Pollution from the 2014–15 Bárðarbunga eruption monitored by snow cores from the Vatnajökull glacier, Iceland

The chemical composition of Icelandic rain and snow is dominated by marine aerosols, however human and volcanic activity can also affect these compositions. The six month long 2014-15 Bárdarbunga volcanic eruption was the largest in Iceland for more than 200years and it released into the atmosphere an average of 60kt/day SO 2 , 30kt/day CO 2 , 500t/day HCl and 280t/day HF. To study the effect of this eruption on the winter precipitation, snow cores were collected from the Vatnajökull glacier and the highlands northeast of the glacier. In addition to 29 bulk snow cores from that precipitated from September 2014 until March 2015, two cores were sampled in 21 and 44 increments to quantify the spatial and time evolution of the chemical composition of the snow.The pH and chemical compositions of melted snow samples indicate that snow has been affected by the volcanic gases emitted during the Bárdarbunga eruption. The pH of the melted bulk snow cores ranged from 4.41 to 5.64 with an average value of 5.01. This is four times greater H + activity than pure water saturated with the atmospheric CO 2 . The highest concentrations of volatiles in the snow cores were found close to the eruption site as predicted from CALPUFF SO 2 gas dispersion quality model. The anion concentrations (SO 4 , Cl, and F) were higher and the pH was lower compared to equivalent snow samples collected during 1997-2006 from the unpolluted Icelandic Langjökull glacier. Higher SO 4 and Cl concentrations in the snow compared with the unpolluted rainwater of marine origin confirm the addition of a non-seawater SO 4 and Cl. The δ 34 S isotopic composition confirms that the sulphur addition is of volcanic aerosol origin.The chemical evolution of the snow with depth reflects changes in the lava effusion and gas emission rates. Those rates were the highest at the early stage of the eruption. Snow that fell during that time, represented by samples from the deepest part of the snow cores, had the lowest pH and highest concentrations of SO 4 , F, Cl and metals, compared with snow that fell later in the winter. Also the Al concentration, did exceed World Health Organisation drinking water standard of 3.7μmol/kg in the lower part of the snow core closest to the eruption site.Collected snow represents the precipitation that fell during the eruption period. Nevertheless, only minor environmental impacts are evident in the snow due to its interaction with the volcanic aerosol gases. In addition, the microbial communities identified in the snow that fell during the eruption were similar to those found in snow from other parts of the Arctic, confirming an insignificant impact of this eruption on the snow microecology

Ground-Based Measurements of the 2014–2015 Holuhraun Volcanic Cloud (Iceland)

The 2014–2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO2, with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios SO2/HCl = 30–110 and SO2/HF = 30–130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3–5.5 km agl were measured with ground- and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting