Device and method for in-situ rapid determination of denitrification rate of water body

Abstract

The invention discloses a novel method for in-situ rapid determination of denitrification potential of a water body. Devices needed by the novel method comprise a purging device, a modified flexible water bag, a water vapor separation device, a mass spectrometer, a peristaltic pump, a gas flowmeter, a PVC hose and the like. Compared with the traditional denitrification rate determination method, the method can realize in-situ rapid determination of the denitrification rate of the water body, can realize in-situ water taking, in-situ purging, in-situ culture and in-situ determination, ensures that various environmental factors in the denitrification process of the water body are not changed as much as possible, restores the real denitrification process of the water body, and has a good application prospect. The measurement result truly reflects the denitrification potential of the water body, the nitrogen cycle process in the natural environment is not affected in the measurement process, no chemicals harmful to the environment and human bodies are added, the method is suitable for research on the denitrification potential of various types of water bodies, long-term monitoring can be achieved, operation is easy, cost is low, and the method is suitable for popularization and application. No harm is caused to human health and the environment.

Description

Technical Field

[0001] The invention relates to the technical field of river and lake ecological restoration, and in particular to an in-situ rapid determination device and method for water body denitrification rate. 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. At present, there are two main 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 human 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 the changing trend of the denitrification rate.

[0004] Isotope labeling is currently the mainstream method for determining denitrification rate, but it also has the following disadvantages: ① Expensive. Isotopes are expensive and isotope labeling 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 harm to human health. 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.

[0005] 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, which takes longer. Summary of the invention

[0006] 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.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: an in-situ rapid determination device for water body denitrification rate, including a purging device, a flexible water bag, a helium bottle, a water vapor separation device and a mass spectrometer. The purging device is connected to the water body to be measured through the input end of a water pump. A pressure tank is arranged in the purging device. An air pipe is connected to the connecting water pipe between the water pump and the pressure tank. An air outlet is arranged at the top of the pressure tank, and the water outlet at the bottom is connected to the flexible water bag through a pipeline. The flexible water bag is also connected to the water vapor separation device, and the water vapor separation device is connected to the helium bottle and the mass spectrometer.

[0008] 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.

[0009] Preferably, the aeration head is an aeration stone.

[0010] Preferably, a pressure gauge is provided on the top of the pressure tank.

[0011] 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 provided 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.

[0012] Preferably, the water vapor separation device includes a peristaltic pump, a support column, a plastic hose, a water vapor exchange tube and a water vapor 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 vapor exchange tube, the water outlet end is connected to the water vapor separation cylinder, the output end of the helium bottle is connected to the bottom of the water vapor exchange tube through a pipe, and the mass spectrometer is connected to the top of the water vapor separation cylinder through a pipe.

[0013] Preferably, a pressure reducing valve is installed on the output end pipeline of the helium cylinder.

[0014] Preferably, the flexible water bag is arranged in the water body to be tested.

[0015] A method for using a device for rapid in-situ determination of water body denitrification rate comprises the following steps: Step 1: Take water in situ and purge. 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 atmosphere, open the pressure reducing valve on the helium cylinder, and deliver the 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 atmosphere. The water outlet on the pressure tank and the water inlet of the water pump are connected through a steel wire hose for circulation. The purge time is controlled within 20 minutes. Step 2: In situ culture, the flexible water bag is first vacuumed, and then the purged water body is connected to the flexible water bag, each water bag is filled with three liters, and then the air in the flexible water bag is discharged, and then the flexible water bag is placed in the in situ water body for culture; Step 3: Initial value determination: connect the flexible water bag to the water vapor separation device, connect the water vapor separation device to the helium cylinder, replace the nitrogen in the water body with helium through the water vapor separation device, connect the exhausted gas to the mass spectrometer, measure for five minutes until the data is stable, then measure the nitrogen value through the mass spectrometer, and convert it through the mark line of the water vapor separation device to obtain the nitrogen value recorded as the initial value N1; 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.

[0016] The present invention provides an in-situ rapid determination device and method for water body denitrification rate. Compared with the traditional denitrification rate determination method, the method can realize in-situ rapid determination of the denitrification rate of the water body, can realize in-situ water extraction, in-situ purge, in-situ cultivation and in-situ determination, and can ensure that various environmental factors in the water body denitrification process do not change as much as possible, restore the real water body denitrification process, make the measurement result most realistically reflect the denitrification potential of the water body, and the determination process does not affect the nitrogen cycle process in the natural environment, and does not add agents harmful to the environment and human body. It 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

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0018] Figure 2 Schematic diagram of the structure of the water-gas separation device in an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of the structure of the purge device in an embodiment of the present invention.

