In-situ non-destructive detection device and method for chlorinated hydrocarbon DNAPL phase in site and water environment

Abstract

The application discloses a device and method for in-situ nondestructive detection of chlorinated hydrocarbon DNAPL phases in a site and water environment, which utilizes a fluorescence excitation and spectrum collection scheme, and the hydrophobicity and liposolubility of a Nile red fluorescent dye, detects the characteristic fluorescence change of the Nile red fluorescent dye when the Nile red fluorescent dye contacts DNAPL phases such as TCE and PCE, dissolves into an organic phase, and generates a significantly enhanced fluorescence signal, thereby rapidly judging the existence of DNAPL, identifying the to-be-detected pollutants, and being suitable for rapid, in-situ and nondestructive detection of chlorinated hydrocarbon pollutants in heavy non-aqueous phase liquid DNAPL in a soil and groundwater environment, and has the advantages of simple operation, rapid response, high sensitivity, environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of environmental testing, specifically to an in-situ non-destructive testing device and method for the DNAPL phase of chlorinated hydrocarbons in sites and aquatic environments. Background Technology

[0002] Non-aqueous phase liquid (NAPL) contaminated sites are a significant type of contaminated site in my country, and also the most challenging to investigate and remediate. Heavy non-aqueous phase liquids (DNAPLs), such as chlorinated hydrocarbon solvents and coal tar, exhibit strong environmental persistence due to their poor water solubility, high volatility, and difficulty in natural degradation. These pollutants can persist and slowly release into the underground environment for extended periods, forming stable pollution sources and posing a serious threat to groundwater ecological security. Therefore, accurate location of contaminated areas and accurate assessment of contamination levels are core prerequisites for the remediation of DNAPL contaminated sites.

[0003] In existing technologies, the detection of DNAPL in soil and groundwater mainly relies on borehole sampling and laboratory analysis. Commonly used techniques include gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). These methods are highly sensitive and accurate, enabling precise chemical qualitative and quantitative analysis of pollutants, and the results are highly reliable. However, they require complex sample pretreatment processes (such as extraction, concentration, and purification), resulting in long analysis cycles. At the same time, pollutant loss or concentration changes can easily occur during sample collection, preservation, and transportation due to factors such as volatilization, which may weaken the authenticity and representativeness of the detection results. The biggest drawback of borehole and well sampling methods is that they cannot accurately determine the precise thickness and distribution of DNAPL in the strata, which seriously restricts the precise investigation and remediation of DNAPL-contaminated sites.

[0004] In addition, to adapt to efficient on-site rapid screening and detection, commonly used technologies also include photoionization detectors (PID) and flame ionization detectors (FID). PID and FID are easy to operate and have a fast response, but they can only provide the relative concentration of total volatile organic compounds and cannot identify components. Portable gas chromatography-mass spectrometry (GC-MS) has certain qualitative capabilities, but it generally suffers from problems such as bulky equipment, high professional operation requirements, expensive maintenance costs, and limited environmental adaptability, making it difficult to fully meet the needs of rapid, continuous, and economical on-site screening. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ non-destructive testing device and method for chlorinated hydrocarbon DNAPL phases in site and aquatic environments, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in site and aquatic environments, including a light source system, filter components, a miniature fiber optic spectrometer, and a computer;

[0008] The light source system includes an LED light source and a light source controller. The light source controller is electrically connected to the LED light source and is used to control the LED light source to excite the light source.

[0009] The light source system is connected to one end of the filter component via a Y-shaped reflective optical fiber. The Y-shaped reflective optical fiber is used to transmit the excitation light source and acquire and transmit the emitted fluorescence.

[0010] The other end of the filter component is connected to a miniature fiber optic spectrometer, which is connected to the computer via USB. The miniature fiber optic spectrometer is used to collect fluorescence signals, and the computer is used for fluorescence signal analysis.

[0011] As a further aspect of the present invention: the Y-type reflective fiber is a one-to-two type fiber, the two ends of the Y-type reflective fiber are respectively connected to an LED light source and a miniature fiber optic spectrometer, and the other end of the Y-type reflective fiber is a reflective fiber optic probe.

[0012] As a further embodiment of the present invention: the excitation wavelength of the LED light source is 490nm, the light source controller is used to control the output power of the LED light source within a limited current range; the effective fluorescence acquisition band of the miniature fiber optic spectrometer is 350-1100nm.

