Intertwining the elemental cycles of iron and carbon: Iron’s influence on the fate and dynamics of organic carbon in the environment

From respiration and DNA synthesis to superparamagnetic nanoparticles, magnetotactic bacteria and old rusty cars, iron is everywhere. Our understanding of iron geochemistry is central to the study of carbon and vice versa as it is nearly impossible to find an environment where these two elements are not conjoined. Iron has a profound effect on the carbon that cycles on geological time scales—in sedimentary rocks, in coal and petroleum deposits, the balance between carbon preservation and remineralization is in part modulated by iron. Approximately 20% of the organic carbon buried in sediments is protected by reducible iron phases, well below the oxic-anoxic limit of the sediment where they are no longer thermodynamically stable. Iron represents a globally important sink for sedimentary organic matter (OM), contributing to maintaining the delicate balance of O2 and CO2 in the atmosphere. Iron also impacts the carbon cycling in active oceanic, atmospheric and lithospheric reservoirs, for example by linking continental erosion to carbon deposition in sediments, and iron-rich riverine discharge and dust deposition to phytoplankton blooms in the middle of the ocean. The association of iron and OM also influences the photoreactivity (Zepp, 2003) and bioavailability (Mackay and Zirino, 1994; Raiswell and Canfield, 2012a), of both elements in aquatic systems. In spite of its significance to high-turnover and refractory carbon, the exact mechanism of interaction between iron and OM is not yet known. We postulate the formation of inner-sphere complexes or coagulates at oxic-anoxic interfaces. We observe preferential sheltering of organic molecules with low C:N atomic ratios and enriched isotopic signatures (δ13C). A novel method, coupling a total organic carbon (TOC) analyzer to an isotope ratio mass spectrometer, was developed to determine the δ13C of the dissolved organic matter that is retained by iron and other minerals. We find that iron phases increase the affinity and adhesion of 13C-enriched dissolved molecules to particulate phases – which has been reported to slow bacterial degradation. Further elucidation of the mechanism of interaction between the 2 elements could be achieved through novel instrumental methods, including TEM microscopy and EXAFS spectroscopy which are used to determine the macrostructural arrangement of iron and OM and the chemical environment surrounding iron atoms in sediments

Assessing carbon dynamics in natural and perturbed boreal aquatic systems

Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to 25 natural systems, human perturbations such as watershed wood harvesting and long term reservoir 26 impoundment lead to profound alterations of biogeochemical processes involved in the aquatic 27 cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in 28 five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon 29 dioxide (CO2), methane (CH4), oxygen (O2), and organic carbon (DOC), as well as total nitrogen 30 (TN) and phosphorus (TP). Dissolved and particulate organic matter, forest soil/litter and 31 leachates, as well as dissolved inorganic carbon (DIC) were analyzed for elemental and stable 32 isotopic compositions (atomic C:N ratios, δ13Corg, δ13Cinorg and δ15Ntot). We found links between 33 the export of terrestrial OM to these systems and the dissolved CO2 and O2 concentrations in the 34 water column, as well as CO2 fluxes to the atmosphere. All systems were GHG emitters, with 35 greater emissions measured for systems with larger inputs of terrestrial OM. The differences in 36 CO2 concentrations and fluxes appear controlled by bacterial activity in the water column and the 37 sediment. Although we clearly observed differences in the aquatic C cycle between natural and 38 perturbed systems, more work on a larger number of water bodies, and encompassing all four 39 seasons should be undertaken to better understand the controls, rates, as well as spatial and 40 temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of 41 GHG emissions (and other key variables) from natural and perturbed systems

Preservation of organic matter in sediments promoted by iron

The biogeochemical cycles of iron and organic carbon are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved iron. In soils, solid iron phases shelter and preserve organic carbon, but the role of iron in the preservation of organic matter in sediments has not been clearly established. Here we use an iron reduction method previously applied to soils to determine the amount of organic carbon associated with reactive iron phases in sediments of various mineralogies collected from a wide range of depositional environments. Our findings suggest that 21.5 ± 8.6 per cent of the organic carbon in sediments is directly bound to reactive iron phases. We further estimate that a global mass of (19–45) × 1015 grams of organic carbon is preserved in surface marine sediments as a result of its association with iron. We propose that these associations between organic carbon and iron, which are formed primarily through co-precipitation and/or direct chelation, promote the preservation of organic carbon in sediments. Because reactive iron phases are metastable over geological timescales, we suggest that they serve as an efficient ‘rusty sink’ for organic carbon, acting as a key factor in the long-term storage of organic carbon and thus contributing to the global cycles of carbon, oxygen and sulphur

