The impact of a disused mine on uranium transport in the River Fal, South West England

Unfiltered and filtered (0.45 and 0.2 microm) water samples and sediment samples (sieved to <180 microm and 180-1000 microm) were collected along an approximately 15 km transect of the River Fal, Cornwall, UK, to examine the impact of the disused South Terras uranium mine on the uranium concentrations of the river water and underlying sediments. The uranium concentration of the water samples fluctuated along the river, with the 0.45 microm filtered water showing the largest, seven-fold, difference between minimum (0.19 microg L(-1)) and maximum (1.34 microg L(-1)) concentrations. The historical uranium mine and spoil heaps were not a significant source of uranium to the river water, as water concentrations were low next to the site, but a highly elevated uranium concentration (1000 mg kg(-1)) was found in sediment below an outflow pipe from this mine. Operationally defined "colloidal" (0.2-0.45 microm) and "dissolved" (<0.2 microm) uranium were the predominant forms of the element in the river water (35 and 45% respectively). The uranium concentration in the dissolved phase showed a correlation coefficient of 0.83 (n= 9) with the total cation concentration, suggesting that the uranium concentration in this fraction is directly linked to weathering of rocks and minerals. The observation that weathering is the dominant mechanism delivering uranium to the river water explains the low uranium concentrations in the river water close to South Terras mine, despite the proximity of the spoil heaps, and the maximum uranium concentrations close to a china clay mining area.     

Indicators of physiological and immunological status of <Emphasis Type="Italic">Litopenaeus setiferus</Emphasis> wild populations (Crustacea,Penaeidae)

Constant environmental changes in oceanic and estuarine systems due to human activity in coastal zones require different tools and strategies for their study to be able to assess the health status of aquatic ecosystems. The Gulf of Mexico has a tremendous ecological importance because of its biological diversity. Baseline levels of blood metabolites and immune components were defined for wild tropical populations of Litopenaeus setiferus, an important shrimp species of the Gulf of Mexico. Osmotic pressure, oxy hemocyanin (OxyHc), glucose, proteins, cholesterol, lactate, and triacylglycerols (TAG) were used as indicators of physiological status; pro phenoloxydase (proPO) and phenoloxydase (PO) quantification of hemocytes, as well as respiratory burst, were used to assess the immunological status. Significant differences were observed in live weight of juveniles, males, and females of L. setiferus with mean values of 10.54, 35.05, and 40.33 g, respectively. A value of 460 mOsm/kg was recorded in the water where juveniles were sampled and 1,000 mOsm/kg in adult sampling zones. Consequently, the osmotic pressure of L. setiferus juveniles (718.02 mOsm/kg) was 22% lower than in adults (925 mOsm/kg); there were no differences between sexes. A significantly lower value in juvenile OxyHc was observed. This value was 24 and 16% lower than that observed in males and females, respectively. Hemolymph glucose, cholesterol, and triacylglycerol levels were not statistically different between shrimp stages, showing median values of 0.19, 0.32, and 0.39 mg/ml of glucose, cholesterol, and triacylglycerols, respectively. Hemocyanin was distributed normally in the juvenile–male population but not in females. A proportion between 52 to 81% of OxyHc of the total protein (OxyHc/Prot) was obtained for all stages. Digestive gland glycogen showed no normal distribution in juveniles and adults. Digestive gland glycogen was significantly higher in juveniles (median value of 2.64 mg/g) than in adults (median value of 1.58 mg/g). A higher value of lactate (0.11 mg/ml) was observed in juveniles than in males (0.09 mg/ml) and females (0.04 mg/ml). Granular cells (GC) corresponded to 36, 44, and 39% of the total hemocytes (TH) observed in juveniles, males, and females. ProPO showed no normal distribution in all stages. A high proPO activity was recorded in L. setiferus females that was 95% higher than in the juvenile–male group. Respiratory burst was divided into two groups, juveniles–males and females, and was distributed normally in both. Female respiratory burst values were 40 and 45% higher than those observed in the juvenile and male groups, respectively. There was an increment in OxyHc, proteins, PO, hemocytes, and respiratory burst with an increase in body weight. In contrast, the relationship of live weight to glucose, TAG, and proPO revealed no significant regressions. A significant decrease in cholesterol, glycogen, and lactate with an increase in body weight was also observed. We now have indicators of nutritional and immune status of juveniles and adults that can reveal changes in trophic relations and health at the population level. This will serve as a basis for using L. setiferus as environmental sentinels, as non-controversial and inexpensive models to evaluate the potential changes that human activities could exert on this important marine ecosystem.Communicated by P.W. Sammarco, Chauvin     

Procedures for estimation of modelling uncertainty in air quality assessment

The main objectives of this work focus, firstly, on a review of the current existent methodologies to estimate air quality modelling uncertainty, and, secondly, in the preparation of guidelines for modelling uncertainty estimation, which can be used by local and regional authorities responsible for air quality management. From the application exercise, it was concluded that it is possible to define a subset of statistical parameters able to reproduce the general uncertainties estimation. Concerning the quality indicators defined by EU directives, the results show that the legislated uncertainty estimation measures are ambiguous and inadequate in several aspects, mainly in what concerns the error measures for hourly and daily indicators based on the highest observed concentration. A relative error at the percentile correspondent to the allowed number of exceedances of the limit value was suggested and tested, showing that is a more robust and appropriate parameter for model performance evaluation.     

