Polluted site remediation method and degradation age limit evaluation method

Abstract

The invention discloses a polluted site remediation method and a degradation age limit evaluation method, and the method comprises the following steps: 1, determining a pollution range, setting a sampling point in a polluted site, taking an underground water sample at the sampling point, and measuring the electron acceptor concentration and the degradation product concentration; 2, calculating the cumulative percentage of different indexes in each period according to the measured concentration of each index in different periods, and drawing a cumulative probability distribution curve of each monitoring index by taking the concentration of an electron acceptor or the concentration of a degradation product as a horizontal coordinate and the corresponding cumulative probability as a vertical coordinate; step 3, threshold range acquisition: acquiring threshold ranges of stable segments of different electron acceptors or degradation products according to the cumulative probability distribution curves of different electron acceptors or degradation products obtained in the step 2; step 4, calculating the degradation capability; and 4, calculating the biodegradation rate of the aquifer. According to the method, the pollutant degradation capability and degradation rate can be quantitatively evaluated by utilizing the conversion relationship between the electron acceptor and the pollutant.

Description

[0001] This invention application is a divisional application of the parent application "A method for assessing the biodegradation rate of aquifers in contaminated sites". The filing date of the parent application is January 30, 2021, and the application number is 2021101318632. Technical Field

[0002] The present invention relates to the technical field of groundwater remediation, and in particular to a contaminated site remediation method and a degradation period assessment method. Background Art

[0003] There are many types of groundwater remediation technologies at present, among which monitoring natural attenuation technology is a low-cost, environmentally friendly in-situ remediation technology. This technology is becoming more mature and has broad application prospects. Biodegradation is the core of natural attenuation remediation technology. Assessing the natural biodegradability of groundwater at a site is the prerequisite for judging whether the site can be remediated by natural attenuation. At present, the evaluation methods for the natural attenuation capacity of organic pollutants in groundwater at home and abroad mainly include pollutant concentration trend analysis method, microbiological method, microcosm experiment method, stable isotope analysis method, computer simulation method, etc. However, these methods have high time and operation costs and cannot quantitatively estimate the degradation capacity of the site. The direct application of indoor test results is limited; they are greatly affected by the components of the pollution source, and the test cost is high and the uncertainty is strong. The hydrogeochemical indicator analysis method can quantitatively estimate the natural attenuation capacity of the site by monitoring the geochemical indicators (electron acceptors / degradation products) that indicate the biodegradation of microorganisms. The test method is simple and cost-effective. The degradation capacity of the contaminated aquifer is evaluated by monitoring the electron acceptors, which is also the core concept method of monitoring natural attenuation.

[0004] When calculating the natural attenuation capacity of a site through the hydrogeochemical indicator analysis method, the calculation of the consumption / production value of electron acceptors / degradation products is generally based on the difference between the electron acceptor / product concentration in the background well and the monitoring well where degradation occurs. In recent years, the research on this method generally selects the lowest pollution level or the highest electron acceptor concentration in the upstream of the background well as the electron acceptor concentration in the natural groundwater of the site, while the electron acceptor / product concentration in the monitoring well where degradation occurs is calculated based on the average value or expected value obtained based on statistical methods. These calculation methods may over-evaluate the degradation capacity of the site and fail to consider the different types of degradation under different redox effects dominated by site microorganisms in the site area. In view of the above problems in calculating the degradation rate, it is necessary to find a method for conservatively evaluating the degradation rate of contaminated sites based on microbial degradation. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the biodegradation capacity of aquifers in contaminated sites in view of the excessive evaluation of site degradation capacity in the prior art.

[0006] Another object of the present invention is to provide a method for evaluating the biodegradation rate of aquifers in contaminated sites in view of the excessive evaluation of site degradation capacity in the prior art.

[0007] Another object of the present invention is to provide a method for remediating a contaminated site.

[0008] Another object of the present invention is to provide a method for evaluating the degradation period of a contaminated site.

