June 05, 2014: Talk: "Aerosol Chemical Characterization: An Indian Scenario"

10:00 - 11:00 AM

Grosser Konferenzraum, GEOMAR, Düsternbrooker Weg 20

Abstract:

Atmospheric aerosols play an important role in regional air quality, public health, atmospheric chemistry and climate change especially over East Asia.  They are produced from various natural and anthropogenic sources and have significant direct radiative impact through absorption and scattering of incoming radiation. It comprises a mixture of sulfates, nitrates, carbonaceous particles, sea salt and mineral dust.
Carbonaceous matter constitutes a large fraction of atmospheric aerosols and it plays a major role in air pollution, visibility, health and climate effects.
The carbonaceous matter consists of organic carbon (OC) and elemental carbon (EC).
Elemental carbon is a primary pollutant emitted from incomplete combustion of fossil fuel and biomass. It is the dominant light absorbing species and the second largest contributor to global warming, after greenhouse gases while OC can be either released directly into the atmosphere from anthropogenic and biogenic sources (primary OC, POC) or formed within the atmosphere through gas-to-particle conversion of volatile organic compounds through photochemical reactions (secondary OC, SOC) .
The high loading of carbonaceous aerosols in fine particles has also been identified as the important factor in climate change, urban haze formation, crop production and atmospheric chemical reactions.

A continuous measurement of PM2.5 for chemical characterization was carried out at a suburban site of North central region of India.
Carbonaceous aerosols as well as water soluble inorganic constituents were analyzed.
Most of the water soluble ions such as F, Cl, NO3, SO4, NH4 and K, had the highest mass concentrations in winter, while higher mass concentrations of Ca and Mg were found in summer.
The acidity in aerosols is neutralized by the alkaline species, as indicated by the correlation between NO3 and SO4 and sum of (Ca, Mg and NH4).
Ca is the major acid neutralizing cation in the aerosols, followed by Mg and NH4.
Both OC and EC exhibited a clear seasonal pattern with highest concentration observed in winter followed by summer and monsoon which may be due to the combined effect of changes in emission rates and different meteorology.
The SEM/EDX analysis revealed the dominance of carbonaceous particles during winter season which is also supported by back trajectory analysis which shows that the origin of these particles is mainly anthropogenic in nature.