CN114354786A - Method for analyzing benzene series spatial distribution of underground water in polluted site based on pollution plume - Google Patents
Method for analyzing benzene series spatial distribution of underground water in polluted site based on pollution plume Download PDFInfo
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Abstract
The invention discloses a method for analyzing the spatial distribution of benzene series in underground water in a polluted site based on pollution plumes, which belongs to the technical field of underground water pollution treatment and comprises the following steps: s1, analyzing a polluted site; s2, arranging monitoring wells; s3, collecting underground water samples; s4, determining a monitoring index and a microbial degradation indicating index: selecting benzene series in a plurality of water samples as a representative monitoring index for identifying natural attenuation of organic pollutants in underground water, and using the oxidation-reduction potential representation of the oxidation-reduction state of the underground water as a microbial degradation indication index; s5, analyzing and testing the sample; and S6, data processing. The method takes the benzene series pollutants in the underground water of the pesticide pollution site as a research object, develops practical research on natural attenuation of the benzene series pollutants in the underground water from the concentration, pollution plume range and oxidation-reduction potential change characteristics of the benzene series pollutants through long-term monitoring data, and provides a theoretical basis for application and perfection of the underground water natural attenuation technology and a risk control technical method.
Description
Technical Field
The invention relates to the technical field of groundwater pollution treatment, in particular to a method for analyzing the spatial distribution of benzene series in groundwater in a polluted site based on pollution feathers.
Background
The benzene series comprises benzene, toluene, ethylbenzene and xylene, is an organic compound with the advantages of easy volatilization, high mobility and high toxic effect, is a common organic solvent in industry, and is a pollutant widely existing in pesticide chemical polluted sites. The residual benzene series in agricultural production can rapidly permeate into soil and underground water, has high migration and diffusion speed, can be retained in the underground water for a long time, and causes serious pollution to the soil and the underground water. At present, the common underground water pollution risk control and restoration technology comprises a permeable reactive barrier, natural attenuation monitoring, extraction treatment, multiphase extraction and the like, wherein compared with other restoration technologies, the method for monitoring the natural attenuation has the advantages of low cost, no damage to the surrounding environment of a polluted site and the like.
The technology for monitoring natural attenuation is to implement a planned monitoring strategy, so that the quantity, toxicity and mobility of pollutants in underground water and soil are reduced to acceptable risk levels according to the physical, chemical and biological effects (biodegradation, diffusion, adsorption, dilution, volatilization, radioactive decay, chemical or biological stability and the like) naturally occurring in a field. At present, natural attenuation phenomena exist in most polluted sites, but the intensity of the natural attenuation shows time and space difference along with the nature of pollutants and the environmental conditions in which the pollutants are located. The various natural attenuation effects jointly determine the persistence and complexity of the pollution plume and the stable, reduced or expanded state of the pollution plume.
The research of the monitoring natural attenuation technology in foreign countries starts earlier, and the application proportion of the monitoring natural attenuation technology is improved year by year and is close to 35 percent. The main pollutants suitable for using the technology for monitoring natural attenuation are petroleum, benzene series, organic solvents and the like, and the advantage of low economic cost and small influence on the environment is taken as an important technology for repairing petroleum hydrocarbon polluted sites for monitoring natural attenuation. At present, domestic researches related to natural attenuation of benzene series mainly focus on indoor simulation tests, and researches on attenuation process and mechanism of pollution fields, feasibility evaluation and the like are still in a starting stage.
Disclosure of Invention
Aiming at the problems, the invention provides a method for analyzing the spatial distribution of benzene series in underground water of a polluted site based on a pollution plume.
The technical scheme of the invention is as follows:
the method for analyzing the benzene series spatial distribution of the underground water of the polluted site based on the pollution plume comprises the following steps:
s1, analyzing a polluted site:
s1-1, analyzing main pollutants in the polluted site, dividing main pollution areas of the polluted site, measuring and calculating the pollution time of the polluted site, and analyzing the climate environment of the polluted site;
s1-2, analyzing hydrogeological conditions of the polluted site, acquiring stratum division parameters and soil composition parameters of the polluted site, monitoring groundwater level, and analyzing hydraulic gradient, runoff speed and groundwater flow direction;
s2, monitoring well layout:
according to the hydrogeological analysis result of the polluted site, 15-20 monitoring wells are distributed in an aquifer within 10m of the polluted site based on the target sampling depth and operability of the monitoring wells, the monitoring wells are communicated, the well depth of the monitoring wells is 10m, and the positions of sieve pipes are set to be-1 to-9.5 m;
s3, collecting underground water samples: adopting a low-flow technology to wash a well and sample underground water, arranging a plurality of sampling ports 2-8 m below the ground, and directly collecting a water sample from an outlet of a water conveying pipeline;
s4, determining a monitoring index and a microbial degradation indicating index:
selecting benzene series in a plurality of water samples as a representative monitoring index for identifying natural attenuation of organic pollutants in underground water, and using the oxidation-reduction potential representation of the oxidation-reduction state of the underground water as a microbial degradation indication index;
s5, sample analysis and test:
performing qualitative and quantitative analysis on a sample by adopting a purging and trapping-gas chromatography mass spectrometer, wherein a chromatographic column is a DB-VRX quartz capillary column, a tuning mode is DFTPP tuning, wherein the chromatographic carrier gas condition is high-purity helium, the flow rate is 1-1.5mL/min, split-flow sample injection is performed at a ratio of 15:1, the temperature of a sample inlet is 240 ℃ plus one's worth of sample, the temperature of a column box is 40 ℃, the sample inlet is kept for 2min at 40 ℃, then the temperature is increased to 250 ℃ at a temperature increase rate of 20 ℃/min, the sample is kept for 3min, the mass spectrum condition is 230 ℃ of an ion source, the interface temperature is 250 ℃, the delay time of a solvent is 0.5min, and an ion detection SCAN mode is adopted;
s6, data processing:
the method comprises the steps of performing data processing and drawing a graph by using Excel and Origin software, performing interpolation analysis on the benzene content by using a Krigin spatial interpolation method, drawing the benzene concentration spatial distribution by using EVS-Pro software, performing correlation analysis on the oxidation-reduction potential and the benzene concentration by using a Pearson correlation coefficient method, calculating the pollution plume area of the benzene, and judging the pollution plume characteristics of the benzene in the underground water layer.
Further, the flow rate of the effluent water collected in the step S3 is 40-100mL/min, so that the water sample flows into the underground water sample bottle, the water sample overflows in the sample bottle to form a convex surface, the bottle cap is screwed, the underground water sample bottle is inverted, the observation is carried out for 3-5 seconds, and bubbles in the bottle are removed. The water sample is prevented from being secondarily polluted or influenced by the external environment, and the accuracy of the experimental result is ensured.
Furthermore, in step S3, there are 5 sampling ports, a sampling period of 1 year, and a total of 4 sampling periods. Practical research on natural attenuation of the concentration of benzene series in underground water is carried out through long-term monitoring data of 4 years.
Further, in the step S4, the benzene series 4 are benzene, toluene, ethylbenzene, and xylene, which are all organic compounds with volatile, high mobility, and high toxicity effects.
Further, before the sample analysis in the step S5, an internal standard solution or an alternative standard solution is added to the sampling bottle, and a water sample test is performed by using a purge trap-gas chromatograph mass spectrometer. Ensure the accuracy of the analysis result of the sample.
Further, the step S5 includes performing a blank standard addition experiment and a parallel experiment, where the relative percentage deviation of each compound in the blank standard addition experiment is 0-20%, and the recovery rate is 70-130%; the relative percentage deviation of the parallel experiment samples is 0-30%, the matrix labeling recovery rate of the water sample is 70-130%, and the accuracy and reliability of the experiment result are ensured.
Preferably, the step S6 of judging the characteristics of the pollution plume includes the following steps:
s6-1: judging the relative positions of the pollution source and the pollution plume, wherein the region with the vertical distribution of the benzene series in the descending trend is the position of the pollution source, and the region with the vertical distribution of the benzene series in the ascending trend is the position of the pollution plume;
s6-2: identifying the three-dimensional form of the pollution plume of the benzene series, and identifying the three-dimensional distribution characteristics of the pollution plume of the underground water by using a three-dimensional spatial information analysis tool and integrating different layer data of each monitoring well in the pollution site;
s6-3: after the second period, 2-4 groups of monitoring wells positioned in the upstream direction of the interior of the pollution plume are converted into medicine adding wells, 2-4 groups of medicine adding wells are added in the upstream direction of the pollution plume, and the medicine adding wells in the interior of the pollution plume are converted into the monitoring wells after the medicine adding is finished;
s6-4: and after the third period, converting 3-5 groups of monitoring wells positioned in the middle of the interior of the pollution plume into aeration wells for heating and aeration to promote the volatilization of the benzene series, simultaneously converting the dosing wells in the upstream direction of the pollution plume in the step S6-3 into extraction wells, and converting 2-4 groups of monitoring wells in the downstream direction of the interior of the pollution plume into extraction wells. The groundwater is repaired by the combination of heating aeration and extraction.
Further, the step S6 includes analyzing the oxidation-reduction potential, where the higher the oxidation-reduction potential in the groundwater is, the stronger the oxidation is, the lower the oxidation-reduction potential in the groundwater is, the stronger the reduction is, drawing a curve of the relationship between the oxidation-reduction potential and the benzene series concentration in the groundwater, and observing the correlation presented by the relationship between the oxidation-reduction potential and the benzene series concentration to obtain the interaction principle between the oxidation-reduction potential and the benzene series concentration.
Further, step S6 includes fitting the benzene series concentration with a first-order attenuation equation, and performing linear fitting on the natural logarithm of the benzene series concentration in each monitoring well and time, where the slope of the linear fitting function is the attenuation coefficient of the benzene series concentration of the monitoring well, so as to evaluate the natural attenuation rate and trend of the contaminated site, where the first-order attenuation equation is:
k＝In(C0/Ct)/t
wherein, C0As initial concentration of benzene series, mg.L-1；CtConcentration of the attenuated organic matter in mg. L-1K is the degradation rate constant of the organic substance, d-1The larger the k value is, the faster the material decays, t is the degradation time, d;
and further obtaining an equation of the half-life period of the benzene series concentration and the degradation rate constant of each monitoring well as the following steps:
t1/2＝0.693/k
wherein, t1/2Half-life of benzene series concentration. The natural decay rate constant reflects the decay rate constant of the contaminant within a certain sampling analysis period and is based on the evaluation result within a certain specific time range.
The invention has the beneficial effects that:
(1) the method takes the benzene series pollutants in the underground water of the pesticide pollution site as a research object, develops practice research on natural attenuation of the benzene series pollutants in the underground water from the aspects of benzene series pollutant concentration, pollution plume range, oxidation-reduction potential change characteristics and the like through long-term monitoring data, and provides theoretical basis for application and improvement of a natural attenuation technology of the underground water of the pesticide pollution site and a risk control technical method.
