# AERQ--A Web-Based Decision Support Tool for Air Quality Assessment
## 2 Materials and Methods  
AERMOD [22; 23] was selected as the central modeling platform for this research. Compared to models like CALPUFF [24] or ADMS [25], AERMOD excels in high-resolution dispersion modeling, making it particularly suitable for urban environments where pollutant levels vary significantly across small spatial scales. Its non-reactive nature aligns with this study's focus on the local-scale dispersion of NO\({}_{2}\) and primary emissions, where chemical reactions are expected to have minimal influence compared to transport and dispersion dynamics. Additionally, AERMOD was chosen by the US EPA as the reference model for air quality assessments, ensuring compliance with established environmental standards. Its computational efficiency and robust handling of complex terrain and meteorological conditions further validate its use in this study.  
AERMOD is an air quality dispersion model based on atmospheric boundary layer turbulence structures. It simulates the dispersion of pollutants from multiple ground-level and elevated sources, including point, area, and volume sources. The AERMOD suite uses numerical solvers to simulate dispersive phenomena, pollutant transport, and both dry and wet removal processes as meteorological conditions change. It also accounts for the geomorphology of the terrain and integrates chemical transformation modules.  
The dispersion algorithms in AERMOD handle both convective and stable atmospheric conditions, considering urban and rural environments, and the influence of buildings and structures. AERMOD defines the boundary layer by calculating parameters such as the Monin-Obukhov length (which represents the height at which turbulence is primarilydriven by buoyancy rather than wind shear), surface friction velocity (shear velocity), surface roughness length (which accounts for the effect of surface roughness on near-ground wind speed), sensible heat flux, convective scaling velocity, and mixing heights driven by both shear and convection. AERMET [26] processes these parameters and meteorological data to model the vertical structure of wind, temperature, and turbulence. AERMET then generates input files for AERMOD.  
AERMOD calculates pollutant concentrations using a steady-state plume model. Terrain influence was accounted for by combining horizontal and terrain-following plumes. The dispersion algorithms were adapted for both convective and stable conditions, considering the characteristics of urban and rural areas, and the impact of vertical structures like buildings. In the current version of the DSS, the AERMOD version 16216r was used.  
AERMOD can simulate various pollutants, like nitrogen dioxide (NO\({}_{2}\)), carbon monoxide (CO), sulfur dioxide (SO\({}_{2}\)), particulate matter (PM), non-methane hydrocarbon (NMHC). It is widely utilized for regulatory compliance assessments, environmental impact studies, and air quality management. It provides detailed information on pollutant dispersion patterns, aiding in evaluating potential health risks and developing effective mitigation strategies. The AERMOD modeling suite has proved versatile and accurate, a valuable tool for assessing and managing air quality in diverse urban and industrial settings [27; 28; 29].