Two Typical Case Studies of Volcanic Eruption Trace Gases Based on EMI Observations

Volcano eruption is one of the most destructive natural disasters, and its direct release of toxic gases and volcanic ash can lead to atmospheric pollution, posing significant threats to human health and ecological balance. To investigate the environmental impact of volcanic emissions, we retrieved the vertical column densities (VCDs) of sulfur dioxide (SO₂) and bromine monoxide (BrO) using the Chinese highest-resolution atmospheric trace gas remote sensing satellite payloads: the Environmental Trace Gas Monitoring Instrument (EMI) series on-board the GaoFen (GF5-02) and DaQi (DQ-1) satellites.

Here, we present our study on two significant volcanic emission events. On January 15, 2022, a violent eruption occurred near the South Pacific Island nation of Tonga, which is a typical submarine volcano. During this eruption, the volcanic plume ascended directly into the stratosphere (above 20 km), releasing a substantial amount of SO₂ and spreading rapidly westward (~30 m/s). In contrast, the majority of the BrO dispersed southeastward slowly (~10 m/s) within the altitude range of 8–15 km on January 16. The differences in eruption height and timing resulted in the transport of SO₂ and BrO in distinct directions in the Southern Hemisphere.

Another case is the Sundhnukagigar volcano on Iceland's Reykjanes Peninsula, which is a typical fissure volcano. A significant eruption began at 21:00 on August 22nd, following an earthquake swarm; this was the largest eruption in the region since December 2023. Satellite data indicated that the volcanic eruption released high concentrations of SO₂, with the maximum SO₂ VCD exceeding 15 Dobson Units (DU). By the morning of the 26th, part of the air mass had been transported northward to the Arctic Svalbard region. Simultaneously, ground observations from Ny-Ålesund revealed that an unprecedented Arctic haze event occurred, with the SO₂ VCD reaching approximately 40 times the usual level. It is also important to note that, in the context of global warming, the ongoing activity of Iceland's volcanoes will further exacerbate the melting of local glaciers and permafrost. This, in turn, disrupts the gravitational balance of the overlying crust, leading to an intensification of volcanic activity. Therefore, it is essential to employ multi-instrument, multi-scale, and high-resolution observations to monitor volcanic activity and assess its impact on both regional and global climate and the environment.