An evaluation of ambient sulphur dioxide concentrations from passive degassing of the Sulphur Springs, Saint Lucia geothermal system: Implications for human health

Passive diffusion tubes were used to measure the atmospheric SO2 concentrations at various sites in Sulphur Springs Park (SSP), in the town of Soufrière and in the capital of Castries. Measurements of average monthly ambient SO2 with the passive samplers indicated that during the dry season period of April to July 2014 concentration at sites closest to the main vents at SSP (Group 1), which are routinely used by staff and visitors, frequently exceeded the WHO 10-minute AQG for SO2 of 500 μg/m3. However, for sites that were more distal to the main venting area (Groups 2 and 3), the average monthly ambient SO2 did not exceed the WHO 10-minute AQG for SO2 of 500 μg/m3 during the entire monitoring period. The measured concentrations and dispersion patterns of ambient SO2 at SSP appear to be influenced by rainfall, proximity to the fumarolic vents, altitude (local topography), local atmospheric circulation and plume dispersion, and anthropogenic sources. Brochures and posters were prepared, for public distribution and display, on possible gas hazards that may be encountered at SSP and precautionary measures that may be taken by visitors to help minimise potential risk from elevated exposure to volcanic gases.