Park scale air quality mode chemical mechanism improvement method for improving ozone simulation capability

Abstract

The invention discloses a park scale air quality mode chemical mechanism improvement method for improving ozone simulation capability, and belongs to the technical field of ozone pollution treatment. The method comprises the following steps: by introducing a VOCs related reaction path, enriching a kinetic equation of ozone generation, so that the model can describe a more complex atmospheric chemical process. Theoretically, the reaction items of the model are more comprehensive, and the ozone simulation requirements under different pollution scenes can be met. Through introduction of VOCs, key links in a NOx-O3 reaction chain can be supplemented, and the adaptability and predictive ability of the model to the actual atmospheric environment are improved. And the model structure is improved, so that the simulation result has a more scientific basis. Due to the fact that emission characteristics of VOCs in different regions and time periods are greatly different, the applicability of a traditional model is limited. According to the model, the reaction rate can be dynamically adjusted according to the actual emission condition of VOCs, and the model is suitable for various atmospheric environments and has a wider application prospect.

Description

Technical Field

[0001] This invention relates to the field of ozone pollution control technology, specifically to a method for improving the chemical mechanism of an air quality model at the park scale to enhance ozone simulation capabilities. Background Technology

[0002] With ozone pollution becoming increasingly prominent, the accuracy of existing park-scale air quality models in simulating ozone generation and transformation processes urgently needs to be improved, especially in terms of chemical mechanisms.

[0003] The AERMOD model is an atmospheric diffusion model based on Gaussian plume theory, suitable for simulating local pollutant diffusion under steady-state conditions, especially performing well in small-scale, refined simulations. The main chemical mechanisms involving O3 in AERMOD are as follows: Ozone Limitation Method (OLM) and Plume Volume Molar Ratio Method (PVMRM) can be used for most pollution sources, estimating the initial conversion of nitrogen oxides (NOx) emissions to nitrogen dioxide based on ambient ozone levels and plume characteristics. OLM only considers NO2 formation based on ambient ozone levels, while PVMRM considers distance-dependent conversion rates based on ambient ozone. Starting with version 16216, PVMRM and OLM are regulatory options that can be specified using the DFAULT keyword in the AERMOD model. The General Reaction Set Method (GRSM) was introduced into AERMOD as the ALPHA option in version 21112, upgraded to the BETA option in version 22112, and subsequently upgraded to a regulatory option with the release of AERMOD 2024. GRSM originates from a technical approach documented by Carruthers et al. in 2017 that considers the reactions between NO, NO2, and O3 in the atmosphere. This approach employs a plume entrainment calculation method similar to PVMRM, but adds a "reaction rate" based on solar radiation and the propagation time from the pollution source to the receptor. The reaction rate is based on the Universal Reaction Set (GRS) chemistry scheme, a semi-empirical photochemical model originally developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia for multi-step conversions between NO, NO2, and O3.

[0004] The GRSM mechanism mainly involves the following two chemical reactions:

[0005] NO2 + hv → NO + O3

[0006] NO + O3 → NO2

[0007] The following chemical reaction scheme was then applied to the total concentration of unreacted contaminants at each receptor site:

[0008] d[NO2] / dt=k[NO][O3]-J[NO2]

[0009] d[NO] / dt=J[NO2]-k[NO][O3]

[0010] d[O3] / dt=J[NO2]-k[NO][O3]

[0011] The reaction coefficient k and the photolysis rate J are defined as follows:

[0012] k = 4.405 × 10 -2 exp(-1370 / T0)

[0013] J = 8 × 10 -4 exp(-10 / Q)+7.4×10 -6 Q

[0014] Where T0 is temperature and Q is solar radiation.

