Evgenia Ilyinskaya

The 2021 Fagradalsfjall eruption marked the first in a series of ongoing eruptions in a densely populated region of Iceland (>260 000 residents within 50 km distance). This eruption was monitored by an exceptionally dense regulatory air quality network, providing a unique opportunity to examine fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its relatively small size, the eruption led to statistically-significant increases in PM and SO₂ concentrations at distances of at least 300 km. Peak daily-mean concentrations of PM₁ (measured in the capital area, 25–35 km distance from the source) rose from 5–6 to 18–20 µg m⁻³, and the proportion of PM₁ within PM₁₀ increased by ∼50 %. In areas with low background pollution, average PM₁₀ and PM_2.5 levels increased by ∼50 % but in places with high background sources, the eruption's impact was not detectable. These findings suggest that ash-poor eruptions are a major source of PM₁ in Iceland and potentially in other regions exposed to volcanic emissions. Air quality guidelines for PM₁ and SO₂ were exceeded more frequently during the eruption than under background conditions. This suggests the potential for an increase in adverse health effects. Moreover, pollutant concentrations exhibited strong fine-scale temporal (≤1 h) and spatial (<1 km) variability. This suggests disparities in population exposures to volcanic air pollution, even from relatively distal sources, and underscores the importance of a dense monitoring network and effective public communication.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

Effusive basaltic eruptions are an important source of volatile trace elements to the troposphere. Constraining the effects of background atmospheric conditions on the transport behavior and plume lifetimes of these elements is critical, both in the use of trace elements as proxies in the geological record, and in mitigating exposure to these elements in downwind communities. Through in-situ multi-element sampling of the Fagradalsfjall (Iceland) 2021-2022 eruption plumes we present the first direct comparison of element dispersion behavior under wet and dry atmospheric conditions. We demonstrate that the alkali metals (Na, K, Rb, Cs) are depleted up to an order of magnitude more under wet background conditions compared to elements such as Se, As, and Cd, which are instead lost preferentially in drier conditions. We propose that heterogeneous element deposition from the volcanic plume is driven by the interactions between element gas-phase speciation, water solubility of the resulting complexes, particulate size-distribution, and affinity for scavenging by larger ash particles. For volcanoes situated in regions with distinct seasonal weather patterns, the delivery of elements to the surface, and thus human exposure to potentially toxic metals such as arsenic, lead, cadmium, and selenium, could therefore vary between wet and dry conditions.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.

The 2021 Fagradalsfjall fissure eruption was the first of ongoing eruptions in the most densely populated part of Iceland (70 % of population within 50 km). It was monitored by an exceptionally dense reference-grade air quality network (14 stations within 40 km), and the first time that a reference-grade timeseries of PM₁ was collected during an eruption. We used these measurements to identify fine-scale dispersion patterns of volcanic air pollutants (SO₂, PM₁, PM_2.5, PM₁₀) in populated areas. Despite its small size the eruption caused a statistically-significant increase in average and peak PM and SO₂ concentrations in at least 300 km distance. Peak daily-means of PM₁ peak rose to 18–20 µg/m³ from 5–6 µg/m³; and proportion of PM₁ increased relative to coarser PM fractions (21–24 % of PM₁₀ compared to 14 % background). Eruption increased PM₁₀ and PM_2.5 by ~50 % in populated areas with low background concentrations, but its impact was not measurable in areas with high background sources. This suggests that ash-poor eruptions are one of, or the most, important source of PM₁ in Iceland, and potentially in other areas exposed to volcanic emissions. There were significant fine-scale temporal (≤1 hour) and spatial (3 SO₂, and 5 and 0 exceedance events, respectively, within a ~12-hour plume advection event. This has implications for population exposures estimates.