Multi-pollutant air quality analyses and apportionment of sources in three particle size categories at Taj Mahal, Agra

Abstract

Taj Mahal, an iconic monument at Agra, India, is faced with the high air pollution levels, affecting its facade. A study was undertaken at the Taj Mahal (June 7–26, 2018) to measure PM2.5, PM10, TSP and their chemical composition: metals, ions, elemental and organic carbons and molecular markers (polyaromatic hydrocarbons, n-alkanes, hopanes and sterols). The objectives of the study were to (i) assess the contribution of sources to PM2.5, PM10 and TSP by employing receptor modelling (USEPA's Chemical Mass Balance model 8.2) and (ii) measure levels of reactive (NH3, SO2, NO2), acidic (HCl, HNO3) and corrosive (H2S) gases.The PM levels were: PM2.5 65 ± 13; PM10 234 ± 84 and TSP 465 ± 204 μg/m3. The percent mass of metals (32–39) was the maximum in all PM size categories followed by secondary inorganic aerosol (SIA; 6–21). PM2.5 had a substantial contribution to coal combustion and fly ash (35%), followed by vehicles (19%). The contribution of soil and road dust was maximum to PM10 (39%) and TSP (61%), followed by the contribution of coal and fly ash in PM10 (34%) and TSP (22%). The presence of HCl (9.44 ± 4.61 μg/m3) suggested the contribution of burning of coal, plastic, paper and waste. The other concern was levels of NH3 (30 ± 14 μg/m3), which adds to the formation of SIA. The major source of NH3 could be from the upstream discharges of partially treated sewage in the River Yamuna, flowing adjacent to the Taj Mahal.