[0009] The technical solution adopted to achieve the purpose of the present invention is:

[0010] A method for calculating the biodegradability of aquifers in contaminated sites, comprising the following steps:

[0011] Step 1, determine the scope of pollution, set up sampling points in the polluted site, take groundwater samples at the sampling points, and measure the concentration of electron acceptors and degradation products;

[0012] Step 2, according to the measured concentration of each indicator in one or more periods, calculate the cumulative percentage of each indicator in one or more periods, and draw the cumulative probability distribution curve of each monitoring indicator with the electron acceptor concentration or the degradation product concentration as the abscissa and the corresponding cumulative probability as the ordinate;

[0013] Step 3, threshold range acquisition:

[0014] According to the cumulative probability distribution curves of different electron acceptors or degradation products obtained in step 2, the threshold ranges of stable segments of different electron acceptors or degradation products are obtained;

[0015] Step 4, calculate the degradation capacity:

[0016] The integral method is used to calculate the biodegradability of a certain electron acceptor, and the expression formula is:

[0017]

[0018] EBC x is the degradation capacity of a certain electron acceptor, in mg / L; x refers to the electron acceptor O2, NO3 - 、SO4 2- , Fe 3+ , Mn 4+ , CO2; C X (p) is the electron acceptor concentration when the cumulative probability is p; p1 and p2 are the cumulative percentages of electron acceptors corresponding to the threshold of the stable segment, and F is the utilization coefficient of petroleum pollutants, in mg / mg.

[0019] In the above technical solution, when setting the sampling points in step 1, the site hydrogeological conditions and pollutant distribution are determined according to the site investigation, and different monitoring areas are divided. At least 3 monitoring wells are selected in each monitoring area to form a monitoring well network to sample and monitor groundwater.

[0020] In the above technical solution, the monitoring area includes a background area or a flanking area, an upstream area, a source area and a downstream area.

[0021] In the above technical solution, the electron acceptors in step 1 include DO, NO3 - and / or SO4 2- .

[0022] In the above technical solution, the degradation products in step 1 include Fe 2+ , Mn 2+ and / or CH4.

[0023] In the above technical solution, the cumulative probability distribution curve is divided into four stages: adaptation, enhancement, stability and attenuation.

[0024] In the above technical solution, the cumulative probability distribution curve is a segmented straight line with multiple obvious turning points. The intersection of the two straight lines is regarded as the threshold of each degradation stage. The cumulative probability distribution curve of the electron acceptor corresponds to the adaptation segment, growth segment, stable segment and attenuation segment from top to bottom, and the cumulative probability distribution curve of the degradation product is the opposite.

[0025] In the above technical scheme, the coefficients of degrading petroleum pollutants by consuming electron acceptors for aerobic reaction, denitrification, manganese reduction, iron reduction, desulfurization, and methanogenesis are 3.14, 4.9, 10.7, 21.8, 4.7, and 0.78, respectively.

[0026] In the above technical solution, the sum of the degradation capacity of all electron acceptor microorganisms is expressed as:

[0027]

[0028] Another aspect of the present invention is a method for evaluating the biodegradation rate of aquifers in contaminated sites, comprising the method for calculating the biodegradation capacity of aquifers in contaminated sites and step 5.

[0029] Step 5: The total degradation capacity of all electron acceptor microorganisms is expressed as:

[0030]

[0031] The biodegradation rate of the aquifer is calculated from the lateral recharge renewal rate of the electron acceptor main flow in the groundwater, and the expression is:

[0032]

[0033] In the formula, v bio is the degradation rate of all electron acceptors in the aquifer, in kg / a; Q is the lateral recharge and renewal flow rate of electron acceptors in the main flow direction in groundwater, in m 3 / d.

[0034] Another aspect of the present invention is a contaminated site remediation method, comprising the above-mentioned method for calculating the biodegradability of aquifers in contaminated sites, and evaluation and remediation steps;

[0035] The assessment and remediation steps include:

[0036] Step 1.1, calculate the degradation capacity provided by each electron acceptor, each

[0037] Step 1.2, in order of the percentage of degradation capacity, supplement the electron acceptors in the contaminated site with salts of electron acceptors with a high percentage of degradation capacity to enhance the natural attenuation capacity of the site.

[0038] Another aspect of the present invention is a method for assessing the degradation period of a contaminated site, comprising the method for assessing the biodegradation rate of an aquifer in a contaminated site and a step of assessing the degradation period; the degradation period t = M / v bio , where M is the amount of pollutant leakage.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention is based on the growth and metabolism principle of degradation microorganisms. The types of microbial degradation can also be divided into four stages: adaptation, growth, stability, and attenuation. The ability to consume electron acceptors in each stage is very different. In mathematical statistics, it is the piecewise functions in the cumulative probability distribution curve of a certain electron acceptor. Since the strong consumption of electron acceptors by microorganisms mainly occurs in the stable stage, the present invention conservatively evaluates the site degradation type (aerobic stage, denitrification stage, manganese reduction stage, iron reduction stage, sulfate reduction stage, and methanogenesis stage) in the stable stage.

