Contingencies of environmental justice: the case of individual mobility and Grenoble’s Low-Emission Zone     

Laure Charleux 《Urban geography》2013,34(2):197-218

Low-emission zones (LEZs) are core urban areas where vehicles that are deemed especially polluting are prohibited, in the hope of reducing the population’s exposure to outdoor air pollution. LEZs have proliferated in Europe during the past decade. While an emerging body of literature considers LEZs’ impacts on pollution, studies thus far have not tackled LEZs’ impacts on mobility. This article uses household-travel survey data to assess how a projected LEZ in Grenoble, France could affect individuals’ mobility, specifically enquiring whether or not the impact would be socially differentiated and might constitute a social injustice. Four likely scenarios are considered and logistic regressions show that, indeed, the probability that people will be affected by the LEZ is related to their social group. However, interpretations in terms of social justice may vary, depending on the reference population considered and hypotheses regarding the reduction of pollution exposure.  相似文献   

A modification of the time-geographic framework to support temporal flexibility in ‘fixed’ activities     

Laure Charleux 《International journal of geographical information science》2013,27(7):1125-1143

The time-geographic distinction between fixed and flexible activities is widely acknowledged to be a somewhat arbitrary dichotomy but is still the current modus operandi for time-geographic calculations. This paper proposes a modification of the classic time-geographic framework to support temporal flexibility in ‘fixed’ activities. This modification is crucial for time-geographic calculations on public transit networks with a low frequency of service, which would otherwise return unstable results.  相似文献   

Turn calculations for the indoor application of the fewest turns path algorithm     

Ann Vanclooster  Nina Vanhaeren  Pepijn Viaene  Kristien Ooms  Laure De Cock  Veerle Fack 《International journal of geographical information science》2013,27(11):2284-2304

ABSTRACT

Present-day indoor navigation systems are often not well adapted to the specific needs and requirements of its users. This research aims at improving those indoor navigation systems by providing navigation support that cognitively closer to user preferences and behaviour. More specifically, the focus is on the implementation of an accurate turn calculation method in a turn minimization algorithm, aiming to lower the complexity of routes and route instructions. This new-introduced perception-based turn calculation procedure is based on a direct door-to-door walking pattern, and, in contrast to previous algorithms, independent of the underlying indoor network type. It takes into account the effects of geometry of indoor space on human movement. To evaluate its functioning, both the traditional algorithm and the proposed perception-based algorithm are applied in the fewest turns path algorithm. It is demonstrated that the proposed algorithm accurately calculates turns in alignment with people’s perception. The implementation of the calculation algorithm in the fewest turns path algorithm also allows future applications in indoor simplest path algorithms, and overall contributes to cognitively richer indoor navigation systems.  相似文献   

The suitability of annual tree growth rings as environmental archives: Evidence from Sr,Nd, Pb and Ca isotopes in spruce growth rings from the Strengbach watershed     

Peter Stille  Anne-Désirée Schmitt  François Labolle  Marie-Claire Pierret  Sophie Gangloff  Florian Cobert  Eric Lucot  Florence Guéguen  Laure Brioschi  Marc Steinmann  François Chabaux 《Comptes Rendus Geoscience》2012,344(5):297-311

The combination of the Sr, Nd and Pb isotope systems, recognized as tracers of sources, with the Ca isotope system, known to reveal biology-related fractionations, allowed us to test the reliability of spruce (Picea abies) growth rings as environmental archives through time (from 1916 to 1983) in a forest ecosystem affected by acid atmospheric deposition. Sr and Pb isotopes have already been applied in former tree-ring studies, whereas the suitability of Nd and Ca isotope systems is checked in the present article. Our Sr and Nd isotope data indicate an evolution in the cation origin with a geogenic origin for the oldest rings and an atmospheric origin for the youngest rings. Ca isotopes show, for their part, an isotopic homogeneity which could be linked to the very low weathering flux of Ca. Since this flux is weak the spruces’ root systems have pumped the Ca mainly from the organic matter-rich top-soil over the past century. In contrast, the annual growth rings studied are not reliable and suitable archives of past Pb pollution.  相似文献   

