Major impact of volcanic gases on the chemical composition of precipitation in Iceland during the 2014–2015 Holuhraun eruption

The holuhraun eruption in 2014–2015 was the largest in iceland for more than 200 years. it resulted in emissions of large quantities of volcanic gases into the atmosphere (11 megaton (mt) so_2,0.1 mt hcl, and 0.05 mt hf). during the eruption the volcanic gases had major effects on f, so_4 and to a lesser extent cl concentrations in precipitaxtion throughout iceland, effects not observed in recent decades. the concentrations of f, cl, and so_4 (n = 705) reached values of 444 μm 12,270 μm, and 17,324 μm during the eruption and were on average ~20 times higher for f and so_4 and much lower for cl compared to preeruption times. the concentrations of major cations (si, na, k, ca, mg, al, and fe) (n = 151) in the precipitation were taken as having originated from seawater spray and dissolution of rock dust and aerosol. based on the mixing model developed here, it is demonstrated that the source of the enrichment of f and so_4 was indeed the volcanic gas emissions with >60–100 mol % of so4 and f in the precipitation originated from volcanic gas, whereas the cl originated mostly from seawater spray, making the volcanic gas input of cl relatively less important than for f and so_4. the results showed that large volcanic eruptions can have major effects on atmospheric chemistry and impact the composition of precipitation.