Designing river water quality policy interventions with scarce data: the case of the Middle Tagus Basin,Spain

ABSTRACT

Anthropic pressures deteriorate river water quality, so authorities need to identify their causes and define corrective actions. Physically based water quality models are a useful tool for addressing physicochemical pollutants, but they must be calibrated with an amount of data that is often unavailable. In this study, we explore the characterization of a model to design corrective interventions in a context of sparse data. A calibration indicator that is both simple and flexible is proposed. This approach is applied to the Middle Tagus Basin in central Spain, where the physicochemical concentration of pollutants is above legal standards. We quantify the effects of the main existing pressures (discharge from wastewater treatment plants, agricultural diffuse pollution and a major inter-basin water transfer) on the receiving waters. In particular, the study finds that wastewater treatment plant effluent concentrations should be reduced to up to 0.65 mg/L of ammonium and 0.55 mg/L of phosphate to achieve the environmental goals. We propose and prioritize a set of policy actions that would contribute to the good status of surface water bodies in the region.     

MAGNÉTOMÈTRE DIFFÉRENTIEL À HAUTE SENSIBILITÉ*

The aim of this article is to describe the double resonance magnetometer system designed and built by the Division de Magnétométrie of the C.E.N. Grenoble, and used by the Département des Recherches Minières du CE.A. For the measurement of magnetic anomalies of geological origin it is necessary to make differential measurements between a mobile instrument which scans the region of interest and a fixed compensatory instrument. The apparatus described here features the following main characteristics: — it gives a direct numerical measurement of the differential magnetic field between the two instruments with an accuracy of 0.01 gamma (10^-7 Oe). — it is designed to be easily operated in geological field work (light weight, low power, possibility to make continuous measurements along a given profile, the measuring signals being radio-linked there are no wires connecting the instruments). Firstly we describe the components of the magnetometer itself namely: double resonance magnetometer heads and differential numerical magnetometer. Secondly we describe the measuring technique.     

Esterase activities in the bivalve mollusc Adamussium colbecki as a biomarker for pollution monitoring in the Antarctic marine environment

Marine environments are continuously being threatened by a large number of xenobiotics from anthropogenic sources. Even in sparsely populated and relatively pristine areas, such as Antarctica, hazardous chemicals can pose a serious environmental problem. The main aims of the present study were to (1) validate and optimize an analytical technique utilizing a microtitre-plate photometer to ascertain background levels of esterase activities in the Antarctic bivalve Adamussium colbecki, (2) carry out in situ monitoring of esterase activities to assess any potential environmental impacts of the Italian Scientific Antarctic Base "Terra Nova Bay" on the surrounding marine area. Results showed the presence of organophosphorous-sensitive cholinesterase (ChE) and carboxylesterase (CbE) activities in the gills of A. colbecki and optimal assay conditions were comparable with those found for bivalve species from temperate areas. A higher sensitivity of ChE versus acetylthiocholine activity in A. colbecki to chlorpyrifos compared to species from temperate areas may also be inferred. The in situ study indicated no differences in the environmental quality of the three study sites located around the Italian Base.     

Groundwater recharge in a sedimentary basin in semi-arid Mexico

Recharge mechanisms and the hydrochemical evolution of groundwater in a semi-arid, 6,840-km², intermountain basin in central Mexico were investigated using stable isotopes and major chemical constituents. Ionic ratio analysis helped to conceptualize and quantify in part the subsequent geochemical evolution in the aquifer system. Mass balance models (PHREEQC) were used to interpret and rectify the geochemical properties of the aquifer. The recharge conditions have not changed noticeably during the last several thousands of years. The recharge mechanisms are accompanied by leaching of meteoric salts on and near the ground surface during major rain events, which previously accumulated after minor rain events. Rapid and diffuse infiltration can be excluded. Indirect infiltration from wadis (arroyos) and depressions (playas) with little mixing in shallow groundwater contrasts with a high degree of mixing for water with deep circulation. The prevailing source of major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) is weathering of carbonates and albite, followed by exchange reactions on clays and hydroxides. Ca²⁺/Na⁺ exchange may interchange along the flow path with reverse (Na⁺/Ca²⁺) exchange, although the Ca²⁺/Na⁺ option is prevalent. Meteoric Ca and Mg inputs are relatively small; however, meteoric Na is insignificant. Irrigation return flow plays an important role in the western part of the study area, giving rise to elevated sulfate and chloride concentrations.

