Seasonal variations in nickel and vanadium in Mont Blanc snow and ice dated from the 1960s and 1990s

Ni and V have been determined in snow and ice collected at a high altitude location (Col du D?me) near the summit of Mont Blanc on the French-Italian border; dated from the 1960s and 1990s. Ni and V were simultaneously determined by inductively coupled plasma sector field mass spectrometry. Measured concentrations range from 6 to 700 pg g(-1) and 4 to 1,100 pg g(-1) for Ni and V, respectively. The results show pronounced seasonal variations in the concentrations of both metals, with high concentration values in summer layers and much lower values for winter layers. These seasonal variations are linked especially with the existence of inversion layers during winter months. Ni and V concentrations in excess of the contributions from rock and soil dust (Ni(excess), V(excess)) appear to be mainly associated with anthropogenic inputs, with pronounced seasonal variations. Large variations in the V(excess)/Ni(excess) ratio are observed, with a higher ratio in summer than in winter. This shows differences in anthropogenic inputs at Col du D?me during the different parts of the year. The above ratio was compared with the corresponding ratios for oil combustion from stationary sources and the exhaust from gasoline and diesel engines. It appears that Ni and V concentrations at Col du D?me are probably the result of changing combinations of contributions from oil combustion for power generation, industrial and residential uses, on one side, and automobile and truck traffic, on the other side, with possibly a significant contribution from Ni smelters in Russia during winter months.     

Influence of the geomembrane on time-lapse ERT measurements for leachate injection monitoring

Leachate recirculation is a key process in the operation of municipal waste landfills as bioreactors. To quantify the water content and to evaluate the leachate injection system, in situ methods are required to obtain spatially distributed information, usually electrical resistivity tomography (ERT). However, this method can present false variations in the observations due to several parameters. This study investigates the impact of the geomembrane on ERT measurements. Indeed, the geomembrane tends to be ignored in the inversion process in most previously conducted studies. The presence of the geomembrane can change the boundary conditions of the inversion models, which have classically infinite boundary conditions. Using a numerical modelling approach, the authors demonstrate that a minimum distance is required between the electrode line and the geomembrane to satisfy the good conditions of use of the classical inversion tools. This distance is a function of the electrode line length (i.e. of the unit electrode spacing) used, the array type and the orientation of the electrode line. Moreover, this study shows that if this criterion on the minimum distance is not satisfied, it is possible to significantly improve the inversion process by introducing the complex geometry and the geomembrane location into the inversion tools. These results are finally validated on a field data set gathered on a small municipal solid waste landfill cell where this minimum distance criterion cannot be satisfied.     

A spatiotemporal model for predicting grain aphid population dynamics and optimizing insecticide sprays at the scale of continental France

We expose here a detailed spatially explicit model of aphid population dynamics at the scale of a whole country (Metropolitan France). It is based on convection–diffusion-reaction equations, driven by abiotic and biotic factors. The target species is the grain aphid, Sitobion avenae F., considering both its winged and apterous morphs. In this preliminary work, simulations for year 2004 (an outbreak case) produced realistic aphid densities, and showed that both spatial and temporal S. avenae population dynamics can be represented as an irregular wave of population peak densities from southwest to northeast of the country, driven by gradients or differences in temperature, wheat phenology, and wheat surfaces. This wave pattern fits well to our knowledge of S. avenae phenology. The effects of three insecticide spray regimes were simulated in five different sites and showed that insecticide sprays were ineffective in terms of yield increase after wheat flowering. After suitable validation, which will require some further years of observations, the model will be used to forecast aphid densities in real time at any date or growth stage of the crop anywhere in the country. It will be the backbone of a decision support system, forecasting yield losses at the level of a field. The model intends then to complete the punctual forecasting provided by older models by a comprehensive spatial view on a large area and leads to the diminution of insecticide sprayings in wheat crops.     

Is the bone tissue of ring-billed gulls breeding in a pollution hotspot in the St. Lawrence River,Canada, impacted by halogenated flame retardant exposure?

Bone metabolism is a tightly regulated process that controls bone remodeling and repair in addition to maintaining circulating calcium and phosphate levels. It has been shown that certain organohalogen contaminants may adversely impact bone tissue metabolism and structure in wildlife species. However, exceedingly few studies have addressed the bone-related effects of organohalogen exposure in birds. The objective of the present study was to investigate the associations between markers of bone metabolism and structural integrity, and concentrations of established and current-use halogenated flame retardants (FRs) in ring-billed gulls (Larus delawarensis) nesting in a known FR hotspot area in the St. Lawrence River (Montreal, Canada). Bone metabolism was assessed using plasma calcium and inorganic phosphate levels, and alkaline phophatase activity, while bone (tarsus; trabecular and cortical sections) structure quality was examined using the percentage of bone tissue comprised in the total bone volume (Bv/Tv) and bone mineral density (BMD). Bv/Tv and BMD of the tarsus tended (not significant) to be positively associated with circulating calcium levels in male ring-billed gulls. Moreover, concentrations of FRs in male bird liver (brominated diphenyl ether (BDE)-154, -183, -201, and -209) and plasma (BDE-209) were negatively correlated with trabecular and cortical BMD of the tarsus. These correlative associations may suggest light demineralization of bone tissue associated with FR exposure in male ring-billed gulls. Present findings provide some evidence that bone (tarsus) metabolism and mineral composition may be impacted in high FR-exposed (mainly to PBDEs) ring-billed gulls breeding in the highly urbanized Montreal region.     

