Method and system for estimating turnover time of total nitrogen in lake water body

Abstract

The invention discloses a method and a system for estimating turnover time of total nitrogen in a lake water body, and belongs to the field of water environment monitoring and greenhouse effect evaluation. The method comprises the following steps: selecting TN concentration data, establishing a database D1, calculating a variable coefficient cv, and drawing an annual change curve of the TN concentration; recording the initial concentration ai and the end concentration of each decrease of the TN concentration and the duration of each decrease, and constructing a database D2; calculating the amplitude delta Ci of each drop, removing all corresponding durations meeting the condition that delta Ci is less than ai. Cvi from the database D2, and screening delta Cigt; a database D3 is established according to the duration di'and the concentration difference delta Ci 'corresponding to ai. Cvi; calculating the time ti required for lowering the TN by one unit, and establishing a database D4; and performing normal distribution analysis on ti in the database D4, selecting groups which are continuously grouped, marking ti in each group as ti 'when the total frequency of the selected groups is greater than 60% and the variation of ti is minimum, and calculating a mean value to obtain the turnover time.

Description

Technical Field

[0001] The present invention belongs to the field of water environment monitoring and greenhouse effect assessment, and particularly relates to a method and system for estimating the turnover time of total nitrogen in lake water bodies. Background Art

[0002] The IPCC has proposed a method for calculating the greenhouse gas emissions of sewage treatment plants by calculating the consumption of source substances (such as COD, T N etc.) that contribute to greenhouse gas production. When the lake ecosystem is regarded as a large natural bioreactor in nature, theoretically, as long as the consumption of source substances in the water body is obtained, the greenhouse gas emissions can be quickly calculated. Under specific processes and strict parameter control, the consumption of source substances in sewage treatment plants is default within the framework of residence time parameters. In comparison, the calculation of the consumption of greenhouse gas source substances in lakes is closely related to their turnover time (t) in the water body. The t parameter is defined as the time required for the consumption of a unit source substance in the lake water body under the support of long-term, continuous and fixed-step monitoring data. For a specific lake, the length of the t parameter is closely related to water temperature, ionic composition, biological community characteristics, etc., and is a characteristic parameter that describes the transformation of source substances. After obtaining the t value, the number of times the source substance completes turnover in the planned measurement period can be obtained, and the corresponding greenhouse gas emissions can be further estimated in combination with the consumption of the source substance in this period.

[0003] In the past, the turnover time of lakes was defined as the time required for all the water in the lake to be exchanged and updated once. Similar to the t parameter, both are characteristic parameters of the lake. The difference is that the turnover time of the lake focuses on the change in water volume, which is generally calculated by the outflow and inflow of the lake. The t parameter focuses on the turnover of substances in the lake water body, and there has been no report on relevant calculation methods so far.

[0004] Starting from the definition of the t parameter, as long as multiple sets of the consumption amounts of source substances per unit time are obtained from the target lake, the t parameter in the statistical sense can be obtained. Since the reaction system cannot be precisely designed and regulated like a sewage treatment plant, the concentration of the source substance in the lake water shows alternating characteristics of rising and falling on the time axis. Taking the monthly monitoring step as an example, the number of times, time, and corresponding durations of significant concentration decreases each year are often different. The influence of different durations on the calculation of the t parameter is that in some durations, the source substance may undergo multiple turnovers, while in some shorter durations, the source substance has not completed a full turnover. This makes it possible that in the calculation process, although it appears to be the consumption of the source substance per unit time on the surface, in fact, both linear and non-linear processes of source substance consumption coexist, resulting in deviations in the calculation of the t parameter. If a fixed duration is used to calculate the consumption amount of the source substance, for example, the average concentration is used for calculation every month, this may cause the consumption amount to show positive and negative values alternating on the time curve, and an effective t parameter cannot be obtained. In addition, the decrease in the concentration of the source substance in the lake water may be caused by reasons such as material migration, absorption, or adsorption, and these processes also "occupy" a certain duration. How to reasonably analyze this part of the influence from the total duration corresponding to the consumption amount of the source substance is also crucial for the t parameter.

