Long-Term Changes of Particulate Emission in the Industrial Region of Upper Silesia (Poland) and their Effect on the Acidity of Rainwater

The article presents data from ten-year measurements, which provethat the positive effects in particulate emission were accompanied by some adverse effects in the form of acidified rainwater. A distinctive change of rainwater pH in the SilesiaRegion (Poland) was first recorded in the early 90's. While in 1989, pH of over 55% of the investigated rainwater samples wasabove 6, in 1997 the average yearly pH was 4.1 and the pH of20%of the investigated samples was in the range of 3.1–4.0. Seekingthe reason for an increased acidity of rainwater, pH values were compared with emission changes of particulate, SO₂ and NO₂ acrossthe studied area. Emission factors of Ca, Mg, Na and K were determined based on the data of particulate matter emission fromcement production processes, coal combustion processes and metallurgy. This allowed comparing the changes of pH rainwater with the area emissions of alkali elements. An analysis of thecorrelation between pH values and the changes of particulatematter and alkali elements emission as well as SO₂ and NO₂ emission in the area under study showed that particulate emission followed by SO₂ emission had the strongest impact onthe modification of rainwater pH, while the impact of NO₂ emission was less distinctive. Additionally, an analysis was made to investigate the relationbetween rainwater pH and the concentration of alkaline ions inrainwater samples. The highest value r = 0.96 was recorded forMg²⁺ ions, the lowest i.e. r = 0.54 for Ca²⁺ ions.This situation can be explained by the fact that calciumcompounds are the soluble substances among the investigatedmetals. Thus, despite the presence of calcium compounds inrainwater samples, a large amount of their portion does notinfluence rainwater pH.