Greta Jimenez
There are various methods to simulate pollution, particularly air and water pollution. For instance, the QUAL2K model is a one-dimensional river and stream water quality model that can simulate the migration and transformation of conventional pollutants. It was used to predict the water quality of the Hongqi River, a tributary in the Taihu Lake Basin, China. The calibrated QUAL2K model calculated the water environmental capacities of CODCr NH3-N, TN, and TP, which were used to determine the necessary pollution load reduction rates to meet water quality objectives. Meanwhile, for air pollution, the CALPUFF model was used to simulate the atmospheric dispersion of air pollutants in Zibo City, China, and estimate the atmospheric environmental capacity of SO2, NO(x), and PM10. Additionally, Gaussian dispersion models or computational fluid dynamics (CFD) models can be employed to simulate air quality, especially in urban areas. Furthermore, indoor air quality simulation software packages like IAQX help advanced users analyze the impact of pollutant sources and sinks, ventilation, and air cleaners.
| Characteristics | Values |
|---|---|
| Modelling air pollution in urban areas | Can be done using CFD codes |
| Modelling air quality in a small area | Use a Lagrangian/Gaussian model like US EPA's AERMOD or ADMS |
| Modelling air quality with many emission sources | Use an Eulerian model like CMAQ |
| Indoor air quality simulation software | IAQX by US EPA |
| Water pollution simulation model | QUAL2K |
| Air pollution simulation in Zibo City, China | CALPUFF model |
| Air pollution in Northeast China | Land use regression |
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What You'll Learn
Using Gaussian dispersion models for urban areas
Gaussian dispersion models, also known as Gaussian plume models, are often used to simulate air pollution in urban areas. These models are based on the Gaussian equation, which describes the dispersion of a pollutant plume. The equation takes into account the height of the pollutant plume's emission source and the effect of ground reflection.
One advantage of using Gaussian dispersion models is that they can be used to simulate the dispersion of pollution from line sources such as roads, which is particularly relevant for urban areas with dense road networks. For example, the Gaussian puff model CALPUFF has been used to simulate NO2 concentrations in Montreal, Canada, taking into account emissions from over 40,000 roads.
However, Gaussian models have limitations when applied to urban areas. They tend to underestimate pollutant concentrations compared to other models, such as street canyon models, and do not account for the turbulence and drag induced by buildings. Additionally, they may not be suitable for simulating the dispersion of pollution at street intersections or over long distances within complex urban environments.
To overcome some of these limitations, Gaussian dispersion models can be coupled with other models or data. For example, the EPISODE urban dispersion model combines an Eulerian 3D grid model with embedded sub-grid dispersion models, including a Gaussian plume model, to simulate pollution dispersion from line and point sources. The EPISODE model also considers atmospheric processes such as advection and diffusion, as well as NO2 photochemistry.
In summary, Gaussian dispersion models are useful for simulating air pollution in urban areas, particularly for dispersing road transport emissions. However, they may not capture all the complexities of urban environments, and combining them with other models or data can improve their accuracy and applicability.
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US EPA's AERMOD or ADMS for single pollution sources
US EPAs AERMOD and ADMS are both Gaussian dispersion models used to simulate air pollution from single sources. They are particularly useful for modelling the impact of industrial sources on air quality.
AERMOD, or AMS/EPA Regulatory Model, is a steady-state plume model that incorporates air dispersion based on planetary boundary layer turbulence structure and scaling concepts. It can be used to model both surface and elevated sources, as well as simple and complex terrain. AERMOD includes three modules: a steady-state dispersion model, a meteorological data preprocessor (AERMET), and a terrain preprocessor (AERMAP). AERMOD's relative simplicity, quick setup, acceptable accuracy, and wide applicability in different atmospheric conditions are some of its advantages.
ADMS, or Advanced Dispersion Modeling System, is another Gaussian dispersion model that evaluates industrial impacts on air quality. It incorporates building effects, complex terrain, coastlines, variations in surface roughness, dry and wet deposition, chemistry schemes, short-term releases, and the calculation of fluctuations in concentration on short timescales. ADMS also allows for the prediction of condensed plume visibility and radioactive decay, including γ-ray dose.
When choosing between AERMOD and ADMS, it is important to consider the availability of meteorological data. In developing countries, for example, accurate and sequential meteorological data may be limited, which can constrain the use of these models. Additionally, the location of industries can also impact the availability of data, as most plants and industrial facilities are constructed outside of large cities where meteorological sites are scarce.
Both AERMOD and ADMS have their advantages and are widely used for simulating air pollution from single sources. However, it is important to note that the choice between the two models depends on specific requirements and data availability.
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Windows-based indoor air quality simulation
Several tools and methods are available for simulating pollution, including indoor air quality simulations. Windows-based indoor air quality (IAQ) simulation software packages have been developed to address the need for accurate estimations of inhalation exposure to indoor air pollutants, considering that individuals spend a significant amount of time indoors.
One such software package is the Simulation Tool Kit for Indoor Air Quality and Inhalation Exposure, or STKi. STKi is a Microsoft Windows-based IAQ simulation package that includes a general-purpose simulation program and stand-alone, special-purpose programs. The general-purpose program enables multi-zone, multi-pollutant simulations and supports gas-phase chemical reactions. It offers a vast collection of models for sources, sinks, and air filters/cleaners, making it versatile for a wide range of indoor air pollution scenarios. The special-purpose programs implement fundamental models that enhance performance over statistical models.
