Stéphane Audry

Bio: Stéphane Audry is an academic researcher from University of Toulouse. The author has contributed to research in topics: Soil water & Drainage basin. The author has an hindex of 25, co-authored 58 publications receiving 2362 citations. Previous affiliations of Stéphane Audry include University of Bordeaux & Paul Sabatier University.

Biogeochemistry of organic carbon, CO2, CH4, and trace elements in thermokarst water bodies in discontinuous permafrost zones of Western Siberia

Abstract: Active processes of permafrost thaw in Western Siberia increase the number of soil subsidencies, thermokarst lakes and thaw ponds. In continuous permafrost zones, this process promotes soil carbon mobilisation to water reservoirs, as well as organic matter (OM) biodegradation, which produces a permanent flux of carbon dioxide (CO2) to the atmosphere. At the same time, the biogeochemical evolution of aquatic ecosystems situated in the transition zone between continuous permafrost and permafrost-free terrain remains poorly known. In order to better understand the biogeochemical processes that occur in thaw ponds and lakes located in discontinuous permafrost zones, we studied ~30 small (1–100,000 m2) shallow (<1 m depth) lakes and ponds formed as a result of permafrost subsidence and thaw of the palsa bog located in the transition zone between the tundra and forest-tundra (central part of Western Siberia). There is a significant increase in dissolved CO2 and methane (CH4) concentration with decreasing water body surface area, with the largest supersaturation with respect to atmospheric CO2 and CH4 in small (<100 m2) permafrost depressions filled with thaw water. Dissolved organic carbon (DOC), conductivity, and metal concentrations also progressively increase from large lakes to thaw ponds and depressions. As such, small water bodies with surface areas of 1–100 m2 that are not accounted for in the existing lake and pond databases may significantly contribute to CO2 and CH4 fluxes to the atmosphere, as well as to the stocks of dissolved trace elements and organic carbon. In situ lake water incubation experiments yielded negligible primary productivity but significant oxygen consumption linked to the mineralisation rate of dissolved OM by heterotrophic bacterioplankton, which produce a net CO2 flux to the atmosphere of 5 ± 2.5 mol C m2 year−1. The most significant result of this study, which has long-term consequences on our prediction of aquatic ecosystem development in the course of permafrost degradation is CO2, CH4, and DOC concentrations increase with decreasing lake age and size. As a consequence, upon future permafrost thaw, the increase in the number of small water bodies, accompanied by the drainage of large thermokarst lakes to the hydrological network, will likely favour (i) the increase of DOC and colloidal metal stocks in surface aquatic systems, and (ii) the enhancement of CO2 and CH4 fluxes from the water surface to the atmosphere. According to a conservative estimation that considers that the total area occupied by water bodies in Western Siberia will not change, this increase in stocks and fluxes could be as high as a factor of ten.

An international symposium

Abstract: s should clearly state the purpose, brief statement of procedure, results and conclusions. Please include your name, full address and topic on all submissions. At least one author of each abstract should register for the conference. All accepted abstracts will be published as symposium proceedings. Additionally, commended abstracts may be published in a journal after they are expanded to a manuscript followed by extensive reviewing. The language of the conference will be English.

Is there a future for sequential chemical extraction

Abstract: Since their introduction in the late 1970s, sequential extraction procedures have experienced a rapid increase in use. They are now applied for a large number of potentially toxic elements in a wide range of sample types. This review uses evidence from the literature to consider the usefulness and limitations of sequential extraction and thereby to assess its future role in environmental chemical analysis. It is not the intention to provide a comprehensive survey of all applications of sequential extractions or to consider the merits and disadvantages of individual schemes. These aspects have been covered adequately in other, recent reviews. This review focuses in particular on various key issues surrounding sequential extractions such as nomenclature, methodologies, presentation of data and interpretation of data, and discusses typical applications from the recent literature for which sequential extraction can provide useful and meaningful information. Also covered are emerging developments such as accelerated procedures using ultrasound- or microwave energy-assisted extractions, dynamic extractions, the use of chemometrics, the combination of sequential extraction with isotope analysis, and the extension of the approach to non-traditional analytes such as arsenic, mercury, selenium and radionuclides.

Global CO2 emissions from dry inland waters share common drivers across ecosystems

Abstract: Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO2) emissions from these sedim ...