Soil column leaching device for simulating nitrosamine infiltration migration and test method thereof

Abstract

The invention relates to a soil column leaching device for simulating nitrosamine infiltration migration and a test method thereof, and belongs to the field of underground water pollution prevention, the soil column leaching device comprises a leaching soil column pipe, soil to be tested and a soil column supporting table, and is characterized in that a spray header for simulating surface runoff scouring is arranged at the top of the leaching soil column pipe; a soil leachate collecting bottle is arranged at the lower part of the soil column supporting table and is communicated with the bottom of the leaching soil column pipe through a funnel arranged above the soil leachate collecting bottle. According to the device, by simulating the pollutant migration process under the leaching condition, soil interstitial liquids and soil lixivium at different time and different soil layers and soil lixivium at the same period can be independently collected and analyzed for multiple times, mutual interference is avoided while simultaneous linkage analysis of the soil interstitial liquids and the soil lixivium is achieved, sampling data are rich, and the sampling accuracy is high. And the experiment result is more real and effective. The device is simple in design structure, low in manufacturing cost and easy to assemble, disassemble and maintain, and has good practicability and popularization and application value.

Description

Technical Field

[0001] The invention patent relates to the field of groundwater pollution prevention and control, and specifically to a soil column leaching device for simulating the infiltration and migration of nitrosamines and its test method. Background Art

[0002] Nitrosamines are a class of organic pollutants containing nitroso groups, with the general chemical formula R1(R2)N—N=O. Currently, more than 300 homologues have been reported. Nitrosamine compounds are listed by the International Agency for Research on Cancer (IARC) as highly toxic and highly carcinogenic organic pollutants to humans and animals. They are globally recognized as the third largest carcinogen after aflatoxin and dioxins. Nitrosamines are widely present in environmental water bodies such as surface water and groundwater. Due to their strong water solubility, they are easily transported vertically in the soil through leaching. This migration process may not only cause soil pollution, but may also further pollute the groundwater system, posing a serious threat to human health and the ecosystem.

[0003] At present, the research on the migration of nitrosamines in groundwater environment is still mainly at the stage of macroscopic observation in the field, and there is a lack of research on the microscopic migration behavior and mechanism of nitrosamines. Most of the existing soil column leaching devices can only analyze soil or leachate separately, and some devices have complex structures and inconvenient sampling, making it difficult to achieve effective linkage between soil interstitial fluid and soil leachate, and thus unable to accurately analyze the dynamic change characteristics of pollutant migration. During the infiltration of pollutants, the environmental behavior of organic pollutants is mainly affected by soil adsorption, ion exchange and microbial degradation. This experimental device can comprehensively examine these three factors and conduct indoor simulation experiments on the vertical migration of nitrosamines in the environment. By simulating the process of pollutant infiltration and migration caused by surface runoff washing pollutants, the instantaneous distribution and migration law of nitrosamines in soil interstitial fluid and soil leachate over time are jointly analyzed to explore the migration and transformation mechanism of nitrosamines in the surface water-soil-groundwater system. Summary of the invention

[0004] In order to solve the deficiencies in the background technology, the present invention designs a device capable of analyzing the dynamic change characteristics of nitrosamine compounds in soil and leachate. The device is equipped with sampling ports of different depths, and can accurately analyze the longitudinal distribution characteristics of pollutants in soil and leachate through multi-level sampling. The device has a simple structure, convenient operation, efficient sampling process, and good practicality and ease of use.

[0005] This is achieved through the following scheme, including the steps:

[0006] The invention discloses a soil column leaching device and a test method for simulating the infiltration and migration of nitrosamines, comprising a leaching soil column pipe, test soil and a soil column support platform, characterized in that a sprinkler head simulating surface runoff scouring is arranged on the top of the leaching soil column pipe, a soil leachate collecting bottle is arranged at the bottom of the soil column support platform, and the soil leachate collecting bottle is connected to the bottom of the leaching soil column pipe through a funnel arranged above the bottle.

[0007] [1] Preferably, the eluvial soil column tube and the soil column support platform are both made of plexiglass, wherein the inner diameter of the eluvial soil column tube is 15 cm and the height is 110 cm, the height of the soil column support platform is 30 cm, and the side length of the platform is 20 cm.

[0008] [2] Preferably, the sprinkler head is connected to the peristaltic pump and the water supply tank in sequence through a water inlet pipe.

[0009] [3] Preferably, the filling height of the test soil is 100 cm, and the reserved water injection space at the top is 10 cm.

[0010] [4] Preferably, the eluvial soil column tube is provided with 10 sampling ports every 10 cm from bottom to top, starting from 10 cm from the bottom.

[0011] [5] Preferably, the inlet of the funnel overlaps with the bottom of the eluvial soil column tube, and the overlapping surface is provided with evenly distributed holes with an inner diameter of 1 cm. The outlet of the funnel extends into the soil leachate collection bottle with an insertion length of 1 cm.

