Influence of peat fires on the rainwater chemistry in intra-mountain basins with specific atmospheric circulations (Eastern Carpathians, Romania)

A comprehensive study on the chemical composition of precipitation, the influence of peat fires and their relations with atmospheric circulation was conducted in the year of 2012, in two intra-mountain basins, the Ciuc basin (CB) and the Giurgeu basin (GB), Eastern Carpathians, Romania. Atmospheric circulation types showed the presence of a westerly anticyclonic circulation, characterized by a strong development of the Azores High to the northern Atlantic, contributing to the appearance of peat-fires. Using ROCADA daily gridded climatic datasets, the maximum and minimum daily temperatures were extracted, showing deviation from 2 °C to 6 °C in the studied year against the multiannual mean for the 1981–2016 period. Rainwater samples were analyzed for pH, major anions and cations; HCO3− concentrations were calculated based on the empirical relationship between pH and HCO3−. The results showed that 45.16% and 54.55% of precipitation had pH > 7.0 at CB and GB, respectively. NH3, NH4+ and Ca2+ are the main neutralizing agents. The significant correlation between SO42− and NH4+ (r = 0.711 – CB; r = 0.736 – GB) indicated neutralization by NH3 in the forms of (NH4)2SO4 and NH4HSO4. Positive regression coefficient between the sum of (H+ + [NH4+] + [Ca2+]) and the sum of ([nss − SO42−] + [NO3−]) (r = 0.855 – CB; r = 0.796 – GB), showed that acid neutralization was primarily brought by NH4+ and/or CaCO3. Using Na as an indicator of marine origin, the proportions of sea salt and non-sea-salt were estimated from elemental ratios. According to correlation analysis and PCA, main acidic ions (SO42− and NO3−) and NH4+ were mainly derived from anthropogenic activities (biomass burning, peat fires, fertilization), while Ca2+ and Mg2+ originated from terrestrial sources. The behavior of gaseous pollutants and smoke distribution resulted from peat fires were deciphered using the HYSPLIT model in a case study. [Display omitted] •Temperature at 850 hPa for 2012 showed deviations with 2 °C–4 °C greater than for 1981–2016.•55% (CB) and 27% (GB) decrease in rainfall amount in 2012 compared to the multiannual mean (2006–2016).•Acidity of rainwater is mainly neutralized by NH4+, soil dust and CaCO3.•pH increases due to NH3 in cloud droplets, resulting below-cloud scavenging of SO2.•W-NW wind direction had the highest frequency, confirming the westerly anticyclonic circulation.