Discharge areas as a useful tool for understanding recharge areas, study case: Mexico Catchment

At present, demographic growth is a significant issue related to environmental damage due to an excessive use of water and forest. Governments are now interested in formulating new strategies that might help to reach a sustainable development. Thus, the Mexican Federal Government initiated an Environmental Hydrological Services Payment Programme in 2003 to preserve its forest territory, specifically to keep its groundwater recharge potential. However, the application of this programme was not supported by hydrogeological studies defining the physical media, rainwater and groundwater flows through proper identification of recharge areas as well as probable impacts to groundwater or to other components of the environment. Wide-view system studies still need to be incorporated. This work highlights the importance of including groundwater flow system investigations as a basis to support environmental projects where a clear understanding of groundwater functioning in relation to a zone receiving payment for hydrological environmental services is required. Stable isotopes and chemical characteristics of non-evaporated groundwater in discharge areas allow the computation of the altitude of recharging precipitation from where possible recharge area location is proposed. Finally, this paper puts forward groundwater flow system definition as a basic tool to support recommendation for an adequate water and environmental management.     

Geochemical fractionation of manganese in the Riogrande II reservoir, Antioquia, Colombia

The Riogrande II reservoir in Colombia has a total storage capacity of 240 million m³ and lies 2,270 m above sea level. The reservoir is used for power generation, water supply and environmental improvement. Dissolved manganese (Mn) is removed from reservoir water dedicated to domestic use by purification processes. Removal of Mn, however, poses a major challenge to purification processes and warrants the study of ways to naturally reduce dissolved Mn levels in the reservoir. The source of Mn within the reservoir is not well understood, however, presumably arises from sediment mobilization initiated by variation in pH, redox potential (ORP or Eh), dissolved oxygen (O₂) and ionic strength conditions. This study investigated conditions within the reservoir to further understand Mn transfer from the sediment into the water column. O₂, pH, oxidation–reduction potential (ORP or Eh), organic matter content and electric conductivity were measured in water samples and sediment from the reservoir. Sequential extraction (SE) procedures were used to test the specific effects exerted by each of these conditions on Mn mobilization from the sediments. The European Community Bureau of Reference (BCR) sequential extraction procedure was used to quantify metals in sediment (referred to as the BCR extraction below). Statistical analysis of geochemical data from water samples (both water column and sediment pore water) and sediments demonstrated the conditions under which Mn can be released from sediments into the water column. The results indicated a primarily oxic water column and anoxic reducing conditions in the sediment (ORP or Eh ≤ ?80 mV). The pH of water in contact with bottom sediments varied from 7.6 to 6.8. The pH of sedimentary pore water varied from 6.8 to 4.7. The sediments contained significant amounts of organic matter (20 %). Chemical extractions showed that the exchangeable fraction contained over 50 % of the total Mn within sediments. Microscopic analysis using scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) indicated that Mn does not occur within well-crystallized mineral phases in the Riogrande II sediments. A large proportion of Mn exists instead as material adsorbed onto the surfaces of recently deposited sediment particles. Bacterial oxidation of organic matter may cause the observed anoxic conditions at the bottom of the reservoir. Mineralization of organic matter therefore contributes to reducing conditions within the sediments. Mobilization of Mn from the sediment into the water column may result from reductive dissolution of this fraction. Manganese release by this mechanism diminishes the water quality of the Riogrande II reservoir and warrants further study.     

The significance of Chara vegetation in the precipitation of lacustrine calcium carbonate

A significant portion of calcium carbonate is deposited in lake sediments as a result of biological processes related to the photosynthetic activity of phytoplankton in the pelagic realm and, in addition, macrophytes in the littoral zone. Lake Wigry, one of the largest lakes in Poland (north‐east Poland), is characterized by: (i) carbonate sediments with a CaCO₃ content exceeding 80% within the littoral zone; and (ii) large areas of submerged vegetation dominated by charophytes (macroscopic green algae, Characeae family). It is claimed that charophytes are highly effective in utilizing HCO₃^? and forming thick CaCO₃ encrustations. Thus, this study was aimed at evaluating the CaCO₃ production by dense Chara stands overgrowing the lake bottom reaching a depth of 4 m. In late July 2009, the fresh and dry mass of plants, the percentage contribution of calcium carbonate and the production of CaCO₃ per 1 m² were investigated along three transects at three depths (1 m, 2 m and 3 m, with each sample area equal to 0·0625 m²) per transect. The composition and structure of phytoplankton and the physico‐chemical properties of the water analysed in both the littoral and pelagic zones served as the environmental background and demonstrated moderately low fertility in the lake. The greatest dry plant mass exceeded 1000 g m^?2 and CaCO₃ encrustations constituted from 59% to over 76% of the charophyte dry weight. Thus, the maximum and average values of carbonates precipitated by charophytes were 685·5 and 438 g m^?2, respectively, which exceeded previously reported results. A correlation of carbonate production with the depth of Chara stands was detected, and intermediate depths offered the most favourable conditions for carbonate precipitation (589 g m^?2 on average). As precipitated carbonates are ultimately stored in bottom deposits, the results highlight the significance of charophytes in lacustrine CaCO₃ sedimentation.     

