JP2012026954A - Collection apparatus, collection method and concentration measuring method of substance to be collected in atmosphere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collection apparatus of a substance to be collected in atmosphere, which can exclude influence of wind velocity in a site and achieve stable collection of the substance to be collected; a collection method of the substance to be collected in atmosphere, which can achieve inexpensive and high-sensitive collection without requiring accurate flow rate management such as an active method; and a concentration measuring method of the substance to be collected in atmosphere, which can accurately reflect Fick's diffusion first rule expression and adapt a sampling rate SR to the substance to be collected by a calculation expression.SOLUTION: A collection apparatus includes: a housing 10 which has an internal space 12 and forms an inflow port 14 capable of allowing air in atmosphere to flow into the space 12 and an outflow port 16 capable of allowing air in the space 12 to flow out; flowing means 20 for allowing air to flow from the inflow port 14 into the space 12, allowing the air to flow toward the outflow port 16 at a fixed speed and generating an air flow of a predetermined speed in the space 12; and holding means 30 for holding a passive sampler 2 at a position where the air flow is generated.

Description

  The present invention relates to a collection device for collecting a collected material such as formaldehyde or volatile organic compound (VOC) floating in the atmosphere on a passive sampler, and a collection device for collecting the collected material by the collection device. The present invention relates to a collection method and a concentration measurement method for measuring the concentration of a substance to be collected collected by this collection method.

  Conventionally, passive samplers that have been exposed to the atmosphere and collected by natural diffusion have been used to collect substances to be collected such as formaldehyde and volatile organic compounds (VOC) floating in the atmosphere ( Patent Document 1). In this passive sampler, the concentration of the collection surface is always made zero by the adsorbent and the collection agent provided in the passive sampler, and by keeping a constant concentration gradient with a higher concentration of the collected substance, The substance to be collected is collected by utilizing the movement diffusion phenomenon of the substance concentration.

  On the other hand, the collection rate per unit area of the passive sampler, that is, the unit collection rate J, is determined by the concentration gradient (C / L) and the molecular diffusion coefficient D [ng / sec] of the diffusing substance. Fick's first diffusion equation (J = D × C / L) can be used. Here, in Fick's first law equation of diffusion, C represents the ambient concentration [ng / ml], and L represents the diffusion length [cm], that is, the length from the inlet of the passive sampler to the collection surface. Further, as shown in the equation (SR = A × D × C / L), the total of the passive samplers is obtained by multiplying the collection area A by the collection rate J (J = D × C / L) per unit area. The collection speed SR can be obtained. This is generally referred to as sampling rate SR, and is known as an inherent collection rate for a specific material to be collected by the passive sampler. This sampling rate SR is expressed in a dimensional unit such as [μg / (ppm × min)], whereby the sampling rate SR and the sampling amount M [μg] obtained from the analysis result after collection and It is known that the concentration C ′ of the substance to be collected in the atmosphere can be obtained from the value of the collection time t [min] based on the formula (C ′ = M / (SR × t)). .

JP 2003-114176 A

  However, since the sampling rate SR of the passive sampler is collected by natural diffusion, as shown in FIG. 5, it does not show a constant value due to the influence of the wind speed at the site. There is a problem that the rate SR fluctuates significantly. This is considered to be because the diffusion concentration gradient extends from the passive sampler and creates a concentration gradient outside the passive sampler due to a decrease in the wind speed around the passive sampler, and the diffusion length L fluctuates greatly. ing.

  For this reason, in many commercial products, it is common to perform a design design such that the extension is apparently reduced by increasing the diffusion length L. However, it is impossible in principle to make the stretching zero, and the wind speed always fluctuates in the actual measurement environment, and the diffusion length L also fluctuates according to the wind speed fluctuation. It is almost impossible to predict the diffusion length L and make it constant. Thus, conventionally, when accurately measuring the concentration of trapped substances in the atmosphere using a passive sampler, the sampling rate SR is obtained by actual measurement according to the measurement site, or active using a pump or the like. This is a subordinate method that requires a general calculation method that uses the sampling rate SR as a representative value in advance by comparison with the method, and uses this, and is complicated and less accurate than the active method. There is a problem.

