JP2024011517A - Collecting method for suspended particle and continuous measuring device for suspended particle - Google Patents

Abstract

To provide a method and a measuring device for collecting two kinds of particle and aerosol, included in the sample air and differing in particle size and concentration, separately by required amounts.SOLUTION: A collecting method for suspended particles comprises: classifying suspended particles in air by a virtual impactor 1; separating air including coarse suspended particles of large particle size and air including fine suspended particles of small particle size from each other; sucking the air including the coarse suspended particles to collect the coarse suspended particles; and also sucking the air including the fine suspended particles through a bypass to collect the fine suspended particles at a position different from the collection position for the coarse suspended particles.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for collecting suspended particles in ambient air or indoor air, and a continuous measuring device for suspended particles.

Particles floating in the ambient air or indoor air can pose serious respiratory hazards, so environmental standards for ambient air and occupational health and environmental standards are being established by international organizations such as the WHO and each country. It is being In addition, as a measurement method for this purpose, it is recommended to remove and collect particles that are sedimentary particles with a large particle size (particle size of 10 μm or more).

For this reason, in Japan, particles with a particle size exceeding 10 μm that are collected by removing 100% of them with 10 μm (100% cut with 10 μm) are called suspended particulate matter (SPM), and in other countries, particles with a particle size of PM 10 (50% cut at 10 μm) is defined as PM ₁₀ (50% cut at 10 μm) that is 10 μm or more.

Additionally, from the results of large-scale epidemiological surveys conducted in the United States since the 1980s, it has been reported that even among _PM10 , particles with a particle size of 2.5 μm or less (2.5 μm cuts 50%) can trigger myocardial infarction. , environmental standards for PM _2.5 have been established worldwide. In Japan, standards have been set for this substance, which is called fine particulate matter. For this reason, measurement of PM _2.5 is required in addition to PM ₁₀ and SPM.

On the other hand, the Occupational Safety and Health Standards also set standards for suspended particulate matter in the air. Particles with a particle size of 4 μm or less (50% cut at 4 μm) are considered "respirable dust" that may reach the alveoli, and are required to be measured along with PM ₁₀ .

Furthermore, in the field of medical research on respiratory diseases (for example, a review can be found in Aerosol Science Technology and Applications, 2014), particles with a particle size of 5 μm or less are considered “inhalable dust” rather than particles with a particle size of 4 μm or less. It is said to be "sexual dust".

In general, many particles with a diameter of 5 μm or less reach deep into the body and some of them are deposited, and are considered to have a large impact on health. Among these, particles with a particle size of more than 1 μm and less than 5 μm are often adsorbed in the throat and trachea, and some of them reach the lungs where they are adsorbed. On the other hand, particles with a particle size of 1 μm or less behave similarly to oxygen or nitrogen gas, and once they reach the lungs, most of them are exhaled again with exhalation.

In this way, particles in the dispersed phase of aerosols in the air differ in how they are deposited in the body and their components depending on the particle size, so in order to analyze this, we analyzed particles with a particle size of over 1 μm and particles with a particle size of 1 μm or less. It is desired to develop a sampling method and device that can separate and collect the particles and continuously measure their weight.

Techniques using virtual impactors are known for classifying particles, for example, as in Patent Documents 1 and 2, but suspended particles with a particle size of more than 1 μm exist in small amounts in the atmosphere, making it difficult to analyze them. These techniques alone are not sufficient to achieve the above objectives, as large amounts of the atmosphere need to be sampled to capture a corresponding amount.

If you try to separate and collect particles contained in the same sample air in different spots, particles with a diameter of 1 μm or less have a higher concentration, so particles with a diameter of 1 μm or less will be collected in excess, and the particle size will increase. There is a problem in that suspended particles with a particle size exceeding 1 μm cannot be collected in an amount suitable for the analysis method.

Japanese Patent Application Publication No. 2016-142722 JP 2019-20372 Publication

The purpose of the present invention is to separate and collect coarse suspended particles with a particle size of more than 1 μm and fine suspended particles with a particle size of 1 μm or less contained in the same sample air in different spots, and to develop an analysis method. It is an object of the present invention to provide a method for collecting suspended particles and a continuous measuring device for suspended particles, which can collect up to an amount according to the amount of particles and continuously measure the collected mass of each particle.

