JP2896575B2 - Method for separating and measuring suspended substances - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring suspended substances in general water bodies such as oceans and lakes in the field and, more particularly, to an apparatus therefor. And a water quality measurement method for continuously and automatically measuring the concentration of each of the suspended substances among the turbidity factors in the water area into phytoplankton and other suspended substances (hereinafter referred to as detritus). Things.

[Prior Art] A conventional turbidity monitoring device generally uses any one of a scattered light measurement method, an absorbance measurement method, and a volume extinction coefficient measurement method. These devices have been used for the purpose of knowing the degree of turbidity due to a single substance and for the purpose of knowing the degree of turbidity as a collective index of water quality without considering the members of the turbidity.

In addition, turbid members in general waters such as seas are the first
They can be roughly classified as shown in the table.

As shown in Table 1, with the progress of eutrophication in general water bodies, in monitoring turbidity, natural turbidity (turbidity caused by phytoplankton, etc.) and artificial turbidity (turbidity caused by construction, etc.) are compared. There is a need for a technology to separate and measure turbidity members, such as those for the purpose and those for the purpose of comparing turbidity due to phytoplankton with other turbidity (turbidity due to soil particles or organic detritus etc.) Is growing.

For this reason, in the fields of absorbance measurement and volume extinction coefficient measurement, monitoring methods and apparatuses for separating and measuring turbid members by a measurement method using a multi-wavelength light flux have been proposed.

The present inventors have also previously disclosed Japanese Patent Publication No. 60-38654, "Method for Measuring the Concentration of Suspended Solids in Water and the Index of Organic Substances," Japanese Patent Application No. 58-2071.
No. 68, "Water quality measurement method using three-wavelength volume extinction coefficient", proposed a method to measure turbidity in water using volume extinction coefficient measurement.

For the former, dissolved organic matter (using COD as an index) by measuring the volume extinction coefficient using ultraviolet light and near-infrared light
A monitoring method and device for measuring organic substances (suspended COD as an index) and suspended substances (SS as an index), and measuring the concentration of organic substances in turbidity (COD, etc.) It is.

For the latter, the volumetric extinction coefficient of three wavelengths is measured so that no error occurs even if the constituents of the suspended substance change because the former method is improved to enable continuous measurement even in general water bodies. In this method, the suspended substances are separated into phytoplankton and other suspended substances (detritus), and each of them is monitored and measured.

Japanese Patent Application Laid-Open No. 54-89796, "Method and Apparatus for Measuring Index of Concentration of Organic Substances in Water" has also been proposed as a method using a fluorescence method. This is the development of a device that monitors the concentration of organic matter indicators (COD, BOD, TOC) by measuring the fluorescence emitted by organic matter in water. Also chlorophyll-a
A method and an apparatus for measuring the distribution of only phytoplankton in a water body by measuring red fluorescence (chlorophyll fluorescence) emitted from the water have already been devised.

As described above, in both the absorption method and the fluorescence method, methods for separating and measuring turbid members have been developed.

[Problem to be Solved by the Invention] However, in the method using the improved three-wavelength volume extinction coefficient measurement, the measurement is performed by using a three-dimensional simultaneous equation of the three-wavelength volume extinction coefficient whose coefficient is determined by a previously measured value. Using the measured value of the volume extinction coefficient of the three wavelengths of the water to be measured, detritus by solving the ternary simultaneous equation, phytoplankton, to measure the concentration of dissolved organic matter, a coefficient in a predetermined equation The small errors contained in the data have a large effect on the final measured value, and a large amount of data is required to determine each coefficient.Accurate measurement can be realized only when the fluctuation of the determined coefficient is small. Problems. Further, a method of separating phytoplankton and detritus using a fluorescence method has not been invented.

Therefore, the present invention is intended to measure only suspended substances,
This is a method for measuring water quality by treating suspended substances in turbidity as two types of substances, phytoplankton and other suspended substances (detritus), and provides a simple and stable measurement method. The purpose is to:

[Means for Solving the Problems] In the method for separating and measuring a suspended substance according to the first invention, the indicator concentration of the suspended substance is composed of the indicator concentration of phytoplankton and the detritus which is the other suspended substance. In the method for measuring suspended solids, which is considered as two types of indicator concentrations, the ratio (τ) between the volume extinction coefficient of phytoplankton and the indicator concentration of phytoplankton (τ) and the indicator concentration of detritus to the volume extinction coefficient of detritus are determined in advance. Is determined, the volume extinction coefficient of the water to be measured and the phytoplankton index concentration are measured, and the volume extinction coefficient of the phytoplankton is determined from the measured phytoplankton index concentration. The detritus volume extinction coefficient was determined from the difference between the measured volume extinction coefficient of the measured water and the volume extinction coefficient of the phytoplankton, and the detritus index concentration was determined. Is shall.