[0041] 2. The hydrogeochemical assessment method is to analyze the ability of the current groundwater environmental conditions to purify pollutants based on the changes in electron acceptor concentrations at different locations of the pollution plume, and then evaluate the sustainability of the natural attenuation capacity of the aquifer.

[0042] 3. This method specifically uses the transformation relationship between electron acceptors and pollutants to quantitatively evaluate the degradation capacity and degradation rate of pollutants. Therefore, using the changes in the concentration of electron acceptors in the stable stage of microbial degradation combined with the hydrogeochemical method to calculate the biodegradation capacity and degradation rate in the contaminated site can maximize the evaluation of the site's natural attenuation capacity and provide data guidance for subsequent site-enhanced natural attenuation remediation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the cumulative probability distribution curve, where (a) is the cumulative probability distribution curve of electron acceptors and (b) is the cumulative probability distribution curve of degradation products.

[0044] Figure 2 Schematic diagram of different electron acceptor / product consumption.

[0045] Figure 3 It is the cumulative probability distribution curve of each electron acceptor / degradation product in Example 2.

[0046] Figure 4 It is the cumulative probability distribution curve of each electron acceptor / degradation product in Example 3.

[0047] Figure 5 It is the cumulative probability distribution curve of each indicator in Example 4. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] Example 1

[0050] A method for assessing biodegradation rate of aquifers in contaminated sites, comprising the following steps:

[0051] Step 1, determine the scope of pollution and measure the hydrogeochemical indicators, which include the concentration of electron acceptors and the concentration of degradation products:

[0052] Based on the site investigation, the site hydrogeological conditions and pollutant distribution are determined, and different monitoring areas (background / flank area, upstream area, source area, downstream area) are divided. At least 3 monitoring wells are selected in each monitoring area to form a monitoring well network to monitor groundwater.

[0053] Using the bele tube and airbag pump to collect groundwater samples at different times and locations of the contaminated site, the inorganic chemical indicators DO and NO3 in the groundwater were determined. - 、SO4 2- , Fe 2+ , Mn 2+, CH4 concentration, the first three of which are electron acceptors and the last three are degradation products.

[0054] Step 2: Draw a cumulative probability distribution curve based on the growth law of microorganisms

[0055] Microorganisms use certain electron acceptors to degrade pollutants, which is divided into four stages: adaptation, enhancement, stability, and attenuation. Therefore, the cumulative probability distribution curve should show a segmented straight line with multiple obvious turning points. The intersection of two straight lines is regarded as the threshold of each degradation stage. According to the concentration of each indicator in different periods, the cumulative percentage of different indicators in each period is calculated, and the cumulative probability distribution curve of each monitoring indicator is drawn with the concentration of electron acceptor / degradation product as the horizontal axis and the corresponding cumulative probability as the vertical axis. The segmented curve of the electron acceptor corresponds to the adaptation segment, growth segment, stability segment and attenuation segment from top to bottom, while the degradation product is the opposite, such as Figure 1 shown.

[0056] Step 3: Get the threshold range

[0057] According to the cumulative probability distribution curves of different electron acceptors / degradation products drawn, the threshold ranges of different electron acceptors / degradation products at each stage are obtained.

[0058] Table 1 Electron acceptor / product concentration thresholds at different degradation stages

[0059] Degradation stage Electron acceptor concentration threshold Degradation product concentration threshold Adaptation phase C3~C4 0～C1 Growth stage C2~C3 C1~C2 Stable segment C1~C2 C2~C3 Attenuation section 0～C1 C3~C4

[0060] Step 4: Evaluation of degradation capacity and degradation rate

[0061] According to the cumulative probability distribution curve, the concentration range of different electron acceptors / degradation products was obtained, and the biodegradability of a certain electron acceptor was calculated by the integral method. The expression formula is:

[0062]

[0063] EBC x is the degradation capacity of a certain electron acceptor (mg / L); x refers to the electron acceptor O2, NO3 - 、SO4 2- , Fe 3+ , Mn 4+ , CO2; C X (p) is the electron acceptor concentration when the cumulative probability is p; F is the petroleum pollutant (in C n H n Expressed) utilization coefficient (mg / mg). From the perspective of microbial metabolism, the coefficients of electron acceptor consumption for degradation of petroleum pollutants by aerobic action, denitrification, manganese reduction, iron reduction, desulfurization and methanogenesis are 3.14, 4.9, 10.7, 21.8, 4.7 and 0.78 respectively.

