A device and method for rapid in-situ determination of water denitrification rate

Abstract

The present invention discloses a new method for rapid in-situ determination of the denitrification potential of water bodies. The apparatus required for the new method includes a purge device, a modified flexible water bag, a water vapor separation device, a mass spectrometer, a peristaltic pump, a gas flow meter, a PVC hose, and the like. Compared with traditional denitrification rate determination methods, the application of this method can achieve rapid in-situ determination of the denitrification rate of water bodies. It can implement in-situ water extraction, in-situ purge, in-situ cultivation, and in-situ determination. It ensures that various environmental factors in the water denitrification process remain unchanged as much as possible, restores the actual water denitrification process, and ensures that the measurement results most accurately reflect the denitrification potential of the water body. The determination process does not affect the nitrogen cycle process in the natural environment, and no chemicals harmful to the environment and human body are added. The method is suitable for denitrification potential research of various types of water bodies, can achieve long-term monitoring, is simple to operate, is low in cost, and does not harm human health or the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of river and lake ecological restoration, and in particular to a device and method for quickly determining the denitrification rate of a water body in situ. Background Art

[0002] Eutrophication of water bodies is the biggest challenge facing the ecological restoration of rivers and lakes. How to efficiently remove nitrogen and phosphorus has become a hot topic of concern. Denitrification is of great significance in ecological restoration. Through effective denitrification measures, we can prevent eutrophication of water bodies, protect groundwater resources, restore wetland ecosystems, improve soil quality, and reduce greenhouse gas emissions. These measures not only help maintain the health and stability of the ecological environment, but also have important significance for human quality of life and sustainable development. With the development of science and technology, more and more physical, chemical, and biological denitrification methods have been discovered and applied. How to select more efficient denitrification methods and study the nitrogen cycle process in various ecosystems on the earth requires monitoring of the denitrification rate. Currently, there are two mainstream methods for determining the denitrification rate: acetylene inhibition method and isotope labeling method.

[0003] The main disadvantages of the acetylene inhibition method are as follows: ① Acetylene interferes with other biological processes. Acetylene not only inhibits the activity of nitrous oxide reductase, but may also inhibit other microbial processes related to the nitrogen cycle, such as nitrification. This interference will affect the accuracy of the experimental results. ② The acetylene inhibition method changes the nitrogen cycle process in the natural environment through artificial intervention, making it difficult for the measurement results to reflect the denitrification rate under natural conditions. ③ The acetylene inhibition method is mainly suitable for environments with high denitrification rates. For environments with low denitrification rates, the inhibitory effect of acetylene is not obvious and the measurement accuracy is low. ④ The acetylene inhibition method is usually used for short-term measurements and has limited effect on long-term monitoring and evaluation of changing trends in denitrification rates.

[0004] Isotope labeling is the currently recognized method for determining denitrification rate, but it also has the following disadvantages:

[0005] ① The cost is high. Isotopes are expensive and the isotope labeling method requires high-precision analytical equipment, which is expensive and has high maintenance costs. ② The technology is complex. Isotope labeling experiments require precise design and control, including the amount of isotope added, time, and environmental conditions, which increases the complexity of the experiment. In addition, the isotope labeling method requires complex pre-treatment and post-treatment of samples, including extraction, purification, and detection, which requires high operating technology and laboratory conditions. ③ There is a radiation risk when using radioactive isotopes, and strict safety measures and management are required to prevent radiation contamination and human health hazards. ④ The uptake, metabolism, and release processes of organisms may interfere with the isotope labeling results, and the influence of biological factors needs to be considered in detail.

[0006] Both the acetylene suppression method and the isotope labeling method are limited by various conditions and cannot achieve in-situ rapid determination of the denitrification rate. The samples can only be brought back to the laboratory for experimental measurement, which takes a long time, especially the isotope labeling method. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing denitrification rate determination method is limited by various conditions and cannot achieve in-situ rapid determination of the denitrification rate.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: an in-situ rapid determination device for the denitrification rate of a water body, including a purge device, a flexible water bag, a helium cylinder, a water vapor separation device and a mass spectrometer. The purge device is connected to the water body to be measured through the input end of a water pump. A pressure tank is provided in the purge device. The connecting water pipe between the water pump and the pressure tank is connected to an air pipe. An air outlet is provided at the top of the pressure tank, and the water outlet at the bottom is connected to the flexible water bag through a pipe. The flexible water bag is also connected to the water vapor separation device, and the water vapor separation device is connected to the helium cylinder and the mass spectrometer.

