CN106908447A - The determination method of DNAPL REV during long term migration in translucent particle material - Google Patents

Abstract

The invention provides a kind of determination method of DNAPL REV during long term migration in translucent particle material, the internal microstructure of translucent particle material is scanned by the microcosmic imaging technique of visible ray, so as to calculate the property such as porosity of material, then saturation degree, the interfacial area of DNAPL water of DNAPL are determined with light transmission method, is finally combined with relative gradient error.This method is integrated with the strong point of various microcosmic scanning techniques, compared with congenic method, this method is more quick, convenient, economical, without the condition that radiology devices etc. are complicated, it is easy to operate, high precision, can carry out Accurate Determining to the REV in porous media internal flow transition process, have stronger applicability in terms of the research of material internal migration mechanism, the accurate simulation of DNAPL long term migrations and reparation to DNAPL.

Description

The determination method of DNAPL REV during long term migration in translucent particle material

Technical field

The present invention relates to a kind of heavy nonaqueous phase organic matter, and in particular in a kind of heavy nonaqueous phase organic pollution transition process Typical unit body determination method.

Background technology

Water is the indispensable valuable source that our mankind depend on for existence and development, and underground water is the important set of water resource It is the important water source of our domestic waters and industrial water into part, there is irreplaceable work to economic sustainable development With.Underground water is easy to exploitation, and compared with surface water, exploitation is convenient, and with low cost, safe coefficient is high, and water quality is preferably, will not Easily it is contaminated as surface water, the economic benefit that it brings is bigger, therefore underground water is served in human social development Important function.In wherein weighing nonaqueous phase pollutant (dense non-aqueous phase liquid, DNAPL) and being underground water Common contaminant, its density ratio water is big, and toxicity is higher, and such as tetrachloro-ethylene (PCE) and trichloro ethylene (TCE) are put into state of the U.S. In 129 kinds of priority pollutants " blacklist " that Environmental Protection Agency of family announces.Due to DNAPL stable chemical natures and solubility is low, So after DNAPL enters water-bearing layer, DNAPL can be mutually stranded in the hole in water-bearing layer as independent in ground water regime. Additionally, the density ratio water of DNAPL is big, the bottom to water-bearing layer can be reached up to the migration of water-bearing layer deep always, and containing Assemble to form pollution pond in the top of the hypotonicity lenticular body of water layer.Therefore, once DNAPL enters ground water regime, remain in The DNAPL of the dispersity in water-bearing layer and the pollution pond being gathered into can turn into the long-time pollution source of underground water, to underground water source Huge harm is caused with belowground ecosystem.But long term migration processes of the DNAPL in water-bearing layer is sufficiently complex, so grinding Study carefully the typical unit body (REV) in the long-term complexity transition processes of DNAPL and analyze REV change with time it is very necessary.

Water and pollutant are all based on the continuous medium hypothesis of REV in the simulation of Migration in Porous Media, thus REV for Measure and material internal the material transport simulation of porous media property are significant.In general, material character or material Material internal flow property can be divided into three intervals with the change of measurement scale：In the I of region, by the shadow of material microscopic property Ring, occur in that violent fluctuation；In region il, the fluctuation of material character gradually tends towards stability, minimum REV yardsticks (L_min) and Maximum REV yardsticks (L_max) be region II border.Maximum REV yardsticks (L is further increased above with measurement scale_max), The heterogeneous of macroscopic view is functioned to, and causes material character to reappear big fluctuation.As scientific and technological develops rapidly, X-ray, The non-intrusion type such as gamma-rays high precision technology is got in the application for determining the aspects such as material character, material internal fluid concentrations and REV Come more extensive.However, precision during in order to ensure X-ray or gamma-ray measurement, in measurement material sample usually require that it is very small, In order to X-ray, gamma-rays penetrable material, additionally, needing equipment, the more energy of complexity, radioactivity during operation in measurement Very risky, flow is numerous and diverse.Visible transmission imaging technique (the light transmission for occurring in recent years Visualization, LTV) application it is more and more extensive, but current visible transmission technology can only determine translucent particle The content of water, pollutant in material etc., the change to REV during DNAPL long term migrations cannot carry out quantification.

The content of the invention

Goal of the invention：The purpose of the present invention is to solve the shortcomings of the prior art, there is provided a kind of high precision and convenient fast The determination method of prompt DNAPL REV during long term migration in translucent particle material.

Technical scheme：The invention provides a kind of DNAPL, REV is really during long term migration in translucent particle material Determine method, comprise the following steps：

(1) by the full water of two-dimentional translucent particle material, visible ray penetrable material, CCD camera is made to receive transmitted light intensity；

(2) porosity of translucent particle material is calculated by the microcosmic imaging technique of visible ray；

(3) long term migration is carried out in DNAPL injections translucent particle material, visible ray penetrable material is persistently used during being somebody's turn to do And transmitted light intensity is received with CCD camera, saturation degree, the interfacial area of DNAPL- water of DNAPL are calculated with light transmission method；

(4) with relative gradient error to the saturation degree during DNAPL long term migrations, the interfacial area of DNAPL- water REV carries out quantitative assessment；

(5) REV is counted, the frequency and cumulative frequency of REV size distributions during analysis DNAPL long term migrations Change.

Further, step (1) loads the translucent quartz sand material of different-grain diameter in two-dimentional sandbox, then uses water saturation Quartz sand material, is irradiated so that visible ray penetrable material, in the opposite side of sandbox CCD phases with visible ray from the side of sandbox Machine receives transmitted light intensity.