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Resumen Se han investigado los mecanismos de recarga y la evolución hidroquímica de las aguas subterráneas en una cuenca semiárida e intermontanosa de México central, de 6.840 km². Para ello, se han utilizado isótopos estables y los constituyentes químicos mayores. El análisis de las relaciones iónicas ha servido para conceptuar y cuantificar en parte su evolución geoquímica posterior dentro del sistema acuífero. Se ha recurrido a modelos de balance de masas (PHREEQC) para interpretar y rectificar las propiedades geoquímicas del acuífero. Las condiciones de recarga no han cambiado de forma apreciable durante los últimos miles de años. Los mecanismos de recarga se ven acompañados por el lixiviado de las sales meteóricas sobre y cerca de la superficie del terreno durante los episodios principales de lluvia, las cuales son acumuladas en episodios menores de lluvia. Se puede excluir la infiltración rápida y difusa. La infiltración indirecta desde arroyos ( wadis) y depresiones ( playas), que apenas se mezcla con las aguas subterráneas someras, contrasta con un elevado nivel de mezcla con el agua de circulación profunda. La fuente dominante de cationes mayores (calcio, magnesio, sodio, potasio) es la meteorización de los carbonatos y albita, mientras que las reacciones de intercambio en las arcillas e hidróxidos son menos importantes. El intercambio ión calcio-ión sodio puede ser reemplazado a lo largo de una línea de flujo por el intercambio opuesto (ión sodio-ión calcio), aunque la primera es prioritaria. Las aportaciones meteóricas de calcio y magnesio son relativamente pequeñas, mientras que la de sodio es insignificante. Los retornos de riego desempeñan un papel importante en la parte occidental del área de estudio, dando lugar a concentraciones elevadas de sulfato y cloruro.

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Résumé Les mécanismes de recharge et lévolution hydrochimique de leau souterraine dans un bassin de montagne de 6 840 km² en zone semi-aride, dans le centre du Mexique, ont été étudiés au moyen des isotopes stables et des composés chimiques majeurs. Lanalyse des rapports ioniques a aidé à conceptualiser et à quantifier en partie lévolution géochimique qui en résulte, dans le système aquifère. Des modèles de bilan de masse (PHREEQC) ont été utilisés pour interpréter et corriger les propriétés de laquifère. Les conditions de recharge nont pas changé notablement au cours des derniers millénaires. Les mécanismes de recharge sont accompagnés, durant les épisodes majeurs de précipitation, dun lessivage, à la surface du sol et à son voisinage, de sels météoriques accumulés auparavant pendant les petits épisodes de pluie. Linfiltration rapide et diffuse peut être exclue. Linfiltration indirecte à partir des oueds (arroyos) et des dépressions (playas) avec un faible mélange dans la nappe superficielle contraste avec le degré élevé de mélange de leau avec les circulations profondes. La source prépondérante des cations majeurs (Ca²⁺, Mg²⁺, Na⁺, K⁺) est laltération des carbonates et des feldspaths ; léchange de cations avec les argiles et les hydroxydes est moins important. Léchange de Ca²⁺ avec Na⁺ peut sinverser le long des axes découlements pour donner un échange de Na⁺ avec Ca²⁺, bien que le cas Ca²⁺/Na⁺ soit prépondérant. Les apports météoriques de Ca et de Mg sont relativement faibles, cependant que celui de Na météorique est insignifiant. Lécoulement par retour dirrigation joue un rôle important dans la partie occidentale de la région étudiée, produisant un accroissement des concentrations élevées en sulfate et en chlorure.