[0020] Figure 4 Schematic diagram of the structure of the water bag in the embodiment of the present invention.

[0021] Figure 5 It is a flow chart of the present invention.

[0022] Figure 6 It is a comparison diagram between the method of the present invention and the acetylene suppression method.

[0023] Figure 7 It is a correlation analysis diagram between the method of the present invention and the acetylene inhibition method.

[0024] 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

[0025] like Figure 1-4 A rapid in-situ determination device for water body denitrification rate includes 1 a purge device, 2 a flexible water bag, 3 a helium cylinder, 4 a water vapor separation device, 5 a mass spectrometer 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 a 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 pores 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.

[0026] The flexible water bag 2 is a PE material water bag with a capacity of 5 liters. A water pipe 2-1 is connected to the water bag cover, and a three-way valve 2-2 is connected to the other end of the water pipe.

[0027] The helium cylinder 3 contains 40 liters of pure helium and is connected to a pressure reducing valve 3-1.

[0028] The water vapor separation device 4 is composed of a peristaltic pump 4-1, a support column 4-2, a PVC plastic hose 4-3, a water vapor exchange cylinder 4-4, and a water vapor separation cylinder 4-5. The maximum speed of the peristaltic pump 4-1 is 500r / min, and the water inlet and outlet are connected to the PVC plastic hose 4-3, the inner diameter of the PVC plastic hose 4-3 is 6mm, the support column 4-2 is made of a PE hard cylinder, the inner diameter is 0.15m, the height is 0.3m, and the thickness is 5mm. The water vapor exchange cylinder 4-4 is composed of a cylinder body 4-4-1 and a rubber plug 4-4-2, and the rubber plug has two holes, one hole is a water inlet, and the other hole is an air inlet. There is a water outlet on the cylinder body connected to the PVC plastic hose 4-3, and the PVC plastic hose 4-3 is wound around the support column 4-2, and the number of windings is not less than ten. 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, and a water outlet is arranged at the bottom.

[0029] 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.

[0030] The peristaltic pump 4-1 is of model LHZW002-10, the inner tube is 4.8×8BPT, the outer tube is 5×7 silica gel, and the flow rate is 0.1-510 ml / min.

[0031] like Figure 5 A method for rapid in-situ determination of water body denitrification potential includes: ① In-situ water collection and purging: The water to be tested taken in-situ is pumped into the purging device through a water pump. When the reading of the pressure gauge on the pressure tank reaches 0.1 atmosphere, open the pressure reducing valve on the helium cylinder, and deliver the helium to the purging 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 atmosphere. The water outlet on the pressure tank and the water inlet on the water pump are connected through a steel wire hose for circulation to achieve a better purging effect and isolate the influence of air. The purging time is controlled to be about 20 minutes.

[0032] 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 pumped out of the water bag to ensure that there is no gas in the water bag, and then place the water bag in the in situ water body for culture.

[0033] ③ Initial value determination: connect the flexible water bag to the water vapor separation device, which is connected to the helium cylinder. Use helium to replace the nitrogen in the water body through the water vapor separation device. Connect the exhausted gas to the mass spectrometer. After measuring for five minutes and waiting for the data to stabilize, the value of nitrogen is measured by the mass spectrometer and converted through the mark of the water vapor separation device to obtain the nitrogen value, which is recorded as the initial value N1.

[0034] 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.

[0035] Eutrophic water from a river was collected and purged in a purge device. After the purge was completed, the water was put into eight flexible water bags, and then the initial values ​​were measured by a mass spectrometer. The water bags were then divided into four groups, and each group was cultured for a different time, namely 3, 4, 5, and 6 hours. After the culture was completed, the final nitrogen value was measured by a mass spectrometer, and finally the change in nitrogen appreciation over time was calculated. The results are as follows.

[0036]

[0037] 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 and 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.

