Atmospheric particulate mercury in the megacity Beijing: Spatio-temporal variations and source apportionment
Particulate mercury (HgP) concentrations in weekly aerosol samples (PM2.5 and TSP) from Beijing, China, were measured for a complete year. In addition, spatial differences were measured for a shorter time period at four different sites and potential source materials were analyzed. Average HgP concentrations in PM2.5 samples were 0.26 ng/m3 for day-time PM2.5, 0.28 ng/m3 for night-time PM2.5, and 0.57 ng/m3 for TSP samples, respectively. Coal combustion was identified as the major source of HgP in Beijing. Other sources included industrial activities as well as red color on historical buildings as a minor contribution. Spatial differences were pronounced with highest concentrations in the inner city (inside the 3rd ring road). The results further showed a strong seasonality with highest concentrations in winter and lowest in summer due to local meteorological conditions (precipitation in summer and stagnant conditions and low mixing layer height in winter) as well as seasonal sources, such as coal combustion for heating purposes. Day–night differences also showed a seasonal pattern with higher night-time concentrations during summer and higher day-time concentrations during winter. Compared to other cities worldwide, the HgP concentrations in Beijing were alarmingly high, suggesting that airborne particulate Hg should be the focus of future monitoring activities and mitigation measures.
(Atmospheric Environment. vol. 109, n° 1352-2310, pp. 251-261, 01/05/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
When deep diagenesis in Arctic Ocean sediments compromises manganese-based geochronology
We used a diagenetic model to test the hypothesis that manganese-rich layers in gas hydrate-bearing Arctic Ocean sediments are reliable time markers for interglacial periods. In the model, diagenesis is fuelled by two sources of reactive carbon: particulate organic carbon settling to the sediment surface, and methane diffusing up from deep gas hydrate deposits. The model includes oxidation of organic carbon and soluble reduced manganese by oxygen supplied continuously from an invariant bottom-water oxygen reservoir; reduction of particulate manganese by hydrogen sulfide generated through anaerobic methane oxidation; transport of dissolved oxygen and manganese by diffusion; and advective transport of particulate components by burial. Particulate organic matter and particulate manganese are only supplied to the sediment during interglacials. Sulfate reduction is not modeled explicitly; instead, the effect of anaerobic methane oxidation on Mn reduction is simulated at the lower boundary of the model by prescribing that particulate manganese is reduced there to soluble Mn(II). The soluble reduced Mn then diffuses upward and is oxidatively precipitated to Mn(IV) by downward diffusing oxygen. The upward flux of soluble Mn(II) is thus a function of the rate at which particulate manganese is advected into the Mn-reduction layer at the bottom of the model; it is not synchronous with events at the sediment–water interface. Model runs reveal that, under idealized but realistic conditions for the Arctic Ocean, oxidation of upward-diffusing Mn(II) generates post-depositional manganese enrichments that cannot readily be distinguished from the manganese-rich sediment layers that accumulate during interglacials. This compromises the use of manganese-rich layers as proxies for interglacial periods. In contrast, manganese-rich layers may be used as first-order markers of interglacial periods in sediments where gas hydrates or other forms of reactive carbon are absent.
(Marine Geology. vol. 366, n° 0025-3227, pp. 62-68, 27/04/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Oceanography: Fresh news from the Atlantic
The Atlantic overturning circulation plays a key role in large-scale climate but how it varies is not well known. Now a study proposes that the weakening it may have experienced in the late 1970s is unprecedented over the last millennium.
(Nature Climate Change. vol. 5, n° 1758-678X, pp. 411-412, 23/04/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Photochemical Aging of Secondary Organic Aerosols Generated from the Photooxidation of Polycyclic Aromatic Hydrocarbons in the Gas-Phase
Aging processes of secondary organic aerosol (SOA) may be a source of oxygenated organic aerosols; however the chemical processes involved remain unclear. In this study we investigate photochemical aging of SOA produced by the gas-phase oxidation of naphthalene by hydroxyl radicals and acenaphthylene by ozone. We monitored the SOA composition using a high-resolution time-of-flight aerosol mass spectrometer (HR-AMS). We initiated SOA aging with UV photolysis alone and with OH radicals in the presence or absence of light and at different NOx levels. For naphthalene, the organic composition of the particulate phase seems to be dominated by highly oxidized compounds such as carboxylic acids, and aging data may be consistent with diffusion limitations. For acenaphthylene, the fate of oxidized products and the moderately oxidized aerosol seem to indicate that functionalization reactions might be the main aging process were initiated by the cumulative effect of light and OH radicals.