Further, step (2) calculates the hole of translucent particle material according to the relation between porosity and transmitted light intensity Porosity：

lnI_s=β+n ξ

Wherein, I_sIt is the transmitted light intensity after visible ray penetrates the translucent particle material of full water,

The porosity of the translucent particle material in each pixel can quantitatively be calculated by above formula.

Further, step (3) calculates the saturation degree of DNAPL with light transmission method：

Wherein, S_oilIt is the saturation degree of DNAPL, I_oilBe two-dimentional translucent quartz sand completely by DNAPL saturations when transmission Light intensity value, I is current transmitted light intensity；I_oilIt is calculated as：

Wherein, I_dIt is the transmitted light intensity values under the conditions of translucent particle material is completely dried, τ_w,oIt is between water and DNAPL The transmissivity at interface, τ_s,aIt is the solid phase particles of material and the transmissivity of Air Interface, α_oilIt is the absorptivity of DNAPL, k_oIt is Hole sum on Two-dimensional Porous Medium thickness, d_oThe average diameter of solid phase particles.

Further, on a microscopic scale, translucent particle material is that hole by solid phase particles and between them is constituted, The therefrom research unit of an optional equilateral triangle, the porosity and pore area of this unit are respectively：

Wherein, R_VIt is the mean radius of solid phase material particle, A is the gross area of triangular element, A_pIt is the hole in unit Area；

Hole in unit is approximately a circle, this diameter of a circle λ_lFor：

For the fluid in granular materials, fluid can not only flow through the middle hole of triangular element, and can flow through Space between solid phase particles；Therefore, pore diameter is diameter of a circle λ_lWith solid phase particles clearance distance Δ L_gAverage value：

Wherein, L₁It is the length of side of triangular element, Δ L_gIt is the distance in solid phase particles gap；

In the microcosmic imaging technique of visible ray, the translucent particle material in each pixel is layered distribution, hole with Solid phase particles from two-dimentional translucent particle material apart from one another by taking up an official post and take a cross-sectional area A_oInfinitesimal infinitesimal, hole Average diameter d_o, hole number k_o, solid phase particles average diameter d_sWith the number k of solid phase particles_sMeet following relation：

nA_oL_T=A_ok_od_o

Wherein, A_oIt is the cross-sectional area of solid phase particles；

Therefore, the hole sum k on Two-dimensional Porous Medium thickness_oCan be calculated by above formula；

After calculating hole sum and the pore diameter in each pixel, it is assumed that DNAPL is on each pixel average mark In all holes, in cubical shape, cubical cross-sectional area is approximately the cross-sectional area of each pixel to cloth, therefore The cubical length of DNAPL in each hole can be calculated, the surface area and pixel of DNAPL in each hole is then calculated The total surface area of DNAPL in upper all holes；The surface area of DNAPL can be approximately the interfacial area between DNAPL and water, The surface area of DNAPL is standardized divided by the volume of measuring system to interfacial area between DNAPL- water, and unit is cm^-1。

Further, step (4) determines DNAPL saturation degrees and DNAPL- in translucent particle material with relative gradient error The REV yardsticks of interfacial area between water：

Wherein,It is relative gradient error,It is the parameter for needing assessment, such as saturation degree of DNAPL, i is the rectangular of measurement From small yardstick to the increased ordinal number of large scale, Δ L is each increased scale size of cuboid grid yardstick to physique.

Further, in order to smooth relative gradient errorThe big ups and downs of curve are used so as to the yardstick of REV is recognized accurately 5 points of relative gradient error averagely recognize REV：

Wherein,It is 5 average values of relative gradient error, whenThe yardstick of REV has been reached during less than or equal to 0.2.

Beneficial effect：The present invention is using the microcosmic imaging technique of visible ray (light transmission micro- Tomography, LTM) scanning translucent particle material microstructure, determine the property such as porosity of material, then use up Method (Light transmission visualization, LTV) determines saturation degree, the boundary of DNAPL- water of DNAPL in material Face area, finally determines the change of the REV during DNAPL long term migrations with relative gradient error；This method is quick, convenient, Economy, without the condition that radiology devices etc. are complicated, easy to operate, high precision can be migrated to porous media internal flow REV in journey carries out Accurate Determining, in the essence repaired in the research of material internal migration mechanism, DNAPL long term migrations to DNAPL Really the aspect such as simulation has stronger applicability.

Brief description of the drawings

Fig. 1 is the installation drawing of the microcosmic imaging technique of visible ray (LTM) and light transmission method (LTV)；

The two-dimentional sandbox of the translucent quartz sand of different-grain diameter is loaded in Fig. 2 (a) experiments；The porosity of (b) LTM technical limit spacings Distribution；(c) material character with yardstick change curve；D () is used to assess the cuboid grid of REV yardsticks；

Fig. 3 is the assessment result of translucent quartz sand porosity REV：The frequency of (a) translucent quartz sand porosity REV point Cloth；Relation of (b) the translucent quartz sand porosity REV smallest dimensions between average diameter of particles；

Fig. 4 be during whole long-term experiment PCE in saturation distribution not in the same time and 30 observation stations chosen H (), SA01-05 belongs to the observation station in the pollution pond accumulated on lenticular body A, SB01-05 belongs to the pollution pond accumulated on lenticular body B Observation station, SC01-05 belong on lenticular body C accumulate pollution pond observation station, SD01-05 belong on lenticular body D accumulate The observation station in pond is polluted, SE01-05 belongs to the observation station in the pollution pond accumulated on lenticular body E, and SF01-05 belongs to from discrete state The observation station chosen in PCE Pollution Plumes；

