottom and a sealed top, the bottom is isolated from the overlying water by a proton exchange membrane (7), the reference electrode chamber (6) is provided with an electrolyte solution, the reference electrode (5) is inserted into the electrolyte solution through the top of the reference electrode chamber (6); The bottom outside of the reference electrode chamber (6) is provided with a circular ring A which is suitable in size for the anode seat, a screw hole A is formed on the circular ring A which is suitable for the screw hole B, when the water level of the overlying water is high, the reference electrode chamber is floated in the overlying water of the wetland sediment by the float, when the water level of the overlying water is low, the screw hole A on the circular ring A is fixed with the screw hole B on the anode seat by a screw; The external resistance (4) is connected in parallel with the data collector (9), the data collector (9) is connected with the monitoring terminal (10) through an electric signal.

2. The apparatus of claim 1, wherein, The material of the anode electrode (1) is stainless steel, graphite or carbon felt.

3. The apparatus of claim 1, wherein, The reference electrode (5) is a silver chloride electrode.

4. The apparatus of claim 1, wherein, The electrolyte solution is a saturated potassium chloride solution.

Images