User:Milton Beychok/Sandbox

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Atmospheric dispersion models are computer programs that use mathematical algorithms to simulate how pollutants in the ambient atmosphere disperse and, in some cases, how they react in the atmosphere. The dispersion models are used to estimate or to predict the downwind concentration of air pollutants emitted from sources such as industrial plants and vehicular traffic. Such models are important to governmental agencies tasked with protecting and managing the ambient air quality. The models are typically used to determine whether existing or proposed new industrial facilities are or will be in compliance with national ambient air quality standards. The models may also be used assist in the design of effective control strategies to reduce emissions of harmful air pollutants.

The dispersion models require the input of data which includes:

  • Meteorological conditions such as wind speed and direction, the amount of atmospheric turbulence (as characterized by what is called the "stability class"), the ambient air temperature and the height to the bottom of any inversion aloft that may be present.
  • Emissions parameters such as source location and height, source vent stack diameter and exit velocity, exit temperature and mass flow rate.
  • Terrain elevations at the source location and at the receptor location.
  • The location, height and width of any obstructions (such as buildings or other structures) in the path of the emitted gaseous plume.

The atmospheric dispersion models are also known as atmospheric diffusion models, air dispersion models, air quality models, and air pollution dispersion models. This compilation of atmospheric dispersion models lists and, where possible, very briefly describes many of the models currently in use worldwide.

Atmospheric layers

Discussion of the layers in the Earth's atmosphere is needed to understand where airborne pollutants disperse in the atmosphere. The layer closest to the earth's surface is known as the troposphere. It extends from sea-level to a height of about 18 km and contains about 80 percent of the mass of the overall atmosphere. The stratosphere is the next layer and extends from 18 km to about 50 km. The third layer is the mesosphere which extends from 50 km to about 80 km. There are other layers above 80 km, but they are insignificant with respect to atmospheric dispersion modeling.

The lowest part of the troposphere is called the atmospheric boundary layer (ABL) or the planetary boundary layer (PBL) and extends from the Earth's surface to about 1.5 to 2.0 km in height. The air temperature of the atmospheric boundary layer decreases with increasing altitude until it reaches what is called the inversion layer (where the temperature increases with increasing altitude) that caps the atmospheric boundary layer. The upper part of the troposphere (i.e., above the inversion layer) is called the free troposphere and it extends up to the 18 km height of the troposphere.

The ABL is of the most importance with respect to the emission, transport and dispersion of airborne pollutants. The part of the ABL between the Earth's surface and the bottom of the inversion layer is known as the mixing layer. Almost all of the airborne pollutants emitted into the ambient atmosphere are transported and dispersed within the mixing layer. Some of the emissions penetrate the inversion layer and enter the free troposphere above the ABL.

In summary, the layers of the Earth's atmosphere from the surface of the ground upwards are: the ABL made up of the mixing layer capped by the inversion layer; the free troposphere; the stratosphere; the mesosphere and others. Many atmospheric dispersion models are referred to as boundary layer models because they mainly model air pollutant dispersion within the ABL. To avoid confusion, it should be noted that models referred to as mesoscale models have dispersion modelling capabilities that extend horizontally up to a few hundred kilometres. It does not mean that they model dispersion in the mesosphere.

U.S. Environmental Protection Agency models

Many of the dispersion models developed by or accepted for use by the U.S. Environmental Protection Agency (EPA) are accepted for use in many other countries as well. Those EPA models are grouped below into four categories.

Preferred and recommended models

  • CALPUFF - A non-steady-state puff dispersion model that simulates the effects of time- and space-varying meteorological conditions on pollution transport, transformation, and removal. CALPUFF can be applied for long-range transport and for complex terrain.
  • BLP - A Gaussian plume dispersion model designed to handle unique modelling problems associated with industrial sources where plume rise and downwash effects from stationary line sources are important.
  • CAL3QHC and CAL3QHCR - CAL3QHC is a CALINE3 based model with queuing calculations and a traffic model to calculate delays and queues that occur at signalized intersections. CAL3QHCR is a more refined version based on CAL3QHC that requires local meteorological data.
  • CTDMPLUS - A Complex Terrain Dispersion Model (CTDM) plus algorithms for unstable situations (i.e., highly turbulent atmospheric conditions). It is a refined point source Gaussian air quality model for use in all stability conditions (i.e., all conditions of atmospheric turbulence) for complex terrain.
  • OCD - Offshore and Coastal Dispersion Model (OCD) is a Gaussian model developed to determine the impact of offshore emissions from point, area or line sources on the air quality of coastal regions. It incorporates overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline.