Fig. 5 is change of the DNAPL saturation degrees with measurement scale；

Fig. 6 is the relative gradient error of DNAPL saturation degrees with the change of measurement scale；

Fig. 7 is the REV smallest dimensions of DNAPL saturation degrees at 30 observation stations during whole long-term experiment with the change of time Change；

Fig. 8 is the frequency distribution of the REV smallest dimensions of the PCE saturation degrees during whole long-term experiment not in the same time；

Fig. 9 is the cumulative frequency point of the REV smallest dimensions of the PCE saturation degrees during whole long-term experiment not in the same time Cloth；

Figure 10 be DNAPL- water between interfacial area with measurement scale change；

Figure 11 be DNAPL- water between interfacial area relative gradient error with measurement scale change；

Figure 12 be during whole long-term experiment at 30 observation stations between DNAPL- water interfacial area REV smallest dimensions Change with time；

Figure 13 be during whole long-term experiment not in the same time between DNAPL- water the REV smallest dimensions of interfacial area frequency Rate is distributed；

Figure 14 be during whole long-term experiment not in the same time between DNAPL- water the REV smallest dimensions of interfacial area it is tired Product frequency distribution.

Specific embodiment

Technical solution of the present invention is described in detail below, but protection scope of the present invention is not limited to the implementation Example.

Embodiment：A kind of heavy nonaqueous phase organic pollution (DNAPL) is during long term migration in translucent particle material The confirmation method of typical unit body (REV), concrete operations are as follows：

As shown in figure 1, to the translucent quartz sand that different-grain diameter is loaded in a two-dimentional sandbox, then with water saturation, Sandbox side visible light source irradiates heterogeneous translucent quartz sand so that visible ray penetrable material, opposite side CCD camera Receive optical signal transmissive.Then DNAPL is made heterogeneous semi-transparent to DNAPL is injected in sandbox by the injection needle at the top of sandbox Long term migration is carried out in alum sand, visible light source sends visible ray penetrable material, CCD camera reality always in whole experiment process When monitor optical signal transmissive.

When light penetrates translucent particle material, according to Fidel's law, transmitted light intensity is：

I=CI₀(∏τ_j)exp(-∑α_id_i) (1)

Wherein, I is the transmitted light intensity after light wears translucent particle material, I_oIt is the intensity of light source, C is that correction visible ray is saturating Penetrate the parameter of error, τ_jIt is the light transmission at interface between i phases and i+1 phases, α_iIt is the absorption coefficient of light of i phases, d_iIt is the thickness of i phases Degree.

In long-term transition process is carried out during DNAPL is expelled to translucent particle material, light penetration thickness is L_TBag During two-dimentional translucent particle material containing solid phase particles, liquid phase water and DNAPL, transmitted light intensity is：

Wherein, d_oIt is the average diameter of hole, k_oIt is number that light penetrates hole on path, k_oilIt is that two dimension is translucent porous The medium hole that direction is filled by DNAPL on thickness sum, d_sIt is the average diameter of solid phase particles, k_sIt is that light is penetrated on path The number of solid phase particles,It is the transmissivity at interface between solid phase particles and liquid phase water,It is liquid phase water and oil phase DNAPL Between interface transmissivity, α_sIt is the absorption coefficient of light of solid phase particles, α_oilIt is the absorption coefficient of light of oil phase DNAPL.

When the hole of translucent particle material is completely by water saturation, transmitted light intensity I_sFor：

When the hole of translucent particle material is completely by DNAPL saturations, transmitted light intensity I_oilFor：

(3) formula substitution (4) formula can be obtained into I_oilWith I_sBetween relation：

(4) formula substitution (2) formula can be obtained into I and I_oilBetween relation：

(5) formula is substituted into (6) formula can obtain the computing formula of DNAPL saturation degrees, that is, light transmission method (LTV) technology：

Wherein, S_oilIt is the saturation degree of DNAPL；(7) I in formula_oilCan be calculated with equation below：

Wherein, I_dIt is transmitted light intensity when translucent particle material is completely dried, τ_s,aIt is the solid phase particles and air of material The transmissivity at interface.

The property of translucent particle material is before DNAPL is injected into sandbox, when translucent particle material is in water-saturated state Measured with the microcosmic imaging technique of visible ray, now transmitted light intensity calculates such as (3) formula.Take up an official post from two-dimentional translucent particle material and take one Individual infinitely small (the A of cross-sectional area_o→ infinitesimal 0), it is assumed that the solid phase particles and hole of material are with each other on the propagation path of light Every in layered distribution, thus hole average diameter d_o, hole number k_o, solid phase particles average diameter d_s, solid phase particles Number k_sWith the thickness L of translucent particle material_TMeet following relation：

nA_oL_T=A_ok_od_o (10)

k_sd_s+k_od_o=L_T (11)

Wushu (10) and formula (11) substitute into formula (3) and obtain the formula that LTM calculates translucent particle material porosity：

lnI_s=β+n γ (12)

WhereinWhen it is determined that parameter beta and ξ numerical value after, in each pixel half The porosity of transparent grain material just can quantitatively be calculated by formula (12).

On a microscopic scale, translucent particle material is that hole by solid phase particles and between them is constituted, such as Fig. 1 institutes Show, therefrom the research unit of an optional equilateral triangle, the porosity and pore area of this unit are respectively：

Wherein, R_VIt is the mean radius of solid phase material particle, A is the gross area of triangular element, A_pIt is the hole in unit Area.