The Mesolithic–Neolithic transition in southern Iberia

New data and a review of historiographic information from Neolithic sites of the Malaga and Algarve coasts (southern Iberian Peninsula) and from the Maghreb (North Africa) reveal the existence of a Neolithic settlement at least from 7.5 cal ka BP. The agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the Mesolithic populations. The timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems, including upwelling intensity, sea-level changes and increased aridity in the Sahara and along the Iberian coast. These changes likely impacted the subsistence strategies of the Mesolithic populations along the Iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the Mesolithic–Neolithic transition. The rapid expansion and area of dispersal of the early Neolithic traits suggest the use of marine technology. Different evidences for a Maghrebian origin for the first colonists have been summarized. The recognition of an early North-African Neolithic influence in Southern Iberia and the Maghreb is vital for understanding the appearance and development of the Neolithic in Western Europe. Our review suggests links between climate change, resource allocation, and population turnover.     

Spatio-Temporal Analysis of the Concentration and Composition of Planktonic Cyanobacteria Community in a Tropical Reservoir Chain

Water Resources - Cyanobacteria are very heterogeneous microorganisms that are important in both natural and artificial environments. Nevertheless, an uncontrolled growth of cyanobacteria, or...     

Canonical and phantom scalar fields as an interaction of two perfect fluids

In this article we investigate and develop specific aspects of Friedmann-Robertson-Walker (FRW) scalar field cosmologies related to the interpretation that canonical and phantom scalar field sources may be interpreted as cosmological configurations with a mixture of two interacting barotropic perfect fluids: a matter component ρ ₁(t) with a stiff equation of state (p ₁=ρ ₁), and an “effective vacuum energy” ρ ₂(t) with a cosmological constant equation of state (p ₂=?ρ ₂). An important characteristic of this alternative equivalent formulation in the framework of interacting cosmologies is that it gives, by choosing a suitable form of the interacting term Q, an approach for obtaining exact and numerical solutions. The choice of Q merely determines a specific scalar field with its potential, thus allowing to generate closed, open and flat FRW scalar field cosmologies.     

Differences in population growth of rotifers and cladocerans raised on algal diets supplemented with yeast

We studied the population growth of two rotifer (Brachionus calyciflorus and Brachionus rubens) and two cladoceran (Ceriodaphnia dubia and Moina macrocopa) species fed three diets (Chlorella vulgaris (Ch), Scenedesmus acutus (Sc) and yeast (Saccharomyces cerevisiae) (Y) in seven combinations (alone or mixed in equal proportions (on dry weight basis): Ch+Sc, Ch+Y, Sc+Y and Ch+Sc+Y). In general, the cladocerans were more adversely affected than the rotifers on the diet of yeast alone. The population growth curves of B. calyciflorus and B. rubens revealed that algal diets were superior to yeast. Regardless of diet, B. rubens had a longer lag phase and delayed peak density compared to B. calyciflorus. Both M. macrocopa and C. dubia had higher peak abundances when fed mixed algae than on either alga offered separately. B. rubens, C. dubia and M. macrocopa reached significantly lower maximal densities on diets containing yeast, S. acutus or both. When the data on the eggs/female (egg ratio) were plotted as function of population density, we found an inverse relation, which was curvilinear for B. calyciflorus and linear for B. rubens. In general, we found that yeast could effectively supplement algal diets in all the test species, thereby reducing costs in large scale production of zooplankton.     

The degree of astaticism of an astatic magnetometer

Summary The degree of astaticism is the fundamental parameter of an astatic magnetometer, an instrument used in geophysics for magnetic measurements of rock specimens. The degree of astaticism is formulated with a view to the vectorial character of the defining quantities and with a view to the effect of the geomagnetic field. As regards measuring the parameter, the mirror method is given, which makes use of the positive and negative orientation of the astatic system relative to the north or east. The measure of the value of the parameter is the change of the sensitivity of the system and the deflection of its zero position, compensated for by the magnetic field of the calibration coil. The problem of the degree of astaticism is treated complexly, inclusive of the measurement of the parameter, which in practice is of fundamental importance for adjusting the systems for manufacturing astatic magnetometers.     

Volcanic rocks of methana,South Aegean arc,Greece

Cale-alkalic lavas and associated intrusives and cognate xenoliths, from the peninsula of Methana, are comparable geochemically with similar lavas from elsewhere in the South Aegean arc. At least four differentiation series have been recognized, largely of basaltic andesite to rhyodacite type, in which hydrous and dry conditions alternated. The compositional range of minerals other than plagioclase is limited. The chemical mineralogy of olivines and pyroxenes has been studied in detail. An aluminous bronzite that is found, contrary to previous interpretations, does not appear to be a high pressure phase. The chemical composition of the basic rocks and basic xenoliths suggests that the parent material of these lavas was of high alumina basalt composition. The abundance of accumulative xenoliths and the change of the mafic minerals to more iron-rich compositions towards the more acid end of each series, suggest that phenocryst fractionation has been the major process for the later stages of the evolution of all these rocks.