In the method for separating and measuring a suspended substance according to a second invention, in the method for separating and measuring a suspended substance according to the first invention, the phytoplankton indicator concentration is defined as a fluorescence emission intensity.

In the method for separating and measuring a suspended substance according to a third invention, in the method for separating and measuring a suspended substance according to the first or second invention, the previously determined volume extinction coefficient of phytoplankton and phytoplankton Is determined from the slope of the correlation between the phytoplankton index concentration or the fluorescence emission intensity of the measured water and the volume extinction coefficient of the measured water.

[Effect] The zooplankton concentration is extremely small in general waters as compared with phytoplankton and detritus, and is a value which can be usually ignored in optical measurement.
Assuming that the suspended substance is separated into detritus and phytoplankton, the volume extinction coefficient (c−c _w ) _λ and the fluorescence intensity F can be expressed as follows.

(C−c _w ) _λ = α (detritus concentration) + β (phytoplankton concentration) where c _w is the volume extinction coefficient of water itself, λ is a suffix indicating wavelength, and α and β are coefficients (constants) F = γ (detritus concentration) + δ (phytoplankton concentration) where γ and δ are coefficients (constants) Here, since the fluorescence intensity coefficient γ of detritus is so small that it can be ignored, the formula is as follows: F = δ (phytoplankton concentration) Can be approximated.

In addition, the ratio (τ) of the phytoplankton volume extinction coefficient (c−c _w ) _λ to the phytoplankton fluorescence intensity (F) of a living phytoplankton is a constant value according to the type of phytoplankton. Τ is expressed by the following equation.

τ = (c−c _w ) _λ / F = B / δ Therefore, the following equation is derived from the above equations.

(C−c _w ) _λ = α (detritus concentration) + τF where the first term on the right side represents the volume extinction coefficient due to detritus, and the second term represents the volume extinction coefficient due to phytoplankton.

[Examples] The turbidity members of the general water body are as shown in Table 1 above. Among these members, only the suspended substances are measured, and the suspended substances are phytoplankton. The measurement method and device for monitoring were roughly classified into detritus.

The _λ Absorbance and volume extinction coefficient of the near-infrared wavelength (e.g. _{660,690nm) (c-c w)} , scattering by suspended state material is affected only to absorption, since the influence of Dissolved substances negligible,
Widely used for measuring turbidity.

However, the relationship between (c−c _w ) _λ in the general sea area and the suspended solids dry weight concentration (SS) as an indicator of suspended solids shows a variation as shown in FIG. It is known to indicate

This is due to a qualitative change in the suspended substance. The following are assumed to be qualitative changes.

1) Changes in the composition ratio of phytoplankton and detritus, which are members of the suspended substance 2) Changes in the particle size and specific gravity of suspended substance particles 3) Changes in the species composition of phytoplankton These qualitative changes Are changing in relation to each other,
As shown in FIG. 2, this causes a variation in the correlation between (c−c _w ) _λ and the dry matter concentration (SS).

However, the practical application of the monitoring device for all these qualitative changes is difficult with the current technology. Therefore, the separation and measurement technology of phytoplankton and detritus of item 1) was studied.

When the suspended substances are roughly classified into phytoplankton and detritus, the volume extinction coefficient (c−c _w ) _{660 at} the near-infrared wavelength (λ = 660 nm) is expressed as follows.

(C−c _w ) ₆₆₀ = α (detritus concentration) + β (phytoplankton concentration) where α and β are proportional coefficients. Next, in the measurement of IN VIVO fluorescence, the excitation light near 436 nm causes a chlorophyll concentration around 685 nm. It is known that a strong fluorescence peak based on a is observed. Therefore, the fluorescence intensity (F) in this case can be expressed as follows.

Here, γ and δ are proportional coefficients, suffix 436 is a suffix indicating an excitation wavelength of 436 nm, and suffix 685 is a suffix indicating a fluorescent wavelength of 685 nm.

