Microcosm field model and method for studying migration and transformation of chlorobenzenes

Abstract

The present application relates to a microcosm site model and method for studying the migration rule and conversion path of chlorobenzene, wherein the microcosm site model comprises a first microcosm site model for analyzing, studying and verifying the generation and migration path of chlorobenzene in the site, a second microcosm site model for studying and verifying the inaccessibility of chlorination reaction occurring in the soil environment and a third microcosm site model for studying the influence of leaching, percolation and volatilization on the migration path of target pollutants. The present application determines the source and migration path of six CBs in the land of dye chemical enterprises, masters the migration and conversion rule of CBs, and provides a scientific basis for the source control of CBs in the production process, the leakage point investigation and the disposal of production waste of dye chemical enterprises, so as to ensure the safe operation of the production enterprises, and provides strong support for the block management and safe utilization of the dye chemical enterprises, such as the investigation of CBs pollution status, risk assessment and even repair control of the closed block.

Description

Technical Field

[0001] This invention relates to the field of soil pollution prevention and control, specifically to a microcosmic site model and method for studying the migration patterns and transformation pathways of chlorobenzenes. Background Technology

[0002] Chlorobenzenes (CBs) are widely used raw materials and organic solvents in the dye chemical industry. They are a class of monocyclic aromatic compounds formed by replacing hydrogen atoms on a benzene ring with chlorine atoms, including six types (12 homologues): chlorobenzene, dichlorobenzene, trichlorobenzene, tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene. These substances are characterized by high toxicity, persistence, and bioaccumulation, and are also known to cause teratogenicity, carcinogenicity, and mutagenicity. Chlorobenzenes, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, pentachlorobenzene, and hexachlorobenzene have been explicitly included in my country's published blacklist of priority controlled pollutants and list of priority controlled chemicals.

[0003] With the rapid pace of industrialization and urbanization in my country, and the green development of urban redevelopment plans such as "retreating secondary industries and advancing tertiary industries" and "moving urban areas into industrial parks," a large number of dye and chemical pollution sites have emerged in rapidly developing economic zones such as the Beijing-Tianjin-Hebei region. This has, to some extent, hindered the coordinated development of regional socio-economic and ecological environments. Dichlorobenzene and trichlorobenzene are the most commonly used raw materials and organic solvents in dye and chemical enterprises. During the use, production, storage, and transportation of chlorobenzene (CBs), leaks and improper disposal of waste have led to their entry into the soil environment of enterprise sites and surrounding areas, thereby harming the ecological environment and endangering human health. In recent years, my country has successively promulgated laws and regulations on soil pollution prevention and control, gradually standardizing the environmental management process for polluted sites. Soil pollution status investigation is the starting point for initiating site environmental management. Whether the investigation results can accurately depict the spatial distribution characteristics of pollutants on the site will directly affect subsequent risk assessment and remediation, and thus influence the management decisions of government departments. Therefore, clarifying the distribution characteristics and migration and transformation patterns of different chlorobenzene compounds in dye and chemical pollution sites is crucial for subsequent risk assessment, control, and remediation of site safety management.

[0004] Currently, numerous studies on the distribution characteristics of chlorobenzene compounds (CBs) in chemically contaminated sites exist both domestically and internationally. However, the target pollutants generally focus on one or two to three chlorobenzene compounds. Meng Xianrong et al. studied the horizontal and vertical distribution characteristics of chlorobenzene in a chemically contaminated site, indicating that the functional zoning of production areas and the hydrogeological conditions of the site are the main factors influencing chlorobenzene distribution. Yu Mei used chlorobenzene, dichlorobenzene, and trichlorobenzene as examples to study the distribution characteristics and migration patterns of CBs in a chemically contaminated site. SPIGARELLI et al. studied the distribution characteristics of hexachlorobenzene in nine chemically contaminated sites, finding varying degrees of pollution in the air, soil, and groundwater within the site area. Furthermore, numerous domestic investigations of dye chemical sites have revealed that the soil environment of these sites is often contaminated with multiple chlorobenzene compounds. Tian Yajing et al. found that dichlorobenzene and trichlorobenzene products contain small amounts of chlorobenzene and other polychlorinated benzenes; in the production of phthalocyanine dyes, the use of trichlorobenzene typically generates hexachlorobenzene. Yuan Yiqian studied the dyeing and printing wastewater from five dye chemical companies and found that trichlorobenzene, tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene were commonly detected in all of them.

[0005] Based on information such as land use history, stratigraphic structure, spatial distribution characteristics of chlorobenzenes (CBs), and existing domestic and international research findings, the applicant previously derived a conceptual model for the migration and transformation of CBs in the land parcel. Building upon this, this invention provides a microcosmic site model and method for studying the migration patterns and transformation pathways of chlorobenzenes. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a microcosmic site model and method for studying the migration patterns and transformation pathways of chlorobenzenes. The objective is to determine the sources and migration pathways of six chlorobenzene compounds (CBs) in dye chemical plant sites and to understand the migration and transformation patterns of CBs. The technical solution of this invention to solve the above-mentioned technical problem is as follows:

[0007] Firstly, a microcosmic site model for studying the migration patterns and transformation pathways of chlorobenzenes. The microcosmic site model includes a first microcosmic site model for analyzing and verifying the generation and migration pathways of chlorobenzenes in a site, a second microcosmic site model for studying and verifying the inaccessibility of chlorination reactions in the soil environment, and a third microcosmic site model for studying the impact of leaching, percolation, and volatilization on the migration pathways of target pollutants.