(Environmental Science and Technology. vol. 49, n° 0013-936X, pp. 5407-5416, 22/04/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mercurial exposure of residents of Santarém and Oriximiná cities (Pará, Brazil) through fish consumption
A survey of the mercurial exposure of residents of Santarém and Oriximiná showed a differential mercurial impregnation between men and women. At the level of both cities, the mean hair mercury concentrations were 1.5 ± 0.5 (90th and 95th percentiles: 2.8 and 4.3) and 2.52 ± 0.09 μg g Hg/g (90th and 95th percentiles: 4.7 and 8.1) for women and men, respectively. The mercurial contamination appeared significantly closely linked to the daily amount of consumed fish. Carnivore species pescada branca (Plagioscion squamosissimus) and apapá (Pellona castelnaeana) and non-carnivore species pacú (Mylossoma duriventre) and aracú (Schizodon fasciatus) were consumed by 22, 19, 55 and 25 % of people, respectively, and the mean mercury concentrations within fish flesh were 1.44 ± 0.11, 1.66 ± 0.19, 0.48 ± 0.09 and 0.49 ± 0.06 μg/g dry weight, respectively. Men aged above 35 were significantly more contaminated than those below. The mean hair concentrations of men were 5.20 ± 1.25 and 1.50 ± 0.22 μg/g, for those aged above 35 and below, respectively. The probability for women of childbearing age from both cities to present a hair mercury concentration above 1 μg Hg/g (corresponding to the US Environmental Protection Agency reference dose) was equal to 0.30 (95 % confidence interval of 0.24-0.36). The probability of hair mercury concentration to be above the lowest observable adverse effect level (LOAEL) (0.3 μg Hg/g) was equal to 0.79 (95 % confidence interval: 0.73-0.86).
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 12150-12161, 18/04/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Développement et applications de l'analyse dirigée par l'effet pour la recherche et l'identification de contaminants à risque pour les écosystèmes aquatiques
Les méthodes actuellement disponibles pour la surveillance de la qualité du milieu se réfèrent au suivi de composés définis par les réglementations et ne permettent pas d’appréhender l’(éco)toxicité réelle de tous les composés présents dans l’environnement (e.g. composés inconnus, produits de transformation, effets de mélange…). Dans ce contexte, une méthode d’analyse pluridisciplinaire intégrative, l’analyse dirigée par l’effet (EDA), a été développée. Cette approche bio-analytique vise à établir un lien de causalité entre une exposition aux contaminants et l’effet biologique observé. La démarche est basée sur la simplification séquentielle d’un échantillon guidée par les bio-essais afin d’individualiser puis identifier, par des techniques analytiques chimiques performantes, les composés biologiquement actifs. Les objectifs de cette thèse ont porté sur (1) le développement et la validation d’une méthodologie, allant du pré-traitement jusqu’au fractionnement, adaptée à différentes matrices environnementales ; (2) la mise en place d’une stratégie d’identification moléculaire par spectrométrie de masse haute résolution ; (3) l’application de la démarche EDA à plusieurs échantillons afin d’illustrer l’adaptabilité et l’apport d’une telle méthode à des problématiques environnementales. Ces travaux de thèse permettent de disposer aujourd’hui d’une démarche bio-analytique complète de la préparation d’échantillon à l’identification de molécules, et adaptée à tous types d’échantillons. Les différentes études environnementales réalisées au cours de ces travaux ont permis, entre autre, d’établir une liste de composés diverses non recherchés pouvant représenter un risque pour l’environnement.
(10/04/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey
The North Anatolian fault (NAF) in the Marmara Sea is a significant hazard for the city of Istanbul. The use of paleoseismological data to provide an accurate seismic risk assessment for the area is constrained by the fact that the NAF system is submarine; thus a history of paleoearthquakes can be inferred only by using marine sediment cores. Here, a record of turbidites was obtained in two cores and used to reconstruct the earthquake history along the Çınarcık segment, a main branch of the NAF. Klg04 was collected from a berm north of the fault, and Klg03 was positioned in the Çınarcık basin, south of the fault. The cores were correlated using long-term geo-chemical variations in the sediment, and turbidites deposited simultaneously at both sites were then identified. Radionuclide measurements suggest the most recent turbi-dite was triggered by the 1894 C.E. M w 7.3 earthquake. We conclude that the turbidites identified at both sites are earthquake generated, based on their particular sedimento-logical and geochemical signatures; the correlation of turbidites at berm and basin sites; and the match of the most recent turbidite with a nineteenth century historical earthquake. To date older turbidites, we used carbon-14 and paleomagnetic data to build an OxCal model with a local reservoir correction of 400 50 yr. The Çınarcık segment is found to have ruptured in 1509 C.E., sometime in the fourteenth century, in 989 C.E., and in 740 C.E., with a mean recurrence interval in the range of 256–321 years. Finally, we used the earthquake record obtained to review the rupture history of the adjacent segments over the past 1500 years.