(2) The method provided by the invention has the advantages that the detection precision of the groundwater water sample is improved by the combination of the purging and trapping-gas chromatography mass spectrometer, the redox potential and the benzene series concentration relation curve in the groundwater is drawn by analyzing the redox potential, the correlation presented by the redox potential and the benzene series concentration relation is observed, and the interaction principle of the two is obtained.
(3) The method of the invention fits the benzene series concentration with a first-order attenuation equation, and carries out linear fitting on the natural logarithm and the time of the benzene series concentration in each monitoring well, wherein the slope of a linear fitting function is the attenuation coefficient of the benzene series concentration of the monitoring well, so as to evaluate the natural attenuation rate and the trend of the polluted site, and obtain an equation of the half-life period of the benzene series concentration of each monitoring well and the degradation rate constant, and the natural attenuation rate constant can reflect the attenuation rate constant of pollutants in a certain sampling analysis period and is based on the evaluation result in a certain specific time range.
(4) The method provided by the invention is used for carrying out auxiliary restoration on the groundwater sample by combining the sampling period, and restoring the groundwater by combining heating aeration and extraction according to the rule reflected by monitoring natural attenuation.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention;
FIG. 2 is a view of a monitoring well layout in Experimental example 1 of the method of the present invention;
FIG. 3 is a distribution diagram of benzene pollution plume in 9 months in 2017 in Experimental example 1 of the method of the present invention;
FIG. 4 is a toluene pollution plume profile in 9 months in 2017 in Experimental example 1 of the method of the present invention;
FIG. 5 is a graph of the distribution of ethylbenzene contamination plume in 9 months in 2017 in Experimental example 1 of the process of the present invention;
FIG. 6 is a xylene pollution plume profile in 9 months 2017 in Experimental example 1 of the method of the present invention;
FIG. 7 is a distribution diagram of benzene pollution plume in Experimental example 1 of the method of the present invention at 6 months 2020;
FIG. 8 is a toluene pollution profile in month 2020 and 6 in Experimental example 1 of the method of the present invention;
FIG. 9 is a distribution diagram of ethylbenzene contamination plume in Experimental example 1 of the process of the present invention at month 2020 and 6;
FIG. 10 is a xylene contamination plume distribution in Experimental example 1 of the process of the present invention at 6 months 2020;
FIG. 11 shows the distribution of the redox potential in the monitoring wells in Experimental example 1 of the method of the present invention;
FIG. 12 is a schematic view of a monitoring well-to-dosing well in Experimental example 2 of the method of the present invention;
FIG. 13 is a schematic view of a monitoring well-to-aeration well and an extraction well in Experimental example 2 of the method of the present invention.
Detailed Description
Example 1
The method for analyzing the benzene series spatial distribution of the underground water of the polluted site based on the pollution plume comprises the following steps:
s1, analyzing a polluted site:
s1-1, analyzing main pollutants in the polluted site, dividing main pollution areas of the polluted site, measuring and calculating the pollution time of the polluted site, and analyzing the climate environment of the polluted site;
s1-2, analyzing hydrogeological conditions of the polluted site, acquiring stratum division parameters and soil composition parameters of the polluted site, monitoring groundwater level, and analyzing hydraulic gradient, runoff speed and groundwater flow direction;
s2, monitoring well layout:
according to the hydrogeological analysis result of the polluted site, 16 monitoring wells are distributed in an aquifer within 10m of the polluted site based on the target sampling depth and operability of the monitoring wells, the monitoring wells are communicated, the well depth of the monitoring wells is 10m, and the positions of sieve pipes are set to be-1 to-9.5 m;
s3, collecting underground water samples:
adopting a low-flow technology to wash a well and sample underground water, arranging a plurality of sampling ports 2-8 m below the ground, directly collecting a water sample from an outlet of a water conveying pipeline, wherein the flow rate of the collected water sample is 70mL/min, so that the water sample flows into an underground water sample bottle, the water sample overflows in the sample bottle to form a convex surface, screwing a bottle cap, reversing the underground water sample bottle, observing for 4 seconds, removing bubbles in the bottle, wherein the number of the sampling ports is 5, the sampling period is 1 year, and 4 sampling periods are arranged in total;
s4, determining a monitoring index and a microbial degradation indicating index:
selecting benzene series in a plurality of water samples as a representative monitoring index for identifying natural attenuation of organic pollutants in underground water, representing the oxidation-reduction state of the underground water by oxidation-reduction potential as an indication index of microbial degradation, wherein the benzene series is 4, namely benzene, toluene, ethylbenzene and xylene;
s5, sample analysis and test:
before sample analysis, an internal standard solution or a substitute standard solution is added into a sampling bottle, and a purging and trapping gas chromatography mass spectrometer Atomx-Agilent 7890B/5977A is adopted for water sample test;
performing qualitative and quantitative analysis on a sample by adopting a purging and trapping-gas chromatography mass spectrometer, wherein the chromatographic column is a DB-VRX quartz capillary column, the tuning mode is DFTPP tuning, the chromatographic carrier gas condition is high-purity helium, the flow rate is 1.2mL/min, split-flow sample injection is performed at a ratio of 15:1, the temperature of a sample inlet is 230 ℃, the temperature of a column box is 40 ℃, the sample inlet is kept for 2min at the condition of 40 ℃, then the temperature is increased to 250 ℃ at the temperature increasing rate of 20 ℃/min and is kept for 3min, the mass spectrum condition is that the ion source temperature is 230 ℃, the interface temperature is 250 ℃, the solvent delay time is 0.5min, and the ion detection SCAN mode is adopted;
carrying out blank standard adding experiments and parallel experiments, wherein the relative percentage deviation of each compound in the blank standard adding experiments is lower than 20%, and the recovery rate is 100%; the relative percentage deviation of the parallel experimental samples is 0-30%, and the matrix standard adding recovery rate of the water sample is 100%;
s6, data processing:
performing data processing and drawing a graph by using Excel and Origin software, performing interpolation analysis on the benzene content by using a Krigin spatial interpolation method, drawing the benzene concentration spatial distribution by using EVS-Pro software, performing correlation analysis on the oxidation-reduction potential and the benzene concentration by using a Pearson correlation coefficient method, calculating the pollution plume area of the benzene, and judging the pollution plume characteristics of the benzene in the underground water layer;
analyzing the oxidation-reduction potential, drawing a relation curve of the oxidation-reduction potential and the benzene series concentration in the underground water, and observing the correlation presented by the relation of the oxidation-reduction potential and the benzene series concentration;
fitting the benzene series concentration with a first-order attenuation equation, performing linear fitting on the natural logarithm of the benzene series concentration in each monitoring well and time, wherein the slope of a linear fitting function is the attenuation coefficient of the benzene series concentration of the monitoring well, so as to evaluate the natural attenuation rate and trend of the polluted site, and the first-order attenuation equation is as follows:
k＝In(C0/Ct)/t
wherein, C0As initial concentration of benzene series, mg.L-1；CtConcentration of the attenuated organic matter in mg. L-1K is the degradation rate constant of the organic substance, d-1The larger the k value is, the faster the material decays, t is the degradation time, d;
and further obtaining an equation of the half-life period of the benzene series concentration and the degradation rate constant of each monitoring well as the following steps:
t1/2＝0.693/k
wherein, t1/2Half-life of benzene series concentration.
Example 2
The present embodiment is different from embodiment 1 in that: the number of monitor well placements is different in step S2.
S2, monitoring well layout: and (2) according to the hydrogeological analysis result of the polluted site, arranging 15 monitoring wells in the aquifer within the range of 10m of the polluted site based on the target sampling depth and operability of the monitoring wells, wherein the monitoring wells are communicated, the well depth of the monitoring wells is 10m, and the positions of the sieve tubes are set to be-1 to-9.5 m.
Example 3
The present embodiment is different from embodiment 1 in that: the number of monitor well placements is different in step S2.
S2, monitoring well layout: and (3) distributing 20 monitoring wells in an aquifer within 10m of the polluted site based on the target sampling depth and operability of the monitoring wells according to the hydrogeological analysis result of the polluted site, wherein the monitoring wells are open wells, the well depth of the monitoring wells is 10m, and the positions of the sieve pipes are set to be-1 to-9.5 m.
Example 4
The present embodiment is different from embodiment 1 in that: the parameters for groundwater sample collection in step S3 are different.
S3, collecting underground water samples: adopt low flow technique to wash the well and groundwater sample, the sample connection sets up a plurality ofly 2-8 meters below ground, directly gather the water sample from the export of waterline, the play water velocity of flow of gathering the water sample is 100mL/min, make the water sample flow in groundwater sample bottle, the water sample overflows in the sample bottle excessively, forms the convex surface, screw up the bottle lid, reverse groundwater sample bottle, observe 5 seconds, get rid of the interior bubble of bottle, the sample connection is 5, the sampling cycle is 1 year, 4 sampling cycles are equipped with altogether.
Example 5
The present embodiment is different from embodiment 1 in that: the parameters for groundwater sample collection in step S3 are different.
S3, collecting underground water samples: adopt low flow technique to wash the well and groundwater sample, the sample connection sets up a plurality ofly 2-8 meters below ground, directly gather the water sample from the export of waterline, the play water velocity of flow of gathering the water sample is 40mL/min, make the water sample flow in groundwater sample bottle, the water sample overflows in the sample bottle in excess, form the convex surface, screw up the bottle lid, reverse groundwater sample bottle, observe 3 seconds, get rid of the interior bubble of bottle, the sample connection is 5, the sampling cycle is 1 year, 4 sampling cycles are equipped with altogether.
Example 6
The present embodiment is different from embodiment 1 in that: the parameters of the water sample test in step S5 are different.
And performing qualitative and quantitative analysis on the sample by adopting a purging and trapping-gas chromatography mass spectrometer, wherein the chromatographic column is a DB-VRX quartz capillary column, the tuning mode is DFTPP tuning, the chromatographic carrier gas condition is high-purity helium, the flow rate is 1mL/min, split-flow sample injection is performed at a ratio of 15:1, the temperature of a sample inlet is 200 ℃, the temperature of a column box is 40 ℃, the sample inlet is kept for 2min at the temperature of 40 ℃, then the temperature is increased to 250 ℃ at the temperature increasing rate of 20 ℃/min and kept for 3min, the mass spectrum condition is that the ion source temperature is 230 ℃, the interface temperature is 250 ℃, the solvent delay time is 0.5min, and the ion detection SCAN mode is adopted.
Example 7
The present embodiment is different from embodiment 1 in that: the parameters of the water sample test in step S5 are different.
And performing qualitative and quantitative analysis on the sample by adopting a purging and trapping-gas chromatography mass spectrometer, wherein the chromatographic column is a DB-VRX quartz capillary column, the tuning mode is DFTPP tuning, the chromatographic carrier gas condition is high-purity helium, the flow rate is 1.5mL/min, split-flow sample injection is performed at a ratio of 15:1, the temperature of a sample inlet is 240 ℃, the temperature of a column box is 40 ℃, the sample inlet is kept for 2min at the condition of 40 ℃, then the temperature is increased to 250 ℃ at the temperature increasing rate of 20 ℃/min and is kept for 3min, the mass spectrum condition is that the ion source temperature is 230 ℃, the interface temperature is 250 ℃, the solvent delay time is 0.5min, and the ion detection SCAN mode is adopted.
