Tissue distribution of metals in loggerhead turtles (Caretta caretta) stranded in the Canary Islands, Spain     

Torrent A  González-Díaz OM  Monagas P  Orós J 《Marine pollution bulletin》2004,49(9-10):854-860

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Lidar and Sun photometer observations of atmospheric boundary-layer characteristics over an urban area in a mountain valley     

Nikolay Kolev  Ivan Grigorov  Ivan Kolev  P. C. S. Devara  P. Ernest. Raj  K. K. Dani 《Boundary-Layer Meteorology》2007,124(1):99-115

We present measurements of the vertical aerosol structure and the aerosol optical depth in the lower troposphere performed above the city of Sofia (an urban area situated in a mountain valley), western Bulgaria by means of a ground-based aerosol lidar operating continuously for a number of years. The lidar measurements were accompanied by measurements of the aerosol optical depth (AOD) in the visible and near infrared regions of the spectrum performed in October 2004 using Microtops II radiometers. The maximum values of the AOD were found to occur 1–2 h before the complete development of the atmospheric boundary layer, i.e. during the residual layer destruction, which confirms our hypothesis concerning the slope circulation effect on the processes taking place in the atmospheric boundary layer. The AOD values obtained by the lidar are lower than those taken by the sun photometer. Further, the AOD exhibits two different types of behaviour. In the case of a ‘clear atmosphere’ (i.e. in the absence of volcanic eruptions and/or dust transport from the Sahara) most of the aerosol accumulated within the atmospheric boundary layer over the urban area considered. The combined use of the two instruments allows the comparison between the optical characteristics of the atmospheric aerosol (e.g. aerosol extinction coefficient, etc.) obtained by the lidar and through an independent method (sun photometer).  相似文献   

森林水文服务市场开发的案例分析     

Danièle Perrot-Maitre 《湿地科学与管理》2002,(4):44-55

<正> 制定合理的管理措施,有助于提供和加强森林的水文服务功能。这些功能包括改良水质、增加干旱季节的径流量、调节地表水与地下水、提高水生生物生产力等。尽管这些功能是最重要的森林生态功能之一,但直到最近,这些功能仍被认为是由林场主免费提供而被排除在市场框架之外。  相似文献   

Hydrogeological investigation in the Mekong Delta around Ho-Chi-Minh City (South Vietnam) by electric tomographyInvestigation hydrogéologique dans le delta du Mékong,autour de la ville de Ho-Chi-Minh (Sud-Vietnam), par tomographie électrique     

Van Ngoc Pham  Danièle Boyer  Jean-Louis Le Mouël  Thi Kim Thoa Nguyen 《Comptes Rendus Geoscience》2002,334(10):733-740

In the Mekong Delta (South Vietnam), the agglomeration of Ho-Chi-Minh (HCM) City, with more than 5 million inhabitants, is confronted with a dramatic shortage of fresh water supply because of the pollution of several aquifers at different depths. The electric tomography, obtained by concurrent inversion of two complementary geoelectrical methods, the Vertical Electrical Sounding (VES) and the Magneto-Telluric Sounding (MTS), turned out to be very efficient to provide a complete electrical image of the underground from the surface until about 800 m depth. This methodology constitutes a very cheap guide for the evaluation of the quality of the groundwater resources in the vast alluvial plain of the Mekong Delta. To cite this article: V.N. Pham et al., C. R. Geoscience 334 (2002) 733–740.  相似文献   

Characteristics of Turbulent Airflow Deduced from Rapid Surface Thermal Fluctuations: An Infrared Surface Anemometer     

Milad Aminzadeh  Daniel Breitenstein  Dani Or 《Boundary-Layer Meteorology》2017,165(3):519-534

The intermittent nature of turbulent airflow interacting with the surface is readily observable in fluctuations of the surface temperature resulting from the thermal imprints of eddies sweeping the surface. Rapid infrared thermography has recently been used to quantify characteristics of the near-surface turbulent airflow interacting with the evaporating surfaces. We aim to extend this technique by using single-point rapid infrared measurements to quantify properties of a turbulent flow, including surface exchange processes, with a view towards the development of an infrared surface anemometer. The parameters for the surface-eddy renewal (\(\alpha \) and \(\beta )\) are inferred from infrared measurements of a single-point on the surface of a heat plate placed in a wind tunnel with prescribed wind speeds and constant mean temperatures of the surface. Thermally-deduced parameters are in agreement with values obtained from standard three-dimensional ultrasonic anemometer measurements close to the plate surface (e.g., \(\alpha = 3\) and \(\beta = 1/26~\hbox {(ms)}^{-1}\) for the infrared, and \(\alpha = 3\) and \(\beta = 1/19~\hbox {(ms)}^{-1}\) for the sonic-anemometer measurements). The infrared-based turbulence parameters provide new insights into the role of surface temperature and buoyancy on the inherent characteristics of interacting eddies. The link between the eddy-spectrum shape parameter \(\alpha \) and the infrared window size representing the infrared field of view is investigated. The results resemble the effect of the sampling height above the ground in sonic anemometer measurements, which enables the detection of larger eddies with higher values of \(\alpha \). The physical basis and tests of the proposed method support the potential for remote quantification of the near-surface momentum field, as well as scalar-flux measurements in the immediate vicinity of the surface.  相似文献   

