A 1 year record of carbonaceous aerosols from an urban site in the Indo‐Gangetic Plain: Characterization, sources, and temporal variability

Abstract

) data set on the chemical composition of ambient aerosols collected from an urban location (Kanpur) in the Indo-Gangetic Plain (IGP) and suggests that the varying strength of the regional emission sources, boundary layer dynamics, and formation of secondary aerosols all contribute significantly to the temporal variability in the mass concentrations of elemental carbon (EC), organic carbon (OC), and water-soluble OC (WSOC). On average, carbonaceous aerosols contribute nearly one third of the PM 10 mass during winter, whereas their fractional mass is only ∼10% during summer. A three-to four-fold increase in the OC and K + concentrations during winter and a significant linear relation between them suggest biomass burning (wood fuel and agricultural waste) emission as a dominant source. The relatively high OC/EC ratio (average: 7.4 ± 3.5 for n = 66) also supports that emissions from biomass burning are overwhelming for the particulate OC in the IGP. The WSOC/OC ratios vary from 0.21 to 0.70 over the annual seasonal cycle with relatively high ratios in the summer, suggesting the significance of secondary organic aerosols. The long-range transport of mineral aerosols from Iran, Afghanistan, and the Thar Desert (western India) is pronounced during summer months. The temporal variability in the concentrations of selected inorganic constituents and neutralization of acidic species (SO 4 2− and NO 3 − ) by NH 4 + (dominant during winter) and Ca 2+ (in summer) reflect conspicuous changes in the source strength of anthropogenic emissions.Citation: Ram, K., M. M. Sarin, and S. N. Tripathi (2010), A 1 year record of carbonaceous aerosols from an urban site in the Indo-Gangetic Plain: Characterization, sources, and temporal variability,

Carbonaceous and Secondary Inorganic Aerosols during Wintertime Fog and Haze over Urban Sites in the Indo-Gangetic Plain

“…3). In addition, mass concentrations of OC and EC at Hisar and Allahabad are also similar with a recent data acquired during the wintertime from Kanpur, an urban site located at the center of the IGP (Ram et al, 2010a). However, mass concentrations of OC and EC at urban sites in the IGP are an order of magnitude higher compared to those at high-altitude site (Manora Peak) in the central Himalaya (Ram et al, 2010b).…”

“…of replicate analyses of water-extracts for K + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− and NO 3 − were better than 3% while it was ~6% for NH 4 + analysis (n = 4). All the reported data of carbonaceous species (EC, OC and WSOC) and inorganic ionic constituents (cations and anions) are corrected for their respective procedural blanks (Ram and Sarin, 2010;Ram et al, 2010a). 23.3 ± 7.1 31.5 ± 7.6 24.1 ± 4.1 11.7 ± 2.9 26.8 ± 9.7 17.4 ± 6.2 SO 2 (μg/m 3 ) ## 11.0 ± 1.7 15.6 ± 4.6 17.2 ± 10.9 # Classification of fog, haze events and clear days as per Ramachandran et al (2006); Lal et al (2008).…”

“…Among the major sources of aerosol, emissions from agricultural-waste and biomass burning dominate during the wintertime (Dec-Feb) (Venkataraman et al, 2005;Rengarajan et al, 2007;Gustafsson et al, 2009;Ram et al, 2010a;Shakya et al, 2010;Rajput et al, 2011;Ram and Sarin, 2011). The transport of mineral aerosol from arid and semiarid regions of western India, during the summer (Aprilearly June), imparts strong temporal variability in the chemical composition and optical properties of aerosol (Jethva et al, 2005;Chinnam et al, 2006).…”

“…The formation of fog and haze is associated with high aerosol loading from anthropogenic sources as well as formation of secondary aerosols via gas-to-particle conversion under favorable meteorological conditions (Reilly et al, 2001;Husain et al, 2004;Sun et al, 2006;Fang et al, 2011;). Recent studies suggest that a significant fraction of atmospheric particulate matter (PM) in the Indo-Gangetic Plain are comprised of carbonaceous aerosol (~30-35% of the PM) and water-soluble inorganic species (~10-20% of the PM) over IGP and other locations in India Rengarajan et al, 2007;Ram et al, 2010a;Deshmukh et al, 2011;Kothai et al, 2011). During the wintertime, low ambient temperatures (range: ~10-20°C, at times dipping as low as 5°C) and weak winds (< 2 m/s) and boundary layer height (~500-800 m) favour stable atmosphere, leading to poor convective mixing and accumulation of pollutants in the lower atmosphere (Nair et al, 2007;Ram et al, 2010a).…”

CCN closure study: Effects of aerosol chemical composition and mixing state

“…The estimated distance of the fire hot spots (shown in Figure 1) from the sampling location is approximately 700-1000 Km. More details on the sampling location are provided elsewhere [Ram et al, 2010a].…”