[0015] Both PVMRM and OLM assume that the reaction of NO with ambient O3 to produce NO2 is an instantaneous reaction. Although the reaction rate is relatively fast, it is not actually instantaneous; its rate is affected by the transport time of pollutants from the source to the downwind receptor. The GRSM mechanism builds upon this by introducing a "reaction rate" based on solar radiation intensity and pollutant propagation time, but its chemical reactions only involve NO, NO2, and O3, neglecting the influence of VOCs. In fact, VOCs play a crucial role in ozone formation and depletion. Ignoring the influence of VOCs often leads to significant discrepancies between model simulations and actual observations, reducing the model's accuracy and applicability.

[0016] In the troposphere, ozone is mainly produced by the reaction of VOCs and NO. x Both NO and O3 are important precursors to ozone formation, generated through photochemical reactions. Specifically, NO2 undergoes photolysis under light with wavelengths less than 424 nm to produce ground-state oxygen atoms, which then react with oxygen to form ozone. The newly generated ozone can react with NO to regenerate NO2. Without the involvement of other species, a dynamic equilibrium will be maintained between NO2, NO, and O3, making it difficult for ozone concentrations to accumulate. However, in the actual atmospheric environment, the presence of VOCs and other substances triggers a free radical cycle, promoting ozone accumulation. In the photochemical formation of ozone, NO... x It can directly generate ozone, while VOCs increase NO by driving free radical reactions. x Efficiency in promoting ozone formation. Summary of the Invention

[0017] The purpose of this invention is to provide an improved chemical mechanism method for campus-scale air quality models that enhances ozone simulation capabilities. Based on the existing NO, NO2, and O3 reaction mechanisms, it innovatively introduces the reaction process of VOCs. By incorporating VOCs into the kinetic model of ozone formation and consumption, the actual ozone formation mechanism in the atmosphere can be more comprehensively reflected, thereby significantly improving the accuracy of ozone concentration simulation.

[0018] To address the aforementioned technical problems, this invention provides a method for improving the chemical mechanisms of campus-scale air quality models to enhance ozone simulation capabilities, comprising the following steps:

[0019] The active organic compound ROC undergoes a photolysis reaction to yield the free radical pool RP;

[0020] NO is oxidized to NO2 via a free radical pool RP;

[0021] NO2 is photolyzed to produce NO and O3.

[0022] O3 and NO react to produce NO2;

[0023] The free radical pool RP is consumed by reaction.

[0024] The free radical pool RP reacts with NO2 to produce inactive nitrogen compounds.

[0025] Preferably, the inactive nitrogen compound includes gaseous nitrogen product SGN and non-gaseous nitrogen product SNGN.

[0026] Preferably, the reaction formula for the photolysis of the active organic compound ROC is:

[0027] ROC+hv →RP+ROC (1)

[0028] The reaction formula for oxidizing NO to NO2 via the free radical pool RP is:

[0029] RP + NO → NO2 (2)

[0030] The reaction equation for the photolysis of NO2 is:

[0031] NO2 + hv → NO + O3 (3) The reaction equation for the reaction between O3 and NO is:

[0032] NO + O3 → NO2 (4)

[0033] The reaction formula for the reaction consumption of the free radical pool RP is:

[0034] RP+RP →RP (5)

[0035] The reaction formula for generating gaseous nitrogen product SGN is:

[0036] RP + NO2 → SGN (6)

[0037] The reaction formula for generating the non-gaseous nitrogen product SNGN is:

[0038] RP+NO2 →SNGN (7).

[0039] Preferably, the reaction rates of reactions (1) to (7) are:

[0040] R1 = k1[ROC]

[0041] R2 = k2[RP][NO]

[0042] R3 = k3[NO2]

[0043] R4 = k4[NO][O3]

[0044] R5 = k5[RP][RP]

[0045] R6 = k6[RP][NO2]

[0046] R7 = k7[RP][NO2] where: R1 to R7 are the reaction rates of reaction formulas (1) to (7), k1 to k7 are the chemical reaction rate constants of reaction formulas (1) to (7), [RP] is the concentration of RP, [NO] is the concentration of NO, [NO2] is the concentration of NO2, [ROC] is the concentration of ROC, and [O3] is the concentration of O3.