[0064] The sum of the degradation capacity of all electron acceptor microorganisms is expressed as:

[0065]

[0066] Calculate the degradation capacity provided by each electron acceptor. That is, the ratio of the degradation capacity of electron acceptors or degradation products to the total degradation capacity.

[0067] The degradation capacity provided by the electron acceptor can provide a reference for the later enhancement of the natural attenuation capacity of the site. That is, if the degradation capacity provided by a certain electron in the site is relatively high, the electron acceptor salt can be added to the site to enhance the natural attenuation capacity of the site.

[0068] The degradation rate of the aquifer is calculated by the lateral recharge renewal rate (flow rate) of the electron acceptor main flow in the groundwater, which is expressed as:

[0069]

[0070] In the formula, v bio is the degradation rate of all electron acceptors in the aquifer (kg / a); Q is the main lateral recharge renewal flow of electron acceptors in groundwater (m 3 / d).

[0071] Under the premise that there is no artificial intervention in the site aquifer pollution, the site pollutant leakage amount can be obtained according to the site investigation, and the degradation period of organic pollution in the biodegradable site can be conservatively estimated. It can provide decision-making for assessing whether natural attenuation is feasible at the contaminated site. It also provides empirical evidence and basic data for the in-situ remediation of the site's groundwater.

[0072] Example 2

[0073] A method for assessing the natural attenuation capacity of a contaminated site comprises the following steps:

[0074] In different monitoring areas (background / flank area, upstream area, source area, downstream area) of a contaminated site, groundwater samples were collected and the DO and NO3 - 、SO4 2- , Fe 2+ , Mn 2+ , CH4 concentration, and draw the cumulative distribution probability curve of electron acceptors / degradation products at different periods. Since the site uses H2O2 for oxidation remediation, it affects the dissolved oxygen content and distribution characteristics in the groundwater; CH4 gas at this site is difficult to collect and thus difficult to detect, so the DO and CH4 indicators are no longer analyzed.

[0075] like Figure 3As shown in the figure, the cumulative probability distribution curve obtained by plotting the electron acceptor / degradation product can obtain the threshold range corresponding to different electron acceptor / product stable sections, NO3 - The concentration range is 2.99-9.83 mg·L -1 , Mn 2+ The concentration range is 1.85-5.13 mg·L -1 , Fe 2+ The concentration range is 0.9-1.02 mg·L -1 , SO4 2- The concentration range is 113.92-193.86 mg·L -1 .

[0076] According to the obtained threshold range, the degradation capacity of each electron acceptor was substituted into the calculation, and the degradation capacity of the electron acceptor in the aquifer during this period was calculated to be 18.41 mg / L, and the degradation rate was 886 kg / a.

[0077] Example 3

[0078] In March of a certain year, groundwater was collected from monitoring wells in different monitoring areas of a certain site, and NO3 in the water samples was measured. - 、SO4 2- , Fe 2+ , Mn 2+ According to the concentration of electron acceptor / degradation product of each indicator, the cumulative probability curve is drawn with the electron acceptor / product concentration as the horizontal axis and the cumulative percentage as the vertical axis.

[0079] like Figure 4 As shown in the figure, according to the cumulative probability distribution curve, the threshold range corresponding to different electron acceptor / product stable sections can be obtained. - The concentration range is 6.15-36.77 mg·L -1 , Mn 2+ The concentration range is 1.58-6.89 mg·L -1 , Fe 2+ The concentration range is 0.16-0.3 mg·L -1 , SO4 2- The concentration range is 111.3-186.7 mg·L -1 .

[0080] According to the obtained threshold range, the electron acceptor degradation capacity was calculated according to the formula and the electron acceptor degradation capacity of the aquifer during this period was 22.55 mg / L, and the degradation rate was 1086.4 kg / a.