New UPb zircon ages from Tonga (Cameroon): coexisting Eburnean–Transamazonian (2.1 Ga) and Pan-African (0.6 Ga) imprints     

Evine Laure Tanko Njiosseu  Jean-Paul Nzenti  Théophile Njanko  Badibanga Kapajika  Anne Nédélec 《Comptes Rendus Geoscience》2005,337(6):551-562

The central domain of the Pan-African Belt in Cameroon is characterized by abundant porphyritic granitoids, which were emplaced synkinematically and variably orthogneissified in relation with ENE-striking steeply dipping transcurrent shear zones. These plutonic rocks have intermediate to felsic compositions and constitute a high-K calk-alkaline series. Conventional UPb zircon dating yields an age of 618 Ma for this syntectonic Pan-African magmatism in the Tonga area. The country rocks are made of metabasites (garnet amphibolites) and tonalitic to trondhjemitic gneisses, which suffered two distinct orogenic cycles: the first one is the Palaeoproterozoic Eburnean–Transamazonian cycle at 2.1 Ga and the second one is the Pan-African orogenesis. These new ages confirm the existence of an extensive Palaeoproterozoic crust in Cameroon and question the areal extent of the Congo–São Francisco craton towards the north. To cite this article: E.L. Tanko Njiosseu et al., C. R. Geoscience 337 (2005).  相似文献   

Post-depositional realignment of magnetic grains and asymmetrical saw-tooth patterns of magnetization intensity     

Laure Meynadier  Jean-Pierre Valet 《Earth and Planetary Science Letters》1996,140(1-4):123-132

Recent paleomagnetic records suggest that the geomagnetic field intensity has a saw-tooth shape matching the succession of polarity intervals. An alternative hypothesis, that mechanisms linked to the acquisition of magnetization would induce similar saw-toothed records, has been tested by several simulations of post depositional reorientations of magnetic grains. Exponential functions used to date to describe post-depositional magnetization (pDRM) processes do not account for the combination of saw-toothed fluctuations and reasonable delays in the recording of the position of the reversals. At least half of the magnetization must be locked in within a few centimetres below the surface. If not, large delays, which are not observed in the data, are introduced in the stratigraphic positions of the reversals. In addition, the rest of the magnetization must be acquired over depths involving several tens of meters to duplicate a saw-toothed shape. These conclusions are reached with or without incorporating intensity variations across reversals. If the original signal is, in fact, asymmetrical then the pDRM must be very limited to remain coherent with the measurements, since the distortions and the offsets induced by the pDRM smoothing are considerably amplified. We conclude that simulations of saw-tooth patterns of relative paleointensity by pDRM processes have consequences that are difficult to reconcile with our present knowledge of the physical properties of deep-sea sediments. Above all, the hypothesis that the saw-tooth is an artifact of the magnetization acquisition process would have major implications for any sedimentary record of geomagnetic features.  相似文献   

The Lithium, Boron and Beryllium content of serpentinized peridotites from ODP Leg 209 (Sites 1272A and 1274A): Implications for lithium and boron budgets of oceanic lithosphere   总被引：2，自引：0，他引：2  

Flurin Vils  Laure Pelletier  Othmar Müntener 《Geochimica et cosmochimica acta》2008,72(22):5475-5504

