Temporal and spatial variation in monitoring of ambient urban air pollutants

Air pollution data from monitoring stations are widely used as a surrogate for human exposure. Automated continuous monitors provide greater temporal resolution than cumulative samplers, but cost and practical constraints generally limit their use to small numbers of sites in any urban area. Spatial and temporal variation of air pollution and the representativeness of urban monitoring stations have been investigated on distance scales ranging from street segments to citywide. Review of the research suggests that spatial variability may be scale-invariant and may sometimes modulate characteristic temporal patterns.