Fluvial carbon export and CO2 efflux in representative nested headwater catchments of the eastern La Plata River Basin

This study involved a baseline evaluation of fluvial carbon export and degas rates in three nested rural catchments (1 to 80 km²) in Taboão, a representative experimental catchment of the Upper Uruguay River Basin. Analyses of the carbon content in stream waters and the catchment carbon yield were based on 4‐year monthly in situ data and statistical modeling using the United States Geological Survey load estimator model. We also estimated p CO₂ and degas fluxes using carbonate equilibrium and gas‐exchange formulas. Our results indicated that the water was consistently p CO₂ saturated (~90% of the cases) and that the steep terrain favors high gas evasion rates. The mean calculated fluvial export was 5.4 tC·km^?2·year^?1 with inorganic carbon dominating (dissolved inorganic carbon:dissolved organic carbon ratio >4), and degas rates (~40 tC km^?2·year^?1) were nearly sevenfold higher than the downstream export. The homogeneous land use in this nested catchment system results in similar water‐quality characteristics, and therefore, export rates are expected to be closely related to the rainfall–runoff relationships at each scale. Although the sampling campaigns did not fully reproduce storm‐event conditions and related effects such as flushing or dilution of in‐stream carbon, our results indicated a potential link between dissolved inorganic carbon and slower hydrological pathways related to subsurface water storage and movement.     

Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis

The Balearic Basin is a young basin composed of thick Plio–Quaternary sediments, including active gravity sedimentation. During the Quaternary, gravity processes deposited (1) turbidite systems, either as symmetrical fans (Petit-Rhône and Valencia fans) or asymmetrical ridges (Marseille–Planier, Grand-Rhône and Pyreneo-Languedocian ridges) and (2) several mass-transport deposits, indicating recurrent sedimentary failures of the margin. This paper synthesizes previous works and proposes a chronological sedimentary evolution for the basin. Except for the last 20 ka, the chronostratigraphy remains poorly constrained but should soon be established for the last 500 ka, based on the PROMESS1 drillings on the outer shelf of the Gulf of Lions, and hopefully for the last 30 Ma, based on ultra-deep drilling in the deep basin from aboard the Chikyu research vessel (IODP proposal Pre699).     

Influence of climate variability on land degradation (desertification) in the watershed of the upper Paraíba River

The study aimed to evaluate the influence of the rainfall and aridity index variability on the process of land degradation (desertification) in order to establish the current degree of increase or decrease in dryness in the watershed of the upper Paraíba River. It included all or part of 18 municipalities, distributed in the western and eastern Cariri regions of Paraíba state. The monthly average values of reference evapotranspiration according to Penman-Monteith method were applied in the annual hydrological balance for obtaining the annual time series of the aridity index for the period from 1950 to 2013. The Mann-Kendall test (MK) was used for trend identification in the annual time series of rainfall and aridity index, at a significance level of α = 0.05. The slope of the trends was obtained by Sen’s method, and the values of rainfall, aridity index, and statistics MK were spatially kriging, to generate thematic maps. The results indicate an increase in rainfall and reduced dryness in the watershed of the upper Paraíba River, conditions that do not contribute to trigger the process of land degradation (desertification), indicating that the cause of this environmental problem is not climatic. Thus, it can be suggested that the observed manifestations of land degradation (desertification) derive much of human than climatic actions. However, there is a trend of increasing dryness and reducing rainfall in the central portion of the watershed, with stronger core in the location of Camalaú. The spatial distribution of rainfall and aridity index shows that minimum values of rainfall coincide with maximum values of the aridity index. Higher values of rainfall were observed in the northwestern portion of the watershed, while the northeast and southeast portions had the lower rainfall values, with the strongest core in the locality of Cabaceiras. The eastern sector of the watershed has high dryness, unlike the western sector, rainier, with minimum values of dryness. In the western portion of the watershed, the aridity index was in the range considered semiarid, with moderate susceptibility to land degradation process. Similarly, in the eastern portion, the dryness stood in the range considered arid, with high susceptibility. The cores with more pronounced dryness correspond to the municipalities of Cabaceiras, Caraúbas, and São João do Cariri.     

