A layered sampling experiment device and a continuous dynamic monitoring method for simulating the effect of intermittent input of new pollutants on groundwater soluble N2O biological conversion

Abstract

The application provides a kind of simulation new pollutant intermittent input mode under the action of groundwater soluble N2O biological conversion layered sampling experimental device and continuous dynamic monitoring method, belongs to groundwater pollution control experimental technical field.Simulation new pollutant intermittent input mode under the action of groundwater soluble N2O biological conversion layered sampling experimental device mainly includes groundwater simulation experimental column, liquid inlet and mixing system, microelectrode monitoring system and layered sampling component;The experimental column is arranged in parallel, and is connected with liquid inlet and mixing system by peristaltic pump, realizes soluble N2O stable liquid inlet, and simulates different input modes by regulating and controlling new pollutant input concentration and frequency;The layered sampling component is used for pore water and microbial sample collection, and microelectrode is used for continuous monitoring of soluble N2O.The application can simulate different input modes of new pollutants in groundwater, realize layered sampling and continuous monitoring, and is suitable for studying the influence of new pollutants on the biological conversion process of soluble N2O in groundwater.

Description

Technical Field

[0001] This invention relates to the field of experimental technology for groundwater pollution control, specifically to a stratified sampling experimental device and a continuous dynamic monitoring method for the biological transformation of dissolved N2O in groundwater under the simulated intermittent input of new pollutants. Background Technology

[0002] Nitrous oxide (N2O) is an important greenhouse gas. Under certain conditions, groundwater can act as both an acceptor and a potential source of N2O. In recent years, with the increase in agricultural activities, irrigation with aquaculture wastewater, and leaching of soils contaminated with new pollutants by rainfall, the problem of residual new pollutants in the groundwater environment has received increasing attention.

[0003] In real-world environments, the entry of new pollutants into shallow groundwater is typically not a continuous and stable input, but rather exhibits distinct intermittent input characteristics. Specifically, irrigation with aquaculture wastewater tends to result in high-concentration, low-frequency inputs, while leaching from contaminated soil through rainfall tends to result in low-concentration, high-frequency inputs. These different input methods not only affect the exposure level and duration of new pollutants in groundwater but may also further influence the N2O biotransformation process within the groundwater.

[0004] Existing groundwater column experimental setups are mainly used for studies on nitrate migration, denitrification processes, or single pollutant transport, and cannot simultaneously meet the requirements for stable input of dissolved N2O, simulation of intermittent input of new pollutants, and continuous monitoring and sampling at multiple locations. Therefore, it is necessary to provide an experimental setup and method capable of simulating different new pollutant input scenarios and achieving continuous dynamic monitoring, providing technical support for revealing the influence and mechanism of new pollutant input on the biotransformation process of dissolved N2O in groundwater. Summary of the Invention

[0005] The purpose of this invention is to provide a stratified sampling experimental device and a continuous dynamic monitoring method for the biotransformation of dissolved N2O in groundwater under the simulated intermittent input of new pollutants. This device can simulate two typical environmental exposure scenarios: high-concentration, low-frequency input and low-concentration, high-frequency input, achieving stable supply of dissolved N2O, multi-layer pore water and microbial sample collection within the column, and continuous N2O monitoring.

[0006] To achieve the above objectives, this invention provides a stratified sampling experimental device for the biotransformation of dissolved N2O in groundwater under simulated intermittent input of new pollutants. Its main technical features include: an experimental column assembly, a liquid inlet and mixing assembly, a new pollutant input assembly, a continuous monitoring assembly, a stratified pore water sampling assembly, and a microbial sampling assembly. The experimental column assembly comprises three parallel groundwater simulation columns, serving as a control column and experimental groups for different new pollutant input methods, respectively. The liquid inlet and mixing assembly is connected via pipelines to a basic culture medium storage bottle, an N2O saturated solution storage bottle, and a new pollutant storage bottle, respectively, and the mixture is then input into each experimental column. The continuous monitoring assembly includes a multi-channel microelectrode main unit and a stainless steel N2O microelectrode for continuous monitoring of dissolved N2O within the experimental column. The stratified pore water sampling assembly is located on the side wall of the experimental column for collecting pore water samples from different strata. The microbial sampling assembly is located at the corresponding strata of the experimental column for obtaining microbial samples at different strata.

