Diel cycles of arsenic speciation due to photooxidation in acid mine drainage from the Iberian Pyrite Belt (Sw Spain)

Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems.     

Inverse modeling of multicomponent reactive transport through single and dual porosity media

Compacted bentonite is foreseen as buffer material for high-level radioactive waste in deep geological repositories because it provides hydraulic isolation, chemical stability, and radionuclide sorption. A wide range of laboratory tests were performed within the framework of FEBEX (Full-scale Engineered Barrier EXperiment) project to characterize buffer properties and develop numerical models for FEBEX bentonite. Here we present inverse single and dual-continuum multicomponent reactive transport models of a long-term permeation test performed on a 2.5 cm long sample of FEBEX bentonite. Initial saline bentonite porewater was flushed with 5.5 pore volumes of fresh granitic water. Water flux and chemical composition of effluent waters were monitored during almost 4 years. The model accounts for solute advection and diffusion and geochemical reactions such as aqueous complexation, acid-base, cation exchange, protonation/deprotonation by surface complexation and dissolution/precipitation of calcite, chalcedony and gypsum. All of these processes are assumed at local equilibrium. Similar to previous studies of bentonite porewater chemistry on batch systems which attest the relevance of protonation/deprotonation on buffering pH, our results confirm that protonation/deprotonation is a key process in maintaining a stable pH under dynamic transport conditions. Breakthrough curves of reactive species are more sensitive to initial porewater concentration than to effective diffusion coefficient. Optimum estimates of initial porewater chemistry of saturated compacted FEBEX bentonite are obtained by solving the inverse problem of multicomponent reactive transport. While the single-continuum model reproduces the trends of measured data for most chemical species, it fails to match properly the long tails of most breakthrough curves. Such limitation is overcome by resorting to a dual-continuum reactive transport model.     

Multiscale analysis of heavy metal contents in Spanish agricultural topsoils

This study characterized and mapped the spatial variability patterns of seven topsoil heavy metals (Cr, Ni, Pb, Cu, Zn, Hg and Cd) within the Ebro river basin (9.3 million ha) by Multivariate Factorial Kriging. The variograms and cross-variograms of heavy metal concentrations showed the presence of multiscale variation that was modeled using three variogram models with ranges of 20km (short-range), 100km (medium-range) and 225km (long-range). Our results indicate that the heavy metal concentration is influenced by bedrock composition and dynamics at all the spatial scales, while human activities have a notorious effect only at the short- and medium-range scale of variation. Sources of Cu, Pb and Zn (and secondary Cd) are associated with agricultural practices (at the short-range scale of variation), whereas Hg variation at the short- and medium-range scale of variation is related to atmospheric deposition.     

Sustainability: A Study of the Level of Ecological Behavior of Postgraduate Students in Brazil

The decline in the supply of natural resources is a cause for concern, especially given continued worldwide population growth. New habits and attitudes toward resource use are slowly being introduced into the everyday lives of persons residing in a number of countries. The term “ecological behavior” refers to acting in favor of the environment, whether these actions are voluntarily or not, or learned or not (Pato & Tamayo, 2006 ). The general objective of this study is to identify the environmental behavior—one of several terms used interchangeably with ecological behavior—of graduate students from a Brazilian federal institution of higher education. We chose this particular group because many of them already act, or will act, as professors. Thus, by virtue of their positions, they will function as opinion leaders who will influence the education of future professionals, establishing a chain through which shared values can gradually change the environmental behavior of society.     

An Assessment of Oil Pollution in the Coastal Zone of Patagonia,Argentina

The Patagonian coast is considered a relatively pristine environment. However, studies conducted along coastal Patagonia have showed hydrocarbon pollution mostly concentrated at ports that have fishing, oil loading, general merchant, and/or tourist activities. A high value of total aliphatic hydrocarbons (TAH) was found at the Rawson fishing port (741 μg/g dw). In other ports with and without petroleum-related activities, hydrocarbon values were approximately 100 μg/g dw. The highest values for TAH and total aromatic hydrocarbons (TArH) were found in Faro Aristizábal, north of San Jorge gulf (1304 and 737 μg/g dw, respectively). This is very likely the result of petroleum-related activities at the Comodoro Rivadavia, Caleta Cordova, and Caleta Olivia ports located within this gulf. In other coastal areas away from potential anthropogenic sources, hydrocarbon values were less than 2 and 3 μg/g dw for TAH and TArH, respectively. This review of published and unpublished information suggests that ports are important oil pollution sources in the Patagonian coast. More detailed studies are needed to evaluate the area affected by port activities, to understand the mechanisms of hydrocarbon distribution in surrounding environments, and to assess bioaccumulation in marine organisms. Despite that some regulations exist to control oil pollution derived from port and docked vessel activities, new and stricter management guidelines should be implemented.     