[0081] Example 4

[0082] In April of a certain year, groundwater was collected from monitoring wells in different monitoring areas of a certain site, and NO3 in the water samples was measured. - 、SO4 2- , Fe 2+ , Mn 2+ According to the concentration of each electron acceptor / degradation product, the cumulative probability distribution curve is drawn with the concentration of each indicator as the horizontal axis and the cumulative percentage as the vertical axis.

[0083] like Figure 5 As shown, according to the cumulative probability distribution curve ( Figure 5 ) can obtain the threshold range corresponding to the stable segment of different indicators, NO3 - The concentration range is 6.15-43.39 mg·L -1 , Mn 2+ The concentration range is 1.82-6.28 mg·L -1 , Fe 2+ The concentration range is 0.62-2.91 mg·L -1 , SO4 2- The concentration range is 111.3-141.69 mg·L -1 .

[0084] Based on the obtained threshold range, it was calculated that the electron acceptor degradation capacity of the aquifer during this period was 14.17 mg / L, and the degradation rate was 682.8 kg / a.

[0085] Example 2-Example 4 are three-phase tests, and the values ​​of the aquifer biodegradation rates calculated in the three phases are similar, proving that the method is stable and applicable.

[0086] The average biodegradation capacity of the aquifer at the site calculated in three phases was 18.38 mg / L, and the conservatively estimated degradation rate of the electron acceptor in the aquifer at the site was 885.39 kg / a. The organic matter degradation rate calculated by this method is lower than the non-conservative degradation rate result of the previous isotope analysis method (1539 kg / a). The calculation results of the two methods are similar, proving that this method is feasible.

[0087] Based on the degradation capacity ratio provided by each electron acceptor, desulfurization (SO4 2- :71.68%)、denitrification(NO3 - :28.11%)、Manganese reduction (Mn 4+ :2.21%)、Fe 3+ :0.21%) degradation rates are 634.64kg / a, 248.86kg / a, 19.59kg / a, 1.87kg / a respectively. In this site, the electron acceptor desulfurization provides a high degradation ratio, so in the later stage, sulfate electron acceptors can be added to the site to enhance the natural attenuation of the site.

[0088] Under the current conditions of the site, the degradation period of petroleum pollutants at the site is conservatively calculated. The amount of oil leakage at the site is estimated to be 4160 kg by the methyl tert-butyl ether (MTBE) mean method, and the degradation period t = M / v. The conservative calculation results show that the degradation period t is 4.7 years.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for remediating a contaminated site, characterized in that: Includes methods for calculating the biodegradability of aquifers at contaminated sites, as well as assessment and remediation procedures; The method for calculating the biodegradability of aquifers in contaminated sites comprises the following steps: Step 1, determine the scope of pollution, set up sampling points in the polluted site, take groundwater samples at the sampling points, and measure the concentration of electron acceptors and degradation products; Step 2, according to the measured concentration of each indicator in one or more periods, calculate the cumulative percentage of each indicator in one or more periods, and draw the cumulative probability distribution curve of each monitoring indicator with the electron acceptor concentration or the degradation product concentration as the abscissa and the corresponding cumulative probability as the ordinate; Step 3, threshold range acquisition: According to the cumulative probability distribution curves of different electron acceptors or degradation products obtained in step 2, the threshold ranges of the stable segments of different electron acceptors or degradation products are obtained; the cumulative probability distribution curve is divided into four stages: adaptation, enhancement, stability and attenuation. The cumulative probability distribution curve is a segmented straight line with multiple obvious turning points. The intersection of two straight lines is regarded as the threshold of each degradation stage. The cumulative probability distribution curve of the electron acceptor corresponds to the adaptation segment, growth segment, stability segment and attenuation segment from top to bottom, and the cumulative probability distribution curve of the degradation product is the opposite; step 4, calculate the degradation ability: The integral method is used to calculate the biodegradability of a certain electron acceptor, and the expression formula is: EBC x is the degradation capacity of a certain electron acceptor, in mg / L; x refers to the electron acceptor O2, NO3 - 、SO4 2- , Fe 3+ , Mn 4+ , CO2; C X (p) is the concentration of electron acceptors when the cumulative probability is p; p1 and p2 are the cumulative percentages of electron acceptors corresponding to the threshold of the stable segment; F is the utilization coefficient of petroleum pollutants, in mg / mg; The repair steps include: Step 1.1, calculate the degradation capacity provided by each electron acceptor. Step 1.2, in order of the percentage of degradation capacity, add electron acceptors to the contaminated site to provide salts of electron acceptors with a high percentage of degradation capacity to enhance the natural attenuation capacity of the site.

