A method for identifying pathways of agricultural non-point source pollution loss

Abstract

This invention provides a method for identifying agricultural non-point source pollution loss pathways, belonging to the field of integrated source control technology for non-point source pollution. The method includes the following steps: S1. Constructing a simulation area and collecting parameters from the simulation area; S2. Collecting relevant parameters of the initial state of the farmland system in the simulation area; S3. Measuring intermediate data during precipitation in the farmland ecosystem of the simulation area; S4. Calculating the nitrogen and phosphorus release concentration Ce(t) at the soil-water interface under precipitation splash erosion; S5. Calculating the total nitrogen and phosphorus runoff flux and the nutrient runoff flux generated by the horizontal mixed plug flow pathway based on the parameters in S1, S2, S3, and S4; S6. Identifying nutrient loss pathways. This method can accurately identify important factors affecting nitrogen and phosphorus runoff loss in paddy fields, improves the accuracy of assessing the emission reduction effect of agricultural non-point source pollution, and provides important scientific basis for optimizing agricultural non-point source pollution reduction technologies.

Description

Technical Field

[0001] This invention belongs to the field of integrated source control technology for non-point source pollution, specifically relating to a method for identifying pathways of agricultural non-point source pollution loss. Background Technology

[0002] Accurately estimating the amount of nutrient loss from farmland and identifying key driving factors is of great practical significance for reducing agricultural non-point source pollution and formulating strategies to prevent and control eutrophication of water bodies, as nitrogen and phosphorus loss in soil is a type of agricultural non-point source pollution.

[0003] CN111551683A discloses a method for quantitatively measuring nutrient release and transport fluxes in wetland systems under precipitation splash erosion. This invention is the first to consider soil solute release and transport fluxes under raindrop splash erosion, increasing the accuracy of nutrient surface runoff loss. Currently, the runoff loss process caused by precipitation splash erosion can be decomposed into a release process and a mixed plug flow process. The release process involves total release, net release, release adsorption and desorption processes, and release transport, occurring with the occurrence of precipitation splash erosion. The mixed plug flow process is accompanied by mixed plug flow transport and mixed plug flow adsorption and desorption processes. However, this invention overestimates the soil nitrogen and phosphorus mixed plug flow adsorption and desorption fluxes, treating them as total adsorption and desorption fluxes (mixed plug flow adsorption and desorption fluxes and release adsorption and desorption fluxes), leading to an underestimation of the net release flux. Consequently, its contribution to the quantitative measurement of precipitation splash erosion to nutrient runoff loss in wetland systems is underestimated. CN116431954A discloses a method for quantifying the contribution of precipitation splash erosion to nutrient runoff loss in farmland ecosystems. This invention is the first to consider the soil solute adsorption and desorption flux under raindrop splash erosion as a factor, and further refines the process into soil nitrogen and phosphorus mixed plug flow adsorption and desorption flux and release adsorption and desorption flux. By correcting the net release flux of precipitation splash erosion to nutrients in farmland ecosystems, the accuracy of nutrient surface runoff transport is increased.

[0004] In actual production trials, soil conditioners are often used to improve soil properties and reduce soil erosion. However, the same soil conditioner can have significantly different effects on reducing nitrogen and phosphorus loss in different regions because soil conditioners prevent soil nutrient loss through different pathways. Furthermore, the pathways of soil nutrient loss during precipitation also vary considerably in different regions. Therefore, identifying the pathways of nutrient loss in farmland ecosystems and then using different soil conditioners or developing improvement strategies accordingly is of great significance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for identifying agricultural non-point source pollution loss pathways. This method is the first to investigate the nitrogen and phosphorus release and transport fluxes in the horizontal and vertical directions of paddy fields under the action of raindrop splash erosion. It can accurately identify the important factors affecting nitrogen and phosphorus runoff loss in paddy fields, improve the accuracy of assessing the emission reduction effect of agricultural non-point source pollution, and provide important scientific basis for optimizing agricultural non-point source pollution emission reduction technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for identifying pathways of agricultural non-point source pollution, comprising the following steps:

[0008] S1. Construct the simulation area and collect simulation area parameters;

[0009] S2. Collect relevant parameters of the initial state of the farmland system in the simulation area;

[0010] S3. Measure intermediate data on precipitation processes in the farmland ecosystem of the simulated area;

[0011] S4. Calculate the nitrogen and phosphorus release concentration Ce(t) at the soil-water interface under the action of precipitation splash erosion;

[0012] S5 calculates the total nitrogen and phosphorus runoff flux and the nutrient runoff flux generated by the horizontal mixed plug flow pathway based on the parameters in S1, S2, S3, and S4.

