Mercury (Hg) is naturally released by volcanoes and geothermal systems, but the global flux from these natural sources is highly uncertain due to a lack of direct measurements and uncertainties with ...upscaling Hg/SO2 mass ratios to estimate Hg fluxes. The 2021 and 2022 eruptions of Fagradalsfjall volcano, southwest Iceland, provided an opportunity to measure Hg concentrations and fluxes from a hotspot/rift system using modern analytical techniques. We measured gaseous Hg and SO2 concentrations in the volcanic plume by near-source drone-based sampling and simultaneous downwind ground-based sampling. Mean Hg/SO2 was an order of magnitude higher at the downwind locations relative to near-source data. This was attributed to the elevated local background Hg at ground level (4.0 ng m−3) likely due to emissions from outgassing lava fields. The background-corrected plume Hg/SO2 mass ratio (5.6 × 10−8) therefore appeared conservative from the near-source to several hundred meters distant, which has important implications for the upscaling of volcanic Hg fluxes based on SO2 measurements. Using this ratio and the total SO2 flux from both eruptions, we estimate the total mass of gaseous Hg released from the 2021 and 2022 Fagradalsfjall eruptions was 46 ± 33 kg, equivalent to a flux of 0.23 ± 0.17 kg d−1. This is the lowest Hg flux estimate in the literature for active open-conduit volcanoes, which range from 0.6 to 12 kg d−1 for other hotspot/rift volcanoes, and 0.5–110 kg d−1 for arc volcanoes. Our results suggest that Icelandic volcanic systems are fed from an especially Hg-poor mantle. Furthermore, we demonstrate that the aerial near-source plume Hg measurement is feasible with a drone-based active sampling configuration that captures all gaseous and particulate Hg species, and recommend this as the preferred method for quantifying volcanic Hg emissions going forward.
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•Lowest mercury concentrations and fluxes reported for any active volcano on Earth•Iceland volcanic systems appear to be sourced from a particularly Hg-poor mantle.•Simultaneous near-vent and downwind data suggest Hg/SO2 is conserved over distance.•First drone-based measurements of plume gaseous mercury above an erupting volcano•Drone-based volcanic mercury sampling now feasible and should be the preferred method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
The 6-month-long 2014–2015 Holuhraun eruption was the largest in Iceland for
200 years, emitting huge quantities of sulfur dioxide (SO2) into the
troposphere, at times overwhelming European ...anthropogenic emissions. Weather,
terrain and latitude made continuous ground-based or UV satellite sensor
measurements challenging. Infrared Atmospheric Sounding Interferometer (IASI)
data are used to derive the first time series of daily
SO2 mass present in the atmosphere and its vertical
distribution over the entire eruption period. A new optimal estimation scheme
is used to calculate daily SO2 fluxes and average e-folding time
every 12 h. For the 6 months studied, the SO2 flux was observed to
be up to 200 kt day−1 and the minimum total SO2 erupted mass
was 4.4±0.8 Tg. The average SO2 e-folding time was
2.4±0.6 days. Where comparisons are possible, these results broadly agree
with ground-based near-source measurements, independent remote-sensing data
and values obtained from model simulations from a previous paper. The results
highlight the importance of using high-resolution time series data to
accurately estimate volcanic SO2 emissions. The SO2 mass
missed due to thermal contrast is estimated to be of the order of 3 % of
the total emission when compared to measurements by the Ozone Monitoring
Instrument. A statistical correction for cloud based on the AVHRR cloud-CCI
data set suggested that the SO2 mass missed due to cloud cover could
be significant, up to a factor of 2 for the plume within the first kilometre
from the vent. Applying this correction results in a total erupted mass of
6.7±0.4 Tg and little change in average e-folding time. The data set
derived can be used for comparisons to other ground- and satellite-based
measurements and to petrological estimates of the SO2 flux. It could
also be used to initialise climate model simulations, helping to better
quantify the environmental and climatic impacts of future Icelandic fissure
eruptions and simulations of past large-scale flood lava eruptions.
The 6-month-long effusive eruption at the Fagradalsfjall volcano in 2021 is the most visited eruption site in Iceland to date (June 2023), and it needed intense lava flow hazard assessment. In this ...study we document how strategies for lava flow modeling were implemented using the stochastic model MrLavaLoba to evaluate hazards during this effusive event. Overall, the purposes were threefold: (a) pre-eruption simulations to investigate potential lava inundation of critical infrastructure, (b) syn-eruption simulations for short-term (2-week time frame) lava flow hazard assessment and (c) syn-eruption simulations for long-term (months to years) hazard assessments. Additionally, strategies for lava barrier testing were developed, and syn-eruption topographic models were incorporated into simulations in near real time. The model provided promising results that were shared regularly at stakeholder meetings with the monitoring personnel, scientists and civil-protection representatives helping to identify potential short-term and long-term lava hazards. This included evaluation of the timing of barrier overflow and the filling and spilling of lava from one valley to another.