Hole in unit is approximately a circle, this diameter of a circle λ_lFor：

For the fluid in granular materials, fluid can not only flow through the middle hole of triangular element, and can flow through Space between solid phase particles, as shown in Figure 1.Therefore, pore diameter is diameter of a circle λ_lWith solid phase particles clearance distance Δ L_g's Average value：

Wherein, L₁It is the length of side of triangular element, Δ L_gIt is the distance in solid phase particles gap.

In LTM technologies, each pixel can approximately be regarded as infinitesimal, the translucent particle material in each pixel is layer Shape distribution, hole is with solid phase particles apart from one another by DNAPL is evenly distributed in this some holes in the trnaslucent materials of each pixel In gap.Pore diameter and hole number can be calculated by (18) formula and (10) formula, and then the saturation computation based on DNAPL goes out Interfacial area between DNAPL and water, and interfacial area between DNAPL- water is standardized with the volume of measuring system, i.e., Interfacial area A between DNAPL- water_OWRefer to the ratio of contact area and the material volume for determining between DNAPL- water.

The property of fluid is shown in Fig. 2 c as measurement scale changes in the property or material of porous media, and wherein curve can be drawn It is divided into three intervals.When measurement scale is very small, such as region I, property can occur violent with measurement scale increase Fluctuation；When measurement scale is located in the II of region, curve becomes relatively gentle, and measurement scale now is exactly the chi of typical unit body Degree；When measurement scale further increases into region III, larger fluctuation can be occurred by the influence curve of macroscopic heterogeneity and become Change.In order to accurately identify the yardstick of typical unit body, DNAPL saturations in translucent particle material are assessed with relative gradient error Interfacial area REV between degree and DNAPL- water：

Wherein,It is relative gradient error,It is the property for needing assessment, such as saturation degree of DNAPL, i is the rectangular of measurement Physique (Fig. 2 d) from small yardstick to the increased ordinal number of large scale, each increased scale sizes of cuboid grid yardstick of Δ L.

Further, since property often fluctuates acutely with the curve that measurement scale changes, it is accurate in order to smooth this fluctuation The yardstick of REV is identified, 5 points of present invention application relative gradient error averagely recognize REV：

Wherein,It is 5 average values of relative gradient error, whenThe yardstick of REV has been reached during less than or equal to 0.2.

Finally calculate saturation degree, the frequency distribution of the REV of the interfacial area of DNAPL- water during DNAPL long term migrations And cumulative frequency distribution, analyze REV and change with time.

The two-dimentional sandbox size of the present embodiment is 60cm (width) × 45cm (height), and sandbox thickness is 1.5cm, to by aluminium Framework and safety glass are constituted, such as Fig. 2 a, and to the translucent quartz sand that different-grain diameter is loaded in sandbox, that is used in experiment is various The property of the quartz sand of different-grain diameter is shown in Table 1：

The property of the translucent quartz sand of table 1

F20/30 mesh quartz sand is provided with using F70/F100, F70/ respectively as the background packing material in sandbox Five lenticular bodies of hypotonicity of the quartz sand filling of F80, F40/F60, F50/F70 and F30/F40 mesh.Additionally, sandbox Top and bottom are filled with hypotonicity thin layer to prevent water from being escaped from sandbox top bottom with the quartz sand of F70/80 mesh.In sandbox The flow rate of water flow in controlled level direction is maintained at 0.5 meter/day so that translucent quartz sand is completely in water-saturated state.Whole dress Put it is ready after, two-dimentional sandbox is placed on before visible light source and causes that visible ray is incident from the side of sandbox, in opposite side Transmitted light is received with CCD camera, the transmitted light intensity of the translucent quartz sand hole full of liquid phase water in hole, each pixel is obtained Infinitesimal can be considered as, then quantitative determined with the porosity of double suprasil sand of LTM methods, as a result such as Fig. 2 b.With phase The smallest dimension of the translucent quartz sand porosity REV determined to gradient error is as shown in figure 3, to the translucent of 1200 grids The REV smallest dimensions of quartz sand have carried out statistical distribution, such as Fig. 3 a.Transverse axis represents REV smallest dimensions in Fig. 3 a, and the longitudinal axis represents right The frequency answered, the REV smallest dimensions of porosity are distributed in the range of 0.0-12.0mm, are mainly distributed on 2.0-9.0mm, and approach Gaussian Profile, this is consistent with the rule of the most Gaussian distributed of the property in water-bearing layer in nature.REV smallest dimensions and particle The smallest dimension of relation such as Fig. 3 b, porosity REV between average diameter is presented significant positive correlation with average diameter of particles (p<0.05), and translucent quartz sand particle diameter it is bigger, for REV smallest dimensions distribution it is wider.

When DNAPL migration experiments start, to the PCE injected in two-dimentional sandbox in tetrachloro-ethylene (PCE), 80min 40mL At the uniform velocity in injection sandbox so that PCE long term migrations, whole transition process continues 1433min.PCE is satisfied with light transmission method (LTV) Quantified with degree, PCE saturation distributions such as Fig. 4, S in figure in whole experiment process_oilRepresent the saturation degree of PCE.PCE from After the decanting point on sandbox top enters into sandbox, infiltrated to bottom from the top of sandbox as water droplet under gravity, such as Shown in Fig. 4 (a).As PCE constantly infiltrates downwards migration, PCE reaches the top of lenticular body A.Because the pressure of PCE cannot overcome The hollow billet of weak infiltrative lenticular body A enters pressure, therefore PCE constantly accumulates to form pollution pond, such as Fig. 4 on lenticular body A tops (b).Then, PCE bypasses the edge of lenticular body A and continues to migrate downward into.When PCE reaches lenticular body B, C, the top of D and E, hair Give birth to similar pollution pond and formed and then bypass the phenomenon that lenticular body edge continues to migrate downward into.At the same time, in the horizontal direction In the presence of lateral stream, PCE is to be bypassed from the left side edge of lenticular body C, D rather than bypass right side edge, then PCE migrations Constantly accumulate to form pollution pond, such as Fig. 4 (d) to sandbox bottom and in bottom.After experiment carries out 80min, the migration of PCE becomes more Plus it is slow, such as Fig. 4 e-h, PCE Pollution Plumes almost do not change in prolonged transition process and are to maintain stable shape State, bottom PCE pollutions pond is further accumulated, while the PCE of sandbox top residual is then constantly reduced.

