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

Abstract

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 Bárðarbunga volcanic eruption was the largest in Iceland for more than 200 years and it released into the atmosphere an average of 60 kt/day SO2, 30 kt/day CO2, 500 t/day HCl and 280 t/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 Bárðarbunga 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 CO2. The highest concentrations of volatiles in the snow cores were found close to the eruption site as predicted from CALPUFF SO2 gas dispersion quality model. The anion concentrations (mainly SO4, 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 SO4 and Cl concentrations in the snow compared with the unpolluted rainwater of marine origin confirms the addition of a non−seawater SO4 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 SO4, 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 3.7 µmol/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. This minor environmental impact evidenced by the microbial communities identified in the snow that fell during the eruption. These communities were similar to those found in snow from other parts of the Arctic, confirming an insignificant impact of this eruption the snow microecology.

Seasonality of Glacial Snow and Ice Microbial Communities

“…We found seasonal differences in the major macro- and micronutrients that are relevant for catabolic and anabolic cell processes ( Goldman et al, 2012 ), for co-factors for enzyme activity, and that are used in anti-freeze protection mechanisms ( Garnham et al, 2011 ). The concentrations of major dissolved ions in all our snow and ice samples ( Table 2 ), fell within the range of concentrations reported in previous studies for Iceland snow and ice samples ( Lutz et al, 2015a ; Galeczka et al, 2017 ). In most cases, the ion concentrations were higher during winter than summer regardless of habitat (i.e., bare ice or snow; Table 2 ).…”

“…The high DOC concentrations measured in our summer 2018 snow samples (between 4 and 20 ppm, Table 2 ) are at the upper-most range of what has previously been measured for glacial ice ( Hood et al, 2015 ), exceeding typical glacial snowpack and glacial outflow concentrations ( Singer et al, 2012 ; Stubbins et al, 2012 ; Yan et al, 2016 ), and are largely in line with measured DOC concentrations in green snowpacks (i.e., snow containing abundant Chlorophyta ) in Svalbard ( Lutz et al, 2015b ), and in ice samples from Antarctica ( Barker et al, 2006 ). We suggest that the relatively high DOC concentrations in our samples compared to others ( Singer et al, 2012 ; Stubbins et al, 2012 ; Hood et al, 2015 ; Yan et al, 2016 ) could arise from (i) our sampling at the end of the summer season (i.e., ~mid-September 2018) compared to other studies sampling between May and August ( Singer et al, 2012 ; Stubbins et al, 2012 ; Wright et al, 2013 ; Lutz et al, 2015a , b ; Yan et al, 2016 ), and (ii) the relatively high nutrient loading (and therefore high primary productivity) experienced by Icelandic glaciers due to volcanic input ( Bagnato et al, 2013 ; Galeczka et al, 2017 ).…”

Fractional degassing of S, Cl and F from basalt magma in the Bárðarbunga rift zone, Iceland

“…The large amount of gas emission from Holuhraun caused repeated air pollution events characterized by atmospheric SO2 concentrations exceeding air quality standards, as well as high concentrations of fine-grained volcanogenic aerosols (Ilyinskaya et al, 2017;Stefánsson et al, 2017). Snow precipitated around the lava field, rain and the surrounding rivers were monitored during the eruption and had elevated F concentrations (Gíslason et al, 2015;Galeczka et al, 2017;Stefánsson et al, 2017) despite its very low abundance in the main gas plume (Gauthier et al, 2016). Understanding the origin and fate of fluorine during degassing processes is thus of importance in order to assess its release to the atmosphere and subsequent environmental impact.…”