The volcanic origin, primarily basaltic, of most of the surface material in Iceland influences its physical properties and appearance. Size distributions, shape analyses and melting experiments were ...made for surface material collected in high‐erosion dust source areas and fresh volcanic ash deposits to determine whether they differ from one another and from dust from other major dust sources. The major differences found between Icelandic dust and dust from other major dust sources in the world, such as the Sahara, are in the particle shapes, lower density and darker colour. Icelandic dust particles greater than 20 μm retain volcanic morphological properties that are also found in fresh volcanic ash. Dust and fresh volcanic ash particles less than 20 μm are crystalline and blocky in nature, similar to the dust from other global source regions. The finer grained (<20 μm) Icelandic particles will have similar suspension and transport behaviours and be similarly hazardous to health and infrastructure as non‐Icelandic dust. The coarser particles (>20 μm) will have different suspension and transport behaviours than other dusts due to the volcanic morphology. Icelandic surface material has between 5% and 30% glassy particles compared to fresh volcanic ash which has more than 50% glassy particles. Glassy particles were observed to melt at a lower temperature than the mineral grains; and, as a result, volcanic ash is found to be more threatening to aircraft engines than the typical dust from Iceland. Icelandic dust was observed to be blocky, or plate‐like in the respirable size fraction, suggesting similar health hazards as dust from other regions.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The 2014–2015 Holuhraun eruption was the largest fissure eruption in Iceland in the last 200 years. This flood basalt eruption produced ~ 1.6 km
3
of lava, forming a lava flow field covering an area ...of ~ 84 km
2
. Over the 6-month course of the eruption, ~ 11 Mt of SO
2
were released from the eruptive vents as well as from the cooling lava flow field. This work examines the post-eruption SO
2
flux emitted by the Holuhraun lava flow field, providing the first study of the extent and relative importance of the outgassing of a lava flow field after emplacement. We use data from a scanning differential optical absorption spectroscopy (DOAS) instrument installed at the eruption site to monitor the flux of SO
2
. In this study, we propose a new method to estimate the SO
2
emissions from the lava flow field, based on the characteristic shape of the scanned column density distribution of a homogenous source close to the ground. Post-eruption outgassing of the lava flow field continued for at least 3 months after the end of the eruption, with SO
2
flux between < 1 and 9 kg/s. The lava flow field post-eruption emissions were not a significant contributor to the total SO
2
released during the eruption; however, the lava flow field was still an important polluter and caused high concentrations of SO
2
at ground level after lava effusion ceased.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
The 2010 eruption of Eyjafjallajökull produced volcanic ash that was mostly deposited to the south and east of the volcano, with the thickest deposits closest to the eruption vents. For ...months following the eruption there were numerous reports of resuspended volcanic ash made by weather observers on the ground. A saltation sensor (SENSIT) and an optical particle counter (OPC) located on the southern side of Eyjafjallajökull measured posteruptive particulate matter (PM) saltation and suspension events, some of which were also observable by satellite imagery. During the autumn/winter following the eruption, visible satellite images and the SENSIT show that PM measured by the OPC was only detected when winds had a northerly component, making the source on the slopes of Eyjafjallajökull. During the largest observed events, particles >10
μ
m were suspended but measured in extremely low concentrations (<1 particle per centimeter cubed). The saltation measurements, however, show high concentrations of particles >100
μ
m in size during these events. During the largest events, winds were at least 5 m s
−1
with a relative humidity < 70%. Ground conditions in Iceland change quickly from unfavorable to favorable for the suspension of particles. It is hypothesized that this is due to the porosity of the surface material allowing water to filter through quickly as well as the fast drying time of surface material. The high moisture content of the atmosphere and the ground do not appear to be a deterrent for large PM events to occur in Iceland.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Among the hazards posed by volcanoes are the emissions of gases and particles that can affect air quality and damage agriculture and infrastructure. A recent intense episode of volcanic degassing ...associated with severe impacts on air quality accompanied the 2018 lower East Rift Zone (LERZ) eruption of Kīlauea volcano, Hawai'i. This resulted in a major increase in gas emission rates with respect to usual emission values for this volcano, along with a shift in the source of the dominant plume to a populated area on the lower flank of the volcano. This led to reduced air quality in downwind communities. We analyse open-access data from the permanent air quality monitoring networks operated by the Hawai'i Department of Health (HDOH) and National Park Service (NPS), and report on measurements of atmospheric sulfur dioxide (SO 2) between 2007 and 2018 and PM 2.5 (aerosol particulate matter with diameter <2.5 µm) between 2010 and 2018. Additional air quality data were collected through a community-operated network of low-cost PM 2.5 sensors during the 2018 LERZ eruption. From 2007 to 2018 the two most significant escalations in Kīlauea's volcanic emissions were: the