Abstract
Lichens, which are symbiotic associations between fungi and algae, serve as bioindicators for assessing air quality via the Modified Index of Atmospheric Purity (IAPM). This research evaluated atmospheric conditions and mapped isocontamination zones in Chachapoyas, Peru. Lichen samples were collected from 36 locations across six urban sectors, while measurements of phorophyte bark pH, ambient temperature, and humidity were also taken. A total of 27 lichen species on 15 phorophyte species were identified. Statistical analysis found no significant correlation between IAPM scores and environmental factors such as bark pH, phorophyte species, temperature, or humidity. Using the IAPM data and Kriging interpolation in QGIS, an isocontamination map was created to display spatial air pollution patterns. The map indicated that the central sector of Chachapoyas had the lowest air quality, while peripheral areas showed decreasing pollution levels, illustrating a clear urban pollution gradient.