Rui Coutinho

Health hazards and disaster potential of ground gas emissions at Furnas volcano, São Miguel, Azores

A health hazard assessment of exposure to soil gases (carbon dioxide and radon) was undertaken in the village of Furnas, located in the caldera of an active volcano. A soil survey to map the area of soil gas flow was undertaken, gas emissions were monitored at fumaroles and in eight houses, and a preliminary radon survey of 23 houses in the main anomaly area was performed. Potential volcanic sources of toxic contamination of air, food, and water were also investigated, and ambient air quality was evaluated. About one-third (41 ha) of the houses were located in areas of elevated carbon dioxide soil degassing. Unventilated, confined spaces in some houses contained levels of carbon dioxide which could cause asphyxiation. Mean indoor radon levels exceeded UK and US action levels in the winter months. A tenfold increase in radon levels in one house over 2 h indicated that large and potentially lethal surges of carbon dioxide could occur without warning. Toxic exposures from the gaseous emissions and from contamination of soil and water were minimal, but sulphur dioxide levels were mildly elevated close to fumaroles. In contrast, evidence of dental fluorosis was manifested in the population of the nearby fishing village of Ribeira Quente where drinking water in the past had contained elevated levels of fluoride. The disaster potential of volcanic carbon dioxide in the area could also be associated with the hydrothermal system storing dissolved carbon dioxide beneath the village. Felt, or unfelt, seismic activity, or magma unrest, especially with a reawakening of explosive volcanic activity (30% probability in the next 100 years) could result in an increase in gas flow or even a gas burst from the hydrothermal system. A survey of all houses in Furnas is advised as structural measures to prevent the ingress of soil gases, including radon, were needed in some of the study houses. Evaluations of the human hazards of volcanic gases should be undertaken in all settlements in volcanic and hydrothermal areas associated with soil gas emissions.

Chemistry of waters from Furnas volcano, São Miguel, Azores: fluxes of volcanic carbon dioxide and leached material

Abstract The well-constrained hydrology of the Furnas caldera permits the quantification of the precipitation, evapotranspiration, runoff and the groundwater discharge out of the volcanic structure. Chemical composition of the discharge in Furnas has been stable for at least a century. A hydrogeochemical survey and discharge measurement of the springs and runoff in Furnas allow estimates of chemical fluxes from the volcanic structure. A tectonically controlled lineament of high carbon dioxide flux has been identified across the caldera floor. Three water types are encountered in Furnas: hydrothermal, carbonated and cold waters. The hydrothermal waters originate from shallow aquifers which derive their heat from local intrusions at shallow depth (100–200 m) at about 160°C. The carbonated waters, some of which are steam heated by discharge from underlying thermal aquifers occurs above the carbon dioxide anomaly across the caldera floor. Extensive leaching, in some cases stoichiometric, of glassy volcanic rocks by these mildly acid carbonated waters supplies most of the dissolved solids in Furnas waters. Chemical flux estimates for the volcano show that carbon dioxide (9358 tons/yr), leached silica (3994 tons/yr) and leached sodium (2628 tons/yr) are the dominating mobile components of the system.

Magma-derived CO2 emissions recorded in 14C and 13C content of plants growing in Furnas caldera, Azores

Abstract The environmental impact of fumarolic and soil emanations of magma-derived carbon dioxide across Furnas caldera has been investigated by measuring the 14 C and 13 C content of 40 specimens of different C3 plants (leaves) growing within and outside the degassing areas. The results demonstrate a significant to large 14 C depletion in many of the plants due to assimilation of 14 C -free endogenous CO2 during photosynthesis and leading to artificial radiocarbon ageing of up to 4400 years. The extent of 14 C ageing broadly correlates with the intensity of gas manifestations at the sampling sites, as inferred from field observations and measurements of excess CO2 concentrations in the volcanic ground. It also provides a time-integrated measure of the amount of volcanic CO2 locally admixed to the ambient air; at several sites this accounts for 15 to 40% of total CO2 (420 to 600 ppm) in enriched air. In some of the plant species (Azalea, Camellia and fern) 14 C depletion is correlated with an enrichment of 13 C due to assimilation of magma-derived CO2 with a 4‰ higher δ 13 C than normal atmosphere. The rate of 13 C enrichment averages ca. 0.18‰ by percent of volcanic carbon fixed in the plant and includes enhanced 13 C discrimination during photosynthesis as a consequence of increased ambient pCO2 (inferred at −0.0306‰ per added ppm of volcanic CO2). Furnas is one of the few volcanoes where clear 13 C enrichment in plants due to endogenous degassing has been evidenced. Our results can be used to estimate the local intensity of volcanic soil gas fluxes in the emanating areas of Furnas caldera. They also have implications for radiocarbon dating of past eruptive events in the caldera, since plants artificially aged by previous degassing could be trapped in volcanic deposits.

