Izotopska sestava padavin na postaji Portorož, Slovenija – obdobje 2007–2010

The stable isotopic composition of oxygen and hydrogen (δ18O and δ2H) and the tritium activity (A) were monitored in precipitation at synoptic station Portorož (Slovenia) during the period 2007–2010. Monthly and yearly isotope variations are discussed and compared with those observed over the period 2001–2006 and with the basic meteorological parameters. The mean values for δ18O and δ2H, weighted by precipitation, are –6.28 ‰ and –41.6 ‰, and these values are 0.35 ‰ and 1.6 ‰ higher but not significantly different than for the period 2001–2006. The reduced major axis (RMA) local meteoric water line (LMWLRMA) for the period 2007–2010 is δ2H = (8.14 ± 0.25)×δ18O + (8.28 ± 1.64), while the precipitation weighted least square regression (PWLSR) results in LMWLPWLSR δ2H = (7.87 ± 0.28)×δ18O + (7.97 ± 1.87). The deuterium excess (d) weighted mean value is 8.6 ‰ and is 1.2 ‰ lower than in 2001–2006, while the temperature coefficient of δ18O is 0.21 ‰/ºC and is for 0.02 ‰/ºC higher than for the previous period. The mean Mediterranean precipitation index (MI) for the period 2007–2010 is 2.3. Lower values of MI and deuterium excess than in the preceding period indicate stronger continental climatic character during observation period, however the differences are not statistically significant. The weighted mean tritium activity is 6.4 TU, which is 0.5 TU lower but not significantly different than in 2001–2006.V prispevku obravnavamo izotopsko sestavo kisika in vodika (δ18O in δ2H) ter aktivnosti tricija (A) v mesečnih vzorcih padavin, ki smo jo spremljali na sinoptični postaji Portorož (Slovenija) v obdobju 2007–2010. Analizirali smo mesečne in letne spremembe izotopske sestave padavin in jih primerjali z nizom podatkov za obdobje 2001–2006 ter z osnovnimi meteorološkimi parametri. Srednje tehtane vrednosti δ18O in δ2H določene ob upoštevanju izmerjene količine padavin znašajo –6,28 ‰ in –41,6 ‰ in so za 0,35 ‰ oziroma 1,6 ‰ višje kot v obdobju 2001–2006, vendar so razlike statistično neznačilne. Lokalno padavinsko premico (LMWLRMA) za obdobje 2007–2010 zapišemo kot δ2H = (8,14 ± 0,25)×δ18O + (8,28 ± 1,64), ob upoštevanju količine padavin pa kot LMWLPWLSR δ2H = (7,87 ± 0,28)×δ18O + (7,97 ± 1,87). Srednja tehtana vrednost devterijevega presežka (δ) znaša 8,6 ‰ in je za 1,2 ‰ nižja kot v obdobju 2001–2006, medtem ko je temperaturni koeficient za δ18O za 0,02 ‰/°C višji kot v primerjalnem obdobju in znaša 0,21 ‰/°C. Srednja vrednost indeksa mediteranskosti padavin (MI) znaša 2,3. Nižje vrednosti MI in devterijevega presežka nakazujejo v opazovanem obdobju bolj kontinentalni značaj podnebja, vendar so razlike statistično neznačilne. Srednja tehtana vrednost tricijeve aktivnosti znaša 6,4 TU in je za 0,5 TU nižja kot v obdobju 2001–2006, a je tudi ta razlika statistično neznačilna

Concentration and stable carbon isotopic composition of CO2 in cave air of Postojnska jama, Slovenia

Partial pressure of CO2 (pCO2) and its isotopic composition (δ13CairCO2) were measured in Postojnska jama, Slovenia, at 10 locations inside the cave and outside the cave during a one-year period. At all interior locations the pCO2 was higher and δ13CairCO2 lower than in the outside atmosphere. Strong seasonal fluctuations in both parameters were observed at locations deeper in the cave, which are isolated from the cave air circulation. By using a binary mixing model of two sources of CO2, one of them being the atmospheric CO2, we show that the excess of CO2 in the cave air has a δ13C value of -23.3 ± 0.7 ‰, in reasonable agreement with the previously measured soil-CO2 δ13C values. The stable isotope data suggest that soil CO2 is brought to the cave by drip water

Oxygen and clumped isotope fractionation during the formation of Mg calcite via an amorphous precursor

