R. Vandelannoote

Relative evaluation of neutron activation, X-ray fluorescence and spark source mass spectrometry for multielement analysis of geothermal waters

To sulfide geothermal waters from the French Pyrenees region and bicarbonate and chloride waters from the French Vosges area, all of the following analysis techniques were applied in order to compose a broad inventory of trace elements: (1) for the dissolved material: neutron activation analysis after a freeze-drying step using a very short cycle (I), short cycle (II) or long cycle (III), neutron activation after co-crystallization on 1-(2-pyridylazo)-2-naphthol (PAN) using a short cycle (IV) or long cycle (V), X-ray fluorescence after co-crystallization on PAN (VI) and spark source mass spectrometry after evaporation on graphite (VII) or preconcentration on PAN, and, (2) for the filtered or suspended material: neutron activation using a very short (VIII), short (IX) or long cycle (X) and X-ray fluorescence (XI). Altogether, on the average some 30 elements could be determined above the detection limit in solution and 15 in suspension. It appeared, however, that for procedures (I), (II), (IV), (VI), (VIII) and (XI) the investment of time and cost had not been efficient enough. Invoking only procedures (III), (V), (IX), (X) and for low salinity geothermal waters only: (VII), the number of elements detected was almost as large.

Analysis of geothermal waters by spark source mass spectrometry

ZusammenfassungDie Analyse von Thermalwasser mittels Funken-Massenspektrometrie ist zwar zeitraubend, sie gestattet aber die Bestimmung von etwa 20 geochemisch interessanten Spurenelementen im ppb-Bereich. Es wird eine physikalische Anreicherung vorgeschlagen, um Elemente mit ganz verschiedenen chemischen Eigenschaften erfassen zu können, z. B. die Alkaligruppe, die Elemente der Übergangsreihe und anionische Verbindungen. Die relativen Empfindlichkeitsfaktoren sind vom Salzgehalt in den Graphitelektroden ziemlich unabhängig. Wegen ihrer gleichmäßigen Elementempfindlichkeit liefert die Funken-Massenspektrometrie Auskunft über den Gehalt von Elementen, die mit Neutronenaktivierung nicht erfaßt werden können, wie z. B. Sn und Pb. Ihre Reproduzierbarkeit ist aber etwa zweimal schlechter.SummaryAlthough the analysis of thermal water by spark-source mass spectrometry (SSMS) is rather timeconsuming, it allows the detection of about 20 elements of geochemical interest down to the ppb-level. A physical preconcentration is proposed in order to collect elements having quite different chemical properties, e.g. alkalis, transition elements, and elements occurring in anionic form. The relative sensitivity factors appear to be rather independent of the salt content of the graphite electrodes. Contrary to neutron activation analysis, SSMS has a quite uniform elemental sensitivity, and allows to determine elements for which neutron activation is not suitable, e.g. Sn and Pb. The precision of SSMS is however by a factor of about 2 worse than that obtained for neutron activation.

Effects of alkaline aluminate waste dumping on seawater chemistry

Abstract The alkaline aluminate waste, of which 1000–2000 tonnes are dumped a few times a year off the Belgian coast in the Southern Bight of the North Sea, contains 5·4% NaCl, 1·8% dissolved Al and 7·4% NaOH, in addition to traces of heavy metals and some aniline- and phenol-derivatives. The pH rises locally to 8-5 and the total Al-concentration reaches 120niglitre −1 (corresponding to an initial waste dilution factor of only 150) in the 10-m wide track just beyond the discharging barge, but these decay quickly to pH 8·1 and 1 mg litre -1 in the 30-m wide track, 500m behind the barge. The relation between the waste concentration and seawater pH was studied. The white precipitate that forms immediately in the sea was identified as Mg 6 Al 2 CO 3 (OH) 16 4H 2 0 (hydrotalcite-manasseite like). No trace of it was found in the local sediments.