[0008] The beneficial effects of this invention are as follows: Through the aforementioned microcosmic site model, this invention identifies the sources and migration paths of six types of CBs in the land used by dye and chemical enterprises, and grasps the migration and transformation laws of CBs. This provides a scientific basis for dye and chemical enterprises in the production process to control CBs at the source, investigate leakage points, and dispose of production waste, thereby ensuring the safe operation of enterprises in production. In addition, it provides strong support for the management and safe utilization of land plots with CBs pollution status investigation, risk assessment, and even remediation control in the closed sites of dye and chemical enterprises.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, the first microcosmic site model is filled from bottom to top with a first gravel layer, a first coarse sand layer, and a first fine sand layer; the first gravel layer is inoculated with aquatic microorganisms, the first gravel layer is filled with water, and a first water outlet is provided at the bottom of the first gravel layer; the first coarse sand layer is inoculated with soil microorganisms.

[0011] The second microcosmic site model is filled from bottom to top with a second gravel layer, a second coarse sand layer, and a second fine sand layer; the second gravel layer is inoculated with the water microorganisms, the second gravel layer is filled with water, and a second water outlet is provided at the bottom of the second gravel layer; the second coarse sand layer is inoculated with the soil microorganisms; a stainless steel pipe with a first opening is provided in the second fine sand layer, and the stainless steel pipe with the opening is connected to the first water tank.

[0012] The third microcosmic site model is filled from bottom to top with a third gravel layer, a third coarse sand layer, and a third fine sand layer; the third gravel layer is inoculated with the aquatic microorganisms, the third gravel layer is filled with water, and a third water outlet is provided at the bottom of the third gravel layer; the third coarse sand layer is inoculated with soil microorganisms; a stainless steel pipe with a second opening is provided in the third fine sand layer, and the stainless steel pipe with the second opening is connected to the second water tank.

[0013] Furthermore, a first soil gas probe is embedded in the first fine sand layer; a second soil gas probe is embedded in the second fine sand layer; and a third soil gas probe is embedded in the third fine sand layer. Changes in soil gas in the first microcosmic site model to the third microcosmic site model are detected using the first soil gas probe to the third soil gas probe.

[0014] Furthermore, the aquatic microbial phylum level includes Proteobacteria, Bacteroidota, Campilobacterota, Actinobacteriota, and Desulfobacterota; the aquatic microbial genus level includes Pseudomonas, Sphingobium, Sulfuricurvum, norank_f__Marinifilaceae, and Sideroxydans;

[0015] The soil microbial phyla include Proteobacteria, Actinobacteriota, Firmicutes, Chloroflexi, and Acidobacteriota, and the soil microbial genera include Pseudomonas, Thiobacillus, Methylomicrobium, Azoarcus, and unclassified_f__Rhodocyclaceae.

[0016] Furthermore, the length of the first gravel layer, the second gravel layer, and the third gravel layer is not less than 2m, the width is not less than 2m, and the height is not less than 30cm.

[0017] The length of the first coarse sand layer, the second coarse sand layer, and the third coarse sand layer is not less than 2m, the width is not less than 2m, and the height is not less than 30cm.

[0018] The first fine sand layer, the second fine sand layer, and the third fine sand layer are all at least 2m in length, at least 2m in width, and at least 140cm in height.

[0019] Furthermore, the first coarse sand layer is a mixture of coarse sand and heavily contaminated soil; the second coarse sand layer is a mixture of coarse sand and heavily contaminated soil; and the third coarse sand layer is a mixture of coarse sand and heavily contaminated soil. The amount of heavily contaminated soil in the first coarse sand layer is 20–80 kg; the amount of heavily contaminated soil in the second coarse sand layer is 20–80 kg; and the amount of heavily contaminated soil in the third coarse sand layer is 20–80 kg.

[0020] Secondly, a method for studying the migration patterns and transformation pathways of chlorobenzenes includes the following steps: using the first microcosm site model to analyze, study, and verify the generation and migration pathways of chlorobenzenes in the site; using the second microcosm site model to study and verify the inaccessibility of chlorination reactions in the soil environment; using the third microcosm site model to study the effects of leaching, infiltration, and volatilization on the migration pathways of target pollutants; and using the detection results of the first, second, and third microcosm site models to determine the migration patterns and transformation pathways of chlorobenzenes.

