KR101003755B1 - Method for analysis of pollutant transport in soil - Google Patents

Abstract

According to the present invention, an upper opening 101 and a lower opening 102 are formed, and a column 100 having an accommodation space of a soil sample therein; A resistor having a pair of potential electrodes 210 mounted on the inner surface of the column 100 in a vertical direction and a pair of current electrodes 220 mounted on the upper and lower sides of the pair of potential electrodes 210, respectively. Measuring unit 200; An inflow water supply unit 120 for introducing contaminants through the lower opening 102; By presenting a test apparatus for the analysis of the movement of soil in the ground containing; effluent collection unit 110 for collecting the effluent sample outflow from the upper opening 101, it is possible to quickly determine the result without chemical analysis of the effluent This allows for more direct and realistic simulation of pollutant behavior in soils and groundwater.

Soil, pollution, electrode

Description

METHODS FOR ANALYSIS OF POLLUTANT TRANSPORT IN SOIL

1 to 4 show an embodiment of a test apparatus according to the present invention,

1 is a side view of a first embodiment;

2 is a partially enlarged view of the first embodiment;

3 is a configuration diagram of a second embodiment.

4 is a configuration diagram of a third embodiment.

5 is a circuit diagram for explaining the principle of the test apparatus according to the present invention.

DESCRIPTION OF REFERENCE NUMERALS

100: column 101: upper opening

102: lower opening 110: outflow water collecting portion

120: inflow water supply unit 200: resistance measurement unit

210: pair of potential electrodes 220: pair of current electrodes

TECHNICAL FIELD The present invention relates to the field of environment, and more particularly, to a method for analyzing the behavior of pollutants in soil and a test apparatus used therein.

In the geoenvironmental field, not only the type and amount of pollutants polluting the soil, but also the interpretation of the pollutant behavior in the soil is of great concern.

In order to simulate the movement of contaminants in the soil, a test method has been used to measure the movement of contaminants by taking soil samples, filling the columns, and injecting the contaminants.

This is a one-dimensional model test that attempts to determine the migration path, time taken for migration, concentration at the point of interest, and duration of pollutants generated by site conditions.

However, this conventional technology requires repeated sampling of the effluent, requires a lot of time to analyze the components of the collected effluent sample, and effluent sampling is simply performed at one point. It has been pointed out as a problem in that there is a limit in identifying an accurate movement characteristic.

The present invention has been made in order to solve the above problems, it is possible to quickly grasp the results without chemical analysis or electrical conductivity measurement of the effluent, pollution to enable more direct and realistic simulation of the behavior of pollutants in the soil The object of the present invention is to provide a test apparatus for moving ground analysis of materials and a method for moving ground analysis of pollutants using the same.

In order to achieve the object as described above, the present invention, the upper opening and the lower opening is formed, the column formed therein the receiving space of the soil sample; A resistance measuring unit including a pair of current electrodes mounted on an inner surface of the column in a vertical direction, and a pair of potential electrodes mounted on upper and lower sides of the pair of current electrodes; An inflow water supply unit for introducing contaminants through the lower opening; It proposes a test apparatus for the ground movement analysis of contaminants, including; effluent collection unit for collecting the effluent sample flowing out from the upper opening.

The column has a circular longitudinal section, and the current electrode and the potential electrode are preferably mounted in parallel in an arc shape.

An angle formed between the center of the column and both ends of the current electrode and the potential electrode is preferably 30 ° or more and 180 ° or less.

The distance between the current electrode and the potential electrode is preferably 5% or more and 10% or less of the diameter of the column.

Preferably, the resistance measuring unit is provided with a plurality in the vertical direction of the column.

The distance between the plurality of resistance measuring units is preferably 20% or more and 50% or less of the length of the column.

On the other hand, the present invention is a soil analysis method of the soil using the test device, the soil sample filling step of filling and compacting the soil sample in the column; An influent supply step of introducing contaminants through the influent supply unit; A resistance measuring step of measuring resistance by applying electricity to the current electrode and measuring a potential by the potential electrode in the plurality of resistance measuring units; A concentration change rate calculation step of calculating a relative rate of change of concentration with time from the measured resistance is presented.

The contaminant used as the influent is preferably an inorganic contaminant having high electrical conductivity due to the ionic phase in the solution.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, in the test apparatus for moving ground analysis of contaminants according to the present invention, an upper opening 101 and a lower opening 102 are basically formed, and a receiving space of a soil sample is formed therein. Formed column 100; A resistor having a pair of potential electrodes 210 mounted on the inner surface of the column 100 in a vertical direction and a pair of current electrodes 220 mounted on the upper and lower sides of the pair of potential electrodes 210, respectively. Measuring unit 200; An inflow water supply unit 120 for introducing contaminants through the lower opening 102; It is configured to include; and the effluent collection unit 110 for collecting the effluent sample flowing out of the upper opening 101.

