Assessment of particulate matter variation during 2011-2015 over a tropical station Agra, India

Air quality over Agra is deteriorating and causing a serious threat to people residing in the city as well as to World heritage site- Tajmahal. In the present study, daily average concentrations of Suspended Particulate Matter (SPM) and Respirable Suspended Particulate Matter (RSPM) were analysed over a period of 2011-2015 at four stations in Agra city, namely: Taj, Itmad-Ud-Daula, Rambagh and Nunhai. The concentrations are above threshold values when compared to specify standards for a healthy environment (by India, US, WHO, EU and China - Class I and Class II) for all the seasons except monsoon and the values are highest in the month of November and lowest in the month of August and September. Variation of RSPM and SPM were found to be positively correlated with each other with values of 0.76 (Taj), 0.72 (Itmad-Ud-Daula), 0.69 (Rambagh), 0.77 (Nunhai). The study illustrates that the levels of SPM and RSPM are not showing any decreasing trend over Agra even after closing of industries and taking other precautions inside the city by Government of India. The study clearly identifies that local control of pollution sources are not enough and pollution is being transported from nearby regions to keep the daily pollution value higher than threshold. Source regions of transported pollutants over Agra have been analysed by using Weighted Potential Source Contribution Function (WPSCF) for both SPM and RSPM. Wavelet analysis of monthly averaged values of RSPM and SPM data sets has shown the existence of semi-annual and annual periodicity over the study region.