[0007] Preferably, the experimental column is a vertical cylindrical structure, filled with quartz sand medium, with a liquid outlet, electrode insertion port and sealing structure at the top, several layered sampling ports along the vertical sidewalls, and a liquid inlet at the bottom. Three experimental columns are arranged in parallel for experiments under different conditions and for parallel controls.

[0008] Preferably, the liquid inlet and mixing assembly includes a basic culture medium storage bottle, an N2O saturated solution storage bottle, a new contaminant storage bottle, infusion tubing, a peristaltic pump, and a mixer; the basic culture medium, N2O saturated solution, and new contaminant solution are respectively transported through independent tubing according to the instruction manual 100002 2023.03 2, and are mixed in the mixer before entering the experimental column, thereby forming a liquid inlet containing dissolved N2O of the target concentration.

[0009] Preferably, the new pollutant input component simulates both high-concentration, low-frequency and low-concentration, high-frequency input modes of the new pollutant by controlling the input time, input frequency, and flow rate of the new pollutant solution.

[0010] Preferably, the continuous monitoring component includes a multi-channel microelectrode host and four stainless steel N2O microelectrodes, wherein three N2O microelectrodes are inserted into three experimental columns respectively, and the fourth N2O microelectrode serves as a backup electrode.

[0011] Preferably, the stratified pore water sampling assembly includes a stratified sampling port, a connecting pipeline, a sealing interface, and a pore water sampler; the pore water sampler is located at the sampling port position on the side wall of the experimental column and is in contact with the medium inside the column, and is used to extract pore water samples in layers; during sampling, an airtight syringe and a sealed sample bottle are used to reduce the loss of dissolved N2O during sampling and transfer.

[0012] Preferably, the microbial sampling assembly includes microbial samplers located at sampling ports on the sidewalls of different layers of the experimental column. The microbial samplers are horizontally installed on the sidewalls of the experimental column and extend into the packing layer inside the column. They include a PTFE sealing section and a sampling section connected in sequence, as well as a nylon flocked carrier disposed within the sampling section. The PTFE sealing section located outside the column has a non-porous structure and a sealing cap at its outer end. An O-ring seal is provided between the sealing cap and the fixed sleeve to ensure the sealing performance during device operation. The end extending into the packing layer is the sampling section, which is made of hydrophilic modified PTFE and pre-wetted to allow pore water to enter the sampling section while preventing packing particles from entering. The nylon flocked carrier disposed within the sampling section is used for microbial attachment and enrichment and can be removed axially along the sleeve for analysis. After sampling, the sampling assembly remains on the column sidewall, thereby avoiding disturbance to the packing structure and hydraulic channels.

[0013] The present invention also provides a method for continuous dynamic monitoring of the biological transformation of dissolved N2O in groundwater using the above-mentioned experimental apparatus, comprising the following steps:

[0014] The first step is to prepare the basic culture medium, N2O saturated solution and new pollutant storage solution required for the experiment, and put them into the corresponding storage bottles for later use; fill the three experimental columns with quartz sand medium, and install the stratified pore water sampling component, microbial sampling component and N2O microelectrode.

[0015] The second step is to connect the experimental column to the inlet and mixing components, the new pollutant input component, and the outlet, so that the entire device is in a sealed operating state; the flow rate is adjusted by the peristaltic pump at the outlet end, so that the experimental column can operate stably under the set hydrodynamic conditions.

[0016] The third step involves introducing a solution containing dissolved N2O into the experimental column without adding any new pollutants to acclimate the system and enable the microorganisms within the column to establish a stable capacity for the biotransformation of dissolved N2O.