That is, the test apparatus according to the present invention adopts the principle of electrical resistivity exploration (ground environmental physics exploration, 2000), which measures the potential difference generated by the direct current or the low frequency alternating current flowing into the soil. This is the theory of determining the resistivity distribution and analyzing the underground structure.

The present invention is to propose a method to determine the movement of contaminants by attaching a horizontal electrode to the column based on the electrical properties of the soil, using the test device as described above, and to directly measure the electrical resistivity of the soil This method has the advantage of predicting the movement of pollutants without sampling the pore water.

Hereinafter, with reference to Figure 5 will be described in detail the principle of the test apparatus and the analysis method according to the present invention.

As the electrical resistivity unit, Ωm is usually used. The inverse of the resistance is conductance, so the conductivity is also the inverse of the electrical resistivity. Ω ⁻¹ / m or S / m is commonly used as a unit of electrical conductivity.

The purpose of electrical exploration, like electrical circuits, is to measure the potential difference between two points.

,

는 다음과 같이 식 1,2에 의해 나타낼 수 있다.5 shows two potential electrodes P1 and P2 and two current electrodes, the potentials generated at each potential electrode.

,

Can be represented by Equation 1,2 as follows.

From the above equation, the potential difference can be obtained as follows.

The electrical resistivity survey is to determine the electrical resistivity by measuring the potential difference.

The parentheses term in this equation is often called the geometric factor G, which can be rewritten as

The resistance value used in this column experiment is the value before the above-mentioned distance coefficient is multiplied.

On the other hand, the actual groundwater does not move without the water gradient, but the various solutes introduced into the groundwater environment may be moved by the concentration gradient or the temperature gradient.

As such, contaminants introduced into the groundwater environment tend to disperse and diffuse away from the migration path that is expected to flow along the groundwater gradient due to advection. This is called hydrodynamic dispersion.

Thus, on a microscopic scale, contaminants are shifted by advection and hydraulic dispersion mechanisms for groundwater gradients, and their concentrations change gradually.

In general, the hydraulic dispersion coefficient in the longitudinal direction is proportional to the n power of the pore velocity, as shown in Equation 6.

As a result of the test invention, the range of n value is generally about 1 to 2 and n = 1 in the granular porous medium. Therefore, Equation 6 is usually expressed as follows.

here,

: 수리분산계수

: Hydraulic variance coefficient

: 지하수의 공극유속

: Pore velocity of groundwater

: 분산지수

: Dispersion Index

: 분자확산계수

: Molecular diffusion coefficient

를 이류에 의한 역학적인 분산(mechanical dispersion)이라고 하고

를 용질의 열역학적인 에너지에 의한 발생되는 분자확산(molecular diffusion)이라 하며, 미시적 규모에서 역학적인 분산현상은 공극 내에서 용질의 속도차, 즉 공극의 불균질성에 의해 일어난다.In this expression

Is called mechanical dispersion

Is called molecular diffusion caused by the thermodynamic energy of the solute. On the microscopic scale, the mechanical dispersion is caused by the difference in the velocity of the solute, ie, the heterogeneity of the pore.

In fact, the diffusion of the solute occurring in the fluid can be expressed by Fick's first and second law as follows.

Where Do is the ion diffusion coefficient and F is the flux of solute in the fluid.

Various contaminants introduced into the groundwater environment are reduced or diluted in solution concentration in the solution by the action of adsorption, ion exchange, chemical precipitation, redox reaction, ionization, etc. on the surface of the aquifer.

In the present invention, it is assumed that there is no delay caused by adsorption and biochemical reactions.

When the groundwater system is homogeneous, isotropic, and saturated, and the groundwater flowing in the groundwater system is rectified, the equation of the unreacted solute in the one-dimensional system (1D) can be simply expressed as in Equation 10.

here,

: 유선방향의 좌표

: Coordinate in the wire direction

: 종분산계수

: Dispersion coefficient

: 유선방향에서 지하수의 공극유속

: Pore velocity of groundwater in streamlined direction

: 종분산지수

Species dispersion index

Based on the above concept, we will analyze the hydraulic dispersion governing formula and the movement of pollutants in the column.

In the present invention, it was assumed that there is no influence of the delay due to the wall friction in the column and the behavior due to the adsorption of sand during the movement of the pollutants.

Hereinafter, specific examples of the test apparatus according to the present invention employing the above principles will be described.