[0013] As a further embodiment of the present invention, it also includes a sample stage disposed on one side of the test bracket, the sample stage comprising a quartz cuvette and a quartz glass plate.

[0014] This invention aims to provide an in-situ non-destructive detection method for chlorinated hydrocarbon DNAPL phases in site and aquatic environments, comprising the following steps:

[0015] Fill the soil sample into a quartz cuvette and smooth the surface;

[0016] Add fluorescent staining solution to the soil sample;

[0017] Cover the soil sample with a quartz glass slide and turn on the excitation light source;

[0018] Fluorescence is collected using a miniature fiber optic spectrometer to obtain the emission spectrum;

[0019] The emission spectrum is analyzed by computer to determine whether DNAPL phase contaminants are present and to identify the types of contaminants.

[0020] As a further aspect of the present invention: the fluorescent staining solution is obtained by diluting a fluorescent dye stock solution in which the fluorescent dye is dissolved in an organic solvent;

[0021] The fluorescent dye is Nile Red, and the organic solvent is anhydrous ethanol.

[0022] The dilution solvent is pure water;

[0023] The excitation wavelength of the excitation light source is 490 nm, and the wavelength range of the collected fluorescence is 520-850 nm.

[0024] As a further aspect of the present invention: the computer is equipped with a storage repository containing information on known pollutant types, and a classification and recognition model is established and trained based on the emission fluorescence spectra of the known pollutant types. The classification and recognition model is used to match and identify the emission spectra collected by the miniature fiber optic spectrometer.

[0025] As a further aspect of the present invention: the known pollutants specifically include carbon tetrachloride, tetrachloroethylene, trichloroethylene, and chloroform, and the step of establishing and training a classification and recognition model based on the emission fluorescence spectra of known pollutant types specifically includes:

[0026] Emission fluorescence spectra of several DNAPL-contaminated soil samples containing known contaminants and chlorinated hydrocarbons were collected.

[0027] The acquired fluorescence spectral data were preprocessed using SG smoothing and SNV standard normalization transformation methods.

[0028] PLS regression analysis was performed on fluorescence spectra and known pollutant species in samples to determine the number of principal factors and establish a PLS-DA classification and identification model.

[0029] Compared with the prior art, the beneficial effects of the present invention are: it provides a small-scale, quick-assembly screening device and method that can be used on-site, enabling rapid in-situ detection of DNAPL phase chlorinated hydrocarbon pollutants in soil, and significantly improving the detection efficiency of DNAPL phase pollutants compared with traditional laboratory testing methods.

[0030] It can perform simple qualitative analysis of DNAPL phase contaminants, while currently commonly used on-site rapid screening tools can only detect volatile organic compounds and do not have separation capabilities, only obtaining total relative concentration values, which does not fully meet the needs of in-situ rapid detection. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in a site and aquatic environment.

[0032] Figure 2 This is a schematic diagram of the cross-section of a reflective fiber optic probe in an in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in a site and aquatic environment.

[0033] Figure 3 Fluorescence spectra of carbon tetrachloride soil samples for in-situ non-destructive testing of chlorinated hydrocarbon DNAPL phases in site and aquatic environments.

[0034] Figure 4 Fluorescence spectra of tetrachloroethylene soil samples used in in-situ non-destructive testing methods for the DNAPL phase of chlorinated hydrocarbons in site and aquatic environments.

[0035] Figure 5 Fluorescence spectra of trichloroethylene soil samples used in in-situ non-destructive testing methods for the DNAPL phase of chlorinated hydrocarbons in site and aquatic environments.

[0036] Figure 6 Fluorescence spectra of chloroform in soil samples for in-situ non-destructive testing of chloroform DNAPL phases in site and aquatic environments.

[0037] Figure 7 This is a confusion matrix diagram of the PLS-DA classification and identification model for predicting test set samples in the in-situ non-destructive testing method for chlorinated hydrocarbon DNAPL phases in site and aquatic environments.