(Example 1) First, seawater at Tokyo Bay Shibaura Wharf was collected, and skeleton skeleton, which was a diatom, was cultured by aeration culture. Skeletonema in the logarithmic growth phase during culture is considered to have more viable skeletonetema and relatively less detritus based on dead cells.

The culture water in the logarithmic growth phase was sampled, and chlorophyll-a, the number of cells, absorbance at 660 nm, and fluorescence intensity were measured. The results are shown in FIGS. 3 and 4 below. FIG. 3 is a graph showing the correlation between the number of cultured skeletonetema cells and the absorbance (Log (1 / T)), and FIG. 4 is a graph showing the correlation between the number of cultured skeletonetema cells (cells / ml) and the fluorescence intensity. FIG.

In this case, assuming that the concentration of phytoplankton in the formula is indicated by the number of cells and that the detritus concentration of the culture water is negligibly small, the formula is expressed as follows.

(C−c _w ) ₆₆₀ = β (phytoplankton concentration) where β is a proportional coefficient Here, since (c−c _w ) ₆₆₀ and (Log (1 / T)) have the following relationship, (c−c _w ) is calculated from the absorbance (Log (1 / T)).
₆₆₀ can be requested.

(C−c _w ) ₆₆₀ = (2.3 / L) * (Log (1 / T)) where L: optical path length (0.1 m) is used, and from FIG. 3 and FIG. , And the proportional coefficients β and δ in the formulas were the following values in the case of Skeletonema.

β = 4.6 * 10 ^-5 (m ^-1 / cells) δ = 30 * 10 ^-5 (mV / cells) Next, chlorella was cultured in the same manner, and chlorophyll-a, cell number, Absorbance and fluorescence intensity were measured. The results are shown in FIG. 5 and FIG.

5 and 6, the proportional coefficients β and δ were as follows in the case of chlorella.

β = 0.69 * 10 ⁻⁵ (m−1 / cells) δ = 10 * 10 ⁻⁵ (mV / cells) In addition, the chlorella culture tank has 100 m
A bottle was placed at the bottom of the aquarium to collect detritus. Detritus and chlorella were mixed in this sample, but as a result of microscopic observation, floc-shaped detritus was mainly present, and the concentration of chlorella mixed therein was 15.5 * 10 ⁴ cells / ml. The data of the detritus sample is shown below.

Chlorella cell count 15.5 * 10 ⁴ cells / ml 660nm absorbance 1.50 (10cm cell) Fluorescence intensity 18mV Suspension dry weight concentration (SS) 248mg / l Absorbance by Chlorella based on 660nm absorbance and fluorescence intensity data of the above detritus sample water When the intensity was subtracted, the volume extinction coefficient (c−c _w ) ₆₆₀ due to detritus and the fluorescence intensity were as follows.

(C−c _w ) by detritus ₆₆₀ = 1.50 * 2.3 / 0.1− (0.69 * 10 ⁻⁵ * 15.5 * 10 ⁴ ) = 33.43 m ⁻¹ Fluorescence intensity by detritus = 18−15.5 * 10 ⁴ * 10 * 10 ⁻⁵ = 2.5 mV Here, the ratio of the volume extinction coefficient at 660 nm to the amount of fluorescence per unit is defined as a ratio (τ), and Table 2 shows that τ of the sample water of each of the skeletonet, chlorella and detritus is shown in Table 2.
(Τ = (c−c _w ) ₆₆₀ / fluorescence intensity (F)) was arranged.

As shown in Table 2, an important finding was obtained that the value of (τ) was very different between phytoplankton and detritus. Detritus showed a significant difference between 13.37 and live chlorella cells.

The dead phytoplankton cells are degraded by the rapid autolysis of the cells containing chlorophyll-a,
Eventually, the generation of fluorescence disappears, but (c−c _w ) ₆₆₀ is
It is an index that indicates the degree of transmission of the parallel light beam. It is evident from this experiment that there is little change depending on whether the phytoplankton is alive or dead, depending on the cell size (projected area) and concentration, and the value of τ is It also became clear that it depends on the type of phytoplankton.

 The following is a summary of the findings obtained above.

Assuming that the suspended substance is separated into detritus and phytoplankton, the volume extinction coefficient (c−c _w ) λ and the fluorescence intensity F can be expressed as follows.