The translucent quartz sand of two dimension is split into 30 layers, 40 row, and the size of each grid is 0.015m × 0.015m.In Fig. 4 30 observation grids are chosen in (h) and is varied with measurement scale observing interfacial area between PCE saturation degrees, PCE- water, SA01- 05 observation station for belonging to the pollution pond accumulated on lenticular body A, SB01-05 belongs to the observation in the pollution pond accumulated on lenticular body B Point, SC01-05 belongs to the observation station in the pollution pond accumulated on lenticular body C, and SD01-05 belongs to the pollution pond accumulated on lenticular body D Observation station, SE01-05 belongs to the observation station in the pollution pond accumulated on lenticular body E, and SF01-05 belongs to dirty from discrete state PCE The observation station chosen in dye plumage.When determining REV yardsticks, cuboid grid (see Fig. 2 d) gradually increases since each net center of a lattice Plus, so as to calculate interfacial area and corresponding relative gradient error between the PCE saturation degrees of different scale, PCE- water.

30 PCE saturation degrees S of observation grid_oilThe curve changed as measurement scale L increases, such as Fig. 5 (a-f) institute Show, observation grid SA01-05, SB01-05, SC01-05, SD01-05, SE01-05 and SF01-05 be respectively selected from lenticular body A, B, In the PCE pollution ponds on C, D, E top and the PCE Pollution Plumes of discrete state.When measurement yardstick very little when, in material character with When in region I (Fig. 2 c) of measurement scale theory change curve, PCE saturation degrees S_oilCurve occurs in that many fluctuations.With measurement The increase of yardstick, PCE saturation degrees S_oilGradually tend towards stability, curve enters the REV platforms of region II.From observation grid SA01- 05th, the PCE saturation degrees S of SB01-05, SC01-05, SD01-05, SE01-05_oilWith REV platforms on the curve that measurement scale changes It is interval unobvious.With the further increase of measurement scale, PCE saturation degrees S_oilChange curve enters region III, starts to receive The influence of macroscopic heterogeneity is arrived.Generally speaking, the PCE saturation degrees S of all observation grids_oilWith measurement scale change curve On REV land regions II be all difficult identification, this causes that REV yardsticks are difficult to accurate evaluation.Additionally, in the lenticular body of different-grain diameter PCE pollute pond observation grid PCE saturation degrees S_oilThere are different features with the change curve of measurement scale, this shows can With the saturation degree of the saturation degree of the PCE according to coherent condition and the PCE of discrete state with the feature of measurement scale change curve come Judge that PCE is coherent condition or discrete state.

Obtain PCE saturation degrees S_oilIt is the first step for assessing REV with the change curve of measurement scale, then with formula (2- 19) PCE saturation degrees S is calculated_oilRelative gradient errorObtain PCE saturation degrees S_oilRelative gradient errorWith measuring scale The change curve of degree, so that REV platforms interval II is more obvious, be easier identification judge, as shown in Figure 6.Work as measuring scale When degree is smaller, relative gradient errorCurve have obvious fluctuation.As measurement scale gradually increases, relative error curve enters Enter region II (Fig. 2 c), now curve gradually tends towards stability and the stabilized platform of REV occurs.As shown in Fig. 6 (a-f), accumulate saturating Observation grid SA01-05, SB01-05, SC01-05, SD01-05 and SE01-05 in mirror body A, B, C, D and E in PCE pollutions pond REV stabilized platforms it is narrower, and the REV stabilized platforms of SF01-05 are then relatively wide, illustrate accumulation in hypotonicity lenticular body The REV in PCE pollutions pond is narrower, and be distributed in the translucent quartz sand of coarse granule the REV of the PCE Pollution Plumes in discrete state compared with It is wide.With PCE saturation degrees S as shown in Figure 5_oilCompared with the change curve of measurement scale, relative gradient error can make REV steady Fixed platform is more obvious, is conducive to the identification of REV yardsticks.

In whole experiment process, PCE is in long term migration, therefore the REV yardsticks of PCE saturation degrees may not be constant. The change such as Fig. 7 of the REV smallest dimensions of PCE saturation degrees in 1433min experimentations in 30 observation grids, dotted line represents every The change of the smallest dimension of PCE saturation degrees REV in group observation grid, realizes representing the REV of PCE saturation degrees in every group of observation grid The change of the average value of smallest dimension.Observation Fig. 7 (a-f) grids SA01-SA05, SB01-SB05, SC01-SC05 and SF01- The REV smallest dimensions of PCE saturation degrees slowly increase with the time in SF05, and PCE satisfies in observation grid SD01-05 and SE01-05 REV smallest dimensions with degree are held nearly constant.Not only the REV smallest dimensions of observation grid can be presented and differed in identical pollution pond The characteristics of sample, and REV smallest dimensions can also change with the time.

