LES ROCHES ERUPTIVES POST-PALEOZOIQUES DU NORD DE LA CHINE     

Par Teilhard de Chardin 《地质学报》1928,7(1):1-11

Les Ioches dont l'etude petrograpmque par M. Lacroix fait l'objet principal de la communication suivante, ont ete recueillies, soit par M. Lacroix lui-meme, soit par M. G. B. Barbour, soit surtout par nous-memes. (P. Teilhard  相似文献   

Assessing sedimentation in a temperate dystrophic lake in the NE Atlantic seaboard region     

C. Dalton  K. Sparber  E. de Eyto 《Journal of Paleolimnology》2018,60(2):117-131

Organic materials deposited in lacustrine environments can be derived from both aquatic and terrestrial ecosystems, and can serve as valuable indicators of catchment and in-lake ecological changes over time. However, spatial and temporal variation in the deposition of these materials within a lake basin will influence the interpretation of these sediment deposits. In this study, materials deposited in suspended sediment traps and basin sediments in Lough Feeagh, a temperate coastal humic lake, show variations in organic matter, total organic carbon and nitrogen loads, algal pigment concentrations and diatom assemblages. Sediment trap samples from three locations along with adjacent surface sediment cores show a clear north–south (inlet to outlet) gradient. C/N ratios reflected a mixture of algal and land-derived organic matter with a major peat influence, and comparisons between sediment trap and surface sediment assemblages revealed pigment and diatom assemblages influenced by lake-basin position and water depth. While some coherency between trap and sediment samples was apparent a more complicated biological response is demonstrated along with reduced water clarity in recent years thus highlighting the implications of increased allochthonous imputs for biological and biogeochemical processes in oligo-humic aquatic systems.  相似文献   

Depiction of Wild Food Foraging Practices in the Media: Impact of the Great Recession     

Sonya Sachdeva  Marla R. Emery  Patrick T. Hurley 《社会与自然资源》2018,31(8):977-993

The practice of gathering and harvesting wild foods has seen renewed interest in recent decades. In addition to contributing to food security and food sovereignty, foraging plays a role in promoting socioecological resilience and creating communities of belonging. However, foraging is generally prohibited by regulations governing public lands in the United States and elsewhere. The growth in food forests suggests public policymakers and land managers’ may be interested in reconsidering this broad prohibition of foraging but require an information base to do so. While a body of research on foraging exists, news media coverage of foraging represents an additional, readily available source of input. As a consequence, framings of foraging in media coverage likely influence managers’ deliberations on this practice. The current paper uses automated content analysis to understand how the practice of gathering and consuming wild foods is framed in print and digital news media, and how these depictions have varied in a 15-year period that includes the Great Recession. Our results show that prevalent framings of foraging represent it variously as a self-provisioning practice or a source of luxury commodities and experiences, with economic uncertainty appearing to affect the frequency of each framing by news media sources. Given managers’ ease of access to them, these distinct framings may influence future regulatory landscapes of foraging.  相似文献   

Formal representation of qualitative direction     

Christian Freksa  Jasper van de Ven  Diedrich Wolter 《International journal of geographical information science》2018,32(12):2514-2534

This paper reviews formal approaches to representing spatial knowledge about qualitative direction. Unlike geometric direction information, qualitative information does not employ numerical values but relies on comparison. The qualitative approach is often regarded as suitable for capturing commonsense concepts and thus is relevant to human-centered interfaces for spatial information systems. To establish a context for the work on qualitative direction, we preset a brief history of the development of qualitative temporal and spatial representations from different scientific perspectives. We identify main focal areas of these representations of spatial direction and propose a taxonomy. In the light of more than three decades of fruitful research, we obtain a map of formal representations that reveal interrelationships between different research strands in the field.  相似文献   

High-resolution mass spectrometric characterization of dissolved organic matter from warm and cold periods in the NEEM ice core     

JianZhong Xu  Amanda Grannas  CunDe Xiao  ZhiHeng Du  Amanda Willoughby  Patrick Hatcher  YanQing An 《寒旱区科学》2018,10(1):38-46

