Methodology to evaluate the renewal period of carbonate aquifers: a key tool for their management in arid and semiarid regions,with the example of Becerrero aquifer,Spain

A methodological procedure is proposed for determining the renewal period (RP), which expresses the ratio of total storage to recharge of carbonate aquifers, and it was applied to the overexploited moderate-size Becerrero carbonate aquifer (southern Spain). To this end, geological and subsurface data—time domain electromagnetic (TEM) soundings and borehole logs—were integrated to construct a three-dimensional (3D) geological model of the aquifer. The interconnected porosity was estimated by analyzing 73 rock samples. The resulting 3D geometrical model makes it possible to quantify the fractions of the aquifer having a confined or unconfined behaviour. Based on the total storage capacity (179?·?10⁶–514?·?10⁶ m³) and available aquifer recharge estimation (4.8?·?10⁶–6.4?·?10⁶ m³/year), an RP between 37 and 106 years is obtained. In view of the RP, an exploitation rate slightly lower than the average recharge of the system is recommended, so that the piezometric level will be stable but below the discharge head that is produced through the springs in natural conditions. The proposed methodology to obtain an aquifer RP and the management strategies designed accordingly are of broad interest, especially for carbonate aquifers, which are abundant in arid and semiarid regions.     

Measurements of volcanic SO2 and CO2 fluxes by combined DOAS,Multi-GAS and FTIR observations: a case study from Turrialba and Telica volcanoes

Over the past few decades, substantial progress has been made to overcome the technical difficulties of continuously measuring volcanic SO₂ emissions. However, measurements of CO₂ emissions still present many difficulties, partly due to the lack of instruments that can directly measure CO₂ emissions and partly due to its strong atmospheric background. In order to overcome these difficulties, a commonly taken approach is to combine differential optical absorption spectroscopy (DOAS) by using NOVAC scan-DOAS instruments for continuous measurements of crateric SO₂ emissions, and electrochemical/NDIR multi-component gas analyser system (multi-GAS) instruments for measuring CO₂/SO₂ ratios of excerpts of the volcanic plume. This study aims to quantify the representativeness of excerpts of CO₂/SO₂ ratios measured by Multi-GAS as a fraction of the whole plume composition, by comparison with simultaneously measured CO₂/SO₂ ratios using cross-crater Fourier transform infrared spectroscopy (FTIR). Two study cases are presented: Telica volcano (Nicaragua), with a homogenous plume, quiescent degassing from a deep source and ambient temperature, and Turrialba volcano (Costa Rica), which has a non-homogeneous plume from three main sources with different compositions and temperatures. Our comparison shows that in our “easier case” (Telica), FTIR and Multi-GAS CO₂/SO₂ ratios agree within a factor about 3 %. In our “complicated case” (Turrialba), Multi-GAS and FTIR yield CO₂/SO₂ ratios differing by approximately 13–25 % at most. These results suggest that a fair estimation of volcanic CO₂ emissions can be provided by the combination of DOAS and Multi-GAS instruments for volcanoes with similar degassing conditions as Telica or Turrialba. Based on the results of this comparison, we report that by the time our measurements were made, Telica and Turrialba were emitting approximately 100 and 1,000 t day^?1 of CO₂, respectively.     

Exposure to ionising radiations arising from the operation of nuclear installations and cancer mortality

World-wide controversy continues to surround the question of whether exposure to ionising radiations arising from nuclear power plants and radioactive fuel cycle facilities could increase the risk of cancer. The objective was to analyse cancer mortality in towns close to Spanish nuclear power plants and radioactive fuel cycle facilities by reference to their history of exposure to artificial radiation generated by such emissions. An ecological cancer mortality study was conducted to know the effect of artificial radiation, estimated taken into account the magnitude of emissions, in towns ≤30 km of any installation. A model of atmospheric and aquatic dispersion of radionuclides was used. As reference, towns within a 50–100 km radius were matched with exposed by socio-demographic characteristics. For analysis purposes, log-linear Poisson models were fitted. The cumulative effective dose was the measure of exposure. Mortality rates ratios were calculated for each tumour site. Natural radiation and socio-demographic matching variables were included in the models, with ‘installation’ as a random effects term. The estimated cumulative artificial radiation dose was below 350 μSv for all sites. For nuclear power plants overall, analysis showed no positive association with increases in the cumulative dose. In the joint analysis of radioactive fuel cycle facilities, however, mortality was observed to rise with increases in the estimated radiation dose in the case of lung, bone and colorectal cancer, and in breast cancer among women. These results would not appear to be due to exposure arising from the operation of the installations, since were not reproduced around installations of the same type.     