[0047] Preferably, R1 to R7 are written in the form of differential equations as follows:

[0048]

[0049]

[0050] In the formula: k1~k7 are the chemical reaction rate constants of reaction formulas (1) to (7), respectively.

[0051] Preferably, the calculation formulas for k1 to k7 are as follows:

[0052]

[0053] k2 = 5482e 242 / T (ppm -1 min -1 )

[0054]

[0055] k4 = 2643e -1370 / T (ppm -1 min -1 )

[0056] k5 = 10000 (ppm) -1 min -1 )

[0057] k6 = 120 (ppm) -1 min -1 )

[0058] k7 = 120 (ppm) -1 min -1 )

[0059] In the formula: T represents temperature, x represents the solar zenith angle, and TSR represents total solar radiation. denoted by , where represents the average activity coefficient of the ROC species mixture, and f(T) represents the temperature function.

[0060] Preferably, the average activity coefficient of the ROC species mixture The formula for calculating the temperature function f(T) is as follows:

[0061]

[0062] γ = 4.7

[0063] In the formula: a i The value represents the activity coefficient of different ROC species, and T represents the temperature.

[0064] Preferably, the concentration of RP is calculated according to the following formula:

[0065] k5[RP] 2 +(k2[NO]+(k6+k7)[NO2])[RP]-k1[ROC]=0

[0066] In the formula: [RP] is the concentration of RP, [NO] is the concentration of NO, [NO2] is the concentration of NO2, [ROC] is the concentration of ROC, and [O3] is the concentration of O3.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] In atmospheric chemical reactions, the formation of O3 is not only affected by NO xOzone formation is also closely related to the presence of VOCs. VOCs participate in photochemical reactions, generating free radicals that promote the conversion of NO to NO2, thus accelerating ozone formation. Traditional models do not consider VOCs, leading to underestimation of ozone formation rates. This invention enriches the kinetic equations of ozone formation by introducing VOC-related reaction pathways, enabling the model to describe more complex atmospheric chemical processes. Theoretically, the model's reaction terms are more comprehensive, adapting to the ozone simulation needs under different pollution scenarios. Theoretical derivation shows that the introduction of VOCs can supplement NO... x This invention addresses a key link in the O3 reaction chain, enhancing the model's adaptability and predictive ability to real-world atmospheric conditions. The improved model structure makes the simulation results more scientifically grounded. Due to significant differences in VOC emission characteristics across different regions and time periods, traditional models have limited applicability. This invention's model can dynamically adjust the reaction rate based on actual VOC emissions, making it suitable for various atmospheric environments and offering broader application prospects. Attached Figure Description

[0069] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0070] Figure 1 The model displays the hourly variations between simulated and observed values. All three curves show a clear diurnal variation in O3 concentration: lowest in the early morning, gradually increasing during the day, peaking in the afternoon, and gradually decreasing after dusk. This trend is consistent with the typical diurnal variation of urban atmospheric O3, mainly influenced by sunlight, temperature, and precursor emissions. The original model mechanism generally underestimated O3 concentration, especially during the high-value periods of the day. The improved mechanism's simulation results are significantly better than the original mechanism, generally closer to the observed values, especially during the high-value periods of the day, and better reproduce the peak value and variation trend of O3. This is because the improved mechanism introduces VOCs, which are important precursors to O3 formation, especially during sunny days, through interaction with NO. x The photochemical reaction promotes the generation of O3.