Example 8
The present embodiment is different from embodiment 1 in that: the parameters of the blank labeling experiment and the parallel experiment in step S5 are different.
Carrying out blank standard adding experiments and parallel experiments, wherein the relative percentage deviation of each compound in the blank standard adding experiments is lower than 20%, and the recovery rate is 70%; the relative percentage deviation of the parallel experiment samples is 0-30%, and the matrix standard adding recovery rate of the water sample is 70%.
Example 9
The present embodiment is different from embodiment 1 in that: the parameters of the blank labeling experiment and the parallel experiment in step S5 are different.
Carrying out blank standard adding experiments and parallel experiments, wherein the relative percentage deviation of each compound in the blank standard adding experiments is lower than 20%, and the recovery rate is 130%; the relative percentage deviation of the parallel experiment samples is 0-30%, and the matrix standard adding recovery rate of the water sample is 130%.
Example 9
The present embodiment is different from embodiment 1 in that: step S6 further includes determining the characteristics of the pollution plume, including the following steps:
s6-1: judging the relative positions of the pollution source and the pollution plume, wherein the region with the vertical distribution of the benzene series in the descending trend is the position of the pollution source, and the region with the vertical distribution of the benzene series in the ascending trend is the position of the pollution plume;
s6-2: identifying the three-dimensional form of the pollution plume of the benzene series, and identifying the three-dimensional distribution characteristics of the pollution plume of the underground water by using a three-dimensional spatial information analysis tool and integrating different layer data of each monitoring well in the pollution site;
s6-3: after the second period, converting 3 groups of monitoring wells positioned in the upstream direction of the interior of the pollution plume into medicine adding wells, simultaneously adding 3 groups of medicine adding wells in the upstream direction of the pollution plume, and converting the medicine adding wells in the interior of the pollution plume into the monitoring wells after the medicine adding is finished;
s6-4: and after the third period, 4 groups of monitoring wells positioned in the middle of the interior of the pollution plume are converted into aeration wells for heating and aeration to promote the volatilization of the benzene series, meanwhile, the dosing wells in the upstream direction of the pollution plume in the step S6-3 are converted into extraction wells, and 3 groups of monitoring wells in the downstream direction inside the pollution plume are converted into extraction wells.
Example 10
This embodiment is different from embodiment 9 in that:
s6-1: judging the relative positions of the pollution source and the pollution plume, wherein the region with the vertical distribution of the benzene series in the descending trend is the position of the pollution source, and the region with the vertical distribution of the benzene series in the ascending trend is the position of the pollution plume;
s6-2: identifying the three-dimensional form of the pollution plume of the benzene series, and identifying the three-dimensional distribution characteristics of the pollution plume of the underground water by using a three-dimensional spatial information analysis tool and integrating different layer data of each monitoring well in the pollution site;
s6-3: after the second period, 2 groups of monitoring wells positioned in the upstream direction of the interior of the pollution plume are converted into medicine adding wells, 2 groups of medicine adding wells are added in the upstream direction of the pollution plume, and the medicine adding wells in the interior of the pollution plume are converted into the monitoring wells after medicine adding is finished;
s6-4: and after the third period, converting 3 groups of monitoring wells positioned in the middle of the pollution plume into aeration wells for heating and aeration to promote the volatilization of the benzene series, simultaneously converting the dosing wells in the upstream direction of the pollution plume in the step S6-3 into extraction wells, and converting 2 groups of monitoring wells in the downstream direction inside the pollution plume into extraction wells.
Example 11
This embodiment is different from embodiment 9 in that:
s6-1: judging the relative positions of the pollution source and the pollution plume, wherein the region with the vertical distribution of the benzene series in the descending trend is the position of the pollution source, and the region with the vertical distribution of the benzene series in the ascending trend is the position of the pollution plume;
s6-2: identifying the three-dimensional form of the pollution plume of the benzene series, and identifying the three-dimensional distribution characteristics of the pollution plume of the underground water by using a three-dimensional spatial information analysis tool and integrating different layer data of each monitoring well in the pollution site;
s6-3: after the second period, 4 groups of monitoring wells positioned in the upstream direction of the interior of the pollution plume are converted into medicine adding wells, 4 groups of medicine adding wells are added in the upstream direction of the pollution plume, and the medicine adding wells in the interior of the pollution plume are converted into the monitoring wells after medicine adding is finished;
s6-4: and after the third period, 5 groups of monitoring wells positioned in the middle of the interior of the pollution plume are converted into aeration wells for heating and aeration to promote the volatilization of the benzene series, meanwhile, the dosing wells in the upstream direction of the pollution plume in the step S6-3 are converted into extraction wells, and 4 groups of monitoring wells in the downstream direction inside the pollution plume are converted into extraction wells.
Experimental example 1
The concentration of benzene series in a pesticide pollution site in Jiangsu province is monitored by natural attenuation under the parameter conditions of example 1, the pesticide pollution site is located at the entrance of the Yangtze river and belongs to the Yangtze river downstream alluvial plains, the overall terrain of the area is low, water nets are densely distributed, the pollution site belongs to the northern subtropical humid climate area, the annual average precipitation is 1000-1400 mm, the production history is more than 40 years, main products comprise pesticides, chlor-alkali, fine chemical engineering, high polymer materials and the like, and the site soil and underground water are seriously polluted by long-term production activities. The main pollutant of the soil is benzene series, and the monitoring natural decay remediation for 4 years is started for underground water from 2016.