A RISK-BASED MODEL FOR DROUGHT CONTINGENCY PLANNING1

ABSTRACT: A risk-based model is presented for determining action levels in real-time operation of public water supplies under drought conditions. The model, applicable to surface water supplies, is built around the almost universally adopted structure for drought management, a sequence of increasingly stringent measures to reduce demand. Action levels are determined by finding minimum storage levels that will satisfy a prescribed set of probability constraints over the remainder of a drawdown-refill cycle. Results are presented for the City of Raleigh, NC.     

Neocembrene A, a major component of the trail-following pheromone in the genus Prorhinotermes (Insecta, Isoptera, Rhinotermitidae)

Summary. The diterpene neocembrene A or (1E,5E,9E,12R)-1,5,9-trimethyl-12-(1-methylethenyl)-1,5,9-cyclotetradecatriene, known as the trail-following pheromone of the advanced Termitidae Nasutitermitinae Nasutitermes exitiosus and Trinervitermes bettonianus, has been identified after SPME-GC/MS as the major component of the trail-following pheromone of the Rhinotermitidae Prorhinotermitinae, Prorhinotermes canalifrons and P. simplex. In all the other Rhinotermitidae studied until now, the major component of their trail pheromones is dodecatrienol ((3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol). This biochemical data further add to the anatomical and molecular characteristics that give a special status to the taxon Prorhinotermes among Rhinotermitidae. In Prorhinotermes canalifrons and P. simplex, neocembrene A was the only secretory compound specific to the sternal gland surface that could be detected after SPME. It elicited orientation as well as recruitment behavioral effects. However, the comparison of the respective biological activities triggered by neocembrene A and by sternal gland secretion suggests that minor components of the latter are acting in synergy with neocembrene A.     

Offspring sex ratio in relation to parental structural size and body condition in the long-lived wandering albatross (<Emphasis Type="Italic">Diomedea exulans</Emphasis>)

Sex ratio theory is one of the most controversial topics in evolutionary ecology. Many deviations from an equal production of males and females are reported in the literature, but few patterns appear to hold across species or populations. There is clearly a need to identify fitness effects of sex ratio variation. We studied this aspect in a population of a long-lived seabird, the wandering albatross (Diomedea exulans), using molecular sex-identification techniques. We report that parental traits affect both (1) fledgling traits in a sex-dependent way and (2) chick sex: Sons are overproduced when likely to be large at fledging and, to a lesser extent, daughters are overproduced when likely to be in good body condition at fledging. Because for the same population, a previous study reported that post-fledging survival was positively affected by size in males and by body condition in females, our results suggest that wandering albatrosses manipulate offspring sex to increase post-fledging survival.     

Trophic relationships in the recently impounded Bagré reservoir in Burkina Faso

The trophic dynamics of Bagré reservoir which has been recently impounded in Burkina Faso was based on the data collected during 1997–1998 period using the Ecopath model and software. Total fish biomass is 22.63 t km⁻² and mainly represents trophic levels (TLs) 2 and 3. The trophic food chain is relatively long and the overall transfer efficiency is quite low. Grazing foodweb based on primary producers is prominent in the reservoir ecosystem and detritus plays a less significant role. Seasonal and long-term variations in water quality have significant influences on the lower TLs clearly showing a bottom-up functioning of the ecosystem. Environmental degradations, such as siltation occurring in the lake, suggest possible risks in limiting ecosystem productivity.     

A METHODOLOGY FOR SELECTING AMONG WATER QUALITY ALTERNATIVES1

While reservoirs are constructed to regulate stream flows for several beneficial purposes including flood control, water supply, hydroelectric power, irrigation and low flow augmentation and to enhance water based recreation, they create problems of water quality that offer a new dimension to the task of efficient operation. Among other potential deleterious effects, thermal stratification in reservoirs inhibits mixing and causes a deterioration of dissolved oxygen levels in lower layers. Several investigators have examined the thermal properties of reservoirs and resultant effects upon dissolved oxygen and have suggested alternative schemes for alleviating detrimental effects (1,2,3,4,5). The objective of this paper is to outline a methodology for evaluating some of these alternatives in a river-reservoir system where downstream water quality control is one of several purposes to be served by the reservoir.