  Then, this invention makes it the 1st objective to provide the collection apparatus of the to-be-collected substance in the air which eliminates the influence of the wind speed in a field and enables the collection of the to-be-collected substance stably. . In addition, the present invention provides a method for collecting a substance to be collected in the atmosphere, which does not require precise flow rate management as in the active method, and enables inexpensive and highly sensitive collection. The purpose of 2. Furthermore, the present invention provides a method for measuring the concentration of collected substances in the atmosphere that accurately reflects Fick's first law equation of diffusion and can adapt the sampling rate SR for the collected substances by a calculation formula. This is the third purpose.

  In order to achieve the first object, an apparatus for collecting a substance to be collected in the atmosphere according to the present invention has a space inside, and an inlet capable of flowing air in the atmosphere into the space, A housing in which an outlet from which air in the space can flow is formed, and air flows into the space from the inlet, and the air flows at a constant speed toward the outlet; And a holding means for holding a passive sampler at a position where the gas flow is generated.

  As described above, according to the trapping device for collected substances in the atmosphere according to the present invention, by generating a gas flow at a constant speed by the flow means and holding the passive sampler at a position where the gas flow is generated. Since the wind speed of the air with respect to the passive sampler can be made constant, the influence of the wind speed at the site can be eliminated and stable collection of the collected material can be enabled.

  In the apparatus for collecting a substance to be collected in the atmosphere according to the present invention, the inflow port is preferably formed in a porous shape, and thus the inflow port is formed in a porous shape, thereby Even when the wind is strong, the speed of the air flowing in from the inlet can be made constant, so that the influence of the wind speed at the site can be further eliminated.

  In the apparatus for collecting a substance to be collected in the atmosphere according to the present invention, the flow means is provided at the outlet and drives a fan that generates a gas flow at a predetermined speed in the space. It is preferable to provide a battery that allows the flow means to have a simple structure, and the cost for manufacturing the collection device can be reduced. Further, since the fan is driven by a battery, it can be used in a measurement place where it is difficult to supply power.

  Further, in the apparatus for collecting a substance to be collected in the atmosphere according to the present invention, the holding means holds the passive sampler so that the collection surface of the passive sampler is uniformly exposed to the gas flow. It is preferable to be configured so that it is possible to collect the substance to be collected more stably. Here, the configuration capable of holding the passive sampler so that the collection surface of the passive sampler is uniformly exposed is, for example, in the case of a tubular passive sampler, the direction of the central axis of the passive sampler and the flow of the gas flow. It is the structure hold | maintained so that a direction may become parallel.

  In order to achieve the second object, a method for collecting a substance to be collected in the atmosphere according to the present invention is a method for collecting a substance to be collected that is performed using the collection device, The gas flow that flows at a constant speed in the space is generated by the flow means, and the trapped substance contained in the gas flow is collected by a passive sampler.

  As described above, according to the method for collecting a substance to be collected in the atmosphere according to the present invention, a gas flow that flows at a constant speed in the space of the housing is generated, and the target contained in the gas flow is generated. By collecting the collected material in the passive sampler, the air velocity of the air to the passive sampler can be kept constant, eliminating the influence of the wind velocity at the site and enabling stable collection of the collected material. In addition, it is possible to enable collection with low cost and high sensitivity without requiring precise flow rate management as in the active method.

  Furthermore, in order to achieve the third object, the method for measuring the concentration of collected substances in the atmosphere according to the present invention is a method for measuring the concentration of collected substances collected by the collecting method. Based on the value of the molecular diffusion coefficient (D), the value of the ambient concentration (C), the value of the diffusion length (L), and the value of the collection area (A) of the passive sampler, (SR = A × D XC / L) Calculate the total collection rate (SR) from the equation, the value of the total collection rate (SR), and the value of the amount of collected material (M) collected by the passive sampler Based on the value of the collection time (t), the concentration (C ′) of the substance to be collected in the atmosphere is calculated from the formula (C ′ = M / (SR × t)).