The present invention classifies suspended particles in the air using a virtual impactor and divides them into air containing coarse suspended particles with large particle sizes and air containing fine suspended particles with small particle sizes,
The air containing coarse suspended particles is sucked in, and the coarse suspended particles are collected in a filter.
This method of collecting suspended particles is characterized in that air containing fine suspended particles is sucked while being bypassed, and the fine suspended particles are collected on a filter at a position different from the position where coarse suspended particles are collected.

Further, the present invention sucks air containing suspended particles and divides the suspended particles in the sucked air into air containing coarse suspended particles with a large particle size and air containing fine suspended particles with a small particle size. A virtual impactor for classification,
a bypass means that is connected to the virtual impactor and that sucks air containing fine suspended particles and bypasses it to an exhaust section;
A tape-shaped filter is provided, and air containing coarse suspended particles and air containing fine suspended particles, which have been classified by a virtual impactor, are sucked through different positions of the tape-shaped filter to produce coarse suspended particles and fine suspended particles. a collection means for successively collecting and separately at different positions of a tape-shaped filter;
detection means for successively detecting floating particles collected at different positions of the tape-shaped filter by the collection means;
A method for detecting suspended particles characterized by comprising a calculation recording means for calculating and recording coarse suspended particles in the air and fine suspended particles in the air from the output of the detection means and the integrated value of the suction air flow rate. It is a continuous measurement device.

According to the present invention, by simply suctioning two types of suspended particles with different particle sizes and concentrations in the air at the same time, two types of particles with different required amounts can be collected at different positions, and each Quantity can be measured efficiently.

According to the present invention, by adjusting the amount of air to be bypassed according to the difference in particle size and concentration of two types of suspended particles in the atmosphere, it is possible to efficiently measure the amount of each by simply sucking them at the same time. This method is highly adaptable as a method for measuring substances in the air.

1 is a cross-sectional view schematically showing the configuration of a virtual impactor 1 included in a suspended particle measuring device according to an embodiment of the present invention. 2 is a system diagram showing the configuration of a suspended particle measuring device including the virtual impactor 1 of FIG. 1. FIG. FIG. 4 is a plan view showing collection positions 3, 3'; 4, 4' of the filter 9; 3 is a graph showing an example of the results of continuous measurement of the concentration of suspended particles in indoor air for 7 days using the β-ray absorption method using the suspended particle measuring device of the present embodiment shown in FIG. 2. FIG. A classifier 52 that classifies at 5 μm and a virtual impactor 1 that classifies at 1 μm are used in the suspended particle measuring device of this embodiment shown in FIG. It is a graph showing an example of the results of continuous measurement for one day.

Embodiments of the present invention will be described below with reference to the drawings. In each figure, substantially corresponding parts are given the same reference numerals, and overlapping explanations will be omitted or simplified.

FIG. 1 is a sectional view showing the configuration of a virtual impactor 1 according to an embodiment of the present invention, and FIG. 2 is a system diagram showing the configuration of a suspended particle measuring device including the virtual impactor 1 of FIG. 1. In the method for collecting suspended particles of this embodiment, first, sample air is taken in through the sampling port 53, and particles with a particle size of 5 μm or more are removed using a classifier (impactor or cyclone) 52. A sample air containing suspended particles with a particle size of less than 5 μm is classified with the virtual impactor 1, and coarse suspended particles with a particle size of more than 1 μm (more than 1 μm and less than 5 μm, Coarse Particle; hereinafter sometimes abbreviated as “CP”) are classified. ) and air containing fine particles (hereinafter sometimes abbreviated as "FP") with a particle size of 1 μm or less, and air containing coarse suspended particles is sucked into coarse suspended particles. The particles are collected in the filter 9, and most of the air containing fine suspended particles is sucked by the bypass means 2 while being bypassed without being collected at the same position on the filter 9, and the coarse suspended particles in the filter 9 are This includes collecting fine suspended particles at a location different from the collection location.

Further, if the cutting characteristic of the virtual impactor 1 is 2.5 μm in particle size, and the cutting characteristic of the classifier 52 upstream thereof is 10 μm, coarse suspended particles can be separated into particles with a particle size of more than 2.5 μm and less than 10 μm (PM _{10-2. 5} ), it is also possible to collect fine suspended particles as particles with a particle size of 2.5 μm or less (PM _2.5 ). Therefore, the particle size of the particles can be changed by manufacturing the classifier 52 whose cutting characteristics range is more than 1 μm in particle size and less than 10 μm, and the virtual impactor 1 whose cutting characteristics range is more than 0.1 μm and less than 8 μm in particle size. It is possible to collect it by In the present invention, particles larger than the cutting characteristics of the virtual impactor 1 are referred to as coarse suspended particles, and particles smaller than the cutting characteristics are referred to as fine suspended particles.