     

Geochemical evidence for mixing of magmatic fluids with seawater,Nisyros hydrothermal system,Greece

The chemical and isotopic compositions (δD_H2O, δ¹⁸O_H2O, δ¹⁸O_CO2, δ¹³C_CO2, δ³⁴S, and He/N₂ and He/Ar ratios) of fumarolic gases from Nisyros, Greece, indicate that both arc-type magmatic water and local seawater feed the hydrothermal system. Isotopic composition of the deep fluid is estimated to be +4.9±0.5‰ for δ¹⁸O and ?11±5‰ for δD corresponding to a magmatic water fraction of 0.7. Interpretation of the stable water isotopes was based on liquid–vapor separation conditions obtained through gas geothermometry. The H₂–Ar, H₂–N₂, and H₂–H₂O geothermometers suggest reservoir temperatures of 345±15 °C, in agreement with temperatures measured in deep geothermal wells, whereas a vapor/liquid separation temperature of 260±30 °C is indicated by gas equilibria in the H₂O–H₂–CO₂–CO–CH₄ system. The largest magmatic inputs seem to occur below the Stephanos–Polybotes Micros crater, whereas the marginal fumarolic areas of Phlegeton–Polybotes Megalos craters receive a smaller contribution of magmatic gases.     

Influence of object concentration on finite strain and effective viscosity contrast: insights from naturally deformed packstones

Deformed conglomerates and ooidal/oncoidal packstones are commonly used to evaluate finite strain in deformed sedimentary successions. In order to obtain a correct estimate of finite strain, it is necessary to consider not only the different behaviour of matrix and objects, but also object concentration. The analysis of two-component rocks characterised by high values of packing commonly results in a substantial underestimate of bulk strain and of viscosity contrast between objects and matrix. In this study, the effects of the volumetric fraction of competent inclusions on both object and bulk measured finite strain, as well as on apparent viscosity contrast, have been investigated in naturally deformed packstones characterised by variable object concentration on the scale of the hand specimen (and hence for homogenous viscosity contrast). Object finite strain has been obtained by Rf/ analysis, whereas the Fry method provides a measure of whole-rock strain that is also a function of inclusion concentration. Therefore, the finite strain measured by the Fry method is better termed effective bulk strain. In order to investigate the role of object concentration, this parameter has been plotted against object and effective bulk strain, and also against viscosity contrast. These diagrams show that: (i) for high values of packing, measured object and effective bulk strain show values that are significantly lower with respect to the calculated maximum value (that would result in the ideal case of no particle interaction and represents therefore the real bulk strain of the samples); (ii) the viscosity contrast shows lower values with respect to the calculated maximum one (that is equal for the three principal sections of the finite strain ellipsoid), and as packing reaches the maximum value, the viscosity contrast approaches a unit value. Empirical equations have also been found that link object concentration with both object and effective bulk finite strain.     

Observations of physical effects from tsunamis of December 30, 2002 at Stromboli volcano, southern Italy

On December 30, 2002, following an intense period of activity of Stromboli volcano (south Tyrrhenian Sea, Italy), complex mass failures occurred on the northwest slope of the mountain which also involved the underwater portion of the volcanic edifice for a total volume of about 2–3×10⁷ m³. Two main landslides occurred within a time separation of 7 min, and both set tsunami waves in motion that hit the coasts of Stromboli causing injuries to three people and severe damage to buildings and structures. The tsunamis also caused damage on the island of Panarea, some 20 km to the SSE from the source. They were observed all over the Aeolian archipelago, at the island of Ustica to the west, along the northern Sicily coasts to the south as well as along the Tyrrhenian coasts of Calabria to the east and in Campania to the north. This paper presents field observations that were made in the days and weeks immediately following the events. The results of the quantitative investigations undertaken in the most affected places, namely along the coasts of Stromboli and on the island of Panarea, are reported in order to highlight the dynamics of the attacking waves and their impact on the physical environment, on the coastal structures and on the coastal residential zone. In Stromboli, the tsunami waves were most violent along the northern and northeastern coastal belt between Punta Frontone and the village of Scari, with maximum runup heights of about 11 m measured on the beach of Spiaggia Longa. Measured runups were observed to decay rapidly with distance from the source, typical of tsunami waves generated by limited-area sources such as landslides.     