Effects of the organophosphate insecticide azinphos-methyl on the reproduction and cholinesterase activity of Biomphalaria glabrata

Azinphos-methyl is an organophosphate insecticide used for pest control on a number of food crops in many parts of the world. The snail Biomphalaria glabrata is a freshwater gastropod widely distributed in South America, Central America and Africa. The aim of the present work was to investigate whether azinphos-methyl causes alterations in the reproduction of B. glabrata. To this end, gastropod pigmented specimens were exposed to various concentrations of the insecticide (0.021, 0.5, 2.5, and 5 mg L⁻¹) for either 2 or 14 d. Along 14 d, several reproduction parameters and cholinesterase (ChE) activity were evaluated. In each group, the number of egg masses, the number of eggs per mass, the number of hatchings, the time to hatching, and the survival of the offspring after one month of treatment was evaluated. The results showed that, depending on the concentration and time of exposure, azinphos-methyl induced alterations in the reproduction of B. glabrata. These alterations were mainly represented by a decrease in the number of egg masses, and, in some cases, by a lower number or even the total absence of hatchings. Thus, the gastropods exposed to 2.5 and 5 mg L⁻¹ of azinphos-methyl for 14 d showed ChE inhibitions higher than 35% along time and completely lost their ability to reproduce. On the other hand, exposure to high acute concentrations or exposure to low concentrations for 14 d resulted in ChE inhibition equal to or lower than 35% between 7 and 14 d of treatment and similar alterations in reproduction. These were represented by a decrease in the number of egg masses. At low pestice levels, the number of egg masses and the number of offspring resulted to be more sensitive biomarkers than ChE inhibition. It is concluded that the insecticide azinphos-methyl can cause a decline in the reproductive performance of B. glabrata.     

Genetic Structure of a Mimosoid Tree Deprived of Its Seed Disperser, the Spider Monkey

Abstract: To assess the genetic consequences for a Neotropical tree of the loss of its main seed disperser, we compared the genetic structure of Inga ingoides in a site where the spider monkey (Ateles paniscus) was abundant and a site where it had been eliminated by subsistence hunting. Gene flow should be reduced in the site where the spider monkey is absent, and there should be a corresponding subpopulation differentiation of seedlings within the spatial range of the movements of these primates in the absence of between-site differences in allelic frequencies. At the microhabitat (  family) scale, seedlings growing under parent plants should be genetically more related in the absence of the spider monkey than in its presence. Subpopulation differentiation was smaller where the spider monkey was present (  four loci, F_ST = 0.011) than where it was absent (  four loci, F_ST = 0.053) for the first year of study, but not for the second year (three loci, F_ST = 0.005 vs. 0.003). The number of alleles in common among seedlings growing under parent plants was smaller in the presence of the spider monkey than in its absence, showing family genetic structure in the first generation for both years of study ( Mann-Whitney, z = −2.17, p = 0.03 and z = −2.72, p = 0.006 for 1996 and 1997, respectively). This family genetic structure in the first generation should accelerate the development of population genetic structure. Development of genetic structure might result in demographic changes, one of which would be a fitness reduction if the species were self-incompatible, as suggested for Inga by available evidence. Large birds and mammals are the main targets of subsistence hunting in the Neotropics. Extinction of seed-dispersing frugivores may result in pronounced changes in the demographic and genetic structure of tree species in Neotropical forests.     

火地岛森林管理：是对环境的又一个威胁 还是可持续发展的一个机会?

为这片世界最南端的森林提出的一个主要森林管理和家具木材生产方案的可能影响,已经引起广泛关注.对这些原始森林的未来所给予的注意,突出说明了环境保护/生物多样性保护与经济效益之间的冲突.火地岛的公共当局和居民处在一个能指定他们合意的生活方式与环境质量的地位,而且能参与旨在以适合于其社会、经济和生态的条件和期望的方式确保可持续性的决策.