The stratum revealed by drilling in the polluted site is mainly divided into 5 layers, the 1 st layer is miscellaneous filling soil which mainly comprises silt and silty clay soil, and the thickness is about 1.2 m; the 2 nd layer is silt with the thickness of about 4.0 m; the 3 rd layer is silt with the thickness of about 20.0m and the vertical permeability coefficient of 2.88 multiplied by 10-3cm/s; the 4 th layer is silt clay with the thickness of about 10.0m and the vertical permeability coefficient of 2.90 multiplied by 10-4cm/s; the 5 th layer is a silt stratum with the thickness more than 15.0m and the vertical permeability coefficient of 5.33 multiplied by 10-3cm/s. The groundwater is shallow pore water, and the main sources of supply are atmospheric precipitation, surface water and waterThe same aquifer supplies laterally, and the underground water drainage mode mainly adopts atmospheric evaporation and lateral runoff. Shallow groundwater is of the free diving type and is mainly affected by atmospheric precipitation and surface runoff. The initial water level is 1.60m below the ground, the stable burial depth is about 1.50m, the highest water level is about 0.5m, and the lowest water level is about 2.50 m. The underground water level changes little, the hydraulic gradient is extremely small, and the groundwater runoff is slow. The flow direction of the underground water in the field is northwest-southeast.
According to the hydrogeology result of the polluted site, the diving aquifer is mainly present in the silt layer, the target polluted aquifer is the diving aquifer, and the underground water is homogeneous, so that the concentration of the pollutants in the underground water of the aquifer is considered to be uniform. Considering both the target sampling depth of the underground water monitoring well and the easy operability of the well building depth, 16 long-term monitoring wells are arranged in the aquifer within 10m of the polluted site, the monitoring wells are communicated, the well depth is set to be 10m, the positions of the sieve tubes are set to be-1 m to-9.5 m, and the monitoring well arrangement diagram is shown in figure 2.
According to the monitoring data of the benzene series concentration in each monitoring well from 2016 (9 months) to 2020 (6 months), the benzene concentration range is 0.00025-16.10 mg.L in the whole monitoring period-1Average concentration of 1.13 mg. L-1(ii) a The concentration range of toluene is 0.00025-164.00 mg.L-1The average concentration was 6.88 mg.L-1(ii) a The ethylbenzene concentration is in the range of 0.00025-43.40 mg.L-1Average concentration of 2.76 mg.L-1(ii) a The concentration range of the dimethylbenzene is 0.00025-47.40 mg.L-1Average concentration of 2.01 mg.L-1(ii) a The concentration range of the benzene series is 0.001-180.52 mg.L-1The average concentration was 13.30 mg.L-1. Toluene is the highest concentration contaminant, and the concentration of toluene in most monitoring wells even exceeds the sum of the concentrations of the other 3 benzene series.
The spatial distribution characteristics of the four benzene series pollution plumes of the polluted site in 2017 and 9 months are shown in FIGS. 3-6. The spatial distribution characteristics of the four benzene series are inconsistent: the high-value areas of benzene are near MW2-5 and MW2-9, and the pollution plumes are distributed in the northwest-southeast direction and are approximately consistent with the underground water flow direction of the polluted site; the high value region of toluene occurs in the MW1-3 and MW2-2 regions, ethylbenzeneAnd the higher concentration region of the xylene is near MW1-3, the concentrations of the toluene, the ethylbenzene and the xylene are lower in the southeast direction, and the pollution plumes of the 3 pollutants are approximately distributed in the northeast-southwest direction. In general, the concentration of the benzene series in the middle of the pollution plume of the benzene series is higher than that in the marginal area, the concentration of the benzene series flowing to the downstream of the groundwater is lower than that flowing to the upstream, and the fact that dilution and diffusion of the pollutants possibly occur along with the flowing of the groundwater is inferred. And (3) carrying out interpolation analysis on the content of the benzene series in the polluted site by utilizing a Kriging space interpolation method of EVS-Pro (Version 9.93) software, and calculating the pollution plume area of the benzene series. In 9 months in 2017, the pollution plume areas of benzene, toluene, ethylbenzene and xylene are 3006.78m respectively2、785.26m2、1333.84m2、202.37m2。
The space distribution of benzene series pollution plume in month 6 of 2020 is shown in FIGS. 7-10, and it can be seen that the space distribution of four benzene series pollution plumes in month 6 of 2020 is substantially similar to that in month 9 of 2017, and the pollution plume areas of benzene, toluene, ethylbenzene and xylene in month 6 of 2020 are respectively reduced to 215.34m2、432.21m2、64.20m2、43.47m2. Although the pollution plume areas of the four benzene series show fluctuation changes in 2018 and 2019 due to the rebound of the pollutant concentration, the pollution plume areas of the four benzene series also show a reduced change trend as a whole. In 6 months in 2020, the reduction ratios of benzene, toluene, ethylbenzene and xylene are respectively 92.83%, 44.96%, 95.19% and 78.52% compared with the reduction ratios of the pollution plume in 9 months in 2017, the change of the pollution plume is also a primary evidence for verifying the effectiveness of the natural attenuation effect, and the gradual reduction of the pollution plume of the pollutants in the pollution site further proves that the natural attenuation of the benzene series in the groundwater occurs.
