Volcanic ash leaching as a means of tracing the environmental impact of the 2011 Grímsvötn eruption, Iceland.

The Grímsvötn volcanic eruption, from 21 to 28 May, 2011, was the largest eruption of the Grímsvötn Volcanic System since 1873, with a Volcanic Explosivity Index (VEI) of magnitude 4. The main geochemical features of the potential environmental impact of the volcanic ash-water interaction were determined using two different leaching methods as proxies (batch and vertical flow-through column experiments). Ash consists of glass with minor amounts of plagioclase, clinopyroxene, diopside, olivine and iron sulphide; this latter mineral phase is very rare in juvenile ash. Ash grain morphology and size reflect the intense interaction of magma and water during eruption. Batch and column leaching tests in deionised water indicate that Na, K, Ca, Mg, Si, Cl, S and F had the highest potential geochemical fluxes to the environment. Release of various elements from volcanic ash took place immediately through dissolution of soluble salts from the ash surface. Element solubilities of Grímsvötn ash regarding bulk ash composition were <1 %. Combining the element solubilities and the total estimated mass of tephra (7.29 × 10(14) g), the total inputs of environmentally important elements were estimated to be 8.91 × 10(9) g Ca, 7.02 × 10(9) g S, 1.10 × 10(9) g Cl, 9.91 × 10(8) g Mg, 9.91 × 10(8) g Fe and 1.45 × 10(8) g P The potential environmental problems were mainly associated with the release of F (5.19 × 10(9) g).

Contribution of volcanic ashes to the regional geochemical balance: the 2008 eruption of Chaitén volcano, Southern Chile.

The environmental geochemical behaviour of the rhyolitic ashes from the 2008 eruption of Chaitén volcano, Southern Chile, has been studied. After the bulk characterisation, the potential contribution to the regional geochemical fluxes was examined using: i) single batch leaching tests to provide a rapid screening of the implied major and trace elements; and ii) column experiments to evaluate the temporal mobility of leached elements. The environmental concerns of these ashes are related to the fine grained component present in each sample (independent of distance from the source), in particular the presence of cristobalite, and the geochemical hazards posed by ash-water interaction. Leaching experiments show the fast dissolution of surface salts and aerosols, which dominate over glass dissolution during the first steps of the ash-water interaction. Chaitén ashes could transfer to the environment more than 1×10(10)g or 10,000 metric tonnes (mt) of Cl, S, Ca, Na, Si, and K; between 1000 and 10,000 mt of F, Mg, and Al; between 100 and 1000 mt of As, Pb, P, Fe, Sr, Zn, Mn, and Br; between 10 and 100 mt of Ba, Li, Ti, Ni, Nb, Cu, Rb, Zr, V, Mo, Co, and Sc; and less than 10 mt of Cr, Sb, Ce, Ga, Cs, and Y. These results show the fertilising potential of the ashes (e.g., providing Ca and Fe) but also the input of potentially toxic trace elements (e.g., F and As) in the regional geochemical mass balance. The Chaitén results evidence lower potentials for poisoning and fertilising than low silica ashes due to the lower contents released of practically all elements.

Environmental geochemistry of ancient volcanic ashes.

Volcanic ashes from the Puna and surrounding Andean areas in northern Argentina show that sometimes volcanic ash deposits are very well preserved (up to several million years) and can remain a potential hazard for the environment in a similar way as current deposits. Eight ashes have been characterized by SEM-EDX and DRX, and their potential released geochemical fluxes were examined by using water and nitric acid batches, which are analyzed by ICP-OES, ICP-MS and ISE (F). Results demonstrate that water batch system is better medium than nitric acid for this study. The high and fast reactivity of these ancient ashes is mainly associated with their high content in glass. The order of magnitude of released contents of implied elements is consistent among the samples, i.e., Al>B>Fe>Zn>F>P>Mn>Ba>Sr>Li>Ti>Rb>Cu>Ni>Sb>Pb>As>Cr>V. Ash-water interaction, although infrequent in arid regions such as the Puna Region in northern Argentina, introduces rapid changes in the geochemical fluxes of elements and pH and may constitute a potential hazard for the environment. In fact, many of these elements are included in the drinking water guidelines due to their potential toxicity and may constitute potential hazards for the environment and human health.

Spatial and seasonal variations of water quality in a Mediterranean catchment: the Llobregat River (NE Spain).

The Llobregat and Ter Rivers, typical Mediterranean catchments in Northeast Spain, supply water to more than 4.5 million inhabitants residing in the metropolitan area of Barcelona. The objective of this work is to study the factors that influence the surface water quality of Llobregat catchment. As such, spatial and temporal variations of more 50 water chemical parameters were monitored in 10 sampling sites for a period that extended from July 1996 to December 2000. The temperature, pH and conductivity were measured at sites, whereas metals were analysed using ICP-OES and ICP-MS instrumental techniques. The head waters of the Llobregat River catchment flow through detrital Mesozoic-Cenozoic sedimentary rocks resulting in calcium bicarbonate-type water with low mineral content. The high water quality of the waterhead is deteriorated in the upper-middle part of the catchment due to: occurrence of evaporite-bearing geological formations, and the mining and industrial activities related to potash exploitation. As a result, an obvious increase in Na, K, Mg, Cl-, Br, Rb, and Sr concentrations is reported leading to a sodium (potassium) chloride water type. This saline hydrochemical fingerprint persists downstream. This important feature renders the low water quality of the Llobregat River to be adequate for drinking supply purposes. In addition, the industrial and residential activities, specially at the lower part of the catchment, increases P, B, Mn, Fe, Pb, Al, Cr, Co, Ni, Cu, Zn, As and Sb water concentrations.

Strategy for water analysis using ICP-MS.

The developed strategy permits determination in three steps of sixty-seven elements using inductively coupled plasma mass spectrometry (ICP-MS). Sodium, Mg, Si, S, Cl, K, and Ca are determined in a first step; B, Al, P, Cr, Fe, Mn, Ni, Cu, Zn, As, Se, Ag, Cd, Sb, Ba, Hg, and Pb are determined in a second step; and Li, Be, Ti, V, Co, Ga, Ge, Br, Rb, Sr, Y, Zr, Nb, Mo, Sn, Te, I, Cs, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Pt, Au, Tl, Bi, Th, and U are analyzed in a third step. The figures of merit obtained are adequate to carry out water quality monitoring and other hydrochemical studies, such those based in the application of hydrochemical fingerprinting to water management.

Fly ash content and distribution in lake sediments around a large power station: inferences from magnetic susceptibility analysis.

The bulk magnetic susceptibility of sediments from artificial and natural lakes around a large coal-fired power station in NE Spain has been measured. Higher magnetic susceptibility values are found in lake sediments located SE of the power station. This distribution of susceptibility values is compatible with environmental and meterological studies of emissions from the power station, which indicate a dominant SE plume direction. Mineralogical studies, by means of X-ray diffraction and scanning electron microscopy, show that the highest susceptibility values found in the sediments are caused by magnetic iron spinels in the fly ash that is transferred to the environment by the power station particulate emissions. After the quantitative mineralogical studies of fly ash, two different methods of fly ash content determination in the sediments have been devised, showing very similar results. The low background magnetic susceptibility of the sediments in the study area and the high susceptibility resulting from the input of magnetic fly ash particles allows both delimitation of the polluted area around the power station, and quantification of the fly ash input into the natural sediments.