STKi complements existing IAQ simulation packages and is geared towards advanced users. It has undergone a small-scale beta test and quality assurance review. Other Windows-based IAQ simulation programs include RISK (Sparks, 1996), MEDB-IAQ (Zhang et al., 1999), and MCCEM (Koontz and Wilkes, 1999).
When simulating air pollution, it is important to consider the scale of the area being modelled. For instance, mesoscale models may face challenges when applied to very small areas. In such cases, Gaussian dispersion models or computational fluid dynamics (CFD) models coupled with aerosol and/or chemistry processes may be more suitable. CFD models can require significant preparation time for geometrical modelling but offer a high degree of realism.
Additionally, the choice of model depends on the specific objectives of the simulation. If the focus is on measuring the impact of a single pollution source, a Lagrangian/Gaussian model like US EPA's AERMOD or ADMS may be appropriate. On the other hand, if comparisons across multiple emission sources are needed, an Eulerian model like CMAQ is recommended, although this requires meticulous work on emissions processing and meteorology.
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QUAL2K model for river and stream water quality
QUAL2K is a one-dimensional river and stream water quality model that computes water levels, horizontal and vertical velocities, temperature, and 21 other water quality parameters (such as dissolved oxygen, nutrients, organic matter, algae, pH, the carbonate cycle, bacteria, and dissolved and suspended solids). The model has been widely applied to stratified surface water systems such as lakes, reservoirs, and estuaries.
The QUAL2K model has been developed over 40 years by the United States Environmental Protection Authority. It has been used by a growing number of analysts and entities in the private sector. The model includes steady-state hydraulics, non-uniform steady flow, and diel heat budget/water-quality kinetics. A one-dimensional vertical lake model is designed to compute seasonal trends of water quality in stratified lakes. There is also a one-dimensional lateral benthic algae model that computes the distribution of biomass in rivers according to temperature, attenuated light, and available nutrients.
The QUAL2K model has been applied to River Kabini in India, which receives agricultural runoff and untreated domestic waste. The model was calibrated and validated for various parameters, including dissolved oxygen, organic nitrogen, ammonium nitrogen, nitrate nitrogen, organic phosphorus, and inorganic phosphorus in the pre-monsoon season. The performance of the model was evaluated using statistics based on root mean square errors (RMSE).
QUAL2K has also been used to predict the dissolved oxygen and biochemical oxygen demand (BOD) of the lower reach of the Diyala River in Iraq. The model was applied to a 16.90 km stretch of the river using hydraulic and water quality data. In another study, the Qual2K model was combined with the HEC-RAS model to assess the water quality of a tidal river in northern Taiwan. The simulation results, which took tidal effects into consideration, agreed with the monitoring data of the river.
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CALPUFF model for atmospheric dispersion
CALPUFF is an advanced atmospheric dispersion model that can be used to simulate the spread of pollution from buoyant, puff, or continuous point, line, and area sources. The model was originally developed by the Sigma Research Corporation in the late 1980s under a contract with the California Air Resources Board. It has since been adopted by the United States Environmental Protection Agency (EPA) as a preferred model for assessing the long-range transport of pollutants and their impacts on Federal Class I areas.
CALPUFF is an integrated Lagrangian puff modeling system that consists of three main components: CALMET, CALPUFF, and CALPOST. CALMET is a diagnostic 3-dimensional meteorological model that provides the necessary meteorological data for the simulation. CALPUFF is the air quality dispersion model that simulates the dispersion of pollutants. CALPOST is a post-processing package used to analyze the output of the CALPUFF model.
One unique aspect of the CALPUFF model is its ability to simulate the secondary fine particles formed by chemical reactions in atmospheric transports. This feature sets it apart from other dispersion models such as AERMOD. Additionally, CALPUFF includes algorithms for handling the effect of downwash by nearby buildings in the path of the pollution plumes, making it suitable for simulating pollution dispersion in complex urban environments.
The CALPUFF model has been used in various studies to analyze industrial air pollution and long-term health risks. For example, Rzeszutek et al. (2023) used CALPUFF to study the dispersion of PM10, NO2, and SO2 pollutants released from industrial activities in Malaysia. The model has also been applied in combination with other models, such as WRF and CALWRF, to improve the accuracy of predictions and better understand the complex interactions between meteorological conditions and pollution dispersion.
Overall, the CALPUFF model is a powerful tool for simulating atmospheric pollution dispersion and assessing the potential impacts of pollutants on the environment and human health. Its flexibility, accuracy, and ability to handle complex scenarios make it a preferred choice for regulatory agencies and researchers alike in the field of air quality modeling and pollution control.
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Frequently asked questions
You can use a Lagrangian/Gaussian model such as US EPA's AERMOD or ADMS.
QUAL2K is a one-dimensional river and stream water quality model that can simulate the migration and transformation of conventional pollutants. It was used to calculate the water environmental capacity of the Hongqi River.
IAQX is an indoor air quality (IAQ) simulation software package that can be used to estimate exposure to indoor air pollutants. It is for advanced users who have experience with exposure estimation, pollution control, risk assessment, and risk management.
