Aerosol characteristics during winter fog at Agra, North India

Abstract

Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO 4 2− , NO 3 − , NH 4 + and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH 4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 µm). AOD value at 0.5 µm wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m 2) than that during clear sky or less foggy/hazy days (+38 W/m 2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m 2 during clear sky or less foggy/hazy days to −76 W/m 2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO 4 2- .

Water Soluble Ionic Species in Atmospheric Aerosols: Concentrations and Sources at Agra in the Indo-Gangetic Plain (IGP)

“…Chemical characterization of aerosols, their mass size distribution studies and its variation in different seasons at Dayalbagh, Agra has also been reported by Kumar et al (2007). Earlier study by Safai et al (2008) at Agra reported chemical characterization of aerosols only during a specific land campaign (December 2004) for intense foggy or hazy days. In this paper, a systematic study of chemical characterization of water soluble fraction of TSP matter has been presented with data from two consecutive years (2009)(2010) and seasonal variation has also been discussed.…”

“…Several researchers have attempted to study the chemical composition and mass size distribution of atmospheric aerosols at different places (Shrestha et al, 2000;Wu et al, 2006;Pio et al, 2008;Stone et al, 2011;Hu et al, 2012;Tsai et al, 2012). In India also, studies on chemical characterization and mass size distribution of water soluble ionic constituents in aerosols have been conducted (Khemani et al, 1985;Safai et al, 1993;Tripathi et al, 1996;Kumar et al, 2003;Rastogi and Sarin, 2005;Kumar et al, 2006;Safai et al, 2008;Kulshrestha et al, 2009;Safai et al, 2010;Deshmukh et al, 2011;George et al, 2011;Ram et al, 2012). Few studies have been carried out in the IndoGangetic plain to characterize TSP (Kulshrestha et al, 1998;Parmar et al, 2001;Kumar et al, 2007;Ram et al, 2010;Ram et al, 2012).…”

Wintertime Variation of Black Carbon in PM2.5 Aerosols Over an Urban Industrial City in East-Central India

“…Aruna et al [32] found about two times higher nighttime value than daytime at Chennai. As per available literature, some cities also have high BC mass loading during nighttime: Dhanbad [31] and Agra [33].…”

Mixing state of individual submicron carbon-containing particles during spring and fall seasons in urban Guangzhou, China: a case study

“…Through the fog processing, OC, ECOC, V-ECOC and EC-Sulfate were generally enhanced with the secondary inorganic species (sulfate, nitrate and/or ammonium). The enhanced secondary inorganic species in aerosols were commonly observed throughout the foggy episodes (Biswas et al, 2008;Safai et al, 2008). However, the EC-fresh and Biomass particles were probably freshly emitted more during the episode, so there was no obvious variation of the secondary species in their mass spectra.…”