CN115201448A - Method and device for analyzing release and migration characteristics of polybrominated diphenyl ethers in polluted site - Google Patents
Method and device for analyzing release and migration characteristics of polybrominated diphenyl ethers in polluted site Download PDFInfo
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Abstract
The invention discloses a method for analyzing release and migration characteristics of polybrominated diphenyl ethers in a polluted site, which comprises the following steps: step 1, sampling in situ in a polluted site to obtain an undisturbed soil column; preparing a simulated rainwater solution or collecting rainwater in a polluted site; step 2, filling the undisturbed soil column into a rock core holder; step 3, pre-washing the undisturbed soil column; and 4, carrying out a leaching experiment: pumping the simulated rainwater solution or rainwater collected in a polluted site into the core holder for leaching at constant pressure and constant flow through the water inlet, and respectively collecting the leaching solution flowing out of each water outlet port; and 5, measuring the water flux of each water outlet port, measuring the concentration of PBDEs in the leaching solution flowing out of each water outlet port, and analyzing the release and migration characteristics of the polybrominated diphenyl ethers in the polluted site according to the detection result. The method can accurately reflect the release characteristics of the PBDEs in the soil of the polluted site and characterize the influence of the preferential flow path on the PBDEs release.
Description
Technical Field
The invention relates to the technical field of environment, in particular to a method and a device for analyzing release and migration characteristics of polybrominated diphenyl ethers in a polluted site based on an undisturbed soil column leaching experiment.
Background
Under the background of shortage of land resources and urban land in China, restoration, development and reuse of polluted fields are important national requirements which are important for people to benefit. Polybrominated diphenyl ethers (PBDEs) are Persistent Organic Pollutants (POPs) widely existing in the environment, and due to the characteristics of environmental persistence, long-distance transmission, bioaccumulation, toxic effect on organisms and human bodies and the like, research on environmental problems becomes a hot spot of current environmental science. PBDEs are produced in 80 th of the 20 th century in China, and become one of the main producing countries of decabromodiphenyl ether (BDE-209) in 2000. PBDEs are widely added into plastic products and the like as brominated flame retardants, but the PBDEs are easy to escape from products and enter the environment, so that environmental pollution is caused; researches have found that the content of PBDEs in the environment such as soil is increased year by year after 80 years in the 20 th century. Only for electronic products, PBDEs exist in circuit boards, electronic components, cables, plastic housings, keyboards and displays, and with the disposal of a large number of electronic products as electronic waste after use, PBDEs pollution to the environment can be caused, especially PBDEs pollution in soil is serious in the field where electronic waste is disassembled and collected. PBDEs in surface soils may be released into the soil interstitial water and migrate down to underground aquifers, causing groundwater contamination.
At present, batch experiments (batch test) and packed column experiments in laboratories, lysimeter experiments in fields and the like are mostly adopted for research on the release and migration behaviors of PBDEs in soil. The batch experiment is to add soil into water to prepare soil suspension, then to stir or oscillate for a certain time, and to sample and determine the release of pollutants released into the water phase or colloid. The method destroys the soil structure, and can not simulate the water flow condition in the soil medium, and the measured pollutant release capacity is generally far higher than that of the actual soil. The packed homogeneous soil column is used for pollutant release and migration experiments, compared with batch experiments, the packed homogeneous soil column is closer to actual soil conditions, and hydrodynamic conditions of underground aquifers can be simulated to a certain extent, but a common preferential flow path in soil generally does not exist in the packed column, and the pollutant release and migration capability in the soil cannot be accurately evaluated. The lysimeter experiment is carried out on site, can accurately predict the pollutant release characteristics under actual conditions, but has long experiment period and high cost. Therefore, a new experimental method must be developed to reveal the release and migration characteristics of POPs such as PBDEs in complex underground porous media.
Aiming at the problems, the invention develops an undisturbed soil column leaching experimental method which is used for researching the release and migration characteristics of PBDEs in actual soil. The method selects typical PBDEs in the polluted site as a research object, collects the undisturbed soil column, inspects the influence of the water chemistry conditions (such as pH and ionic strength) on the PBDEs released by the undisturbed soil column through the leaching experiment carried out in the core holder, researches the influence of soil heterogeneity and complex water chemistry conditions on the migration characteristics of the PBDEs, and has great significance for researching the problem of how the interaction of complex water chemistry factors influences the migration capability of organic pollutants and the like.