The oxygen and clumped isotope signatures of Mg calcites are routinely used as environmental proxies in a broad range of surroundings, where Mg calcite forms either by classical nucleation or via an amorphous calcium magnesium carbonate (ACMC) precursor. Although the (trans)formation of ACMC to Mg calcite has been identified for an increasing number of settings, the behavior of both isotope proxies throughout this stage is still unexplored. In the present study ACMC (trans)formation experiments were carried out at constant pH (8.30 ± 0.03) and temperature (25.00 ± 0.03 °C) to yield high Mg calcite (up to 20 mol% Mg). The experimental data indicate that the oxygen isotope values of the amorphous and/or crystalline precipitate (δ$^{18}$O$_{prec}$, analyzed as Mg calcite) are affected by the (trans)formation pathway, whereas clumped isotopes (Δ$_{47prec}$ = Δ$_{47Mg-calcite}$) are not. The oxygen isotope evolution of the solid phase can be explained by the instantaneous trapping of the isotopic composition of the aqueous (bi)carbonate complexes. This entrapment results in remarkably high 10$^{3}$ln(α$_{prec-H2O}$) values of ∼33‰ at the initial ACMC formation stage. During the ACMC transformation process the oxygen isotope equilibrium is approached rapidly between Mg calcite and water (Δ$^{18}$O$_{Mg calcite-water}$ = 30.3 ± 0.4‰) and no isotopic memory of the initial to the final Mg calcite at the end of the experiment occurs. The implications for oxygen and clumped isotope signatures of Mg calcite formed via ACMC are discussed in the aspects of various scenarios of (trans)formation conditions and their use as environmental proxies

Sulfate attack - Reaction mechanisms revealed by a multi proxy approach

The destructive effects of sulfate attack on concrete structures are well known, but the reaction paths and mechanisms that cause the deterioration are still under debate. The aim of this study is to contribute to a deeper understanding on investigating concrete damage by introducing a novel and promising multi proxy approach method. The methodology comprises advanced mineralogical and hydro-geochemical methods as well as stable isotope signals. Investigations were performed on various field case studies in Austria, where the locally occurring ground water was classified as slightly aggressive to concrete, in accordance to DIN EN 206-1. Nevertheless intense concrete damage related to sulfate attack was found. Severely damaged mushy concrete consisted mainly of thaumasite, secondary calcite, gypsum and relicts of aggregate. The expressed interstitial solutions from such material were extremely enriched in SO4 (up to >30000 mg L-1). Stable hydrogen and oxygen isotope were applied successfully and demonstrated that the degree of evaporation provoked enrichments in SO4 and other dissolved, potentially harmful ions such as Cl. Furthermore, the enormous accumulation of incompatible trace elements (e.g. Rb and Li) clearly indicated that numerous wetting and drying cycles had occurred. Such a highly dynamic system is known to induce severe destructive effects on concrete. In this study we demonstrate that the application of a multi proxy approach can provide a better understanding of the complexity of reaction mechanisms involving sulfate attack on concrete structures. More detailed knowledge on the individual reactions that promote concrete damage in field structures will help to find specific counter measures for already affected buildings and to develop tailored concrete recipes, applications and constructive measures for future projects

Fracture dolomite as an archive of continental palaeo-environmental conditions

The origin of Quaternary dolomites in continental environments (e.g. karst and lakes) is barely constrained compared to marine dolomites in sedimentary records. Here we present a study of dolomite and aragonite formations infilling young fractures of the ‘Erzberg’ iron ore deposit, Austria, under continental-meteoric and low temperature conditions. Two dolomite generations formed shortly after the Last Glacial Maximum (~20 kyr BP): dolomite spheroids and matrix dolomite. Clumped isotope measurements and U/Th disequilibrium ages reveal formation temperatures of 0–3 °C (±6 °C) and 3–20 °C (±5 °C) for the both dolomite types, and depositional ages around 19.21 ± 0.10 kyr BP and 13.97 ± 0.08 kyr BP or younger, respectively. Meteoric solution and carbonate isotope compositions (δ18O, δ13C and 87Sr/86Sr) indicate the dolomites formed via aragonite and high-Mg calcite precursors from CO2-degassed, Mg-rich solutions. Our study introduces low temperature dolomite formations and their application as a sedimentary-chemical archive.ISSN:2662-443

Interaction of hyperalgesia and sensory loss in complex regional pain syndrome type I (CRPS I)

Sensory abnormalities are a key feature of Complex Regional Pain Syndrome (CRPS). In order to characterise these changes in patients suffering from acute or chronic CRPS I, we used Quantitative Sensory Testing (QST) in comparison to an age and gender matched control group