Home and Online Management and Evaluation of Blood Pressure (HOME BP) using a digital intervention in poorly controlled hypertension: randomised controlled trial

Objective: The HOME BP (Home and Online Management and Evaluation of Blood Pressure) trial aimed to test a digital intervention for hypertension management in primary care by combining self-monitoring of blood pressure with guided self-management. Design: Unmasked randomised controlled trial with automated ascertainment of primary endpoint. Setting: 76 general practices in the United Kingdom. Participants: 622 people with treated but poorly controlled hypertension (>140/90 mm Hg) and access to the internet. Interventions: Participants were randomised by using a minimisation algorithm to self-monitoring of blood pressure with a digital intervention (305 participants) or usual care (routine hypertension care, with appointments and drug changes made at the discretion of the general practitioner; 317 participants). The digital intervention provided feedback of blood pressure results to patients and professionals with optional lifestyle advice and motivational support. Target blood pressure for hypertension, diabetes, and people aged 80 or older followed UK national guidelines. Main outcome measures: The primary outcome was the difference in systolic blood pressure (mean of second and third readings) after one year, adjusted for baseline blood pressure, blood pressure target, age, and practice, with multiple imputation for missing values. Results: After one year, data were available from 552 participants (88.6%) with imputation for the remaining 70 participants (11.4%). Mean blood pressure dropped from 151.7/86.4 to 138.4/80.2 mm Hg in the intervention group and from 151.6/85.3 to 141.8/79.8 mm Hg in the usual care group, giving a mean difference in systolic blood pressure of −3.4 mm Hg (95% confidence interval −6.1 to −0.8 mm Hg) and a mean difference in diastolic blood pressure of −0.5 mm Hg (−1.9 to 0.9 mm Hg). Results were comparable in the complete case analysis and adverse effects were similar between groups. Within trial costs showed an incremental cost effectiveness ratio of £11 ($15, €12; 95% confidence interval £6 to £29) per mm Hg reduction. Conclusions: The HOME BP digital intervention for the management of hypertension by using self-monitored blood pressure led to better control of systolic blood pressure after one year than usual care, with low incremental costs. Implementation in primary care will require integration into clinical workflows and consideration of people who are digitally excluded. Trial registration: ISRCTN13790648

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

PrendreParole : récit d’une pratique de l’enseignement de la création de balados en contexte du cours de français au secondaire

Lorsqu’il est question d’enseignement et d’évaluation de la communication orale, l’exposé individuel est l’activité la plus fréquemment employée dans les écoles québécoises. Or, de nombreuses options gagneraient à être explorées afin d’à la fois diversifier, mais aussi d’enrichir les pratiques. C’est en fonction de cette prémisse que s’articule PrendreParole un projet ludique de création de balados à saveur mythologique. En plus d’aborder l’enseignement du français oral, ce dispositif vise à développer de façon concomitante les compétences numériques et multimodales. Cet article décrit le projet sous la forme d’un récit de pratique structuré par la méthode des 4P, puis relève des trajectoires d’intérêt quant à la mobilisation de ces compétences par le mode sonore dans le contexte du cours de français au secondaire.When it comes to teaching and evaluating oral communication, individual presentations are the most prevalent method employed in Quebec schools. However, many alternatives would benefit from being explored to both diversify and enrich practices. It is from this premise that stems PrendreParole, a gamified pedagogical project of podcast creation with mythological undertones. In addition to French oral skills, this project aims to concurrently develop digital and multimodal competencies. This article describes the project through a narrative of practice structured by the 4P method, then identifies trajectories of interest regarding the mobilization of such competencies through the use of sound modalities in the context of French class at highschool level