The natural attenuation process includes physical, chemical and biological degradation, wherein the biological degradation involved by microorganisms is the most dominant mechanism of natural attenuation. The microbial degradation process of benzene series generally comprises the steps of respectively carrying out oxidation-reduction reactions such as aerobic action, denitrification action, manganese reduction action, iron reduction action, sulfate reduction action and the like on microorganisms by utilizing an electron donor (benzene series) and an electron acceptor to dissolve oxygen, nitrate, tetravalent manganese, trivalent iron, sulfate and the like. The oxidation-reduction potential (ORP) is an index that macroscopically reflects redox and can be used to indicate the degree of consumption of an electron acceptor and thus the microbial degradation reaction, and in general, the higher the ORP in groundwater, the stronger the oxidation, and the lower the ORP in groundwater, the stronger the reduction. By researching the distribution rule of the oxidation-reduction potential in the underground water, whether the organic matters in the underground water are degraded or not can be preliminarily judged, and the intermediate evidence of natural attenuation of the benzene series in the polluted site is indirectly obtained.
As shown in FIG. 11, the ORP value of each monitoring well in the polluted site from 9 months in 2017 to 6 months in 2020 is-361 mV to 240.2mV, and the average value is-56.71 mV. Under the normal condition, the ORP value range in the underground water is-400-800 mV, and the low oxidation-reduction potential is favorable for the occurrence of microbial degradation, so that the ORP value in the underground water of the polluted site is lower, and the microbial degradation of benzene series is favorable.
The linear relation between the ORP and the benzene series concentration in the groundwater shows that the two are in extremely obvious negative correlation (p is less than 0.01), which indicates that the ORP is lower in a benzene series high-concentration area, and the ORP is higher in a benzene series low-concentration area, probably because the benzene series high-concentration area in a polluted site is degraded, and the microorganisms need to continuously consume electron acceptors in the groundwater through oxidation-reduction action, so that the ORP in the groundwater is lower; on the other hand, the ORP in the groundwater is low, and the groundwater is in a partial reducing environment and continuously promotes the benzene series to generate reduction reaction.
Experimental example 2
Then, natural attenuation monitoring is carried out on the benzene series concentration of a pesticide pollution site in Jiangsu province under the parameter condition of example 9, the experimental example is similar to the hydrogeological condition of the pollution site in the experimental example 1, wherein 3 groups of monitoring wells W1-1, W1-2 and W1-5 positioned in the upstream direction of the interior of the pollution plume in the step S6-3 are converted into dosing wells, and 3 groups of dosing wells W3-1, W3-2 and W3-3 are added in the upstream direction of the pollution plume; in the step S6-4, 4 groups of monitoring wells located in the middle of the interior of the pollution plume are converted into aeration wells W2-1, W2-2, W2-4 and W2-5 to be heated and aerated to promote the volatilization of the benzene series, meanwhile, in the step S6-3, the dosing wells W1-1, W1-2 and W1-5 in the upstream direction of the pollution plume are converted into extraction wells, and 3 groups of monitoring wells W1-4, W1-7 and W1-8 in the downstream direction of the interior of the pollution plume are converted into extraction wells, and the area of the pollution plume of the benzene series is calculated and analyzed by the same experimental method in the experimental example 1, and the reduction ratios of benzene, toluene, ethylbenzene and xylene to the pollution plume in 9 months in 2017 are 93.74%, 48.54%, 94.17% and 80.27% respectively.
Compared with the pollution plume analysis data in the experimental example 1, after the groundwater is repaired by the combination of heating aeration and extraction in the experimental example 2, the pollution plume reduction ratios of benzene, toluene and xylene are improved to a certain extent, wherein the pollution plume reduction ratio of toluene is improved most obviously, and the pollution plume reduction ratio of ethylbenzene is reduced to a certain extent, which indicates that the groundwater is repaired by the combination of heating aeration and extraction, so that the removal effect of most benzene pollutants in the groundwater is improved, the speed of the removal is higher than that of pure natural attenuation, and the promotion effect on ethylbenzene cannot be well achieved, so that other methods are considered in groundwater environmental management aiming at ethylbenzene as a main pollutant.
Claims (9)
1. The method for analyzing the benzene series spatial distribution of the underground water of the polluted site based on the pollution plume is characterized by comprising the following steps of:
s1, analyzing a polluted site:
s1-1, analyzing main pollutants in the polluted site, dividing main pollution areas of the polluted site, measuring and calculating the pollution time of the polluted site, and analyzing the climate environment of the polluted site;
s1-2, analyzing hydrogeological conditions of the polluted site, acquiring stratum division parameters and soil composition parameters of the polluted site, monitoring groundwater level, and analyzing hydraulic gradient, runoff speed and groundwater flow direction;
s2, monitoring well layout:
according to the hydrogeological analysis result of the polluted site, 15-20 monitoring wells are distributed in an aquifer within 10m of the polluted site based on the target sampling depth and operability of the monitoring wells, the monitoring wells are communicated, the well depth of the monitoring wells is 10m, and the positions of sieve pipes are set to be-1 to-9.5 m;
s3, collecting underground water samples: adopting a low-flow technology to wash a well and sample underground water, arranging a plurality of sampling ports 2-8 m below the ground, and directly collecting a water sample from an outlet of a water conveying pipeline;
s4, determining a monitoring index and a microbial degradation indicating index:
selecting benzene series in a plurality of water samples as a representative monitoring index for identifying natural attenuation of organic pollutants in underground water, and using the oxidation-reduction potential representation of the oxidation-reduction state of the underground water as a microbial degradation indication index;
s5, sample analysis and test:
performing qualitative and quantitative analysis on a sample by adopting a purging and trapping-gas chromatography mass spectrometer, wherein a chromatographic column is a DB-VRX quartz capillary column, a tuning mode is DFTPP tuning, wherein the chromatographic carrier gas condition is high-purity helium, the flow rate is 1-1.5mL/min, split-flow sample injection is performed at a ratio of 15:1, the temperature of a sample inlet is 240 ℃ plus one's worth of sample, the temperature of a column box is 40 ℃, the sample inlet is kept for 2min at 40 ℃, then the temperature is increased to 250 ℃ at a temperature increase rate of 20 ℃/min, the sample is kept for 3min, the mass spectrum condition is 230 ℃ of an ion source, the interface temperature is 250 ℃, the delay time of a solvent is 0.5min, and an ion detection SCAN mode is adopted;
s6, data processing:
the method comprises the steps of performing data processing and drawing a graph by using Excel and Origin software, performing interpolation analysis on the benzene content by using a Krigin spatial interpolation method, drawing the benzene concentration spatial distribution by using EVS-Pro software, performing correlation analysis on the oxidation-reduction potential and the benzene concentration by using a Pearson correlation coefficient method, calculating the pollution plume area of the benzene, and judging the pollution plume characteristics of the benzene in the underground water layer.
