| For construction projects that may produce harmful gases,the prediction and determination of health protection distance is an indispensable or very important part of environmental impact assessment.With the continuous improvement of people's living standards,the increasing awareness of the environment and the urgent need for a good ecological environment and environmental quality,the health protection distance of construction projects has become more and more concerned.How to scientifically and reasonably determine the distance between the production unit of unorganized emission of harmful gases and sensitive areas such as hospitals,schools and residential areas,as well as the health protection distance,becomes very important.This paper compares and analyses three methods to determine the health protection distance of construction projects,their respective scope of application and their advantages and disadvantages.The calculation parameters of health protection distance,the selection of main atmospheric pollutants,the determination of emission level of atmospheric pollutants,the methods of measuring and calculating unorganized emissions were analyzed.(1)According to the relevant provisions of "Technical Guidelines for Environmental Impact Assessment of Atmospheric Environment"(HJ 2.2-2018),taking a chemical plant in Shaanxi Province in a typical hilly and gully region of the Loess Plateau as an example,the selection of process flow and pollution production links,accounting factors and pollutant emission analysis,the determination method of health protection distance,the monitoring scheme of non-organized pollution sources and the selection of prediction model were carried out.To calculate and determine the health protection distance.This paper studies the atmospheric environmental protection distance calculated based on "Technical Method for Establishing Local Air Pollutant Emission Standards" and SCREEN 3 atmospheric environmental protection distance calculation model when the atmospheric environment is in complex terrain and produces unorganized harmful gas emissions.The difference between the atmospheric environmental protection distance calculated by SCREEN 3 model and AERMOD model is compared and analyzed.Finally,the sanitary protection distance of existing devices is calculated.For: caustic soda device 200 m,hydrogen chloride synthesis device 600 m,vinyl chloride synthesis device 500 m.After the completion of the second phase(II)of the project,the sanitary protection distance of the plant is 250 m for caustic soda,700 m for hydrogen chloride synthesis and 600 m for vinyl chloride synthesis.(2)The conclusion proves that the calculation model of atmospheric environmental protection distance and the technical method for formulating local atmospheric pollutant emission standards recommended by industry standards are relatively simple due to its early introduction and implementation.When calculating the distance,it is only related to the area of non-point sources,source strength and average wind speed,and it is impossible to consider the local high concentration caused by complex areas similar to this project.Environmental impacts such as degree zones can not meet the needs.The ARMOD model recommended by the Technical Guidelines for Environmental Impact Assessment Atmospheric Environment is a further atmospheric prediction model recommended in recent years.Taking the excessive range of pollutants discharged by the project as a health protection distance,the ARMOD model can fully reflect the role of topography,meteorology and other major factors affecting pollutant diffusion.On this basis,the health protection model can be predicted or determined.Scientific and reasonable.(3)The paper also puts forward the technical method of determining the intensity of unorganized emission sources as soon as possible,and some suggestions on the standard of atmospheric environmental protection distance in some industries,which can provide reference for environmental assessment and ecological environmental protection. |
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