CN113654950A - Plant-related behavior simulation in chemical environmental system simulation - Google Patents

Plant-related behavior simulation in chemical environmental system simulation Download PDF

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CN113654950A
CN113654950A CN202110397243.3A CN202110397243A CN113654950A CN 113654950 A CN113654950 A CN 113654950A CN 202110397243 A CN202110397243 A CN 202110397243A CN 113654950 A CN113654950 A CN 113654950A
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孟耀斌
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Abstract

The invention relates to plant-related behavior simulation in chemical substance environmental system simulation coupled with hydrological processes. In the simulation method, the atmospheric concentration of a chemical substance and the stratum corneum concentration of the chemical substance form a mass transfer fugacity pair, and the atmospheric concentration of the chemical substance and the sap concentration of the chemical substance form a mass transfer fugacity pair; the concentration of the chemical substance stratum corneum and the concentration of the chemical substance sap form a mass transfer fugacity pair. The method comprises a chemical leaf surface migration simulation between the plant and the atmosphere, wherein gaseous chemicals migrate and diffuse between the atmosphere and the mesophyll through the stomatal channels and between the atmosphere and the mesophyll through the stratum corneum. The simulation method provided by the invention has the simulation capability of dynamically adapting the chemical substance migration among the atmosphere, the vegetation and the soil to the meteorological process and the seasonal periodic physiological characteristics of plants and embodying the dynamic change of the exposure concentration in a multi-environment medium.

Description

Plant-related behavior simulation in chemical environmental system simulation
Technical Field
The invention relates to the fields of chemical substance environmental risk analysis, environmental risk assessment, environmental risk management and the like, in particular to a simulation method of chemical substances in environmental exposure in the fields.
Background
After various chemical substances are manufactured, human life is enriched, and meanwhile, environmental risks brought by the chemical substances can possibly harm public health and various lives in an ecological system, so that the chemical substances become one of core contents of development and environmental safety control of chemical industry at home and abroad. Chemical environmental risk analysis is the basis for environmental risk assessment and environmental risk management; the Environmental risk needs to predict the Concentration of chemical substances in various Environmental media, such as soil, water, vegetation, and the atmosphere, which is called the Predicted Environmental Concentration (PEC) of chemical substances in a certain Environmental medium, and the Concentration is compared with the damage threshold of chemical substances to living beings, and whether chemical substances form a risk to a certain living being is determined according to whether the PEC exceeds the threshold. Therefore, if dynamic changes of the environmental concentration of the chemical substances, such as daily concentration (or average concentration every 96h, every 7d, every 30d, etc.) fluctuation of the chemical substances in the environmental medium within one year (even multiple years), can be simulated, the threshold value of toxic effect of the chemical substances under different exposure time periods can be flexibly matched, and thus a foundation is laid for more accurately evaluating the environmental risk of the chemical substances.
The current chemical exposure assessment model estimates the concentration in the environmental medium "under long-term stable conditions" based on the "cautious principle" (precautionary principle) in risk management, using this concentration as the predicted environmental concentration PEC; in match, toxicity test results are used to estimate the Predicted No-Effect Concentration (PNEC) in an environmental medium (such as surface water), and then the risk is judged according to whether PEC/PNEC is greater than 1. In fact, the toxic effects of chemical species on organisms are related to the exposure time and the specific life stage of the organism, and the threshold concentration of chemical species for hazard varies significantly with exposure time, the life stage of the organism, e.g., seasonally, so that methods for setting PNEC and PEC under long-term stability conditions are subject to a conservative bias (over-conservative bias) while complying with the conservative principle. The risk management of overly conservative chemicals can compromise the development of the chemical industry, particularly the high-end chemical industry, and can have a significant adverse impact on the materials industry, equipment manufacturing, etc. downstream of the industry chain. If the annual dynamic change of the concentration of the chemical substance in different environment media can be reasonably estimated, the fluctuation rule of the concentration of the environment media can be examined day by day and is contrasted and analyzed with the biological life history, so that accurate environment risk analysis can be realized, and excessive conservative bias in chemical substance environment risk assessment is avoided.
The current mainstream environment exposure estimation method comprises an fugacity theory, a mainstream exposure model based on the fugacity balance theory and a chemical substance space distribution model based on the hydrological flow space-time difference, and as can be seen from the basic logic of chemical substance risk assessment and the development context of the chemical substance exposure model, the environment exposure model taking the homogeneous and steady natural environment hypothesis and the balance distribution as the core and leading the chemical substances to be classified as the basic characteristics begins to change to attach importance to the influence of the dynamic process of the natural environment such as the hydrological process and the like on the chemical substance environment exposure.
The chemical substance exposure simulation model coupled with the hydrological process has the following basic characteristics:
A) generally, watershed (watershed) is used as a space range for simulation and prediction; if the region (region) exceeds the scope of the drainage basin, the drainage basins involved need to be simulated respectively and then proper space synthesis is carried out;
B) dividing the interior of the river basin into a plurality of sub river basins (sub) according to the terrain and the confluence characteristics; each sub-basin is further divided into a plurality of basic hydrological units (such as Hydrological Response Units (HRUs)) according to the terrain gradient, the soil property and the ground surface coverage;
C) the spatial differentiation of chemical substances in surface environment media such as soil, surface water and sediment is expressed by hydrologic spatial units, such as the concentration in the soil surface layer and subsurface layer of a certain HRU, the concentration in river water in a certain sub corresponding river reach and the concentration in the sediment of the river reach, the concentration in crop leaves on a certain HRU and the like;
D) the chemical substance is subjected to corresponding chemical reaction (such as degradation and possible generation) in each environmental medium on each space unit, and the reaction is influenced by the environmental conditions such as temperature, humidity, illumination and the like of the corresponding space unit;
E) chemical substances migrate with the hydrological process: the chemical substances in the atmosphere enter soil and water along with precipitation; chemical substances in soil, water and leaf surfaces enter the atmosphere along with evaporation; chemical substances on the surface layer of the soil enter the river reach along with surface runoff and soil erosion; chemical substances that flow down and up the surface layer (lower layer) of the soil with infiltration and capillary migration to the lower layer (upper layer) of the soil; soil moisture chemicals are taken into the plant along with the plant and enter the plant roots and are transported to the leaf surface; the chemical substances suspended in the water body enter the mud from the water or enter the water from the mud along with the sedimentation of suspended particles and the re-suspension of the surface layer of the bottom mud; and the like;
F) the migration of chemical substances among the space units is the space migration of water (surface runoff and soil erosion, interflow, river reach connection, confluence, barrage storage and discharge, irrigation water regulation).
In the chemical substance environmental system exposure model coupled with the hydrological process, vegetation is relatively independent and is used as a new environmental medium to be juxtaposed with the atmosphere, soil, water (sediment) and the like. However, not only the behavior pattern of the chemical substances in the vegetation but also the migration and transformation of the chemical substances between the vegetation and other environmental media (atmosphere, soil) should be considered.
Therefore, there is a need to construct a model of chemical migration and transformation between vegetation and other environmental media to more realistically implement the simulation and prediction functions of chemical environmental system exposure models coupled with hydrological processes.
Disclosure of Invention
The simulation method for the behavior of the chemical substances in the plants coupled with the hydrological process, disclosed by the invention, is used for dynamically predicting the concentration of the chemical substances in each medium in an environmental system comprising the media such as soil, water, atmosphere, vegetation and the like in an area or watershed space range. The term "environment" as used herein includes the category of "ecological environment" and also includes the category of "environmental health" in the course of health due to contamination with chemicals in the environment. By "chemical" herein is meant a chemical that can migrate with air, water streams, and particulate matter in the environment.