[0013] S6. Identify pathways of nutrient loss;

[0014] The identification method is as follows:

[0015] The contribution rates of nutrient runoff flux generated by the horizontal mixing plug flow pathway and nutrient runoff flux generated by nitrogen release at the soil-water interface to the total nitrogen and phosphorus runoff flux were calculated respectively, and the nutrient loss pathway was judged based on the contribution rates.

[0016] Preferably, the simulated area in S1 is a farmland ecosystem without netting.

[0017] Preferably, the simulation area parameters in S1 include farmland area A and field ridge height H0.

[0018] Preferably, the relevant parameters in S2 include the water level height H(t) of the farmland ecosystem in the initial state and the initial nutrient concentration Cpaddy(t) of the paddy field water layer.

[0019] Preferably, the intermediate data in S3 includes the average nutrient concentration C in precipitation. pre (t); When runoff occurs, measure the depth R of continuous rainfall after runoff occurs. (t+1) .

[0020] Preferably, the nitrogen and phosphorus release concentration Ce(t) at the water-soil interface in S4 is calculated according to the calculation formula of Ce(t) in Chinese Patent No. 202310699523.9.

[0021] Preferably, the formula for calculating the total nitrogen and phosphorus runoff flux in S5 is:

[0022]

[0023] In the formula, Qi is the total nitrogen and phosphorus runoff flux, A is the farmland area; C pre (t) represents the average nutrient concentration in precipitation, R (t+1) H represents the depth of continuous rainfall following runoff generation. (t) Let C be the water level height of the farmland ecosystem at time t. paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, Ce(t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the splash erosion effect of precipitation, and H0 represents the height of the paddy field ridge.

[0024] Preferably, the formula for calculating the nutrient runoff flux generated by the horizontal mixing plug flow pathway in S5 is as follows:

[0025]

[0026] In the formula, Q Li The nutrient runoff flux generated by the horizontal mixing plug flow pathway is represented by A, where A is the farmland area; C pre (t) represents the average nutrient concentration in precipitation, R (t+1) H represents the depth of continuous rainfall following runoff generation. (t) Let C be the water level height of the farmland ecosystem at time t. paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, Ce(t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the splash erosion effect of precipitation, and H0 represents the height of the paddy field ridge.

[0027] Preferably, the nutrient runoff flux generated by nitrogen release at the soil-water interface in S6 is as described in Chinese Patent No. 202310699523.9. N The formula for calculating (t) is used.

[0028] Preferably, the contribution rate in S6 is calculated using the following methods:

[0029] Formula for calculating the contribution rate of nutrient runoff flux caused by nitrogen release at the soil-water interface to total nitrogen and phosphorus runoff flux:

[0030]

[0031] Formula for calculating the contribution rate of nutrient runoff flux generated by the horizontal mixing plug flow pathway to total nitrogen and phosphorus runoff flux:

[0032]

[0033] As a preferred approach, after identifying the pathways of nutrient loss, nutrient loss can be targeted and controlled based on these pathways.

[0034] It contains at least the following beneficial technical effects:

[0035] This invention discovers that the runoff loss mechanism mainly includes horizontal mixing and flow action and vertical splashing and release action. By detecting and calculating the contribution rate of these two factors to nutrient runoff loss in farmland ecosystems, the soil nutrient loss pathways in different regions can be accurately determined. Soil conditioners or improvement methods can also be evaluated, thereby enabling targeted soil improvement. Attached Figure Description

[0036] Figure 1 Contribution rate of nitrogen runoff from different sources. Detailed Implementation

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] The main sources of nitrogen loss from paddy fields through nitrogen runoff include rainfall, irrigation, nitrogen release at the soil-water interface, and mixed flow.

