Which GIS analysis is specifically used to identify areas with unusually high concentrations of a pollutant?

• A. Buffer analysis
• B. Overlay analysis
• C. Hotspot/cluster analysis
• D. Interpolation

Answer: (C)

Identifying areas with unusually high concentrations of a pollutant hinges on detecting meaningful spatial patterns and testing whether those high values are more clustered than expected by chance. Hotspot/cluster analysis does just that. It looks for statistically significant clusters of high values (hotspots) and low values (cold spots) across your study area, often using measures like Getis-Ord Gi* or local Moran’s I. By comparing observed concentrations to a randomized baseline, it flags locations where high pollutant levels are not just random fluff but part of a real, spatially coherent pattern. This makes it the most direct tool for pinpointing where pollution is truly concentrated.

Buffer analysis focuses on distances around features, not on clustering of values. Overlay analysis combines layers to create new data but doesn’t identify concentration patterns. Interpolation builds a smooth surface from sample points to estimate values at unsampled locations; it shows where concentrations might be high, but it doesn’t inherently test whether those high values form statistically significant hotspots—additional hotspot analysis is needed to confirm that.