Method for measuring radon-220 concentration and radium-224 concentration in water by bubbling method

Abstract

A method for measuring the concentration of radon 220 and radium-224 in water through a bubbling method comprises the steps that based on a bubbling measuring device, water on the surface layer of the water surface is sampled and put into a sample bottle, a pump of an RAD7 radon measuring instrument is started, the radon 220 contained in a water sample is put into the RAD7 radon measuring instrument and tends to be stable, the concentration of the radon 220 coming out of bubbling of the water sample measuring bottle and the concentration of the radon 220 in the water in the water sample measuring bottle are balanced, and the concentration of the radon 220 contained in the water sample measuring bottle is calculated. And recording a concentration curve of the radon-220 in the gas measured by the RAD7 radon measuring instrument from the starting state to the equilibrium state. The concentration of the radon 220 in the water is determined through a bubbling method, relevant expressions of the concentration of the radon 220 in all positions of different spaces of the device are established, and the expressions are substituted into the expressions to solve the concentration of the radon 220 and the concentration of the radium-224 in the water. The measurement method is used for calculating the concentration of the radon 220 and the concentration of the radium-224 in the water, the calculation process is simple, the calculation result is accurate, the concentration of the radon 220 and the concentration of the radium-224 in the water sample can be continuously monitored and analyzed for a long time, a basis is provided for knowing regional water source quality, water pollution control, agriculture and animal husbandry water and the like, and the method is suitable for popularization and application. The underground water environment and resident drinking water safety are ensured.

Description

Technical Field

[0001] The present invention relates to a nuclear radiation detection technology, in particular to a method for measuring the concentration of radon-220 and radium-224 in water by the bubbling method. Background Art

[0002] Radon-220 is a natural radioactive gas that usually exists in soil and water bodies and enters the air through the exhalation on the water surface. The concentration of radon-220 plays an important role in environmental monitoring and water quality assessment, especially in the detection of groundwater and drinking water safety. Therefore, accurately measuring the concentration of radon-220 in water and the exhalation rate of radon-220 on the water surface is of great significance for water environment protection and public health safety.

[0003] The monitoring and research related to radon-220 are inseparable from the calculation of the concentration of radium-224. Radium-224 is the parent nuclide of radon-220, and the radon-220 generated by its decay is one of the main sources of radon exhaled in water bodies. Therefore, measuring and calculating the concentration of radium-224 in water bodies plays a fundamental role in understanding the radioactive equilibrium relationship in water bodies, evaluating the radiation hazards of water bodies, and developing water purification technologies.

[0004] Currently, the measurement methods for the concentration of radon-220 mainly rely on the direct sampling and detection of radon gas, such as using radon detection instruments such as RAD7 radon detectors for concentration monitoring. However, the existing measurement technologies have some deficiencies, mainly manifested as complex measurement processes, large influence of environmental factors on data accuracy, and cumbersome operations, and it takes a long time to obtain stable measurement results. These problems are particularly prominent in some long-term and continuous monitoring projects, restricting their application in water quality monitoring and water resource protection. Traditional methods mainly analyze the radon-220 content by collecting water samples or infer the concentration of radon-220 in water through indirect experimental means. However, these methods usually require a long experimental cycle and complex operations, and cannot meet the requirements of rapid response and real-time monitoring. In addition, the half-life of radon-220 is relatively short, about 55.6 seconds, making the concentration change rapidly during the measurement process, posing challenges to traditional measurements. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for measuring the concentration of radon-220 and radium-224 in water by the bubbling method.

[0006] The technical solution of the present invention is: a method for measuring the concentration of radon-220 and radium-224 in water by the bubbling method, including a measurement process and a calculation process. The measurement process is based on a bubbling measurement device, which includes a water sample measurement bottle, a bottle cap, an intake pipe sleeve, an exhaust pipe sleeve, an intake pipe, an exhaust pipe, a drying bottle, and a RAD7 radon detector. The exhaust pipe is connected to the intake end of the drying bottle through a hose, the exhaust end of the drying bottle is connected to the intake end of the RAD7 radon detector through a hose, and the exhaust end of the RAD7 radon detector is connected to the intake pipe of the water sample measurement bottle through a hose.

