Characterization and Local Emission Sources for Ammonia in an Urban Environment.

Ammonia levels were evaluated in the urban environment of Madrid City, Spain. A total of 110 samplers were distributed throughout the city. Vehicle traffic density, garbage containers and sewers were identified as local emission sources of ammonia. The average ammonia concentrations were 4.66 ± 2.14 µg/m3 (0.39-11.23 µg/m3 range) in the winter and 5.30 ± 1.81 µg/m3 (2.33-11.08 µg/m3 range) in the summer. Spatial and seasonal variations of ammonia levels were evaluated. Hotspots were located in the south and center of Madrid City in both winter and summer seasons, with lower ammonia concentrations located in the north (winter) and in the west and east (summer). The number of representative points that were needed to establish a reliable air quality monitoring network for ammonia was determined using a combined clustering and kriging approach. The results indicated that 40 samplers were sufficient to provide a reliable estimate for Madrid City.