Trace-element geochemistry of thermal water percolating through a karstic environment in the region of Saint Ghislain (Belgium)

Abstract Five geothermal waters from the Mons area (southern Belgium) have been studied: one natural hot spring at Stambruges, one stagnant warm water from the “inclined tunnels” at Baudour, and three thermal waters from the drillholes at St. Ghislain, Ghlin and Douvrain, originating from the carbonate/anhydrite-bearing Visean strata, at depths of ca. 2600, 1550 and 1300 m, respectively. Multielement chemical analysis of the filtered water and its suspended matter > 0.4 μ m) was carried out by instrumental neutron activation. Temperature in depth, calculated using the silica (chalcedony) chemical geothermometer, ranged from 75 to 88°C, in good agreement with experimentally determined values. Na/K and Na/K/Ca geothermometers yieilded erratic results, as expected from the geological environment in the aquifer. From the analytical data it can be calculated that the thermal waters of St. Ghislain, Ghlin and Douvrain are not only saturated with respect to chalcedony, but also to anhydrite, calcite, fluorite, barite, strontianite, and possibly zinc silicate, iron (III) hydroxide or siderite, albite, microcline, gibbsite and kaolinite. They are oversaturated with respect to muscovite. Data are also presented for the other thermal waters, and a cold spring water (Claire Fontaine, Stambruges). The similar trace-element composition of the thermal waters can be explained by percolation of the water in the same distant recharge zone, from where it descends, becomes heated at depth and rises along collapse breccia, and locally (Baudour, Stambruges) along fissures. The uptake of higher amounts of Ca, Mg, Sr and sulfate in St. Ghislain and Ghlin, as compared to Douvrain and Baudour is correlated with the boundary between the “non-dissolved” and “dissolved” evaporitic zones. This boundary is situated between St. Ghislain and Douvrain, and is roughly parallel with the direction of the groundwater flow (WNW).

Trace-elemental anomalies in surface water near a small lead-zinc mineralization at Menez-Albot (Brittany, France)

Abstract Sensitive multi-element analysis techniques were applied to water samples collected in the vicinity of a small Zn-Pb-Cu sulfide mineralization in the region of Menez-Albot (Finistere, France). The variation of the trace-element content along a local stream shows the presence of the mineralization, mainly through a simultaneous positive anomaly in solution for a group of about 10 elements (e.g. Ni, Cu, Zn, As, Sb) which are connected with this type of mineralization. The anomaly decreases steeply due to the influx of swamp water rich in Fe, Mn and organic matter. The precipitation barrier is reflected in the stream sediment composition. Contamination from fertilizers was observed in some samples.

Hydrogeochemistry in the zinc—lead mining district of “Les Malines” (Gard, France)

Abstract Sensitive multi-element analysis techniques together with major-element and isotopic analyses were applied to spring, mine and surface waters in the vicinity of an important known zinc—lead deposit in a carbonate environment, in the “Les Malines” area (Gard, France). Both the dissolved and suspended phases were investigated, and concretions and sediments were also considered in some cases. This methodological test shows that the ore body leaves various clear fingerprints, such as the Zn, As, Sb, Pb and U levels in the dissolved phase, the sulfate increment and the δ 34 S. Some of the elements in solution are controlled by slightly soluble compounds, e.g. Zn by smithsonite and hydrozincite, Ba by barite, and Pb by hydrocerussite. Mapping the saturation indices for these elements appears useful for displaying the hydrogeochemical anomaly.

Trace Element Geochemistry in Thermal Waters from Plombieres and Bains (Vosges)

The thermal waters of Plombieres and Bains can be described as mixtures of Sondage Neuf water (Plombieres) and cold water.

Statistical grouping and controlling factors of dissolved trace elements in a surface water system

Abstract Sensitive multi‐element analytical techniques were applied to determine 24 dissolved trace components in 25 different water samples from a 10 km2 zone in Brittany, France. Correspondence factor and multiple regression analyses showed that the elements considered are influenced mainly by the presence of: Fe‐Mn oxide accumulations, a local poly‐metallic sulfide mineralization, and non‐mineralized host rocks, agricultural activity and abundant organic material in local swamps. Via these numerical techniques the location of the poly‐metallic ore body can be derived from the data set.