Ionic composition of six-year daily precipitation samples collected at JRC-Ispra (Italy) in relation to synoptic patterns and air mass origin

A six-year dataset of daily precipitation samples collected and analyzed at the rural background station of Joint Research Center (JRC) at Ispra (Italy), was studied in conjunction with synoptic patterns and Concentration Weighted Trajectory (CWT) model in order to identify atmospheric mechanisms and transport pathways affecting the concentrations of eight major inorganic ions: NO -3 , Cl-, Na+, Mg2+, Ca2+, SO2-4 , NH+4 and K+. A Principal Component Analysis (PCA) distributed the studied constituents to three categories reflecting major emission sources: a) Anthropogenic b) Sea salt and c) Crustal. The concentrations of all ions in precipitation samples were negatively correlated with precipitation amounts, however the negative correlations were more enhanced for species having a mainly anthropogenic origin (NO -3 , SO2-4 , NH+4 and K+). The anthropogenic constituents were transported mainly from continental Europe, while the primary role of emissions in the industrialized Po Valley was highlighted from the impact of Eastern airflows on NO -3 , SO2-4 , NH+ 4 and K+ levels. In addition, a secondary Saharan dust source for SO2-4 was verified. Sea salt species (Cl-, Na+ and Mg2+) were originated from the Mediterranean Sea, the North Sea, the Baltic Sea, and possibly from the Atlantic through France, while Saharan dust intrusions clearly enhanced the levels of crustal constituents (Ca2+ and Mg2+). The elaboration of a multi-year precipitation dataset for the first time with CWT model, provided new insights regarding the emission sources and transport mechanisms affecting the ionic composition of precipitation samples collected at JRC-Ispra.

Automated summary

This study analyzed a six-year dataset of daily precipitation samples collected in rural Italy in conjunction with synoptic patterns and the Concentration Weighted Trajectory (CWT) model. The aim was to identify atmospheric mechanisms and transport pathways affecting the concentrations of major inorganic ions. The study found that the concentrations of all ions were negatively correlated with precipitation amounts. Anthropogenic constituents primarily originated from continental Europe, while sea salt species came from various seas surrounding Italy and Saharan dust intrusions increased the levels of crustal constituents.