For plants, the leaf surface is the cuticle (cuticle) on the outer layer of the mesophyll tissue, which comprises the matrix (cuticle matrix), wax (cuticle wax) scattered thereon, i.e., outside, and stomata. The stratum corneum is both a barrier between the atmosphere and mesophyll tissue and a medium for holding organic chemicals; stomata (stomata) is a channel that directly communicates between the mesophyll and the atmosphere. In this sense, the stratum corneum is the channel for mass transfer between the atmosphere outside the leaf surface and the tissue inside the leaf, and this channel is formed by pores connected in parallel to the stratum corneum. By setting the vegetation phase chemical morphology for the behavior simulation of chemicals, the design of chemical migration models in vegetation can be simplified. In the method, a canopy stratum corneum (indicated by cut subscript and referred to as a canopy stratum phase) is independently used as a new environmental medium plant module, and the function of the canopy stratum corneum is to fill a temporary storage carrier required by indirect migration between the atmosphere and a soil environmental medium in a chemical substance environmental system exposure model coupled with a hydrological process; when the plant module is dynamically simulated with the integration of the environment media such as the atmosphere, the soil, the water body and the like, the nonlinear and procedural characteristics such as 'accumulation-falling' of the migration between the atmosphere and the soil can be expressed, so that the uncertainty of the exposure concentration in the soil and the atmosphere and the indirectly related uncertainty of the total exposure concentration of the water body can be well expressed. By taking into account the persistence of the particulate matter in the stratum corneum, deviations introduced by neglecting this persistence can be reduced, particularly in seasons with less precipitation, and this persistence consideration of the present invention can significantly improve simulation accuracy.
The method considers that the chemical substance concentration in the mesophyll can be approximated by the sap concentration C due to the migration of water between the chemical substance and sap in the mesophyll and the migration of the chemical substancesapReplacing; and the chemical substances in the leaf epidermal cutin are used as the cutin concentration CcutCharacterization, it is related to the root concentration CrootAnd sap concentration CsapTogether constitute the vegetation phase chemical concentration.
By the above definition, it is possible to establish a more accurate exposure model for evaluating the exposure risk of the chemical substance in the environment.
According to one aspect of the present invention there is provided a method of modelling the behaviour of a chemical in a plant coupled to a hydrological process, the method comprising simulation of chemical leaf surface migration between the plant and the atmosphere, the simulation of leaf surface migration further comprising
Gas chemical substances migrate and diffuse between the atmosphere and the mesophyll through the pore channels; and
gaseous chemicals migrate and diffuse between the atmosphere and the mesophyll through the stratum corneum.
Preferably, in the simulation, the atmospheric concentration of the chemical substance and the stratum corneum concentration of the chemical substance form a mass transfer fugacity pair, and the atmospheric concentration of the chemical substance and the sap concentration of the chemical substance form a mass transfer fugacity pair; the concentration of the chemical substance stratum corneum and the concentration of the chemical substance sap form a mass transfer fugacity pair.
Preferably, the leaf surface migration simulation further comprises the leaf surface cuticle layer receiving an input flux of atmospheric particulate laden chemical.
Preferably, if the amount of chemical substance M held by the canopyfoliageThe amount of chemical substance in the leaf surface cuticle, M, the amount of chemical substance held in the canopyfoliageDaily change of (A) and (B)foliageExpressed as:
Figure BDA0003019010600000041
wherein
Figure BDA0003019010600000042
Representing the input flux of chemicals carried by the canopy trapped particulate matter to the stratum corneum phase,
Figure BDA0003019010600000043
and
Figure BDA0003019010600000044
respectively the diffusion mass transfer flux of the gaseous chemical substance in the atmosphere and the cuticle phase and the diffusion mass transfer flux of the cuticle phase and the mesophyll tissue, and the unit is mol/m2。
Preferably, the simulation of the migration of the plant leaf surface further comprises the dynamic process of the loading, shedding and elution of the atmospheric particulates on the leaf surface, which is characterized by the amount of the particulates loaded by the vegetation canopy per unit ground surface projection area.
Preferably, the method further comprises
Migration of water-soluble chemical substances between the plant roots and the soil; and
the migration of chemical uptake by the plant roots to the parts above the roots, wherein the wool migration flux of the chemical uptake by the plant from the soil and into the transpiration stream is the product of the transpiration stream flow rate and the transpiration stream chemical concentration.
Preferably, ifDefining the chemical mass of the vegetation dry branches as MbiomassShowing that the daily change of chemical quality of the dry branches of the vegetation is Delta MbiomassIncluding chemicals that enter the mesophyll and sap from the atmosphere and chemicals that are ingested by the soil,
Figure BDA0003019010600000045
wherein
Figure BDA0003019010600000046
Is the mass transfer flux of the gaseous chemical substance and the dissolved chemical substance in the mesophyll tissue through the pores,
Figure BDA0003019010600000047
the diffusion mass transfer flux of the cuticle to the mesophyll tissue,
Figure BDA0003019010600000048
the net migration flux of chemical substances from the soil into the transpiration stream is in mol/m2。
Preferably, the method further comprises characterizing the degradation and storage of the chemical substance within the plant by diffusion of the chemical substance from the sap to other tissues of the plant.
Preferably, the simulation method comprises
Acquiring geographic data, vegetation surface coverage data, meteorological field data and chemical substance distribution data of a researched area by taking a hydrological basic unit as spatial precision;
and (3) determining the behavior of chemical substances in the plants according to the precipitation, the atmospheric dry and wet sedimentation flux and the ground surface coverage type.
Preferably, the method for simulating the behavior of the chemical substances in the plants under the framework of the daily precision discretization simulation comprises the following steps
Obtaining the concentration of the chemical substances in the plants in the previous day and the concentration of the chemical substances in the air in the current day to calculate the concentration of the chemical substances in the leaves;
obtaining the water-soluble concentration of chemical substances in soil, and calculating the concentration of the chemical substances in the tree roots;
the higher of the two concentrations was determined as the sap concentration in the plant at the day.
According to the simulation method, the canopy stratum corneum is independent to serve as a new environmental medium plant module, and a temporary storage carrier required by indirect migration between the atmosphere and a soil environmental medium in a chemical substance environmental system exposure model coupled with a hydrological process is provided; through setting up the bearing capacity of vegetation canopy to atmospheric particulates, can embody the "effect of keeping in" of vegetation in the migration in-process between atmospheric particulates and soil, avoided in the traditional atmospheric diffusion model particulate matter always directly subside the bias that this settlement of input soil brought, more rationally simulated the process that atmospheric particulates carried chemical entering plant leaf portion, when plant leaf portion is edible part, this also provides support for latent crowd's diet exposes and health risk aassessment. The simulation method provided by the invention has the simulation capability of dynamically adapting the chemical substance migration among the atmosphere, the vegetation and the soil to the meteorological process and the seasonal periodic physiological characteristics of plants and embodying the dynamic change of the exposure concentration in a multi-environment medium.
Drawings
The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings:
FIG. 1 shows a schematic view of a blade configuration according to an embodiment of the invention;
FIG. 2 shows a computational flow diagram of a process for the migration of plants to the atmosphere and soil according to an embodiment of the present invention;
FIG. 3 shows a flow chart of a reconciliation calculation of plant leaf intake with root intake according to an embodiment of the present invention;
FIG. 4 illustrates a watershed map according to an example of the invention;
FIG. 5 illustrates spatial information input layers according to an example of the invention;
FIG. 6 illustrates an input point source location graph according to an example of the invention;
FIG. 7 shows a basin population density profile according to an example of the invention;
fig. 8 shows a chemical vegetation behavior simulation timing diagram according to an example of the present invention.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
The invention provides a migration and transformation process model of a vegetation module in a chemical substance environmental system exposure model coupled with a hydrological process and a calculation implementation method, wherein in the preferred embodiment, "chemical substances" refer to organic substances which can exist in environmental media such as air (containing particles therein), water (containing sediment and suspended solids), soil (containing soil moisture and soil solid particles) and the like at normal temperature. The method mainly comprises the steps of (1) setting a scheme of vegetation phase chemical substance form and a related process calculation framework; (2) secondly, designing a chemical substance migration model between the leaf surface and the atmosphere; (3) thirdly, migration of chemical substances between the roots and the soil; (4) sixthly, designing a calculation scheme of vegetation correlation process under a daily precision discretization simulation framework.