Disclosure of Invention
The invention aims to provide a method for analyzing release and migration characteristics of polybrominated diphenyl ethers in a polluted site based on an undisturbed soil column leaching experiment, aiming at the technical defects of PBDEs release and migration behavior analysis in soil in the prior art.
In another aspect of the present invention, an apparatus for analyzing the release and migration characteristics of polybrominated diphenyl ethers in contaminated sites is provided.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a method for analyzing release and migration characteristics of polybrominated diphenyl ethers in a contaminated site, comprising the steps of:
preparing a simulated rainwater solution or collecting rainwater in a polluted site;
and 4, carrying out a leaching experiment: pumping the simulated rainwater solution or rainwater collected in a polluted site into the core holder for leaching through the water inlet at constant pressure and constant flow, and respectively collecting the leaching solution flowing out of each water outlet port;
and 5, measuring the water flux of each water outlet port, measuring the concentration of PBDEs in the leaching solution flowing out of each water outlet port, and analyzing the release and migration characteristics of the polybrominated diphenyl ethers in the polluted site according to the detection result.
In the above technical solution, in the step 1, the undisturbed soil column to be detected is obtained by the following method: removing vegetation on the surface layer of the soil, then collecting an original-state soil column at the depth of 0-10 cm on the surface layer by using a pulse sampler, sealing the bottom of the pulse sampler by using a sealing film after the original-state soil column is collected, sleeving a protective sleeve on the pulse sampler, and transporting the soil to a laboratory for storage in a refrigerator.
In the above technical solution, in the step 1, when preparing the simulated rainwater solution, two sets of simulated rainwater solutions are prepared, one set of simulated rainwater solutions with the same pH and different ionic strengths, and the other set of simulated rainwater solutions with the same ionic strength and different phs;
preferably, one of the two sets of simulated rainwater solutions has a pH of 5.6 and ionic strengths of 10, 5, 1, 0.1 and 0.01mM, and the other set of simulated rainwater solutions has an ionic strength of 1mM and pH values of 4.0, 6.0, 8.0 and 10.0, respectively.
In the above technical solution, in the step 2, the undisturbed soil column and the pulse sampler are placed together in the core holder.
In the above technical scheme, in the step 3, the pre-washing time is 24-48h, and the drainage time of the undisturbed soil column under the action of gravity is 16-20h.
In the above technical scheme, in the step 4, the leaching time is 4-8h in each leaching experiment, and the drainage time of the undisturbed soil column under the action of gravity is 16-20h after each leaching experiment;
when analyzing the influence of rainwater with different ionic strengths on the release characteristics of polybrominated diphenyl ethers in a polluted site, carrying out leaching experiments for one time by sequentially using simulated rainwater solutions with pH of 5.6 and ionic strengths of 10, 5, 1, 0.1 and 0.01mM respectively, and collecting the leaching solution flowing out of each water outlet port at intervals of 20-40min during each leaching experiment;
when analyzing the influence of rainwater with different ion pH values on the release characteristics of polybrominated diphenyl ethers in a polluted site, carrying out leaching experiments in sequence by using simulated rainwater solutions with ion strength of 1mM and pH values of 4.0, 6.0, 8.0 and 10.0 respectively, and collecting the leaching solution flowing out of each water outlet port at intervals of 20-40min during each leaching experiment.
In the above technical solution, in the step 5, the water flux = the volume of the collected leaching solution per unit time of each water outlet port divided by the port area.
In the above technical solution, in the step 5, the determination of PBDEs comprises the following steps:
step s1, extracting PBDEs in the eluated solution, transferring the eluated solution into a brown bottle, adding BDE-77 as a recovery rate indicator, then adding n-hexane and oscillating for liquid-liquid extraction for multiple times, mixing the extraction solutions obtained by multiple operations, then blowing nitrogen, fixing the volume to 1mL by using the n-hexane, oscillating in a vortex manner, absorbing the extraction solution, filtering the extraction solution by using a 0.22-micron organic phase nylon filter, transferring the filtered extraction solution into a gas phase sample bottle, adding BDE-118 as an internal standard, and placing the internal standard in a refrigerator for storage to serve as a liquid to be detected;
and step s2, using a gas chromatography-mass spectrometer to measure the types and the concentrations of the PBDEs in the solution to be measured.
In the above technical solution, in the step s2, the gas chromatograph-mass spectrometer chromatographic column is an Rtx-1614 capillary column (15 m × 0.25mm × 0.10 μm). The carrier gas is helium, the flow rate is 2mL/min, the sample is injected without shunting, and the sample injection amount is 1 mu L.
The temperature rising procedure is as follows: keeping the temperature at 110 ℃ for 3min, raising the temperature to 200 ℃ at the speed of 25 ℃/min, raising the temperature to 280 ℃ at the speed of 15 ℃/min, then raising the temperature to 305 ℃ at the speed of 20 ℃/min, keeping the temperature for 5min, and finally, 18.183min.
The mass spectrum conditions are as follows: negative Chemical Ion (NCI) source, selected Ion Monitoring (SIM) mode, ion source temperature 250 ℃ and transmission line temperature 280 ℃. The BDE-209 quantitative ions are fragment ions with mass-to-charge ratios (m/z) of 466 and 468, and the other PBDEs quantitative ions are bromide ions (m/z of 79 and 81).
In the above technical scheme, in the step 5, the water outlet port with the largest water flux is used as a main water outlet port, the total release rate of polybrominated diphenyl ethers in the leaching solution of each water outlet port is calculated, the release and vertical migration capabilities of polybrominated diphenyl ethers in the surface soil of the polluted site under specific conditions are predicted, and the release heterogeneity of the polybrominated diphenyl ethers is analyzed by comparing the flow rate of the leaching solution of the main water outlet port and other water outlet ports with the content difference of the polybrominated diphenyl ethers.
In another aspect of the present invention, a device for analyzing release and migration characteristics of polybrominated diphenyl ethers in a contaminated site comprises a double-cylinder constant-pressure constant-flow pump, a piston container, a core holder and a water collection funnel, wherein: the water inlet of the double-cylinder constant-pressure constant-flow pump is connected with ultrapure water, the water outlet of the double-cylinder constant-pressure constant-flow pump is connected to the inlet of the piston container through a pipeline, a simulated rainwater solution is filled in the piston container, the outlet of the piston container is connected to the water inlet of the core holder through a water supply pipeline, an inlet pressure gauge is arranged on the water supply pipeline, an undisturbed soil column is filled in the core holder, a screen is arranged below the undisturbed soil column to prevent soil particles from flowing out, the bottom of the core holder is provided with N water outlet ports, one water outlet port is arranged at a central position and is a central water outlet port, the rest water outlet ports are symmetrically arranged by taking the central water outlet port as a center, each water outlet port is connected with a water collecting funnel, and a leaching solution flowing out of the water outlet port is collected into a sample receiving pipe at the lower part through the water collecting funnel;
the prepared simulated rainwater solution is stored in the piston container, the simulated rainwater solution is pumped into the original-state soil column by the double-cylinder constant-pressure constant-flow pump at constant pressure and constant flow rate, and the leaching solution flows out through the water outlet port after the original-state soil column is leached.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention adopts the undisturbed soil column to carry out leaching experiment, and can accurately reflect the release characteristics of PBDEs in the soil of the polluted site.
2. The invention monitors the release of PBDEs through a plurality of water outlet ports, and can characterize the influence of the priority flow path on the PBDEs release.
Drawings
FIG. 1 is a field diagram of undisturbed soil column collection of a contaminated site, wherein (a) is a pulse sampler and a connecting rod, and (b) is the collected undisturbed soil column.
FIG. 2 is a diagram of an experimental apparatus for leaching undisturbed soil column.
FIG. 3 is a schematic diagram of an undisturbed soil column leaching experimental device. Wherein (a) is a schematic view of the whole device, and (b) is a schematic view of the position of the water outlet port.
FIG. 4 is a graph showing the variation of the flux of the effluent from four outlet ports in different ion intensity eluviation experiments.
Fig. 5 is a water flux change diagram of outflow liquid from four water outlet ports in the process of simulating the leaching of rainwater solution into an undisturbed soil column at different pH values.
In the figure: 1-ultrapure water, 2-double-cylinder constant-pressure constant-flow pump, 3-piston container, 4-simulated rainwater solution, 5-inlet pressure gauge, 6-core holder, 7-water collecting funnel, 8-sample receiving pipe, 9-test tube rack, 10-undisturbed soil column and 11-water outlet port.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
1.1 collecting undisturbed soil column
And (3) selecting a Z1 point position of a certain polluted site to collect an undisturbed soil column (shown in figure 1). Before collecting the soil column, removing surface vegetation, and then collecting the undisturbed soil column on the surface at the depth of 0-10 cm by using a stainless steel pulse sampler with the diameter of 7.5cm (inner diameter) and the depth of 10 cm. After the undisturbed soil column is collected, the bottom of the pulse sampler is sealed by a sealing film and sleeved with a protective sleeve (fixed by a rubber band), and the pulse sampler is transported back to a laboratory and stored in a refrigerator at 4 ℃.