In the embodiment according to the present invention, the virtual impactor 1 includes a nozzle section 40, an air collection section 41, and an air guide section 42, and the nozzle section 40 has a circular jet nozzle 43 having an inner diameter D0. It has a defining cylindrical portion 44 and a constricted tube portion 45 continuous to the cylindrical portion 44. The air guide part 42 has a first outlet 46 with an inner diameter D2 and a second outlet 47 with an inner diameter D3, and the second outlet 47 is defined by a collecting part 51 made of a cylindrical straight pipe. Ru.

The air collection section 41 includes a truncated conical air collection pipe section 48 and a cylindrical straight pipe section 49 coaxially connected to the air collection pipe section 48 . The air collecting pipe section 48 has an inlet 50 having an inner diameter D1, which forms the same axis as the jet nozzle 43 and is spaced apart from each other at an interval S in the axial direction. The sample air supplied to the nozzle part 40 flows into the cylindrical part 44 while increasing the flow velocity by the tube contraction part 45, and a part of the sample air ejected from the jet port 43 flows into the air collecting part 41. The main flow flows into the air guide section 42 . A part of the sample air that has flowed into the air guide section 42 flows into the channel L2 from the second outlet 47, and the remainder flows into the channel L3 from the first outlet 46.

FIG. 3 is a plan view showing the collection position of the filter. The virtual impactor 1 sucks a constant flow of air, and coarse suspended particles in the sucked air with a particle size exceeding 1 μm are classified by inertial force into micro suspended particles with a particle size of 1 μm or less, and most of the particles contained in the air at Q0 are coarse suspended particles enter the air collection section 41 and are collected at the position indicated by reference numeral 3 on the filter 9 below. On the other hand, the air containing fine suspended particles flows along the streamline, and Q2 of the Q0 fine suspended particles in the air enter the collection section 51 and are deposited at the position of reference numeral 4 of the filter 9 below. be captured. The remaining fine suspended particles in the air Q3 are discharged from the bypass without being collected by the filter 9. Q0 is confirmed by the flow rate calculated from the differential pressure between the pressure G3 inside the virtual impactor 1 and the pressure sensor G4 (which measures atmospheric pressure), and Q1 and Q2 are measured by the flow rate sensor MFM1 and flow rate sensor MFM2, respectively. be done.

To describe the dimensions of each part of the virtual impactor 1 and the air flow Q0 to Q3 as an example, D0 = φ4 mm, D1 = φ5 mm, D2 = φ12.7 mm, D3 = φ12 mm, S = 5 mm, air flow Q0 to Q3. Let Qv0 to Qv3 be the volume flow rate of air corresponding to Qv0=125L/min, Qv1=20L/min, Qv2=15L/min, Qv3=90L/min, D1/D0=1.25, S/D0= 1.25, Qv1/Qv0=0.16.

The volume flow rate is adjusted by the flow rate adjustment valve PV3 and the flow rate adjustment valve PV4 so that the volumetric flow rate becomes Qv0, the volumetric flow rate is adjusted by the flow rate adjusting valve PV1 so that the volumetric flow rate becomes Qv1, and the flow rate adjusting valve PV2 is adjusted so that the volumetric flow rate becomes Qv2. .

The introduced atmosphere passes through the nozzle section 40 and is distributed into an outer tube section (main stream) and an air collection section 41 (secondary flow). In this embodiment, the main flow is guided to the bypass means 2 provided connected to the outlet of the outer pipe section, and further flows into the bypass flow to be bypassed and the flow to the collection section 51 that collects fine suspended particles. The fine suspended particles are collected at a second position of the tape-shaped fluorine-based membrane filter (hereinafter sometimes abbreviated as "filter") 9.

Normally, in a device using a conventional virtual impactor, if there is no bypass means 2 that does not collect it in a filter, the mainstream will have a large flow rate compared to the secondary flow, so even if it is as it is, fine particles contained in the mainstream will be The amount of particle filtration increases and is greater than the filtration of coarse suspended particles.