[0021] Further, the method includes the following steps: Using the first microcosm site model, injecting a mixed simulated wastewater containing chlorobenzene pollutants (excluding chlorobenzene) into the first gravel layer of the first microcosm site model; periodically sampling and testing the microorganisms in the soil, simulated groundwater, soil air, and / or soil-water media of the first microcosm site model to analyze and verify the generation and migration pathways of chlorobenzene in the site; using the second microcosm site model, adding a mixed simulated wastewater containing dichlorobenzene and trichlorobenzene pollutants into the second microcosm site model monthly through a stainless steel pipe with a first opening; periodically sampling and testing the microorganisms in the soil, simulated groundwater, and soil-water media of the second microcosm site model. Microorganisms in soil atmosphere and / or soil water media are sampled and tested to study and verify the inaccessibility of chlorination reactions in the soil environment. Using the aforementioned third microcosm site model, a mixed simulated wastewater containing chlorobenzene pollutants is added to the third microcosm site model monthly through a stainless steel pipe with a second opening. Microorganisms in the soil, simulated groundwater, soil atmosphere and / or soil water media of the third microcosm site model are sampled and tested regularly to study the impact of leaching, infiltration, and volatilization on the migration pathways of target pollutants. The migration patterns and transformation pathways of chlorobenzene are determined based on the test results of the first, second, and third microcosm site models.

[0022] Furthermore, the content of each chlorobenzene pollutant in the mixed simulated wastewater containing chlorobenzene-free chlorobenzene is 0.01–123.0 mg / L; the content of each chlorobenzene pollutant in the mixed simulated wastewater containing dichlorobenzene and trichlorobenzene is 3.99–123.0 mg / L, and the flow rate of the mixed simulated wastewater containing dichlorobenzene and trichlorobenzene is 30–50 L / month; the content of each chlorobenzene pollutant in the mixed simulated wastewater containing chlorobenzene pollutants is 0.01–293.0 mg / L, and the flow rate of the mixed simulated wastewater containing chlorobenzene pollutants is 30–50 L / month.

[0023] Furthermore, it also includes the following steps: collecting simulated groundwater samples through the first outlet of the first microcosmic site model; collecting simulated groundwater samples through the second outlet of the second microcosmic site model; and collecting simulated groundwater samples through the third outlet of the third microcosmic site model. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process of the present invention;

[0025] Figure 2 Bar diagram (phylum level) showing the settlement diversity of soil microorganisms in a previously contaminated site of a dye factory;

[0026] Figure 3 Bar diagram (genus level) showing the settlement diversity of soil microorganisms in a previously contaminated site of a dye factory;

[0027] Figure 4 Bar diagram (phylum level) showing the settlement diversity of groundwater microbial community in a previously contaminated site of a dye factory;

[0028] Figure 5 Bar diagram (genus level) showing the settlement diversity of groundwater microbial community in a previously contaminated site of a dye factory;

[0029] Figure 6 This is a three-dimensional schematic diagram of the first microcosm site model;

[0030] Figure 7 This is a top view of the first microcosmic site model;

[0031] Figure 8 A schematic diagram of the soil gas detector deployment for the first microcosm site model;

[0032] Figure 9 This is a three-dimensional schematic diagram of the second micro-universe site model;

[0033] Figure 10 This is a top view of the second microcosm site model;

[0034] Figure 11 A schematic diagram of the soil gas detector deployment for the second microcosm site model;

[0035] Figure 12 This is a three-dimensional schematic diagram of the third micro-universe site model;

[0036] Figure 13 Top view of the third microcosm site model;

[0037] Figure 14 A schematic diagram of the soil gas detector deployment for the third microcosm site model;

[0038] Figure 15 A summary and comparison chart of soil sample data from the first microcosm site experiment (unit: mg / kg);

[0039] Figure 16 Summary chart of soil sample data from the second microcosm site model experiment (unit: mg / kg);

[0040] Figure 17 Graph showing the analysis results of soil samples from the third microcosm site (unit: mg / kg);

[0041] Figure 18 Analysis of groundwater sample test results from the third micro-universe site simulation (unit: ug / L);

[0042] Figure 19 Analysis of soil gas sample test results at the Third Microcosm site (unit: ug / m³) 3 ). Detailed Implementation

[0043] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0044] Description of the materials used in the following embodiments:

[0045] Gravel, coarse sand, and fine sand were purchased from the building materials market.

[0046] The simulated wastewater was prepared in the laboratory. In the simulated mixed wastewater containing chlorobenzene-containing pollutants, the content of each chlorobenzene pollutant was 0.01–123.0 mg / L; in the simulated mixed wastewater containing dichlorobenzene and trichlorobenzene, the content of each chlorobenzene pollutant was 3.99–123.0 mg / L; and in the simulated mixed wastewater containing chlorobenzene pollutants, the content of each chlorobenzene pollutant was 0.01–293.0 mg / L.

[0047] The heavily polluted soil and groundwater both originated from a polluted site of a dye factory in North China. The soil and groundwater samples were collected in February 2023, and the samples for inoculation of the heavily polluted soil and groundwater were collected in May 2023.

[0048] Example

[0049] This embodiment utilizes a combination of microbial genomics technology and model simulation experiments to conduct in-depth research on the migration and transformation patterns of six chlorobenzene compounds, aiming to provide technical support for the prevention of pollution in operating enterprises and the remediation of polluted sites in the dye chemical industry. The main contents include ( Figure 1 ):

[0050] (1) Use microbial genomics technology to identify and obtain dechlorination-reducing bacteria in deep soil and groundwater in heavily polluted areas of the previous research site;

[0051] Deep soil and groundwater samples were collected from the heavily polluted area of ​​the previous research site. Microbial genomics techniques were used to conduct diversity and quantitative analysis of dechlorination-reducing bacteria in the soil and groundwater, and to identify and obtain relevant information on dechlorination-reducing bacteria.