1.2 preparing simulated rainwater solution
Preparing simulated rainwater solutions with different ionic strengths and pH values according to the pH value, the conductivity, the ionic composition and the content of rainwater in Tianjin city as leaching solutions. First, ca (NO) is used 3 ) 2 ·4H 2 O、(NH 4 ) 2 SO 4 、CaCl 2 、KNO 3 、MgSO 4 ·7H 2 O、Na 2 SO 4 The analytical pure-grade drugs are prepared into simulated rainwater stock solution with the ionic strength of 60mM according to the content in the table 1.
Table 1 simulation of rainwater stock pH and ionic molarity
The leaching solutions with different ionic strengths are prepared by the following method: the stock solutions were diluted 6, 12, 60, 600 and 6000 times respectively to obtain eluates with ionic strength: 10. 5, 1, 0.1 and 0.01mM. All leachates were adjusted to pH 5.6 using NaOH and HCl at a concentration of 0.01M.
The leaching solutions with different pH values are prepared by the following method: the stock solution was diluted 60-fold to give a eluviation solution with an ionic strength of 1mM, and the pH was adjusted to 4.0, 6.0, 8.0 and 10.0 using NaOH and HCl at a concentration of 0.1M, respectively.
Example 2
The original-state soil column leaching experimental device is built:
as shown in fig. 3, the original-state soil column leaching experimental device comprises a double-cylinder constant-pressure constant-flow pump 2, a piston container 3, a rock core holder 6 and a water collection funnel 7, wherein: the water inlet of the double-cylinder constant-pressure constant-flow pump 2 is connected with ultrapure water 1, the water outlet of the double-cylinder constant-pressure constant-flow pump is connected to the inlet of the piston container 3 through a pipeline, a simulated rainwater solution 4 is filled in the piston container 3, the outlet of the piston container 3 is connected to the water inlet of the core holder 6 through a water supply pipeline, an inlet pressure gauge 5 is arranged on the water supply pipeline, an undisturbed soil column 10 is filled in the core holder 6, a screen is arranged below the undisturbed soil column to prevent soil particles from flowing out, N water outlet ports 11 are arranged at the bottom of the core holder, one water outlet port is arranged at the central position and is a central water outlet port, the rest water outlet ports are symmetrically arranged by taking the central water outlet port as the center, a water collecting funnel 7 is connected to each water outlet port, and a leaching solution flowing out of the water outlet ports is collected to a sample receiving pipe 8 at the lower part through the water collecting funnel 7.
More specifically, the prepared simulated rainwater solution 4 is stored in the piston container 3, the double-cylinder constant-pressure constant-flow pump 2 pumps the simulated rainwater solution 4 into an original-state soil column 10 at a constant flow rate, a pulse sampler provided with the original-state soil column 10 is arranged in a rock core holder 6, and a screen with the aperture of 200 meshes is arranged below the soil column to prevent large-size soil particles from flowing out. The lower end of the core holder 6 has 7 water outlet ports (each water outlet port has a diameter of 1.6 cm) arranged in the manner shown in fig. 3 (b): wherein 1 water outlet port (numbered as "7 #") is located at the center as a central port, and the other 6 water outlet ports (numbered as "1#" to "6 #") are arranged in a regular hexagon around the central port. Each water outlet port captures 2cm of flowing area 2 Leaching solution; the total collection area was 14cm 2 . The showering solution flows out from a water outlet port at the bottom of the core holder 6, and is collected to a sample receiving pipe 8 through a water collecting funnel 7 (made of polytetrafluoroethylene), wherein the sample receiving pipe 8 is a glass test tube, and the glass test tube is arranged on a test tube rack 9.
Example 3
Utilize the original state earth pillar eluviation experimental apparatus of embodiment 2 building, carry out original state earth pillar eluviation experiment under the different ionic strength condition, including steps such as experiment post prewashing, eluviation experiment and the analysis of drenching solution sample:
(1) Experimental original state soil column pre-washing
Continuously leaching and dissolving the undisturbed soil column for 48 hours by using a simulated rainwater solution with the ionic strength of 0.01mM and the pH of 5.6 at the flow rate of 15mM/h to remove soluble impurities in the undisturbed soil column and balance the moisture content in the undisturbed soil column, then stopping leaching, and draining the original soil column for 18.7 hours under the action of gravity.