[0038] In the figure, 1-light source controller, 2-LED light source, 3-Y-type reflective optical fiber, 4-test bracket, 5-sample stage, 6-filter component, 7-optical fiber, 8-miniature optical fiber spectrometer, 9-computer. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0041] In one embodiment of the present invention, such as Figure 1 , Figure 2As shown in the figure, an in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phase in a site and aquatic environment provided by an embodiment of the present invention includes a light source system, a filter component 6, a miniature fiber optic spectrometer 8, and a computer 9. The light source system includes an LED light source 2 and a light source controller 1. The light source controller 1 is electrically connected to the LED light source 2 and is used to control the excitation light source of the LED light source 2. The light source system is connected to one end of the filter component 6 through a Y-type reflective fiber 3. The Y-type reflective fiber 3 is used to transmit the excitation light source and acquire and transmit emitted fluorescence. The other end of the filter component 6 is connected to the miniature fiber optic spectrometer 8. The miniature fiber optic spectrometer 8 is connected to the computer 9 through USB. The miniature fiber optic spectrometer 8 is used to acquire fluorescence signals, and the computer 9 is used for fluorescence signal analysis.

[0042] The Y-type reflective fiber 3 is a one-to-two fiber optic cable. The two ends of the Y-type reflective fiber 3 are connected to the LED light source 2 and the miniature fiber optic spectrometer 8, respectively. The other end of the Y-type reflective fiber 3 is a reflective fiber optic probe.

[0043] The filter component 6 is connected to the miniature fiber optic spectrometer 8 via an optical fiber 7.

[0044] The excitation wavelength of the LED light source 2 is 490nm, and the light source controller 1 is used to control the output power of the LED light source 2 within a limited current range; the effective fluorescence acquisition band of the miniature fiber optic spectrometer is 350-1100nm.

[0045] It also includes a sample stage 5 set on one side of the test bracket 4, the sample stage 5 including a quartz cuvette and a quartz glass plate.

[0046] In this embodiment, typical DNAPL phase chlorinated hydrocarbon pollutants (such as trichloroethylene TCE, tetrachloroethylene PCE, etc.) in soil are used as the research object. The hydrophobicity and lipophilicity of Nile Red fluorescent dye are utilized. When it comes into contact with DNAPL phases such as TCE and PCE, it dissolves into the organic phase and generates a significantly enhanced fluorescence signal. By detecting this characteristic fluorescence change, the presence of DNAPL can be quickly determined, and the pollutant to be tested can be identified at the same time. Furthermore, in specific equipment and usage scenarios, the light source controller is limited to adjusting the light source intensity within the current range of 1-99mA. The reflective optical fiber and the interface between the optical fiber and other components are all SMA interfaces. The fluorescence acquisition and analysis software in computer 9 can modify the integration time, acquisition mode, and perform wavelength correction according to the detection requirements.

[0047] In one embodiment of the present invention, the present invention also provides an in-situ non-destructive detection method for chlorinated hydrocarbon DNAPL phases in a site and aquatic environment, comprising the steps of:

[0048] Soil samples are filled into quartz cuvettes and the surface is leveled; fluorescent staining solution is added to the soil samples; a quartz glass slide is placed on the soil samples and the excitation light source is turned on; fluorescence is collected by a miniature fiber optic spectrometer 8 to obtain the emission spectrum; the emission spectrum is analyzed by a computer 9 to determine whether DNAPL phase contaminants are present and to identify the types of contaminants.

[0049] The fluorescent staining solution is obtained by diluting a fluorescent dye stock solution dissolved in an organic solvent; the fluorescent dye is Nile Red, the organic solvent is anhydrous ethanol, the dilution solvent is pure water, the excitation wavelength of the excitation light source is 490 nm, and the wavelength range of the collected fluorescence is 520-850 nm.

[0050] The computer 9 is equipped with a storage repository containing information on known pollutant types. A classification and recognition model is established and trained based on the emission fluorescence spectra of the known pollutant types. The classification and recognition model is used to match and identify the emission spectra collected by the miniature fiber optic spectrometer 8.

[0051] The known pollutants specifically include carbon tetrachloride, tetrachloroethylene, trichloroethylene, and chloroform. The step of establishing and training a classification and recognition model based on the emission fluorescence spectra of known pollutant types specifically includes:

[0052] Emission fluorescence spectra were collected from several DNAPL-contaminated soil samples containing known contaminants and chlorinated hydrocarbons.

[0053] The acquired fluorescence spectral data were preprocessed using SG smoothing and SNV standard normalization transformation methods.

[0054] PLS regression analysis was performed on fluorescence spectra and known pollutant species in samples to determine the number of principal factors and establish a PLS-DA classification and identification model.