[0052] (2) By comparing the functional distribution and stratigraphic structure information of the sites studied in previous studies, three microcosm model sites were simulated and established.

[0053] Microcosmic site simulation experiments were conducted to study the changes in chlorobenzene compounds (CBs) in the "water-soil-air" environment of the model site, as well as the changes in dechlorination-reducing bacteria. The resulting conceptual model of CB migration and transformation revealed the migration and transformation patterns of six chlorobenzene compounds in the land used by dye and chemical industry enterprises. The aforementioned microcosmic site models include: a first microcosmic site model for analyzing and verifying the generation and migration pathways of chlorobenzene in the site; a second microcosmic site model for studying and verifying the inaccessibility of chlorination reactions in the soil environment; and a third microcosmic site model for studying the impact of leaching, percolation, and volatilization on the migration pathways of target pollutants.

[0054] The specific process is as follows:

[0055] 1. Identify and obtain dechlorination-reducing functional bacteria from deep soil and groundwater in heavily polluted areas of the previous research site using microbial genomics technology.

[0056] 1.1 Soil microbial community diversity at the previous study site

[0057] Six sets of soil microbial samples were collected from a contaminated site of a dye factory in North China in February 2023. Two sets of control samples were collected from the former office area of ​​the dye factory, and four sets of soil samples were collected from the heavily polluted area. Each set of samples was tested in 2-3 replicates. The samples were collected on-site by professionals from Shanghai Meiji Biomedical Technology Co., Ltd., and transported to the laboratory for microbial community diversity testing. The results are as follows: Figure 2 and Figure 3 As shown.

[0058] Soil microbial community settlement diversity (Bar) at a previously contaminated site of a dye factory Figure 2 and Figure 3As shown, the top five microbial phyla in the soil samples were Proteobacteria, Actinobacteriota, Firmicutes, Chloroflexi, and Acidobacteriota, while the top five genera were Pseudomonas, Thiobacillus, Methylomicrobium, Azoarcus, and unclassified_f__Rhodocyclaceae.

[0059] Among them, Yu Jintao, a master's student from China University of Geosciences, studied the characteristics and degradation potential of microbial functional groups in chlorinated hydrocarbon contaminated sites. His research showed that Proteobacteria, Firmicutes, and Actinobacteria are the dominant bacterial phyla in chlorinated hydrocarbon contaminated sediments. Furthermore, *Pseudomonas* is the most common potential dechlorination genus, and most *Pseudomonas* species have shown tolerance to chlorinated hydrocarbons. Some species in the *Thiobacillus* genus also possess dechlorination capabilities. These conclusions are basically consistent with the results of this invention.

[0060] Pseudomonas exhibits strong biodegradation capabilities for chlorinated aromatic compounds at the oxygen / anoxic interface, primarily occurring at the vadose zone and groundwater interface. Zhang Weixi et al. screened a Pseudomonas sp. HY-100A strain capable of efficiently degrading a mixture of chlorobenzene (CB) and o-dichlorobenzene (o-DCB). Pseudomonas strains, domesticated from chlorinated hydrocarbon-contaminated soil, are capable of degrading chlorobenzene compounds. Zhang Wanying et al. found relatively high abundance of Pseudomonas in chlorobenzene-contaminated groundwater, and Pseudomonas sp. P51 and Pseudomonas putida have been found to degrade low-chlorinated benzenes in nature. Information on dechlorination capabilities for other genera has not yet been found. Furthermore, studies have reported that Pseudomonas and Azoarcus can utilize DCM (dichloromethane) and DCA (dichloroacetic acid) as carbon and energy sources under aerobic conditions.

[0061] 1.2 Groundwater Microbial Community Diversity at the Previous Study Site

[0062] In a previous study, six sets of groundwater microbial samples were collected from a contaminated site of a dye factory in North China (February 2023). One set of control samples was collected from the former office area of ​​the dye factory, and five sets of groundwater samples were collected from the heavily polluted area. Each set of samples was prepared in quadruplicate. The samples were collected on-site by professionals from Shanghai Meiji Biomedical Technology Co., Ltd., and transported to the laboratory for microbial community diversity testing. The results are as follows: Figure 4 and Figure 5As shown.

[0063] Bar Figure 4 and Figure 5 As shown, the top five phyla in the microbial information of groundwater in heavily polluted areas of contaminated sites are Proteobacteria, Bacteroidota, Campilobacterota, Actinobacteriota, and Desulfobacterota; the top five genus are Pseudomonas, Sphingobium, Sulfuricurvum, norank_f__Marinifilaceae, and Sideroxydans, with Pseudomonas having a relative abundance as high as 90%.

[0064] Literature review and analysis revealed that *Pseudomonas* can acclimatize groundwater contaminated with chlorobenzene compounds and undergo dechlorination degradation of chlorobenzene compounds in anoxic environments. Related studies indicate that *Sphingobium* possesses dechlorination and ring-opening functions, thus contributing to the degradation of chloroaromatic hydrocarbons in this experiment. *Sulfuricurvum* plays an important role in the carbon and sulfur cycles.