[0005] In summary, for calculating the greenhouse gas emission amount based on the consumption amount of the source substance, the method for obtaining the t parameter has become the current bottleneck. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method and system for estimating the turnover time of total nitrogen in lake water, which solves the problems in the prior art.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for estimating the turnover time of total nitrogen in lake water includes the following steps:

[0009] Select T N concentration data and establish a database D1;

[0010] Calculate the average value aver, standard deviation sd, and coefficient of variation cv of the T N concentration in the database D1;

[0011] Using the monitoring step S w as the abscissa and the T N concentration as the ordinate, plot the annual change curve of the T N concentration in the database D1;

[0012] Based on the annual change curve, record the starting concentration a N and the ending concentration b i of each decrease in the Ti and T N The duration d experienced by each decrease in concentration i , construct database D2;

[0013] Calculate T N The amplitude of each decrease in concentration ΔC i , and based on the coefficient of variation, eliminate all durations in database D2 that satisfy ΔC i < a i ·cv;

[0014] Screen from database D2 for ΔC i > a i ·cv corresponding durations d i ' and the concentration decrease amplitude ΔC i ', establish database D3;

[0015] Based on database D3, calculate the time t required for T N to decrease by one unit i , establish database D4;

[0016] Perform a normal distribution analysis on t in database D4. Starting from the highest frequency array, successively select consecutive groups from its left and right sides; when the total frequency of the selected groups > 60%, and the variation of t among them is the smallest, mark t in each group as t i '; i Find the mean of t i ' to obtain T i turnaround time

[0017] to calculate the N2O release amount i ' N Turnaround time to calculate the N2O release amount

[0018] Furthermore, when establishing database D1, select a monitoring step size S w greater than 7d, less than 30d, and T concentration data continuously observed for more than 10 years N .

[0019] Furthermore, the calculation formula for the coefficient of variation cv is:

[0020] cv = sd / aver × 100%.

[0021] Furthermore, the calculation formula for the amplitude of each decrease in T concentration ΔC N is: i

[0022] ΔC i = a i - b i .​

[0023] Further, the N time t required for the concentration of T to decrease by one unit i is calculated by the formula:

[0024] t i = d′ i / ΔC i '.

[0025] Further, the release amount FN of N2O 2O is calculated by the formula:

[0026]

[0027] In the formula, is the release amount of N2O, is the consumption of T that contributes to the generation of N2O within the time period N , and is the conversion factor.

[0028] A system for estimating the turnover time of total nitrogen in lake water bodies includes:

[0029] Database D1 construction module: Select the concentration data of T N to establish the database D1;

[0030] Coefficient of variation calculation module: Calculate the average value aver, standard deviation sd, and coefficient of variation cv of the concentration of T in the database D1; N

[0031] T N Concentration change curve plotting module: Using the monitoring step S w as the abscissa and the concentration of T N as the ordinate, plot the annual change curve of the concentration of T in the database D1; N

[0032] Database D2 construction module: Based on the annual change curve, record the starting concentration a N , ending concentration b i and the duration d i experienced by the concentration of T each time it decreases, N and construct the database D2; i

[0033] Duration elimination module: Calculate the amplitude ΔC N of the decrease in the concentration of T each time, and based on the coefficient of variation, eliminate all durations that satisfy ΔC i < a i · cv from the database D2; i

[0034] Database D3 construction module: Screen ΔC from database D2 i > a i · The duration d corresponding to cv i ' and the concentration decrease amplitude ΔC i ', and establish database D3;

[0035] Database D4 construction module: Calculate T based on database D3 N The time t required for the concentration to decrease by one unit i and establish database D4;

[0036] Time screening module: Perform a normal distribution analysis on t in database D4 i Starting from the highest frequency array, sequentially select consecutive groups from its left and right; When the total frequency of the selected groups > 60%, and the variation of t among them i is the smallest, mark t in each group i as t i ';

[0037] Turnover time calculation module: Calculate the mean of t i ' to obtain T N Turnover time to calculate the N2O release amount

[0038] A computer storage medium stores a readable program. When the program runs, it can execute the above-mentioned method for estimating the turnover time of total nitrogen in lake water bodies.

[0039] An electronic device includes: a processor, a memory, a communication interface, and a communication bus. The processor, the memory, and the communication interface complete communication with each other through the communication bus;

[0040] The memory is used to store at least one executable instruction, and the executable instruction causes the processor to execute the operations corresponding to the above-mentioned method for estimating the turnover time of total nitrogen in lake water bodies.

[0041] A computer program product includes computer instructions, and the computer instructions instruct a computing device to execute the operations corresponding to the above-mentioned method for estimating the turnover time of total nitrogen in lake water bodies.