Therefore, the filter paper in the collection section for fine suspended particles becomes clogged before the amount necessary to confirm the components of coarse suspended particles can be filtered, making it impossible to collect an appropriate amount at the same time. In particular, when a larger amount of air than usual is introduced in order to collect coarse suspended particles that have a low concentration in the air, there is a problem that the amount of fine suspended particles that are collected becomes excessive.

According to the simultaneous collection method of this embodiment, the bypass flow bypassed by the bypass means 2 adjusts the amount of collected fine suspended particles to an appropriate amount without filtering most of the fine suspended particles. be able to.

In addition, in this embodiment, the amount of air introduced into the virtual impactor 1 and the amount of the bypass flow are controlled by the respective suction pumps P1, P2, P3 and flow rate adjustment valves PV1 to PV4 provided in each flow path. By using and adjusting the amount, it is possible to finely adjust the amount of collection.

In this embodiment, the sample air sucked into the device is classified by the virtual impactor 1 into air containing fine suspended particles and air containing coarse suspended particles, and the air containing only CP is classified by the virtual impactor 1. The air passes from the nozzle section 40 through the air collection section 41 (secondary flow), is filtered at the first position 3 of the tape-shaped fluorine-based membrane filter 9, and is exhausted to the outside through the flow path L1.

The air containing FP is discharged as a main stream from the virtual impactor 1 and guided to the air guide section 42, and is sucked through the flow path L3 by the suction pump P3 and the air containing the FP through the flow path L2 by the suction pump P2. A bypass flow is bypassed without being collected by the filter 9, and a flow is distributed to the collection section 51 where fine suspended particles are collected by the filter 9.

The bypass means 2 is connected to the discharge port of the outer tube part of the virtual impactor 1, and sucks the bypassed air with a suction pump P3.The bypass means 2 is cylindrical in shape, and one end is connected to the outlet of the outer tube part of the virtual impactor 1. As shown, it is connected to the discharge port of the outer tube part of the virtual impactor 1, and the other end communicates with the suction pump P3 via the flow path L3.

At this time, it is important to balance the bypass flow and the flow to the collection section 51 by adjusting the suction amount of the suction pump P2 and the suction pump P3 so that the amount of FP collected becomes a desired value. It is. That is, when the amount of FPs in the atmosphere is very large, by adjusting the suction amount of suction pump P3 to be larger than that of suction pump P2, the amount of air containing FPs to be bypassed increases, and the amount of air containing FPs that is bypassed increases. 51 is reduced, and the amount of FP to be collected can be reduced.

The flow to the collection unit 51 that collects fine suspended particles is sucked by the suction pump P1, filtered by the second position 4 of the tape-shaped fluorine-based membrane filter 9, and passed through the flow path L2 to the outside. Exhausted.

The bypass flow is sucked by the suction pump P3 and exhausted to the outside through the bypass means 2 and the flow path L3.

In this device, regarding the air flow Q1, the suction amount of the suction pump P1 is measured using the flow rate sensor MFM1, and the air flow is passed through the flow path L1 using the flow rate adjustment valve PV1 provided in the flow path L1 and the pressure sensor G1. By adjusting the amount of air, the amount of CP collected at the first position 3 of the filter 9 can be set to a desired amount per unit time.

At the same time, regarding the air flow Q2, the suction amount of the suction pump P2 is measured using the flow rate sensor MFM2, and the flow rate adjustment valve PV2 provided in the flow path L2 and the pressure sensor G2 are used to measure the suction amount of the air passing through the flow path L2. By adjusting the amount, the amount of FP collected at the second position 4 of the filter 9 can be set to a desired amount per desired unit time. Furthermore, regarding the air flow Q0, the pressure difference is calculated using the pressure sensor G3 and the pressure sensor G4, Q0 is determined from the characteristics of the virtual impactor 1, and Q3 (Q3=Q0-Q1-Q2) is calculated. Q3 adjusts the suction amount of the suction pump P3 by using flow rate adjustment valves PV3 and PV4 provided in the flow path L3, and adjusts the flow rate of the bypass flow passing through the flow path L3.

For example, if the sample air Q0 is introduced into the virtual impactor 1 at a flow rate of 125 L (liters) per minute, then the secondary flow of air Q1 containing CP from the virtual impactor 1 is 20 L per minute, and the virtual impactor 1 Of the main flow containing FP from the main stream, the bypass flow Q3 is 90 L/min, and the flow Q2 to the collection section 51 that collects FP is 15 L/min.

