Long-term trends and factors influencing rainwater chemistry in the Tatra Mountains, Poland

The results of rainwater chemistry monitoring in the Tatra Mountains, Poland, during the periods 1993–1994 and 2002–2019 were used to determine long-term trends and the factors influencing rainwater chemistry in the last two decades. In the early 1990’s, the study area was characterized by prominent acid rains with a pH of 4.4 that affected surface water, meadows, and forest ecosystems. A rising pH temporal trend has been observed during the following years, indicating improving air quality. This trend has also been observed in measured ionic concentrations and reduced wet deposition loads of sulfur- and nitrogen-containing acid-forming compounds. The neutralization capacity of rainwater in Kasprowy Wierch increased over the last twenty years and has mostly been dominated by NH4+. The ammonium availability index has been steadily increasing between years 2002 and 2019 but remains less than 1. This statistically significant relationship also indicates that a portion of neutralization occurs in the lower part of the atmosphere due to ammonium-related neutralization processes. The acidic potential (AP) and the ratio AP/NP (acidic potential/neutralization potential) have been declining during the same time. The stated trends in rainwater chemistry reflect the transformation to more environmentally sustainable economies in the region. Similar changes have been observed in neighboring countries in the region, including Slovakia, the Czech Republic, and Lithuania.