Alternative models

  • ADAM - Air Force Dispersion Assessment Model (ADAM) is a modified box and Gaussian dispersion model which incorporates thermodynamics, chemistry, heat transfer, aerosol loading, and dense gas effects.
  • ADMS-3 - Atmospheric Dispersion Modelling System (ADMS-3) is an advanced dispersion model developed in the United Kingdom for calculating concentrations of pollutants emitted both continuously from point, line, volume and area sources, or discretely from point sources.
  • SLAB - A model for denser-than-air gaseous plume releases that utilizes the one-dimensional equations of momentum, conservation of mass and energy, and the equation of state. SLAB handles point source ground-level releases, elevated jet releases, releases from volume sources and releases from the evaporation of volatile liquid spill pools.
  • DEGADIS - Dense Gas Dispersion (DEGADIS) is a model that simulates the dispersion at ground level of area source clouds of denser-than-air gases or aerosols released with zero momentum into the atmosphere over flat, level terrain.
  • HGSYSTEM - A collection of computer programs developed by Shell Research Ltd. and designed to predict the source-term and subsequent dispersion of accidental chemical releases with an emphasis on dense gas behavior.
  • HOTMAC and RAPTAD - HOTMAC is a model for weather forecasting used in conjunction with RAPTAD which is a puff model for pollutant transport and dispersion. These models are used for complex terrain, coastal regions, urban areas, and around buildings where other models fail.
  • HYROAD - The Hybrid Roadway Model integrates three individual modules simulating the pollutant emissions from vehicular traffic and the dispersion of those emissions. The dispersion module is a puff model that determines concentrations of carbon monoxide (CO) or other gaseous pollutants and particulate matter (PM) from vehicle emissions at receptors within 500 meters of the roadway intersections.
  • ISC3 - A Gaussian model used to assess pollutant concentrations from a wide variety of sources associated with an industrial complex. This model accounts for: settling and dry deposition of particles; downwash; point, area, line, and volume sources; plume rise as a function of downwind distance; separation of point sources; and limited terrain adjustment. ISC3 operates in both long-term and short-term modes.
  • OBODM - A model for evaluating the air quality impacts of the open burning and detonation (OB/OD) of obsolete munitions and solid propellants. It uses dispersion and deposition algorithms taken from existing models for instantaneous and quasi-continuous sources to predict the transport and dispersion of pollutants released by the open burning and detonation operations.
  • PLUVUEII - A model that estimates atmospheric visibility degradation and atmospheric discoloration caused by plumes resulting from the emissions of particles, nitrogen oxides, and sulfur oxides. The model predicts the transport, dispersion, chemical reactions, optical effects and surface deposition of such emissions from a single point or area source.
  • SCIPUFF - A puff dispersion model that uses a collection of Gaussian puffs to predict three-dimensional, time-dependent pollutant concentrations. In addition to the average concentration value, SCIPUFF predicts the statistical variance in the concentrations resulting from the random fluctuations of the wind.
  • SDM - Shoreline Dispersion Model (SDM) is a Gaussian dispersion model used to determine ground-level concentrations from tall stationary point source emissions near a shoreline.

Screening models

These are models that are often used before applying a refined air quality model to determine if refined modelling is needed.

  • AERSCREEN - The screening version of AERMOD. It produces estimates of concentrations, without the need for meteorological data, that are equal to or greater than the estimates produced by AERMOD with a full set of meteorological data. AERSCREEN is still under development and is not currently available to the public.
  • CTSCREEN - The screening version of CTDMPLUS.
  • SCREEN3 - The screening version of ISC3.
  • TSCREEN - Toxics Screening Model (TSCREEN) is a Gaussian model for screening toxic air pollutant emissions and their subsequent dispersion from possible releases at superfund sites. It contains 3 modules: SCREEN3, PUFF, and RVD (Relief Valve Discharge).
  • VALLEY - A screening, complex terrain, Gaussian dispersion model for estimating 24-hour or annual concentrations resulting from up to 50 point and area emission sources.
  • COMPLEX1 - A multiple point source screening model with terrain adjustment that uses the plume impaction algorithm of the VALLEY model.
  • RTDM3.2 - Rough Terrain Diffusion Model (RTDM3.2) is a Gaussian model for estimating ground-level concentrations of one or more co-located point sources in rough (or flat) terrain.
  • VISCREEN - A model that calculates the impact of specified emissions for specific transport and dispersion conditions.