[0071] Figure 2The spatial distribution of O3 concentration near point sources in industrial parks is illustrated. The decrease in O3 concentration near point sources is mainly due to the titration reaction between NO emitted from these sources and O3, consuming a large amount of O3 and creating a low-O3 zone. As the distance from the point source increases, NO concentration gradually decreases, while the O3 regeneration process intensifies, leading to a subsequent increase in O3 concentration. The improved mechanism simulation results show a wider range and higher concentration of high-O3, with more pronounced downwind diffusion, reflecting the promoting effect of VOCs on O3 formation. In contrast, the original mechanism significantly reduces O3 near point sources due to the titration effect of NO, but lacks photochemical reactions involving VOCs, making it difficult for O3 to regenerate downwind, resulting in simulation results showing only a decrease in O3 concentration without a subsequent increase. This indicates that the original mechanism cannot accurately reflect the actual formation and distribution characteristics of O3 in the atmosphere and underestimates the contribution of point sources to regional O3 pollution. Detailed Implementation

[0072] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0073] The terminology used in one or more embodiments of this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the one or more embodiments of this specification. The singular forms “a,” “described,” and “the” as used in one or more embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in one or more embodiments of this specification refers to and includes any or all possible combinations of one or more associated listed items.

[0074] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this specification, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this specification, and similarly, second may also be referred to as first. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0075] The present invention will now be described in further detail with reference to the accompanying drawings:

[0076] This invention provides a method for improving the chemical mechanism of an air quality model at the park scale to enhance ozone simulation capabilities:

[0077] Azzi et al. used a series of VOC mixtures and smog chamber data with different VOC / NOx ratios to identify the most important reactions in the photochemical smog formation process, thus formulating the GRS mechanism. The GRS mechanism is an extension of the NOx / O3 photochemical steady-state equilibrium mechanism, taking into account reactive organic components. The advantages of the GRS scheme lie in its versatility and simplicity, allowing it to be applied to different atmospheric chemistry models. This mechanism reduces the number of reactions that need to be calculated by selecting and combining key reactions; it uses parameterization to describe certain complex chemical processes, reducing computational complexity; and it is applicable to different meteorological conditions and geographical regions, enabling global application.

[0078] The scheme obtained by GRS uses only seven reactions to represent thousands of reactions involving VOCs-NOx-O3. These seven reactions are:

[0079] ROC+hv→RP+ROC

[0080] RP + NO → NO2

[0081] NO2 + hv → NO + O3

[0082] NO + O3 → NO2

[0083] RP+RP→RP

[0084] RP+NO2→SGN

[0085] RP+NO2→SNGN

[0086] Compared to the GRSM mechanism in the AERMOD model, the GRS mechanism adds the following substances: ROC (reactive organic compounds), RP (reactive radical pool), SGN (stable gaseous nitrogen products), and SNGN (stable non-gaseous nitrogen products). These components are groups of substances with similar chemical structures or reactivity. The third and fourth reactions mentioned above represent the exact chemical mechanisms, while the remaining reactions are only approximate representations of their corresponding chemical reactions. The first reaction represents the photolysis of all ROCs. This is the most important reaction because it is considered the "starting point" of the smog formation process and the source of RP. The second reaction is fast and is the first fate of RP, converting NO to NO2. The generated NO2 can be photolyzed to generate O3 and regenerate NO through the third reaction. In the fourth reaction, the generated O3 can react with NO to generate NO2. The fifth reaction represents the second sink of RP, while the sixth and seventh reactions are other sinks that produce inactive nitrogen compounds.

[0087] The reaction rates of each substance are:

[0088] R1 = k1[ROC]

[0089] R2 = k2[RP][NO]

[0090] R3 = k3[NO2]

[0091] R4 = k4[NO][O3]

[0092] R5 = k5[RP][RP]

[0093] R6 = k6[RP][NO2]

[0094] R7 = k7[RP][NO2]

[0095] The form of a differential equation is:

[0096]

[0097] In the formula, [RP] is the concentration of RP, [NO] is the concentration of NO, [NO2] is the concentration of NO2, [ROC] is the concentration of ROC, and [O3] is the concentration of O3.