Setting scheme of vegetation phase chemical substance form and related process calculation framework
Positioning of vegetation phase in environmental system
The chemical substance environment system exposure model of the coupling hydrological process is divided according to three levels of a basin, a sub-basin and a basic hydrological unit according to the spatial division of hydrological calculation. As a preferred embodiment of the present invention, a vegetation phase (also referred to herein as vegetation or plant) as a vegetation module in the model also takes basic hydrologic cells as spatial computational units, i.e., spatial precision; correspondingly, the time precision is consistent with the hydrologic calculation precision, and preferably the day precision. The vegetation is definitely attached to the soil space division, chemical substance transfer in a horizontal direction for example between space units does not exist, and only vertical migration exists, namely migration between atmosphere and vegetation and soil. For simplicity, the present invention does not relate to the process of chemical migration and transformation in plants in water.
In the invention, the plant module has the function of filling a temporary storage carrier required by indirect migration between atmosphere and soil environment medium in a chemical substance environment system exposure model coupled with a hydrological process; when the plant module is dynamically simulated with the integration of the environment media such as the atmosphere, the soil, the water body and the like, the nonlinear and procedural characteristics such as 'accumulation-falling' of the migration between the atmosphere and the soil can be expressed, so that the uncertainty of the exposure concentration in the soil and the atmosphere and the uncertainty of the total exposure concentration of the water body related to the brief introduction can be well expressed.
Chemical concentration design in vegetation phase
Chemical substance migration between plants and the atmosphere and soil almost always occurs along with water migration of plants, and the physiological regulation of water migration of plants also affects chemical substance migration. Therefore, it is an intuitive advantage to simulate the migration pathway of chemical substances according to the pathway of plant water exchange with the atmosphere and soil. In a preferred embodiment of the invention, the concentration of the chemical substances in the vegetation is defined, for example, in terms of three key parts: respectively root (root) concentration CrootLeaf (canopy) concentration CfoliageAnd sap (sap) concentration Csap. The sap is the sap formed by transporting water in the plant, and is not limited to the plant of the tree type. Root concentration CrootDirectly correlating chemical migration between the root and the soil; concentration of sap CsapExpresses the migration of chemical substances accompanied when the water exchange is carried out between the canopy and the root; leaf concentration CfoliageDirectly linked to chemical migration between the intra-leaf and extra-canopy atmospheres.
Existing leaf concentration CfoliageThe definition of (a) is ambiguous because it takes into account that the exterior of the leaf, due to its geometry, mechanical properties and chemical properties of the cuticle, can accept settling of atmospheric particulates and carry them over a period of time; leaf concentration CfoliageIt is not sufficient to clearly characterize the equilibrium relationship between the leaf surface and the mesophyll of the chemical species on the leaf-borne particulate matter. The invention is disclosedTo facilitate the transport of water between the chemicals and sap in the mesophyll and to accompany the migration of the chemicals, the chemical concentration in the mesophyll can be approximated by the sap concentration CsapReplacing; and the chemical substances in the leaf epidermal cutin are used as the cutin concentration CcutCharacterization, it is related to the root concentration CrootAnd sap concentration CsapTogether constitute the vegetation phase chemical concentration.
The stratum corneum, independently, is of great significance as an environmental mediator in the simulation of chemical behavior in plants coupled to hydrological processes. Because seasonal variations in canopy, particularly annual crops or deciduous forests, etc., that result in concentrated large biomass inputs to the ground during a particular season, also means concentrated inputs of chemicals to the ground that, if coupled with variable meteorological hydrologic scenarios, can result in a rather unfavorable chemical exposure migration, it is the purpose of the present invention to attempt to establish an exposure model for a more accurate risk assessment service.
Thus, the term "sap" as used herein refers to both the various water solutions that migrate within a plant, both to the transpiration upflow (xylem sap), to the transport downflow of photosynthesis products (phloem sap), and to the solution within the canopy mesophyll; concentration of sap CsapRefers to the concentration of chemicals within the three parts of the juice. According to the invention, the chemical substance concentration among various sap is simplified into a concentration level by the definition. This definition greatly simplifies the dependence on specific plant physiological characteristics in the chemical substance environmental system exposure model coupled with the hydrological process, and trades the convenience of chemical substance migration calculation in plants at the cost of sacrificing the accuracy of the concentration inside the plants.
Second, design of model for chemical substance migration between leaf surface and atmosphere
The chemical substance environmental system exposure model coupled with the hydrological process can quickly complete calculation on the premise of ensuring the prediction accuracy of the exposed concentration of the surface, such as soil and water environmental media.
The key points of the horizontal migration diffusion simplification algorithm comprise: neglecting terrain influence, introducing no wind direction parameter, approximately expressing the plane geometric relation between sub-drainage basins by argument and distance, calculating plane diffusion parameter by mean value of gas field parameter at two positions of discharging sub-drainage basin (SO) and receiving sub-drainage basin (RE), and simplifying calculation of diffusion outflow drainage basin boundary part of sub-drainage basin located at drainage basin boundary. The rationality and benefit of these simplified algorithm points are as follows:
modeling of (A) leaf surface structure
The leaf surface is the stratum corneum (cuticle) on the outer layer of the mesophyll tissue, which comprises a matrix (particulate matrix) and wax (particulate wax) scattered thereon (outside). The stratum corneum is both a barrier between the atmosphere and the mesophyll tissue and a medium for the containment of organic chemicals. The leaf surface structure in this method is expressed as shown in FIG. 1.
In fig. 1, the Leaf profile is shown as being divided into the approximate geometrical relationship of the cuticle, which in turn is divided into the outer waxy layer wax and the cuticle matrix below the waxy layer wax; also shown is stomastomata, which is a channel that directly communicates mesophyll with the atmosphere. In this sense, the stratum corneum, which includes both the matrix and the wax, is a channel and a barrier to mass transfer between the atmosphere outside the leaf surface and the tissues inside the leaf, and this channel and barrier are formed by pores in parallel with the stratum corneum.
As shown in fig. 1, the leaf tables can receive atmospheric settled Particulate Matter (PM) that forms a migration between the particulate laden chemicals and the stratum corneum during the duration of the stratum corneum, i.e., not yet fallen or eluted by the precipitation. The persistence of the particles in the stratum corneum is complicated, but neglecting persistence may introduce larger deviations, which is particularly undesirable in seasons with less precipitation. Therefore, in the method, the stratum corneum (indicated by cut subscript and referred to as coronary phase) is independently used as a new environmental medium.
Chemical substance migration simulation strategy between (II) leaf surface and atmosphere
After addition of the stratum corneum as an environmental medium, atmospheric chemicals sink to the leaf surface and are refined into a migration process that targets both the leaf surface stratum corneum and the inner leaf tissue (mesophyll). Corresponding, atmosphereConcentration CairRespectively corresponding to the stratum corneum concentration CcutAnd sap concentration CsapForming mass transfer fugacity pairs; at the same time, the stratum corneum concentration CcutAnd sap concentration CsapAnd also form mass transfer fugacity pairs. The independent stratum corneum concentration C is clearly shown in FIG. 1cutAnd sap concentration CsapAnd mass transfer between the two, CcutAnd CairC, CsapAnd CairThe mass transfer between the two. Due to strong regulation by meteorological conditions, plant physiology, etc., Cair、CcutAnd CsapThe mass transfer between the three is not suitable for setting directly according to equilibrium distribution, especially the concentration C in plantscutAnd sap concentration CsapThis is especially true in the presence of large uncertainties. Namely, when the simulation is carried out in a daily precision discretization mode, the increase and the decrease of the three must be calculated in a mass transfer flux mode.