[0055] In this embodiment, as Figures 3 to 7 The detection method is implemented based on the device in the previous embodiment. To eliminate interference from external light, a black box is used to isolate the system from the outside world during the experiment. The specific steps are as follows:

[0056] Preparation of fluorescent dye solution: Nile red solid powder was dissolved in anhydrous ethanol to prepare a stock solution; before detection, it was diluted with pure water to the required concentration to obtain the working solution of fluorescent dye for detection; Preparation of contaminated soil sample: The sample to be tested was filled into a quartz cuvette with a smooth surface, the fluorescent dye solution was dropped onto the sample, and the quartz glass slide was quickly covered and placed on the sample stage; Fluorescence detection: The excitation light source was turned on, and fluorescence detection was performed using a spectrometer; Classification and recognition model establishment: A classification and recognition model was established using the emission fluorescence spectra of samples with known pollutant types in the training set; Result analysis: Qualitative analysis was performed using the emission fluorescence spectra of samples with unknown pollutant types in the test set.

[0057] Under LED light source illumination, if DNAPL phase chlorinated hydrocarbons are present in the sample, the dye will dissolve into the organic phase and produce a significantly enhanced fluorescence signal. By collecting the fluorescence spectrum with a miniature fiber optic spectrometer, and based on whether the fluorescence intensity is significantly enhanced and the spectral characteristics, it is possible to quickly and in situ determine whether the soil contains the target pollutant, thus achieving qualitative identification.

[0058] In the specific implementation: four target substances were identified based on the type of pollutant: carbon tetrachloride, tetrachloroethylene, trichloroethylene, and chloroform; 200 fluorescence spectral samples were collected for each category, totaling 800 samples; spectral data in the 520nm to 850nm band were obtained using a fluorescence spectral acquisition system, resulting in fluorescence intensity at 816 wavelength points, with the original data dimension being 800 rows × 816 columns; a stratified random partitioning method was adopted, with 160 samples randomly selected from each category as the training set and the remaining 40 as the test set, with a random seed of 42 set to ensure repeatability of results. The final training set contained 640 samples (4 × 160), and the test set contained 160 samples (4 × 40). The training set was used for model building and parameter selection, while the test set was used for final performance verification.

[0059] A Savitzky-Golay smoothing filter with a window width of 11 and a polynomial order of 3 is used to perform convolution smoothing on the spectral curve of each sample. A standard normal variable transformation is performed on each sample by first subtracting the mean of all wavelength points of the sample and then dividing by the standard deviation, so that the mean of each sample is 0 and the standard deviation is 1. This step is also performed independently for each sample.

[0060] The mean and standard deviation of each wavelength point are calculated based on the training set. Then, the training set and the test set are standardized respectively. This step eliminates the scale difference between different wavelength variables, so that the mean of each feature on the training set is 0 and the standard deviation is 1, which is conducive to the stable solution of PLS ​​regression. The four pollutant labels in the training set are converted into a dummy variable matrix, and each dummy variable is centered to obtain a centered response matrix. The centering operation eliminates the intercept term, allowing PLS to focus on modeling inter-class differences.

[0061] Five-fold stratified cross-validation was employed to calculate the root mean square error (RMSECV) of cross-validation for latent variables ranging from 1 to 30. The number of latent variables with the smallest RMSECV was selected as the optimal model complexity. The calculation results showed that the RMSECV was minimized when the number of latent variables was 10; therefore, the optimal number of latent variables was determined to be 10. A PLS-DA regression model was established using all 640 training samples and the selected 10 latent variables, yielding the regression coefficient matrix and the cross-validation determination coefficient Q. 2 The value of 0.8 indicates that the model has good predictive ability.

[0062] Spectral data of 160 samples from the test set (already subjected to the same SG smoothing and SNV normalization) were input into the trained PLS-DA model to obtain continuous predicted values ​​for each sample's category. The category corresponding to the largest predicted value was taken as the final predicted label. The predicted label was compared with the true label to calculate the overall classification accuracy. The results showed that the classification accuracy of the test set reached 96.25%, and the confusion matrix ( Figure 7 The results show that most samples were correctly classified, with only a few samples being misclassified, indicating that the established PLS-DA model has a high ability to identify DNAPL phase chlorinated hydrocarbon pollutants and can be effectively used for qualitative analysis of unknown samples.