[0007] The specific steps of the measurement process and the calculation process are as follows: I. Measurement process Pour the surface water of the water sample to be measured into the water sample measurement bottle, and tighten the bottle cap. Set the air outlet of the intake pipe in the water sample to be measured and close to the bottom of the water sample measurement bottle, and the air inlet of the exhaust pipe is located above the liquid level of the water sample to be measured.

[0008] Start the pump of the RAD7 radon detector. Under the action of the pump, the radon-220-containing air in the water sample bubbles in the water sample measurement bottle, so that the air enters the drying bottle through the exhaust pipe for drying, and then enters the RAD7 radon detector. Record the concentration value of the RAD7 radon detector at this time; assuming that the gas concentration in the water sample is uniform, when the reading of the RAD7 radon detector tends to be stable, the concentration of radon-220 in the bubbles coming out of the water sample measurement bottle reaches equilibrium with the concentration of radon-220 in the water of the water sample measurement bottle. Record the concentration curve of radon-220 in the gas measured by the RAD7 radon detector from startup to the equilibrium state.

[0009] II. Calculation process Let the concentration of radon-220 in the water of the water sample measurement bottle be c 1 (t) The concentration of radon-220 in the gas of the water sample measurement bottle is c 2 (t) The concentration of radon-220 in the gas path from the air outlet of the water sample measurement bottle to the air inlet of the RAD7 radon detector is c 3 (t) The concentration of radon-220 in the internal measurement cavity of the RAD7 radon detector is c 4 (t) The concentration of radon-220 in the gas path from the air outlet of the RAD7 radon detector to the air inlet of the water sample measurement bottle is c 5 (t) When performing bubbling measurement under the action of the pump, the concentration of radon-220 in the water of the water sample measurement bottle 1 is c 1 (t) The calculation expression for changing with time is as follows: (1) Wherein, c Ra-224 represents the concentration of radium-224 in water, with the unit of Bq / m 3 ; λ Rn-220 represents the decay constant of radon-220, with the unit of s -1 ; L represents the 8-pump flow rate of the RAD7 radon detector, with the unit of L / min; V 1 represents the volume of the surface water of the water sample to be measured, with the unit of m 3 ; X represents the ratio of gaseous radon-220 to radon-220 in water at equilibrium, and this value is obtained through formula calculation or experimental measurement.

[0010] When the concentration of radon-220 in water in the water sample measurement bottle reaches equilibrium with gaseous radon-220, there is the following expression: (2) Substitute into formula (1) and solve to obtain the following expression: (3) Meanwhile, the concentration of gaseous radon-220 in the water sample measurement bottle is calculated by the following expression: (4) Wherein, V 2 represents the volume of the surface water of the water sample to be measured, with the unit of m 3 .

[0011] When the concentration of radon-220 in water in the water sample measurement bottle reaches equilibrium with gaseous radon-220, solving formula (4) gives the following expression: (5) After the concentration of gaseous radon-220 in the water sample measurement bottle reaches equilibrium with the concentration in the internal chamber of the RAD7 radon detector, the concentration of radon-220 in the internal chamber of the RAD7 radon detector is not the actual concentration of radon-220 in the sample bottle due to the natural decay during the gas path circulation time. Therefore, when calculating the concentration of gaseous radon-220 in the water sample measurement bottle, it is necessary to correct the concentration of radon-220 measured by the RAD7 radon detector using the correction factor of the radon-220 detection efficiency. Thus, the expression for the actual concentration of gaseous radon-220 is as follows: (6) Wherein, CF 1 represents the calibration factor of the RAD7 radon detector; CF 2Represents the correction factor for radon-220 detection efficiency; c Rn-220 Represents the reading of radon-220 concentration in the RAD7 radon detector, with the unit of Bq / m 3 ; V 3 Represents the volume of the gas path from the gas outlet of the water sample measurement bottle to the gas inlet of the RAD7 radon detector, with the unit of m 3 ; V 4 Represents the volume of the internal chamber of the RAD7 radon detector, with the unit of m 3 .

[0012] Substitute the result obtained from formula (6) into formula (5) to calculate the radon-220 concentration in the water of the water sample measurement bottle.