Migration of chemicals in the canopy involves six input-output pathways: the method comprises the steps of firstly, inputting atmospheric air into the leaf (atmospheric dry sedimentation, sedimentation indicated by a downward arrow) ↓, secondly, outputting chemical substances in tree liquid in the leaf to the atmospheric air (entering the atmospheric air accompanied by transpiration and indicated by an upward arrow) ×, thirdly, inputting water drops on the leaf surface into the leaf (atmospheric wet sedimentation and interception by a canopy) ↓), fourthly, inputting stratum corneum formed by intercepting particulate matter PM on the leaf surface, fifthly, diffusing mass transfer ↓ofthe stratum corneum into the leaf, and finally, diffusing and outputting the chemical substances in the leaf to the stratum corneum. Wherein, the third step is a model for the settlement of the atmosphere vegetation to the earth surface included in the traditional atmosphere migration European model.
In the method, the following main calculation strategy is formed for the role of highlighting the leaf surface cuticle as a medium between the leaf external atmosphere and the leaf internal sap:
(1) migration and diffusion of gaseous chemicals between the atmosphere and mesophyll (short-circuiting the stratum corneum) through pore channels
The driving force for mass transfer is the loss degree difference in terms of atmospheric concentration CairThe concentration of mesophyll tissue, that is, the concentration of sap CsapRepresents;
the mass transfer resistance includes the lost motion resistance RaDiffusion resistance R of blade surface boundary layer (laminar layer)bAir hole diffusion resistance Rstomata. Wherein R isbAnd RstomataAre calculated according to the resistance in plant transpiration of water vapor.
(2) Migration and diffusion of gaseous chemicals through the stratum corneum between the atmosphere and mesophyll
The driving force for mass transfer is the loss degree difference in terms of atmospheric concentration CairWith the concentration C in the stratum corneumcutRepresents;
the mass transfer resistance includes the lost motion resistance RaDiffusion resistance R of blade surface boundary layer (laminar layer)bStratum corneum diffusion resistance Rcut. Wherein R isbThe settings are as above. The stratum corneum diffusion resistance is proportional to the stratum corneum thickness δ.
(3) Chemical mass transfer in the retained water drops following precipitation of rain drops on the leaf surface
During the precipitation process, raindrops may form droplets on the leaf surface within a short time, but as the precipitation continues, the droplets can quickly drop (elution effect of the precipitation), and the dropped raindrops form wet settlement on soil and do not form migration with the leaf surface. However, the canopy has a certain water holding capacity (canopy), raindrops which are deposited to the surface of the leaves in the weak rainfall form the migration of the water holding capacity of the atmospheric canopy, and the water holding capacity of the canopy is in the migration diffusion with chemical substances in the leaves. In the method, the chemical substances dissolved in the water-holding capacity of the canopy layer and the concentration of the gaseous chemical substances are considered together, and the enhancement effect of the leaf surface dry sedimentation process of the gaseous substances is considered.
This approach is based on the following considerations: the canopy water retention exists in the evaporation process intermittently in the precipitation process, the mass transfer area between the liquid drop and the leaf surface cuticle is small, the mass transfer area between the liquid drop and the air is relatively larger, and the evaporation process is vigorous compared with the diffusion process into the leaf; the water-soluble chemical substances are volatilized into gaseous molecules along with the evaporation of the liquid drops, so that the contribution of mass transfer channels between the leaf surface liquid drops and the atmosphere and the mesophyll or the horny layer is difficult to distinguish in daily precision, and the necessity is not large.
(4) The atmospheric particulates carry chemical substances redistributed in the stratum corneum after dry and wet sedimentation to the leaf surface
After atmospheric particulates (e.g., PM2.5) are captured by the leaf surface, the chemicals carried by the particulates diffuse into the stratum corneum, see fig. 1, despite dry and wet settling. Since the thickness of the stratum corneum is itself between less than 1 μm and 10 μm, PM forms deep admixtures in the stratum corneum. The PM-carried chemical diffuses into the stratum corneum. Within daily accuracy, it is reasonable to arrange for such particulate matter to be thoroughly mixed with the stratum corneum (distributed after mixing in a system where the stratum corneum and PM together form).
Wherein, atmospheric particulates which are settled to the leaf surface in wet settlement form an increment part of the leaf surface stratum corneum carrying particulates only by deducting the particulate parts which are eluted to the ground by the precipitation, and form a migration diffusion source between the atmospheric particulates and the leaf surface stratum corneum together with the leaf surface already carrying the particulates.
In summary, the migration process between the chemical substances in the atmosphere and the vegetation canopy includes three bidirectional migration channels: gaseous chemicals are transported through the pores and diffused in parallel through the stratum corneum, directly inputting captured particles into the stratum corneum. Accordingly, if the amount of chemical substance (M) held by the canopy is definedfoliage) The amount of chemical in the cuticle of the leaf, MfoliageDaily change of (Δ M)foliage) Can be expressed as a combination of two mass transfer fluxes:
Figure BDA0003019010600000101
wherein
Figure BDA0003019010600000102
Represents the input flux (mol/m) of chemical substances carried by the captured particles in the canopy to the stratum corneum phase2)，
Figure BDA0003019010600000103
And
Figure BDA0003019010600000104
respectively diffusion mass transfer flux (outer flux) of gaseous chemical substances in the atmosphere and stratum corneum phase and leavesDiffusion mass transfer flux (inside flux) (mol/m) of meat tissue (labeled sap)2) See fig. 1.
Chemical mass (in M) of vegetation trunks (parts excluding leaves and roots) is definedbiomassRepresents), then MbiomassDaily change of (Δ M)biomass) Including chemicals that enter the mesophyll and sap from the atmosphere, but also chemicals that are ingested by the soil (see below: fourthly, designing a model for partial migration of the chemical substance ingested by the root to the root):
Figure BDA0003019010600000105
wherein
Figure BDA0003019010600000106
The mass transfer flux (mol/m) of the gaseous chemical substance and the dissolved chemical substance in the mesophyll tissue through the pores2)，
Figure BDA0003019010600000107
Diffusion mass transfer flux (inside flux) (mol/m) for stratum corneum towards mesophyll tissue (labeled sap)2)，
Figure BDA0003019010600000108
Net migration flux (mol/m) of chemical substances for uptake from the soil and into the transpiration stream2)。
(III) chemical substance diffusion migration flux calculation method through air holes
Figure BDA0003019010600000109
The comprehensive expression of the downward flux of the mass transfer of the gaseous chemical substance and the dissolved chemical substance in the mesophyll tissue through the air holes and the upward flux of the dissolved chemical substance in the mesophyll tissue which is volatilized into the atmosphere through the air holes is realized. The part of the raindrop retention leaf surface dissolved with chemical substances and the gaseous dry settlement part are both regarded as gaseous states to be equivalent to the external atmospheric concentration
Figure BDA0003019010600000111
The equilibrium gaseous concentration C representing the concentration of mesophyll tissueLeafForming mass transfer kinetics (see figure 1).
Equivalent external atmospheric concentration
Figure BDA0003019010600000112
Calculated as follows:
Figure BDA0003019010600000113
wherein F represents the sedimentation flux (mol/(m)2d) The superscripts air, pep denote dry and wet sedimentation of the chemical, respectively, CairRepresents the concentration (mol/m) of gaseous chemical substances in the atmosphere3)。
Figure BDA0003019010600000114
The resistance of mass transfer can be set in comparison with the dry settlement of gaseous substances by the lost motion resistance RaDiffusion resistance R of blade surface boundary layer (laminar layer)bAir hole diffusion resistance RstomataAnd (4) forming.