[0042] Advantages of the present invention:

[0043] This invention patent takes the total nitrogen (T N ) in lake water bodies as an example. Based on its long-term and continuous monitoring data, it creatively proposes a method under the constraint of monitoring step size, with T NA method for obtaining the turnover time by taking "each decline" of the concentration on the time curve as the entry point. "Each decline" not only eliminates the potential influence brought by the subjective judgment of significant concentration decline by different scholars, but also makes the calculation of the turnover time have consistent frequencies, the same durations, continuous effects, and controllable errors for the data obtained inter-annually, providing an important method support for estimating the N2O release amount in lake water based on the consumption of source substances. Brief Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0045] Figure 1 is the T in the lake water body of the present invention N Schematic diagram of "each decline" and its related parameters on the annual change curve of the concentration. Detailed Embodiments

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0047] Embodiment 1

[0048] A method for estimating the total nitrogen turnover time in lake water body includes the following steps:

[0049] S1, select the monitoring step S w greater than 7d, less than 30d, and the T N concentration data continuously observed for more than 10 years to establish the database D1;

[0050] In this embodiment, the T N concentration data is obtained from the monitoring data of the provincial control section. Calculate the average value of the monitoring concentrations of all sections according to S w and arrange the average values in the time process by year to form D1.

[0051] S2, taking the data of 10 consecutive years as the object, calculate the average value aver, standard deviation sd, and coefficient of variation cv of the T N concentration in the database D1;

[0052] The calculation formula of the coefficient of variation cv is:

[0053] cv = sd / aver×100%

[0054] S3, with a monitoring step size S w as the abscissa and T N concentration as the ordinate, plot the annual change curve of T N concentration that has been accumulated in database D1 for at least 10 years, as Figure 1 shown;

[0055] S4, find the part where the T N concentration decreases on the annual change curve of T N concentration, record the starting concentration a N of each decrease in T i concentration, the ending concentration b i and the duration d N experienced by each decrease in T i concentration, and establish database D2 containing a i b i d i ;

[0056] As Figure 1 shown, a1, a2, a3 are respectively: the starting concentrations when the T N concentration decreases for the 1st, 2nd, and 3rd times; b1, b2, b3 are respectively: the ending concentrations when the T N concentration decreases for the 1st, 2nd, and 3rd times; d1, d2, d3 are respectively: the durations experienced by the T N concentration when it decreases for the 1st, 2nd, and 3rd times; ΔC1, ΔC2, ΔC3 are respectively: the amplitudes of the T N concentration when it decreases for the 1st, 2nd, and 3rd times.

[0057] S5, calculate the amplitude ΔC N of each decrease in T i concentration, and based on the coefficient of variation, exclude all durations in database D2 that satisfy ΔC i < a i ·cv;

[0058] The calculation formula for the amplitude ΔC N of each decrease in T i concentration is:

[0059] ΔC i = a i - b i

[0060] The amplitude ΔC N of each decrease in the T i concentration corresponding to the excluded duration and the starting concentration a N of each decrease in T i concentration need to satisfy ΔCi <a i ·cv.

[0061] S6. Filter ΔC from database D2 i > a i The duration corresponding to ·cv and the concentration decline amplitude are respectively denoted as d i ', ΔC i ′, and establish database D3;

[0062] S7. Calculate T based on D3 N The time t required for the concentration to decrease by one unit i , and establish database D4

[0063] T N The time t required for the concentration to decrease by one unit i The calculation formula for is:

[0064] t i = d′ i / ΔC i '

[0065] S8. Perform a normal distribution analysis on t in D4, starting from the highest frequency array, and sequentially select consecutive groups on its left and right; when the total frequency of the selected groups (including the highest frequency array) > 60%, and the variation of t among them i is the smallest, mark t in each group i as t i '; i '

[0066] The following uses a specific case to introduce the specific process involved in S8:

[0067] ① When there are 18 data in t in D4 i , with a minimum value of 27.5, a maximum value of 130.3, and an average value of 70.6, divide the 18 data into 5 groups, namely < 30, 30 - 60, 60 - 90, 90 - 120, 120 - 150.

[0068] ② The number of data (frequency) in each group is 1, 7, 5, 3, and 2 respectively, and the frequencies are 5.56%, 38.89%, 27.78%, 16.67%, and 11.11% respectively.

[0069] ③ Locate the highest frequency array, that is, 30 - 60 (frequency 38.89%). Starting from this group, sequentially extend to its left and right to select consecutive groups, and the total frequencies of the two selected groups > 60% are obtained respectively, that is, the total frequency of {< 30, 30 - 60, 60 - 90} is 72.23%, and the total frequency of {30 - 60, 60 - 90} is 66.67%.

