engleski

Seasonal Distributions of Acid Components in PM2.5 Fraction of Airborne Particles in Zagreb Air

It is well known that airborne particles and their constituents are associated to adverse health effects, reduction of visibility and the soiling of buildings (Schwartz 1994 ; Gamble and Lewis 1996, Lippmann and Thurston 1996 ; Harrison et al. 1997). The acidity of the particle has been supposed to be the crucial factor (Lippmann and Thurston 1996). Acid aerosols in the air are formed primarily from the oxidation of sulphur oxides, nitrogen oxides and hydrocarbons, mainly originating from combustion sources. In the atmosphere the primary pollutant sulphur dioxide is oxidized by both homogenous and heterogenous reactions forming a sulphuric acid aerosol, which can react rapidly with other components present in the air mainly with gaseous ammonia, leading to various molecular forms of sulphates (Brook et al. 1997). Nitrogen dioxide (mainly the secondary pollutant) is readily oxidized to nitrates. Nitrates may be present in the gaseous phase as nitric acid vapor, while the sulphates are mainly found in the aerosol phase (Wyers and Duyzer 1997). Aerosol acidity and concentrations of each species are seasonally dependable, varying with the time of the day and location. Summer aerosols are more acid compared to those collected during winter period. Strong acids are more frequently present in fine (high-risk) particle fraction compared to the coarse one. This paper presents seasonal mass concentration and content distributions of acid anions (chlorides, nitrates, sulphates) in high-risk particle fraction (PM2.5 – particles with equivalent an aerodynamic diameter less than 2.5 mm) in Zagreb ambient air.

Pollution; Sulfate; Health; Urban

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