Precipitation composition and wet deposition temporal pattern in Central Serbia for the period from 1998 to 2004

Abstract

Bulk samples collected on a daily basis at three principal meteorological stations in central Serbia were analyzed on chloride (Cl⁻), nitrate ${\left( {{\text{NO}}^{ - }_{3} } \right)}$, sulfate ${\left( {{\text{SO}}^{{2 - }}_{4} } \right)}$, sodium (Na⁺), ammonium ${\left( {{\text{NH}}^{ + }_{4} } \right)}$, potassium (K⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) in addition to precipitation amount, pH and conductivity measurements over the period 1998–2004. The data were subjected to variety of analyses (linear regression, principal component analysis, time series analysis) to characterize precipitation chemistry in the study area. The most abundant ion was ${\text{SO}}^{{2 - }}_{4}$ with annual volume weighted mean concentration of 242 μeq L⁻¹. Neutralization of precipitation acidity occurs both as a result of the dissolution of alkaline compounds containing Ca²⁺, Mg²⁺, and K⁺ as well as the absorption of ammonia. The ratio of ${{\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}} } \mathord{\left/ {\vphantom {{{\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}} } {{\text{NO}}^{{\text{ - }}}_{{\text{3}}} }}} \right. \kern-\nulldelimiterspace} {{\text{NO}}^{{\text{ - }}}_{{\text{3}}} }$ was above 5, which indicated that the combustion process of low-grade domestic lignite for electricity generation from coal-fired thermal power plants was the main source of pollution in the investigated area. A considerable mean annual bulk wet deposition of SO₄–S determined by precipitation amount and concentrations of sulfate in the precipitation was calculated to be 12–35 kg ha⁻¹.