summit eruption that began in 2008 (Kīlauea emissions averaged 5-6 kt/day SO 2 from 2008 until summit activity decreased in May 2018) and the LERZ eruption in 2018 when SO 2 emission rates reached a monthly average of 200 kt/day during June. In this paper we focus on characterizing the airborne pollutants arising from the 2018 LERZ eruption and the spatial distribution and severity of volcanic air pollution events across the Island of Hawai'i. The LERZ eruption caused the most frequent and severe exceedances of the Environmental Protection Agency (EPA) PM 2.5 air quality threshold (35 µg/m 3 as a daily average) in Hawai'i in the period 2010-2018. In Kona, for example, the maximum 24-h-mean mass concentration of PM 2.5 was recorded as 59 µg/m 3 on the twenty-ninth of May 2018, which was one of eight recorded exceedances of the EPA air quality threshold during the 2018 LERZ eruption, where there had been no exceedances in the previous 8 years as measured by the Whitty et al. Kīlauea-PM 2.5 and SO 2 Concentrations HDOH and NPS networks. SO 2 air pollution during the LERZ eruption was most severe in communities in the south and west of the island, as measured by selected HDOH and NPS stations in this study, with a maximum 24-h-mean mass concentration of 728 µg/m 3 recorded in Ocean View (100 km west of the LERZ emission source) in May 2018. Data from the low-cost sensor network correlated well with data from the HDOH PM 2.5 instruments, confirming that these low-cost sensors provide a robust means to augment reference-grade instrument networks.
Large quantities of natural particulate matter are generated in Iceland every year. Glaciers, rivers, and explosive volcanic eruptions contribute to the production of suspended material in the air. ...With frequent high winds and sparse vegetation cover, fine and coarse particles are suspended and transported over land and out to sea. Observations of particulate matter during the period of 1966–2016 were used to determine the impact of explosive volcanic eruptions on the number of observed particulate matter events. These observations were made by weather observers at synoptic weather stations distributed around Iceland. Deposits from some explosive volcanic eruptions that produce new source material were found to increase the number of observations of particulate matter at stations relatively close to the volcano (within 125 km) for at least several months after the end of the eruption. This signal is only observed for eruptions that produced enough material to be classified into Volcano Explosive Index (VEI) of 3, or greater, and did not end during the winter, and is only rarely seen at the national scale. Eruptions starting shortly before or during the winter season and ending before the spring melt did not have an impact on the observations of suspended particulate matter due to snow covering the fresh material, reducing the potential for resuspension. The data set is insufficient to explain why only some eruptions fulfilling the criteria produce local effects persisting over multiple months. Seasonality, weather, and wind conditions are much stronger factors for increasing the number of particulate matter (PM) events than the creation of new material provided by explosive volcanic eruptions. A PM event is defined to occur when any type of PM is observed in the atmosphere.
•Number of PM observations after volcanic eruptions depends on timing and intensity.•Weather conditions determine the number of PM observations following an eruption.•Resuspended PM is mostly from known source areas rather than volcanic ash deposits.•Frequency of resuspended dust and/or ash follows a seasonal pattern.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
Volcanic systems are challenging environments in which to accurately sample or measure gaseous mercury (Hg) concentrations, as the gas plumes may be hot, acidic and halogen-rich; Hg concentrations ...may be highly variable; and the environment may not be readily accessible. We conducted an inter-method comparison study of atmospheric Hg measurements at Icelandic volcanic systems using four different methods. These included a passive air sampler (PAS), an active sampler with activated carbon trap (ACT) and two real-time measurement instruments, the Lumex portable mercury analyzer and the Tekran automated mercury analyzer. Good agreement in calculated and time-averaged volcanic plume Hg concentrations (ranging from 2.3 to 7.2 ng m−3) was obtained between the ACT and Lumex methods operated simultaneously at the same sites. In a post-fieldwork intercomparison, ACT and Tekran sampling yielded excellent agreement in measuring background atmospheric Hg concentrations. However, PAS-measured concentrations were significantly lower than the other methods, and in many cases were below the method detection limit, which may be due to the short sampling timeframes and/or adverse meteorological conditions not allowing sufficient Hg to be collected on the samplers. These findings demonstrate that Lumex and ACT methods are suitable for gaseous Hg measurement in volcanic gas plumes.
•We compared four gaseous mercury measurement methods at volcanic sites.•Activated carbon trap sampling agreed well with Lumex and Tekran results.•Passive samplers yielded significantly lower mercury than other methods.•Further tests are needed to assess passive samplers in sulfur-rich volcanic gases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed ...observations has obscured insight into the mechanical interplay between collapse and eruption. We use multiparameter geophysical and geochemical data to show that the 110-square-kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, near-exponential decline of both collapse rate and the intensity of the 180-day-long eruption.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
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