[0012] [6] Preferably, the inner diameter of the sampling port is 15 mm, and the outlet is covered by a plastic cover with an embedded silicone septum, and a sampling tube with an inner diameter of 4 mm runs through the inside of the sampling port.

[0013] [7] Preferably, the sampling tube is inserted 6 cm into the eluvial soil column tube and extends 3 cm outside the sampling port, and the outlet of the sampling tube is provided with a rotary locking device.

[0014] The advantages and beneficial effects of the patent of this invention are:

[0015] This device can collect soil interstitial fluid and soil leaching liquid at different times and different soil layers separately and multiple times, realize the simultaneous linkage analysis of soil interstitial fluid and soil leaching liquid while avoiding mutual interference, and the sampling data is rich, and the experimental results are more real and effective. The device has a simple design structure, low production cost, easy loading and unloading and maintenance, and has good practicality and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the patent structure of the present invention.

[0017] Figure 2 The concentration of nitrosamines in different layers of soil columns in the experimental group changes with time.

[0018] Figure 3 The concentration of nitrosamines in different layers of the sterilized soil column changes with time.

[0019] Figure 4 The changes of nitrosamines in the soil column leachate of the experimental group (a) and the sterilization group (b) over time.

[0020] Numbers in the attached figure: 1-water supply tank, 2-peristaltic pump, 3-water inlet pipe, 4-sprinkler head, 5-sampling port, 6-sampling tube, 7-leaching soil column tube, 8-plastic cover, 9-rotary locking device, 10-test soil, 11-soil column support platform, 12-funnel, 13-soil leachate collection bottle, 14-soil sterilizer. DETAILED DESCRIPTION

[0021] The present invention discloses a soil column leaching device and a test method for simulating the infiltration and migration of nitrosamines, comprising a leaching soil column pipe 7, test soil 10 and a soil column support platform 11, characterized in that a sprinkler head 4 simulating surface runoff scouring is arranged on the top of the leaching soil column pipe 7, a soil leachate collecting bottle 13 is arranged at the bottom of the soil column support platform 12, and the soil leachate collecting bottle 13 is connected to the bottom of the leaching soil column pipe 7 through a funnel 12 arranged above it.

[0022] [1] The eluvial soil column tube 7 and the soil column support platform 11 are both made of plexiglass, wherein the inner diameter of the eluvial soil column tube 7 is 15 cm and the height is 110 cm, the height of the soil column support platform 11 is 30 cm, and the side length of the platform is 20 cm.

[0023] [2] The spray head 4 is connected to the peristaltic pump 2 and the water supply tank 1 in sequence through the water inlet pipe 3.

[0024] [3] The filling height of the test soil 10 is 100 cm, and the water injection space reserved at the top is 10 cm.

[0025] [4] The eluvial soil column tube 7 is provided with 10 sampling ports 5 at intervals of 10 cm from the bottom to the top.

[0026] [5] The inlet of the funnel 12 overlaps with the bottom of the eluvial soil column tube 7, and the overlapping surface is provided with evenly distributed holes with an inner diameter of 1 cm. The outlet of the funnel 12 extends into the soil leachate collection bottle 13, and the insertion length is 1 cm.

[0027] [6] The inner diameter of the sampling port 5 is 15 mm, and the outlet is covered by a plastic cover 8 with an embedded silicone septum, and a sampling tube 6 with an inner diameter of 4 mm runs through the interior of the sampling port 5.

[0028] [7] The sampling tube 6 is inserted 6 cm into the eluvial soil column tube 7 and extends 3 cm outside the sampling port 5, and a rotary locking device 9 is provided at the outlet of the sampling tube 6.

[0029] Example 1

[0030] Two leaching soil column tubes 7 made of plexiglass with the same texture and specifications were prepared and marked as the experimental group and the sterilization group respectively. The homogenized test soil 10 was divided into 10 layers according to the field layer. The soil column of the experimental group was directly filled with the test soil 10 layer by layer, while the sterilization group soil column was first mixed with the sterilizer 14 evenly into the test soil 10 of each layer. The sterilizer 14 sampled isothiazolinone at a concentration of 3 mL / L, and then the test soil 10 was filled layer by layer. Subsequently, the two leaching soil column tubes 7 were fully wrapped with shading cloth to avoid light interference, and the soil column was slowly leached with deionized water until saturated. After the soil column was saturated, a mixed sample solution containing 50 mg of each of the four nitrosamines (NDMA, NDBA, NDEA and NPYR) was evenly injected into the surface of the soil column using a standard needle in the dark, and then a 1 cm thick mixed in-situ soil that had been freeze-dried, sieved and homogenized was laid on the top of the soil column. After the preparation work was completed, the appropriate leaching volume was set on the peristaltic pump 2 according to the experimental requirements, and then the experiment was started. The entire experiment was carried out at room temperature of 25 ± 1 °C to simulate the migration process of nitrosamines in the actual environment.