[0038] 2. Comparison experiment of using the new method to measure the denitrification rate with the traditional method of acetylene inhibition method: Take four bottles of 350ml water from the surface, middle and bottom layers of a river in anaerobic bottles, and add 5ml zinc chloride to one of the bottles to terminate the reaction after purging for 15 minutes as a blank group, and add 10ml acetylene solution to the other three bottles as a parallel group. After six hours of reaction, add zinc chloride solution to terminate the reaction and collect the gas. Use gas chromatograph to measure the nitrous oxide value and then calculate the denitrification rate. At the same time, take water from each layer and measure the denitrification rate using the new method. First, put it into the GCR device for purging for 20 minutes, then use the mass spectrometer to measure the standard gas, and then measure the initial value of the water bag. After 8 hours of cultivation, the final value is measured, and then the denitrification rate is calculated, and the two are compared.

[0039] like Figure 6 , Figure 7 shown.

[0040] From the results, it can be seen that the new method has a higher result than the acetylene inhibition method. Since the acetylene inhibition method only measures the denitrification rate of denitrification, while the denitrification rate measured by the new method includes a series of denitrification processes such as nitrification and denitrification, anaerobic ammonia oxidation, and iron ammonia oxidation, the new method has a higher value and can better reflect the denitrification potential of the water body. At the same time, the new method has a high correlation with the acetylene inhibition method, and the new method can also be used to directly convert the denitrification rate of the water body denitrification reaction according to the correlation coefficient. Therefore, it is proved that the new method is feasible to measure the denitrification rate of water bodies. At the same time, compared with the acetylene inhibition method, the new method can be quickly monitored in situ, the operation is simpler and more convenient, and it is more cost-effective.

Claims

1. A device for rapid in-situ determination of water body denitrification rate, characterized in that: 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). 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 arranged inside the purge device (1). An air pipe (1-3) is connected to a connecting water pipe (1-2) between the water pump (1-1) and the pressure tank (1-5). An air outlet (1-5-5) is arranged at the top end of the pressure tank (1-5). The 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 also connected to the water-gas separation device (4). The water-gas separation device (4) is connected to the helium bottle (3) and the mass spectrometer (5).

2. A device for rapid in-situ determination of water body denitrification rate as claimed in claim 1, characterized in that: The purging device (1) comprises the connecting water pipe (1-2) arranged in a spiral shape, the air pipe (1-3) being connected to the helium bottle (4), the output end of the air pipe (1-3) being connected to an aeration head (1-4), the aeration head (1-4) being 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) being connected to a water inlet (1-5-1) in the middle of the pressure tank (1-5).

3. A device for rapid in-situ determination of water body denitrification rate as claimed in claim 2, characterized in that: The aeration heads (1-4) are aeration stones.

4. The in-situ rapid determination device for water body denitrification rate according to claim 1, characterized in that: A pressure gauge (1-5-4) is provided on the top of the pressure tank (1-5-1).

5. The in-situ rapid determination device for water body denitrification rate according to claim 1, characterized in that: 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 a 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).

6. A device for rapid in-situ determination of water body denitrification rate as claimed in claim 5, characterized in that: 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.

7. The in-situ rapid determination device for water body 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).

8. The in-situ rapid determination device for water body denitrification rate according to claim 1, characterized in that: The flexible water bag (2) is arranged in the water body to be tested.

9. The method for using the in-situ rapid determination device for water body denitrification rate as claimed in claim 1, characterized in that: The steps include: Step 1: In situ water collection and purging: the water body to be tested collected in situ is pumped into the purging 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 atmosphere, the pressure reducing valve (3-1) on the helium cylinder (3) is opened, and the helium is transported to the purging 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 atmosphere 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 purging time is controlled within 20 minutes; Step 2, in situ culture, first evacuate the flexible water bag (2), then connect the purged water body into the flexible water bag (2), fill each water bag with three liters, then exhaust the air in the flexible water bag (2), and then place the flexible water bag (2) in the in situ water body for culture; Step 3, initial value determination, the flexible water bag (2) is connected to the water vapor separation device (4), the water vapor separation device (4) is connected to the helium cylinder (3), the nitrogen in the water body is replaced by helium through the water vapor separation device (4), the discharged gas is connected to the mass spectrometer (5), and the measurement is carried out for five minutes until the data is stable. At this time, the value of nitrogen is measured by the mass spectrometer (5), and 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 leaving the water bag (2) for six hours, connect it to the water vapor separation device again and connect it 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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