[0009] Preferably, the purging device includes the spirally arranged connecting water pipe, the air pipe is connected to the helium cylinder, the output end of the air pipe is connected to the aeration head, the aeration head is fixed to the water inlet end of the connecting water pipe, and the water outlet end of the connecting water pipe is connected to the water inlet in the middle of the pressure tank.

[0010] Preferably, the aeration head is an aeration stone.

[0011] Preferably, a pressure gauge is provided on the top of the pressure tank.

[0012] Preferably, a control valve is installed on the pipe of the water outlet, and the movable end of the pipe of the water outlet is connected to the water bag tube on the top of the flexible water bag, and the water bag tube is connected to a three-way valve, and the water bag tube is connected to the water-gas separation device through the three-way valve.

[0013] Preferably, the water-gas separation device includes a peristaltic pump, a support column, a plastic hose, a water-gas exchange tube and a water-gas separation cylinder. The input end of the peristaltic pump is connected to the three-way valve, the output end of the peristaltic pump is connected to the plastic hose through a pipe, the plastic hose is wrapped around the support column, the water inlet end of the plastic hose is connected to the water-gas exchange tube, and the water outlet end is connected to the water-gas separation cylinder. The output end of the helium bottle is connected to the bottom of the water-gas exchange tube through a pipe, and the mass spectrometer is connected to the top of the water-gas separation cylinder through a pipe.

[0014] Preferably, a pressure reducing valve is installed on the output end pipe of the helium cylinder.

[0015] Preferably, the flexible water bag is arranged in the water body to be tested.

[0016] A method for using a device for rapid in-situ determination of water denitrification rate comprises the following steps:

[0017] Step 1: Take water in situ and purge it. The water to be tested taken in situ is pumped into the purge device through a water pump. After the reading of the pressure gauge on the pressure tank reaches 0.1 atmospheres, open the pressure reducing valve on the helium cylinder and deliver helium to the purge device through the aeration head. At the same time, by controlling the control valve on the water outlet of the pressure tank and the air outlet on the pressure tank, the value on the pressure gauge is maintained at about 0.1 atmospheres. Connect the water outlet on the pressure tank and the water inlet of the water pump through a steel hose for circulation. The purge time is controlled within 20 minutes.

[0018] Step 2: In situ culture: vacuum the flexible water bag first, then add the purged water into the flexible water bag, fill each water bag with three liters, then expel the air in the flexible water bag, and then place the flexible water bag in the in situ water body for culture;

[0019] Step 3: Initial value determination: Connect the flexible water bag to the water vapor separation device, which is then connected to the helium cylinder. The nitrogen in the water is replaced by helium through the water vapor separation device. The discharged gas is connected to the mass spectrometer. After the data stabilizes after five minutes of measurement, the nitrogen value is measured by the mass spectrometer and converted to the nitrogen value obtained by the calibration line of the water vapor separation device, which is recorded as the initial value N1.

[0020] Step 4: Calculation of denitrification rate: After placing the water bag for six hours, connect it to the water vapor separation device again and connect it to the mass spectrometer to measure the nitrogen value in the water bag at this time. The final value of nitrogen N2 is obtained by conversion through the marking line. The denitrification rate can be obtained by subtracting the initial value from the final value and dividing it by the time.

[0021] The present invention provides an in-situ rapid determination device and method for the denitrification rate of a water body. Compared with traditional denitrification rate determination methods, the method can realize in-situ rapid determination of the denitrification rate of a water body, and can realize in-situ water extraction, in-situ purge, in-situ cultivation, and in-situ determination. It can ensure that various environmental factors in the denitrification process of the water body do not change as much as possible, restore the real denitrification process of the water body, make the measurement results most realistically reflect the denitrification potential of the water body, and the nitrogen cycle process in the natural environment is not affected during the determination process. No agents harmful to the environment and human body are added. The method is suitable for the denitrification potential research of various types of water bodies, can realize long-term monitoring, is simple to operate, has low cost, and is harmless to human health and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the accompanying drawings and examples:

[0023] Figure 1 Schematic diagram of the structure of an embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the water-gas separation device in an embodiment of the present invention.

[0025] Figure 3 Schematic diagram of the structure of the purge device in an embodiment of the present invention.

[0026] Figure 4 Schematic diagram of the structure of the water bag in an embodiment of the present invention.

[0027] Figure 5 Flowchart of the present invention.

[0028] Figure 6 It is a comparison diagram of the method of the present invention and the acetylene suppression method.

[0029] Figure 7 It is a correlation analysis diagram between the method of the present invention and the acetylene suppression method.