Dissolved organic matter(DOM) is an important component of ice cores but is currently poorly characterized. DOM from one Holocene sample(HS, aged at 1600–4500 B.P.) and one Last Glacial Maximum sample(LS, aged at 21000–25000 B.P.) from the North Greenland Eemian Ice Drilling(NEEM) ice core were analyzed by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS). CHO compounds contributed 50% of the compounds identified in negative-ionization mode in these two samples, with significant contributions from organic N, S, and P compounds, likely suggesting that marine DOM was an important source in these samples. Overall, the chemical compositions are similar between these two samples, suggesting their consistent DOM sources. However, subtle differences in the DOM between these two samples are apparent and could indicate differences in source strength or chemistry occurring through both pre-and post-depositional processes. For example, higher relative amounts of condensed carbon compounds in the HS DOM(5%), compared to the LS DOM(2%), suggest potentially important contributions from terrestrial sources. Greater incorporation of P in the observed DOM in the LS DOM(22%), compared to the HS DOM(13%), indicate more active microbiological processes that likely contribute to phosphorus incorporation into the DOM pool. Although these two samples present only a preliminary analysis of DOM in glacial/interglacial periods, the data indicate a need to expand the analysis into a broader range of ice-core samples, geographical locations, and glacial/interglacial periods.  相似文献   

Evaluation of methods of spatial interpolation for monthly rainfall data over the state of Rio de Janeiro,Brazil     

Gustavo?Bastos?Lyra  Tamíres?Partelli?Correia  José?Francisco?de?Oliveira-Júnior  Marcelo?ZeriEmail authorView author&#;s OrcID profile 《Theoretical and Applied Climatology》2018,134(3-4):955-965

Five deterministic methods of spatial interpolation of monthly rainfall were compared over the state of Rio de Janeiro, southeast Brazil. The methods were the inverse distance weight (IDW), nearest neighbor (NRN), triangulation with linear interpolation (TLI), natural neighbor (NN), and spline tension (SPT). A set of 110 weather stations was used to test the methods. The selection of stations had two criteria: time series longer than 20 years and period of data from 1960 to 2009. The methods were evaluated using cross-validation, linear regression between values observed and interpolated, root mean square error (RMSE), coefficient of determination (r ²), coefficient of variation (CV, %), and the Willmott index of agreement (d). The results from different methods are influenced by the meteorological systems and their seasonality, as well as by the interaction with the topography. The methods presented higher precision (r ²) and accuracy (d, RMSE) during the summer and transition to autumn, in comparison with the winter or spring months. The SPT had the highest precision and accuracy in relation to other methods, in addition to having a good representation of the spatial patterns expected for rainfall over the complex terrain of the state and its high spatial variability.  相似文献   

Photochemical activation of chlorine by iron-oxide aerosol     

Julian?WittmerEmail author  Cornelius?ZetzschEmail author 《Journal of Atmospheric Chemistry》2017,74(2):187-204

The photochemical activation of chlorine by dissolved iron in artificial sea-salt aerosol droplets and by highly dispersed iron oxide (Fe₂O₃) aerosol particles (mainly hematite, specific surface ~150 m² g^?1) exposed to gaseous HCl, was investigated in humidified air in a Teflon simulation chamber. Employing the radical-clock technique, we quantified the production of gaseous atomic chlorine (Cl) from the irradiated aerosol. When the salt aerosol contained Fe₂O₃ at pH 6, no significant Cl production was observed, even if the dissolution of iron was forced by “weathering” (repeatedly freezing and thawing for five times). Adjusting the pH in the stock suspension to 2.6, 2.2, and 1.9 and equilibrating for one week resulted in a quantifiable amount of dissolved iron (0.03, 0.2, and 0.6 mmol L^?1, respectively) and in gaseous Cl production rates of ~1.6, 6, and 8?×?10²¹ atoms cm^?2 h^?1, respectively. In a further series of experiments, the pure Fe₂O₃ aerosol was exposed to various levels of gaseous hydrogen chloride (HCl). The resulting Cl production rates ranged from 8?×?10²⁰ Cl atoms cm^?2 h^?1 (at ~4 ppb HCl) to 5?×?10²² Cl atoms cm^?2 h^?1 (at ~350 ppb HCl) and confirmed the uptake and conversion of HCl to atomic Cl (at HCl to Cl conversion yields of 2–5 %, depending on the relative humidity). The Fe₂O₃ experiments indicate that iron-induced Cl formation may be important for highly soluble combustion-aerosol particles in marine environments in the presence of gaseous HCl.  相似文献   

