Heavy metals partioning in three French forest soils by sequential extraction procedure

To know the concentration of heavy metal associated to chemical compounds is important to evaluate the environmental risks on soils, particularly regarding ion bioavailability. The relative mobility and strength of binding of heavy metals to the soil components can be studied using a sequential extraction procedure which provides a meaningful comparison between different soil profiles. The heavy metals partitioning bas been identified in three different french forest soils : one cambic podzol, one calcaric cambisol and one mollic andosol, using a new sequential extraction method. Results show that metal fractionation is metal and site specific. The water leaching phase does not contain any metals. The proportion of heavy metal leached in the exchangeable and the acid — soplhuabslee is significant for Cd. The residual phase is important for Cr, Pb, and to a lesser extend for Ni. The organic matter fraction is dominant for Zn and Cu. Thus, the considered heavy metals are mainly bounded to iron oxides, to the organic matter and to the mineral residue. The order of heavy metals availability in the three soils would be : Zn>Cd>Cu>Pb>NiL&egatd;C r.i sotopes in some extracts of the extraction procedure corroborate the anthropogenic inputs for two soils. These both infomations allow to trace the origin, the mobility and the distribution of Pb in the soil

Practical Issues Regarding the Use of Dielectric Measurements to Diagnose the Service Health of MV Cables

Presented at Jicable '07.During the last decade, Very Low Frequency (VLF) testing for extruded distribution cables has gained interest among the North American utilities. The increasing interest is evidenced by recent research publications and discussions inside the expert community in which standards are being proposed and continuously discussed. While there is a general consensus as to the meaning of insulation dielectric properties, many open issues still remain for discussion in order to produce a more accurate evaluation. Consequently, this paper will discuss a number of the practical issues that arise when making these measurements at VLF on field aged and non-aged cables, particularly Tan δ measurements. The discussion is based on data from laboratory experiments and field testing.The work reported here was supported by a large number of utilities in North America and the U.S. Department of Energy under award number DE-FC02-04CH11237

A Drop of Active Matter

We study theoretically the hydrodynamics of a fluid drop containing oriented filaments endowed with active contractile or extensile stresses and placed on a solid surface. The active stresses alter qualitatively the wetting properties of the drop, leading to new spreading laws and novel static drop shapes. Candidate systems for testing our predictions include cytoskeletal extracts with motors and ATP, suspensions of bacteria or pulsatile cells, or fluids laden with artificial self-propelled colloids.Comment: submitted to J Fluid Mec

Critical loads for lead in France: First results on forest soils

Within the framework of the United Nation Convention on Long Range Transboundary Air Pollution, France is part of the Working Group on Effect which aims at evaluating the impact of atmospheric deposition on ecosystems by calculating critical loads. The critical loads are the highest deposition of compounds that will not cause chemical changes in soil leading to long-term harmful effects on ecosystem structure and function. A guidance manual for calculation of critical loads for heavy metals (lead and cadmium) has been proposed by the Coordination Center for Effects (executive body of the WGE). French National Focal Center (CNRS and ADEME) aims in this study at evaluating the accuracy of the european methodology for calculation of critical loads for french forest soils. It appears that critical load approach is adapted for France but need to be calibrated at least for calculation of weathering fluxes and determination of critical limits. Stand-still on the contrary is not adequate because of inherent contradictions in the method and too much uncertainties in the transfer functions

Hypercompact stellar clusters: morphological renditions and spectro-photometric models

Numerical relativity predicts that the coalescence of a black hole-binary causes the newly formed black hole to recoil, and evidence for such recoils has been found in the gravitational waves observed during the merger of stellar-mass black holes. Recoiling (super)massive black holes are expected to reside in hypercompact stellar clusters (HCSCs). Simulations of galaxy assembly predict that hundreds of HCSCs should be present in the halo of a Milky Way-type galaxy, and a fraction of those around the Milky Way should have magnitudes within the sensitivity limit of existing surveys. However, recoiling black holes and their HCSCs are still waiting to be securely identified. With the goal of enabling searches through recent and forthcoming databases, we improve over existing literature to produce realistic renditions of HCSCs bound to black holes with a mass of 10$^{5}$ M$_{\odot}$. Including the effects of a population of blue stragglers, we simulate their appearance in Pan-STARRS and in forthcoming $Euclid$ images. We also derive broad-band spectra and the corresponding multi-wavelength colours, finding that the great majority of the simulated HCSCs fall on the colour-colour loci defined by stars and galaxies, with their spectra resembling those of giant K-type stars. We discuss the clusters properties, search strategies, and possible interlopers.Comment: Accepted for publication on MNRAS, 17 pages, 7 figure