PCE saturation degrees S during PCE long term migrations_oilREV smallest dimensions frequency distribution such as Fig. 8, transverse axis represents REV Smallest dimension, the longitudinal axis represents corresponding frequency.In the first few minutes of PCE long term migrations experiment, PCE saturation degrees S_oilREV The frequency distribution of smallest dimension is in irregular random distribution, and now only a small amount of PCE is entered into sandbox, the Pollution Plume of PCE It is smaller.Over time, increasing PCE is injected into sandbox, and Pollution Plume constantly expands, PCE saturation degrees S_oil's The frequency of REV smallest dimensions becomes closer to Gaussian Profile, PCE saturation degrees S_oilREV smallest dimensions average value be 5.0- 6.0mm, such as Fig. 8 (d).After the injection of PCE terminates, distress resolves, PCE saturation degrees S are injected_oilREV smallest dimensions frequency The shape of distribution becomes closer to Gaussian Profile, such as Fig. 8 (e-f).When experiment is by 1095min, PCE saturation degrees S_oilREV The frequency distribution shape of smallest dimension becomes stabilization, does not have afterwards with time significant change, such as Fig. 8 (g-h), PCE saturations Degree S_oilREV smallest dimensions be distributed between 4.0mm and 14.0mm.Fig. 8 a-h show that PCE is vertical under injection pressure effect PCE saturation degrees S in infiltration process_oilThe frequency of REV smallest dimensions random distribution is presented, have a big fluctuation, stop injection PCE Afterwards, distress resolves are injected, afterwards PCE saturation degrees S_oilREV smallest dimensions frequency shape close to height more regular, evenly This distribution.

The PCE saturation degrees S during PCE long term migrations_oilREV smallest dimensions cumulative frequency distribution such as Fig. 9 (a-h). In experiment initial period, PCE injection sandboxes, PCE saturation degrees S_oilREV smallest dimensions cumulative frequency and REV smallest dimensions Incremental trend is presented, but occurs in that random fluctuation, such as Fig. 9 (a-b).With the carrying out of experiment, PCE is gradually migrated, and is polluted Plumage progressively expands, and PCE is infiltrated from upper strata to lower floor in vertical direction, CE saturation degrees S_oilREV smallest dimensions cumulative frequency Shape gradually become more to smooth, fluctuation is gradually reduced, such as Fig. 9 (c-d).When REV smallest dimensions are more than 11.0mm, for Cumulative frequency then more than 80%, illustrate that the REV smallest dimensions of PCE saturation degrees in sandbox are similar to 11.0mm, such as Fig. 9 (c-d). At the end of PCE injects, distress resolves, linear positive correlation, such as Fig. 9 between cumulative frequency and REV smallest dimensions are injected H (), the REV smallest dimensions of the PCE saturation degrees in the grid more than 80% are about 12.0mm.PCE saturation degrees S_oilREV it is minimum The frequency and cumulative frequency shape of yardstick change with time and show, can be by the property of REV frequencies and cumulative frequency come really Determine stages of the PCE in long term migration.

Interfacial area A between PCE- water_OWFor understanding, PCE is in Migration in Porous Media behavior and obtains PCE long term migrations Characteristic parameter it is most important.For each pixel of two-dimentional translucent quartz sand, along solid phase particles on thickness direction and hole Gap is presented the structure of layered distribution.By the measure of LTM and LTV technologies, interfacial area between 30 PCE- water of observation grid A_OWThe relation such as Figure 10 (a-f) changed with measurement scale, as can be seen from the figure interfacial area A between PCE- water_OWWith measuring scale The change curve of degree and PCE saturation degrees S_oilChange curve with measurement scale is very different.When measurement scale is smaller, PCE- Interfacial area A between water_OWMeasured value occur in that substantial amounts of big ups and downs with the change of measurement scale.When measurement scale exceedes During the smallest dimension of REV, interfacial area A between the PCE- water for measuring_OWFluctuation weaken.With the further increasing of measurement scale Greatly, interfacial area A between the PCE- water of observation grid SA01-05, SB01-05, SC01-05 and SD01-05_OWMeasured value totality On reducing, and interfacial area A between the PCE- water of observation grid SE01-05 and SF01-05_OWThe trend of increase is then presented.Such as Shown in Figure 10 (f), for being chosen in the PCE Pollution Plumes in discrete state in the translucent quartz sand of the background material from sandbox Observation grid SF01-05, interfacial area A between the PCE- water for measuring_OWFirst there is larger fluctuation, then gradually tend towards stability. With PCE saturation degrees S_oilCompared with the change curve of measurement scale, interfacial area A between PCE- water_OWThe small fluctuation of curve more Many, general trend is more flat.

For interfacial area A between more accurately qualitative assessment PCE- water_OWREV, it is same to interface between PCE- water Area A_OWRelative gradient error calculated, come more accurate with the change curve of measurement scale will pass through relative gradient error Really identify REV platforms.Figure 11 (a-f) is the relative gradient error of each observation grid with the change curve of measurement scale, institute REV platforms all clearly, are easily recognized in having curve, and it is more convenient that this causes that REV is assessed.When measurement scale is initially in small yardstick In the range of, there is violent fluctuation in relative gradient error, and then with the gradually increase of measurement range, the fluctuation on curve is gradually Gradually reduce.In all observation grids, interfacial area A between the PCE- water of SA01-05, SB01-05 and SC01-05_OWRelatively ladder Degree error amount is minimum, and interfacial area A between the PCE- water of observation grid SD01-05, SE01-05 and SF01-05_OWRelatively ladder The value for spending error is maximum.With PCE saturation degrees S_oilRelative gradient error compare, interfacial area A between PCE- water_OWRelatively ladder When degree error increases with measurement scale, fluctuation is quick to be reduced.Sum it up, for translucent particle material, between PCE- water Interfacial area A_OWREV than PCE saturation degrees S_oilREV yardsticks it is bigger.