[0030] In the figure: 1. Purge device; 1-1. Water pump; 1-2. Connecting water pipe; 1-3. Air pipe; 1-4. Aeration head; 1-5. Pressure tank; 1-5-1. Water inlet; 1-5-2. Water outlet; 1-5-3. Control valve; 1-5-4. Pressure gauge; 1-5-5. Air outlet; 2. Flexible water bag; 2-1. Water bag tube; 2-2. Three-way valve; 3. Helium cylinder; 3-1. Pressure reducing valve; 4. Water-gas separation device; 4-1. Peristaltic pump; 4-2. Support column; 4-3. Plastic hose; 4-4. Water-gas exchange cylinder; 4-5. Water-gas separation cylinder; 5. Mass spectrometer. DETAILED DESCRIPTION

[0031] like Figure 1-4 A rapid in-situ determination device for water denitrification rate includes 1 purge device, 2 flexible water bags, 3 helium cylinders, 4 water vapor separation devices, 5 mass spectrometers.

[0032] The purging device 1 consists of a water pump 1-1, a connecting water pipe 1-2, an air pipe 1-3, an aeration head 1-4, and a pressure tank 1-5. The lift of the water pump 1-1 is 50 meters. The connecting water pipe 1-2 is a rubber hose containing steel wire. One end of the connecting water pipe 1-2 is connected to the water pump 1-1, and the other end is connected to the pressure tank 1-5. A section of air pipe 1-3 is connected to the water outlet of the water pump 1-1, and the air pipe 1-3 is connected to an aeration head. The aeration head 1-3 is made of air stone and is covered with 0.5 mm air holes inside. The other end of the air pipe 1-3 is connected to the helium cylinder 3. The pressure tank 1-5 is made of stainless steel and includes a water inlet 1-5-1 connected to the connecting water pipe 1-1, a water outlet 1-5-2 connected to a control valve 1-5-3 through the connecting water pipe 1-2, and a pressure gauge 1-5-4 and an air outlet 1-5-5 are installed on the top of the pressure tank 1-5. The air outlet 1-5-5 is connected to a section of air pipe and a control valve.

[0033] The flexible water bag 2 is made of PE material and has a capacity of 5 liters. The water bag cover is connected to a water pipe 2-1, and the other end of the water pipe is connected to a three-way valve 2-2.

[0034] The helium cylinder 3 contains 40 liters of pure helium and is connected to a pressure reducing valve 3-1.

[0035] The water vapor separation device 4 comprises a peristaltic pump 4-1, a support column 4-2, a PVC plastic hose 4-3, a water-gas exchange cylinder 4-4, and a water-gas separation cylinder 4-5. Peristaltic pump 4-1 has a maximum speed of 500 rpm, and its water inlet and outlet are connected to a PVC plastic hose 4-3 with an inner diameter of 6 mm. Support column 4-2 is made of a PE rigid cylinder with an inner diameter of 0.15 m, a height of 0.3 m, and a thickness of 5 mm. Water-gas exchange cylinder 4-4 consists of a barrel 4-4-1 and a rubber stopper 4-4-2. The rubber stopper has two holes, one for the water inlet and the other for the air inlet. The barrel has a water outlet connected to the PVC plastic hose 4-3. The PVC plastic hose 4-3 is wrapped around support column 4-2 with at least ten turns. The water-gas separation cylinder 4-5 is a PE material cylinder with two holes, one hole is connected to the PVC plastic hose 4-3 wound from the support column 4-2, and the other hole is an air outlet. A water outlet is set at the bottom.

[0036] The mass spectrometer 5 is a HIDEN in-situ differential electrochemical mass spectrometer equipped with an ultra-low flow OEMS injection system, with an injection rate as low as 250ul / min, a fast scanning speed of 650 measurements / second for transient analysis, and automatic spectrum analysis provides peak recognition and component analysis, with quantitative data output in PPM, PPB or %. It is an advanced online electrochemical research method developed by combining traditional electrochemical methods with modern gas phase mass spectrometry analysis technology.

[0037] The peristaltic pump 4-1 is of model LHZW002-10, with an inner tube of 4.8×8BPT and an outer tube of 5×7 silica gel, and a flow rate of 0.1-510 ml / min.

