Contribution of SHRIMP U–Pb zircon geochronology to unravelling the evolution of Brazilian Neoproterozoic fold belts

The South-American continent is constituted of three major geologic–geotectonic entities: the homonym platform (consolidated at the end of the Cambrian), the Andean chain (essentially Meso-Cenozoic) and the Patagonian terrains, affected by tectonism and magmatism through almost all of the Phanerozoic. The platform is constituted by a series of cratonic nuclei (pre-Tonian, fragments of the Rodinia fission) surrounded by a complex fabric of Neoproterozoic structural provinces.     

Main Species Characteristics of Phytoplankton Spring Blooms in NE Atlantic and Arctic Waters (68–80° N)

A compilation of phytoplankton species abundance data from the spring bloom along the northern Norwegian coast and in the Barents Sea shows that the quantitatively most important species are the prymnesiophyte Phaeocystis pouchetii and the common cold water to temperate diatoms Chaetoceros socialis, Skeletonema costatum sensu lato, Fragilariopsis oceanica, Thalassiosira spp., Chaetoceros furcellatus, Chaetoceros compressus, Chaetoceros debilis and Bacterosira bathyomphala. The relative abundance of diatoms and Phaeocystis varied highly and apparently stochastically between years. P. pouchetii occurred during all stages of the spring bloom and sometimes completely dominated the phytoplankton community. Along the Norwegian coast, the importance of P. pouchetii increased northwards. The species composition in coastal fjords at 70° N is surprisingly similar to that of shelf waters in the Barents Sea (up to 80° N). An exception is S. costatum sensu lato which was seldom observed in Arctic waters. Small flagellates (<10 μm) other than dinoflagellates and P. pouchetii are also important among the Barents Sea spring phytoplankton. Associations of species seem rigid over time and are dominated by C. socialis and P. pouchetii in northern waters. Biogeographical categories of spring bloom species in relation to environmental conditions are discussed.     

Mineralogical and geochemical spatial analyses of a waste-rock dump at the Libiola Fe–Cu sulphide mine (Eastern Liguria,Italy)

In this work, we investigated a 3 ha sulphide-bearing waste-rock dump (Libiola Mine, Italy) using mineralogical, geochemical, and geostatistical analyses. The dumped materials were highly heterogeneous in grain size and lithology and varied both laterally and vertically. Other than the host rock of the ore, basalts and serpentinites, the dumped materials contained high amounts of low-grade chalcopyrite- and pyrite-rich mineralisations. Due to these characteristics and to the absence of minerals able to neutralise acidity, this waste-rock dump can be classified as an acid mine drainage (AMD) producer. The study confirms that AMD is still active and, in the best scenario, can persist for up to 6.17 × 10³ years. The consequences of this process are of serious environmental concern as it involves strong acidification of the circulating waters, the release of potentially toxic metals into the soil, streams and rivers and the precipitation of huge quantities of secondary Fe-oxides and Fe-oxyhydroxides.     

Micro-XCT chondrule classification for subsequent isotope analysis

Chondrules are microscopic, recrystallized melt droplets found in chondritic meteorites. High-resolution isotope analyses of minor elements require large enough element quantities which are obtained by dissolving entire chondrules. This work emphasizes the importance of X-ray computed tomography (XCT) to detect features that can significantly affect the bulk chondrule isotope composition. It thereby expands on other works by looking into chondrules from a wide range of chondrites including CR, CV, CB, CM, L, and EL samples before turning toward complex and time-consuming chemical processing. The features considered are metal and igneous rims, compound chondrules, matrix remnants, and metal contents. In addition to the identification of these features, computed tomography prevents the inclusion of non-chondrule samples (pure matrix or metal) as well as samples where two different chondrule fragments with potentially different isotope compositions are held together by matrix. Matrix surrounding chondrules is also easily detected and the affected chondrules can be omitted or reprocessed. The results strongly encourage to perform XCT before dissolution of chondrules for isotope analysis as a non-invasive method.     

Species richness,diversity and density of understory vegetation along disturbance gradients in the Himalayan conifer forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.     