[0042] Patent CN116431954A discloses a method for quantifying the contribution of precipitation splash erosion to nutrient runoff loss in farmland ecosystems, specifically the net nutrient release flux E of precipitation splash erosion in farmland ecosystems. N The corrected formula for (t) is: E N (t)=Q N (t)-SE N (t). Nitrogen release at the soil-water interface is based on the effect of precipitation splash erosion on paddy fields. The contribution rate of nitrogen release at the soil-water interface is equal to the ratio of net precipitation splash erosion flux to runoff. It can be calculated according to the calculation formula for the contribution of precipitation splash erosion to nutrient runoff loss in farmland ecosystems as described in patent CN116431954A. The calculation formula is as follows:

[0043]

[0044] Furthermore, this invention found that the main influencing factors of nitrogen runoff loss in paddy fields are nutrient runoff loss generated by horizontal mixing and flow pathways and nitrogen release at the soil-water interface. By exploring the contribution rate of these two factors to nitrogen runoff loss in paddy fields, the nutrient loss pathway of the plot can be determined and targeted control can be carried out.

[0045] Specifically, the method for identifying pathways of agricultural non-point source pollution loss includes the following steps:

[0046] S1. Construct the simulation area and collect simulation area parameters;

[0047] S2. Collect relevant parameters of the initial state of the farmland system in the simulation area;

[0048] S3. Measure intermediate data on precipitation processes in the farmland ecosystem of the simulated area;

[0049] S4. Calculate the nitrogen and phosphorus release concentration Ce(t) at the soil-water interface under the action of precipitation splash erosion;

[0050] S5 calculates the total nitrogen and phosphorus runoff flux and the nutrient runoff flux generated by the horizontal mixed plug flow pathway based on the parameters in S1, S2, S3, and S4.

[0051] S6. Identify pathways of nutrient loss;

[0052] The identification method is as follows:

[0053] The contribution rates of nutrient runoff flux generated by the horizontal mixing plug flow pathway and nutrient runoff flux generated by nitrogen release at the soil-water interface to the total nitrogen and phosphorus runoff flux were calculated respectively, and the nutrient loss pathway was judged based on the contribution rates.

[0054] The simulated area in S1 is a farmland ecosystem without netting.

[0055] The simulation parameters in S1 include farmland area A and field ridge height H0.

[0056] The relevant parameters in S2 include the water level height H(t) of the farmland ecosystem in the initial state and the initial nutrient concentration Cpaddy(t) of the paddy field water layer.

[0057] The intermediate data in S3 includes the average nutrient concentration C in precipitation. pre (t); When runoff occurs, measure the depth R of continuous rainfall after runoff occurs. (t+1) .

[0058] The nitrogen and phosphorus release concentration Ce(t) at the water-soil interface in S4 is calculated according to the calculation formula of Ce(t) described in Chinese Patent No. 202310699523.9; specifically:

[0059] C e (t)=k1C Paddy (t)

[0060] The formula for calculating the total nitrogen and phosphorus runoff flux in S5 is as follows:

[0061]

[0062] In the formula, Qi is the total nitrogen and phosphorus runoff flux, A is the farmland area; C pre (t) represents the average nutrient concentration in precipitation, R (t+1) H represents the depth of continuous rainfall following runoff generation. (t) Let C be the water level height of the farmland ecosystem at time t. paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, Ce(t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the splash erosion effect of precipitation, and H0 represents the height of the paddy field ridge.

[0063] Preferably, the formula for calculating the nutrient runoff flux generated by the horizontal mixing plug flow pathway in S5 is as follows:

[0064]

[0065] In the formula, Q Li The nutrient runoff flux generated by the horizontal mixing plug flow pathway is represented by A, where A is the farmland area; C pre(t) represents the average nutrient concentration in precipitation, R (t+1) H represents the depth of continuous rainfall following runoff generation. (t) Let C be the water level height of the farmland ecosystem at time t. paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, Ce(t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the splash erosion effect of precipitation, and H0 represents the height of the paddy field ridge.