[0013] According to the RAD7 radon detector manual, the actual concentration reading of the RAD7 radon detector is twice the actual concentration in the internal chamber. Therefore, the actual Rn-220 concentration in the RAD7 internal chamber is: (7) At the same time, the calculation expression for the radon-220 concentration at the gas inlet of the water sample measurement bottle is obtained as: (8) Among them, V5 represents the volume of the gas path from the gas outlet of the RAD7 radon detector to the gas inlet of the water sample measurement bottle, with the unit of m 3 .

[0014] When V5 is very small, formula (8) is simplified to: (9) Substitute the radon-220 concentration C1(t) in the water of the water sample measurement bottle 1 calculated by formula (5) and the radon-220 concentration C5(t) at the gas inlet of the water sample measurement bottle calculated by formula (9) into formula (3), and the concentration value of radium-226 in the water can be obtained.

[0015] The present invention has the following advantages compared with the prior art: 1. The device for measuring radon-220 concentration and radium-224 concentration in water by the bubbling method provided by the present invention has a simple structure, is easy to operate, has a short measurement time, and is suitable for long-term and continuous monitoring under complex environmental conditions.

[0016] 2. Calculating the radon-220 concentration and radium-224 concentration in water through the measurement method provided by the present invention has a simple calculation process and accurate calculation results, and can conduct long-term and continuous monitoring and analysis of the radon-220 concentration and radium-224 concentration in groundwater samples in a certain area.

[0017] The following further describes the detailed structure of the present invention in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the device for measuring the concentration of radon-220 and radium-224 in water according to the present invention. Specific Embodiments

[0019] Example 1. As Figure 1 shown, the method for measuring the concentration of radon-220 and radium-224 in water by the bubbling method includes a measurement process and a calculation process. The measurement process is based on an existing bubbling measurement device, which includes a water sample measurement bottle 1, a bottle cap 2, an inlet pipe sleeve 3, an outlet pipe sleeve 4, an inlet pipe 5, an outlet pipe 6, a drying bottle 7, and a RAD7 radon detector 8. A substance for drying gas, such as calcium chloride powder, etc., is placed in the drying bottle 7. The inlet pipe sleeve 3 and the outlet pipe sleeve 4 are respectively installed on the bottle cap 2. The inlet pipe 5 is inserted into the inlet pipe sleeve 3, and the outlet pipe 6 is inserted into the outlet pipe sleeve 4. The outlet pipe 6 is connected to the inlet end of the drying bottle 7 through a hose. The outlet end of the drying bottle 7 is connected to the inlet end of the RAD7 radon detector 8 through a hose. The outlet end of the RAD7 radon detector 8 is connected to the inlet pipe 5 of the water sample measurement bottle 1 through a hose.

[0020] The measurement process and the calculation process specifically include the following steps: I. Measurement Process Pour the surface water of the water sample to be measured into the water sample measurement bottle 1, and tighten the bottle cap 2. Set the outlet of the inlet pipe 5 in the water sample to be measured and close to the bottom of the water sample measurement bottle 1, and the inlet of the outlet pipe 6 is located above the liquid level of the water sample to be measured.

[0021] Start the pump of the RAD7 radon detector 8. Under the action of the pump, the air containing radon-220 in the water sample bubbles in the water sample measurement bottle 1, so that the air enters the drying bottle 7 through the outlet pipe 6 for drying, and then enters the RAD7 radon detector 8. Record the concentration value of the RAD7 radon detector 8 at this time. Assuming that the gas concentration in the water sample is uniform, when the reading of the RAD7 radon detector 8 tends to be stable, the concentration of radon-220 in the bubbles coming out of the water sample measurement bottle 1 reaches equilibrium with the concentration of radon-220 in the water of the water sample measurement bottle 1. Record the concentration curve of radon-220 in the gas measured by the RAD7 radon detector 8 from startup to the equilibrium state.

[0022] II. Calculation Process Let the concentration of radon-220 in the water of the water sample measurement bottle 1 be c 1 (t) , and the concentration of radon-220 in the gas of the water sample measurement bottle 1 be c 2 (t), when performing bubbling measurement under the action of a pump, the radon-220 concentration in the water of the water sample measurement bottle 1 is c 1 (t) The calculation expression varying with time is as follows: (1) Where, c 1 (t) is the radon-220 concentration in the water of the water sample measurement bottle 1, with the unit of Bq / m 3 ; c 2 (t) is the radon-220 concentration in the gas of the water sample measurement bottle 1, with the unit of Bq / m 3 ; λ Rn-220 represents the radon-220 decay constant, with the unit of s -1 ; L represents the pump flow rate of the RAD7 radon detector 8, with the unit of L / min; V 2 represents the gas volume in the water sample measurement bottle 1, with the unit of m 3 ; X represents the ratio of gaseous radon-220 to radon-220 in water at equilibrium, and this value is obtained through formula calculation or experimental measurement.