(C−c _w ) _λ = α (detritus concentration) + β (phytoplankton concentration) where α and β are proportional coefficients Here, γ and δ are proportional coefficients, λ ₁ is a suffix indicating the excitation wavelength λ ₂ is the fluorescence receiving wavelength. Here, it has been clarified that the fluorescence intensity coefficient γ of detritus is so small that it can be ignored. Can be approximated.

Further, it has become clear from the above that τ takes different values depending on the type of phytoplankton, so τ based on phytoplankton is expressed as follows.

From the formula, Here, the first term on the right side represents the volume extinction coefficient due to detritus, and the second term represents the volume extinction coefficient due to phytoplankton.

Therefore, if α and τ are determined in advance for the sample water to be measured, By measuring, the detritus concentration and the phytoplankton concentration of the test water can be continuously measured.

Also, as described below, the increase and decrease of phytoplankton in the sea area, Can be obtained directly from the slope of the correlation, and the detritus relative concentration can be measured using this.

(Example 2) Based on the above-described measurement method, an apparatus shown in Fig. 1 was produced in order to perform a verification test in a general sea area.

FIG. 1 is an explanatory view showing an outline of a measuring apparatus. In the figure, one of the light sources (1) is changed in parallel by a lens system (2) and is emitted from a light exit window (6) into a sample (water). Irradiated. The emitted light is attenuated due to scattering by suspended matter in the sample and absorption by dissolved organic matter, and the light-receiving window (1
4), lens system (15) pinhole filter system (1
By 6), light of a predetermined wavelength reaches the photodetector (17). From the output of (17) and the output of (5), (c−c _w ) _λ
Is calculated.

On the other hand, light for measuring fluorescence passes from the light source (1) through the lens system (3), and only light of the excitation wavelength λ is emitted from the emitted light (7) by the filter (4). Fluorescence generated by the excitation light passes from the sample window (13) through the fluorescence entrance window (8), and light other than a predetermined wavelength is filtered by the filter system (9).
And only the necessary fluorescence passes through the lens system (10) and is detected by the fluorescence receiving unit. The luminance change of the light source is always corrected from the output of the light source photodetector (5). (5),
From the outputs from (11) and (17), the phytoplankton concentration and the detritus concentration are continuously and automatically measured by the above-described measuring method.

(Example 3) The above equipment was installed at the mouth of the Sumida River (water depth 1m),
The volume extinction coefficient (λ = 660 nm) and the fluorescence intensity (excitation light intensity 436 nm, fluorescence wavelength 685 nm) were continuously measured for 6 days from August to August 30. FIG. 7 and FIG. 8 show the time-dependent changes of the volume extinction coefficient and the fluorescence intensity over 24 hours on August 25 and August 28 of this measurement. In the figure, ● represents the fluorescence intensity and × represents the volume extinction coefficient.

 The water quality changes on both days showed very different patterns.

Looking at the change on 8/25, (c−c _w ) ₆₆₀ shows a large increase, but there is almost no change in the fluorescence intensity, and (c−c _w ) ₆₆₀
Changes drastically and turbidity peaked at 12:00. (C-
c _w ) Despite the change of ₆₆₀ , the fluorescence intensity has hardly changed. On the other hand, on August 28, the change in (c−c _w ) _{660 and} the change in the fluorescence intensity fluctuated in a linked manner.

Next, FIG. 9 shows a scatter diagram of (c−c _w ) ₆₆₀ and the fluorescence intensity. In the figure, Δ indicates data on 8/25, and ● indicates data on 8/28. The data of 8/28 is distributed almost linearly in FIG. 10, and when the regression line is calculated, the following line is obtained.

Comparing the equations, one obtains τ = 0.163.
This value is almost equal to the value of skeletonema in the culture experiment (Example 1). In Example 1, it is clear that the τ value of phytoplankton shows a constant value depending on the type. In the mirror result, the dominant species was skeletonema, which was the same type of plankton as examined in Example 1. In the data of 8/28, by detritus (c
−c _w ) ₆₆₀ was almost constant at 2.6, and it is considered that (c−c _w ) ₆₆₀ due to phytoplankton changed significantly.

