Rare-earth elements in groundwaters from the Osamu Utsumi mine and Morro do Ferro analogue study sites, Poços de Caldas, Brazil

Data are presented on rare-earth elements (REE) in prefiltered (<450 nm) near-surface and deeper groundwaters and in corresponding particulate matter (>450 nm) from the Osamu Utsumi uranium mine and the Morro do Ferro thorium-REE-deposit. Groundwaters from both sites typically contain between 1–50 μg/l of total REE, but can reach values of up to 160 μg/l in the deepest borehole F4 (U-Mine: 150–415 m). Even higher REE concentrations of up to 29 mg/l were measured in acidic, sulfate-rich near-surface waters of the same site. The chondrite-normalized REE patterns in deeper, more reducing groundwaters and in their corresponding suspended particle fractions are similar to those observed in the bedrock (phonolites), indicating that bedrock leaching and secondary mineral sorption occurred without significant fractionation between these elements, in accordance with the only small variations in the stability constants of the expected REE-sulfate complexes in these waters. Groundwaters from the unsaturated zone of both sites show a very characteristic cerium depletion (less pronounced than that observed in the corresponding suspended particulate fractions), which is most probably related to the oxidation of Ce (III) under the prevailing E_h-conditions of these waters (600 to 800 mV), and to sorption/precipitation reactions of the much less soluble Ce(IV) species. Coarse particulate matter (>450 nm), composed mainly of amorphous ferric hydrous oxides, has a strong capacity for sorption of REE. This is shown by its very high REE concentrations, in some boreholes > 8,000 μg/g (total REE), and by the calculated association ratios R_a (ml/g), which are in the order of 10⁵ to 10⁶. The implications of these findings for the migration behavior of REE in both environments are discussed.     

The big picture of field hydrology studies in Brazil

ABSTRACT

In-situ

hydrological monitoring is essential for a proper decision-making process and modelling. Efforts have been made in Brazil to carry out field activities at the basin scale, but how complete and comprehensive are those studies? Where are they located? How long have they been carried out? What are the main findings? To answer these questions, an overview of experimental monitoring basins in Brazil is presented, listing their geographical locations, monitored variables, operational status, monitoring periods and main publications. We identified 60 monitored sites, spread across most Brazilian biomes, with an average monitoring period of 12 years. However, some publications from these monitoring studies are not fully accessible to the international community. Field hydrology activities in Brazil contribute to a better understanding of hydrological processes in humid and semi-arid regions and inform us about the impacts of land-use change on water quality and quantity.     

Compensating for estimation smoothing in kriging

Smoothing is a characteristic inherent to all minimum mean-square-error spatial estimators such as kriging. Cross-validation can be used to detect and model such smoothing. Inversion of the model produces a new estimator—compensated kriging. A numerical comparison based on an exhaustive permeability sampling of a 4-ft² slab of Berea Sandstone shows that the estimation surface generated by compensated kriging has properties intermediate between those generated by ordinary kriging and stochastic realizations resulting from simulated annealing and sequential Gaussian simulation. The frequency distribution is well reproduced by the compensated kriging surface, which also approximates the experimental semivariogram well—better than ordinary kriging, but not as well as stochastic realizations. Compensated kriging produces surfaces that are more accurate than stochastic realizations, but not as accurate as ordinary kriging.     

Dispersal and germination ofProsopis flexuosa(Fabaceae) seeds by desert mammals in Argentina

The ‘algarrobo’Prosopis flexuosais an important food resource in the Monte Desert of Argentina. Native, domestic, and exotic mammals consume the fruit of this legume and disperse the seed through faeces. In the present study we analyse the effect that different dispersal agents (cattle, horse, European wild boar, rodents, gray fox) have on seed damage, viability, and germination. Cattle increase germination at the expense of reduced viability, whereas horses maintain viability but do not contribute to a prompt germination response. Among native mammals, the gray fox maintains seed viability without increasing germination, whereas rodents affect seed viability but enhance germination rates. The European wild boar, however, damages all of the seeds it consumes.     

Global risks of Bedellia somnulentella (Lepidoptera: Bedelliidae) invasion: a modeling exercise using a mechanistic model,CLIMEX

Theoretical and Applied Climatology - This study aimed to identify the global risk of invasion and establishment of Bedellia somnulentella, a pest of the sweet potato crop, for the present and...     

A Surface-Layer Study of the Transport and Dissipation of Turbulent Kinetic Energy and the Variances of Temperature,Humidity and CO$$_$$

We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO\(_2\) content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afternoon and Sunset Turbulence experiment. The consequences of dissipation similarity in the variance transport are also discussed and quantified. The results show that, for the convective atmospheric surface layer, the non-dimensional dissipation terms can be expressed in the framework of Monin–Obukhov similarity theory and are independent of whether the variable is temperature or moisture. The scalar similarity in the dissipation term implies that the characteristic scales of the atmospheric surface layer can be estimated from the respective rate of variance dissipation, the characteristic scale of temperature, and the dissipation rate of temperature variance.     

Provenance and tectonic implications of Orán Group foreland basin sediments,Río Iruya canyon,NW Argentina (23° S)

Foreland basins are important recorders of tectonic and climatic processes in evolving mountain ranges. The Río Iruya canyon of NW Argentina (23° S) exposes ca. 7500 m of Orán Group foreland basin sediments, spanning over 8 Myr of near continuous deposition in the Central Andes. This study presents a record of sedimentary provenance for the Iruya Section in the context of a revised stratigraphic chronology. We use U‐Pb zircon ages from six interbedded ash layers and new magnetostratigraphy to constrain depositional ages in the section between 1.94 and 6.49 Ma, giving an average sedimentation rate of 0.93 ± 0.02 (2σ) km Myr^?1. We then pair U‐Pb detrital zircon dating with quartz trace‐element analysis to track changes in sedimentary provenance from ca. 7.6 to 1.8 Ma. Results suggest that from ca. 7.6 to ca. 6.3 Ma, the Iruya watershed did not tap the Salta Group or Neogene volcanics that are currently exposed in the eastern Cordillera and Puna margin. One explanation is that a long‐lived topographic barrier separated the eastern Puna from the foreland for much of the mid‐late Miocene, and that the arrival of Jurassic‐Neogene zircons records regional tectonic reactivation at ca. 6.3 Ma. A second major provenance shift at ca. 4 Ma is marked by changes in the zircon and quartz populations, which appear to be derived from a restricted source region in Proterozoic‐Ordovician meta‐sediments. Considered in conjunction with the onset of coarse conglomerate deposition, we attribute this shift to accelerated uplift of the Santa Victoria range, which currently defines the catchment's western limit. A third shift at ca. 2.3 Ma records an apparent disconnection of the Iruya with the eastern Puna, perhaps due to defeat of the proto Rio‐Iruya by the rising Santa Victoria range. This study is one of the first applications of quartz trace‐element provenance analysis, which we show to be an effective complement to U‐Pb detrital zircon dating when appropriate statistical methods are applied.