Figure BDA0003019010600000115
R in the above formulabCan be set with reference to water vapor, RstomataTypical values can be found in the literature: when the water vapor transpiration is calculated in a general ecological hydrological model, the effects of solar radiation, water deficit and plant conditions are considered, and R is set by means of air hole resistance in the modelsstomataNot only feasible, but also more reasonable. The specific value-taking method is omitted.
(IV) method for calculating diffusion migration flux of chemical substances in atmosphere and mesophyll to stratum corneum
Shown in formula (1)
Figure BDA0003019010600000116
And
Figure BDA0003019010600000117
the flux of the diffusion mass transfer of gaseous chemical substances in the atmosphere and chemical substances in the mesophyll (in the same sap in the method) to the cuticle of the leaf surface is shown in fig. 1. The stratum corneum diffuses very slowly and cannot use the balance hypothesis, and the fugacity difference of the contents of chemical substances in the atmosphere, mesophyll and stratum corneum is calculated. For this purpose, the concentration of the chemical substance in the stratum corneum is defined, the fugacity of which is expressed as the equilibrium gaseous concentration, then
Figure BDA0003019010600000118
And
Figure BDA0003019010600000119
can be calculated as follows:
Figure BDA00030190106000001110
Figure BDA00030190106000001111
in the above formula CairIs the concentration (mol/m) of gaseous chemical substances in the atmosphere3)，CcutChemical concentration in the stratum corneum (mol/kg cuticle), CsapIs the concentration of chemical substances in the stratum corneum (mol/m)3) (ii) a Fu denotes the fugacity, having a dimension of atmospheric concentration (mol/m)3) The subscript thereon is as defined for C; kcut-aStratum corneum-air distribution constant (m) for chemical substances3/kg)，KwaIs the water-gas partition constant (-) of chemical substance, the former can be determined by the partition constant K of stratum corneum matrix and airMX-aAnd the distribution coefficient K of cuticle wax and gaseous chemicalsWX-aAnd determining the mixing ratio of the substrate and the wax in the horny layer; the latter is the basic physicochemical properties of a chemical substance. R in the above formulacuticleFor the resistance to diffusion in the stratum corneum, the stratum corneum resistance (or conductance) of the plant can be studiedResearching the result; deltaouterThe fraction of the outer layer thickness in the stratum corneum for which mass transfer with air and with mesophyll occurs is virtually divided, the general deltaouterShould be 0.5.
(V) calculation method for receiving input flux of atmospheric particle carried chemical substances by leaf surface cuticle
In the formula (1)
Figure BDA0003019010600000121
The input flux to the canopy stratum corneum is shown as a result of chemicals carried on the foliar-outward trapped particulate matter accompanying the particulate matter being trapped by the stratum corneum. After the atmospheric particulates are captured by the leaf surface, a ternary distribution system of particulate matter-stratum corneum matrix-stratum corneum waxy (PM-MX-WX) on the leaf surface is formed. The volume ratio of wax in the cuticle in the literature is utilized
Figure BDA0003019010600000122
Then the proportion of the chemical substances in the PM-MX-WX system distributed to the particulate matter PM, the cuticle matrix MX and the cuticle waxy WX is respectively as follows:
Figure BDA0003019010600000123
Figure BDA0003019010600000124
Figure BDA0003019010600000125
in the three formulas, KPM-aIs the distribution coefficient, K, of particulate matter PM to gaseous chemical substancesMX-aIs the partition coefficient, K, of the stratum corneum matrix to gaseous chemicalsWX-aDistribution coefficient of cuticle wax and gaseous chemicals, PMcanopyAnd mfoliaRespectively representing the amount of particulate matter retained by the canopy and the mass of the stratum corneum (including CM and CW) per projected area of the ground (g/m)2)。
KPM-aAccording to the partition coefficient K between the particles and the chemical substancepTreatment, provided or estimated by literature reports. KMX-aThe experimental results in the literature can be used as well. Good fitting quality (r) was obtained after fitting 62 chemicals with solvation parameters as in 1(Platts and Abraham,2000)20.994) of KMX-aEstimation formula:
Figure BDA0003019010600000131
solvation parameters in formula (la):
Figure BDA0003019010600000132
as a result of the polarization parameters,
Figure BDA0003019010600000133
is the acidity of the hydrogen bond,
Figure BDA0003019010600000134
to hydrogen bond basicity, logL16Distribution coefficient logarithm of hexadecane, VxIs McGowan volume, R2Excess molar refractive index (molar excess fraction).
Based on estimated KMX-aCan estimate K empiricallyWX-a
KWX-a＝0.1*KMX-a (11)
Therefore, complete distribution simulation of the PM-MX-WX ternary system in the vegetation canopy can be completed by the formulas (7) to (11) and the basic model; thereby calculating the chemical substance concentration C in the leaf surface cuticlecutAnd the concentration C of the chemical substance on the equilibrated leaf surface captured particulate matterfolia,PM。
(VI) calculation method of dynamic process of loading, falling and elution of atmospheric particulates on leaf surface
The vegetation canopy continuously receives atmospheric particulate matter settlement to form dynamic changes of particulate matter carried by the canopy. Definition of PMcanopyVegetation crown being unit ground surface projection areaThe amount of particulate matter carried by the layer (g/m)2ground area). Since the canopy cannot carry particulate matter indefinitely, in PMcanopyWhen the bearing capacity of the vegetation is exceeded, the vegetation canopy can not accept the settlement of the particles any more, and the physical manifestation is that the particles held by the canopy fall off and enter the soil. To express this process, the method sets the maximum fine particulate bearing capacity variable of the vegetation canopy: maximum PM bearing capacity per Leaf Area Index (LAI)
Figure BDA0003019010600000135
That is, as LAI increases, the bearing capacity of the canopy to PM increases linearly. Here, the
Figure BDA0003019010600000136
The particle sizes of the particles with the capacity of carrying chemical substances are respectively set; for simplicity, only the particle size grouping PM2.5 may be considered.
On the other hand, regardless of PMcanopyIf the bearing capacity of the vegetation is exceeded, PM is generated only when the vegetation meets precipitation forming scouring elutioncanopyWill be accompanied by a reduction in the elution of particulate matter from the leaf surface. According to the current scientific study, we set the precipitation elution efficiency to be expressed as follows:
y＝a(1-exp(-bx)) (11)
wherein a and b are parameters which are different according to the vegetation types, x is the accumulated precipitation (mm) in the precipitation process, and y is the accumulated elution ratio (-) of the leaf surface PM. Research shows that a is about 0.5-0.7; b is about 0.17 to 0.26mm-1。
In the dynamic simulation, the PM on the canopy is logically set to the calculation logic as follows:
Figure BDA0003019010600000141
in the above formula,. DELTA.PMcanopyShows the dry and wet sedimentation amounts (g/m) of the granules in one day2ground area), Pcp is the amount of precipitation (mm) on the day, LAI is the leaf area index (-), WcanopyAnd
Figure BDA0003019010600000142
the existing water storage amount of the canopy and the maximum water storage amount of the canopy are expressed by equivalent precipitation (mm).
Correspondingly, the calculation logic for setting the ground soil to receive PM settlement is as follows:
Figure BDA0003019010600000143
the calculation logic shown by the formula defines the distribution relation of the atmospheric particulate matter PM settlement between the vegetation and the soil:
as long as effective precipitation occurs, dry and wet settlement in the day falls to the soil; moreover, the particulate matter PM on the surface of the leaves can be partially eluted to the ground according to the precipitation and the elution rule;
(II) no precipitation or only trace precipitation (not exceeding the water holding capacity of the tree crown) occurs, as long as the accumulated PM exceeds the PM bearing capacity of the tree crown, only the PM corresponding to the maximum bearing capacity of the leaf surface particulate matter PM is reserved, and the exceeded part falls off to the ground;
and (III) no precipitation or only trace precipitation (not exceeding the water holding capacity of the tree crown) occurs, and the dry and wet sedimentary PM falls on the leaf surface completely as long as the accumulated PM does not exceed the PM bearing capacity of the tree crown.
