Cu- and Zn-Soil Anomalies in the NE Border of the South Portuguese Zone (Iberian Variscides,Portugal) Identified by Multifractal and Geostatistical Analyses

Extensive Cu- and Zn-soil geochemical data in the Albernoa/Entradas–S. Domingos region (NE border of the Iberian Pyrite Belt, South Portuguese Zone) were examined to separate anomalies from background using the concentration–area fractal model. Distribution patterns of Cu and Zn concentrations in soil are primarily influenced by bedrock. The regional threshold values of Cu- and Zn-soil contents over metasedimentary sequences are 20–25 and 20–60 ppm, respectively, becoming 30–50 and 20–90 ppm, respectively, when metavolcanic rocks are present. The first-order threshold values for Cu are 80–90 ppm in soils over metasediments and 70–80 ppm in soils over sequences bearing metavolcanics. For Zn, the first-order threshold values are 40–80 and 90–100 ppm in soils over metasediments and metavolcanic rocks, respectively. Metasediments and metavolcanics comprising significant sulphide disseminations are outlined by Cu- and Zn-soil values above 100 and 300 ppm in soil, respectively. On the basis of these results, Alvares and Albernoa/Entradas areas emerge as the first priority targets for exploration. The observed non-coincidence of Cu- and Zn-soil anomalies in soil in the area could reflect difference in element dispersion during weathering, they mostly indicate distinct metal sources related to the original composition of different rock types or to chemical changes developed during Variscan deformation/re-crystallization path. The established regional baseline data can be used as reference for environmental studies.     

Predicting spectral features in galaxy spectra from broad-band photometry

We explore the prospects of predicting emission-line features present in galaxy spectra given broad-band photometry alone. There is a general consent that colours, and spectral features, most notably the 4000 Å break, can predict many properties of galaxies, including star formation rates and hence they could infer some of the line properties. We argue that these techniques have great prospects in helping us understand line emission in extragalactic objects and might speed up future galaxy redshift surveys if they are to target emission-line objects only. We use two independent methods, Artificial Neural Networks (based on the ANNz code) and Locally Weighted Regression (LWR), to retrieve correlations present in the colour N -dimensional space and to predict the equivalent widths present in the corresponding spectra. We also investigate how well it is possible to separate galaxies with and without lines from broad-band photometry only. We find, unsurprisingly, that recombination lines can be well predicted by galaxy colours. However, among collisional lines some can and some cannot be predicted well from galaxy colours alone, without any further redshift information. We also use our techniques to estimate how much information contained in spectral diagnostic diagrams can be recovered from broad-band photometry alone. We find that it is possible to classify active galactic nuclei and star formation objects relatively well using colours only. We suggest that this technique could be used to considerably improve redshift surveys such as the upcoming Fibre Multi Object Spectrograph (FMOS) survey and the planned Wide Field Multi Object Spectrograph (WFMOS) survey.     

Mechanics of thick-skinned Variscan overprinting of Cadomian basement (Iberian Variscides)

Remnants of the Cadomian basement can be found in the Iberian Variscides (IBVA) in several key sectors of its autochthonous units (composed of Neoproterozoic to Lower Palaeozoic metasedimentary sequences) and within the Continental Allochthonous Terrane (CAT). Comprehensive characterization of these critical exposures shows that the prevailing features are related to major geological events dated within the age range of 620–540 Ma. Indeed, near the Cambrian–Ordovician boundary, the IBVA Internal Zones experienced pervasive basement thinning and cover thickening, reflecting diffusive displacement of intracratonic rifting that continued until Lower Devonian times. In the thick-skinned Internal Zones, Helvetic/Penninic style nappes were generated, whereas flower upright axial structures developed along transpressive, intraplate shear zones. These features contrast with those preserved in the thin-skinned IBVA External Zones, dominated by décollements above (un-)deformed Palaeozoic and Cadomian basement. The inferred attenuation of rheological contrast between Cadomian basement and Palaeozoic cover can be explained by inherited fabrics due to thermal softening operated during the Cambrian–Lower Devonian extensional regime. Deeper décollements (and subsequent strain partitioning) are also expected to develop at the upper-lower crust (and at the Moho?) transition, as imaged by the available seismic profiling and MT surveys. The whole data implies a significant discontinuity between Cadomian and Variscan Cycles that should have constrained subsequent lithospheric evolution.     

Dynamics of carbon and CO<Subscript>2</Subscript> removals by Brazilian forest plantations during 1990–2016

Background

We analyzed the dynamics of carbon (C) stocks and CO₂ removals by Brazilian forest plantations over the period 1990–2016. Data on the extent of forests compiled from various sources were used in the calculations. Productivities were simulated using species-specific growth and yield simulators for the main trees species planted in the country. Biomass expansion factors, root-to-shoot ratios, wood densities, and carbon fractions compiled from literature were applied. C stocks in necromass (deadwood and litter) and harvested wood products (HWP) were also included in the calculations.