Linking rainfall-induced landslides with predictions of debris flow runout distances     

Jonas von Ruette  Peter Lehmann  Dani Or 《Landslides》2016,13(5):1097-1107

Rapid debris flows are among the most destructive natural hazards in steep mountainous terrains. Prediction of their path and impact hinges on knowledge of initiation location and the size and constitution of the released mass. To better link mass release initiation with debris flow paths and runout lengths, we propose to capitalize on a newly developed model for rainfall-induced landslide initiation (“Catchment-scale Hydro-mechanical Landslide Triggering” CHLT model, von Ruette et al. 2013) and couple it with simple estimates of debris flow runout distances and pathways. Landslide locations and volumes provided by the CHLT model are used as inputs to simulate debris flow runout distances with two empirical- and two physically-based models. The debris flow runout models were calibrated using two landslide inventories in the Swiss Alps obtained following a large rainfall event in 2005. We first fitted and tested the models for the “Prättigau” inventory, where detailed information on runout path was available, and then applied the models to landslides inventoried from a different catchment (“Napf”). The predicted debris flow runout distances (emanating from CHLT simulated landslide positions) were well in the range of observed values for the physically-based approaches. The empirical approaches tend to overestimate runout distances relative to observations. These preliminary results demonstrate the added value of linking shallow landslide triggering models with predictions of debris flow runout pathways for a range of soil states and triggering events, thus providing a more complete hazard assessment picture for debris flow exposure at the catchment scale.  相似文献   

Tropical atmospheric stability and wind structures as inferred from the Indian MST radar observations     

P. C. S. Devara  P. E. Raj  G. Pandithurai  K. K. Dani 《Meteorology and Atmospheric Physics》1997,64(3-4):173-186

Summary The MST (Mesosphere-Stratosphere-Tropospher) Radar Facility at Gadanki (13.47° N, 79.18° E), near Tirupati, Andhra Pradesh, India has been operated over seven diurnal cycles—three in November 1994, one in September 1995 and three in January–February 1996 with an objective to study the wind and stability characteristics in the troposphere and lower-stratosphere. The radar-measured height profiles of both zonal (EW) and meridional (NS) wind components and near-simultaneous radiosonde measurements from Madras (13.04° N, 80.7° E) and Bangalore (12.85° N, 77.58° E), the two stations close to either side of the radar site, have been compared and they are found to be in gross agreement within the limitations of the sensing techniques.The results of the study also indicated multiple stable and turbulent structures/stratification throughout the height region from about 4 to 30 km. It is noticed that the stable layers are well marked around the altitudes 4 km, 12 km and the tropopause while the turbulent layers exist a few kilometers below the tropopause. These stable and turbulent layer structures showed good correspondence with the radar-measured wind gradients and also with the radiosonde-derived temperature and wind distributions over Madras. The maximum positive gradient in the signal-tonoise ratio (SNR) which corresponds to radar tropopause is found to coincide with the greater potential temperature gradient and smaller wind gradient. The time evolution of atmospheric stability structure, derived from the SNR, spectral width and vertical wind revealed a diffused tropopause or tropopause weakening which is found to be associated with broader spectral width and larger gradients of winds. This feature is considered to be due either to the instability associated with large vertical gradients in horizontal winds (dynamical instability) or to the instability generated by the convection (convective instability).With 6 Figures  相似文献   

The role of trace elements in controlling H incorporation in San Carlos olivine     

Peter?M.?E.?TollanEmail authorView author&#;s OrcID profile  Hugh?St.?C.?O’Neill  J?rg?Hermann 《Contributions to Mineralogy and Petrology》2018,173(11):89