Microstructural modifications in tungsten induced by high flux plasma exposure : TEM examination

We have performed microstructural characterization using transmission electron microscopy (TEM) techniques to reveal nanometric features in the sub-surface region of tungsten samples exposed to high flux, low energy deuterium plasma. TEM examination revealed formation of a dense dislocation network and dislocation tangles, overall resulting in a strong increase in the dislocation density by at least one order of magnitude as compared to the initial one. Plasma-induced dislocation microstructure vanishes beyond a depth of about 10 mu m from the top of the exposed surface where the dislocation density and its morphology becomes comparable to the reference microstructure. Interstitial edge dislocation loops with Burgers vector a(0)/2 and a(0) were regularly observed within 6 mu m of the sub-surface region of the exposed samples, but absent in the reference material. The presence of these loops points to a co-existence of nanometric D bubbles, growing by loop punching mechanism, and sub-micron deuterium flakes, resulting in the formation of surface blisters, also observed here by scanning electron microscopy

Effects of wind driven rainfalls on soil loss from a Douro vineyard, Portugal

In permanent row crops, rainfall interception by canopies in rows varies according to wind direction and this may affect raindrop impact and erosion in the inter-row area. The paper aims at discussing the effects of wind direction during rainfalls on soil loss from vineyard plots with different slope aspect in the Douro Region, Portugal. Long term continuous rainfall records, daily wind direction, and soil loss from 5 plots (32m long x 5n wide), in a 45% slope row‐planted vineyard, with slope aspect from NW to SW, were explored separating events only with water loss (NER, 67 non‐erosive events) from the others (ERO, 100 erosive events), and considering for each event wind direction at peak rainfall intensity. Calm atmosphere prevailed but with lower frequency in ERO (65%) than in NER (72%). Most frequent winds were NW (20%) and S (11%) in ERRO, and SE (12%) and NW (7%) in NER. Wind direction affected the differences between plots in event soil loss (expressed by the CV of the 5 plots soil loss in each event), with a CV 90% for NW winds, 37% for S, and 33% for Calm. NW winds blow parallel to vine rows in some plots and almost perpendicular in the others and this effect was most evident during the larger erosion events when lowest to highest plot soil loss ratio reached 1:50. These results may contribute to better tune the application of conservation measures in Douro vineyards considering plot location and dominant wind direction.info:eu-repo/semantics/publishedVersio

Estimating erosion control performance of soil management practices in Douro viticulture

Conventional soil management (sm) in Douro viticulture, Portugal, comprise several weed control tillage operations along the crop cycle. Alternative sm practices reduce or exclude tillage, keeping ground cover for large part of the wetter seasons. Aiming at comparing the relative performance in erosion control of alternative sm practices, this study used long term records from a Douro vineyard as vine and ground vegetation evolution, crop management operations and detailed rainfall data. The USLE C factor was calculated combining vine row cover and inter-row ground cover effects in the typical vine cycle. With rainfall erosivity temporal distribution, erosion control by ground vegetation management options, representing different sm practices, was assessed for conventional and alternative (imposing different ground vegetation density, removal date and residues level after weed control). Results compare relative soil protection performance of alternative sm practices with conventional sm. Leaving residues over ground after weed control works better (54% increase in erosion control for 80% residue cover), than delaying weed control date (37% increase for a delay to mid-July), while increasing sown ground vegetation density is not so effective (17% increase for 80% cover). The methodological approach and results of this study are expected to contribute to better adjust sm practices for erosion control in Douro viticulture.info:eu-repo/semantics/publishedVersio