[0063] The detection system involved in this application is not limited to Figure 1 The illustrated method of use also allows the fiber optic probe and fiber optic components to be integrated and mounted on in-situ drilling equipment. During drilling, the equipment can acquire real-time fluorescence spectral information of soil at different depths, enabling in-situ detection of DNAPL phase chlorinated hydrocarbon pollutants on the vertical depth profile. Simultaneously, rapid on-site qualitative analysis can be performed. This method effectively improves detection efficiency and spatial resolution, and is suitable for rapid on-site screening and depth distribution identification of contaminated sites, providing in-situ, real-time, and non-destructive technical means for soil environmental assessment and remediation.

[0064] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0065] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the disclosure in the specification and embodiments. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0066] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. An in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in a site and aquatic environment, characterized in that, It includes a light source system, a filter component (6), a miniature fiber optic spectrometer (8), and a computer (9); The light source system includes an LED light source (2) and a light source controller (1). The light source controller (1) is electrically connected to the LED light source (2) and is used to control the LED light source (2) to excite the light source. The light source system is connected to one end of the filter component (6) via a Y-type reflective optical fiber (3). The Y-type reflective optical fiber (3) is used to transmit the excitation light source and acquire and transmit the emitted fluorescence. The other end of the filter component (6) is connected to the miniature fiber optic spectrometer (8), which is connected to the computer (9) via USB. The miniature fiber optic spectrometer (8) is used to collect fluorescence signals, and the computer (9) is used for fluorescence signal analysis.

2. The in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments according to claim 1, characterized in that, The Y-type reflective fiber (3) is a one-to-two fiber. The two ends of the Y-type reflective fiber (3) are connected to the LED light source (2) and the miniature fiber optic spectrometer (8), respectively. The other end of the Y-type reflective fiber (3) is a reflective fiber optic probe.

3. The in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments according to claim 2, characterized in that, The excitation wavelength of the LED light source (2) is 490nm, and the light source controller (1) is used to control the output power of the LED light source (2) within a limited current range; the effective fluorescence acquisition band of the micro fiber optic spectrometer (8) is 350-1100nm.

4. The in-situ non-destructive testing device for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments according to claim 3, characterized in that, It also includes a test stand (4) and a sample stage (5) disposed on one side of the test stand (4), the sample stage (5) including a quartz cuvette and a quartz glass plate.

5. An in-situ non-destructive testing method for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments, characterized in that, Includes the following steps: Fill the soil sample into a quartz cuvette and smooth the surface; Add fluorescent staining solution to the soil sample; Cover the soil sample with a quartz glass slide and turn on the excitation light source; Fluorescence is collected using a miniature fiber optic spectrometer (8) to obtain the emission spectrum; The emission spectrum is analyzed by computer (9) to determine whether DNAPL phase contaminants are present and to identify the types of contaminants.

6. The in-situ non-destructive testing method for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments according to claim 5, characterized in that, The fluorescent staining solution is obtained by diluting a fluorescent dye stock solution in which the fluorescent dye is dissolved in an organic solvent; The fluorescent dye is Nile Red, and the organic solvent is anhydrous ethanol. The dilution solvent is pure water; The excitation wavelength of the excitation light source is 490 nm, and the wavelength range of the collected fluorescence is 520-850 nm.

7. The in-situ non-destructive testing method for chlorinated hydrocarbon DNAPL phases in sites and aquatic environments according to claim 6, characterized in that, The computer (9) is equipped with a storage library containing information on known pollutant types. A classification and identification model is established and trained based on the emission fluorescence spectra of the known pollutant types. The classification and identification model is used to match and identify the emission spectra collected by the micro fiber optic spectrometer (8).

8. The in-situ non-destructive testing method for chlorinated hydrocarbon DNAPL phases in a site and aquatic environment according to claim 7, characterized in that, The known pollutants specifically include carbon tetrachloride, tetrachloroethylene, trichloroethylene, and chloroform. The step of establishing and training a classification and recognition model based on the emission fluorescence spectra of known pollutant types specifically includes: Emission fluorescence spectra of several DNAPL-contaminated soil samples containing known contaminants and chlorinated hydrocarbons were collected. The acquired fluorescence spectral data were preprocessed using SG smoothing and SNV standard normalization transformation methods. PLS regression analysis was performed on fluorescence spectra and known pollutant species in samples to determine the number of principal factors and establish a PLS-DA classification and identification model.

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