[0098] In the above formula, k represents the chemical reaction rate constant, and the calculation formula is:

[0099]

[0100] k2 = 5482e 242 / T (ppm -1 min -1 )

[0101]

[0102] k4 = 2643e -1370 / T (ppm -1 min -1 )

[0103] k5 = 10000 (ppm) -1 min -1 )

[0104] k6 = 120 (ppm) -1 min -1 )

[0105] k7 = 120 (ppm) -1 min -1 )

[0106] In the formula: k1 and k5-k7 are taken from the study of Azzi et al., k2 and k4 are taken from the study of Valencia et al., and k3 is taken from the study of Rojas et al. T represents temperature, x represents solar zenith angle, and TSR represents total solar radiation. Let f(T) represent the average activity coefficient of the ROC species mixture, and f(T) represent a function of temperature. The calculation formula is as follows:

[0107]

[0108] γ = 4.7

[0109] In the above formula, a i The value represents the activity coefficient of different ROC species, taken from the study of Valencia et al., where T represents temperature.

[0110] The reaction rate of the ROC component is zero, meaning that the component is conserved. This assumption is valid if the simulation timescale is much smaller than the lifetime of the ROC (i.e., days to months). The lifetime of free radicals is typically much shorter than that of other species. Therefore, it is assumed that the production and consumption rates of free radicals are in equilibrium, and the free radical pool (RP) is in a quasi-steady state. This simplifies the transport equation for RP to a quadratic equation with only one positive solution. The concentration of RP can then be calculated using the following formula:

[0111] k5[RP] 2 +(k2[NO]+(k6+k7)[NO2])[RP]-k1[ROC]=0

[0112] This invention updates the GRSM mechanism in the AERMOD (Air Quality Model for Parks) to the aforementioned GRS scheme. Compared to the original GRSM mechanism, it considers the influence of VOCs on O3 and NOx concentrations and updates the reaction rate equations. A fifth-order Runge-Kutta scheme with an adaptive time step is used to solve the rate equations, thereby obtaining the concentrations of O3, NO2, and NO after each receptor chemical reaction. The chemical mechanism, including VOCs, provides a more complete description of the O3 formation process and better reflects the real atmospheric environment, which is of great significance for accurately simulating and forecasting O3 concentrations.

[0113] This invention introduces VOCs into the GRSM mechanism of the AERMOD (Air Quality Model for Parks) at the park scale, expanding the GRSM mechanism from two chemical reactions involving only NO, NO2, and O3 to seven chemical reactions involving VOCs, thus more closely resembling the real atmospheric environment.

[0114] In addition, this invention updates the original mechanism of NO2 photolysis rate by directly incorporating the solar altitude angle into the formula, which can reflect the influence of the sun's position change on the photolysis rate throughout the day. By using a piecewise function and fitting it separately for different solar altitude angle intervals, it can more accurately reflect the variation law of photolysis rate in each interval.

[0115] To better illustrate the technical effects of the present invention, the present invention provides the following specific embodiments to illustrate the above technical process:

[0116] Example 1: A method for improving the chemical mechanism of an air quality model at the park scale to enhance ozone simulation capabilities:

[0117] Currently, this invention has incorporated VOCs into the GRSM chemical mechanism of the AERMOD (Air Quality Model for Industrial Parks) at the industrial park scale. To evaluate its simulation effect, a typical case study was selected. Considering factors such as the test area, emission sources, and topography, Zhengzhou City, Henan Province, was chosen as the target area for the case study simulation. The industrial park's core enterprise is Zhengzhou Xinli Power Co., Ltd. This company is located in Zhongyuan District, Zhengzhou City, Henan Province (central latitude and longitude 113.59°E, 34.77°N) and primarily engages in thermal power generation.