  As described above, according to the method for measuring the concentration of a substance to be collected in the atmosphere according to the present invention, fluctuations in the value of the diffusion length L can be suppressed by eliminating the influence of the wind speed at the site. As a result, Fick's first law equation of diffusion (J = D × C / L) is accurately reflected, and the sampling rate of almost all the trapped substances to be diffused by the equation (SR = A × D × C / L) SR can be estimated theoretically. In addition, since the sampling rate SR can be estimated, the concentration C ′ of the trapped substance in the atmosphere can be accurately calculated by the formula (C ′ = M / (SR × t)). High concentration measurement can be made possible.

  As described above, according to the present invention, there is provided a trapping device and a trapping method for a trapped substance in the air that eliminates the influence of wind speed at the site and enables stable trapping of the trapped substance. can do. In addition, according to the present invention, the concentration measurement method of the collected substance in the atmosphere that can accurately reflect the Fick's first law equation of diffusion and adapt the sampling rate SR for the collected substance by a calculation formula. Can be provided.

It is sectional drawing which shows schematic structure of the collection apparatus which concerns on one Embodiment of this invention. It is a side view which shows the state which looked at the collection apparatus which concerns on this embodiment from the A direction. It is a graph which shows the comparison of the collection amount at the time of indoor environment measurement of the collection method which concerns on this embodiment, and the conventional collection method. It is a graph which shows the comparison measurement result with the active method in two places in the office where wind speed differs. It is a graph which shows the relationship between the collection amount of a passive sampler, and a wind speed.

  Next, the collection device concerning one embodiment of the present invention is explained based on a drawing. As illustrated in FIG. 1, the collection device 1 according to the present embodiment generates a gas flow, a housing 10 having a space 12 therein, a flow unit 20 that generates a gas flow at a predetermined speed in the space 12, and a gas flow. The holding part 30 holding the passive sampler 2 is provided at the position. In the collection device 1 according to the present embodiment, a tube-type passive sampler is used, but the present invention is not limited thereto, and various passive samplers can be used, and the collection device 1 according to the present embodiment is Various modifications can be made depending on the type and shape of the passive sampler.

  The housing 10 includes a housing body 10a formed in a cylindrical shape, and a lid member 10b that can close an opening on the upstream side (left side in FIG. 1) of the housing body 10a.

  The housing body 10a can accommodate the passive sampler 2 and has a diameter and a length that allows the gas flow generated by the fluidizing section 20 to flow sufficiently stably in the state where the passive sampler 2 is accommodated. Have. Further, the inner surface of the housing body 10a is formed by a smooth surface so as not to disturb the flow path of the gas flow flowing in the space 12.

  The lid member 10b is configured to be detachable from the housing body 10a, and an inflow port 14 through which air in the atmosphere can flow is formed in the space 12 of the housing 10. As shown in FIG. 2, the inflow port 14 is formed of a plurality of orifices formed in a porous shape, that is, continuously formed at equal intervals on the circumference of the same circle centering on the center of the lid member 10b. It is comprised so that the static pressure of the fluidized part 20 may not be increased by the environment. The entire region on the downstream side (right side in FIG. 1) of the housing main body 10a is open, thereby constituting an outlet 16 through which air in the space 12 can flow out.

  As shown in FIG. 1, the flow unit 20 includes a fan 22 provided at the outlet 16 of the housing 10 and a power source (not shown) that supplies electric power for driving the fan 22. The fan 22 is driven to cause air to flow into the space 12 from the inlet 14 and to flow the air toward the outlet 16 at a constant speed to generate a gas flow at a predetermined speed in the space 12. It is configured to let you. Here, the fan 22 is preferably capable of generating a gas flow having a flow rate of 0.3 [m / sec] or more. In particular, by setting it to 1.0 [m / sec] or more, it is possible to reduce the change in the collection speed according to the fluctuation of the flow speed. This is significantly different from the active method, and has an advantage that fine control is not required for flow velocity management, and it is possible to configure an inexpensive and accurate collection device. Further, the fan 22 is preferably a low-power and small-sized fan that can be driven by two AA batteries for 24 hours or longer. If the fan 22 is configured to generate a gas flow at a predetermined speed, the fan 22 has a fine flow rate. There is no need to have control.