[0070] ④ Calculate the coefficient of variation (standard deviation / mean) of t in the group with a total frequency of 72.23% to be 31.27%, and that of the group with a total frequency of 66.67% is 31.27%. i

[0071] ⑤ Select the group with a smaller coefficient of variation, that is, the group with a total frequency of 66.67%. Mark t in ({30 - 60, 60 - 90}) among them i as ti′.

[0072] S9, find the mean of t i ' to obtain T N Turnaround time That is,

[0073] S10, based on T N Turnaround time Calculate the N2O emission

[0074] The emission of N2O The calculation formula is:

[0075]

[0076] Wherein, is the N2O emission, is the consumption of T contributing to N2O production within the time period N is the conversion factor.

[0077] In some embodiments, this calculation method is also applicable to the estimation of CH4 emission in lake water bodies, and only needs to replace T N with COD during the calculation and make corresponding adjustments. In addition, except for lakes, this method is applicable to water areas such as reservoirs, ponds, estuaries, and rivers.

[0078] Based on a similar inventive concept, an embodiment of the present invention also provides a computer storage medium storing a readable program, which can execute the above-mentioned method for estimating the total nitrogen turnover time in lake water bodies when the program runs.

[0079] Based on a similar inventive concept, an embodiment of the present invention provides an electronic device, including: a processor, a memory, a communication interface, and a communication bus, and the processor, the memory, and the communication interface complete communication with each other through the communication bus;

[0080] The memory is used to store at least one executable instruction, and the executable instruction causes the processor to execute the operations corresponding to the above-mentioned method for estimating the total nitrogen turnover time in lake water bodies.

[0081] Based on a similar inventive concept, an embodiment of the present invention further provides a computer program product, including computer instructions, where the computer instructions direct a computing device to execute the operations corresponding to the above-mentioned method for estimating the total nitrogen turnover time in lake water bodies.

[0082] Embodiment 2

[0083] Based on the method for estimating the total nitrogen turnover time in lake water bodies proposed in Embodiment 1, in this embodiment, a system for estimating the total nitrogen turnover time in lake water bodies is proposed, including:

[0084] Database D1 construction module: Select the T N concentration data to establish database D1;

[0085] Coefficient of variation calculation module: Calculate the average value aver, standard deviation sd, and coefficient of variation cv of the T N concentration in database D1;

[0086] T N Concentration change curve plotting module: Using the monitoring step S w as the abscissa and the T N concentration as the ordinate, plot the annual change curve of the T N concentration in database D1;

[0087] Database D2 construction module: Based on the annual change curve, record the starting concentration a N 、ending concentration b i and the duration d i experienced by each decrease in the T N concentration, and construct database D2; i

[0088] Duration elimination module: Calculate the amplitude of decrease ΔC N for each decrease in the T i concentration, and based on the coefficient of variation, eliminate all durations that satisfy ΔC i <a i ·cv from database D2;

[0089] Database D3 construction module: Screen the durations d i >a i ·cv and the corresponding concentration decrease amplitude ΔC i ' from database D2, and establish database D3; i

[0090] Database D4 construction module: Based on database D3, calculate the time t N required for the T i concentration to decrease by one unit, and establish database D4;

[0091] Time filtering module: In the database D4, for t i perform a normal distribution analysis. Starting from the highest-frequency array, successively select groups with continuous grouping from its left and right sides; when the total frequency of the selected groups > 60%, and among them, when the variation of t i is the smallest, mark t in each group as t i as t i ';

[0092] Turnaround time calculation module: Calculate the mean of t i ' to obtain T N Turnaround time to calculate the N2O release amount