FIG. 10 shows the fluorescence intensity and chlorophyll-
3 shows a diagram illustrating the correlation of a. As shown in the figure,
There is a good correlation between 0.95 and the fluorescence intensity and chlorophyll-a, and it is clear that the fluorescence intensity indicates an increase or decrease in the phytoplankton concentration.

Next, on August 25, the dominant species of phytoplankton is skeletonema, and the following formula is obtained from the value of τ = 0.163 already obtained.

As shown in Example 1 above, if τ based on phytoplankton in the measurement water area is determined in advance, Can be continuously measured from the continuously measured values of the detritus relative concentration {α (detritus concentration)}.

In addition, for example, a suspension dry weight concentration (SS) is taken as an index of the detritus concentration in advance, and is substituted into the expression to obtain the following expression.

If this α is determined in advance by a calibration curve, the detritus concentration can be converted to the suspension dry weight concentration (SS), and the suspension dry weight concentration (SS) of detritus can be measured continuously. Can be.

[Effects of the Invention] As described above, the present invention determines α and τ for a sample water to be measured in advance. By measuring, the detritus concentration and the phytoplankton concentration of the test water can be separately measured continuously.

Also, due to the increase and decrease of phytoplankton in the general sea area, Can be obtained directly from the slope of the correlation of, and this can be used to measure the detritus concentration. This means that the concentration of generated soil particles and the like and the concentration of natural water, especially phytoplankton, can be measured separately by construction, and only the environmental impact of construction can be measured continuously. .

Further, the apparatus using the above-described method has another effect that it is possible to easily separate and measure the components of the suspended substance in the field.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a measuring device, FIG. 2 is a diagram showing a relationship between a volume extinction coefficient in a general sea area and a suspended matter dry weight concentration (SS), and FIG. Diagram showing the correlation between the number of cells and the absorbance (Log (1 / T)), FIG. 4 shows a diagram showing the correlation between the number of cultured skeletonema cells and the fluorescence intensity, and FIG. 5 shows the cells of the cultured chlorella FIG. 6 is a graph showing the correlation between the number of cells and the fluorescence intensity, FIG. 6 is a graph showing the correlation between the number of cells of cultured chlorella and the fluorescence intensity, and FIG. FIG. 8 is a diagram showing the time-dependent changes of the volume extinction coefficient and the fluorescence intensity on another measurement day at the same place as in FIG. 7, and FIG.
A diagram showing the distribution of the fluorescence intensity with (c−c _w ) _{660 in} FIG.
The figure is a diagram showing the correlation between the fluorescence intensity and chlorophyll-a. In the figure, (1) is a light source, (2), (3), (10),
(15) is a lens, (4), (9) and (16) are filters,
(5) is a light source light detector, (6) is a parallel light exit window, (7)
Is the excitation light emission window, (8) is the fluorescence reception window, (11) is the fluorescence detector, (12) and (13) are the water to be measured, (14) is the transmitted light reception window, and (17) is the transmitted light It is a detector.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-71339 (JP, A) JP-A-60-100033 (JP, A) JP-A-2-190746 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) G01N 21/00-21/74

Claims (3)

(57) [Claims] 1. A method for measuring a suspended substance in which the indicator concentration of a suspended substance is regarded as two types, namely, a phytoplankton index concentration and a detritus index concentration which is another suspended substance. Ratio between the volume extinction coefficient of phytoplankton and the indicator concentration of phytoplankton (τ) and the proportional coefficient of the indicator concentration of detritus to the volume extinction coefficient of detritus (α)
The volume extinction coefficient of the measured water and the phytoplankton index concentration are measured, and the volume extinction coefficient of the phytoplankton is obtained from the measured phytoplankton index concentration, A method for separating and measuring suspended substances, wherein a detritus volume extinction coefficient is determined from a difference between a volume extinction coefficient and a volume extinction coefficient of the phytoplankton, and a detritus index concentration is determined. 2. The method for separating and measuring a suspended substance according to claim 1, wherein the phytoplankton indicator concentration is a fluorescence emission intensity. 3. The method for separating and measuring a suspended substance according to claim 1 or 2, wherein the ratio (τ) between the volume extinction coefficient of phytoplankton and the indicator concentration of phytoplankton, which is determined in advance, is measured. A method for separating and measuring suspended substances, wherein the method is obtained from a slope of a correlation between a phytoplankton index concentration or a fluorescence emission intensity of water and a volume extinction coefficient of water to be measured.