Chemical monitoring of river water bodies in an EU outermost region: examples from the Azores archipelago (Portugal)

Chemical monitoring of water quality on a total of 16 rivers in the Azores archipelago (Portugal), since 2003, made it possible to identify the major pressures and spatial geochemical variations along main course of the rivers. River water pollution is to a large extent associated to point sources, namely domestic wastewater discharges, especially in urban areas, and diffuse sources, associated with pasture land, and explain the high values on BOD(5) and nutrients (P and N). Heavy metals and metalloids, as well as hydrocarbons and pesticides, are generally under the detection limits of the analytical methods. Generally, river water reflects pollution loads according to a simple model, derived from land use in the watershed: in the upper part conditions are pristine, in the intermediate portion of the basin pasture land dominates and near the coast urban discharges are increasingly important. Results stress the role that an approach based on the watershed scale, coupled with land use management measures, are crucial to water management procedures and a successful WFD implementation in small river basin districts like the Azores. The paper also shows the need for full compliance regarding EU directives on urban wastewater and nitrate pollution due to agriculture.

Human adjustments and social vulnerability to volcanic hazards: the case of Furnas Volcano, São Miguel, Açores

Abstract Following a review of recent developments by social theorists, concerned with the policy and practice of natural hazard reduction it is argued that neither the so-called dominant nor the radical perspectives, are sufficient on their own to answer the questions now being addressed by applied volcanologists during the International Decade for Natural Disaster Reduction. In order to make useful recommendations to policy-makers, which are both reliable assessments of eruption risk and at the same time sensitive to probable interactions of future eruptions with the physical environment of the study region and its peoples, a conflation of traditional hazard analysis and vulnerability analysis is required. This view is tested by means of a case study of evacuation planning at Furnas Volcano in the Açores. As well as supporting the argument from theory, this example leads to the proposition that research on evacuation planning and civil defence should proceed in an ordered sequence. First hazard analysis (i.e. hazard mapping) should be carried out in the traditional manner. Next possible interactions with the physical environment should be specified and a preliminary plan of evacuation routes drawn up. Before detailed recommendations about the logistics of evacuation are made, however, it is vital that such factors as the demographic, socio/economic and cultural/behavioural characteristics of the population at risk are fully considered.

Communicating information on eruptions and their impacts from the earliest times until the late twentieth century

Volcanoes hold a fascination for human beings and, before they were recorded by literate observers, eruptions were portrayed in art, were recalled in legend and became incorporated into religious practices: being viewed as agents of punishment, bounty or intimidation depending upon their state of activity and the culture involved. In the Middle East the earliest record dates from the third millennium BCE and knowledge of volcanoes increased progressively over time. In the first century CE written records noted nine volcanoes in the Mediterranean region plus Mount Cameroon in West Africa, yet by 1380 AD the record only totalled 48, with volcanoes in Japan, Indonesia and Iceland being added. After this the list of continued to increase, but important regions such as New Zealand and Hawaii were only added during the last 200 years. Only from 1900 did the rate of growth decline significantly, but it is sobering to recall that in the twentieth century major eruptions have occurred from volcanoes that were considered inactive or extinct, examples including: Mount Lamington—Papua New Guinea, 1951; Mount Arenal—Costa Rica, 1968 and Nyos—Cameroon, 1986. Although there were instances where the human impact of historical eruptions were studied in detail, with examples including the 1883 eruption of Krakatau and 1943–1952 eruption of Paricutin, these were exceptions and before 1980 there was a significant knowledge gap about both the short and long-term effects of major eruptions on societies. Following a global review, this chapter provides a discussion of the ways in which information has been collected, compiled and disseminated from the earliest times until the 1980s in two case study areas: the Azores Islands (Portugal) and southern Italy. In Italy information on eruptions stretches back to prehistoric times and has become progressively better known over more than 2,000 years, yet even here there remain significant gaps in the record even for events that took place between 1900 and 1990. In contrast, located in the middle of the Atlantic, the Azores have been isolated for much of their history and illustrate the difficulties involved in using indigenous sources to compile, not only assessments of impact, but also at a more basic level a complete list of historical events with accurate dates.

