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Aerosol acidity and secondary organic aerosol formation during wintertime over urban environment in western India
Abstract Atmospheric mass concentration of ambient PM2.5, its chemical composition and aerosol acidity have been studied during the wintertime from an urban site in a semi-arid region of western India. The concentration of PM2.5 ranged from 32 to 106 μg m−3 during the 30-day sampling period; and carbonaceous species (EC, OC) and water-soluble inorganic constituents (WSIC) account for ∼58% and ∼29% of the mass, respectively. The contribution of SO4 2− to PM2.5 is significant (Average: 17.5%) and that of NO3 − is minor (Average: ∼2%). The ratio of water soluble to particulate organic carbon (WSOC/OC) varies from 0.26 to 0.52 (Average: 0.41) and provides evidence for the significant role of secondary organic aerosol (SOA) in an urban environment. Measured concentration of [H+]air, used as an index of aerosol acidity, varies from 0.25 to 11 μmol m−3 and exhibits linear increase with the secondary organic carbon (SOC). Our field-based data provide the direct evidence for enhanced SOA formation at high level of acidity, consistent with laboratory studies.
Research highlights ► In a semi-arid urban site from western India, PM2.5 mass ranged from 32 to 106 μg m−3 during winter. ► (EC + OC) and water-soluble inorganic constituents (WSIC) account for ∼58% and ∼29%, respectively. ► Contribution of SO4 2− is significant (Average: 17.5%) in WSIC and that of NO3 − is minor (∼2%). ► Concentration of [H+]aerosol, an index of aerosol acidity, exhibits linear increase with SOC.
Aerosol acidity and secondary organic aerosol formation during wintertime over urban environment in western India
Abstract Atmospheric mass concentration of ambient PM2.5, its chemical composition and aerosol acidity have been studied during the wintertime from an urban site in a semi-arid region of western India. The concentration of PM2.5 ranged from 32 to 106 μg m−3 during the 30-day sampling period; and carbonaceous species (EC, OC) and water-soluble inorganic constituents (WSIC) account for ∼58% and ∼29% of the mass, respectively. The contribution of SO4 2− to PM2.5 is significant (Average: 17.5%) and that of NO3 − is minor (Average: ∼2%). The ratio of water soluble to particulate organic carbon (WSOC/OC) varies from 0.26 to 0.52 (Average: 0.41) and provides evidence for the significant role of secondary organic aerosol (SOA) in an urban environment. Measured concentration of [H+]air, used as an index of aerosol acidity, varies from 0.25 to 11 μmol m−3 and exhibits linear increase with the secondary organic carbon (SOC). Our field-based data provide the direct evidence for enhanced SOA formation at high level of acidity, consistent with laboratory studies.
Research highlights ► In a semi-arid urban site from western India, PM2.5 mass ranged from 32 to 106 μg m−3 during winter. ► (EC + OC) and water-soluble inorganic constituents (WSIC) account for ∼58% and ∼29%, respectively. ► Contribution of SO4 2− is significant (Average: 17.5%) in WSIC and that of NO3 − is minor (∼2%). ► Concentration of [H+]aerosol, an index of aerosol acidity, exhibits linear increase with SOC.
Aerosol acidity and secondary organic aerosol formation during wintertime over urban environment in western India
Rengarajan, R. (author) / Sudheer, A.K. (author) / Sarin, M.M. (author)
Atmospheric Environment ; 45 ; 1940-1945
2011-01-12
6 pages
Article (Journal)
Electronic Resource
English
Physical and chemical processes of wintertime secondary nitrate aerosol formation
| Springer Verlag | 2011