  The holding unit 30 includes a support column 32 formed in a rod shape and a recess 34 that can be fitted to the end of the passive sampler 2. The upstream end portion (left side in FIG. 1) of the support column 32 is connected to the center position of the inner surface of the lid member 10b so that the center axis of the support column 32 is coaxial with the center axis of the housing body 10a. A recess 34 is provided at the downstream end (right side in FIG. 1) of the support 32 so that the opening faces the downstream. The holding portion 30 is configured such that the central axis of the passive sampler 2 is coaxial with the central axis of the housing body 10a, that is, parallel to the flow direction of the gas flow, by fitting the end portion of the passive sampler 2 into the recess 34. In contrast, the passive sampler 2 can be held so that the collection surface (circumferential surface) of the passive sampler is uniformly exposed. In addition, the holding unit 30 has such a length that the passive sampler 2 can be accommodated in the space 12 of the housing 10 when holding the passive sampler 2.

  Next, from the method of collecting the substance to be collected in the atmosphere using the collection device 1 according to the present embodiment and the amount of the substance to be collected collected by this collection method, the atmosphere is collected. A method for calculating the concentration of the trapped substance in it will be described. In order to collect a substance to be collected in the atmosphere using the collection device 1 according to this embodiment, first, after removing the lid member 10b from the housing body 10a, the passive sampler 2 is taken out from the airtight bag, The end of the passive sampler 2 is held by the holding unit 30. Next, the lid member 10 b is attached to the housing body 10 a so that the passive sampler 2 is positioned in the space 12 of the housing 10. Thereafter, an operation switch (not shown) of the flow unit 20 is operated to drive the fan 22 to generate a gas flow at a constant speed in the space 12. Thereby, the collection surface of the passive sampler 2 is uniformly exposed to the gas flow containing the substance to be collected, and the substance to be collected is collected by the passive sampler 2 by the movement diffusion phenomenon. After a predetermined collection time has elapsed, the drive of the fan 22 is stopped, the lid member 10b is removed from the housing body 10a, and the passive sampler 2 is collected in an airtight bag. Thereafter, the passive sampler 2 is transported to the measurement chamber, and the collection amount M of the substance to be collected collected by the passive sampler 2 is measured in the measurement chamber by various known methods.

  In order to calculate the concentration of the substance to be collected in the atmosphere using the collection device 1 according to this embodiment, first, the Fick's first law equation (J = D × C / L) was used. The unit collection speed J for the substance to be collected of the passive sampler 2 is calculated. Here, the collection device 1 according to the present embodiment eliminates the influence of the wind speed by generating the gas flow to which the passive sampler 2 is exposed at a predetermined wind speed and in a constant state, and thus the diffusion length L, that is, the passive Since the value of the length from the inlet of the sampler 2 to the collection surface can be made constant, the unit collection speed J can be calculated by accurately reflecting the Fick's first law equation. Here, in Fick's first law equation of diffusion, D represents a molecular diffusion coefficient of a substance to be collected, C represents an ambient concentration, and C / L represents a concentration gradient.

  Next, based on the value of the unit collection speed J calculated from the first law equation of Fick's diffusion (J = D × C / L) and the value of the collection area A of the passive sampler 2, (SR = A The total collection speed, that is, the sampling rate SR is calculated from the formula (DxC / L). This sampling rate SR is an inherent collection rate for a specific material to be collected by the passive sampler. Here, the dimensional unit of the sampling rate SR is [μg / (ppm × min)].

  Next, the value of the sampling rate SR obtained from the equation (SR = A × D × C / L), the value of the trapped substance M actually collected by the passive sampler 2, Based on the value of the collection time t, the concentration C ′ of the trapped substance in the atmosphere is calculated from the formula (C ′ = M / (SR × t)).

  As described above, according to the method for measuring the concentration of collected substances in the atmosphere according to the present embodiment, Fick's first law equation of diffusion (J = D × C / L) is accurately reflected, and (SR = A It is possible to theoretically estimate the sampling rate SR of almost all of the diffusing trapped substances by the formula (× D × C / L). Further, since the sampling rate SR can be estimated, the concentration of the trapped substance in the atmosphere can be accurately calculated by the formula (C ′ = M / (SR × t)), so that the accuracy is high. Concentration measurements can be made possible.