We conducted a series of hydroxylation experiments using mm-sized cuboids cut from six different crystals of San Carlos olivine with a range of trace-element concentrations. The cuboids were pre-annealed and then hydroxylated under identical conditions, ensuring that variation in the amounts of H incorporated depended only on the compositional variables. The pre-anneal was at 1400 °C, atmospheric pressure and an oxygen fugacity equivalent to Δlog FMQ?+?1, with the subsequent hydroxylation at 800 °C and 1.5 GPa, for 3 days. Hydrogen was incorporated into all six crystals by the four main substitution mechanisms [Si], [Mg], [Ti] and [triv], with homogeneous H contents in the cores of the crystals, indicating H diffusion rates faster than 10^??11 m²/s. Total H as H₂O in the homogeneous cores calculated by summing all the infrared absorbance bands ranges from 13 to 27 wt. ppm. The total H₂O in the six pre-annealed crystals is poorly correlated with any measured compositional variable. However, when the H₂O associated with individual infrared bands is compared, clear trends emerge. The intensity of absorption bands at 3572 and 3525 cm^??1 are strongly correlated with Ti concentrations, whose range in the six crystals exceeds an order of magnitude. Bands between 3400 and 3300 cm^??1, correlate negatively with Na⁺, but are positively correlated with the difference between molar Cr³⁺ and Na⁺. This highlights a previously unrecognised role for Na in suppressing H incorporation in natural olivines. The results confirm the important role that the trace constituents of olivine play in H incorporation. Two of these trace elements, Na and Ti, tend to be similarly enriched or depleted by partial melting or metasomatism of the mantle, but have opposite effects on H incorporation, with Ti enhancing it but Na suppressing it. Models estimating the effect of H in olivine on mantle rheology must, therefore, consider carefully the availability of these trace elements.  相似文献   

Quantifying lateral root reinforcement in steep slopes – from a bundle of roots to tree stands     

M. Schwarz  P. Lehmann  D. Or 《地球表面变化过程与地形》2010,35(3):354-367

A review of present modelling approaches for root reinforcement in vegetated steep hillslopes reveals critical gaps in consideration of plant–soil interactions at various scales of interest for shallow landslide prediction. A new framework is proposed for systematic quantification of root reinforcement at scales ranging from single root to tree root system, to a stand of trees. In addition to standard basal reinforcement considered in most approaches, the critical role of roots in stabilizing slopes through lateral reinforcement is highlighted. Primary geometrical and mechanical properties of root systems and their function in stabilizing the soil mass are reviewed. Stress–strain relationships are considered for a bundle of roots using the formalism of the fiber bundle model (FBM) that offers a natural means for upscaling mechanical behavior of root systems. An extension of the FBM is proposed, considering key root and soil parameters such as root diameter distribution, tortuosity, soil type, soil moisture and friction between soil and root surface. The spatial distribution of root mechanical reinforcement around a single tree is computed from root diameter and density distributions based on easy to measure properties. The distribution of root reinforcement for a stand of trees was obtained from spatial and mechanical superposition of individual tree values with regard to their positions on a hillslope. Potential applications of the proposed approach are illustrated in a numerical experiment of spatial strength distribution in a hypothetical slope with 1000 trees randomly distributed. The analyses result in spatial distribution of weak and strong zones within the soil where landslide triggering is expected in large and continuous zones with low reinforcement values. Mapping such zones would enhance the quality of landslide susceptibility maps and optimization of silvicultural measures in protection forests. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Directional hydrostratigraphic units simulation using MCP algorithm     

N.?BenoitEmail author  D.?Marcotte  A.?Boucher  D.?D’Or  A.?Bajc  H.?Rezaee 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(5):1435-1455

Understanding the geological uncertainty of hydrostratigraphic models is important for risk assessment in hydrogeology. An important feature of sedimentary deposits is the directional ordering of hydrostratigraphic units (HSU). Geostatistical simulation methods propose efficient algorithm for assessing HSU uncertainty. Among different geostatistical methods to simulate categorical data, Bayesian maximum entropy method (BME) and its simplified version Markov-type categorical prediction (MCP) present interesting features. In particular, the zero-forcing property of BME and MCP can provide a valuable constrain on directional properties. We illustrate the ability of MCP to simulate vertically ordered units. A regional hydrostratigraphic system with 11 HSU and different abundances is used. The transitional deterministic model of this system presents lateral variations and vertical ordering. The set of 66 (11 × 12/2) bivariate probability functions is directly calculated on the deterministic model with fast Fourier transform. Despite the trends present in the deterministic model, MCP is unbiased for the HSU proportions in the non-conditional case. In the conditional cases, MCP proved robust to datasets over-representing some HSU. The inter-realizations variability is shown to closely follow the amount and quality of data provided. Our results with different conditioning datasets show that MCP replicates adequately the directional units arrangement. Thus, MCP appears to be a practical method for generating stochastic models in a 3D hydrostratigraphic context.  相似文献