[0065] 2. Establish three simulated microcosm sites.

[0066] 2.1 First Microcosmic Site Model

[0067] The structure of the first microcosmic site model is as follows: Figure 6-8 As shown:

[0068] (1) Dimensions: The length, width and height are all 2m, and the volume is 8 cubic meters. The pool is surrounded by a 3:7 wall. The interior is divided into four equal parts with a length of 1m, a width of 1m and a height of 2m by a brick. The side walls and bottom of the pool are equipped with a cement anti-seepage layer.

[0069] (2) The four equal portions of the pool space are set up with four different treatments, as follows:

[0070] Treatment 1 (blank control group): 30cm gravel (submerged in distilled water) + 30cm coarse sand + 140cm fine sand;

[0071] Treatment 2 (uninoculated control group): 30cm gravel (followed by 20L CBs simulated wastewater, then submerged in distilled water) + 30cm coarse sand + 140cm fine sand;

[0072] Treatment 3 (control group without added simulated CBs wastewater): 30cm gravel (12.5L of heavily polluted groundwater was added later to inoculate microorganisms, and then distilled water was added to submerge it) + 30cm coarse sand mixture (coarse sand was mixed with 20kg of heavily polluted soil and inoculated with microorganisms) + 140cm fine sand.

[0073] Treatment 4 (Experimental Group): 30cm gravel (followed by adding 12.5L of heavily polluted groundwater for microbial inoculation, then adding 20L of CBs simulated wastewater, and finally submerging with distilled water) + 30cm coarse sand mixture (coarse sand mixed with 20kg of heavily polluted soil, then inoculated with microorganisms) + 140cm fine sand. Note: The CBs simulated wastewater used in the above treatments does not contain monochlorobenzene (the content of each chlorobenzene pollutant in the mixed simulated wastewater without chlorobenzene is 0.01~123.0mg / L).

[0074] (3) Three layers of soil gas probes were buried at the center of the four different treatment pools, 75cm, 105cm and 150cm from the bottom upwards, to collect and detect the changes in gaseous chlorobenzene substances at different depths in different treatments.

[0075] (4) Four water outlets are set 15cm below the ground to facilitate the collection of simulated groundwater samples with four different treatments in the first micro-universe site.

[0076] (5) Regularly sample and observe the soil, simulated groundwater, soil gas and microorganisms in the soil-water medium in the first micro-universe site. The experimental cycle is 6 months and the sampling frequency is 1 time / month.

[0077] 2.2 Second Microcosm Site Model

[0078] The second microcosmic site model is as follows: Figure 9-11 As shown:

[0079] (1) Dimensions: Length, width and height are all 2m, and the volume is 8 cubic meters. The pool is surrounded by a 3:7 wall, and the side walls and bottom of the pool are all equipped with a cement anti-seepage layer.

[0080] (2) The specific steps for filling the second microcosm site model are as follows:

[0081] The tank was filled from bottom to top with the following materials: 30cm gravel (followed by adding 50L of heavily polluted groundwater for microbial inoculation, then submerged with distilled water), 30cm coarse sand mixture (coarse sand thoroughly mixed with 80kg of heavily polluted soil, then inoculated with microorganisms), 90cm fine sand (two perforated stainless steel pipes were installed in parallel to simulate underground sewage pipelines), and 50cm fine sand filling to a height of 200cm. Two 50L stainless steel water tanks were installed on the left side of reaction tank 2 (for later addition of CBs simulated wastewater), completing the construction. Each month, 20L of self-made mixed simulated wastewater containing dichlorobenzene (3 types) and trichlorobenzene (3 types) was added to each water tank in the second micro-universe site model (the content of each chlorobenzene pollutant in the mixed simulated wastewater containing dichlorobenzene and trichlorobenzene was 3.99–123.0 mg / L, and the flow rate of the mixed simulated wastewater containing dichlorobenzene and trichlorobenzene was 30–50L / month).

[0082] (3) Analogous to the first micro-universe site, four sets of soil gas samplers were evenly deployed in the two bodies of the treatment pool. Three layers of soil gas probes were buried at 75cm, 105cm and 150cm from the bottom upwards to collect and detect the changes in gaseous chlorobenzene substances at different depths.

[0083] (4) A water outlet is set 15cm below the ground to facilitate the collection of simulated groundwater samples in the second micro-universe site model.

[0084] (5) Regularly sample and observe the soil, simulated groundwater, soil gas and microorganisms in the soil-water medium in the second micro-universe site model. The experimental cycle is 6 months and the sampling frequency is 1 time / month.

[0085] 2.3 Third Microcosm Site Model

[0086] The third microcosmic site model is as follows: Figure 12-14 As shown:

[0087] (1) Dimensions: Length, width and height are all 2m, and the volume is 8 cubic meters. The pool is surrounded by a 3:7 wall, and the side walls and bottom of the pool are all equipped with a cement anti-seepage layer.