Despite the key importance of altered oceanic mantle as a repository and carrier of light elements (B, Li, and Be) to depth, its inventory of these elements has hardly been explored and quantified. In order to constrain the systematics and budget of these elements we have studied samples of highly serpentinized (>50%) spinel harzburgite drilled at the Mid-Atlantic Ridge (Fifteen-Twenty Fracture zone, ODP Leg 209, Sites 1272A and 1274A). In-situ analysis by secondary ion mass spectrometry reveals that the B, Li and Be contents of mantle minerals (olivine, orthopyroxene, and clinopyroxene) remain unchanged during serpentinization. B and Li abundances largely correspond to those of unaltered mantle minerals whereas Be is close to the detection limit. The Li contents of clinopyroxene are slightly higher (0.44-2.8 μg g⁻¹) compared to unaltered mantle clinopyroxene, and olivine and clinopyroxene show an inverse Li partitioning compared to literature data. These findings along with textural observations and major element composition obtained from microprobe analysis suggest reaction of the peridotites with a mafic silicate melt before serpentinization. Serpentine minerals are enriched in B (most values between 10 and 100 μg g⁻¹), depleted in Li (most values below 1 μg g⁻¹) compared to the primary phases, with considerable variation within and between samples. Be is at the detection limit. Analysis of whole rock samples by prompt gamma activation shows that serpentinization tends to increase B (10.4-65.0 μg g⁻¹), H₂O and Cl contents and to lower Li contents (0.07-3.37 μg g⁻¹) of peridotites, implying that—contrary to alteration of oceanic crust—B is fractionated from Li and that the B and Li inventory should depend essentially on rock-water ratios. Based on our results and on literature data, we calculate the inventory of B and Li contained in the oceanic lithosphere, and its partitioning between crust and mantle as a function of plate characteristics. We model four cases, an ODP Leg 209-type lithosphere with almost no igneous crust, and a Semail-type lithosphere with a thick igneous crust, both at 1 and 75 Ma, respectively. The results show that the Li contents of the oceanic lithosphere are highly variable (17-307 kg in a column of 1 m × 1 m × thickness of the lithosphere (kg/col)). They are controlled by the primary mantle phases and by altered crust, whereas the B contents (25-904 kg/col) depend entirely on serpentinization. In all cases, large quantities of B reside in the uppermost part of the plate and could hence be easily liberated during slab dehydration. The most prominent input of Li into subduction zones is to be expected from Semail-type lithosphere because most of the Li is stored at shallow levels in the plate. Subducting an ODP Leg 209-type lithosphere would mean only very little Li contribution from the slab. Serpentinized mantle thus plays an important role in B recycling in subduction zones, but it is of lesser importance for Li.  相似文献   

Assessment of a field incubation method estimating primary productivity in rockpool communities     

Laure M.-L.J. Noël  John N. Griffin  Richard C. Thompson  Stephen J. Hawkins  Michael T. Burrows  Tasman P. Crowe  Stuart R. Jenkins 《Estuarine, Coastal and Shelf Science》2010

An open incubation method has been used in many studies to directly estimate primary productivity and ecosystem functioning by measuring photosynthetic and respiratory rates in intertidal rockpool communities. The method measures changes in dissolved oxygen concentrations recorded in situ during an artificial dark period (respiration) and a natural light period (net primary productivity). Although this method has yielded interesting results, its advantages and limitations have yet to be thoroughly tested. The accuracy of the method was investigated in a controlled laboratory environment and compared with field incubations. Atmospheric oxygen diffusion across the air–water interface did not affect incubation measurements under low wind speed (<2 m s⁻¹). Temperature increases during incubations were not greater than in natural rockpools and did not affect primary productivity. The major problem was the oxygen supersaturation which inhibited photosynthesis, thus leading to an underestimation of primary production. To allow comparable measurements, net primary productivity needs to be recorded during the linear phase of the photosynthetic process (<30 min of light) before water reaches supersaturation (<160%). This method gives rapid and reliable estimates of primary productivity thereby allowing biodiversity and ecosystem functioning relationships to be tested using rockpools as natural mesocosms.  相似文献   

Lipid biomarkers and bacterial lipase activities as indicators of organic matter and bacterial dynamics in contrasted regimes at the DYFAMED site, NW Mediterranean     

Nicolas Bourguet  Madeleine Goutx  Jean-Franois Ghiglione  Mireille Pujo-Pay  Genevive Mvel  Andr Momzikoff  Laure Mousseau  Catherine Guigue  Nicole Garcia  Patrick Raimbault  Romain Pete  Louise Oriol  Dominique Lefvre 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1454-1469