Characterization of environmental impact on resources, using strategic assessment of environmental impact and management of natural spaces of “Las Batuecas-Sierra de Francia” and “Quilamas” (Salamanca, Spain)

A new procedure is proposed for joint strategic environmental assessment and environmental impact assessment using simultaneous characterizations in the protected natural area studied to analyse the importance and extent of the impact of human activities within this area on the various natural resources. GIS techniques were used to define territorial models, including environmental information criteria in thematic layers to facilitate environmental diagnosis in the early planning stages in the areas of concern or of higher quality for conservation at different working levels (municipal, district, provincial or national). Traditional conventional environmental impact assessment methods were improved, using spatial analysis to compare scenarios based on the spatial and temporal variability of the impacts identified and their evaluation. This method was applied to the natural space of Las Batuecas-S. de Francia and Quilamas, where in an initial stage the different anthropogenic activities (landfills, etc.) with the potential to cause direct (sewage waters, etc.) or indirect (leachate, etc.) impacts were identified, using checklists and double-entry matrices to analyse actions likely to cause impacts, developing the cartography and identifying environmental impacts potentially damaging to the natural environment. Next, thematic and interpretive mappings were drawn up (surface water quality, aquifer vulnerability to pollution and vulnerability to municipal solid waste) to assess the effects upon resources (water, soil, air, etc.). Finally, by overlapping the impact identification and vulnerability mappings (municipal solid waste, pollution of aquifers and surface water quality) the impact characterization mapping was obtained, showing the absorption capacity of the different sectors to help the responsible bodies set out preventive and/or corrective measures. The essence of this paper is, in methodological terms, its use of two methods simultaneously (strategic environmental assessment and environmental impact assessment) in a protected natural area, allowing it to be extrapolated to any area where territorial management and planning studies need to be carried out.     

Cyclical salt efflorescence weathering: an invisible threat to the recovery of underground mine environment for tourist exploitation

Enhancing the value of an underground mine environment for tourist exploitation involves altering the physico-chemical balance of stone materials whose original mechanical properties guaranteed the structural stability of the site’s galleries and chambers. Humidity and temperature changes caused by the public exhibition of this kind of assets are the main causes of such disorders. After the intervention in the Agrupa-Vicenta mine in La Union (Spain) there were still runoff-water leaks into the mine. These water runoffs through the fault and schistosity planes of the enclosing rock mass give rise to salt precipitation over time. Adapting this mine and turning it into a museum have meant a decrease in relative indoors humidity and an increase in temperature. These variations have caused rocks, which were stable in the original conditions, to increase their rate of physico-chemical weathering due to the polycyclic supergene alteration of the metal sulfides they contain. The resulting release of sulfates into the solution and their subsequent precipitation as single and double salt efflorescence causes haloclasty, deteriorating the rock’s mechanical properties and diminishing the structural stability of the operation. This paper presents the results of characterizing the supergene mineral phases of salt efflorescence in the rock bed enclosing an underground sulfide mine value enhanced for tourist exploitation. Dangers for the structural stability of this type of architectural intervention, associated to the formation of efflorescences, are also identified; these efflorescences are caused by the weathering of rocks that make up its supporting structure.     

Treatment of an ECF bleaching effluent with white-rot fungi in an air-lift bioreactor

Pulp and paper mills utilise huge amount of natural resources, inorganic and organic materials along with large volume of water in different stages of paper manufacturing, resulting in a significant volume of effluents. The aim of this work was to investigate the treatment of a bleaching effluent [effluent chlorine free (ECF)] from the cellulose industry with white-rot fungi in an air-lift bioreactor. This effluent was submitted to the biological treatment with three white-rot fungi, and, every 24 h for 120 h, analytical tests were performed to analyse the quality parameters of treatment (COD, phenols, colour, pH). Before and after treatment, the effluent was analysed as its molecular mass distribution and absorptivity in the UV/VIS. Lentinus edodes, Trametes versicolor and Trametes villosa promoted similarly significant reductions in the following characteristics: (a) effluent colour (40–44 %), (b) total phenol (30–51 %) and (c) COD (37–43 %). The UV/visible spectrometry reading of the effluent after the fungi treatment showed a reduction in the absorbance of all wavelengths between 260 and 500 nm. The size exclusion HPLC profile of the effluent was modified, and the treatment promoted changes in the intensity of the peaks associated with compounds of high and low molecular weight. Phenoloxidases were produced during the treatment. T. versicolor produced the highest levels of laccase, and L. edodes was the only fungus that produced peroxidases.     

Leaching and dilution of fertilizers in the Yucatan karstic aquifer

The application of agrochemicals in crops can cause pollution of aquifers, especially those with a shallow water table and covered by thin soils; such is the case of Yucatan, Mexico. Information about the requirements and application of fertilizers to major irrigation and rainfed crops as well as the volume of water consumed in growing were used to determine the potential amount of nitrate delivered to groundwater. The research reported in this paper was conducted in the metropolitan area of the city of Merida, in Yucatán, Mexico, where groundwater plays an important role since it is the main source of supply, due to the lack of surface water in the region. In addition, the vulnerability of this aquifer is threatened by the various activities taking place in the municipalities, which emphasize agriculture, located within the groundwater basin. This activity is analyzed as a source of contamination given the concentration of NO₃ ^? present in groundwater intended for human consumption. The results show that the contribution of farming that enriches the presence of nitrates in the aquifer is different for each municipality in the study area. For the ZMM, the average nutrient leaching is 44 % of the original mass applied; it could be diluted approximately 12 times, in the groundwater.     

Geoarchaeology of Pleistocene open-air sites in the Vila Nova da Barquinha-Santa Cita area (Lower Tejo River basin, central Portugal)

This paper aims to provide insight into human occupation and landscape change during the Pleistocene in a central area of the Lower Tejo basin (Portugal). Detailed geomorphological mapping, coupled with lithostratigraphy, sedimentology and luminescence dating, supports the identification of a complete terrace staircase sequence. It consists of six gravely terraces located below the culminant (Pliocene) basin unit. A chronological framework for the sedimentary sequences and associated human industries is proposed and correlated with marine oxygen isotope stages (MIS): T1 terrace, not dated; T2, not dated; T3, >300 ka; T4, ∼300-160 ka (MIS8, MIS7 and MIS6); T5, ∼136-75 ka (MIS5); T6, ∼62-30 ka (MIS3); colluvium and aeolian sands, ∼30-14 ka (MIS2); valley fill deposits, ∼14 ka to present (MIS1). The oldest artefacts were found at the base of the T4 terrace, with the local stratigraphic level dated to ≥175 ± 6 ka (Middle Pleistocene). The lithic assemblages collected from distinct stratigraphic levels (T4, T5 top, T6 terraces and colluvium) are characterized by the predominance of opportunistic technological choices, a feature that can be attributed partly to the preferential exploitation of the available raw material, dominated by local-sourced quartzites and quartz pebbles. The adaptation to local raw material (texture and volume), together with subsistence patterns and behaviours, could explain the rarity of Acheulian types (handaxes and cleavers) and picks in the T4 terraces of the Tejo tributaries; this is in contrast to the same terrace of the Tejo valley, in which these types are found. Interpretation of the environmental conditions (controlled by climate and glacio-eustatic sea-level changes) affecting the hunter-gatherer human groups is also presented.     

Overwash vulnerability assessment based on long-term washover evolution

An integrated methodology for evaluation of overwash vulnerability is developed with respect to the historical washover evolution of a barrier island system. Three different aspects of overwash are addressed in the vulnerability indices developed: overwashed shoreline ratio, maximum overwash intrusion recurrence, and complete barrier overwash. The indices were applied to the barriers in the Ria Formosa system in Southern Portugal using an aerial photography catalogue covering the period 1947–2001. Historical trends of washover evolution were observed to be different between the barriers analysed, but generally, there was a decrease in washover number and dimensions throughout the analysed period. The final overwash diagnostic obtained allowed an integrated overwash vulnerability rating to be defined for each barrier, with vulnerabilities ranging from low to extreme. The methodology has produced results that may assist coastal managers with information concerning barrier island system overwash hazard, define the temporal and geographical distributions of overwash, and provide indications as to where overwash is most likely to occur in the future.