When air is continuously passed through the first and second positions 3 and 4 of the filter 9, the amount of suspended particles collected on the first and second positions 3 and 4 gradually increases, and the particles Since the filter 9 becomes clogged and cannot be suctioned, the tape feed mechanism 7 moves the filter 9 a certain length C in the direction of the arrow 8 at regular intervals or when the amount of collected FP and CP exceeds a certain amount. The next collection begins.

The filter 9 is in the form of a tape and is supplied wound around the supply roll 6, and is supplied to the first position 3 and the second position 4 by a plurality of guide rollers (not shown), and is supplied to the first position 3 and the second position 4 by a plurality of guide rollers (not shown) and The tape is wound onto a take-up roller 5 through a tape feeding mechanism 7 consisting of two upper and lower rollers. The tape feeding mechanism 7 feeds the filter 9 by a certain length C in the direction of the arrow 8 when a certain period of time has elapsed or when the amount of collected FP and CP exceeds a certain amount. This moves the position 3' of the filter 9 to a new position 3 and the position 4' to a new position 4.

In this way, the amount of CP and FP collected at the first and second positions 3 and 4 of the filter 9 can be measured by combining with a known measuring means, such as a β-ray absorption method or a light reflection method. can do.

An example of measuring collected CP and FP using a combination of a β-ray absorption method and a light reflection method will be described.

The first position 3 and second position 4 of the filter 9 are irradiated with β-rays from the first β-ray source 10 and the second β-ray source 11, and the amount of transmitted β-rays is continuously transmitted to the first β-ray detector 12, respectively. , detected by the second β-ray detector 13. The detection result is input to a calculation processing unit (Central Processing Unit; CPU) 28 through the first preamplifier 21 and the second preamplifier 22.

Further, the first position 3 of the filter 9 is irradiated with white light of a constant intensity from the light source 24 via the optical fiber 25, and the reflected light is guided to the photodetector 23 via the optical fiber 26. The light is continuously detected by the photodetector 23 every minute, and the detection results are input to the arithmetic processing section 28 via the third preamplifier 27.

When air is continuously passed through the first and second positions 3 and 4 of the filter 9, the amount of suspended particles collected on the first position 3 and the second position 4 gradually increases. Since the first position 3 and the second position 4 become clogged and the suction force decreases, the tape feeding mechanism 7 moves the filter 9 by a certain length C in the direction of the arrow 8 at fixed intervals, for example, every hour. and the next measurement begins.

The regions of the first position 3 and second position 4 of the filter 9 that collect suspended particles are, for example, circular with a diameter of 11 mm.

The filter 9 is tape-shaped and is unwound from the supply roll 6, and is supplied to the first position 3 and the second position 4 by a plurality of guide rollers (not shown). The tape is then wound onto a take-up roller 5 through a tape feeding mechanism 7 consisting of two upper and lower rollers. The tape feeding mechanism 7 is configured to feed the filter 9 by a certain length C in the direction of the arrow 8 when a certain period of time has elapsed or when the amount of collected FP and CP exceeds a certain amount. This moves the position 3 of the new filter 9 to a new position 3' and the position 4 to a new position 4'.

The relationship between the detection results of the first and second β-ray detectors and the photodetector and the amount of suspended particles on the filter 9 is calculated using equation (1).

I _j = I _j-1 exp (-μ _m χ _m ) …(1)

Here, I _j is the amount of β-rays transmitted through the filter that collected suspended particles or the amount of light reflected by the filter 9 at a certain moment, and I _j-1 is the same amount one minute before. In addition, I ₀ is the amount of β-rays transmitted through a new filter before collecting suspended particles or the amount of light reflected by the same filter, μ _m is a proportionality constant, and χ _m is the amount of β-rays transmitted per unit area of the filter 9. Mass of collected suspended particles (μg/cm ² ). _μm is a value specific to the β-ray sources 10, 11 and the light source, and is determined in advance in units of cm ² /μg using a standard material. Equation (1) is transformed to obtain equation (2).

χ _m =-1/μ _m ln(I _j /I _j-1 ) …(2)

By determining the ratio of I _j and I _j-1 from equation (2), for example, the amount of suspended particles per unit area of the filter 9 collected in one minute can be calculated. (which is equal to the area of the second location 4, which for a diameter of 11 mm is about 0.95 ^cm2 ) will give you the mass of airborne particles collected one minute ago (μg/min) can be calculated.