[0066] The nutrient runoff flux generated by nitrogen release at the soil-water interface in S6 is as described in Chinese Patent No. 202310699523.9, E. N The formula for calculating (t) is used.

[0067] The contribution rate in S6 is calculated using the following methods:

[0068] Formula for calculating the contribution rate of nutrient runoff flux caused by nitrogen release at the soil-water interface to total nitrogen and phosphorus runoff flux:

[0069]

[0070] Formula for calculating the contribution rate of nutrient runoff flux generated by the horizontal mixing plug flow pathway to total nitrogen and phosphorus runoff flux:

[0071]

[0072] The two calculation formulas have the same denominator, but are expressed differently.

[0073] After identifying the pathways of nutrient loss, nutrient loss can be controlled in a targeted manner based on these pathways.

[0074] Example

[0075] (1) An artificial precipitation control experiment was conducted, with the following groups: CK group (no netting, no PAM addition, normal fertilization), NE group (netting, no PAM addition, normal fertilization), and P1 group (no netting, 2g / m² PAM addition). 2 PAM (normal fertilization) and P2 group (no mesh covering, 4g / m² added) 2 PAM (normal fertilization) was used in 4 treatments, with 2 parallel plots per treatment, for a total of 8 plots. Each plot had an area of ​​6m². 2 (2m×3m)

[0076] (2) Saturated topsoil (0-20cm) from paddy fields in the plots was collected before, during, and after the start of precipitation and placed in a preservation box to prevent disturbance. The same precipitation intensity (60mm / h), the same precipitation time (1h), and the same precipitation splash force were controlled by the artificial precipitation control system. Surface water, runoff, precipitation, and nitrogen and phosphorus release solution at the soil-water interface were collected from the paddy fields of both plots at 20min, 40min, and 60min after the start of precipitation and stored in a refrigerator for later testing.

[0077] (3) Perform data collection and calculation according to the method described above.

[0078] Experimental results:

[0079] In group CK, the contribution rate of nitrogen release at the soil-water interface to runoff loss was 20.6% at 20 min after rainfall, and the contribution rate of mixed plug flow was 68.7%. In group P1, the contribution rate of nitrogen release at the soil-water interface to runoff loss was 22.3%, and the contribution rate of mixed plug flow was 66.5%. In group P2, the contribution rate of nitrogen release at the soil-water interface to runoff loss was 23.0%, and the contribution rate of mixed plug flow was 65.5%. The contribution rates of nitrogen release at the soil-water interface to runoff loss in groups P1 and P2 were higher than those in group CK, but not significantly (p>0.05).

[0080] At 40 min after rainfall, the contribution rate of nitrogen release at the soil-water interface to runoff loss was 16.6% in the CK group and 73.8% in the mixed plug flow. In the P1 group, the contribution rate was 15.2% and 75.9% respectively. In the P2 group, the contribution rate was 15.5% and 75.4% respectively. In contrast to 20 min after rainfall, the contribution rates of nitrogen release at the soil-water interface to runoff loss in the P1 and P2 groups were lower than those in the CK group. The contribution rates of nitrogen release at the soil-water interface to runoff loss in all treatments were significantly lower than those at 20 min after rainfall (p<0.05).

[0081] At 60 min after rainfall, the contribution rate of nitrogen release at the soil-water interface to runoff loss was 14.0% in group CK and 77.6% in group P1. The contribution rate of nitrogen release at the soil-water interface to runoff loss was 13.4% and 78.5% in group P2. The contribution rate of nitrogen release at the soil-water interface to runoff loss was 14.6% and 77.0% in group P2. There was no significant difference in the contribution rate of nitrogen release at the soil-water interface to runoff loss among the different treatments (p>0.05).

[0082] Contribution rate of nitrogen runoff from different sources, see Figure 1It is evident that the main influencing factors of nitrogen runoff loss in paddy fields are nutrient runoff loss generated by horizontal mixing and flow pathways and nitrogen release at the soil-water interface.

