Lichen Biomonitoring of Air Quality Using API, AQI, HII and Environmental Impact in Djelfa, a Semi-Arid Region

Air quality in steppe environments can be assessed using lichen biodiversity and environmental variables, which are excellent bioindicators. This study uses biomonitoring techniques to assess and map air pollution levels in the province of Djelfa, while identifying species sensitive to air contamination. The analysis focused on epiphytic corticolous lichens in 36 communes of the province of Djelfa, with samples taken at 121 stations distributed between forests, urban areas and main roads, reflecting different levels of exposure to pollutants. Three indices were used to quantify pollution: the Atmospheric Purity Index (API), the Air Quality Index (AQI) and the Human Impact Index (HII). Twenty-two (22) species of corticolous lichens were identified, mainly foliaceous and crustaceous thalli. The values obtained for the API ranged from (0-44.965), the AQI from (0-27.533) and the HII from (2-28), revealing strong spatial variability, with pollution levels significantly higher in urban and road areas than in forested areas. The results of the statistic analysis (PCA, RDA, Monte Carlo test) demonstrate the influence of environmental factors and arid to semi-arid climatic conditions on lichen diversity, confirming their usefulness as bioindicators, and indicate a marked deterioration in air quality as one moves away from forests. This study contributes to a better understanding of the impact of human activity on ecosystems in arid environments.