*4.2. Morphology-Optimization Strategies for Pollutant Dispersion at Neighborhood-Scale*

Based on the findings of the preceding investigation, strategies for optimizing neighborhood morphology based on air quality improvements were proposed. First, the relationship between BD, BED and PM2.5 show a trend of sine and cosine curves. Therefore, BD should be reasonably controlled in the neighborhoods, and the BED of residential buildings along the street should be reduced while increasing the commercial buildings along the street (Figure 12a). Second, in terms of functional morphological characteristics, GCR showed a reduced influence on wind speed and PM2.5 below the canopy, and the reducing effect decreases as the vertical height above the canopy increases. Therefore, it is critical to plant a diverse variety of vegetation species of varying heights (Figure 12b). Furthermore, it is important to increase the GCR while ensuring the functional integrity of the neighborhoods. Third, in terms of the shape morphological characteristics, ABF and ABV showed a trend of increasing and then decreasing with PM2.5 values. Therefore, when the intensity of development is identified, specific buildings' heights should be increased, and the individual building's masses and number of total buildings in the neighborhood should be limited (Figure 12c). Additionally, the difference of building heights should be reasonably delineated (Figure 12d), according to the SDH curve fitting, to promote the climbing of incoming winds.

**Figure 12.** Morphology-optimization strategies for pollutant dispersion: (**a**) BED solution; (**b**) GCR solution; (**c**) ABV solution; (**d**) SDH solution.
