Asian Journal of Physical and Chemical Sciences

Air-quality research in India has predominantly focused on large metropolitan regions, leaving plateau-based Tier-II cities comparatively underexamined. This study assessed the spatio-temporal variability of air quality across five land-use zones in Ranchi, Jharkhand: industrial, traffic, residential, agricultural, and eco-sensitive. Monthly observations collected during 2022–2023 yielded 120 site-month records, and the National Air Quality Index framework was applied to PM₂.₅, PM₁₀, SO₂, and NO₂. Site-level differences were evaluated using one-way analysis of variance, while dominant-pollutant regimes and seasonal patterns were examined to identify spatial and temporal contrasts. Mean AQI differed significantly among sites (F(4, 115) = 11.04, p < 0.001). The traffic site recorded the highest mean AQI (267.7 ± 27.2), followed by the industrial site (243.2 ± 16.9), indicating sustained pollution pressure in high-emission zones. The eco-sensitive site recorded a higher mean AQI (175.1 ± 105.4) than the residential site (158.6 ± 58.0), suggesting that local vegetation did not consistently prevent episodic deterioration. PM₂.₅ was the most frequent AQI-determining pollutant, particularly at the traffic and industrial sites, whereas PM₁₀ governed several abrupt episodes at the agricultural and eco-sensitive locations. Winter generally showed the highest and most variable AQI, while the monsoon produced lower and less dispersed values, reflecting seasonal differences in pollutant accumulation and removal. Overall, the findings demonstrate marked land-use and seasonal heterogeneity in Ranchi. They further indicate that air-quality monitoring and management should address both persistent emissions at traffic and industrial locations and episodic pollution affecting peri-urban, agricultural, and eco-sensitive zones within the rapidly expanding plateau-based urban environment.