Effect of Overstrength on the Seismic Behaviour of Multi-Storey Regularly Asymmetric Buildings

In past years, seismic response of asymmetric structures has been frequently analysed by means of single-storey models, because of their simplicity and low computational cost. However, it is widely believed that use of more realistic multi-storey models is needed in order to investigate effects of some system characteristics (such as overstrength, higher modes of vibration, etc.) that make behaviour of multi-storey schemes different from that of single-storey systems. This paper examines effects of the overstrength in element cross-sections on the seismic behaviour of multi-storey asymmetric buildings. It is shown that in actual buildings this characteristic, which is sometimes very variable both in plan and along the height of the building, may lead to distributions of ductility demands different from those expected according to the results from single-storey models. Consequently, torsional provisions, which aim at reducing ductility demands of single-storey asymmetric systems to those of the corresponding torsionally balanced systems, should be re-checked in light of the behaviour of realistic multi-storey buildings.     

Human Strategies for Coping with El Niño Related Drought in Amazônia

This article reports on findings of a research project examining farmers' coping strategies in the Brazilian Amazon in response to El Niño related weather events. We examine the extent of vulnerability of small and large farmers to these events in a tropical rainforest environment. Little attention has been given to the impact of ENSO events in Amazônia, despite evidence for devastating fires during ENSOs. Although we found a range of locally developed forecasting techniques and coping mechanisms, farmers have sustained significant losses, and we suggest that increased access to scientific forecasts would greatly enhance the ability of the farmers in our study area to cope with El Niño related weather events. In Amazônia the El Niño phase of the El Niño-Southern Oscillation (ENSO) climate pattern leads to an extended period of reduced rainfall (Hobbs et al., 1998). This period of reduced rainfall can result in significant agricultural losses for farmers and ranchers in the area and in increased forest flammability. We have found that the majority of our study population uses several methods of forecasting, coping with, and adapting to drought events – and they recognize the economic losses they can experience and the loss of forests through the accidental spread of fire. The poorest farmers in our study area experience El Niño related drought events as a serious threat to their livelihoods. Their vulnerability is heightened during extreme climate events and our observations revealed that all of the farmers in our study would benefit from increased availability of improved forecast information relevant to their locality and their current farming strategies. This paper examines the availability and use of forecasts, the occurrence of accidental fires and techniques to prevent fire related losses, and the coping mechanisms for dealing with El Niño related drought in the agricultural regions surrounding the cities of Altamira and Santarém, in Pará State, Brazil. Distribution of an El Niño Prediction Kit at the end of the study and a series of workshops may lead to better local information on rainfall variability and create a farmer-maintained grid of collecting stations to sensitize farmers to the variability of precipitation in the region, and on their property.     

Geochemistry of the Submarine Gaseous Emissions of Panarea (Aeolian Islands, Southern Italy): Magmatic vs. Hydrothermal Origin and Implications for Volcanic Surveillance

The marine sector surrounding Panarea Island (Aeolian Islands, South Italy) is affected by widespread submarine emissions of CO₂ -rich gases and thermal water discharges which have been known since the Roman Age. On November 3^rd, 2002 an anomalous degassing event affected the area, probably in response to a submarine explosion. The concentrations of minor reactive gases (CO, CH₄ and H₂) of samples collected in November and December, 2002 show drastic compositional changes when compared to previous samples collected from the same area in the 1980s. In particular the samples collected after the November 3^rd phenomenon display relative increases in H₂ and CO and a strong decrease in the CH₄ contents, while other gas species show no significant change. The interaction of the original gas with seawater explains the variable contents of CO₂, H₂S, N₂, Ar and He which characterize the different samples, but cannot explain the large variations of CO, CH₄ and H₂ which are instead compatible with changes in the redox, temperature and pressure conditions of the system. Two models, both implying an increasing input of magmatic fluids are compatible with the observed variations of minor reactive species. In the first one, the input of magmatic fluids drives the hydrothermal system towards atypical (more oxidizing) redox conditions, slowly pressurizing the system up to a critical state. In the second one, the hydrothermal system is flashed by the rising high-T volcanic fluid, suddenly released by a magmatic body at depth. The two models have different implications for volcanic surveillance and risk assessment: In the first case, the November 3^rd event may represent both the culmination of a relatively slow process which caused the overpressurization of the hydrothermal system and the beginning of a new phase of quiescence. The possible evolution of the second model is unforeseeable because it is mainly related to the thermal, baric and compositional state of the deep magmatic system that is poorly known.