[0017] The fourth step involves setting up a control group, a high-concentration low-frequency input group, and a low-concentration high-frequency input group after the system has stabilized. The input concentration, input time, and input frequency of the new pollutant solution are controlled by the new pollutant input component to simulate different intermittent input scenarios of the new pollutant.

[0018] The fifth step involves continuously recording the changes in dissolved N2O concentration within each experimental column using a multi-channel microelectrode host during the experiment, and collecting pore water and microbial samples from different strata at preset time points to dynamically analyze the biotransformation process of dissolved N2O in groundwater.

[0019] The present invention has the following beneficial effects: The stratified sampling experimental device for the biotransformation of dissolved N2O in groundwater under the simulated intermittent input of new pollutants provided by the present invention can achieve stable input of dissolved N2O, simulation of intermittent input of new pollutants, and stratified sampling. It can realistically simulate two types of new pollutant input scenarios in groundwater: high concentration at low frequency and low concentration at high frequency. The device uses three experimental columns arranged in parallel, which helps to improve the accuracy and comparability of the experimental results.

[0020] The continuous dynamic monitoring method provided by this invention enables continuous monitoring of dissolved N2O during experimental operation. Combined with stratified water and microbial sample collection, it allows for dynamic analysis of the biotransformation process of dissolved N2O in groundwater. This method improves the temporal resolution of process data, which is beneficial for revealing the changing characteristics and mechanisms of dissolved N2O biotransformation in groundwater under different intermittent input modes of new pollutants. Attached Figure Description

[0021] Figure 1 – Schematic diagram of the structural principle of the present invention

[0022] Figure 2 – Schematic diagram of the microbial sampling unit structure

[0023] The names of the parts corresponding to the labels in the figure are as follows: 1-Basic culture medium bottle, 2-N2O saturated liquid bottle, 3-New pollutant storage bottle, 4-Peristaltic pump, 5-Mixer, 6-Experimental column, 7-Porous water sampling port, 8-Microbial sampling unit, 9-N2O microelectrode, 10-Microelectrode main unit, 11-Outlet water bottle, 12-Hydrophilic modified PTFE sampling section, 13-PTFE sealing section, 14-Nylon flocked carrier, 15-Sealing cap. Detailed Implementation

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] As shown in Figures 1-2, the present invention provides a stratified sampling experimental device for the biotransformation of dissolved N2O in groundwater under the simulated intermittent input of new pollutants. The device includes a basic culture medium bottle 1, an N2O saturated liquid bottle 2, a new pollutant storage bottle 3, a multi-channel peristaltic pump 4, a mixer 5, three parallel experimental columns 6, a pore water sampling port 7, a microbial sampling unit 8, an N2O microelectrode 9, a microelectrode host 10, and a water outlet bottle 11 located at the outlet end of the experimental column 6. The microbial sampling structure includes a hydrophilic modified PTFE sampling section 12, a PTFE sealing section 13, a nylon flocked carrier 14, and a sealing cap 15. The basic culture medium, N2O saturated liquid, and new pollutant solution are respectively transported by the peristaltic pump 4, mixed in the mixer 5, and then enter the experimental column 6.

[0026] Three experimental columns 6 are arranged in parallel, serving as a control column, a low-concentration high-frequency input column, and a high-concentration low-frequency input column, respectively. Each experimental column 6 is a vertical cylindrical structure with an inner diameter of 60 mm and a height of 500 mm, filled with quartz sand medium. Multiple pore water sampling ports 7 are vertically arranged on the sidewalls of the experimental column 6 for collecting stratified pore water and microbial samples. The top of the experimental column 6 has an outlet and an electrode insertion port, and the bottom has an inlet.