The settlement of PM received by the soil from the canopy can be obtained according to the logic calculation, and the flux is multiplied by the amount of the chemical substances on the PM distributed to the ternary balance system of the day-leaf table PM-MX-WX (distribution ratio shown in the formula (7) in the specification) in the simulation process, so that the input of the chemical substances from the canopy shedding value surface can be obtained
Figure BDA0003019010600000144
Figure BDA0003019010600000145
Thirdly, designing a model for chemical substance migration between roots and soil
The roots of the plants take up chemicals from the soil and form a concentration C at the rootsroot. Method for producing a composite materialIt is assumed that only water-soluble chemicals in the soil can migrate towards the roots of the vegetation. Due to regulation and control of plant physiology, although the migration and intake processes of chemical substances in soil to vegetation root systems are researched a lot, a dynamic process model is not established; the method also abandons the approach of establishing the intake kinetics, but in line with scientific research literature (such as the soilpusveg model (Terzaghi et al, 2017, Terzaghi et al, 2015)), adopts a simplified treatment mode: the chemical Concentration C of the plant roots was calculated by means of Root Concentration Factor (RCF)root. RCF is defined as follows:
Figure BDA0003019010600000151
wherein [ Cd,s]Is the concentration (mol/m) of soluble chemical substances in soil3 soil water)，CrootIs the concentration of the chemical substance in the soluble state in the roots of the plants (mol/kg WetWeight root).
The RCF value can be determined by the basic physicochemical parameter logK of the chemical substanceowEstimation (Briggs et al, 1982):
Figure BDA0003019010600000152
in the method, the migration of chemical substances in the plants to the soil through roots is not considered, namely, the plants are regarded as pure chemical substance 'enrichments'. This assumption is approximately reasonable: the migration of chemicals in the soil to the roots is a result of the transport of soil moisture to the plants (transpiration), and the water output of plants to the soil is generally considered to be much weaker than the transpiration and is expressed as a small amount of secretions at the roots, so the output of plants to the soil is weak, if any, due to the soilbpusveg model (Terzaghi et al, 2017, Terzaghi et al, 2015)) assuming that the downward migration flow (phylomam sap flow) in the plants is 1/20 of the transpiration upward flow (xylomam sap flow). Thus, the chemical migration flux between the soil and the plant
Figure BDA0003019010600000153
Is the one-way uptake flux (mol/m) of soil → plants2) The logic is calculated as follows:
Figure BDA0003019010600000154
i.e., root chemical concentration if calculated as RCF
Figure BDA0003019010600000155
Chemical concentration of root over the previous day
Figure BDA0003019010600000156
Then accept the calculation
Figure BDA0003019010600000157
The root concentration of the current day is determined by the product of the root concentration of the current day and the wet weight of the root
Figure BDA0003019010600000158
The amount of the chemical substances contained in the roots of the current day is larger than the amount of the chemical substances contained in the roots of the previous day
Figure BDA0003019010600000159
The difference of (A) was taken as the flux from soil uptake into the roots on the day
Figure BDA00030190106000001510
If it is
Figure BDA00030190106000001511
The concentration of the chemical substances in the root part is not more than the concentration of the chemical substances in the root part on the previous day
Figure BDA00030190106000001512
Neglecting the migration from the soil to the roots on the day: (
Figure BDA00030190106000001513
Is zero).
As aboveCalculated flux of chemical migration between soil and plant
Figure BDA00030190106000001514
Apparently only the result of the equilibrium distribution between the roots and the soil solution, the rationale is that the dynamic course of the uptake of soil solution into the roots can be balanced in a solar-precision simulation, and numerous experiments (e.g. (Briggs et al, 1982)) prove that this balance can indeed be reached within one day.
Fourth, model design of chemical substance intake in root part migrating to upper part of root
As a result of the migration of water by Transpiration during the migration of chemical substances in the soil to the roots of plants, the chemical substances, after entering the roots, continue to migrate to the upper parts of the plants and to the canopy leaves along with the Transpiration Stream (transfer Stream); of course, while some portion of the chemical species is stored in the root (root concentration C is determined by RCF, as described above)root) And another part of the chemical substance diffuses out of the transpiration stream into the branches of the plant.
The concentration C of chemical substances in the transpiration upflow (the plant with xylem is generally xylem sap) under the action of plant transpirationTS_Sap(mol/m3) The concentration of the soil solution chemicals and the Transpiration flow enrichment Factor (TSCF, dimensionless) can be calculated as:
Figure BDA0003019010600000161
the TSCF can be determined by the basic physicochemical parameter logK of chemical substancesowAnd (6) estimating. The estimated formulae (19) to (20)) of TSCF are available from scientific literature (Briggs et al, 1982) and (Hsu et al, 1990) as follows:
Figure BDA0003019010600000162
Figure BDA0003019010600000163
in the method, the mean value of the two estimations is adopted as TSCF.
As previously mentioned, the method does not take into account the chemical flux of the plant into the soil, and therefore the chemical wool migration flux of the plant from the soil and into the transpiration stream
Figure BDA0003019010600000164
The transpiration flow rate (m is expressed by the water depth per unit area of transpiration) and the transpiration chemical concentration CTS_sapThe product of:
Figure BDA0003019010600000165
in the formula, ETaThe actual transpiration (mm) is calculated from the basic process of ecological hydrology, and is omitted here.
It should be noted that the above (four, model design of the migration of the chemical uptake into the root to the upper part of the root) independently of this expresses C as an enrichment factor (expression of equilibrium state)rootAnd CTS_sapPossible contradictions at two concentrations: the uptake of chemicals into the roots, whether enriched at the roots or continuing to be transported up the plant, is accompanied by a transpiration stream. The TSCF values obtained in the laboratory were actually the result of satisfying both root enrichment and "sap" enrichment. If the transpiration stream is not vigorous within a day or there is not enough chemical in the soil to enrich the plant, the chemicals that enter the plant with the transpiration stream cannot simultaneously satisfy both the root enrichment calculated by the RCF equation (16)) and the transpiration stream enrichment calculated by the TSCF equations (19), (20)).