Results

Plantation forests stocked 231 Mt C in 1990 increasing to 612 Mt C in 2016 due to an increase in plantation area and higher productivity of the stands during the 26-year period. Eucalyptus contributed 58% of the C stock in 1990 and 71% in 2016 due to a remarkable increase in plantation area and productivity. Pinus reduced its proportion of the carbon storage due to its low growth in area, while the other species shared less than 6% of the C stocks during the period of study. Aboveground biomass, belowground biomass and necromass shared 71, 12, and 5% of the total C stocked in plantations in 2016, respectively. HWP stocked 76 Mt C in the period, which represents 12% of the total C stocked. Carbon dioxide removals by Brazilian forest plantations during the 26-year period totaled 1669 Gt CO_2-e.

Conclusions

The carbon dioxide removed by Brazilian forest plantations over the 26 years represent almost the totality of the country´s emissions from the waste sector within the same period, or from the agriculture, forestry and other land use sector in 2016. We concluded that forest plantations play an important role in mitigating GHG (greenhouse gases) emissions in Brazil. This study is helpful to improve national reporting on plantation forests and their GHG sequestration potential, and to achieve Brazil’s Nationally Determined Contribution and the Paris Agreement.

     

Electrodialytic treatment of sewage sludge: influence on microbiological community

This study aimed to evaluate the changes in microbiological communities present in sewage sludge (SS) when subjected to an electric field. The establishment of these relations is important to design and optimize an electrotechnology that not only promotes a direct degradation of the emerging organic contaminants, through electrodegradation, but also stimulates their biodegradation. Different current intensities were used continuously or by steps, in a two compartment electrodialytic (ED) cell. Samples collected between May and July of 2015 were analysed, prior to ED treatment, and the 35 Taxa identified were divided in 12 groups. Initial samples, collected on May, were mainly constituted by stalked ciliates (86%), followed by shelled amoebae (8%), whereas the samples collected between June and July presented higher number of shelled amoebae, between 52 and 92%. Epistylis, Vorticella and Arcella gibbosa were the most frequent protozoa identified. Samples richness (R) was between 7 and 14, Simpson’s biodiversity index (D) between 0.45 and 0.69, and evenness between 0.42 and 0.65. At the end of the ED experiments, a decrease in the number of identified Taxa and individuals was observed and, consequently, SS biodiversity also decreased. This decline was more pronounced in the ED experiments conducted with currents above 50 mA (0.10 mA cm^?2). In terms of abundance, the final SS was mainly constituted by shelled amoebae that showed to be the most resistant to the conditions within the ED cell. The obtained results showed that the studied conditions within the ED cell were not appropriate to the microbiological communities, which influenced the final SS quality.     

Geochemical anomaly separation by multifractal modelling

Geochemical anomaly separation using the concentration–area method as applied to two different geological settings in Portugal is investigated. Soil geochemistry data sets were used in both settings. Geochemical surveys were conducted for the exploration of gold mineralisations in quartz veins associated with major shear zones (Arouca, NW Portugal). Similar surveys were also undertaken for V and Ti exploration related to the accumulation of oxide minerals in gabbroic rocks belonging to an exotic oceanic terrane (Mombeja) and to a late calc-alkaline igneous complex (Odivelas), both in SE Portugal. Results have been interpreted using the extensive information available for each area, which includes detailed geological mapping, structural information, whole-rock chemical analysis, and mineralogical data. Anomalous thresholds for each area were computed and compared mainly with whole-rock chemical analyses and mineral chemistry data. In the Arouca area, anomalies at the local scale were identified for Au (630 ppb), As (912 ppm), and Sb (630 ppm), and at a regional scale for As (96 ppm). In the Mombeja area, anomalies at a regional scale were identified for V (88 ppm), Cr (232 ppm), and Ni (76 ppm), and the available results for Odivelas area suggest the existence of local scale V anomalies, whose magnitude is generally above 400 ppm. In the Arouca area, the correlation between these threshold values and grades in rocks is clearly shown, especially by discriminating two different mineralising events. The second, and most important mineralising event is responsible for grades above 1 ppm for Au in the mineralised structures, contrasting with grades below 500 ppb from the first event. The anomalies identified in Mombeja reflect mainly a regional distribution of the outcropping rock types, mainly metagabbros and serpentinised peridotites, with special emphasis on the correlation between V and the gabbroic rocks. The thresholds obtained for each element are always lower than their mean content in the rocks. The Odivelas area shows threshold values for V clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of oxide minerals within the gabbroic rocks. In order to overcome data scarcity, a scheme to super-sampling the population by using estimated values with ordinary kriging in the computation of the anomalous thresholds was essayed. These results, albeit needing further validation, gave some indicative references to the economic potential of this area for V mineralisations.