Shining Light on Black Rock Coatings in Smelter-Impacted Areas

Earth scientists have long known of the existence of black coatings on exposed rocks in smelter-impacted areas such as Sudbury, Ontario or Rouyn-Noranda, Québec. Black rock coatings in the Greater Sudbury area are remarkable geological records of atmospheric conditions, including mixing, scavenging, and oxidation processes, deposition rates, and the nature and source of anthropogenic releases to the atmosphere. The coatings are composed of an amorphous silica matrix that has trapped atmosphere-borne nanoparticles and has preserved their chemical and isotopic signature. These coatings are the product of high emissions of SO2 and subsequent non-stoichiometric dissolution of exposed siliceous rocks. The coatings contain spherical smelter-derived Cu–Ni-oxide particulate matter (micrometre and nanometre-sized) and metal-sulphate rich layers composed of nanometer aggregates of Fe–Cu sulphates. Lead, As, and Se-bearing nanoparticles emitted from smelters are incorporated in metal-sulphate-rich layers along the atmosphere-coating interface, presumably during coating formation. On a regional scale, ratios between different metal(loid)s in the coatings indicate that small diameter primary Pb, As and Se-bearing sulphate aerosols have been deposited at higher rates compared to larger, Ni-bearing particulate matter. High sulphur isotope values in coatings closer to smelting centres and their decrease with distance from the smelters is attributed to an increase in mixing of primary and secondary sulphates. SOMMAIRELes géoscientifiques connaissent depuis longtemps l’existence d’une couche noire sur les roches exposées aux abords des fonderies comme celles de Sudbury en Ontario ou Rouyn-Noranda au Québec.   Les couches noires des roches de la grande région de Sudbury constituent de remarquables enregistrements géologiques des phénomènes atmosphériques, notamment des processus de mélange, de piégeage, et d'oxydation, ainsi que des taux de sédimentation et de la nature et de l’origine des rejets anthropiques dans l'atmosphère.   Ces couches noires sont constituées d'une matrice de silice amorphe qui a piégé des nanoparticules atmosphériques et conservé leur signature chimique et isotopique.  Ces couches noires sont le produit de fortes émissions atmosphériques de SO2 et d’une dissolution non-stœchiométrique subséquente des roches siliceuses exposées.  Ces couches noires contiennent des sphérules de particules atmosphériques d’oxydes de Cu-Ni (de taille micrométrique et nanométrique) issues de la fonderie, et des couches riches en sulfate de métaux constituées d’agrégats nanométriques de sulfates de Fe-Cu.   Les nanoparticules de plomb, d’As et de Se émises par les fonderies sont incorporées dans les couches riches en sulfate de métal à l'interface de l’atmosphère et de cette couche, probablement lors de la formation de cette couche.  À l’échelle régionale, les rapports de concentration des différents métaux ou métalloïdes dans les couches noires indiquent que les aérosols de faible diamètre de sulfate de Pb, d’As et de Se primaires ont été déposés à des taux plus élevés que les particules nickélifères de plus grande dimension.  Les valeurs plus élevées des isotopes du soufre observées dans les couches à proximité des fonderies et leur diminution en fonction de l’éloignement des fonderies sont attribuées à une augmentation du mélange entre sulfates à l’émission et post-émission

Early changes in tissue amino acid metabolism and nutrient routing in rats fed a high-fat diet: evidence from natural isotope abundances of nitrogen and carbon in tissue proteins

International audienceLittle is known about how diet-induced obesity and insulin resistance affect protein and amino acid (AA) metabolism in tissues. The natural relative abundances of the heavy stable isotopes of C (δ 13C) and N (δ 15N) in tissue proteins offer novel and promising biomarkers of AA metabolism. They, respectively, reflect the use of dietary macronutrients for tissue AA synthesis and the relative metabolic use of tissue AA for oxidation v. protein synthesis. In this study, δ 13C and δ 15N were measured in the proteins of various tissues in young adult rats exposed perinatally and/or fed after weaning with a normal- or a high-fat (HF) diet, the aim being to characterise HF-induced tissue-specific changes in AA metabolism. HF feeding was shown to increase the routing of dietary fat to all tissue proteins via non-indispensable AA synthesis, but did not affect AA allocation between catabolic and anabolic processes in most tissues. However, the proportion of AA directed towards oxidation rather than protein synthesis was increased in the small intestine and decreased in the tibialis anterior muscle and adipose tissue. In adipose tissue, the AA reallocation was observed in the case of perinatal or post-weaning exposure to HF, whereas in the small intestine and tibialis anterior muscle the AA reallocation was only observed after HF exposure that covered both the perinatal and post-weaning periods. In conclusion, HF exposure induced an early reorganisation of AA metabolism involving tissue-specific effects, and in particular a decrease in the relative allocation of AA to oxidation in several peripheral tissues

Natural abundance of nitrogen isotopes in amino acids are biomarkers of the metabolic syndrome onset

International audienceIntroduction: The isotope effects associated with nitrogen metabolic pathways result in differences in the nitrogen stable isotopecompositions (δ15N) of metabolic pools within individuals. Thus, inter-individual differences in some δ15N values can reflect differencesin nitrogen metabolismObjectives: Here, we evaluated in rats whether the metabolic syndrome (MS) onset involve some dysregulations of nitrogen metabolismwhich can be traced with δ15N values of individual amino acids in plasma and tissue proteins.Method / Design: Sixty male Wistar rats were fed a high fat diet for 10 weeks and 2 groups were selected in either the upper (MS group,n=10) or the lower (Lean, control group, L, n=10) ends of body weight and fasting insulin distributions and killed for tissue collection. Plasma and tissue proteins were precipitated and hydrolyzed and δ15N values of Ala, Asx, Glx, Gly, Leu, Pro and Ser were determined usinggas chromatograph combustion isotope ratio mass spectrometry.Results: Body weight and fasting insulin were 1.3 and 8.2 fold higher in the MS compared with the L group, respectively. No differencewas observed between groups for δ15N values of Asx, Glx, Leu, Pro and Ser, whereas δ15N values of Ala and Gly were significantly lowerin plasma and muscle proteins of the MS group. A discriminant analysis showed that the difference between δ15N of Gly and Leu in plasmaproteins is the main contributor to group separation. On the basis of this variable alone, 95% of the rats were correctly classified as MS or L.Conclusions: These results evidence that nitrogen metabolism is affected during the onset of insulin resistance in a tissue-specificmanner. They also suggest that the δ15N of some plasma amino acids represent promising early biomarkers of these metabolic changes.Keywords: (maximum 5): compound-specific amino acid δ15N values, early biomarkers, metabolic syndrome, protein and amino acidmetabolis