Photochemical models

Photochemical air quality models have become widely utilized tools for assessing the effectiveness of control strategies adopted by regulatory agencies. These models are large-scale air quality models that simulate the changes of pollutant concentrations in the atmosphere by characterizing the chemical and physical processes in the atmosphere. These models are applied at multiple geographical scales ranging from local and regional to national and global.

  • Models-3/CMAQ - The latest version of the Community Multi-scale Air Quality (CMAQ) model has state-of-the-science capabilities for conducting urban to regional scale simulations of multiple air quality issues, including tropospheric ozone, fine particles, toxics, acid deposition, and visibility degradation.
  • CAMx - The Comprehensive Air quality Model with extensions (CAMx) simulates air quality over many geographic scales. It handles a variety of inert and chemically active pollutants, including ozone, particulate matter, inorganic and organic PM2.5/PM10, and mercury and other toxics.
  • REMSAD - The Regional Modeling System for Aerosols and Deposition (REMSAD) calculates the concentrations of both inert and chemically reactive pollutants by simulating the atmospheric processes that affect pollutant concentrations over regional scales. It includes processes relevant to regional haze, particulate matter and other airborne pollutants, including soluble acidic components and mercury.
  • UAM-V - The Urban Airshed Model was a pioneering effort in photochemical air quality modelling in the early 1970s and has been used widely for air quality studies focusing on ozone.

Models developed in the United Kingdom

  • ADMS-3 - See the description of this model in the Alternative Models section of the models accepted by the U.S. EPA.
  • ADMS-URBAN - A model for simulating dispersion on scales ranging from a street scale to city-wide or county-wide scale, handling most relevant emission sources such as traffic, industrial, commercial, and domestic sources. It is also used for air quality management and assessments of current and future air quality vis-a-vis national and regional standards in Europe and elsewhere.
  • ADMS-Roads - A model for simulating dispersion of vehicular pollutant emissions from small road networks in combination with emissions from industrial plants. It handles multiple road sources as well as multiple point, line or area emission sources and the model operation is similar to the other ADMS models
  • ADMS-Screen - A screening model for rapid assessment of the air quality impact of a single industrial stack to determine if more detailed modelling is needed. It combines the dispersion modelling algorithms of the ADMS models with a user interface requiring minimal input data.
  • GASTAR - A model for simulating accidental releases of denser-than-air flammable and toxic gases. It handles instantaneous and continuous releases, releases from jet sources, releases from evaporation of volatile liquid pools, variable terrain slopes and ground roughness, obstacles such as fences and buildings, and time-varying releases.
  • NAME - Nuclear Accident ModEl (NAME) is a local to global scale model developed by the UK's Met Office. It is used for: forecasting of air quality, air pollution dispersion, and acid rain; tracking radioactive emissions and volcanic ash discharges; analysis of accidental air pollutant releases and assisting in emergency response; and long-term environmental impact analysis. It is an integrated model that includes boundary layer dispersion modelling.
  • UDM - Urban Dispersion Model is a Gaussian puff based model for predicting the dispersion of atmospheric pollutants in the range of 10m to 25km throughout the urban environment. It is developed by the Defense Science and Technology Laboratory for the UK Ministry of Defence. It handles instantaneous, continuous, and pool releases, and can model gases, particulates, and liquids. The model has a three regime structure: that of single building (area density < 5%), urban array (area density > 5%) and open. The model can be coupled with the US model SCIPUFF to replace the open regime and extend the model's prediction range.

Models developed in continental Europe

The European Topic Centre on Air and Climate Change, which is part of the European Environment Agency (EEA), maintains an online Model Documentation System (MDS) that includes descriptions and other information for almost all of the dispersion models developed by the countries of Europe. The MDS currently contains 104 models developed in Europe (excluding the United Kingdom). Of those 104 models, 29 were subjectively selected for inclusion here. Anyone interested in seeing the complete MDS can access it here.