[0031] Example 2

[0032] Migration patterns of nitrosamines in the surface water-soil-groundwater system: On the 1st, 3rd, 7th, 14th, 21st, 36th, 50th, 64th, 92nd, 139th, 153rd and 184th days after spraying deionized water, 1 mL of water samples were extracted from the interstitial liquid sampling port 5 and the leachate collection bottle 13 at different soil layers using a sampling syringe equipped with a 0.45 µm filter. The instantaneous concentrations of nitrosamines in the 11 samples were then detected by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS). The relevant results are shown in Figure 2. Figure 2 and Figure 3As shown. The experimental results show that the infiltration patterns of nitrosamines in the soil columns of the experimental group and the sterilization group are basically the same, both showing that NDMA has the highest detection rate and concentration, followed by NDEA and NPYR. NDBA is only detected in the upper layer samples at the beginning of soil column infiltration, and is less or not detected over time, indicating that sterilization does not change the migration characteristics of nitrosamines in the surface water-soil-groundwater system. At the same time, the experiment also showed that nitrosamine compounds with low octanol / water partition coefficients (such as NDMA, NDEA and NPYR) are more likely to penetrate the soil barrier and migrate into the groundwater with the water flow. This characteristic highlights that such nitrosamine compounds have a higher potential risk of groundwater contamination.

[0033] Example 3

[0034] Degradation of nitrosamines by microorganisms during migration: This example is based on the sampling time design of Example 2. During the 190-day soil column experiment, whenever the leachate collection bottle 13 accumulated to 500 mL, the collection bottle 13 was taken out, the concentration of nitrosamines in the leachate was measured, and a new collection bottle 13 was replaced. The relevant results are shown in Figure 1. Figure 4 As shown. The experimental results showed that NDBA was not detected in the leachate of either the experimental group or the sterilization group. Compared with the experimental group, the total outflow of NDMA (3366> 3314 µg), NDEA (896 > 641 µg) and NPYR (608 > 508 µg) in the leachate of the sterilization group was slightly higher. These results show that in the soil column of the experimental group, the migration process of nitrosamines is accompanied by microbial degradation; in addition, by comparing the results of this example with those of Example 1, it was found that microbial degradation behavior also existed in the leachate collection bottle 13 while the leachate was waiting to be collected to 500 mL. These results further prove that microbial degradation is one of the main degradation pathways of nitrosamines in groundwater, providing an important biological degradation mechanism for the natural removal of nitrosamines in groundwater, which helps to reduce the concentration of nitrosamines in groundwater and improve its environmental safety.

Claims

1. A soil column leaching device for simulating the infiltration and migration of nitrosamines and a test method thereof, characterized in that: The invention comprises a leached soil column tube (7), test soil (10) and a soil column support platform (11), characterized in that a sprinkler head (4) for simulating surface runoff scouring is arranged at the top of the leached soil column tube (7), a soil leachate collection bottle (13) is arranged at the bottom of the soil column support platform (11), and the soil leachate collection bottle (13) is connected to the bottom of the leached soil column tube (7) via a funnel (12) arranged above the leached soil column tube (7).

2. The soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 1, characterized in that: The eluvial soil column tube (7) and the soil column support platform (11) are both made of organic glass, wherein the inner diameter of the eluvial soil column tube (7) is 15 cm and the height is 110 cm, and the height of the soil column support platform (11) is 30 cm and the side length of the platform is 20 cm.

3. A soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 1, characterized in that The spray head (4) is connected to the peristaltic pump (2) and the water supply tank (1) in sequence through the water inlet pipe (3).

4. The soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 1, characterized in that: The filling height of the test soil (10) is 100 cm, and the reserved water injection space at the top is 10 cm.

5. The soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 1, characterized in that: The eluvial soil column tube (7) is provided with 10 sampling ports (5) at intervals of 10 cm from the bottom from bottom to top.

6. A soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 1, characterized in that: The inlet of the funnel (12) overlaps with the bottom of the eluvial soil column tube (7), and the overlapping surface is provided with evenly distributed holes with an inner diameter of 1 cm. The outlet of the funnel (12) extends 1 cm into the soil leachate collection (13) bottle.

7. A soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 5, characterized in that: The inner diameter of the sampling port (5) is 15 mm, and the outlets are covered by plastic covers (8) embedded with silicone septa, and a sampling tube (6) with an inner diameter of 4 mm runs through the interior of the sampling port (5).

8. A soil column leaching device and test method for simulating the infiltration and migration of nitrosamines according to claim 5 or 7, characterized in that: The sampling tube (6) is inserted 6 cm into the eluvial soil column tube (7) and extends 3 cm outside the sampling port (5), and a rotary locking device (9) is provided at the outlet of the sampling tube (6).

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