Amazonsaurus maranhensis gen. et sp. nov. (Sauropoda, Diplodocoidea) from the Lower Cretaceous (Aptian–Albian) of Brazil

A new genus and species of an Aptian–Albian sauropod from the Itapecuru Formation, northern Brazil, Amazonsaurus maranhensis, is described. It is known from an incomplete, but diagnostic postcranial skeleton. The new taxon possesses several autapomorphies, such as the anterior caudal vertebrae with lateral laminae formed by the coalescence of the spinoprezygapophyseal and postzygodiapophyseal laminae and, to a lesser extent, of the postzygodiapophyseal laminae. It exhibits many synapomorphies supporting its inclusion in the Diplodocoidea. These include high caudal neural arches and anterior caudal neural arches with spinoprezygapophyseal laminae on the lateral aspect of the neural spine. This record is consistent with previous hypotheses on the existence of a community of Afro-South American dinosaurs.     

Numerical study on the effect of submerged depth on the horizontal plate wave energy converter

The growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method （FVM）. In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid （VOF） is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea （HP） on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for HP=0.53 m （88% of the depth）. This efficiency is 17% larger than that found in the worst case （HP=0.46 m, 77% of the depth）.     

Evaluation and modeling of runoff and sediment yield for different land covers under simulated rain in a semiarid region of Brazil

This paper quantifies the runoff and sediment yield for four different land covers in a semiarid region of Brazil. The WESP model, a distributed, event-oriented runoff-erosion model, was applied and its physical parameters, N_s and K_R, were adjusted based on observed runoff and sediment yield data using simulated rainfall with an average intensity of 53 mm h^-1. The sediment yield obtained was 53.02 kg ha^-1 (caatinga vegetation), 231.96 kg ha^-1 (bare soil), 309.75 kg ha^-1 (beans), and 847.38 kg ha^-1(corn). The results showed that caatinga cover yields the lowest erosion and runoff when compared to the other treatments. The results also show that the sediment yield and runoff values simulated with N_s, K_I, and K_R parameters were well calibrated, within acceptable deviations. The caatinga vegetation was more effective in protecting the soil, when compared to the other types of coverage. The beans and corn covers had the highest values of runoff and sediment yield, even higher than those observed for bare soil.     

Temporal variability of throughfall as a function of the canopy development stage: from seasonal to intra-event scale

ABSTRACT

The interception process impacts rainfall magnitude and intensity under the canopy. In this study, the effect of plant interception on throughfall characteristics was assessed in the deciduous Caatinga vegetation, at different canopy development stages and for temporal scales ranging from seasonal to the intra-event scale. Throughfall and stemflow percentages were slightly higher at the onset of the rainy season, when leaf area density is low, with resulting lower interception losses. However, there was no statistical difference among the variables at the seasonal scale. At the intra-event scale, average and maximum throughfall intensity at different time intervals showed statistical difference between the stages of canopy development. Regardless of leaf area density and rainfall depth, vegetation is able to retain all the water up to 2 min in the beginning of each rainfall event with accumulated rainfall smaller than 0.6 mm. Furthermore, the Caatinga vegetation attenuates the rainfall intensity by 30–40%.     

Evidence of scavenging on remains of the gomphothere Haplomastodon waringi (Proboscidea: Mammalia) from the Pleistocene of Brazil: Taphonomic and paleoecological remarks

This study reports implications of different tooth marks left by carnivorous mammals on long bones of Haplomastodon waringi from the Quaternary of Águas de Araxá, Minas Gerais, Brazil. Analyses of gnawing damage by ursids, felids, and canids have shown that these groups produce pits on bone surfaces when the gnawing is superficial, and punctures more often when the prey is intensely consumed. Scratches or scoring marks are most often associated with gnawing by canids, which may spend a long time gnawing the bones, leading to differential tooth marking. The gomphothere bones at Águas de Araxá did not result from predation, but are a consequence of a local mass mortality in a period of low environmental humidity, with little water and a scarcity of food. Canids frequently act as opportunistic scavengers during periods when herbivores face food shortages. Previous studies of necrophagous dermestid larvae indicate that the gomphothere carcasses of Águas de Araxá were exposed for a long period of time after death. These insects are the last consumers of a carcass because they act only when the body fat is completely lost. Thus, the gomphothere carcasses at Águas de Araxá suffered canid necrophagy in the early stages of decomposition, possibly during a drought period. Thereafter, the gomphothere carcasses would have been exposed for a period about 230 days until the final burial event.     

Contrasting oxygen fugacity of I- and S-type granites from the Araçuaí orogen,SE Brazil: an approach based on opaque mineral assemblages

Mineralogy and Petrology - This study presents mineralogical characterization of opaque assemblages from I- and S-type granites from the Araçuaí orogen, southeastern Brazil that belong...