[0023] When the radon-220 concentration in the water of the water sample measurement bottle 1 reaches equilibrium with the gaseous radon-220, there is the following expression: (2) Substitute into formula (1) and solve to obtain the following expression: (3) After the radon-220 concentration in the gas inside the water sample measurement bottle 1 reaches equilibrium with the concentration inside the internal chamber of the RAD7 radon detector 6, the radon-220 concentration in the internal chamber of the RAD7 radon detector 6 is not the actual radon-220 concentration in the sample bottle due to the natural decay during the gas path circulation time. Therefore, when calculating the radon-220 concentration in the gas of the water sample measurement bottle 1, it is necessary to correct the radon-220 concentration measured by the RAD7 radon detector 6 using the correction factor of the radon-220 detection efficiency. Thus, the expression for the actual concentration of gaseous radon-220 is as follows: (6) Where, CF 1 represents the calibration factor of the RAD7 radon detector 6; CF 2 represents the correction factor of the radon-220 detection efficiency; c Rn-220Indicates the reading of the radon-220 concentration in the RAD7 radon detector 6, with the unit of Bq / m 3 ; V 3 Indicates the volume of the gas path from the gas outlet of the water sample measurement bottle 1 to the gas inlet of the RAD7 radon detector 6, with the unit of m 3 ; V 4 Indicates the volume of the internal chamber of the RAD7 radon detector 6, with the unit of m 3 。

[0024] Substitute the result obtained from formula (6) into formula (5) to calculate the radon-220 concentration in the water in the water sample measurement bottle 1.

[0025] According to the RAD7 radon detector 6 manual, the actual concentration reading of the RAD7 radon detector 6 is twice the actual concentration in the internal chamber. Therefore, the actual Rn-220 concentration in the RAD7 internal chamber is: (7) At the same time, the calculation expression for the radon-220 concentration at the gas inlet of the water sample measurement bottle 1 is obtained as: (8) Where, V5 indicates the volume of the gas path from the gas outlet of the RAD7 radon detector 6 to the gas inlet of the water sample measurement bottle 1, with the unit of m 3 。

[0026] When V5 is very small, formula (8) is simplified to: (9) Substitute the radon-220 concentration in the water in the water sample measurement bottle 1 c 1(t) calculated by formula (5) and the radon-220 concentration c 5(t) at the gas inlet of the water sample measurement bottle 1 calculated by formula (9) into formula (3), and the concentration value of radium-226 in the water can be obtained.