Accounting for uncertainties and time preference in economic analysis of tackling climate change through forestry and selected policy implications for Scotland and Ukraine

The paper discusses the development of economic techniques for dealing with uncertainties in economic analysis of planting trees to mitigate climatic change. In consideration of uncertainty, time preference and intergenerational equity, the traditional cost-benefit analysis framework is challenged with regard to the discounting/non-discounting of carbon uptake benefits, and because it usually uses a constant and positive discount rate. We investigate the influence of various discounting protocols on the outputs of economic analysis. The idea of using the declining discount rate is also considered. Several numerical examples dealing with the analysis of afforestation for carbon sequestration in Scotland and Ukraine are provided. We show that the choice of discounting protocols have a considerable influence on the results of economic analysis, and therefore, on the decision-making processes related to climate change mitigation strategies. The paper concludes with some innovative insights on accounting for uncertainties and time preference in tackling climate change through forestry, several climate policy implications of dealing with uncertainties, and a brief discussion of what the use of different discounting protocols might imply for decision making.     

Enhancing the relevance of Shared Socioeconomic Pathways for climate change impacts,adaptation and vulnerability research

This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance.     

A numerical approach to estimate shaft friction of bored piles in sands

A new approach to estimate shaft capacity of bored piles in sandy soils, based on numerical analysis, is presented. The topic is relevant as current design methods often largely underestimate the shaft capacity of piles in sands, thus resulting in an over-conservative design. The proposed approach is based on explicitly modelling the thin cylinder of soil surrounding the pile, where strain localization concentrates (shear band), and on the fundamental mechanic behaviour of sandy soils (e.g. dilatancy, softening). This approach is both simple and easy to apply. Results of a broad parametric study involving axially loaded single piles embedded in different sandy soils are presented, highlighting that relative density and grain size distribution mainly affect the shaft capacity. The capability of the procedure to predict shaft friction is checked against data from a well-documented full-scale axial load test on instrumented pile. Some suggestions for calibration and application of the method are also reported.     

Evaluating locally available organic substrates for vertical flow passive treatment cells at Cerro Rico de Potosí, Bolivia

Vertical flow cells (VFCs) are key components of passive acid mine drainage (AMD) treatment systems and require organic substrates that create anaerobic conditions and encourage bacterial sulfate reduction. In the high elevation desert of Potosí, Bolivia, the low productivity landscape limits the availability of sustainable and economical organic substrates. Locally available brewery waste, llama manure, and cow manure were evaluated as potential VFC substrates in a preliminary laboratory fed-batch study to assist in passive treatment system design. Two abandoned AMD discharges were collected from Cerro Rico de Potosí. Discharge A had an initial pH of 2.96, specific conductance of 3.31 mS/cm, and acidity of 1,350 mg/L as CaCO₃ equivalent. Discharge B had an initial pH of 3.85, specific conductance of 1.87 mS/cm, and acidity of 1,000 mg/L as CaCO₃ equivalent. Triplicate fed-batch reactors were set up in 1-L cubitainers with each potential substrate exposed to each AMD, yielding a total of 18 reactors exposed for 9 days and sampled two times for anions and dissolved metals. Cow manure reactors exhibited the greatest pH and alkalinity increases. Cd, Co, Fe, Mn, Ni, Pb, and Zn decreased in all reactors. SO₄ concentrations only decreased in brewery waste reactors. However, SO₄ reducing bacteria was higher for cow manure reactors. Results suggest that llama and cow manure are the more labile substrates, with llama manure being the most affordable. Brewery waste could be a suitable less-labile long-term substrate amendment. However, longer-term studies are needed to determine the optimum VFC substrate mixture in this unique circumstance.     

Luminescence and other spectroscopic properties of purple and green Cr-clinochlore

For the first time ever, the luminescence spectra of Cr³⁺ centers in two chlorite crystals are presented. Chromium ions occupy the strong crystal-field site M4 in the brucite sheet and the intermediate crystal-field site in the inner octahedral sheet for purple and green chlorite, respectively. We discuss the influence of an effective positive charge on the Cr³⁺ ion and an effective negative charge of ligands on the differences in the values of the Dq and B parameters. It is concluded that the presence of Fe²⁺ ions and other point defects, as well as concentration quenching, causes the very short luminescence lifetimes of chromium ions.