2. The method for analyzing the spatial distribution of the benzene series in the groundwater in the polluted site based on the pollution plume as claimed in claim 1, wherein the effluent flow rate of the collected water sample in the step S3 is 40-100mL/min, so that the water sample flows into the groundwater sample bottle, the water sample overflows from the sample bottle excessively to form a convex surface, the bottle cap is tightened, the groundwater sample bottle is inverted, and the observation is carried out for 3-5 seconds, so as to remove air bubbles in the bottle.
3. The method for analyzing the spatial distribution of benzene series in groundwater in a polluted site based on pollution plume according to claim 1, wherein in the step S3, the number of sampling ports is 5, the sampling period is 1 year, and 4 sampling periods are provided.
4. The method for analyzing the spatial distribution of benzene series in groundwater in a polluted site based on pollution plume according to claim 1, wherein the benzene series in step S4 is 4, which are benzene, toluene, ethylbenzene, and xylene, respectively.
5. The method for analyzing the benzene series spatial distribution of groundwater in a polluted site based on the pollution plume as claimed in claim 1, wherein before the sample analysis in the step S5, an internal standard solution or a substitute standard solution is added into a sampling bottle, and a water sample test is performed by using a purging and trapping gas chromatography mass spectrometer.
6. The method for analyzing the spatial distribution of benzene series in groundwater in a contaminated site based on pollution plume according to claim 1, wherein the step S5 further comprises performing a blank standard addition experiment and a parallel experiment, wherein the relative percentage deviation of each compound in the blank standard addition experiment is 0-20%, and the recovery rate is 70-130%; the relative percentage deviation of the parallel experiment samples is 0-30%, and the matrix standard adding recovery rate of the water sample is 70-130%.
7. The method for analyzing the spatial distribution of benzene series in groundwater in a polluted site based on pollution plume according to claim 3, wherein the step S6 of judging the characteristics of the pollution plume includes the following steps:
s6-1: judging the relative positions of the pollution source and the pollution plume, wherein the region with the vertical distribution of the benzene series in the descending trend is the position of the pollution source, and the region with the vertical distribution of the benzene series in the ascending trend is the position of the pollution plume;
s6-2: identifying the three-dimensional form of the pollution plume of the benzene series, and identifying the three-dimensional distribution characteristics of the pollution plume of the underground water by using a three-dimensional spatial information analysis tool and integrating different layer data of each monitoring well in the pollution site;
s6-3: after the second period, 2-4 groups of monitoring wells positioned in the upstream direction of the interior of the pollution plume are converted into medicine adding wells, 2-4 groups of medicine adding wells are added in the upstream direction of the pollution plume, and the medicine adding wells in the interior of the pollution plume are converted into the monitoring wells after the medicine adding is finished;
s6-4: and after the third period, converting 3-5 groups of monitoring wells positioned in the middle of the interior of the pollution plume into aeration wells for heating and aeration to promote the volatilization of the benzene series, simultaneously converting the dosing wells in the upstream direction of the pollution plume in the step S6-3 into extraction wells, and converting 2-4 groups of monitoring wells in the downstream direction of the interior of the pollution plume into extraction wells.
8. The method for analyzing the benzene series spatial distribution of groundwater in a polluted site based on the pollution plume as claimed in claim 1, wherein the step S6 further comprises analyzing the oxidation-reduction potential, plotting the oxidation-reduction potential versus the benzene series concentration in the groundwater, and observing the correlation presented by the relationship between the oxidation-reduction potential and the benzene series concentration.
9. The method for analyzing the spatial distribution of benzene series in groundwater of a polluted site based on pollution plume according to claim 1, wherein the step S6 further comprises fitting the benzene series concentration to a first-order attenuation equation, and performing linear fitting on the natural logarithm of the benzene series concentration in each monitoring well and time, wherein the slope of the linear fitting function is the attenuation coefficient of the benzene series concentration in the monitoring well, so as to evaluate the natural attenuation rate and trend of the polluted site, and the first-order attenuation equation is:
k＝In(C0/Ct)/t
wherein, C0As initial concentration of benzene series, mg.L-1；CtConcentration of the attenuated organic matter in mg. L-1K is the degradation rate constant of the organic substance, d-1The larger the k value is, the faster the material decays, t is the degradation time, d;
and further obtaining an equation of the half-life period of the benzene series concentration and the degradation rate constant of each monitoring well as the following steps:
t1/2＝0.693/k
wherein, t1/2Half-life of benzene series concentration.
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| CN115343403A (en) * | 2022-08-16 | 2022-11-15 | 生态环境部南京环境科学研究所 | Detection device for benzene series in underground water of typical pesticide pollution site |
| CN115660413A (en) * | 2022-10-17 | 2023-01-31 | 生态环境部南京环境科学研究所 | Risk management and control system for polluted site underground water |
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