Cycling and atmospheric exchanges of selenium in Canadian subarctic thermokarst ponds

• Published in: Biogeochemistry
• Main Authors: Lanceleur, Laurent, Tessier, Emmanuel, Bueno, Maïté, Pienitz, Reinhard, Bouchard, Frédéric, Cloquet, Christophe, Amouroux, David
• Other Authors: Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nordiques (CEN), Université Laval Québec (ULaval), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), We thank the TAKUVIK research program and the Arctic Metals project (ANR-11-CESA-0011) for logistic and financial support, We thank Claude Tremblay, Najat Bhiry and Warwick F. Vincent for their support at the field station of Centre for Northern Studies (CEN); Michel Cremer for particle-size distribution analyses; Laura Forsström for support in physico-chemical measures; posthumously, Jean Carignan, at the origin of the project Arctic Metals, ANR-11-CESA-0011,Arctic Metals,Devenir des éléments métalliques en régions arctique et sub-arctique: exposition des écosystèmes et des populations nordiques(2011)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Flux; Permafrost; Selenium; Subarctic; Thermokarst; Volatile; [CHIM.POLY]Chemical Sciences/Polymers; [CHIM.MATE]Chemical Sciences/Material chemistry; [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.ANAL]Chemical Sciences/Analytical chemistry; Canada; permafrost
• Online Access: https://hal-univ-pau.archives-ouvertes.fr/hal-02319607; https://doi.org/10.1007/s10533-019-00599-w

International audience The levels and speciation of dissolved, particulate and gaseous Se have been measured in five thermokarst ponds in a sporadic and discontinuous permafrost region of northern Québec (Canada) during summer oxygen stratification. Evolution of Se concentrations with depth was investigated in sediment cores collected in three different ponds. The potential for inorganic Se transformation in natural pond waters was investigated by experimental incubations of isotopic species-specific tracers of selenite and selenate. Experimental and monitoring observation revealed that high dissolved carbon concentration, suspended particle matter concentration, heterotrophic activity and periphytic biofilms have a significant role in the formation of gaseous selenium species. In sediment, Se is mainly associated with organic matter in the concentration range 0.14–1.6 mg kg−1. Despite low outgassing rates of volatile Se toward the atmosphere (1–97 ng Se m−2 day−1), the large surface occupied by ponds in northern Canada may lead to important exchange rates (ca. 1 ton year−1) at the global scale. Detailed measurements of Se speciation, including volatile compounds, and its reactivity toward heterotrophic activity in selected thaw ponds from the Canadian Subarctic provides new insight to better constrain the biogeochemical pathways leading to Se removal from the water column via atmospheric gas exchange and sediment accumulation.