Spring geochemistry in an active volcanic environment (São Miguel, Azores): source and fluxes of inorganic solutes

Mineral waters were monthly sampled in selected springs from Furnas and Fogo trachytic central volcanoes (São Miguel, Azores, Portugal). Water temperatures between 15.1 °C and 90.2 °C, characterize poorly mineralized waters of Na-HCO₃ and Na-HCO₃-Cl types. According to the spring location, two watersheds were selected in each volcano to evaluate solute fluxes and chemical weathering rates (Fogo volcano: Ribeira Grande river - RRG; Furnas volcano: Ribeira Quente river - RRQ). Na, Mg, K and Ca fluxes in groundwater represented 43%, 60%, 46% and 57% of the total (subsurface plus surface fluxes) in RRG, and respectively 43%, 53%, 46% and 49% in RRQ. Average HCO₃ flux is ten times higher in RRQ (130.1 × 10(6) mol/yr) compared to RRG (13.8 × 10(6) mol/yr), reflecting the volcano degassing and the lower ratio between groundwater and river water fluxes. Based on these values, total CO₂-consumption by weathering ranged from 1.5 × 10(6)mol/km(2)/yr (RRG) to 4 × 10(6)mol/km(2)/yr (RRQ). TDS load varied between 3772 t/yr (RRG) and 15388 t/yr (RRQ), and the ratio between values in groundwater and in surface water is respectively equal to 0.72 and 2.04. The associated chemical weathering rates in groundwater were 206 t/km(2)/yr (RRG) and 399 t/km(2)/yr (RRQ). Coupled to river water, these values indicate that total chemical weathering rates are respectively equal to 493 t/km(2)/yr and 594 t/km(2)/yr. A similar approach developed for the entire archipelago showed that the chemical weathering rates due to groundwater are in the range from 33 to 321 t/km(2)/yr, being partially controlled by the age of the islands. Results of the present study point out to the need to consider groundwater solute fluxes due to weathering when establishing geochemical budgets.

Fluvial geochemistry in São Miguel Island (Azores, Portugal): source and fluxes of inorganic solutes in an active volcanic environment

River water chemistry in two of the major rivers in São Miguel Island (Azores archipelago, Portugal) has been characterized monthly between June 2010 and October 2011 in order to estimate the main geochemical processes that explain water composition and to estimate solute fluxes and the thermal water input to rivers. Both rivers (Ribeira Grande - RRG, and Ribeira Quente - RRQ) drain active trachytic central volcanoes. The number of sampling stations is seven in RRG and six in RRQ. Rivers are mainly slightly acid to basic in nature (pH in the range 5.41-8.70 in RRG and 5.90-8.10 in RRQ) and from the Na-HCO3 and Na-HCO3-Cl water types. In both cases water temperature increases towards the river mouth and median values are slightly higher in Ribeira Quente (15.5-22.4°C) comparing to Ribeira Grande river (15.2-19.7°C). Electrical conductivity suggests poorly mineralized waters (139-456 μS/cm in RRG and 209-402 μS/cm in RRQ, and values increase downstream. Higher solute fluxes are associated to HCO3 and Na, and the total CO2 flux is equal to 3647 t/yr in RRQ and 7546 t/yr in RRG. Mixture with thermal water discharges also influences river water chemistry and in RRQ the contribution to the annual average discharge rate was estimated in 2.96×10(6)m(3)/yr (12.8% of overall discharge rate in the watershed). In RRG thermal water discharges were estimated in 2.4×10(6)m(3)/yr (14.9% of the discharge rate). The minimum total CO2-consumption associated with low-temperature weathering is equal to 0.58×10(6)mol/km(2)/yr in Ribeira Quente river and equal to 0.78×10(6)mol/km(2)/yr in Ribeira Grande river.

Especificaciones de cálculo de la vida útil y estado límite de corrosión

RESUMENLos cálculos de vida útil de las estructuras de hormigón están pasando rápidamente de los laboratorios a las normativas y a ser especificados en la licitación de grandes infraestructuras. Así vidas útiles de 100 años o más se han requerido en puentes como Oresund o en el nuevo canal de Panamá. Sin embargo la especificación se realiza de forma resumida sin que se defina la forma de demostrar esa durabilidad y en algunos casos, sin siquiera mencionar los ensayos y sus valores limites que se deben utilizar. En la presente comunicación se describen los aspectos más importantes que se deben especificar en los modelos que deben ser además de los coeficientes de difusión, la concentración superficial, los factores de envejecimiento y el límite de cloruros así como la probabilidad de corrosión que se considera inaceptable.Palabras Clave: hormigón; cloruros; resistividad; difusión.ABSTRACTEstimates of service life of concrete structures are rapidly moving from laboratories to the standards and to be specified in the construction for large infrastructures. So service life of 100 years or more were required to Oresund bridge or the new Panama Canal. However, the specification is made without defining how to prove the specified durability and in some cases, without even mentioning the tests and limit values to be used. Present communication describes the most important aspects to be specified in the chloride prediction models in addition to the diffusion coefficients, which are the surface concentration, the aging factor, the limit of chlorides and the acceptable probability of corrosion.Keywords: concrete; chlorides; resistivity; diffusion.

Improving the selection of focal species exposed to pesticides to support ecological risk assessments

Risk assessment investigates the potential impacts of chemicals on non-target organisms. To assess the risk, ecotoxicologists study the responses of a panel of species to different substance exposure. Among the different parameters used to select indicator species (i.e. focal species), their frequency of occurrence is considered as the key parameter. Although species occurrence within a given habitat is easy to determine, we argue that it does not totally reflect the dependence of a species on a given habitat or its potential exposure to chemicals. In this study, we combined the occurrence of species with their habitat-specificity to identify focal species for risk assessment in cereals. We showed that ranking species by occurrence or by habitat-specificity produced different results, with generalist species ranking high in the occurrence list, and species with specialised habitats ranking high in the abundance list. Integrating frequency and abundance of species into one single indicator (the "Indicator Value") allows us to rank species with specialised habitats as high as generalist species in the top rank species list. Although habitat-specificity is an ecologically meaningful concept, it is largely overlooked in eco-toxicological risk assessment, despite the fact that specialists are good indicators of various environmental pressures. This method could be used extensively at different scales and could contribute to studies on risk assessment issue by (re)introducing ecological and population-level concepts and opening up new trait-based approaches.

Injuries in preschool children: the hypothetical protector effect of minor injuries and risk factors for minor and medically attended injuries

This study aimed to investigate the relationship between minor and medically attended injuries and to analyse the influence of child-related factors and family-related factors in injuries of preschool children. Individual interviews were conducted with 335 parents of 1- to 5-year-old children. Parents informed about the child and the family variables and reported the child's history of injuries in the last year. The frequencies of minor injuries and medically attended injuries were not correlated. The risk factors for both kinds of injuries include the number of siblings and the size of the family. Minor injuries were more frequent in older than in younger children. Medically attended injuries were more frequent in boys than in girls. The risk factors that influence minor and medically attended injuries are different, suggesting that the strategies to prevent and reduce injuries need to take that difference into consideration.