Some of the European models listed in the MDS are public domain and some are not. Many of them include a pre-processor module for the input of meteorological and other data, and many also include a post-processor module for graphing the output data and/or plotting the area impacted by the air pollutants on maps.

The country of origin is included for the each of the European models listed below.

  • ONM9440 (Austria) - A Gaussian dispersion model for continuous, buoyant plumes from stationary sources for use in flat terrain areas. It includes plume depletion by dry deposition of solid particulates.
  • GRAL (Austria) - The GRAz Lagrangian model was developed at the Graz University of Technology and it is a dispersion model for buoyant plumes from multiple point, line and tunnel portal sources. It handles flat or complex terrain but it has no chemistry or deposition capabilities.
  • IFDM (Belgium) - The Immission Frequency Distribution Model, developed at the Flemish Institute for Technological Research(VITO), is a Gaussian dispersion model used for point and area sources dispersing over flat terrain on a local scale. The model includes plume depletion by dry or wet deposition but cannot handle building effects, chemical transformations or complex terrain.
  • SEVEX (Belgium) - The SEVeso EXpert model simulates the accidental release of toxic and/or flammable material over flat or complex terrain from multiple pipe and vessel sources or from evaporation of volatile liquid spill pools. The accidental releases may be continuous, transient or catastrophic. The integrated model can handle denser-than-air gases as well as neutral gases (i.e., neither denser than or lighter than air). It does not include handling of multi-component material, nor does it provide for chemical transformation of the releases. The model's name is derived from the major disaster caused by the accidental release of highly toxic gases that occurred in Seveso, Italy in 1976.
  • HAVAR (Czech Republic) - A Gaussian plume model integrated with a puff model and a hybrid plume-puff model, developed by the Czech Academy of Sciences, is intended for routine and/or accidental releases of radionuclides from single point sources within nuclear power plants. The model includes radioactive plume depletion by dry and wet deposition as well as by radioactive decay. For the decay of some nuclides, the creation of daughter products that then grow into the plume is taken into account.
  • SYMOS'97 (Czech Republic) - A model, developed by the Czech Hydrometeorological Institute, for dispersion calculations of continuous neutral or buoyant plumes from single or multiple point, area or line sources. It can handle complex terrain and it can also be used to simulate the dispersion of cooling tower plumes.
  • OML (Denmark) - A model for dispersion calculations of continuous neutral or buoyant plumes from single or multiple, stationary point and area sources. It has some simple methods for handling photochemistry (primarily for NO2) and for handling complex terrain. The model was developed by the National Environmental Research Institute of Denmark, which is a part of the Danish Ministry of the Environment.
  • AEROPOL (Estonia) - The AERO-POLlution model developed at the Tartu Observatory in Estonia is a Gaussian plume model for simulating the dispersion of continuous, buoyant plumes from stationary point, line and area sources over flat terrain on a local to regional scale. It includes plume depletion by wet and/or dry deposition as well as the effects of buildings in the plume path.
  • BUO-FMI (Finland) - This model was developed by the Finnish Meteorological Institute (FMI) specifically for estimating the atmospheric dispersion of neutral or buoyant plume gases and particles emitted from fires in warehouses and chemical stores. It is a hybrid of a local scale Gaussian plume model and another model type. Plume depletion by dry deposition is included but wet deposition is not included.
  • CAR-FMI (Finland) - This model was developed by the Finnish Meteorological Institute (FMI) for evaluating atmospheric dispersion and chemical transformation of vehicular emissions of inert (CO, NOx) and reactive (NO, NO2, O3) gases from a road network of line sources on a local scale. It is a Gaussian line source model which includes an analytical solution for the chemical cycle NO-O3-NO2.
  • UDM-FMI (Finland) - This model was developed by the Finnish Meteorological Institute (FMI) as an integrated Gaussian urban scale model intended for regulatory pollution control. It can handles multiple point, line, area and volume sources and it includes chemical transformation (for NO2), wet and and dry deposition (for SO2), and downwash phenomena (but no building effects).
  • MERCURE (France) - An atmospheric dispersion modeling CFD code developed by Electricite de France (EDF) and distributed by ARIA Technologies, a French company. The code is a version of the CFD software ESTET, developed by EDF's Laboratoire National d'Hydraulique.
  • RADM (France) - The Random-walk Advection and Dispersion Model (RADM) was developed by ACRI-ST, an independent research and development organization in France. It can model gas plumes and particles (including pollutants with exponential decay or formation rates) from single or multiple stationary, mobile or area sources. Chemical reaction, radioactive decay, deposition, complex terrain, and inversion conditions are accommodated.
  • STOER.LAG (Germany) - A dispersion model designed to evaluate accidental releases of hazardous and/or flammable materials from point or area sources in industrial plants. It can handle neutral and denser-than-air gases or aerosols from ground-level or elevated sources. The model accommodates building and terrain effects, evaporation of volatile liquid spill pools, and combustion or explosion of flammable gas-air mixtures (including the impact of heat and pressure waves caused by a fire or explosion).
  • PROKAS-V (Germany) - A Gaussian dispersion model for evaluating the atmospheric dispersion of air pollutants emitted from vehicular traffic on a road network of line sources on a local scale.