(2) Leaching experiment
Simulated rain water solution (pH = 5.6) with ionic strength of 10mM was eluviated to undisturbed soil column for 5.3h, then eluviation was stopped and undisturbed soil column was drained by gravity for 18.7h. And sampling once at 7 water outlet ports at the lower end of the undisturbed soil column every 20min during leaching, and detecting.
The above experimental operation was repeated, and leaching experiments were sequentially performed with the same undisturbed soil column and 5 simulated rainwater solutions of different ionic strengths (pH = 5.6) in the following order: 10mM, 5mM, 1mM, 0.1mM and 0.01mM. The undisturbed soil column is leached for 5.3h each time, leaching is stopped, and the undisturbed soil column is drained for 18.7h under the action of gravity.
(3) Determination of water flux of eluviation solution and concentration of PBDEs
And (3) measuring the water flux: the volume of the collected leaching solution per outlet port per unit time was measured, divided by the port area (2 cm) 2 ) The flux (in cm/h) was obtained.
The extraction method of PBDEs in the leaching solution comprises the following steps: the leach solution was transferred to a 20mL brown bottle and 2. Mu.L of 5. Mu.g/mL BDE-77 was added as an indicator of recovery. Then adding 2mL of normal hexane, oscillating for 30min for liquid-liquid extraction, repeatedly extracting the original leaching solution twice, mixing the three extraction solutions, blowing nitrogen, slowly blowing to below 1mL, using the normal hexane to fix the volume to 1mL, carrying out vortex oscillation for 30s, sucking the extraction solution, filtering the extraction solution by using a 0.22 mu m organic phase nylon filter, transferring the filtration solution to a gas phase sample bottle, adding 2 mu L of 5 mu g/mL BDE-118 serving as an internal standard, and placing the internal standard in a refrigerator at the temperature of-20 ℃ for storage to be detected.
Determination of PBDEs in the extract: the type and concentration of PBDEs in the extract were determined by gas chromatography-mass spectrometry (GC-MS) using a gas chromatography-mass spectrometer model 7890A-5975C (Agilent, USA).
The gas chromatography-mass spectrometer chromatographic column is an Rtx-1614 capillary column (15 m × 0.25mm × 0.10 μm). The carrier gas is helium, the flow rate is 2mL/min, the split-flow sample injection is not carried out, and the sample injection amount is 1 mu L.
The temperature rising procedure is as follows: keeping the temperature at 110 ℃ for 3min, raising the temperature to 200 ℃ at the speed of 25 ℃/min, raising the temperature to 280 ℃ at the speed of 15 ℃/min, then raising the temperature to 305 ℃ at the speed of 20 ℃/min, keeping the temperature for 5min, and finally, 18.183min.
The mass spectrum conditions are as follows: negative Chemical Ion (NCI) source, selected Ion Monitoring (SIM) mode, ion source temperature 250 ℃ and transmission line temperature 280 ℃. The quantitative ion of BDE-209 is fragment ion with mass-to-charge ratio (m/z) of 466, 468, and the quantitative ion of other kinds of PBDEs is bromide ion (m/z of 79, 81).
(4) Results of the experiment
In the process of leaching the undisturbed soil column by using simulated rainwater solutions with different ionic strengths, an obvious preferential flow path is presented (in 7 water outlet ports below the undisturbed soil column, only 4 ports have water to be discharged) (figure 4).
As shown in fig. 4, the water flux of different water outlet ports also changed in the successive experiments: during the first time of leaching by using 10mM simulated rainwater solution, water is discharged through the 4# -and 6# -outlet ports, and the 4# -outlet port is the main outlet port, during the second time of leaching by using 5mM simulated rainwater solution, water is discharged through the 4# -, "6# -," 7# - "outlet port, and the 7# -" outlet port is the main outlet port, during the second time of leaching, the water flux through the 4# -, and "6# -, is reduced, water samples start to be discharged from the adjacent port 7# -, during the third time of leaching by using 1mM simulated rainwater solution, water is discharged through the 3# -," 4# -, "6# -, and the 3# -" outlet port is the main outlet port, during the third time of leaching, the water flux through the 4# -, and "6# -, water samples start to be discharged from the adjacent port 3# -, during the fourth time of leaching by using 0.1mM simulated rainwater solution, during the 4# -," outlet port, and "6# -, and the simulated rainwater solution is discharged through the fifth outlet port, and the main outlet port is the 4# -, and the water sample is the fifth time of the 4# -, and the main outlet port is the 4# -, and the water outlet port is the 5mM simulated rainwater solution. According to the experimental results, when the original-state soil columns are leached by using simulated rainwater solutions with different ionic strengths, the preferential flow paths are different.
