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CO2 flux from Ribeira Quente river (Furnas Volcano -- São Miguel, Azores)

César Andrade1, J. Virgílio Cruz1, 2, Letícia Ferreira1, Fátima Viveiros1, 2, Diogo Braga1, António Cordeiro1

  • Affiliations:  1 IVAR -- Instituto de Investigação em Vulcanologia e Avaliação de Riscos, Universidade dos Açores, Ponta Delgada, Portugal. 2 Faculdade de Ciências e Tecnologia, Universidade dos Açores, Ponta Delgada, Portugal.

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 263

  • Programme No: 3.17.34

  • Theme 3 > Session 17

Abstract

Ribeira Quente river drains out Furnas Volcano, an active quaternary central volcano located in the island of São Miguel (Azores), being influenced by hydrothermal discharges. To characterize CO2 diffuse flux, measurements were made following the accumulation chamber method. Measurements were made systematically along the major river and the most important tributaries in the Ribeira Quente watershed along two surveys, totalizing 210 points and 215 points, respectively. Flux measurements are in the range between 0.4 and 24,085.5 g.m-2.d-1 (mean = 518.5 ± 1,901.8 g.m-2.d-1; median = 25.5 g.m-2.d-1), and between 2.2 and 10,637 g.m-2.d-1 (mean = 334 ± 884.9 g.m-2.d-1; median = 46.1 g.m-2.d-1), respectively along surveys 1 and 2. The background values of biogenic origin were estimated as 20 to 31 g.m-2.d-1. Flux along the several paths along which measurements were performed show sharp increases relative to background values whenever hydrothermal discharges to the river take place. Through the integration of the mean values, diffuse CO2 emission was calculated as 20. 5 t.d-1 and 23.8 t.d-1, respectively for surveys 1 and 2. This approach considers continuity along the overall area where measurements took place, and seems that overestimates the area, thus leading to a higher overall flux compared to the ones calculated by dividing the river channel in several sections and computing separately each contribution (15.5 t.d-1 and 13.0 t.d-1). The overall CO2 flux in the watershed is estimated as 17.8 t.d-1 and 14.6 t.d-1, considering the contribution of all tributaries where values are of biogenic source.