[0083] In this experiment, by comparing the nitrogen runoff loss, nitrogen release and nitrogen release and transport under different treatments during rainfall, it was found that the application of PAM could significantly reduce nitrogen runoff loss (p<0.05), and increase nitrogen release and nitrogen release and transport but not significantly (p>0.05). Therefore, the reduction in runoff loss due to the addition of polyacrylamide (PAM) mainly comes from the mixing and plug flow process.

[0084] This demonstrates that the method of the present invention can determine the pathways of nutrient loss in a plot of land, as well as the pathways of soil amendment or amendment methods.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for identifying pathways of agricultural non-point source pollution runoff, characterized in that, Includes the following steps: S1. Construct a farmland ecosystem without netting and collect parameters of the simulation area, including farmland area A and field ridge height H0, and construct a control plot with netting coverage; S2. Collect relevant parameters of the initial state of the farmland system in the simulation area, including the water level height H(t) of the farmland ecosystem and the initial nutrient concentration C of the paddy field water layer under the initial state. paddy (t); S3. Measure intermediate data on precipitation processes in the simulated farmland ecosystem, including the average nutrient concentration C in the precipitation. pre (t); When runoff occurs, measure the continuous rainfall depth R(t+1) after the runoff occurs; S4. Calculate the nitrogen and phosphorus release concentration C at the soil-water interface under the action of precipitation splash erosion. e (t); S5. Calculate the total nitrogen and phosphorus runoff flux and the nutrient runoff flux generated by the horizontal mixed plug flow pathway based on the parameters in S1, S2, S3, and S4. The formula for calculating the total nitrogen and phosphorus runoff flux is as follows: ， In the formula, Q i C represents the total nitrogen and phosphorus runoff flux, where A is the farmland area; pre (t) represents the average nutrient concentration in the precipitation, R(t+1) represents the continuous rainfall depth after runoff generation, H(t) represents the water level height of the farmland ecosystem at time t, and C paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, C e (t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the action of precipitation splash erosion, and H0 represents the height of the field ridge; The formula for calculating the nutrient runoff flux generated by the horizontal mixing plug flow pathway is as follows: ， In the formula, Q Li The nutrient runoff flux generated by the horizontal mixing plug flow pathway is represented by A, where A is the farmland area; C pre (t) represents the average nutrient concentration in the precipitation, R(t+1) represents the continuous rainfall depth after runoff generation, H(t) represents the water level height of the farmland ecosystem at time t, and C paddy (t) represents the initial nutrient concentration of the paddy field water layer at the start of rainfall, C e (t) represents the nitrogen and phosphorus release concentration at the soil-water interface under the action of precipitation splash erosion, and H0 represents the height of the field ridge; S6. Identify pathways of nutrient loss; The identification method is as follows: The contribution rates of nutrient runoff flux generated by the horizontal mixing plug flow pathway and nutrient runoff flux generated by nitrogen release at the soil-water interface to the total nitrogen and phosphorus runoff flux were calculated respectively, and the nutrient loss pathway was judged based on the contribution rates. The contribution rate is calculated using the following methods: Formula for calculating the contribution rate of nutrient runoff flux caused by nitrogen release at the soil-water interface to total nitrogen and phosphorus runoff flux: ， Formula for calculating the contribution rate of nutrient runoff flux generated by the horizontal mixing plug flow pathway to total nitrogen and phosphorus runoff flux: ， After identifying the pathways of nutrient loss, the study aimed to control nutrient loss by comparing nitrogen runoff loss, nitrogen release, and nitrogen release and transport during rainfall under different treatments.

2. The method for identifying agricultural non-point source pollution runoff pathways according to claim 1, characterized in that, The nitrogen and phosphorus release concentration C at the water-soil interface in S4 e (t) As described in Chinese Patent No. 202310699523.9, C e The formula for calculating (t) is used.

3. The method for identifying agricultural non-point source pollution runoff pathways according to claim 1, characterized in that, The nutrient runoff flux generated by nitrogen release at the soil-water interface in S6 is as described in Chinese Patent No. 202310699523.9, E. N The formula for calculating (t) is used.

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