  Next, the Example of the collection apparatus 1 which concerns on this embodiment is described using FIGS. FIG. 3 is a graph showing the ratio of the main VOC amount [μg] collected in the collection agent of Example 1 and the main VOC amount [μg] collected in the collection agent of Comparative Example 1. FIG. 4 is a graph showing comparative measurement results with the active method at two points in the office with different wind speeds, and FIG. 5 is a graph showing the relationship between the collection amount of the passive sampler and the wind speed.

[Collecting volatile organic compounds]
In this measurement, a collection method (Example 1) in which a passive sampler is accommodated in the collection device 1 according to the present embodiment to collect a substance to be collected, and the passive sampler is simply exposed to the environment. Then, the conventional collection method (Comparative Example 1) for collecting the substance to be collected was carried out at the same measurement site, and the amount of the substance to be collected was compared.

  The measurement field was selected in a new office where the wind speed was approximately 0 to 0.04 [m / sec] and the extension of the diffusion length of the passive sampler was likely to occur. In Example 1, the wind speed of the gas flow generated by the fluidizing section 20 of the collection device 1 was set to be 0.3 to 0.5 [m / sec]. The material to be collected was a volatile organic compound (VOC), and the passive sampler used was a tube-type passive sampler for VOC collection. Under these measurement conditions, 24 hours of collection was performed at the measurement site, and then the adsorbent was taken out from the passive sampler, and VOCs collected by the solvent extraction method were extracted from the collection agent into an organic solvent. This solution was quantitatively analyzed with an analytical instrument (gas chromatograph mass spectrometry).

  In this measurement, as shown in FIG. 3, the result that the collected amount of Example 1 was about 1.6 times larger than the collected amount of Comparative Example 1 was obtained. Therefore, it became clear that the collection efficiency of Example 1 was 60% higher than that of Comparative Example 1, and the collection at a lower concentration was possible. This measurement result is a result of a steady environmental test in the environmental test apparatus, that is, a graph showing the relationship between the collected amount of the passive sampler and the wind speed in FIG. sec] was consistent with the result that the collection efficiency was about 60% higher than the collection efficiency when the wind speed was 0 to 0.04 [m / sec]. Here, the vertical axis in FIG. 5 indicates that the collection amount of the passive sampler is a ratio [%] to the collection amount obtained by the active method of collecting using a pump in order to clarify the standard. It is represented.

[Comparison with the active method at two locations in the office with different wind speeds]
Next, at two points of different wind speeds in the newly built office, a collection method (Example 2) for collecting a collected material by accommodating a passive sampler in the collection device 1 according to the present embodiment; And the conventional collection method (Comparative Example 2), in which the passive sampler is simply exposed to the environment to collect the collected material, and the amount of collected material is compared. Contaminated air analysis was performed.

  There were two measurement fields: a point in the newly built office with a wind speed of 0.05 [m / sec] and a point with almost no wind at a wind speed of 0.01 [m / sec] or less. The collected substances were 1,2-dichloropropene, 2-butanone (MEK), 2-pinene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene. The other measurement conditions and analysis conditions were the same as those described above for [Collecting volatile organic compounds].

In this measurement, as shown in FIG. 4, Example 2 was obtained at two points with different wind speeds at a ratio close to 100% compared to the active method for all collected substances. When the wind speed was different for the substances to be collected, the ratio with the active method was different, and the result was that the collected amount tended to decrease by about 20% to 30%. In FIG. 4, the vertical axis represents the amount collected (M _0.05 ) at a point where the wind speed is 0.05 [m / sec] and the amount collected (M ₀ .0) at a point where the wind speed is 0.01 [m / sec] _{. 01} ) (M _0.01 / M _0.05 ) [%]. In addition, the amount of collection (M _0.01 , M _0.05 ) at each point in Example 2 and Comparative Example 2 is determined by the active method of collecting using a pump in order to clarify the standard. The ratio (M _0.01 / M _a , M _0.05 / M _a ) [%] with the collected amount (M _a ). From this measurement result, it is clear that Comparative Example 2 is affected by the environmental wind speed, whereas Example 2 is hardly affected by the environmental wind speed.

  According to the collection device 1 according to the present embodiment, it becomes possible to eliminate the influence of wind speed at the site, and thus passive sampling, which is generally known as a simple method, is collected using a pump. The accuracy corresponding to general active sampling can be improved.