Performance of the WRF model to simulate the seasonal and interannual variability of hydrometeorological variables in East Africa: a case study for the Tana River basin in Kenya     

Kerandi  Noah Misati  Laux  Patrick  Arnault  Joel  Kunstmann  Harald 《Theoretical and Applied Climatology》2017,130(1-2):401-418

This study investigates the ability of the regional climate model Weather Research and Forecasting (WRF) in simulating the seasonal and interannual variability of hydrometeorological variables in the Tana River basin (TRB) in Kenya, East Africa. The impact of two different land use classifications, i.e., the Moderate Resolution Imaging Spectroradiometer (MODIS) and the US Geological Survey (USGS) at two horizontal resolutions (50 and 25 km) is investigated. Simulated precipitation and temperature for the period 2011–2014 are compared with Tropical Rainfall Measuring Mission (TRMM), Climate Research Unit (CRU), and station data. The ability of Tropical Rainfall Measuring Mission (TRMM) and Climate Research Unit (CRU) data in reproducing in situ observation in the TRB is analyzed. All considered WRF simulations capture well the annual as well as the interannual and spatial distribution of precipitation in the TRB according to station data and the TRMM estimates. Our results demonstrate that the increase of horizontal resolution from 50 to 25 km, together with the use of the MODIS land use classification, significantly improves the precipitation results. In the case of temperature, spatial patterns and seasonal cycle are well reproduced, although there is a systematic cold bias with respect to both station and CRU data. Our results contribute to the identification of suitable and regionally adapted regional climate models (RCMs) for East Africa.

  相似文献   

Early Warning Signals for Regime Transition in the Stable Boundary Layer: A Model Study     

I. G. S. van Hooijdonk  A. F. Moene  M. Scheffer  H. J. H. Clercx  B. J. H. van de Wiel 《Boundary-Layer Meteorology》2017,162(2):283-306

The evening transition is investigated in an idealized model for the nocturnal boundary layer. From earlier studies it is known that the nocturnal boundary layer may manifest itself in two distinct regimes, depending on the ambient synoptic conditions: strong-wind or overcast conditions typically lead to weakly stable, turbulent nights; clear-sky and weak-wind conditions, on the other hand, lead to very stable, weakly turbulent conditions. Previously, the dynamical behaviour near the transition between these regimes was investigated in an idealized setting, relying on Monin–Obukhov (MO) similarity to describe turbulent transport. Here, we investigate a similar set-up, using direct numerical simulation; in contrast to MO-based models, this type of simulation does not need to rely on turbulence closure assumptions. We show that previous predictions are verified, but now independent of turbulence parametrizations. Also, it appears that a regime shift to the very stable state is signaled in advance by specific changes in the dynamics of the turbulent boundary layer. Here, we show how these changes may be used to infer a quantitative estimate of the transition point from the weakly stable boundary layer to the very stable boundary layer. In addition, it is shown that the idealized, nocturnal boundary-layer system shares important similarities with generic non-linear dynamical systems that exhibit critical transitions. Therefore, the presence of other, generic early warning signals is tested as well. Indeed, indications are found that such signals are present in stably stratified turbulent flows.  相似文献   

The impacts of a plume-rise scheme on earth system modeling: climatological effects of biomass aerosols on the surface temperature and energy budget of South America     

de Menezes Neto  Otacilio L.  Coutinho  Mariane M.  Marengo  José A.  Capistrano  Vinícius B. 《Theoretical and Applied Climatology》2017,129(3-4):1035-1044

Theoretical and Applied Climatology - Seasonal forest fires in the Amazon are the largest source of pollutants in South America. The impacts of aerosols due to biomass burning on the temperature...  相似文献