[0038] like Figure 5 A method for rapid in-situ determination of water denitrification potential includes:

[0039] ① In-situ water collection and purging: The water to be tested is pumped into the purging device through a water pump. After the pressure gauge on the pressure tank reaches 0.1 atmosphere, open the pressure reducing valve on the helium cylinder and deliver helium to the purging device through the aeration head. At the same time, the pressure gauge value is maintained at around 0.1 atmosphere by controlling the control valve on the pressure tank outlet and the air outlet on the pressure tank. Connect the water outlet on the pressure tank and the water inlet on the water pump with a steel hose to circulate to achieve a better purging effect and isolate the air from the air. The purging time is controlled to be around 20 minutes.

[0040] ② In situ culture: vacuum the flexible water bag first, then connect the purged water body into the flexible water bag, and fill each water bag with about three liters of water. Due to sufficient mixing during the purging process, there will still be some gas in the water bag at this time. These gases need to be extracted from the water bag to ensure that there is no gas in the water bag. Then place the water bag in the in situ water body for culture.

[0041] ③ Initial value determination: Connect the flexible water bag to the water vapor separation device, which is then connected to the helium cylinder. Use helium through the water vapor separation device to replace the nitrogen in the water body. Connect the exhausted gas to the mass spectrometer and measure for five minutes until the data stabilizes. At this time, the nitrogen value is measured by the mass spectrometer and converted using the mark of the water vapor separation device to obtain the nitrogen value, which is recorded as the initial value N1.

[0042] ④ Calculation of denitrification rate: After placing the water bag for 6 hours, connect the water vapor separation device again and connect it to the mass spectrometer to measure the nitrogen value in the water bag at this time. The final value of nitrogen N2 is obtained by conversion through the marking line. The denitrification rate can be obtained by subtracting the initial value from the final value and dividing it by the time.

[0043] Eutrophic water from a river was collected and purged in a purge device. After the purge was completed, the water was placed in eight flexible water bags, and then their initial values ​​were measured using a mass spectrometer. The water bags were then divided into four groups, and each group was incubated for a different time, namely 3, 4, 5, and 6 hours. After the incubation period, the final nitrogen value was measured using a mass spectrometer. Finally, the change in nitrogen value over time was calculated, and the results are as follows.

[0044]

[0045] As time goes by, the nitrogen value measured by this method increases significantly and cumulatively, indicating that the microorganisms in the water body are continuously carrying out a series of denitrification reactions such as nitrification, denitrification, anaerobic ammonia oxidation, etc. to generate nitrogen, resulting in a continuous increase in the dissolved nitrogen in the water bag. This is consistent with the actual situation, which shows that the new method can indeed measure the denitrification reaction process of the water body.

[0046] 2. Comparison experiment using the new method to measure denitrification rate with the traditional acetylene inhibition method: Four 350ml bottles of water were collected from the surface, middle, and bottom layers of a river in anaerobic bottles. After purging for 15 minutes, 5ml of zinc chloride was added to one of the bottles to terminate the reaction as a blank control. 10ml of acetylene solution was added to the other three bottles as parallel controls. After six hours of reaction, zinc chloride solution was added to terminate the reaction and the gas was collected. The nitrous oxide value was measured using a gas chromatograph, and the denitrification rate was calculated. Simultaneously, the denitrification rate was measured using the new method for each layer of water. First, the water was purged in a GCR device for 20 minutes, then the standard gas was measured using a mass spectrometer, and the initial value of the water bag was measured. After 8 hours of incubation, the final value was measured, and the denitrification rate was calculated and compared.

[0047] like Figure 6 、 Figure 7 shown.

[0048] The results show that the new method produces higher results than the acetylene inhibition method. This is because the acetylene inhibition method only measures the denitrification rate of denitrification, while the new method measures a series of denitrification processes, including nitrification and denitrification, anaerobic ammonium oxidation, and iron-ammonia oxidation. Therefore, the new method provides higher values ​​and better reflects the denitrification potential of the water body. Furthermore, the new method has a high correlation with the acetylene inhibition method, and the new method can also be used to directly convert the correlation coefficient to obtain the denitrification rate of the water body denitrification reaction. This proves that the new method is feasible for measuring water body denitrification rates. Furthermore, compared with the acetylene inhibition method, the new method can quickly monitor in situ, is simpler and more convenient to operate, and is more cost-effective.