The column 100 may take any cross-sectional phenomenon, but in order to allow the current to flow evenly into the soil sample filled therein, the longitudinal section of the column 100 is circular, as shown in FIG. 210 and the current electrode 220 preferably take a structure mounted in parallel in an arc shape.

The angle formed between the center of the column 100 and the both ends of the potential electrode 210 and the current electrode 220 has an electrical influence on each electrode based on the basic theory of electric resistivity survey (ground environmental physical survey, 2000). To the extent that it is not within the range, it is necessary to take into account that the soil has a minimum volume of soil within the measurement range.

As a result, the angle formed between the center of the column 100 and the ends of the potential electrode 210 and the current electrode 220 was found to be preferably 30 ° or more and 180 ° or less. In FIG. It is shown.

 This is because a sufficient contact area between the filled soil and the electrode should be secured to minimize the contact resistance.

The distance between the potential electrode 210 and the current electrode 220 should also consider the same factors as in the case of the angle between the above electrodes, but the experimental results show that it is preferably 5% or more and 10% or less of the diameter of the column 100. In the embodiment of FIG. 2, when the diameter of the column 100 is 40 mm, the distance between the potential electrode 210 and the current electrode 220 is set to 3 mm.

In the resistance measuring unit 200 constituted by the potential electrode 210 and the current electrode 220, a plurality of resistance measuring units 200 are mounted along the vertical direction of the column 100, which is a direction in which pollutants move. It is preferable in that it is.

The distance between the plurality of resistance measuring units 200 also need to be limited for the same reason as the angle and the distance between the upper electrodes, and as a result of the experiment, it was found that it is preferably 20% or more and 50% or less of the length of the column 100. .

Hereinafter, specific examples of the method for moving the soil in the ground using the test apparatus according to the present invention will be described in detail.

In the ground movement analysis method of contaminants according to the present invention, the soil sample filling step of filling and compacting the soil sample in the column 100; An inflow water supply step of introducing contaminants through the inflow water supply unit 120; A resistance measuring step of measuring resistance by applying electricity to the potential electrode 210 in the plurality of resistance measuring units 200 and measuring the potential by the current electrode 220; And a concentration change rate calculating step of calculating a relative concentration change rate with time from the measured resistance.

First, as shown in FIGS. 3 and 4, two columns having the same size (height: 400 mm and diameter: 40 mm) were fabricated, and each column was provided with three electrodes at equal intervals to analyze the movement of contaminants. Arranged.

The soil used as a sample was filled using Jumjin standard sand (24 hours post-drying), which is considered to have a uniform permeability coefficient and no adsorption of contaminants.

At this time, in order to simulate the condition of the soil in a certain condition to fill the column by the same compaction method to make a sample having the compaction characteristics as shown in Table 1.

division Column 1 Column 2 Weight (g) column 734 735 Column + Filling Soil 1956 1970 Column + Filling Soil + Water 2286 2297 Column dimension (length × diameter; cm) 40 × 5 40 × 5 Volume (cm3) Total volume of soil 785 785 Volume of gap in soil 330 327 Volume of clearance (ml) 330 327 Clearance 0.4 0.42 Water content (%) 27 26.5 Inflow Flow Rate (ml / min) 0.1 1.2 Measure frequency 1 kHz 1 kHz Measuring temperature (° C) 24.3 23.4

The electrode for measuring the resistance is composed of two current electrodes 220 and two potential electrodes 210, it was manufactured to have the same radius of curvature as the inner surface of the column.

This is for more accurate electrical measurement by maximizing the surface area of the sample in contact with the electrode and reducing the voids.

As shown in FIG. 2, the electrodes were arranged at a distance of 50 mm from the top and bottom of the column based on a column height of 400 mm so that the three electrodes had the same distance at 120 mm intervals.

In addition, the electrodes are manufactured to have a length of 20mm and a thickness of 2mm, and each electrode has a space of 3mm.

Based on the basic theory of electrical resistivity exploration, each electrode is considered to have the minimum volume of soil in the measurement range within the range that does not affect each other.

Samples in the column were both chopped by the same compaction method (10 cm intervals, 15 compactions with a compaction rod) using standard yarns ordered.

The number of the electrode is indicated by ○-○, the front number means the column number, the rear number is indicated by -1, -2, -3 in order based on the column top.

For example, the electrode at the top of column 1 would be 1-1.

First, prior to the experiment, both columns were packed and filled with the same compaction method using Jumunjin standard yarn, and as a result, almost similar water content, porosity, and void volume were obtained as shown in Table 1 above.