In this case, the method is configured to prioritize root enrichment: first, the uptake flux of root chemical is calculated according to RCF and root biomass
Figure BDA0003019010600000171
(formula (17)). It is clear that,
Figure BDA0003019010600000172
is carried into the roots of the plants with the transpiration stream. Therefore, should be made with
Figure BDA0003019010600000173
With a daily transpiration flow ETaWith the concentration [ C ] in the transpiration streamTS_sap]Comparing the products to see if the latter are sufficiently supporting
Figure BDA0003019010600000174
Only when
Figure BDA0003019010600000175
Calculated by equation (17)
Figure BDA0003019010600000176
The effect is obtained, otherwise,
Figure BDA0003019010600000177
can only press ETa[CTS_sap]The modification, namely formula (17), should be modified as follows:
Figure BDA0003019010600000178
meanwhile, the formula (21) is also limited to
Figure BDA0003019010600000179
This is true, i.e., equation (21) should also be modified:
Figure BDA00030190106000001710
fifth, simplified calculation scheme of degradation and storage process inside plants
It is possible that chemical substances are degraded in plants, generally, degradation requires oxygen or dissolved oxygen, so that the method only allows degradation in Sap (Sap), and the degradation kinetics are first order reaction kinetics, with a degradation rate constant kdegCan be set according to literature values (d)-1). Although the chemical substances stored in other plant tissues can be diffused and enter the sap again, the method only considers the diffusion (storage process) of the sap into other plant tissues and does not consider the reverse process for the moment, and the storage process can be also approximated by first-order reaction kinetics, and the storage rate constant is kstoreCan be set according to literature values (d)-1) When no literature value can be referred to, parameter calibration should be considered. So that the concentration of chemical substances in the sap [ C ]sap]Should be corrected as follows:
Figure BDA00030190106000001711
during daily precision discretization, a rough estimation value [ C ] of the concentration of chemical substances in sap is obtained through other migration calculationssap，0]Then, the correction is performed according to the following formula:
Figure BDA0003019010600000181
sixthly, design of calculation scheme of vegetation related process under daily precision discretization simulation framework
The chemical substance environmental system exposure model coupled with the hydrological process is used for carrying out discretization simulation on day-night day-to-day changes of chemical substances in the environmental system including atmosphere, water, soil and vegetation on the soil by taking a hydrological basic unit (HRU) as space precision. As mentioned in the second part of the design of the model for chemical migration between the leaf surface and the atmosphere, the characteristics of a plurality of processes of chemical substances related to vegetation are yet to be further scientifically researched and discovered, based on the prior knowledge, the invention does not pay attention to the chemical concentration in the tissues such as the average meaning or branches and trunks in the plants, but defines the stratum corneum concentration C according to the parts where chemical substances migrate between vegetation and the environmental media such as the atmosphere and soilcutRoot concentration CrootConcentration of sap CsapThe three concentrations serve as vegetation phase chemical concentrations of interest in a chemical environmental system exposure model coupled with the hydrological process.
In the simulation process of a certain day, vegetation related calculation is developed based on the current state concentrations of the forms of various chemical substances in the atmosphere and the soil while the modules of the atmosphere, the soil, the water body and the like are simulated (see the above-mentioned (second) chemical substance migration simulation strategy between the leaf surface and the atmosphere). In relation to the precipitation situation (presence or absence of precipitation, and precipitation size) on the same day, the overall calculation scheme is shown in fig. 2.
The leaf part is based on the concentration C of the sap because of the uptake from the atmosphere or the volatilization to the atmospheresapCalculation of, and CsapAt the same time, the equilibrium concentration in the root transpiration flow is calculated, the two are different, but based on the design of the method, CsapShould be uniform, so two paths are needed to calculate CsapAnd (4) blending. In the method CsapThe harmonic calculation strategy of (2) is shown in fig. 3.
The key points of the vegetation-related calculation schemes and sequences shown in fig. 2 and 3 are as follows:
the bearing capacity of the leaf surface to the particulate matters settled by the atmosphere has the non-stable dynamic characteristics of dynamic accumulation, rain washing and excess capacity shedding, and the washing, shedding and the like are determined by plant characteristics and rainfall characteristics;
part of atmospheric particulates without vegetation in the hydrological basic unit directly subsides to soil, so that the dynamic change of chemical substance migration among atmosphere, soil and vegetation is different every day along with the periods of seasonal vegetation growth and withering and the like, and the influence of the vegetation is reflected by year-round or year-round simulation;
sap concentration C in plantssapAdopting the high value of the numerical value obtained by the leaf intake and the numerical value obtained by the root intake;
for grain crops, deciduous plants and the like, the canopy leaf part withers and falls in autumn and winter, and the input of short-time large-flux chemical substances to soil is formed;
in grain crops, annual plants and the like, chemical substances contained in roots of the crops are classified into soil and mixed among different layers of the soil along with operations such as turning over the soil after harvesting and the like.
The design and sequence of the above calculation scheme has the following advantages:
set up the bearing capacity of vegetation canopy to atmospheric particulates, fully embody the "temporary storage" effect of vegetation in the migration process between atmospheric particulates and soil:
the bias brought by the setting that the particles in the atmosphere always directly settle and are input into the soil in the traditional atmospheric diffusion model is avoided;
the process that atmospheric particulates carry chemical substances into the plant leaves is reasonably simulated, and when the plant leaves are edible parts, the process also provides support for potential crowd dietary exposure and health risk assessment.
The chemical substance intake of the root firstly updates the concentration of the chemical substance in the root according to the enrichment coefficient of the root and calculates the daily increase of the chemical substance contained in the root; in combination with the flow rate of the transpiration stream over a day, if the daily transpiration stream inputs no more than the daily increase in root chemicals, then no further intake of the transpiration stream is considered (only the chemical intake of the leaves is considered): the advantage of this strategy is that it is preferable to have the chemicals ingested by the roots stay in the roots. Since the root chemicals return to the soil along with the end of the plant life cycle, the arrangement herein will preferably avoid or relatively reduce the bias of underestimation of chemical concentration in the soil caused by plant enrichment, consistent with the "cautious principles".
Taking the greater concentration of the falling sap concentration absorbed by leaves and the transpiration sap concentration absorbed by roots as the strategy of the sap concentration; because the method does not consider discharging chemical substances to the soil from roots, the method can overestimate the concentration of the chemical substances in the sap on the whole, thereby overestimating the migration of the soil to the atmosphere and the degradation or storage in the vegetation; however, given the preference of the present method to concentrate the chemical species in the roots (see above) and the uncertainty of the plant-related process, the bias developed here should fall into a tolerable category.
In summary, the design of the vegetation-related process calculation scheme shown in fig. 2 and 3 is an optimization scheme that, under the condition that the existing vegetation-and-chemical-related research is not sufficient, considering the requirement that the chemical substance environmental system exposure model coupled with the hydrological process mainly aims at simulating the exposure concentration in non-living environmental media such as soil and water, and reasonably expresses the migration dynamics of chemical substances among the atmosphere, vegetation and soil as much as possible, and the vegetation-related process calculation scheme has the simulation capability of adapting to the seasonal periodic physiological characteristics of meteorological processes and plants and embodying the dynamic variation of the exposure concentration in multi-environmental media.
Examples of the invention
1. Study area selection
The present example identified the study area as the upstream drainage basin of the liuyang river in the south of hu, which was located in the east of the Changsha city in the south of hu and was bordered by the province of Jiangxi, and which had an area of about 1990 square kilometers, as shown in FIGS. 4 and 5. The area is obviously affected by global warming and shows that extreme weather events are increased, precipitation is abnormal in flood season and drought and waterlogging are frequent. The upstream basin of the Liuyang river belongs to subtropical seasonal windy humid climate, the average temperature in many years is 17.5 ℃, the average precipitation in many years is 1550mm, and the precipitation is mainly concentrated in 3-7 months, which accounts for about 65% of the total precipitation in all years. The river basin is mainly divided into a brook river basin and a brook river basin, and the two rivers meet at the double river mouths.
2. Inputting data
1) Geographic information data and meteorological field data
The model constructed by the simulation method of the invention needs data such as a research area DEM, land cover, soil classification and meteorological hydrology, and specific data parameters are shown in Table 1. The soil classification data is from the latest data of Nanjing soil institute, the land utilization data is from the latest data, the weather station data is from China Meteorological science data sharing service network, the rainfall station data and the hydrological station data are from Hunan hydrological Bureau, and the reservoir data is obtained by field investigation. Of these data, the data of the weather station, the rainfall station, and the hydrological station are day by day from 1/month in 2008 to 12/month in 2016 and 31/day.
Table 1 data required for modeling of up-flow of the Liuyang river
Figure BDA0003019010600000201
2) Target chemical property data
The target chemical substance in the test is, for example, an O-xylene-based substance (indicated by OXY, and in the figure, by O-xylene), which is volatile and facilitates the characterization of the effect of concentration simulation in the atmosphere. Design attribute data for OXY is shown in table 2.