Claims

1. A device for rapid in-situ determination of water denitrification rate, characterized by: The invention comprises a purge device (1), a flexible water bag (2), a helium bottle (3), a water-gas separation device (4) and a mass spectrometer (5), wherein the purge device (1) is connected to a water body to be tested via an input end of a water pump (1-1), a pressure tank (1-5) is provided in the purge device (1), a water pipe (1-2) connecting the water pump (1-1) and the pressure tank (1-5) is connected to an air pipe (1-3), an air outlet (1-5-5) is provided at the top end of the pressure tank (1-5), and a water outlet (1-5-2) at the bottom end is connected to the flexible water bag (2) via a pipe, the flexible water bag (2) is further connected to the water-gas separation device (4), and the water-gas separation device (4) is connected to the helium bottle (3) and the mass spectrometer (5); A control valve (1-5-3) is installed on the pipe of the water outlet (1-5-2); the movable end of the pipe of the water outlet (1-5-2) is connected to the water bag pipe (2-1) provided on the top of the flexible water bag (2); the water bag pipe (2-1) is connected to a three-way valve (2-2); the water bag pipe (2-1) is connected to the water-gas separation device (4) via the three-way valve (2-2); The water-gas separation device (4) comprises a peristaltic pump (4-1), a support column (4-2), a plastic hose (4-3), a water-gas exchange tube (4-4) and a water-gas separation cylinder (4-5); the input end of the peristaltic pump (4-1) is connected to the three-way valve (2-2); the output end of the peristaltic pump (4-1) is connected to the plastic hose (4-3) via a pipeline; the plastic hose (4-3) is wound around the support column (4-2); the water inlet end of the plastic hose (4-3) is connected to the water-gas exchange tube (4-4); the water outlet end is connected to the water-gas separation cylinder (4-5); the output end of the helium bottle (3) is connected to the bottom of the water-gas exchange tube (4-4) via a pipeline; and the mass spectrometer (5) is connected to the top of the water-gas separation cylinder (4-5) via a pipeline. The flexible water bag (2) is arranged in the water body to be tested.

2. The device for rapid in-situ determination of water denitrification rate according to claim 1, characterized in that: The purging device (1) comprises the spirally arranged connecting water pipe (1-2), the air pipe (1-3) is connected to the helium cylinder (4), the output end of the air pipe (1-3) is connected to the aeration head (1-4), the aeration head (1-4) is fixed to the water inlet end of the connecting water pipe (1-2), and the water outlet end of the connecting water pipe (1-2) is connected to the water inlet (1-5-1) in the middle of the pressure tank (1-5).

3. The device for rapidly measuring the denitrification rate of a water body according to claim 2, wherein: The aeration heads (1-4) are aeration stones.

4. The device for rapidly measuring the denitrification rate of a water body according to claim 1, wherein: A pressure gauge (1-5-4) is provided on the top of the pressure tank (1-5-1).

5. The device for rapid in-situ determination of water denitrification rate according to claim 1, characterized in that: A pressure reducing valve (3-1) is installed on the output end pipeline of the helium cylinder (3).

6. The method for using the device for rapid in-situ determination of water denitrification rate according to claim 1, wherein: The steps include: Step 1: Take water in situ and purge it. The water to be tested taken in situ is pumped into the purge device (1) through the water pump (1-1). After the reading of the pressure gauge (1-5-4) on the pressure tank (1-5) reaches 0.1 atmospheres, the pressure reducing valve (3-1) on the helium cylinder (3) is opened to transport the helium into the purge device (1) through the aeration head (1-4). At the same time, the value on the pressure gauge (1-5-4) is maintained at about 0.1 atmospheres by controlling the control valve (1-5-3) on the water outlet (1-5-2) of the pressure tank (1-5) and the air outlet (1-5-5) on the pressure tank (1-5). The water outlet (1-5-2) on the pressure tank (1-5) and the water inlet of the water pump (1-1) are connected through a steel hose for circulation. The purge time is controlled within 20 minutes. Step 2: In situ culture, the flexible water bag (2) is first vacuumed, and then the purged water body is connected to the flexible water bag (2), and each water bag is filled with three liters. The air in the flexible water bag (2) is then exhausted, and then the flexible water bag (2) is placed in the in situ water body for culture; Step 3: Determine the initial value. Connect the flexible water bag (2) to the water vapor separation device (4), which is connected to the helium cylinder (3). Use helium to replace nitrogen in the water body through the water vapor separation device (4). Connect the discharged gas to the mass spectrometer (5). After measuring for five minutes and the data is stable, the value of nitrogen is measured by the mass spectrometer (5). The nitrogen value is converted by the mark line of the water vapor separation device (4) and recorded as the initial value N1. Step 4: Calculation of the denitrification rate: After the water bag (2) is placed for six hours, it is connected to the water vapor separation device again and connected to the mass spectrometer (5) to measure the nitrogen value in the water bag (2) at this time. The final value of nitrogen N2 is obtained by conversion through the marking line. The denitrification rate can be obtained by subtracting the initial value from the final value and dividing it by the time.

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