  • AUSTAL2000 (Germany) - The official air dispersion model to be used in the permitting of industrial sources by the German Federal Environmental Agency. The model accommodates point, line, area and volume sources of buoyant plumes. It has capabilities for building effects, complex terrain, plume depletion by wet or dry deposition, and first order chemical reactions. It is based on the LASAT model developed by Ingenieurbüro Janicke Gesellschaft für Umweltphysik.
  • ATSTEP (Germany) - Gaussian Puff Dispersion and Deposition model used in the decision support system RODOS (Real-time On-line Decision Support) for nuclear emergency management. RODOS is operational in Germany by the Federal Office for Radiation Protection (BfS) and test-operational in many other European countries. More information on RODOS is available here and on the ATSTEP model here.
  • DIPCOT (Greece) - DIsPersion over COmplex Terrain (DIPCOT) is a model developed in the National Centre of Scientific Research "DEMOKRITOS" of Greece that simulates dispersion of buoyant plumes from multiple point sources over complex terrain on a local to regional scale. It does not include wet deposition or chemical reactions.
  • DISPLAY-2 (Greece) - A vapour cloud dispersion model for neutral or denser-than-air pollution plumes over irregular, obstructed terrain on a local scale. It accommodates jet releases as well as two-phase (i.e., liquid-vapor mixtures) releases. This model was also developed at the National Centre of Scientific Research "DEMOKRITOS" of Greece.
  • MUSE (Greece) - A photochemical atmospheric dispersion model developed by Professor Nicolas Moussiopoulos at the Aristotle University of Thessaloniki in Greece. It is intended for the study of photochemical smog formation in urban areas and assessment of control strategies on a local to regional scale. It can simulate dry deposition and transformation of pollutants can be treated using any suitable chemical reaction mechanism.
  • MEMO (Greece) - A Eulerian non-hydrostatic prognostic mesoscale model for wind flow simulation. It was developed by the Aristotle University of Thessaloniki in collaboration with the Universität Karlsruhe. This model is designed for describing atmospheric transport phenomena in the local-to-regional scale, often referred to as mesoscale air pollution models.
  • FARM (Italy) - The Flexible Air quality Regional Model (FARM) is an atmospheric dispersion model designed for the analysis of episodes and scenarios, evaluation of the effects of regional emission control policies and pollution forecasts in complex situations. It accommodates point and area sources, and includes photochemistry and plume depletion by wet and dry deposition.
  • SAFE_AIR II (Italy) - The Simulation of Air pollution From Emissions II (SAFE AIR II) was developed at the Department of Physics, University of Genoa, Italy to simulate the dispersion of air pollutants above complex terrain at local and regional scales. It can handle point, line, area and volume sources and continuous plumes as well as puffs. It includes first-order chemical reactions and plume depletion by wet and dry deposition, but it does not include any photochemistry.
  • STACKS (The Netherlands) - A Gaussian plume dispersion model for point and area buoyant plumes to be used over flat terrain on a local scale. It includes building effects, NO2 chemistry and plume depletion by deposition. It is used for environmental impact studies and evaluation of emission reduction strategies.
  • CAR-International (The Netherlands) - Calculation of Air pollution from Road traffic(CAR-International) is an atmospheric dispersion model developed by the Netherlands Organisation for Applied Scientific Research. It is used for simulating the dispersion of vehicular emissions from roadway traffic.
  • LOTOS-EUROS (The Netherlands) - The LOng Term Ozone Simulation - EURopean Operational Smog (LOTOS-EUROS) model was developed by the Netherlands National Institute for Public Health and the Environment (RIVM) in The Netherlands. It is designed for modelling the dispersion of pollutants (such as: photo-oxidants, aerosols, heavy metals) over all of Europe. It includes simple reaction chemistry as well as wet and dry deposition.
  • EK100W (Poland) - A Gaussian plume model used for air quality impact assessments of pollutants from industrial point sources as well as for urban air quality studies on a local scale. It includes wet and dry deposition. The effects of complex terrain are not included.
  • POLGRAPH (Portugal) - This model was developed at the University of Aveiro, Portugal by Professor Carlos Borrego. It was designed for evaluating the impact of industrial pollutant releases and for air quality assessments. It is a Gaussian plume dispersion model for continuous, elevated point sources to be used on a local scale over flat or gently rolling terrain.
  • INPUFF-U (Romania) - This model was developed by the National Institute of Meteorology and Hydrology in Bucharest, Romania. It is a Gaussian puff model for calculating the dispersion of radionuclides from passive emission plumes on a local to urban scale. It can simulate accidental or continuous releases from stationary or mobile point sources. It includes wet and dry deposition. Building effects, buoyancy effects, chemical reactions and effects of complex terrain are not included.
  • MODIM (Slovak Republic) - A model for calculating the dispersion of continuous, neutral or buoyant plumes on a local to regional scale. It integrates a Gaussian plume model for single or multiple point and area sources with a numerical model for line sources, street networks and street canyons. It is intended for regulatory and planning purposes.
  • DISPERSION21 (Sweden) - This model was developed by the Swedish Meteorological and Hydrological Institute (SMHI) for evaluating air pollutant emissions from existing or planned industrial or urban sources on a local scale. It is a Gaussian plume model for point, area, line and vehicular traffic sources. It includes plume penetration of inversions aloft, building effects, NOx chemistry and it can handle street canyons. It does not include wet or dry deposition, complex atmospheric chemistry, or the effects of complex terrain.