To completely saturate the column with deionized water, the deionized water was saturated with CO _{2 (g)} gas for 2 hours before entering the column and one pump per column was used.

CO _{2 (g)} is well soluble in deionized water, allowing full saturation of the soil.

0.002M Cl ⁻ was used as the influent, and inlet flow rate was set to 0.1 ml / min for column 1 and inlet flow rate to 1.2 ml / min for column 2.

The reason for using Cl ⁻ is because it is an unreactive substance that does not adsorb or chemically react with soil particles.

Resistance measurements were made using an LCR meter at 1 kHz at 10 minute intervals until a full breakthrough of Cl ⁻ occurred.

And the sampling of the effluent was set to be sampled at intervals in consideration of the flow rate of 0.1 ml / min and 1.2 ml / min using the Auto Sampler.

At this time, all the samples are numbered for each sample in order to compare with the breakthrough curve for the electrical resistivity.

Hereinafter, the test results by the test apparatus and the analysis method according to the present invention described above will be described.

When Cl ⁻ solution is introduced into a column saturated with DI water, the resistance measured at the electrode decreases drastically.

This indicates that Cl ⁻ is in an ionic state in the aqueous state, and these ions act as charge carriers, resulting in a decrease in the measured resistance value and an increase in electrical conductivity.

In the case of a column flowing 0.002M Cl ⁻ at a flow rate of 0.1 ml / min, a concentration history curve with elapsed time was shown in Table 1 above.

값을 의미하며, 각 전극에서 측정된 저항값 (그 역수인) 컨덕턴스(EC) 값으로 환산, 상대적인 농도변화율(C/C0)로 표현하여 농도이력곡선으로 나타낸 것이다.Where C / Co

It is a value, and it is expressed as a concentration history curve expressed as a relative concentration change rate (C / C0) in terms of conductance (EC) value of resistance value (inversely) measured at each electrode.

Where EC _t is the conductance of time t, EC _max is the maximum conductance value measured during the test time, and EC _min is the minimum conductance value measured during the test time.

As can be seen in Table 2, it was found that Cl ⁻ formed a distinct concentration history curve for each electrode in turn.

The time taken for the soil in contact with the electrode to saturate to 0.002 M Cl ⁻ can be understood as the time when C / C 0 has a value of 0.5.

That is, T1 (500 minutes) is electrode 1-3, T2 (1540 minutes) is electrode 1-2, and T3 (2600 minutes) is the time taken for the soil around electrode 1-1 to be completely saturated.

Of course, the value increases from T1 to T3 because the distance that the Cl ⁻ solution flowing from the lower opening of the column reaches the electrode increases.

It can be seen that the time between T1 and T2 is 1040 minutes and the time between T2 and T3 is 1060 minutes, indicating that the experiment shows reliable results.

Theoretically, if the distance between the electrodes 1-1, 1-2, 1-3 is equal to 120 mm and the inflow flow rate is constant, the values of (T2-T1) and (T3-T2) should be the same.

T4, T5, and T6 are the time from the first introduction of Cl ⁻ to the soil adjacent to the electrodes 1-1, 1-2, 1-3 in the column and the complete breakthrough.

This also shows the tendency of T6> T5> T4 due to the effects of advection and diffusion that can occur when the pollutants move in the column.

Table 3 shows the flow rate, flow rate, hydraulic dispersion coefficient, and crystal coefficient obtained by substituting the results of Table 2 into Equation 10.

As a result, it was confirmed that the flow rate and the hydraulic dispersion coefficient of the three electrodes were almost the same, and the crystal coefficient was close to 1.

Through this, it can be confirmed that the concentration history curve obtained based on the resistance value has high reliability.

Flow rate
v [cm / min] flux
Q [ml / min] Hydraulic variance coefficient
D [cm ² / min] Coefficient of determination
R ² 1-1 electrode 0.01322 0.1091 0.0007614 0.9999 1-2 electrodes 0.01278 0.1054 0.0008506 0.9997 1-3 electrodes 0.01152 0.0951 0.0006708 0.9996

Table 4 is a graph showing the relative concentration hysteresis curve with time variation after introducing 0.002M Cl ^- aqueous solution into column 2.

The conditions of column 2 were the same except that the influent flow rate was changed compared to column 1.

Similar to the test of column 1, the time taken for the soil to saturate within the range of the measuring electrode of column 2 tended to increase as it goes up from the bottom electrode.

That is, T1 (53 minutes) is electrode 1-3, T2 (140 minutes) is electrode 1-2, and T3 (215 minutes) is the time taken for the soil around electrode 1-1 to fully saturate.