(Bulletin of the Seismological Society of America. vol. 105, n° 0037-1106, pp. 622-645, 01/04/2015)
LGENS, INSU - CNRS, CNRS, ENS-PSL, PSL, LDEO, ULiège, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS, AGEs, ULiège
Performance of the VLT Planet Finder SPHERE II. Data analysis and results for IFS in laboratory
Aims. We present the performance of the Integral Field Spectrograph (IFS) of SPHERE, the high-contrast imager for the ESO VLT telescope designed to perform imaging and spectroscopy of extrasolar planets, obtained from tests performed at the Institut de Planetologie et d'Astrophysique de Grenoble facility during the integration phase of the instrument. Methods. The tests were performed using the instrument software purposely prepared for SPHERE. The output data were reduced applying the SPHERE data reduction and handling software, adding an improved spectral deconvolution procedure. To this aim, we prepared an alternative procedure for the spectral subtraction exploiting the principal component analysis algorithm. Moreover, a simulated angular differential imaging procedure was also implemented to estimate how the instrument performed once this procedure was applied at telescope. The capability of the IFS to faithfully retrieve the spectra of the detected faint companions was also considered. Results. We found that the application of the updated version of the spectral deconvolution procedure alone, when the algorithm throughput is properly taken into account, gives us a 5 sigma limiting contrast of the order of 5 x 10(-6) or slightly better. The further application of the angular differential imaging procedure on these data should allow us to improve the contrast by one order of magnitude down to around 7x10(-7) at a separation of 0.3 arcsec. The application of a principal component analysis procedure that simultaneously uses spectral and angular data gives comparable results. Finally, we found that the reproducibility of the spectra of the detected faint companions is greatly improved when angular differential imaging is applied in addition to the spectral deconvolution.
(Astronomy & Astrophysics - A&A. vol. 576, n° 0004-6361, 01/04/2015)
GSFC, IPAG, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNES, CNRS, OAPD, INAF, LAM, AMU, INSU - CNRS, CNES, CNRS, ObsGE, UNIGE, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, LESIA, UPMC, INSU - CNRS, CNRS, PSL, UPD7, CNRS, MPIA, TUM, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CFHT, INSU - CNRS, NRC, CNRS, UH
Potential denitrification rates are spatially linked to colonization patterns of nosZ genotypes in an alluvial wetland
Through denitrification, attached bacterial communities reduce water nitrogen loads during transport from land to river. In an in situ colonization experiment, spatial and temporal dynamics in composition of bacterial communities and denitrification activity were studied in bacterial biofilms in an alluvial aquifer. Mesh bags with glass beads were installed in different wells in an alluvial aquifer affected by surface water fluxes from an adjacent river and biofilms were sampled throughout the 15-month experiment. By combining structural (PCR-DGGE using nosZ genes) and functional (Denitrification Enzyme Activity measurements) descriptors, the denitrifiers community structure of biofilms and their functional responses were studied. Denitrifiers bacterial community composition developed on beads linked to denitrification capability were correlated with the modeled load of dissolved organic carbon coming from the river and dissolved oxygen concentration, which were set by the river channel water flow through the aquifer.
(Ecological Engineering. vol. 80, n° 0925-8574, pp. 191-197, 18/03/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Decadal Changes in South Pacific Sea Surface Temperatures and the Relationship to the Pacific Decadal Oscillation and Upper Ocean Heat Content: Decadal Changes in South Pacific SST
Decadal changes in Pacific sea surface temperatures (SST) and upper ocean heat content (OHC) remain poorly understood. We present an annual average composite coral Sr/Ca-derived SST time-series extending back to 1791 from Fiji, Tonga and Rarotonga (FTR) in the Pacific Decadal Oscillation (PDO) sensitive region of the Southwest Pacific. Decadal SST maxima between 1805 and 1830 C.E. indicate unexplained elevated SSTs near the end of the Little Ice Age. The mean period of decadal SST variability in this region has a period near 25 years. Decades of warmer (cooler) FTR SST co-occur with PDO negative (positive) phases since at least ~1930 C.E. and positively correlate with South Pacific OHC (0-700m). FTR SST is also inversely correlated with decadal changes in equatorial Pacific SST as measured by coral Sr/Ca. Collectively, these results support the fluctuating trade wind-shallow meridional overturning cell mechanism for decadal modulation of Pacific SSTs and OHC.
(Geophysical Research Letters. vol. 42, n° 0094-8276, pp. 2358-2366, 01/03/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS