Land use and land cover dynamics in Leiria City: relation between peri-urbanization processes and hydro-geomorphologic disasters

Natural Hazards - The objective of the present study is to evaluate the relation between the spatial and temporal dynamics of Land Use and Land Cover (LULC) and the hydro-geomorphological processes...     

Permselective Membrane Fouling During Azo Dye Wastewater Treatment

A Na‐montmorillonite membrane wastewater renovation prototype system was developed to specifically treat an ionic azo dye. Efficiency of this prototype system was limited to membrane fouling. Fouling rates were not consistently uniform owing to steric effects and competition for exchange sites. The decrease in solute rejection with time can be attributed to the decrease in the relative permeability of the compacted Na‐montmorillonite membrane to the dye with time due to fouling. This decrease occurs probably as a two‐step nucleation–growth mechanism with the nucleation part dependent in part on solvent flux, number of nucleation sites on the membrane, and sorbed mass part that controls solute flux and organic polymerization. The effect of concentration polarization was significant since the flux was higher than the mass‐transfer coefficient. The low diffusion coefficient of the ionic azo dye resulted in low mass transfer coefficients. The most important macromolecular solution properties to be considered for pilot systems may include high concentration‐dependent viscosity, possible non‐Newtonian fluid behavior, and low and concentration‐dependent self‐diffusivity amongst other factors. For pilot systems, the greater the quantity of large macromolecules in the ambient water, the greater the necessity of reducing the permselectivity of the membrane to prevent significant polarization.     

Modelling discharge through artesian springs based on a high‐resolution piezometric network

Artesian springs are localized aquifer outlets that originate when pressurized ground water is allowed to rise to the surface. Computing artesian discharge directly is often subject to practical difficulties such as restricted accessibility, abundant vegetation or slow flow rates. These circumstances call for indirect approaches to quantify flow. This paper presents a method to estimate ground water discharge through an upwelling spring by means of a three‐layer steady‐state groundwater flow model. Model inputs include on‐site measurements of vertical sediment permeability, sediment temperatures and hydraulic gradients. About 70 spring bed piezometers were used to carry out permeability tests within the spring sediments, as well as to quantify the hydraulic head at different depths below the discharge point. Sediment temperatures were measured at different depths and correlated to permeabilities in order to demonstrate the potential of temperature as a substitute for cumbersome slug tests. Results show that the spatial distribution of discharge through the spring bottom is highly heterogeneous, as sediment permeability varies by several orders of magnitude within centimetres. Sensitivity analyses imply that geostatistical interpolation is irrelevant to the results if field datasets come from a sufficiently high resolution of piezometric records. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of geostatistical methods in gold geochemical anomalies identification (Montemor-O-Novo, Portugal)

The study described herein concerns the application of geostatistical methods to data soil from Montemor-O-Novo area (Southern Portugal). In the area, the gold mineralised zones (Banhos, Caeiras, Falés, Gamela, Malaca and Monfurado) are characterised by different geological settings and mineralogical assemblages. A total of 1211 soil samples were collected in Montemor-O-Novo area and analysed for Cu, Pb, Zn, As, Ba and Au by atomic absorption spectrometry.To account for spatial structure, simple and cross variograms were computed for the main directions of the grid sampling. From the experimental variograms a linear model of coregionalization composed of three structures, a nugget effect and two anisotropic spherical structures, was fitted to each of the six variables. The coregionalization matrices deduced from the theoretical model show the relationships between the variables at different scales. These matrices were compared with those obtained by principal component analysis (PCA).This methodology was the basis for estimating the corresponding spatial components (Y0, Y1 and Y2) using factorial kriging analysis (FKA). Maps of raw data, Y0, Y1 and Y2 were made for each variable.The use of multivariate analysis permit the study of the spatial structure intrinsic to geochemical data and the identification and refinement of significant anomalies related to Au-bearing mineral deposits.     