[0027] The basic culture medium bottle 1, the N2O saturated solution bottle 2, and the new contaminant storage bottle 3 are each connected to a peristaltic pump 4. The basic culture medium, N2O saturated solution, and new contaminant solution are transported to a mixer 5 via independent pipelines, mixed, and then distributed to the experimental column 6. The outlet end of the experimental column 6 is connected to a water outlet bottle 11. The continuous monitoring component includes a microelectrode host 10 and four N2O microelectrodes 9, of which three N2O microelectrodes 9 are inserted into three experimental columns 6 respectively, and the fourth N2O microelectrode 9 serves as a spare electrode.

[0028] The pore water sampling port 7 is equipped with a corresponding pore water sampler, which contacts the medium inside the column for stratified extraction of pore water samples. An airtight syringe is used to connect the pore water sampler during sampling to minimize the loss of dissolved N2O during sampling and transfer.

[0029] The microbial sampling structure is located at the pore water sampling port 7 of the corresponding layer of the experimental column 6. The microbial sampling unit 8 is horizontally installed on the side wall of the experimental column 6 and extends into the packing layer inside the column. The sealing cap 15 is located at the outer end of the PTFE sealing section 13, and an O-ring is located between the sealing cap 15 and the PTFE sealing section 13 to ensure the airtightness of the device during operation. The hydrophilic modified PTFE sampling section 12 is located at the end of the microbial sampling unit 8 that extends into the packing layer, and is pre-wetted before installation to allow pore water to enter the interior of the sampling section while preventing packing particles from entering the sampling unit.

[0030] The microbial sampling unit 8 extends 25 mm into the packing layer, and the PTFE sealing section is 15 mm long. The nylon flocked carrier 14 is placed inside the hydrophilic modified PTFE sampling section 12 for microbial attachment, growth, and subsequent sample collection. During microbial sampling, the sealing cap 15 is opened, and the nylon flocked carrier 14 is removed axially for microbial analysis. The microbial sampling unit 8 remains on the sidewall of the experimental column 6 to maintain the stability of the packing layer structure and flow channels within the column. (Instruction manual 100002 2023.03 4)

[0031] This invention discloses a stratified sampling experimental device and continuous dynamic monitoring method for the biological transformation of dissolved N2O in groundwater under simulated intermittent input of new pollutants, comprising the following steps:

[0032] The first step is to prepare the basic culture medium, N2O saturated solution and new pollutant storage solution, and put them into the basic culture medium bottle 1, N2O saturated solution bottle 2 and new pollutant storage solution bottle 3 respectively; fill the three experimental columns 6 with quartz sand medium, and install the pore water sampling port 7, microbial sampling unit 8, N2O microelectrode 9 and water outlet bottle 11.

[0033] The second step is to connect the liquid storage bottles, mixer 5, and experimental column 6 in sequence to ensure the entire device is in a sealed operating state; the flow rate is adjusted by the peristaltic pump 4 to ensure the stable operation of the experimental column 6.

[0034] The third step involves introducing a mixture of N2O saturated solution and basic culture medium into experimental column 6 without adding new pollutants, to acclimate the system and enable the microorganisms within the column to establish a stable capacity for soluble N2O biotransformation.

[0035] Fourth, after the system stabilizes, set up a control column, a high-concentration low-frequency input column, and a low-concentration high-frequency input column respectively; the control column does not introduce new pollutants throughout the process; by controlling the input concentration, input time, and input frequency of the new pollutant solution, simulate different intermittent input scenarios of new pollutants.

