Showing papers by "Aude Leynaert published in 2023"
TL;DR: In this article , the authors examined sediments collected in the Coastal and Continental Margin Zones (CCMZs) of East China seas, an environment of peculiar interest given the large amount of lSi deposited by the Yellow River and the Yangtze River.
Abstract: Introduction The Coastal and Continental Margin Zones (CCMZs) contribute to 40% of the total burial flux of biogenic silica (bSi) of the world ocean. However, the accurate determination of the bSi content (bSiO2%) in marine sediments remains a challenge. The alkaline methods commonly used to quantitatively determine bSiO2% can completely digest the amorphous silica of diatoms but are less effective at digesting radiolarians and sponge spicules. In addition, the lithogenic silica (lSi) found in sediments is partly digested during these alkaline extractions, which can bias the accuracy of the determined bSiO2%. This is of importance in CCMZs where the lSi:bSi ratio is high. Methods In this study, we examined sediments collected in the CCMZs of East China seas, an environment of peculiar interest given the large amount of lSi deposited by the Yellow River and the Yangtze River. Results and discussion The results show that alkaline digestions using stronger solutions and pretreatment steps resulted in an overestimate of the bSiO2% due to increased leaching of silica mainly from authigenic silicates and clays, whereas weak digestions underestimated the bSiO2% owing to incomplete digestion of sponge spicules. We found that the use of the Si/Al method accurately corrects for the lSi fraction in marine sediments, and thereby improves the determinations of bSiO2% in the sediments of East China seas CCMZs. Ensuring full digestion of all bSi remainschallenging, in particular for sponge spicules, motivating both verifications via microscopy and longer extraction times. To emphasize the influence of these methodological differences, we revised the bSi burial flux in the East China seasand provide a new estimate of 253 (± 286) Gmol-SiO2 yr-1, which is one third of theprevious estimates. We discuss the potential contribution from radiolarian andsponges and we propose a new general protocol for the determination of bSi insediments that minimizes the methodological bias in bSi determination.
3 citations
TL;DR: In this paper , an overview of the different data quality control actions applied to fulfill requirements for quality and competence in environmental monitoring datasets is presented, along with equipment, accommodation, design of the ILC exercises, and statistical methodology specially adapted to small environmental networks and multivariate datasets.
Abstract: Introduction While crucial to ensuring the production of accurate and high-quality data—and to avoid erroneous conclusions—data quality control (QC) in environmental monitoring datasets is still poorly documented. Methods With a focus on annual inter-laboratory comparison (ILC) exercises performed in the context of the French coastal monitoring SOMLIT network, we share here a pragmatic approach to QC, which allows the calculation of systematic and random errors, measurement uncertainty, and individual performance. After an overview of the different QC actions applied to fulfill requirements for quality and competence, we report equipment, accommodation, design of the ILC exercises, and statistical methodology specially adapted to small environmental networks (<20 laboratories) and multivariate datasets. Finally, the expanded uncertainty of measurement for 20 environmental variables routinely measured by SOMLIT from discrete sampling—including Essential Ocean Variables—is provided. Results, Discussion, Conclusion The examination of the temporal variations (2001–2021) in the repeatability, reproducibility, and trueness of the SOMLIT network over time confirms the essential role of ILC exercises as a tool for the continuous improvement of data quality in environmental monitoring datasets.