This study investigated the relationships between dissolved organic matter (DOM) composition and bacterial dynamics on short time scale during spring mesotrophic (March 2003) and summer oligotrophic (June 2003) regimes, in a 0–500 m depth water column with almost no advection, at the DYFAMED site, NW Mediterranean. DOM was characterized by analyzing dissolved organic carbon (DOC), colored dissolved organic matter (CDOM) and lipid class biotracers. Bacterial dynamic was assessed through the measurement of in situ bacterial lipase activity, abundance, production and bacterial community structure. We made the assumption that by coupling the ambient concentration of hydrolysable acyl-lipids with the measurement of their in situ bacterial hydrolysis rates (i.e. the free fatty acids release rate) would provide new insights about bacterial response to change in environmental conditions. The seasonal transition from spring to summer was accompanied by a significant accumulation of excess DOC (+5 μM) (ANOVA, p<0.05, n=8) in the upper layer (0–50 m). In this layer, the free fatty acids release rate to the bacterial carbon demand (BCD) ratio increased from 0.6±0.3 in March to 1.3±1.0 in June (ANOVA, p<0.05, n=8) showing that more uncoupling between the hydrolysis of the acyl-lipids and the BCD occurred during the evolution of the season, and that free fatty acids contributed to the excess DOC. The increase of lipolysis index and CDOM absorbance (from 0.24±0.17 to 0.39±0.13 and from 0.076±0.039 to 0.144±0.068; ANOVA, p<0.05, n=8, respectively), and the higher contribution of triglycerides, wax esters and phospholipids (from <5% to 12–31%) to the lipid pool reflected the change in the DOM quality. In addition to a strong increase of bacterial lipase activity per cell (51.4±29.4–418.3±290.6 Ag C cell⁻¹ h⁻¹), a significant percentage of ribotypes (39%) was different between spring and summer in the deep chlorophyll maximum (DCM) layer in particular, suggesting a shift in the bacterial community structure due to the different trophic conditions. At both seasons, in the chlorophyll layers, diel variations of DOM and bacterial parameters reflected a better bioavailability and/or DOM utilization by bacteria at night (the ratio of free fatty acids release rate to bacterial carbon demand decreased), most likely related to the zooplankton trophic behaviour. In mesotrophic conditions, such day/night pattern was driving changes in the bacterial community structure. In more oligotrophic period, diel variations in bacterial community structure were depth dependent in relation to the strong summer stratification.  相似文献   

Coniferization of the mixed‐wood boreal forests under warm climate     

Ccile C. Remy  Dominic Senici  Han Y. H. Chen  Yves Bergeron  Martin Lavoie  Laure Paradis  Adam A. Ali 《第四纪科学杂志》2019,34(7):509-518

Mixed‐wood boreal forests are characterized by a heterogeneous landscape dominated by coniferous or deciduous species depending on stand moisture and fire activity. Our study highlights the long‐term drivers of these differences between landscapes across mixed‐wood boreal forests to improve simulated vegetation dynamics under predicted climate changes. We investigate the effects of main climate trends and wildfire activities on the vegetation dynamics of two areas characterized by different stand moisture regimes during the last 9000 years. We performed paleofire and pollen analyses in the mixed‐wood boreal forest of north‐western Ontario, derived from lacustrine sediment deposits, to reconstruct historical vegetation dynamics, which encompassed both the Holocene climatic optimum (ca. 8000–4000 a bp ) and the Neoglacial period (ca. 4000 a bp ). The past warm and dry period (Holocene climatic optimum) promoted higher fire activity that resulted in an increase in coniferous species abundance in the xeric area. The predicted warmer climate and an increase in drought events should lead to a coniferization of the xeric areas affected by high fire activity while the mesic areas may retain a higher broadleaf abundance, as these areas are not prone to an increase in fire activity. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献