[0088] (2) The specific filling of the third micro-universe site is as follows:

[0089] The tank was filled from bottom to top with the following materials: 30cm gravel (followed by adding 50L of heavily polluted groundwater for microbial inoculation, then submerged with distilled water), 30cm coarse sand mixture (coarse sand thoroughly mixed with 80kg of heavily polluted soil, then inoculated with microorganisms), 90cm fine sand (two perforated stainless steel pipes were installed parallel to simulate underground sewage pipelines), and 50cm fine sand filling to a height of 200cm. Two 50L stainless steel water tanks were installed on the left side of reaction tank 2 (for later addition of CBs simulated wastewater), completing the construction. Each month, 20L of self-made mixed simulated wastewater containing monochlorobenzene to hexachlorobenzene (a total of 12 substances) was added to each tank in the third microcosmic field. (The content of each chlorobenzene pollutant in the mixed simulated wastewater ranged from 0.01 to 293.0 mg / L, and the flow rate of the mixed simulated wastewater containing chlorobenzene pollutants was 30-50L / month.)

[0090] (3) Analogous to the first microcosm site, four sets of soil gas samplers were evenly deployed in the third microcosm site. Three layers of soil gas probes were buried at 75cm, 105cm and 150cm from the bottom upwards to collect and detect changes in the gaseous substances of chlorobenzene at different depths.

[0091] (4) A water outlet is set 15cm below the ground to facilitate the collection of simulated groundwater samples in the third micro-universe site.

[0092] (5) Regularly sample and observe the soil, simulated groundwater, soil gas and microorganisms in the soil-water medium in the third micro-universe site. The experimental cycle is 6 months and the sampling frequency is 1 time / month.

[0093] 3. Experimental Results

[0094] 3.1 Comparison of horizontal distribution maps of chlorobenzene and CBs before and after in the first microcosm site model, analyzing and verifying the generation and migration pathways of chlorobenzene in the site.

[0095] as follows Figure 15As shown, soil samples from the First Microcosm Site underwent CBs analysis over a six-month period. The original experimental soil samples did not contain monochlorobenzene, 1,2,3,5-tetrachlorobenzene, or 1,2,3,4-tetrachlorobenzene. After one month of reaction at the First Microcosm Site, 1,2,3,4-tetrachlorobenzene appeared, and the levels of pentachlorobenzene and hexachlorobenzene in the experimental soil began to decrease after one month. It is inferred that during the one-month reaction period, the dominant microbial species (Pseudomonas, etc.) inoculated at the First Microcosm Site underwent anaerobic dechlorination, degrading pentachlorobenzene and hexachlorobenzene into lower-level tetrachlorobenzene. Furthermore, three dichlorobenzene substances, three trichlorobenzene substances, and two tetrachlorobenzene substances all showed a rebound after three months, with the rebound of dichlorobenzene substances being more pronounced. This is inferred to be due to the anaerobic dechlorination of pentachlorobenzene, hexachlorobenzene, and other high-chlorinated benzene substances into low-chlorinated benzene substances. Liu Zhitong, a master's student at Nanjing University, discovered through bottled experiments that 1,2,4-trichlorobenzene could be completely degraded and removed after 95 days of microbial treatment, while the relative abundance of dechlorinating microorganisms showed a characteristic of first gradually increasing and then decreasing. Therefore, it is inferred that during the period of March to June in this study, high-chlorinated benzene compounds were dechlorinated to form low-chlorinated benzene compounds, leading to a significant rebound in the content of dichlorobenzene compounds, while trichlorobenzene and tetrachlorobenzene compounds showed a slight rebound.

[0096] 3.2 Comparison of horizontal distribution of CBs before and after in the second microcosm site model, to study and verify the inaccessibility of chlorination reactions in the soil environment.

[0097] like Figure 16 As shown, three trichlorobenzene compounds of known concentration were added to the second microcosm site model. After a 6-month experimental reaction, samples were taken and analyzed every month. Data analysis revealed that the soil samples from the second microcosm site model contained 10 chlorobenzene compounds (excluding monochlorobenzene and 1,2,3,5-tetrachlorobenzene), while the original soil contained 9 chlorobenzene compounds (excluding monochlorobenzene, 1,2,3,5-tetrachlorobenzene, and 1,2,3,4-tetrachlorobenzene). 1,2,3,4-tetrachlorobenzene was not present in the original soil, but was detected in the experimental soil in March and May, indicating its formation through the dechlorination reaction of pentachlorobenzene and hexachlorobenzene. After adding the three trichlorobenzene compounds, the concentrations of tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene in the second microcosm site model showed almost no increase (compared to the original soil). Furthermore, the chlorination reaction of chlorocarbons requires the replacement of hydrogen atoms on the benzene ring of chlorobenzene compounds by chlorine atoms, a process that requires extremely high external energy (such as high temperature and pressure). In summary, it can be verified that low-chlorinated benzene compounds cannot undergo chlorination reactions to produce high-chlorinated benzene compounds after entering the soil environment.

[0098] 3.3 Comparative distribution maps of leaching, permeation, and volatilization factors before and after the target pollutant in the third microcosm site model, determining the impact on the migration path of the target pollutant.

[0099] After 2-3 months of experimental observation, multiple chlorobenzene substances were detected in the soil, simulated wastewater and soil gas in the simulated third microcosm site. The migration analysis of chlorobenzene substances in each medium is shown below.

[0100] (1) Soil

[0101] The soil sampling depth at the third micro-universe site was set at six layers: 30cm, 60cm, 90cm, 120cm, 150cm, and 180cm from the top of the reaction tank. Soil samples were collected from the 30cm and 60cm layers in January, and from the 30cm–180cm layers in February. Each soil sample tested for 12 substances, ranging from monochlorobenzene to hexachlorobenzene. The analysis and summary of the test data are as follows. Figure 17 As shown.

[0102] In the third microcosm site, the simulated underground pipeline leak point was located 50cm deep from the top of the reaction tank. After two months of vertical penetration testing, monochlorobenzene, pentachlorobenzene, and hexachlorobenzene were not found in the soil samples from the reaction tank. The three dichlorobenzene compounds were detected at a maximum depth of 90cm, and the three trichlorobenzene compounds were detected at a maximum depth of 180cm (having entered the simulated groundwater layer). Tetrachlorobenzene was only found at a depth of 60cm after one month of vertical migration.

[0103] (2) Simulated groundwater

[0104] Two months of simulated groundwater samples were collected from the third micro-universe site for analysis. The results are as follows: Figure 18 As shown, only three dichlorobenzene compounds and three trichlorobenzene compounds were detected in the simulated groundwater in the reaction tank. Data from January and February showed almost identical results for each indicator. It is inferred that after one month of penetration, dichlorobenzene and trichlorobenzene compounds had entered the simulated groundwater, and due to the extremely low solubility of chlorobenzene compounds, the simulated groundwater was already saturated.

[0105] (3) Soil gas

[0106] Three batches of chlorobenzene-containing soil gas samples were collected from the third microcosm site, with each batch collected one month apart. Each batch was collected at three depths: 75cm, 105cm, and 150cm above the bottom of the reaction tank. The results of the chlorobenzene-containing soil gas samples from the third microcosm site are as follows. Figure 19 As shown. During a three-month soil gas monitoring period, the gaseous chlorobenzenes detected at the Third Microcosm site were mainly monochlorobenzene, three types of dichlorobenzene, and three types of trichlorobenzene. Monochlorobenzene was only detected in the January data, with concentrations ranging from 8000 to 24000 ug / m³. 3The highest concentration was found at 105 cm depth; however, no monochlorobenzene was detected in February and March, presumably due to volatilization loss in the surface water tank. Due to the influence of simulated wastewater infiltration, no soil gas samples were collected at a depth of 75 cm in February and March. Tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene compounds were not detected in the Third Microcosm site, mainly due to their high boiling points and high vapor pressures (see Table 1 below).

[0107] Table 1 Physicochemical properties of chlorobenzene compounds

[0108]

[0109] (4) Summary

[0110] Analysis of chlorobenzene detection data in soil, simulated groundwater, and soil gas at the third micro-universe site revealed that after one month of vertical infiltration, dichlorobenzene and trichlorobenzene could penetrate a 170cm thick sand layer and enter the simulated groundwater. Monochlorobenzene, after entering the reaction tank, primarily volatilized upwards in gaseous form and entered the atmosphere within two months. All three types of dichlorobenzene and trichlorobenzene exhibited both downward migration and upward volatilization pathways; the downward portion entered the aquifer, while the upward portion entered the atmosphere. Due to their high boiling point, high vapor pressure, high soil adsorption coefficient, low solubility, and low solution concentration (Table 1), tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene were mainly retained in the soil of the reaction tank.

[0111] In summary, the above research has identified the sources and migration pathways of six types of carbon dioxide (CBs) in dye and chemical enterprise land, and grasped the migration and transformation patterns of CBs. This provides a scientific basis for dye and chemical enterprises in the production process to control CBs at the source, investigate leakage points, and dispose of production waste, thereby ensuring the safe operation of enterprises in production. Furthermore, it provides strong support for the management and safe utilization of land in dye and chemical enterprise shutdown sites, including CBs pollution investigation, risk assessment, and even remediation control.

[0112] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0113] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0114] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0115] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0116] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A microcosmic site device for studying the migration patterns and transformation pathways of chlorobenzenes, characterized in that, The microcosm site apparatus includes a first microcosm site apparatus for analyzing, studying and verifying the generation and migration pathways of chlorobenzene in the site, a second microcosm site apparatus for studying and verifying the inaccessibility of chlorination reactions in the soil environment, and a third microcosm site apparatus for studying the impact of leaching, percolation and volatilization on the migration pathways of target pollutants. The first microcosmic site device is filled from bottom to top with a first gravel layer, a first coarse sand layer and a first fine sand layer; the first gravel layer is inoculated with aquatic microorganisms, the first gravel layer is filled with water, and a first water outlet is provided at the bottom of the first gravel layer; the first coarse sand layer is inoculated with soil microorganisms. The second microcosmic site device is filled from bottom to top with a second gravel layer, a second coarse sand layer and a second fine sand layer; the second gravel layer is inoculated with the water microorganisms and filled with water, and a second water outlet is provided at the bottom of the second gravel layer; the second coarse sand layer is inoculated with the soil microorganisms; a stainless steel pipe with a first opening is provided in the second fine sand layer, and the stainless steel pipe with the opening is connected to the first water tank. The third microcosmic site device is filled from bottom to top with a third gravel layer, a third coarse sand layer, and a third fine sand layer; the third gravel layer is inoculated with the aquatic microorganisms, the third gravel layer is filled with water, and a third water outlet is provided at the bottom of the third gravel layer; the third coarse sand layer is inoculated with soil microorganisms; a stainless steel pipe with a second opening is provided in the third fine sand layer, and the stainless steel pipe with the second opening is connected to the second water tank. The length of the first gravel layer, the second gravel layer, and the third gravel layer is not less than 2m, the width is not less than 2m, and the height is not less than 30cm. The length of the first coarse sand layer, the second coarse sand layer, and the third coarse sand layer is not less than 2m, the width is not less than 2m, and the height is not less than 30cm. The first fine sand layer, the second fine sand layer, and the third fine sand layer are all at least 2m in length, at least 2m in width, and at least 140cm in height.