[0093] The method of the present invention can be implemented in hardware, firmware, or can be implemented as software or computer code that can be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or can be implemented as computer code originally stored in a remote recording medium or a non-transitory machine-readable medium and downloaded through a network and will be stored in a local recording medium, so that the method described herein can be stored on such a software process on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component (such as a RAM, a ROM, a flash memory, etc.) that can store or receive software or computer code. When the software or computer code is accessed and executed by the computer, the processor, or the hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0094] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for estimating the turnover time of total nitrogen in lake water bodies, characterized in that, Including the following steps: Select T N Concentration data is selected to establish database D1; Calculate the average value aver, standard deviation sd, and coefficient of variation cv of the concentration of T in the database D1 N ; With a monitoring step size S w as the abscissa and T N concentration as the ordinate, plot the annual change curve of the T N concentration in the database D1; Based on the annual change curve, record T N The starting concentration a of each decrease in i concentration, the ending concentration b i and the duration d experienced by each decrease in T N concentration, and construct a database D2; i ​ Calculate T N The amplitude of decrease in concentration each time, ΔC i , and based on the coefficient of variation, eliminate from the database D2 all the durations that satisfy ΔC i <a i ·cv; Screen ΔC from database D2 i > a i · The duration d corresponding to cv i ' and the concentration decrease ΔC i ', and establish database D3; Based on database D3, calculate T N The time t required to decrease by one unit i , and establish database D4; Perform a normal distribution analysis on t in database D4 i starting from the highest frequency array, and successively select consecutive groups from its left and right sides; when the total frequency of the selected groups > 60%, and the variation of t i is the smallest among them, mark t in each group i as t i '; For t i 'Calculate the mean to obtain T N Turnaround time To calculate the N2O emission 2. The method for estimating the turnover time of total nitrogen in lake water bodies according to claim 1, wherein, When establishing the database D1, select the monitoring step size S w greater than 7 days, less than 30 days, and the T N concentration data observed continuously for more than 10 years.

3. The method for estimating the turnover time of total nitrogen in lake water bodies according to claim 1, characterized in that, The calculation formula of the coefficient of variation cv is: cv = sd / aver×100%.

4. The method for estimating the turnover time of total nitrogen in lake water according to claim 1, characterized in that, The said T N The amplitude of decrease ΔC of the concentration each time i The calculation formula is as follows: ΔC i = a i - b i .

5. The method for estimating the turnover time of total nitrogen in lake water bodies according to claim 4, characterized in that, The T N time t required for the concentration to decrease by one unit i The calculation formula is as follows: t i = d i ' / ΔC i '.

6. The method for estimating the turnover time of total nitrogen in lake water bodies according to claim 5, characterized in that The release amount of N2O The calculation formula is as follows: In the formula, is the N2O release amount, is the consumption of T N that contributes to N2O production within the time period, is the conversion factor.

7. An estimation system for the turnover time of total nitrogen in lake water bodies, characterized in that, Including: Database D1 construction module: Select T N concentration data to establish database D1; Coefficient of variation calculation module: Calculate the average aver, standard deviation sd, and coefficient of variation cv of the T concentration in database D1 N ; T N Concentration change curve plotting module: with the monitoring step S w as the abscissa and T N concentration as the ordinate, plot the annual change curve of T N concentration in the database D1; Database D2 construction module: Based on the annual change curve, record T N The starting concentration a of each decrease in the T i , the ending concentration b i and T N The duration d experienced by each decrease in the T concentration i , and construct database D2; Duration exclusion module: Calculate T N The amplitude of decrease in concentration each time, ΔC i , and based on the coefficient of variation, exclude all durations in database D2 that satisfy ΔC i <a i ·cv; Database D3 construction module: Screen ΔC from database D2 i > a i · Duration d corresponding to cv i ' and concentration decrease amplitude ΔC i ', and establish database D3; Database D4 construction module: Based on database D3, calculate T N The time t required for the concentration to decrease by one unit i , and establish database D4; Time Screening module: Perform a normal distribution analysis on t in database D4 i starting from the highest-frequency array, and successively select groups with consecutive groupings from its left and right sides; when the total frequency of the selected groups > 60%, and among them, the variation of t i is the smallest, mark t in each group i as t i '; Turnaround time calculation module: For t i 'Calculate the mean value to obtain T N Turnaround time to calculate the N2O release amount 8. A computer storage medium stores a readable program, characterized in that, When the program runs, it can execute a method for estimating the total nitrogen turnover time in lake water bodies described in any one of claims 1-6.

9. An electronic device, characterized in that, Including: A processor, a memory, a communication interface, and a communication bus. The processor, the memory, and the communication interface complete communication with each other through the communication bus; The memory is used to store at least one executable instruction, and the executable instruction causes the processor to execute operations corresponding to a method for estimating the total nitrogen turnover time in lake water bodies described in any one of claims 1-6.

10. A computer program product comprising computer instructions, characterized in that, The computer instruction instructs the computing device to execute operations corresponding to a method for estimating the total nitrogen turnover time in lake water bodies described in any one of claims 1-6.

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