Assessment of site-effects using acceleration time series. Application to São Sebastião volcanic crater

The Azores archipelago is located at the North America, Eurasia and Africa triple junction and shows seismicity and volcanism typical of an active plate boundary. Terceira Island has been affected by several damaging earthquakes being the 1980 January 1st event (M=7.2) the strongest in Azores during the last century.     

Coastal and oceanic SST variability along the western Iberian Peninsula

The inter-annual variability of the sea surface temperature (SST) was analyzed along the western Iberian Peninsula in the region ranging from 9.5 °W to 21.5 °W and from 37.5 °N to 42.5 °N with a spatial resolution of 1°×1° from 1900 to 2008. Both coastal and oceanic SST showed an overall increase with warming and cooling cycles similar to those observed in the North Atlantic region and in previous regional studies. In addition, the evolution of coastal and ocean water has been observed to be different. In general, ocean water is more affected by the different warming–cooling cycles than coastal water. In spite of coast and ocean are highly influenced by global changes affecting the whole North Atlantic region, near shore SST has been observed to be correlated with local wind regime, which is itself a manifestation of the Eastern Atlantic (EA) teleconnection pattern.     

Gravity-geoelectric joint inversion over the Potiguar rift basin, NE Brazil

A joint inversion of gravity and geoelectrical data has been performed along a 100 km long profile across the oil-bearing Potiguar rift basin in NE Brazil. The integrated approach is based on the connection between density and resistivity of a sedimentary sequence through the porosity. Seventy-one gravity stations and twenty-nine vertical electrical soundings were carried out across the central part of the Early Cretaceous basin in the Precambrian Borborema Province to apply the proposed joint inversion. Both the physical properties and geometry of the multilayer deep model were well constrained by a wide set of prior information obtained by surface mapping, geophysical logs and seismic sections. The results reveal a rift architecture formed by a 5000 m thick half-graben structure separated by an intervening basement high and an extensive adjacent platform with a sedimentary infill of about 300 m thick. The calculated model shows geometries for the sedimentary density/resistivity interfaces in agreement with the seismostratigraphic sequences revealed by seismic section, representing a substantial improvement in comparison with previously published gravity models.     

Groundwater Discharge as a Source of Dissolved Carbon and Greenhouse Gases in a Subtropical Estuary

Groundwater may be highly enriched in dissolved carbon species, but its role as a source of carbon to coastal waters is still poorly constrained. Exports of deep and shallow groundwater-derived dissolved carbon species from a small subtropical estuary (Korogoro Creek, Australia, latitude ?31.0478°, longitude 153.0649°) were quantified using a radium isotope mass balance model (²³³Ra and ²²⁴Ra, natural groundwater tracers) under two hydrological conditions. In addition, air-water exchange of carbon dioxide and methane in the estuary was estimated. The highest carbon inputs to the estuary were from deep fresh groundwater in the wet season. Most of the dissolved carbon delivered by groundwater and exported from the estuary to the coastal ocean was in the form of dissolved inorganic carbon (DIC; 687 mmol m^?2 estuary day^?1; 20 mmol m^?2 catchment day^?1, respectively), with a large export of alkalinity (23 mmol m^?2 catchment day^?1). Average water to air flux of CO₂ (869 mmol m^?2 day^?1) and CH₄ (26 mmol m^?2 day^?1) were 5- and 43-fold higher, respectively, than the average global evasion in estuaries due to the large input of CO₂- and CH₄-enriched groundwater. The groundwater discharge contribution to carbon exports from the estuary for DIC, dissolved organic carbon (DOC), alkalinity, CO₂, and CH₄ was 22, 41, 3, 75, and 100 %, respectively. The results show that CO₂ and CH₄ evasion rates from small subtropical estuaries surrounded by wetlands can be extremely high and that groundwater discharge had a major role in carbon export and evasion from the estuary and therefore should be accounted for in coastal carbon budgets.