Mass of particles collected by filter 3 from Q1: M(Q1) μg,
Mass of particles collected by filter 4 from Q2: M(Q2) μg.
Here, the mass concentration of the sample air is
Mass concentration of CP: [CP] μg/m ³ ,
Mass concentration of FP: [FP] μg/m ³ ,
Further, the integrated flow rates corresponding to Q0 to Q3 when collected for a certain period of time are written as Q _t0 to Q _t3 (m ³ ).

Here, as the characteristics of virtual impactor 1,
1. All of the CP passes through only Q1 (coarse particle side) of the virtual impactor 1 and is collected by the filter 9.
2. The FP passes through Q1 (coarse particle side) as well as Q2 (fine particle side) of the virtual impactor 1, and the mass (number) of particles collected by the filter 9 depends on the flow rate division ratio.

M(Q2)=[FP]× _Qt2 ...(3)
M (Q1) = [CP] × Q _t0 + [FP] × Q _t1 … (4)

From equations (3) and (4), the mass concentration is

[FP]=M(Q2)/( _Qt2 )...(5)
[CP]={M(Q1)-M(Q2)×(Q _t1 /Q _t2 )}/Q _t0 …(6)
It is expressed as

FIG. 4 shows the concentration of suspended particles in indoor air using a β-ray absorption method using a classifier 52 that classifies at 5 μm and a virtual impactor 1 that classifies at 1 μm in the suspended particle measuring device of the present embodiment shown in FIG. FIG. 5 is a graph showing an example of the results of continuous measurement for 7 days. FIG. 5 shows a graph in which a classifier 52 that classifies at 5 μm and a virtual impactor 1 that classifies at 1 μm are added to the suspended particle measuring device of this embodiment shown in FIG. 2 is a graph showing an example of the results of continuous measurement of the amount of trapped particles in indoor air for 7 days using the β-ray absorption method. In FIG. 4, the vertical axis shows suspended particle concentration (μg/m ³ ), and the horizontal axis shows time (days). Moreover, in FIG. 5, the vertical axis shows the amount of suspended particles collected per hour (μg), and the horizontal axis shows the time (day). From FIG. 4, it can be seen that the concentration of coarse suspended particles (particle size of more than 1 μm and less than 5 μm) in indoor air is about 1 to 3 μg/m ³ , which is low. On the other hand, as shown in FIG. 5, it can be seen that the amount of coarse suspended particles (particle size exceeding 1 μm and less than 5 μm) collected per hour was 10 to 20 μg, which was a larger amount.

Furthermore, focusing on the 10-hour period from 1:00 AM to 11:00 AM on April 20, 2022, the average concentration of coarse suspended particles during this period was 2.1 μg/m3, while the average concentration of fine suspended particles was 18 μg/ ^m3 . It was .0μg/ ^m3 . In addition, the tape was moved as a filter once every hour, and the average amount collected during this period was 16.0 μg of coarse suspended particles and 16.1 μg of fine suspended particles. If the same air is sampled during this period, without using the present invention, with a device using a conventional virtual impactor, by moving the tape once every hour, at a sampling rate of about 1 m ³ per hour, The average amount of coarse suspended particles collected is only 2.1 μg. With the conventional method, if you try to collect coarse suspended particles by moving the tape once every 10 hours and increasing the collection time, not only will the temporal resolution deteriorate, but the cumulative amount of collected particles will increase. 21 μg and 180 μg of fine suspended particles, which is a sufficient amount of coarse suspended particles to be collected, but the amount of fine suspended particles collected may be too large and the filter may become clogged with particles, making it impossible to collect them. is expected. In conventional methods, when a filter collects 80 to 100 μg of suspended particles, the filter becomes clogged and cannot be collected. Furthermore, if the detection limit of the β-ray absorption method is expressed as the amount of filter capture, it is, for example, 1 to 2 μg, and the average concentration of coarse suspended particles is 2.1 μg/m ³ , so the detection limit is expressed once every hour as in the conventional method. If the tape is moved as shown in FIG. On the other hand, since the average amount collected by the filter in the present invention was 16.0 μg, highly accurate measurement was possible.

As described above, the effects of the present invention make it possible to efficiently concentrate coarse suspended particles in the sample air even at a low concentration, increase the amount of particles collected in the filter, and improve sensitivity. You can see that the measurement was successful.