2. The microcosmic site device for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 1, characterized in that, A first soil gas probe is buried in the first fine sand layer; a second soil gas probe is buried in the second fine sand layer; and a third soil gas probe is buried in the third fine sand layer.

3. The microcosmic site device for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 1, characterized in that, The level of aquatic microorganisms includes Proteobacteria , Bacteroidota , Campilobacterota , Actinobacteriota and Desulfobacterota ; The level of aquatic microorganisms includes: Pseudomonas , Sphingobium , Sulfuricurvum , norank_f__Marinifilaceae and Sideroxydans ; The soil microbial phylum level includes Proteobacteria , Actinobacteriota , Firmicutes , Chloroflexi and Acidobacteriota The soil microbial genus level includes Pseudomonas , Thiobacillus , Methylomicrobium , Azoarcus and unclassified_f__Rhodocyclaceae .

4. The microcosmic site device for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 1, characterized in that, The first coarse sand layer is a mixture of coarse sand and heavily polluted soil; the second coarse sand layer is a mixture of coarse sand and heavily polluted soil; and the third coarse sand layer is a mixture of coarse sand and heavily polluted soil.

5. A method for studying the migration patterns and transformation pathways of chlorobenzenes, characterized in that, The method includes the following steps: using the first microcosmic site device according to any one of claims 1 to 4, analyzing and verifying the generation and migration pathways of chlorobenzene in the site; using the second microcosmic site device according to any one of claims 1 to 4, studying and verifying the inaccessibility of chlorination reactions occurring in the soil environment; using the third microcosmic site device according to any one of claims 1 to 4, studying the effects of leaching, percolation, and volatilization on the migration pathways of target pollutants; and using the detection results of the first, second, and third microcosmic site devices to determine the migration patterns and transformation pathways of chlorobenzene.

6. The method for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 5, characterized in that, The process includes the following steps: Using the first microcosm site device, a mixed simulated wastewater containing chlorobenzene-based pollutants (excluding chlorobenzene) is injected into the first gravel layer of the first microcosm site device. Microorganisms in the soil, simulated groundwater, soil gas, and / or soil-water media of the first microcosm site device are sampled and tested periodically to analyze and verify the generation and migration pathways of chlorobenzene in the site. Using the second microcosm site device, a mixed simulated wastewater containing dichlorobenzene and trichlorobenzene-based pollutants is added monthly through a stainless steel pipe with a first opening. Microorganisms in the soil, simulated groundwater, and soil gas of the second microcosm site device are sampled and tested periodically. Sampling and testing of microorganisms in soil and / or soil-water media will be conducted to study and verify the inaccessibility of chlorination reactions in the soil environment. Using the aforementioned third microcosm site device, a mixed simulated wastewater containing chlorobenzene pollutants will be added to the third microcosm site device monthly through a stainless steel pipe with a second opening. Sampling and testing of microorganisms in the soil, simulated groundwater, soil gas, and / or soil-water media of the third microcosm site device will be conducted periodically to study the impact of leaching, infiltration, and volatilization on the migration pathways of target pollutants. The migration patterns and transformation pathways of chlorobenzene will be determined based on the test results of the first, second, and third microcosm site devices.

7. The method for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 6, characterized in that, The concentration of each chlorobenzene pollutant in the simulated mixed wastewater containing chlorobenzene (excluding chlorobenzene) is 0.01 ~ 123.0 mg / L; the concentration of each chlorobenzene pollutant in the simulated mixed wastewater containing dichlorobenzene and trichlorobenzene is 3.99 ~ 123.0 mg / L, and the flow rate of the simulated mixed wastewater containing dichlorobenzene and trichlorobenzene is 30 ~ 50 L / month; the concentration of each chlorobenzene pollutant in the simulated mixed wastewater containing chlorobenzene is 0.01 ~ 293.0 mg / L, and the flow rate of the simulated mixed wastewater containing chlorobenzene is 30 ~ 50 L / month.

8. The method for studying the migration patterns and transformation pathways of chlorobenzenes according to claim 6, characterized in that, It also includes the following steps: collecting simulated groundwater samples through the first outlet of the first microcosmic site device; collecting simulated groundwater samples through the second outlet of the second microcosmic site device; and collecting simulated groundwater samples through the third outlet of the third microcosmic site device.

Images