[0036] The fifth step involves continuously monitoring the changes in dissolved N2O concentration in each experimental column 8 using N2O microelectrode 9, and collecting pore water and microbial samples from different strata at preset time points to analyze the biotransformation process of dissolved N2O in groundwater.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept and essence of the present invention, and these modifications, improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A stratified sampling experimental device for the biological transformation of dissolved N2O in groundwater under simulated intermittent input of new pollutants, characterized in that: The experimental apparatus includes a basic culture medium bottle (1), an N2O saturated liquid bottle (2), a new contaminant storage bottle (3), a peristaltic pump (4), a mixer (5), at least three parallel experimental columns (6), a pore water sampling port (7), a microbial sampling unit (8), an N2O microelectrode (9), a microelectrode host (10), and a water outlet bottle (11) located at the water outlet end of the experimental column (6). The experimental column (6) is a vertical cylindrical structure with an inner diameter of approximately 60 mm and a height of approximately 500 mm, filled with quartz sand medium. Each experimental column (6) has multiple pore water sampling ports (7) arranged vertically on its sidewalls, an outlet and an electrode insertion port at the top, and an inlet at the bottom. The basic culture medium bottle (1), N2O saturated liquid bottle (2), a new contaminant storage bottle (3), a peristaltic pump (4), a mixer (5), at least three parallel experimental columns (6), a pore water sampling port (7), a microbial sampling unit (8), an N2O microelectrode (9), a microelectrode host (10), and a water outlet bottle (11) located at the water outlet end of the experimental column (6). The saturated liquid bottle (2) and the new pollutant storage bottle (3) are respectively connected to the peristaltic pump (4) and transported to the mixer (5) through independent pipelines for mixing and then distributed to the experimental column (6); the liquid outlet of the experimental column (6) is connected to the water outlet bottle (11) through a silicone tube; the microbial sampling unit (8) includes a hydrophilic modified PTFE sampling section (12), a PTFE sealing section (13), a nylon flocked carrier (14) and a sealing cap (15). The microbial sampling unit (8) is installed horizontally on the side wall of the experimental column (6) and extends into the packing layer inside the column. The hydrophilic modified PTFE sampling section (12) is pre-wetted to allow pore water to enter the sampling section and block the packing particles at the same time; the nylon flocked carrier (14) is used for microbial attachment and growth and subsequent sample collection. It is taken out along the axial direction during sampling. After completion, the microbial sampling unit (8) continues to remain on the side wall of the column to maintain the stability of the packing layer structure and flow channel; The continuous monitoring component includes a microelectrode host (10) and an N2O microelectrode (9), wherein three N2O microelectrodes (9) are inserted into three experimental columns (6) respectively, and the fourth N2O microelectrode (9) is reserved for continuous monitoring of the change in the concentration of dissolved N2O in the experimental column (6).

2. The experimental apparatus according to claim 1, characterized in that: The three experimental columns (6) serve as the control column, the high-concentration low-frequency input column, and the low-concentration high-frequency input column, respectively. The control column does not input new pollutants. The high-concentration low-frequency input column and the low-concentration high-frequency input column achieve different intermittent input modes of new pollutants by controlling the input concentration, input time and input frequency of the solution in the new pollutant storage bottle (3).

3. A method for stratified sampling of dissolved N2O in groundwater through biotransformation using the experimental apparatus described in claim 1, characterized in that, The method includes the following steps: First, prepare the basic culture medium, N2O saturated solution, and new pollutant solution, and put them into the basic culture medium bottle (1), N2O saturated solution bottle (2), and new pollutant storage bottle (3), respectively. Fill the three experimental columns (6) with quartz sand medium and install the pore water sampling port (7), microbial sampling unit (8), N2O microelectrode (9), and water outlet bottle (11). Second, connect the storage bottles, mixer (5), and experimental columns (6) in sequence to make the device run in a sealed manner. Adjust the flow rate by the peristaltic pump (4) to make the experimental column (6) run stably. Third, without adding new pollutants, introduce a mixture of N2O saturated solution and basic culture medium into the experimental column (6) for acclimatization, so that the microorganisms in the column can establish a stable soluble N2O biotransformation capacity. The fourth step is to set up the experimental column (6) as a control column, a high-concentration low-frequency input column and a low-concentration high-frequency input column, and to simulate different intermittent input scenarios by adjusting the input concentration, time and frequency of the solution in the new pollutant storage bottle (3). The fifth step involves continuously monitoring the changes in dissolved N2O concentration in each experimental column (6) using N2O microelectrodes (9) during the experiment, and collecting pore water samples and microbial samples from different strata at preset time points to analyze the biotransformation process of dissolved N2O in groundwater.

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