Biogenic cements and encapsulation of zinc

Metals can be stabilized into cement matrix by solidification/stabilization process. Rice hull is an agricultural residue containing about 10-20% (weight) of silica. It can be used to synthesize β-Ca₂SiO₄, an important component of Portland cement. Furthermore it is possible to prepare β-Ca₂SiO₄ doped with heavy metals. Here we describe the synthesis of β-Ca₂SiO₄ doped with zinc and the behavior of mortars prepared using this material. Products were analyzed by X-ray diffraction, differential thermal analysis and scanning electron microscopy coupled to energy-dispersive spectroscopy. The maximum amount of zinc that can be inserted into β-Ca₂SiO₄, without affecting the crystalline structure, is limited to 2% (molar basis). In comparison with conventional mortars, zinc-modified mortars show a similar behavior, regarding porosity, resistance to acidic attack and compressive strength. The synthesis of β-Ca₂SiO₄ doped with zinc presents a new possibility for safety enhancement in solidification/stabilization processes.     

Impacts of climate change on the distribution of species and communities in the Chilean Mediterranean ecosystem

The Mediterranean region of Chile is considered a biodiversity hot spot. An increase in temperature and decrease in precipitation, as projected for the end of this century by global circulation models, would likely change the distribution of the sclerophyllous thorny shrubland and woodland. In order to assess those potential impacts, the MAXENT algorithm was used to project potential changes in the distribution of the Mediterranean ecosystem. Ecological niche models were fitted and used to project the potential distribution of these forest ecosystems by the end of the century. Projections were made using data from the PRECIS model for the A2 and B2 climate change scenarios and two strategies of occupancy: free migration and non-migration. Distribution models of sclerophyllous, woodland and shrubland performed accurately representing current species’ distribution. When we assume non-migration responses under climate change scenarios, results reveal a decrease in the distribution area for all the species. The areas where the highest reduction in a suitable environment was found are located along the coastline, where higher temperature increases have been projected. For native ecosystems from the Andean Range region, such as communities dominated by thorny species, a stable habitat was found, associated with a higher adaptation capability to future climatic projections. Hence, in the future, buffer zones originated by “topo-climatic” conditions might play a key role in protecting Central Chile biodiversity.     

Multicriteria analysis applied to the sustainable agriculture problem

SUMMARY

The aim of this paper is to present an operational approach to compare the relative sustainability of existing farming systems. Sustainability rests on the assumption that an equilibrium must exist among three domains: social, economic and ecological. If we are to look for a solution to the problem, we must face a multi-dimensional approach. We propose that multicriteria analysis, a multi-dimensional method, is an appropriate methodology to study the issue. As sustainability cannot be measured directly, the way out is to use indicators. We have performed a thorough analysis of four farming systems existing in Guaíra, SP, Brazil to validate the methodology. Thirty indicators of sustainability (ten ecological, ten social, and ten economic) were defined and used to perform the analysis. The results of the multicriteria analysis proved useful because of its capability of reducing the dimensionality of the problem. From the three dimensions of sustainability, a final score was derived that can easily compare the relative sustainability of each farming system.     

Comparing modern and presettlement forest dynamics of a subboreal wilderness: does spruce budworm enhance fire risk?

Insect disturbance is often thought to increase fire risk through enhanced fuel loadings, particularly in coniferous forest ecosystems. Yet insect disturbances also affect successional pathways and landscape structure that interact with fire disturbances (and vice-versa) over longer time scales. We applied a landscape succession and disturbance model (LANDIS-II) to evaluate the relative strength of interactions between spruce budworm (Choristoneura fumiferana) outbreaks and fire disturbances in the Boundary Waters Canoe Area (BWCA) in northern Minnesota (USA). Disturbance interactions were evaluated for two different scenarios: presettlement forests and fire regimes vs. contemporary forests and fire regimes. Forest composition under the contemporary scenario trended toward mixtures of deciduous species (primarily Betula papyrifera and Populus spp.) and shade-tolerant conifers (Picea mariana, Abies balsamea, Thuja occidentalis), with disturbances dominated by a combination of budworm defoliation and high-severity fires. The presettlement scenario retained comparatively more "big pines" (i.e., Pinus strobus, P. resinosa) and tamarack (L. laricina), and experienced less budworm disturbance and a comparatively less-severe fire regime. Spruce budworm disturbance decreased area burned and fire severity under both scenarios when averaged across the entire 300-year simulations. Contrary to past research, area burned and fire severity during outbreak decades were each similar to that observed in non-outbreak decades. Our analyses suggest budworm disturbances within forests of the BWCA have a comparatively weak effect on long-term forest composition due to a combination of characteristics. These include strict host specificity, fine-scaled patchiness created by defoliation damage, and advance regeneration of its primary host, balsam fir (A. balsamea) that allows its host to persist despite repeated disturbances. Understanding the nature of the three-way interaction between budworm, fire, and composition has important ramifications for both fire mitigation strategies and ecosystem restoration initiatives. We conclude that budworm disturbance can partially mitigate long-term future fire risk by periodically reducing live ladder fuel within the mixed forest types of the BWCA but will do little to reverse the compositional trends caused in part by reduced fire rotations.