1 Virtual impactor 2 Bypass means 3 First position for collecting suspended particles 4 Second position for collecting suspended particles 5 Tape take-up roller 6 Tape supply roll 7 Tape feeding mechanism 8 Arrow mark 9 Tape-shaped membrane filter 10 First β-ray source 11 Second β-ray source 12 First β-ray detector 13 Second β-ray detector 14 β-ray flow 21 First preamplifier 22 Second preamplifier 23 Photodetector 24 Light source 26 Optical fiber 27 Third preamplifier 28 Arithmetic processing Part 40 Nozzle part 41 Air collection part 42 Air guide part 43 Spout port 44 Cylindrical part 45 Constriction pipe part 46 First discharge port 47 Second discharge port 48 Air collection pipe part 49 Straight pipe part 50 Inflow hole 51 Collection part 52 Classifier 53 Collection port G1 Pressure sensor G2 Pressure sensor G3 Pressure sensor G4 Pressure sensor L1 Flow path L2 Flow path L3 Flow path P1 Suction pump P2 Suction pump P3 Suction pump MFM1 Flow rate sensor MFM2 Flow rate sensor PV1 Flow rate adjustment valve PV2 Flow rate adjustment valve PV3 Flow rate adjustment Valve PV4 Flow rate adjustment valve

The present invention classifies suspended particles in the air using a virtual impactor and separates air containing coarse suspended particles with large particle sizes and air containing fine suspended particles with small particle sizes,
The air containing coarse suspended particles is sucked in, and the coarse suspended particles are collected in a filter.
The air containing the fine suspended particles flowing out from the virtual impactor is divided into a flow to a collection part that collects the fine suspended particles, and a bypass flow that bypasses the fine suspended particles without collecting them, and the air is sucked. This method of collecting suspended particles is characterized in that fine suspended particles are collected on a filter at a position different from a position where coarse suspended particles are collected.

Further, the present invention sucks air containing suspended particles and divides the suspended particles in the sucked air into air containing coarse suspended particles with a large particle size and air containing fine suspended particles with a small particle size. A virtual impactor for classification,
a suction means that is connected to the virtual impactor and sucks a part of the air containing the fine suspended particles flowing out from the virtual impactor and distributes the air to a collecting section for the fine suspended particles; bypass means for sucking the remainder of the air contained therein and bypassing it to the exhaust section as a bypass flow that does not collect fine suspended particles ;
A tape-shaped filter is provided, and air containing coarse suspended particles and air containing fine suspended particles, which have been classified by the virtual impactor, are sucked through different positions of the tape-shaped filter to separate coarse suspended particles and fine suspended particles. a collection means that specifically and continuously collects the particles at different positions of the tape-shaped filter;
detection means for successively detecting floating particles collected at different positions of the tape-shaped filter by the collection means;
Continuous measurement of suspended particles characterized by comprising a calculation recording means for calculating and recording coarse particles in the air and fine suspended particles in the air from the output of the detection means and the integrated value of the suction atmospheric flow rate. It is a device.

Claims (2)

The suspended particles in the air are classified using a virtual impactor, and the air is divided into air containing coarse suspended particles with a large particle size and air containing fine suspended particles with a small particle size.
The air containing coarse suspended particles is sucked in, and the coarse suspended particles are collected in a filter.
A method for collecting suspended particles, characterized in that air containing fine suspended particles is sucked while being bypassed, and the fine suspended particles are collected on a filter at a position different from the position where coarse suspended particles are collected. a virtual impactor that sucks air containing suspended particles and classifies the suspended particles in the sucked air into air containing coarse suspended particles with a large particle size and air containing fine suspended particles with a small particle size;
a bypass means that is connected to the virtual impactor and that sucks air containing fine suspended particles and bypasses it to an exhaust section;
A tape-shaped filter is provided, and air containing coarse suspended particles and air containing fine suspended particles, which have been classified by a virtual impactor, are sucked through different positions of the tape-shaped filter to produce coarse suspended particles and fine suspended particles. a collection means for successively collecting and separately at different positions of a tape-shaped filter;
detection means for successively detecting floating particles collected at different positions of the tape-shaped filter by the collection means;
A method for detecting suspended particles characterized by comprising a calculation recording means for calculating and recording coarse suspended particles in the air and fine suspended particles in the air from the output of the detection means and the integrated value of the suction atmospheric flow rate. Continuous measurement device.