In fig. 4, (a) the ionic strength of the simulated stormwater solution is 10mM, (b) the ionic strength of the simulated stormwater solution is 5mM, (c) the ionic strength of the simulated stormwater solution is 1mM, (d) the ionic strength of the simulated stormwater solution is 0.1mM, and (e) the ionic strength of the simulated stormwater solution is 0.01mM. The flow rate was set at 15mm/h, pH =5.6. The vertical dashed line indicates that undisturbed soil column is gravity drained for 18.7h. And analyzing the water sample flowing out of each water outlet port. The black square represents the combination of water samples for extraction treatment, and the characters above the square are sample numbers.
Combining the collected leaching solutions, combining the leaching solutions in adjacent glass test tubes (under one water outlet port, the leaching solutions in two or more glass test tubes adjacent in leaching time are combined), detecting BDE-209 in each combined water sample, detecting BDE-209 with higher concentration (0.05-0.75 ng/mL) in a part of the water samples, not detecting other PBDEs (see table 2), not detecting BDE-209 in other water samples, wherein the BDE-209 concentration in a sample (the ion intensity of the leaching solution is 10 mM) with the number of H1 is the highest.
TABLE 2 BDE-209 release concentration in eluviation experiments with different ionic strengths
Note: the sample numbers are shown in FIG. 4.
In the above experiment, all the BDE-209 that can be measured are from the water sample of the main apopore, which indicates that the heterogeneity of the surface soil of the field is high. The release and the migration of polybrominated diphenyl ethers are influenced by simulating rainwater outflow in the flow path, and the polybrominated diphenyl ethers in the soil are easier to release and vertically migrate from pore paths with large rainwater outflow. Comparing the release rates of BDE-209 at different ionic strengths, the best release capacity of polybrominated diphenyl ethers was found at 10mM ionic strength.
Example 4
Utilize the original state earth pillar eluviation experimental apparatus of embodiment 2 building, carry out original state earth pillar eluviation experiment under the different pH condition, including steps such as experiment post preflushing, eluviation experiment and the analysis of eluviation sample:
(1) Pre-washing experimental column
The procedure was the same as in example 3.
(2) Leaching experiment
A simulated rainwater solution with pH of 4.0 and ionic strength of 1mM is leached into the undisturbed soil column for 5.3h, leaching is stopped, and the original soil column is drained under the action of gravity for 18.7h. During leaching, samples were taken every 20min at 7 water outlets of the column and analyzed immediately. The above experimental operation was repeated, and leaching experiments were sequentially performed with the same undisturbed soil column and 4 simulated rainwater solutions of different pH (both ionic strength 1 mM) in the following order: 4.0, 6.0, 8.0 and 10.0. The undisturbed soil column is leached for 5.3h each time, leaching is stopped subsequently, and the undisturbed soil column is drained for 18.7h under the action of gravity.
(3) Determination of water flux and PBDEs concentration of eluviation solution
The procedure was the same as in example 3.
(4) Results of the experiment
In the process of leaching the undisturbed soil column by the simulated rainwater solution with different pH values, an obvious preferential flow path is presented, and only 2 ports of '1 #' and '5 #' are provided with water to be discharged (figure 5). In successive experiments, the water flux of the 2 outlet holes also changed: during the second leaching, the water flux through port "1# increases, becoming the main water outlet and continues until the end of the experiment.
In fig. 5, (a) a simulated stormwater solution having a pH of 4.0, (b) a simulated stormwater solution having a pH of 6.0, (c) a simulated stormwater solution having a pH of 8.0, and (d) a simulated stormwater solution having a pH of 10.0. The flow rate was set at 15mM/h, ionic strength =1mM. The vertical dashed lines indicate that the column was gravity drained for 18.7h. The black square represents the combination of water samples for extraction treatment, and the characters above the square are the sample numbers.
(3) In the leaching solutions collected from the water outlet ends in leaching experiments with different pH values, combining the collected leaching solutions in adjacent glass test tubes (under one water outlet port, the leaching solutions in two or more glass test tubes adjacent in leaching time are combined), detecting BDE-209 in each combined water sample, detecting BDE-209 with higher concentration (0.06-1.00 ng/mL) in part of the water samples, not detecting other PBDEs (see Table 3), and not detecting BDE-209 in other water samples; wherein, the BDE-209 concentration in the sample h3 obtained under the condition that the pH of the leaching solution is 10 is the highest and reaches 1.00ng/mL.
