Seasonal and diurnal patterns in the dispersion of SO2 from Mt. Nyiragongo. (May 2016)

• Record Type: Journal Article
• Authors: Dingwell, Adam; Rutgersson, Anna; Claremar, Björn; Arellano, Santiago; Yalire, Mathieu M.; Galle, Bo
• Is Part Of: Atmospheric environment. Volume 132(2016)
• Page Start: 19
• Page End: 29
• Publication Date: 2016-05
• Subjects: Dispersion modelling -- Volcanic degassing -- Nyiragongo -- Sulfur dioxide -- FLEXPART-WRF; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2016.02.030
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Mt. Nyiragongo is an active volcano located in the Democratic Republic of Congo, close to the border of Rwanda and about 15 km north of the city of Goma (∼ 1, 000, 000 inhabitants). Gases emitted from Nyiragongo might pose a persistent hazard to local inhabitants and the environment. While both ground- and satellite-based observations of the emissions exist, prior to this study, no detailed analysis of the dispersion of the emissions have been made. We have conducted a dispersion study, using a modelling system to determine the geographical distribution of SO2 . A combination of a meteorological model (WRF), a Lagrangian particle dispersion model (FLEXPART-WRF) and flux data based on DOAS measurements from the NOVAC-network is used. Since observations can only be made during the day, we use random sampling of fluxes and ensemble modelling to estimate night-time emissions. Seasonal variations in the dispersion follows the migration of the Inter Tropical Convergence Zone. In June–August, the area with the highest surface concentrations is located to the northwest, and in December–February, to the southwest of the source. Diurnal variations in surface concentrations were determined by the development of the planetary boundary layer and the lake-/land breeze cycle around lake Kivu. Both processes contribute to low surface concentrations during the day and high concentrations during the night. However, the strong northerly trade winds in November–March weakened the lake breeze, contributing to higher daytime surface concentrations along the northern shore of Lake Kivu, including the city of Goma. For further analysis and measurements, it is important to include both seasonal and diurnal cycles in order to safely cover periods of high and potentially hazardous concentrations. Highlights: A strong variability in the dispersion of gases from Mt. Nyiragongo was found. The regional dispersion depends on seasonal weather patterns. There is also a local influence from land-sea breezes around lake Kivu. Local communities might be more exposed to emissions than previously assumed.