The yardstick for obtaining REV has important meaning for characteristic features in determination PCE transition processes.Moved for a long time in PCE During shifting, PCE Pollution Plumes are continually changing, therefore interfacial area A between corresponding PCE- water_OWREV yardsticks can not yet Disconnected to change, this causes accurately to determine interfacial area A between PCE- water_OWREV yardstick it is more difficult, so research REV Change in long term with the time is most important.Interfacial area A between 30 PCE- water of observation grid_OWREV smallest dimensions at any time Between change such as Figure 12, with PCE saturation degrees S_oilREV yardstick versus time curves compare, as shown in fig. 7, PCE- water it Between interfacial area A_OWREV smallest dimensions more stablize in long process, without the larger change of appearance.

Interfacial area A between PCE- water in the experimentation of PCE long term migrations_OWREV smallest dimensions frequency distribution such as Figure 13 (a-h).When experiment initial stage a small amount of PCE is injected into translucent quartz sand, the frequency distribution of REV smallest dimensions is presented Irregular shape, as shown in fig. 13 a-b.As PCE is constantly injected into sandbox, PCE Pollution Plumes gradually expand, when more next The frequency distribution of REV smallest dimensions begins its approach to be distributed in the Gaussian Profile of 1.0-10.0mm, but in 13.0-14.0mm models Enclose interior frequency and occur in that peak value.After PCE injection stages terminate, injection pressure disappears, interfacial area A between PCE- water_OWREV The frequency distribution shape of smallest dimension is gradually stablized, and becomes closer to Gaussian Profile.Additionally, 13.0-14.0mm scopes are corresponding Frequency also gradually keeps constant, such as Figure 13 e-f.After experimentation is more than 1095min, interfacial area A between PCE- water_OWREV No longer there is obvious change, interfacial area A between PCE- water with the time in the frequency distribution of smallest dimension_OWREV smallest dimensions 2.00mm-7.00mm and 13.00mm-14.00mm is distributed in, as shown in Figure 13 h.During whole long-term PCE migrations experiment Interfacial area A between PCE- water_OWREV smallest dimensions frequency distribution change show, inject pressure in the presence of, start Interfacial area A between stage PCE- water_OWThe frequency distribution of REV smallest dimensions random, irregular shape is presented, with injection Distress resolves, PCE Pollution Plumes tend towards stability, and during the reallocation after PCE injects, frequency distribution gradually becomes stabilization.

The interfacial area A between PCE- water during PCE long term migrations_OWREV smallest dimensions cumulative frequency distribution such as Figure 14 (a-h).Interfacial area A between PCE- water_OWREV smallest dimensions cumulative frequency it is minimum in experiment incipient stage and REV Yardstick is presented positive correlation, such as Figure 14 (a-b).With the carrying out of experiment, PCE is vertically infiltrated to deep layer and is expanded Pollution Plume, Interfacial area A between PCE- water_OWThe shape of cumulative frequency of REV smallest dimensions become increasingly to smooth, such as Figure 14 (c-d), And the significant increase of the corresponding cumulative frequencies of 13.0-14.0mm.When cumulative frequency is more than 80%, interface between corresponding PCE- water Area A_OWREV smallest dimensions reach 11.0mm, such as Figure 14 h.Interfacial area A between PCE- water_OWREV smallest dimensions frequency Rate and cumulative frequency distribution shape can be used for distinguishing the different phase during PCE long term migrations.

Claims (7)

1. the determination method of a kind of DNAPL REV during long term migration in translucent particle material, it is characterised in that：Including Following steps：

(1) by the full water of two-dimentional translucent particle material, visible ray penetrable material, CCD camera is made to receive transmitted light intensity；

(2) porosity of translucent particle material is calculated by the microcosmic imaging technique of visible ray；

(3) long term migration is carried out in DNAPL injections translucent particle material, continues to be used in combination with visible ray penetrable material during being somebody's turn to do CCD camera receives transmitted light intensity, and saturation degree, the interfacial area of DNAPL- water of DNAPL are calculated with light transmission method；

(4) REV of the saturation degree during DNAPL long term migrations, the interfacial area of DNAPL- water is entered with relative gradient error Row quantitative assessment；

(5) REV is counted, the change of the frequency and cumulative frequency of REV size distributions during analysis DNAPL long term migrations Change.

2. the determination method of DNAPL according to claim 1 REV during long term migration in translucent particle material, It is characterized in that：Step (1) loads the translucent quartz sand material of different-grain diameter in two-dimentional sandbox, then with water saturation quartz Sand material material, is irradiated so that visible ray penetrable material with visible ray from the side of sandbox, is connect with CCD camera in the opposite side of sandbox Receive transmitted light intensity.

3. the determination method of DNAPL according to claim 1 REV during long term migration in translucent particle material, It is characterized in that：Step (2) calculates the porosity of translucent particle material according to the relation between porosity and transmitted light intensity：

lnI_s=β+n ξ

Wherein, I_sIt is the transmitted light intensity after visible ray penetrates the translucent particle material of full water, n is porosity；I_oIt is the original light intensity of visible light source, C is the parameter for correcting visible transmission error, α_sIt is the light suction of solid phase Receive coefficient, d_sBe full water translucent quartz sand material in solid phase particles average diameter, L_TIt is the thickness of translucent particle material Degree, e is Euler's constant；τ_s,wIt is the light transmission of solid-liquid water termination, d_oIt is the average straight of hole Footpath；

The porosity of the translucent particle material in each pixel can quantitatively be calculated by above formula.