Theoretically, the values of T1, T2, and T3 should also be 12-fold different, given that the influent flow rate is 12 times greater than that of column 1.

Comparing the T1, T2, and T3 values of column 1 and column 2 shows that the test showed reliable results.

As a result, in the analysis method according to the present invention, it was possible to grasp the movement of Cl ⁻ using the resistance value.

In addition, as a result of comparing the resistance values by saturating Cl ⁻ solution at various flow rates to correct the resistance values measured at the three electrodes, it was confirmed that T1, T2, and T3 were proportional to the flow rate, and thus the electrode error was very small.

Flow rate
v [cm / min] flux
Q [ml / min] Hydraulic variance coefficient
D [cm ² / min] Coefficient of determination
R ² 1-1 electrode 0.1098 0.9065 0.00656 0.9964 1-2 electrodes 0.1429 1.1798 0.01463 0.9993 1-3 electrodes 0.1591 1.3135 0.01516 0.9992

The numerical results shown in Table 5 also show that the three electrodes have high reliability with similar flow rates, flow rates, and hydraulic dispersion coefficient values.

T4, T5, and T6 are the time from the first introduction of Cl ⁻ to the soil adjacent to the electrodes 1-1, 1-2, 1-3 in the column and the complete breakthrough.

Both column 1 and column 2 show a tendency of T6> T5> T4, which shows that the effects of advection and diffusion that can occur when the pollutants move in the column can be identified.

Since the above has been described only with respect to some of the preferred embodiments that can be implemented by the present invention, the scope of the present invention, as is well known, should not be construed as limited to the above embodiments, the present invention described above It will be said that both the technical idea and the technical idea which together with the base are included in the scope of the present invention.

The present invention can quickly determine the results without chemical analysis of the effluent, the test apparatus for the movement analysis of soil and groundwater contaminants to more directly and realistically simulate the behavior of contaminants in the soil and the soil and using the same Provides a method for moving analysis of groundwater contaminants.

In the above example, in order to analyze the movement of Cl ^- material in the soil by using the resistance value, three integral electrodes are manufactured in the column to observe the movement of Cl ^- solution passing through the soil in the column based on the resistance value measured for each position. It was.

As a result. The breakthrough curve was obtained by converting the measured resistance value to the relative concentration change value.

The breakthrough curve obtained has the following meaning in analyzing the movement of contaminants in column experiments.

1) Breakthrough curve can be obtained more quickly without chemical analysis of effluent or measurement of electric conductivity.

2) Since the concentration breakthrough curve is obtained from the electrical resistivity of pollutants including soil, not runoff, the behavior of pollutants in the soil can be simulated more directly and realistically.

3) Analysis of concentration breakthrough curves obtained from the measured resistance values confirmed that dispersion and advection influenced the movement of pollutants.

In addition, in the present invention, by developing a new type of electrode and measuring the electrical resistivity value, the practicality and applicability of the electrode were proposed in a column experiment using the electrical resistivity.

Claims (8)

A column having an upper opening and a lower opening formed therein and having an accommodation space of the soil sample therein; A resistance measuring unit including a pair of current electrodes mounted on an inner surface of the column in a vertical direction, and a pair of potential electrodes mounted on upper and lower sides of the pair of current electrodes; An inflow water supply unit for introducing contaminants through the lower opening; And an effluent collecting part for collecting the effluent sample flowing out of the upper opening. The resistance measuring unit In the ground movement analysis method of contaminants using a test device equipped with a plurality in the vertical direction of the column, A soil sample filling step of filling and compacting a soil sample inside the column; An inflow water supply step of introducing contaminants through the inflow water supply unit; A resistance measuring step of measuring resistance by applying electricity to the current electrode and measuring a potential by the potential electrode in the plurality of resistance measuring units; A concentration change rate calculating step of calculating a relative rate of change of concentration with time from the measured resistance; Movement analysis method in the ground of the pollutant comprising a. The method of claim 1, The column is circular in cross section, The current electrode and the potential electrode in the ground movement of the pollutants, characterized in that mounted in parallel in the arc (弧) shape. The method of claim 2, And an angle formed between the center of the column and both ends of the current electrode and the potential electrode is 30 ° or more and 180 ° or less. The method of claim 2, The distance between the current electrode and the potential electrode is 5% or more and 10% or less of the diameter of the column in the soil movement analysis method. delete The method of claim 1, The distance between the plurality of resistance measuring units An analysis method for moving soil in the ground, characterized in that less than 20% to 50% of the length of the column. delete The method of claim 1, The contaminant used as the inflow water is an inorganic contaminant present in the ionic phase in the solution, the soil movement analysis method.

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