Models developed in Australia

  • AUSPLUME - A dispersion model that has been designated as the primary model accepted by the Environmental Protection Authority (EPA) of the Australian state of Victoria.
  • LADM - An advanced model developed by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) for simulating the dispersion of buoyant pollution plumes and predicting the photochemical formation of smog over complex terrain on a local to regional scale. The model can also handle fumigated plumes (see the books listed below in the "Further reading" section for an explanation of fumigated plumes).
  • TAPM - An advanced dispersion model integrated with a pre-processor for providing meteorological data inputs. It can handle multiple pollutants, and point, line, area and volume sources on a local, city or regional scale. The model capabilities include building effects, plume depletion by deposition, and a photochemistry module. This model was also developed by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO).
  • DISPMOD - A Gaussian atmospheric dispersion model for point sources located in coastal regions. It was designed specifically by the Western Australian Department of Environment to simulate the plume fumigation that occurs when an elevated onshore pollution plume intersects a growing thermal internal boundary layer (TIBL) contained within offshore air flow coming onshore.
  • AUSPUFF - A Gaussian puff model designed for regulatory use by CSIRO. It includes some simple algorithms for the chemical transformation of reactive air pollutants.

Other models

  • PUFF-PLUME - A Gaussian chemical/radionuclide dispersion model that includes wet and dry deposition, real-time input of meteorological observations and forecasts, dose estimates from inhalation and gamma shine, and puff or plume dispersion modes. It is the primary model for emergency response use for atmospheric releases of radioactive materials at the Savannah River Site of the United States Department of Energy. It was first developed by the Pacific Northwest National Laboratory (PNNL) in the 1970's.

See also

Air pollution dispersion models

Others

Further reading

For those who would like to learn more about atmospheric dispersion models, it is suggested that either one of the following books be read:

External links

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