TABLE 3 BDE-209 release concentration in different pH eluviation experiments
Note: the sample numbers are shown in FIG. 5.
Compared with example 3, in the process of leaching the undisturbed soil column by the simulated rainwater solution with different pH values, all the BDE-209 capable of being measured are also from the water sample of the main water outlet. The influence of the pH of the rainwater on the release and migration of the polybrominated diphenyl ethers is shown, and similarly, paths with large rainwater outflow quantity release and migrate the polybrominated diphenyl ethers more easily. Comparing the release rates of BDE-209 at different pH, it was found that the polybrominated diphenyl ethers were more efficiently released at a pH of 10 in the leacheate.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for analyzing release and migration characteristics of polybrominated diphenyl ethers in a contaminated site, comprising the steps of:
step 1, sampling in situ in a polluted site to obtain an undisturbed soil column to be detected;
preparing a simulated rainwater solution or collecting rainwater in a polluted site;
step 2, filling the undisturbed soil column into a core holder, wherein the top of the core holder is provided with a water inlet, the bottom of the core holder is provided with N water outlet ports, one water outlet port is arranged at the central position and is a central water outlet port, and the rest water outlet ports are symmetrically arranged by taking the central water outlet port as a center;
step 3, pre-washing the undisturbed soil column: pumping the simulated rainwater solution or rainwater collected in a polluted site into the core holder for pre-flushing under the condition of constant pressure and constant current through the water inlet, removing soluble impurities in the undisturbed soil column and balancing the moisture content in the undisturbed soil column, and then stopping leaching, wherein the undisturbed soil column is drained under the action of gravity;
and 4, carrying out a leaching experiment: pumping the simulated rainwater solution or rainwater collected in a polluted site into the core holder for leaching through the water inlet at constant pressure and constant flow, and respectively collecting the leaching solution flowing out of each water outlet port;
and 5, measuring the water flux of each water outlet port, measuring the concentration of PBDEs in the leaching solution flowing out of each water outlet port, and analyzing the release and migration characteristics of the polybrominated diphenyl ethers in the polluted site according to the detection result.
2. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in a polluted site as claimed in claim 1, wherein in the step 1, the undisturbed soil column to be detected is obtained by the following method: removing vegetation on the surface layer of the soil, then collecting an undisturbed soil column at the depth of 0-10 cm on the surface layer by using a pulse sampler, sealing the bottom of the pulse sampler by using a sealing film after the undisturbed soil column is collected, sleeving a protective sleeve on the pulse sampler, and transporting the pulse sampler back to a laboratory for storage in a refrigerator.
3. The method for analyzing release and migration characteristics of polybrominated diphenyl ethers in a contaminated site according to claim 1, wherein in the step 1, when preparing the simulated rainwater solution, two sets of simulated rainwater solutions are prepared, one set being a simulated rainwater solution having the same pH and different ionic strengths, and the other set being a simulated rainwater solution having the same ionic strength and different pH;
preferably, one of the two sets of simulated rainwater solutions has a pH of 5.6 and ionic strengths of 10, 5, 1, 0.1 and 0.01mM, and the other set of simulated rainwater solutions has an ionic strength of 1mM and pH values of 4.0, 6.0, 8.0 and 10.0, respectively.
4. The method for analyzing polybrominated diphenyl ethers release and migration characteristics in a contaminated site according to claim 2, characterized in that in step 2, a undisturbed column is placed in the core holder together with a pulse sampler.
5. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in a polluted site as claimed in claim 1, wherein in the step 3, the pre-washing time is 24-48h, and the drainage time of the undisturbed soil column under the action of gravity is 16-20h.
6. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in the polluted site as claimed in claim 3, wherein in the step 4, the leaching time is 4-8h in each leaching experiment, and the drainage time of an undisturbed soil column under the action of gravity is 16-20h after each leaching experiment;
when analyzing the influence of rainwater with different ionic strengths on the release characteristics of polybrominated diphenyl ethers in a polluted site, sequentially using simulated rainwater solutions with pH of 5.6 and ionic strengths of 10, 5, 1, 0.1 and 0.01mM to carry out a leaching experiment, and collecting the leaching solution flowing out of each water outlet port at intervals of 20-40min during each leaching experiment;
when analyzing the influence of rainwater with different ionic pH values on the release characteristics of polybrominated diphenyl ethers in a polluted site, carrying out leaching experiments in sequence by using simulated rainwater solutions with ionic strength of 1mM and pH values of 4.0, 6.0, 8.0 and 10.0 respectively, and collecting the leaching solution flowing out of each water outlet port at intervals of 20-40min during each leaching experiment.
7. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in a contaminated site according to claim 1, wherein in step 5, the water flux = the volume of the collected leaching solution per outlet port per unit time divided by the port area;
in the step 5, the determination of PBDEs comprises the following steps:
step s1, extracting PBDEs in the leaching solution, transferring the leaching solution into a brown bottle, adding BDE-77 as a recovery rate indicator, then adding n-hexane and oscillating for liquid-liquid extraction for multiple times, mixing the extraction solutions obtained by multiple operations, blowing nitrogen, fixing the volume to 1mL by using the n-hexane, carrying out vortex oscillation, absorbing the extraction solution, filtering the extraction solution by using a 0.22-micron organic phase nylon filter, transferring the extraction solution into a gas phase sample bottle, adding BDE-118 as an internal standard, and storing the internal standard in a refrigerator to serve as a liquid to be detected;
and step s2, using a gas chromatography-mass spectrometer to measure the types and the concentrations of the PBDEs in the solution to be measured.
8. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in contaminated sites according to claim 7, wherein in step s2, the GC-MS column is an Rtx-1614 capillary column (15 m x 0.25mm x 0.10 μm). The carrier gas is helium, the flow rate is 2mL/min, the sample injection is not divided, and the sample injection amount is 1 mu L.
The temperature rising procedure is as follows: keeping the temperature at 110 ℃ for 3min, raising the temperature to 200 ℃ at the speed of 25 ℃/min, raising the temperature to 280 ℃ at the speed of 15 ℃/min, then raising the temperature to 305 ℃ at the speed of 20 ℃/min, keeping the temperature for 5min, and finally, 18.183min.
The mass spectrum conditions are as follows: negative Chemical Ion (NCI) source, selecting Ion Monitoring (SIM) mode, wherein the temperature of the ion source is 250 ℃ and the temperature of the transmission line is 280 ℃. The BDE-209 quantitative ions are fragment ions with mass-to-charge ratios (m/z) of 466 and 468, and the other PBDEs quantitative ions are bromide ions (m/z of 79 and 81).
9. The method for analyzing the release and migration characteristics of polybrominated diphenyl ethers in the polluted site as claimed in claim 1, wherein in the step 5, the water outlet port with the largest water flux is taken as a main water outlet port, the total release rate of the polybrominated diphenyl ethers in the leaching solution of each water outlet port is calculated to predict the release and vertical migration capabilities of the polybrominated diphenyl ethers in the surface soil of the polluted site under specific conditions, and the release heterogeneity of the polybrominated diphenyl ethers is analyzed by comparing the flow rate of the leaching solution of the main water outlet port and other water outlet ports with the content difference of the polybrominated diphenyl ethers.
10. The utility model provides a device of polybrominated diphenyl ether release and migration characteristic in analysis contaminated site which characterized in that, includes double-cylinder constant voltage constant current pump, piston container, rock core holder and catchment funnel and constitutes, wherein: the water inlet of the double-cylinder constant-pressure constant-flow pump is connected with ultrapure water, the water outlet of the double-cylinder constant-pressure constant-flow pump is connected to the inlet of the piston container through a pipeline, a simulated rainwater solution is filled in the piston container, the outlet of the piston container is connected to the water inlet of the core holder through a water supply pipeline, an inlet pressure gauge is arranged on the water supply pipeline, an original-state soil column is filled in the core holder, a screen is arranged below the original-state soil column to prevent soil particles from flowing out, N water outlet ports are arranged at the bottom of the core holder, one water outlet port is arranged at a central position and is a central water outlet port, the other water outlet ports are symmetrically arranged by taking the central water outlet port as a center, a water collecting funnel is connected to each water outlet port, and a leaching solution flowing out of the water outlet ports is collected into a sample receiving pipe at the lower part through the water collecting funnels;
the prepared simulated rainwater solution is stored in the piston container, the simulated rainwater solution is pumped into the original-state soil column by the double-cylinder constant-pressure constant-flow pump at constant pressure and constant flow rate, and the leaching solution flows out through the water outlet port after the original-state soil column is leached.
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| CN113075329A (en) * | 2021-04-02 | 2021-07-06 | 南开大学 | Method for detecting polybrominated diphenyl ethers in contaminated site soil |
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