Eco-hydrological role of deep aquifers in the Salado sedimentary basin in the Province of Buenos Aires,Argentina

Although not well known, the eco-hydrological functions of deep aquifers (those having no contact with surface hydrological events) play an important role in the hydrological regime because they can affect the type of habitats, the availability of water and nutrients and the salinity of the medium, among other environmental features. This work aims at characterizing the deep Tertiary hydrogeological units of the Salado sedimentary basin in the Province of Buenos Aires, Argentina, at a regional scale, and to determine their environmental importance in the hydrological cycle. The geological characterization of the study area is based on the drilling profiles from oil exploration wells bored by different oil companies between 1948 and 1994, and also from the existing literature. The conclusion is that water exchange between quaternary surface aquifers in contact with atmospheric events and deep tertiary aquifers is one of the main processes that keep the hydrologic balance of the region. Not only is this crucial for the conservation of the numerous and well-developed ecosystems in the basin wetlands, but also significant for the agricultural and cattle-raising activities of the region.     

Stability of biomass-derived black carbon in soils

Black carbon (BC) may play an important role in the global C budget, due to its potential to act as a significant sink of atmospheric CO₂. In order to fully evaluate the influence of BC on the global C cycle, an understanding of the stability of BC is required. The biochemical stability of BC was assessed in a chronosequence of high-BC-containing Anthrosols from the central Amazon, Brazil, using a range of spectroscopic and biological methods. Results revealed that the Anthrosols had 61-80% lower (P < 0.05) CO₂ evolution per unit C over 532 days compared to their respective adjacent soils with low BC contents. No significant (P > 0.05) difference in CO₂ respiration per unit C was observed between Anthrosols with contrasting ages of BC (600-8700 years BP) and soil textures (0.3-36% clay). Similarly, the molecular composition of the core regions of micrometer-sized BC particles quantified by synchrotron-based Near-Edge X-ray Fine Structure (NEXAFS) spectroscopy coupled to Scanning Transmission X-ray Microscopy (STXM) remained similar regardless of their ages and closely resembled the spectral characteristics of fresh BC. BC decomposed extremely slowly to an extent that it was not possible to detect chemical changes between youngest and oldest samples, as also confirmed by X-ray Photoelectron Spectroscopy (XPS). Deconvolution of NEXAFS spectra revealed greater oxidation on the surfaces of BC particles with little penetration into the core of the particles. The similar C mineralization between different BC-rich soils regardless of soil texture underpins the importance of chemical recalcitrance for the stability of BC, in contrast to adjacent soils which showed the highest mineralization in the sandiest soil. However, the BC-rich Anthrosols had higher proportions (72-90%) of C in the more stable organo-mineral fraction than BC-poor adjacent soils (2-70%), suggesting some degree of physical stabilization.     

Full-scale experimental investigations on the response of a flooded passenger vehicle under subcritical conditions

Natural Hazards - Vehicles can be easily swept away by floodwaters once the flow velocity and depth reach certain critical limits, with probabilities toward fatality reported to be nearly 50%....