2. The contaminated site remediation method according to claim 1, characterized in that: When setting the sampling points in step 1, the site hydrogeological conditions and pollutant distribution are determined according to the site investigation, and different monitoring areas are divided. At least 3 monitoring wells are selected in each monitoring area to form a monitoring well network to sample and monitor groundwater.

3. The contaminated site remediation method according to claim 2, characterized in that: The monitoring area includes a background area, a flanking area, an upstream area, a source area and / or a downstream area.

4. The contaminated site remediation method according to claim 1, characterized in that: The electron acceptors in step 1 include DO, NO3 - and / or SO4 2- .

5. The contaminated site remediation method according to claim 1, characterized in that: The degradation products in step 1 include Fe 2+ , Mn 2+ and / or CH4.

6. The contaminated site remediation method according to claim 1, characterized in that: The coefficients of degrading petroleum pollutants by consuming electron acceptors for aerobic reaction, denitrification, manganese reduction, iron reduction, desulfurization and methanogenesis were 3.14, 4.9, 10.7, 21.8, 4.7 and 0.78 respectively.

7. The contaminated site remediation method according to claim 1, characterized in that: The sum of the degradation capacity of all electron acceptor microorganisms is expressed as:

8. A method for assessing the degradation period of a contaminated site, characterized in that: Includes methods for assessing biodegradation rates in aquifers at contaminated sites and steps for assessing degradation years; The method for assessing biodegradation rate of aquifers in contaminated sites comprises the following steps: Step 1, determine the scope of pollution, set up sampling points in the polluted site, take groundwater samples at the sampling points, and measure the concentration of electron acceptors and degradation products; Step 2, according to the measured concentration of each indicator in one or more periods, calculate the cumulative percentage of each indicator in one or more periods, and draw the cumulative probability distribution curve of each monitoring indicator with the electron acceptor concentration or the degradation product concentration as the abscissa and the corresponding cumulative probability as the ordinate; Step 3, threshold range acquisition: According to the cumulative probability distribution curves of different electron acceptors or degradation products obtained in step 2, the threshold ranges of the stable segments of different electron acceptors or degradation products are obtained; the cumulative probability distribution curve is divided into four stages: adaptation, enhancement, stability and attenuation. The cumulative probability distribution curve is a segmented straight line with multiple obvious turning points. The intersection of two straight lines is regarded as the threshold of each degradation stage. The cumulative probability distribution curve of the electron acceptor corresponds to the adaptation segment, the growth segment, the stable segment and the attenuation segment from top to bottom, and the cumulative probability distribution curve of the degradation product is opposite to it; Step 4, calculate the degradation capacity: The integral method is used to calculate the biodegradability of a certain electron acceptor, and the expression formula is: EBC x is the degradation capacity of a certain electron acceptor, in mg / L; x refers to the electron acceptor O2, NO3 - 、SO4 2- , Fe 3+ , Mn 4+ , CO2; C X (p) is the concentration of electron acceptors when the cumulative probability is p; p1 and p2 are the cumulative percentages of electron acceptors corresponding to the threshold of the stable segment; F is the utilization coefficient of petroleum pollutants, in mg / mg; Step 5: The total degradation capacity of all electron acceptor microorganisms is expressed as: The biodegradation rate of the aquifer is calculated from the lateral recharge renewal rate of the electron acceptor main flow in the groundwater, and the expression is: In the formula, v bio is the degradation rate of all electron acceptors in the aquifer, in kg / a; Q is the lateral recharge and renewal flow rate of electron acceptors in the main flow direction in groundwater, in m 3 / d; Step 6: Under the premise that the site degradation rate remains unchanged, the degradation period t = M / v bio , where M is the amount of pollutant leakage.

9. The method for assessing the degradation period of a contaminated site according to claim 8, characterized in that: The pollutant is oil spill.

10. The method for assessing the degradation period of a contaminated site according to claim 8, characterized in that: The amount of pollutant leakage was estimated by the MTBE mean method.

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