Study On The Response To Parameter Variation In Two Atmospheric Models Of AERMOD And SCREEN3

Atmospheric prediction is an indispensable part of the atmospheric environmental impact assessment. According to the results of prediction, the impact of project operations to the atmospheric environment were accurately determined. It also provides reference to the adjustment of the layout and design of environmental protection measures. In this paper, the parameter variation response of the SCREEN3 model and the AERMOD model and their applications in the concrete cases were investigated. Firstly, the single effect of the air temperature, flue gas flux and pollution source strength were studied by sensitivity analysis method. Thereafter, the orthogonal test method and grey correlation analysis method were used to research the comprehensive influence of these parameters. The effect of the wind direction,wind speed, surface type, surface humidity and building downwash parameters were discussed by using sensitivity analysis method. Finally, taking a mechanical project as an example to study the SCREEN3 model and AERMOD model. The fuzzy mathematics method was used to verify the similarity between the predictive results and the monitoring data, it is proved whether the parameters set are correct, and provide theoretical basis and reference for improving the scientific and accuracy of atmospheric environmental impact assessment. The main contents of research and the results are as follows:(1)The single effect of the air temperature, flue gas flux and pollution source strength were discussed by sensitivity analysis method. The results showed that there was a significant relationship between the maximum concentration predictive value and the three parameters. The maximum concentration is positively correlated with the air temperature, pollution source strength, and is negatively correlated with the flue gas flux. In terms of the comprehensive influence of these parameters,orthogonal test method and grey correlation analysis method are used to analyze the results which turns out to be the same. The sequence of the parameter sensitivity is as follows:pollution source strength>flue gas flux >air temperature. So it can be seen that theapplication of the two methods is correct. The interaction effect of these parameters were researched by orthogonal test method. The results showed that the interaction between flue gas flux and pollution source strength is more significant, the interaction between air temperature and flue gas flux, pollution source strength is not obvious.(2)Wind direction, wind speed, surface type, surface humidity and building downwash parameters all have significant influence on AERMOD model prediction results. By considering the wind effects, it is clear to see that: when the wind direction is not at the same time, the prediction results gradually decrease with the increase of the wind speed, and the decreasing speed is gradually slow; When the wind speed is not at the same time, the forecast results change with the wind direction, the maximum concentration is concentrated in downwind of the pollution sources. By considering the type of surface and surface humidity, it is clear to see that: when the surface type is not at the same time, the prediction results are decreased with the increase of the surface humidity; When the surface humidity is not at the same time,The order of influence of surface type is as follows: city >crops>grassland. By considering the building downwash parameters, it is clear to see that the maximum pollutant concentration were decreased with the increase of the chimney height.(3)In accordance with the response of the SCREEN3 model and the AERMOD model to the parameter variation in the atmospheric prediction, a mechanical project can be taken as an example to study the use of SCREEN3 model and AERMOD model. The fuzzy mathematics method is used to verify the similarity between the predicted results and the monitoring data, It is proved that the prediction result is ideal and these parameters are really important. Therefore, before carrying out the environmental impact assessment work, first of all, a comprehensive survey of the actual parameters were conducted. If there are a lot of parameters, using orthogonal test method or grey correlation analysis method to sort each parameter. Great influence parameters must be investigated and accurately grasped, and less affected parameters can be estimated appropriately. After the end of the forecast, the fuzzy mathematics method is used to verify the similarity between the predictive results and the monitoring data. we can adjust the working direction and eliminate the error intime pursuant to the results. Through the above work, we can improve the function of model, the accuracy of prediction, and realize the accurate application of SCREEN3 model and AERMOD model in atmospheric environmental impact assessment.