Chapter 16 Volcanic hazard vulnerability on São Miguel Island, Azores

Abstract In recent years much progress has been made in researching a wide variety of extreme events on São Miguel. In addition there are a number of volcano-related risks that impact upon the people of São Miguel. Some of these may occur both before and during volcanic emergencies (e.g. earthquakes), whilst others render São Miguel dangerous even when its volcanoes are not erupting (e.g. flooding, landslides, tsunamis and health impacts, especially the effects of CO2 seepage into dwellings). In this chapter we first define what vulnerability means to the people of São Miguel, and relate this to the cultural and economic characteristics of the island. The following aspects of vulnerability are discussed: (a) physical (i.e. housing, settlement and the characteristics of evacuation routes and plans); (b) demographic and economic; and (c) social and cultural and perceptual (i.e. whether people have an accurate cognition of risk). Particular areas of concern relate to housing: the identification of isolated dwellings that would be difficult to evacuate; the vulnerability/resilience of evacuation routes following recent infrastructure improvements; characteristics of the islands transient population; management of livestock under emergency conditions; local leadership roles; and educational outreach.

Chapter 21 Hydrogeology of São Miguel Island, Azores: a review

Abstract Groundwater is the main source of water supply on São Miguel. Groundwater abstraction (25 hm3 a−1) relies almost exclusively on springs discharging from perched aquifers. A total of 1100 springs (1.5 springs/km2) are located on São Miguel, mainly in the Água de Pau and the Furnas–Povoação groundwater bodies. Only 26 wells have been drilled, distributed principally in the west-central zone. Specific capacity ranges between 0.49 and 100 l (s m)−1 (median=1.11 l (s m)−1), while transmissivity ranges between 5.98×10−4 and 1.22×10−1 m2 s−1 (median=1.35×10−3 m2 s−1). Groundwater is predominantly of the Na-Cl and Na-HCO3 types and electrical conductivity in springs ranges from 36 to 440 μS cm−1 (median=152 μS cm−1), which is lower than in wells (211–9670 μS cm−1; median=515 μS cm−1). These values result from seawater spray, a CO2 soil contribution and limited dissolution of primary silicate minerals from volcanic rocks. In the case of wells, seawater intrusion may also influence electrical conductivity. One of the main problems in groundwater quality is total and faecal coliform microbial contamination. A pollution risk map constructed for São Miguel as a whole showed that risk in the majority of the groundwater bodies is only very low to moderate.

Chapter 19 Hydrogeochemical characterization of mineral waters in São Miguel Island, Azores

Abstract A dataset on the chemical composition of mineral water discharges from São Miguel, 76 samples, depicts a large variability of chemical types and dissolved solids content. The distribution of the discharges shows an association with the three active Quaternary central volcanoes that dominate the geology of São Miguel, namely Furnas, Fogo and Sete Cidades, 74% of which are springs, 13% fumaroles, 12% wells and 1% hand-dug wells. Total dissolved solids (TDS) values are in the range of 159–20 957 mg l−1, discharge temperature varies from 15 to 99.5°C and waters are mainly strongly acid to slightly alkaline (pH ranging between 2.2 and 7.71). Springs discharge mainly from perched-water bodies, corresponding to Na-HCO3 and Na-HCO3-Cl-type waters, with a composition influenced by absorption of CO2 and mixing between meteoric water and boiling waters with a hydrothermal component. Instead the majority of the wells are distributed along the coast and depict chloride enrichment owing to mixture with seawater. The lower pH values are associated with boiling pools at Fogo Volcano with a SO4-dominated chemistry, resulting from steam-heating of shallow perched-water bodies.