Spatio-temporal assessment of urban environmental conditions in Ranchi Township, India using remote sensing and Geographical Information System techniques

The present study investigates the status of the urban environment in Ranchi, a rapidly growing city in the eastern part of India. The various environmental indicators viz., ambient air quality, aerosol concentration, ambient noise level and urban green space were analysed in a spatio-temporal framework by employing geoinformatics. The ambient air quality measurement indicates a high concentration of Suspended Particulate Matter (>300 μ g/m-super-3) and Respirable Suspended Particulate Matter (>200 μ g/m-super-3), as well as low level concentrations of sulphur dioxide (>60 μ g/m-super-3) and nitrogen dioxide (>60 μ g/m-super-3) in Ranchi Township. The concentration of ambient air pollutants was significantly higher in Ranchi as compared to other major urban centres of Jharkhand. The spatial distribution of aerosol optical depth (AOD) indicated variation with high concentrations at transportation junctions (0.30-0.35% at 340 nm) and road junctions (>0.30% at 340 nm), and low concentrations (>0.22% at 340 nm) at planned residential areas. The AOD concentration in Ranchi was lower (>0.35% at 340 nm) compared to the Patratu coal mining-cum-industrial region (>0.8% at 340 nm). The majority of the locations in Ranchi exhibited ambient noise levels above the prescribed limits with an increasing trend from 2005 to 2010. The core urban area was the noisier one (>65 dB(A)) when compared to the peripheral areas in the city. The spatial assessment of urban green space derived from WorldView-II satellite data indicated the existence of adequate green spaces (12.7%) within Ranchi Township, although urban cores are largely devoid of green space due to dense built-up land. The study exhibited that vegetation significantly contributes in noise attenuation and a reduction in aerosol concentration.