TABLE 2 target chemical Property data
Figure BDA0003019010600000211
3) Pollution source input
In this test, the environmental background concentration of the target chemical substance was not set, the chemical substance input in the environmental medium was derived from the surface source input, which is derived from population density and discharge coefficient, and the point source input was classified into sewage treatment plant discharge, air point source discharge, and landfill discharge, as shown in tables 3 to 6. Point source input locations are shown in fig. 6 and population density distributions are shown in fig. 7.
TABLE 3 table of emission coefficients of surface sources
Figure BDA0003019010600000212
Table 4 atmospheric point source discharge meter for pollutants
Figure BDA0003019010600000213
TABLE 5 Point-Source discharge Meter for Industrial wastewater
Figure BDA0003019010600000214
Table 6 refuse landfill site source discharge table
Figure BDA0003019010600000221
3. Results of operation and simulation
The example is based on a swat (soil and Water Assessment tool) model and is improved by referring to the simulation method analyzed above, and the improved model is used for simulating a time sequence chart of chemical substance vegetation behaviors based on the conditions to verify the simulation method of the chemical substance behaviors in the plants coupled with the hydrological process.
The vegetation simulation firstly simulates the growth of vegetation, vegetation grows out in spring and summer, and can take over target chemical substances attached to the surfaces of particles in atmospheric sedimentation and enrich the target chemical substances from roots, vegetation declines in autumn and winter, and chemical substances are not stored. Fig. 8 shows a vegetation behavior simulation timing diagram for 500# HRU near sub-basin 1.
After the test target chemical substance OXY (shown as O-xylene in the figure) is subjected to atmospheric dry settlement, the test target chemical substance OXY is carried by the vegetation canopy, and the concentration of OXY in the atmosphere is reduced and the concentration of OXY in the vegetation canopy is increased. The specific action process is as follows: after the particles in the atmosphere are settled to the leaf surface, the particles are firstly carried by the leaf surface, and distribution of OXY to the leaf part cuticle (divided into stroma and wax) is generated on the leaf surface; then, OXY in the stratum corneum and gaseous OXY in the atmosphere diffuse into the mesophyll through the pores on the leaf surface, respectively. Then, OXY in the mesophyll migrates to the branches of the plant along with the transport of water in the plant body. When the leaf surface particulate matter exceeds the leaf surface bearing capacity or large precipitation occurs, OXY in the leaf surface particulate matter falls into soil along with falling or elution of the particulate matter, so that the concentration of OXY in the soil is increased.
The absorption and enrichment of OXY in the soil by the roots can cause the concentration of OXY in the soil to be reduced slightly, and part of OXY absorbed by the roots can migrate to the branches of the plants when the concentration of OXY in the soil environment is too low (in this example, lower than about 3X 10)-7g/m3) When the root was not enriched efficiently, it was shown that the OXY content of the root was zero. In autumn and winter, the vegetation leaves will wither and the OXY (including OXY contained in the cuticle carrying the particles and leaves) of the leaves will fall into the soil, causing soil OThe XY concentration has small rising fluctuation; in this example, since the concentration of OXY in soil is much greater than that of OXY in plants, fluctuations of OXY in soil caused by withering of leaves in autumn and winter are not obvious and are easily affected by other factors.
As can be seen from the simulation results shown in fig. 8, under the condition that the research on vegetation and chemical substances is not sufficient at present, in consideration of the requirement that the chemical substance environmental system exposure model coupled with the hydrological process mainly aims at simulating the exposure concentration in non-living environmental media such as soil and water, the invention provides an optimization scheme for reasonably expressing the migration dynamics of chemical substances among atmosphere, vegetation and soil as much as possible, and the scheme has the simulation capability of adapting to the meteorological process and the seasonal periodic physiological characteristics of plants and embodying the dynamic variation of the exposure concentration in multi-environmental media.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims (10)

1. A method for simulating the behavior of chemical substances in plants in a coupled hydrological process is characterized in that the atmospheric concentration of the chemical substances and the stratum corneum concentration of the chemical substances form a mass transfer fugacity pair in the simulation, and the atmospheric concentration of the chemical substances and the sap concentration of the chemical substances form a mass transfer fugacity pair; the concentration of the chemical substance stratum corneum and the concentration of the chemical substance sap form a mass transfer fugacity pair.
2. The method of claim 1, wherein the method comprises a simulation of chemical substance leaf surface migration between the plant and the atmosphere, the simulation further comprising
Gas chemical substances migrate and diffuse between the atmosphere and the mesophyll through the pore channels; and
gaseous chemicals migrate and diffuse between the atmosphere and the mesophyll through the stratum corneum.
3. The method of claim 1, wherein said simulation of leaf surface migration further comprises the leaf surface cuticle receiving migration and diffusion of atmospheric particulate laden chemicals to the cuticle.
4. The method of claim 3 for modeling the behavior of a chemical in a plant coupled with a hydrological process,
if the amount of chemical substance M held by the canopyfoliageThe amount of chemical substance in the leaf surface cuticle, M, the amount of chemical substance held in the canopyfoliageDaily change of (A) and (B)foliageExpressed as:
Figure FDA0003019010590000011
wherein
Figure FDA0003019010590000012
Representing the input flux of chemicals carried by the canopy trapped particulate matter to the stratum corneum phase,
Figure FDA0003019010590000013
and
Figure FDA0003019010590000014
respectively the diffusion mass transfer flux of the gaseous chemical substance in the atmosphere and the cuticle phase and the diffusion mass transfer flux of the cuticle phase and the mesophyll tissue, and the unit is mol/m2。
5. The method of claim 1, wherein the simulation of the migration of the foliage of the plant further comprises characterizing the dynamic process of loading and shedding, elution and elution of atmospheric particulates at the foliage by the amount of particulates carried by a canopy of vegetation per unit area of the projected surface.
6. The method of claim 1, further comprising simulating the behavior of a chemical in a plant coupled to a hydrological process
Migration of water-soluble chemical substances between the plant roots and the soil; and
the migration of chemical uptake by the plant roots to the parts above the roots, wherein the wool migration flux of the chemical uptake by the plant from the soil and into the transpiration stream is the product of the transpiration stream flow rate and the transpiration stream chemical concentration.
7. The method of claim 6, wherein M is the amount of chemical species in the vegetation trunks if defined asbiomassShowing that the daily change of chemical quality of the dry branches of the vegetation is Delta MbiomassIncluding chemicals that enter the mesophyll and sap from the atmosphere and chemicals that are ingested by the soil,
Figure FDA0003019010590000021
wherein
Figure FDA0003019010590000022
Is the mass transfer flux of the gaseous chemical substance and the dissolved chemical substance in the mesophyll tissue through the pores,
Figure FDA0003019010590000023
the diffusion mass transfer flux of the cuticle to the mesophyll tissue,
Figure FDA0003019010590000024
the net migration flux of chemical substances from the soil into the transpiration stream is in mol/m2。
8. The method of claim 1, further comprising characterizing the degradation and storage of the chemical species within the plant by diffusion of the chemical species from sap into other tissues of the plant.
9. The method of claim 1, wherein the method comprises simulating the behavior of a chemical in a plant coupled to a hydrological process
Acquiring geographic data, vegetation surface coverage data, meteorological field data and chemical substance distribution data of a researched area by taking a hydrological basic unit as spatial precision;
and (3) determining the behavior of chemical substances in the plants according to the precipitation, the atmospheric dry and wet sedimentation flux and the ground surface coverage type.
10. The method of claim 1, wherein the method of modeling the behavior of a chemical substance in a plant under a framework of precision-discretized daily simulation comprises
Obtaining the concentration of the chemical substances in the plants in the previous day and the concentration of the chemical substances in the air in the current day to calculate the concentration of the chemical substances in the leaves;
obtaining the water-soluble concentration of chemical substances in soil, and calculating the concentration of the chemical substances in the tree roots;
the higher of the two concentrations was determined as the sap concentration in the plant at the day.
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