[0118] This invention simulates the air pollution process around the Zhengzhou Xinli Power Co., Ltd. thermal power plant from July 6th to 14th, 2019. It employs a GRSM mechanism incorporating VOCs, considering the effects of organic compounds such as propane, higher alkanes, ethylene, higher olefins, formaldehyde, high-formaldehyde compounds, ketones, benzene, monoalkylbenzenes, dialkylbenzenes, and trialkylbenzenes, thus making the AERMOD model's simulation results for O3 concentration more accurate. Specifically, AERMAP is used as a terrain preprocessor to process the terrain data of point sources and receivers, while MMIF is used as the model's meteorological preprocessor to convert the output of the forecast meteorological model WRF into parameters and formats directly input into the AERMOD model. Simultaneously, the simulation results of the regional air quality model CMAQ, subtracting point source emissions from the Zhengzhou thermal power plant, are used to provide background concentrations for AERMOD.

[0119] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the chemical mechanism of an air quality model at the park scale to enhance ozone simulation capabilities, characterized in that, Includes the following steps: The active organic compound ROC undergoes a photolysis reaction to yield the free radical pool RP; NO is oxidized to NO2 via a free radical pool RP; NO2 is photolyzed to produce NO and O3. O3 and NO react to produce NO2; The free radical pool RP is consumed by reaction. The free radical pool RP reacts with NO2 to produce inactive nitrogen compounds.

2. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 1, characterized in that: The inactive nitrogen compounds include gaseous nitrogen product SGN and non-gaseous nitrogen product SNGN.

3. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 2, characterized in that: The reaction formula for the ROC photolysis of the active organic compound is: ROC+hv →RP+ROC (1) The reaction formula for oxidizing NO to NO2 via the free radical pool RP is: RP + NO → NO2 (2) The reaction equation for the photolysis of NO2 is: NO2 + hv → NO + O3 (3) The reaction equation for the reaction between O3 and NO is: NO + O3 → NO2 (4) The reaction formula for the reaction consumption of the free radical pool RP is: RP+RP →RP (5) The reaction formula for generating gaseous nitrogen product SGN is: RP + NO2 → SGN (6) The reaction formula for generating the non-gaseous nitrogen product SNGN is: RP+NO2 →SNGN (7).

4. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 3, characterized in that: The reaction rates of reactions (1) to (7) are: R1 = k1[ROC] R2 = k2[RP][NO] R3 = k3[NO2] R4 = k4[NO][O3] R5 = k5[RP][RP] R6 = k6[RP][NO2] R7 = k7[RP][NO2] where: R1 to R7 are the reaction rates of reaction formulas (1) to (7), k1 to k7 are the chemical reaction rate constants of reaction formulas (1) to (7), [RP] is the concentration of RP, [NO] is the concentration of NO, [NO2] is the concentration of NO2, [ROC] is the concentration of ROC, and [O3] is the concentration of O3.

5. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 4, characterized in that: R1 to R7 can be written in the form of differential equations as follows: In the formula: k1~k7 are the chemical reaction rate constants of reaction formulas (1) to (7), respectively.

6. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 5, characterized in that: The formulas for calculating k1 to k7 are: k2=5482e 242 / T (ppm -1 min -1 ) k4=2643e -1370 / T (ppm) -1 minutes -1 ) k5=10000(ppm -1 min -1 ) k6=120(ppm -1 min -1 ) k7=120(ppm -1 my -1 ) In the formula: T represents temperature, x represents the solar zenith angle, and TSR represents total solar radiation. denoted by , where represents the average activity coefficient of the ROC species mixture, and f(T) represents the temperature function.

7. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 6, characterized in that: The average activity coefficient of the ROC species mixture The formula for calculating the temperature function f(T) is as follows: γ = 4.7 In the formula: a i The value represents the activity coefficient of different ROC species, and T represents the temperature.

8. The method for improving the chemical mechanism of campus-scale air quality models to enhance ozone simulation capabilities according to claim 7, characterized in that: The concentration of RP is calculated using the following formula: k5[RP] 2 +(k2[NO]+(k6+k7)[NO2])[RP]-k1[ROC]=0 In the formula: [RP] is the concentration of RP, [NO] is the concentration of NO, [NO2] is the concentration of NO2, [ROC] is the concentration of ROC, and [O3] is the concentration of O3.

Images