Claims

1. A method for measuring the concentration of radon-220 and radium-224 in water by the bubbling method, characterized in that: It includes a measurement process and a calculation process. The measurement process is based on a bubbling measurement device, which includes a water sample measurement bottle, a bottle cap, an air inlet pipe sleeve, an air outlet pipe sleeve, an air inlet pipe, an air outlet pipe, a drying bottle, and a RAD7 radon detector. The air outlet pipe is connected to the air inlet end of the drying bottle through a hose, the air outlet end of the drying bottle is connected to the air inlet end of the RAD7 radon detector through a hose, and the air outlet end of the RAD7 radon detector is connected to the air inlet pipe of the water sample measurement bottle through a hose; The specific steps of the above-mentioned measurement process and calculation process are as follows: I. Measurement process Pour the surface water of the water sample to be measured into the water sample measurement bottle, and tighten the bottle cap. Set the air outlet of the air inlet pipe in the water sample to be measured and close to the bottom of the water sample measurement bottle, and the air inlet of the air outlet pipe is located above the liquid level of the water sample to be measured; Start the pump of the RAD7 radon detector. Under the action of the pump, the air containing radon-220 in the water sample bubbles in the water sample measurement bottle, so that the air enters the drying bottle through the air outlet pipe for drying, and then enters the RAD7 radon detector, and record the concentration value of the RAD7 radon detector at this time; Assuming that the gas concentration in the water sample is uniform, when the reading of the RAD7 radon detector tends to be stable, the concentration of radon-220 in the bubbles coming out of the water sample measurement bottle reaches equilibrium with the concentration of radon-220 in the water of the water sample measurement bottle, and record the concentration curve of radon-220 in the gas measured by the RAD7 radon detector from startup to the equilibrium state; II. Calculation process Let the radon-220 concentration in the water of the water sample measuring bottle be c 1 (t) , and the radon-220 concentration in the gas of the water sample measuring bottle be c 2 (t) , the radon-220 concentration in the gas path from the outlet of the water sample measuring bottle to the inlet of the RAD7 radon detector be c 3 (t) , the radon-220 concentration in the internal measurement cavity of the RAD7 radon detector be c 4 (t) , the radon-220 concentration in the gas path from the outlet of the RAD7 radon detector to the inlet of the water sample measuring bottle be c 5 (t) , when performing bubbling measurement under the action of a pump, the calculation expression for the change of the radon-220 concentration in the water of the water sample measuring bottle 1 with time is as follows: c 1 (t) The following is: （1） Among them, c Ra-224 represents the concentration of radium-224 in water, with the unit of Bq / m 3 ; λ Rn-220 represents the decay constant of radon-220, with the unit of s -1 ; L represents the pump flow rate of the RAD7 radon detector, with the unit of L / min; V 1 represents the volume of the surface water of the water sample to be measured, with the unit of m 3 ; X represents the ratio of gaseous radon-220 to radon-220 in water at equilibrium, and this value is obtained through formula calculation or experimental measurement; When the concentration of radon-220 in the water of the water sample measurement bottle reaches equilibrium with the radon-220 in the gas, the following expression exists: （2） Substitute into formula (1) and solve to obtain the following expression: （3） At the same time, the concentration of radon-220 in the gas of the water sample measurement bottle is calculated by the following expression: （4） Among them, V 2 represents the volume of the surface water of the water sample to be measured, with the unit of m 3 ; When the concentration of radon-220 in the water of the water sample measurement bottle reaches equilibrium with the radon-220 in the gas, solving formula (4) has the following expression: （5） After the concentration of radon-220 in the gas in the water sample measurement bottle reaches equilibrium with the concentration in the internal chamber of the RAD7 radon detector, the concentration of radon-220 in the internal chamber of the RAD7 radon detector is not the actual concentration of radon-220 in the sample bottle due to the natural decay of the gas path circulation time. Therefore, when calculating the concentration of radon-220 in the gas of the water sample measurement bottle, it is necessary to use the correction factor of the radon-220 detection efficiency to correct the concentration of radon-220 measured by the RAD7 radon detector. Therefore, the expression of the actual concentration of gas radon-220 is as follows: （6） Among them, CF 1 represents the calibration factor of the RAD7 radon detector; CF 2 represents the correction factor for the radon-220 detection efficiency; c Rn-220 represents the reading of the radon-220 concentration in the RAD7 radon detector, with the unit of Bq / m 3 ; V 3 represents the volume of the gas path from the air outlet of the water sample measurement bottle to the air inlet of the RAD7 radon detector, with the unit of m 3 ; V 4 represents the volume of the internal chamber of the RAD7 radon detector, with the unit of m 3 ; Substitute the result obtained from formula (6) into formula (5) to calculate the concentration of radon-220 in the water of the water sample measurement bottle; According to the RAD7 radon detector manual, the actual concentration reading of the RAD7 radon detector is twice the actual concentration in the internal chamber. Therefore, the actual concentration of Rn-220 in the internal chamber of the RAD7 is: （7） At the same time, the calculation expression of the concentration of radon-220 at the air inlet of the water sample measurement bottle is obtained: （8） V5 represents the volume of the air path from the outlet of the RAD7 radon detector to the inlet of the water sample measuring bottle, in m 3 ; When V5 is very small, formula (8) is simplified to: （9） Substitute the concentration of radon-220 C1(t) in the water of the water sample measurement bottle 1 calculated by formula (5) and the concentration of radon-220 C5(t) at the air inlet of the water sample measurement bottle calculated by formula (9) into formula (3), and the concentration value of radium-226 in the water can be obtained.

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