  Moreover, since the collection apparatus 1 which concerns on this embodiment is an apparatus of the simple structure of generating a gas flow in the housing 10 with the fan 22 driven by a dry cell, it should be used also in a place where it is difficult to secure a power source. In addition, it can be carried out without incurring costs in an investigation method in which a large number of measurement points are set, such as a diffusion investigation from a collection substance generation source such as an expressway or a production factory.

  Furthermore, in the collection device 1 according to the present embodiment, the housing 10 is configured to have a light shielding property, so that not only the influence of the wind speed at the site but also the light shielding effect such as sunlight can be provided.

  Furthermore, since the collection device 1 according to the present embodiment can eliminate the influence of the wind speed, it is not necessary to intentionally increase the diffusion length L like a general passive sampler. Therefore, it is possible to create and use a passive sampler in which the diffusion length L is extremely shortened and the collection speed is increased as much as possible.

  The collection device according to the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea of the present invention. For example, in the collection device 1 according to the present embodiment, the housing 10 is composed of a cylindrical housing body 10a and a lid member 10b, but is not limited thereto, and has a space inside. Any configuration and shape may be used as long as an inflow port through which air in the atmosphere can flow in and an outflow port through which the air in the space can flow out are formed in the space.

  Further, in the collection device 1 according to the present embodiment, the inflow port 14 is formed in a porous shape, but is not limited thereto, and the inflow port 14 can flow air in the atmosphere into the housing. Any configuration, shape, and number may be used as long as the configuration is appropriate.

  Furthermore, in the collection device 1 according to the present embodiment, the flow unit 20 is configured by the fan 22 and the power source. However, the present invention is not limited to this, and air flows into the space from the inlet of the housing. Any configuration and shape may be used as long as the air is made to flow at a constant speed toward the outlet and a gas flow having a predetermined speed is generated in the space.

  Furthermore, in the collection device 1 according to the present embodiment, the holding unit 30 is configured to be able to hold so that the collection surface (circumferential surface) of the passive sampler 2 is uniformly exposed to the gas flow. However, the present invention is not limited to this, and it is sufficient if the passive sampler is held at a position where a gas flow is generated.

DESCRIPTION OF SYMBOLS 1 Collection apparatus, 10 housing, 12 space, 14 inflow part, 16 outflow part, 20 fluidization part, 30 holding part

Claims (6)

A housing having a space therein, and an inflow port through which air in the atmosphere can flow and an outflow port through which the air in the space can flow out are formed;
A flow means for causing air to flow into the space from the inflow port, causing the air to flow at a constant speed toward the outflow port, and generating a gas flow at a predetermined speed in the space;
A holding device for holding a passive sampler at a position where the gas flow is generated. The apparatus for collecting a substance to be collected in the atmosphere according to claim 1, wherein the inflow port is formed in a porous shape. The flow means is
A fan provided at the outlet and generating a gas flow at a predetermined speed in the space;
The apparatus for collecting a substance to be collected in the atmosphere according to claim 1, further comprising: a battery that drives the fan. The said holding | maintenance means is comprised so that the passive sampler can be hold | maintained so that the collection surface of a passive sampler may be uniformly exposed with respect to the said gas flow. An apparatus for collecting substances to be collected in the atmosphere according to the item. A method for collecting a substance to be collected that is performed using the collection device according to claim 1,
The gas flow flowing at a constant speed in the space is generated by the flow means, and the trapped substance contained in the gas flow is collected by a passive sampler. How to collect the collected material. A method for measuring the concentration of a substance to be collected collected by the collection method according to claim 5,
Based on the value of the molecular diffusion coefficient (D), the value of the ambient concentration (C), the value of the diffusion length (L), and the value of the collection area (A) of the passive sampler, (SR = A × D × C / L) Calculate the total collection rate (SR) from the formula,
Based on the value of the total collection rate (SR), the value of the collected amount (M) of the collected material collected by the passive sampler, and the value of the collection time (t), (C ′ = A method for measuring the concentration of a substance to be collected in the air, wherein the concentration (C ′) of the substance to be collected in the atmosphere is calculated from the equation M / (SR × t)).

Images