4. the determination method of DNAPL according to claim 1 REV during long term migration in translucent particle material, It is characterized in that：Step (3) calculates the saturation degree of DNAPL with light transmission method：

$S_{oil}=\frac{\ln I_S-\ln I}{\ln I_S-\ln I_{oil}}$

Wherein, S_oilIt is the saturation degree of DNAPL, I_oilBe two-dimentional translucent quartz sand completely by DNAPL saturations when transmitted light intensity Value, I is current transmitted light intensity；I_oilIt is calculated as：

$I_{oil}=I_S{\mathrm{\&tau;}}_{w,o}^{2k_o}{e}^{-{\mathrm{\&alpha;}}_{oil}{d}_o{k}_o}$

$k_o=\frac{ln(I_s/I_d)}{2ln({\mathrm{\&tau;}}_{s,w}/{\mathrm{\&tau;}}_{s,a})}$

Wherein, I_dIt is the transmitted light intensity values under the conditions of translucent particle material is completely dried, τ_w,oIt is interface between water and DNAPL Transmissivity, τ_s,aIt is the solid phase particles of material and the transmissivity of Air Interface, α_oilIt is the absorptivity of DNAPL, k_oIt is many two dimensions Hole sum on the dielectric thickness of hole, d_oThe average diameter of solid phase particles.

5. the determination method of DNAPL according to claim 4 REV during long term migration in translucent particle material, It is characterized in that：On a microscopic scale, translucent particle material is that hole by solid phase particles and between them is constituted, therefrom The research unit of an optional equilateral triangle, the porosity and pore area of this unit are respectively：

$n=\frac{A-{\mathrm{\&pi;R}}_V^2/2}{A}$

$A_p=A-\frac{{\mathrm{\&pi;R}}_V^2}{2}$

Wherein, R_VIt is the mean radius of solid phase material particle, A is the gross area of triangular element, A_pIt is the hole face in unit Product；

Hole in unit is approximately a circle, this diameter of a circle λ_lFor：

$A_p=\frac{{\mathrm{\&pi;R}}_V^{2}n}{2(1-n)}=\mathrm{\&pi;}{({\mathrm{\&lambda;}}_l/2)}^2$

${\mathrm{\&lambda;}}_l=R_V\sqrt{\frac{2n}{1-n}}$

For the fluid in granular materials, fluid can not only flow through the middle hole of triangular element, and can flow through solid phase Space between particle；Therefore, pore diameter is diameter of a circle λ_lWith solid phase particles clearance distance Δ L_gAverage value：

${\mathrm{\&Delta;L}}_g=L_1-2R_V=R_V(\sqrt{\frac{2\mathrm{\&pi;}}{\sqrt{3}(1-n)}}-2)$

$d_o=\frac{{\mathrm{\&lambda;}}_l+{\mathrm{\&Delta;L}}_g}{2}=\frac{R_V}{2}(\sqrt{\frac{2n}{1-n}}+\sqrt{\frac{2\mathrm{\&pi;}}{\sqrt{3}(1-n)}}-2)$

Wherein, L₁It is the length of side of triangular element, Δ L_gIt is the distance in solid phase particles gap；

In the microcosmic imaging technique of visible ray, the translucent particle material in each pixel is layered distribution, hole and solid phase Particle from two-dimentional translucent particle material apart from one another by taking up an official post and take a cross-sectional area A_oInfinitesimal infinitesimal, hole it is average Diameter d_o, hole number k_o, solid phase particles average diameter d_sWith the number k of solid phase particles_sMeet following relation：

nA_oL_T=A_ok_od_o

Wherein, A_oIt is the cross-sectional area of solid phase particles；

Therefore, the hole sum k on Two-dimensional Porous Medium thickness_oCan be calculated by above formula；

After calculating hole sum and the pore diameter in each pixel, it is assumed that DNAPL is evenly distributed on each pixel In all holes, in cubical shape, cubical cross-sectional area is approximately the cross-sectional area of each pixel, therefore can be with The cubical length of DNAPL in each hole is calculated, institute on the surface area and pixel of DNAPL in each hole is then calculated There is the total surface area of DNAPL in hole；The surface area of DNAPL can be approximately the interfacial area between DNAPL and water, DNAPL Surface area interfacial area between DNAPL- water is standardized divided by the volume of measuring system, unit is cm^-1。

6. the determination method of DNAPL according to claim 1 REV during long term migration in translucent particle material, It is characterized in that：Step (4) determined with relative gradient error in translucent particle material DNAPL saturation degrees and DNAPL- water it Between interfacial area REV yardsticks：

Wherein,It is relative gradient error,It is the parameter for needing assessment, such as saturation degree of DNAPL, i is the rectangular physique of measurement From small yardstick to the increased ordinal number of large scale, Δ L is each increased scale size of cuboid grid yardstick to son.

7. the determination method of DNAPL according to claim 6 REV during long term migration in translucent particle material, It is characterized in that：In order to smooth relative gradient errorThe big ups and downs of curve so as to the yardstick of REV is recognized accurately, with relative 5 points of gradient error averagely recognize REV：

${\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_g^i=\frac{{\mathrm{\&epsiv;}}_g^{i-2}+{\mathrm{\&epsiv;}}_g^{i-1}+{\mathrm{\&epsiv;}}_g^i+{\mathrm{\&epsiv;}}_g^{i+1}+{\mathrm{\&epsiv;}}_g^{i+2}}{5}\&le;0.2$

Wherein,It is 5 average values of relative gradient error, whenThe yardstick of REV has been reached during less than or equal to 0.2.