Potential application of oxygen-18 and deuterium in mining effluent and acid rock drainage studies

 Oxygen-18 (¹⁸O) and deuterium (D, or ²H) are routinely used in hydrologic, climatologic and geothermal studies. In hydrology, stable isotopes provide information on the type and topology (altitude and latitude) of the recharge waters and the historical effects on water, related to such physical processes as evaporation (in ponds), melting (of snow or ice), condensation, evapotranspiration and mixing. In geothermal studies, stable isotopes provide key information related to recharge and the various temperature-dependent water/rock isotope exchange reactions. The latter is assessed through the oxygen shift in the ¹⁸O/D correlation. At acid rock drainage (ARD) sites, water/rock interactions are primarily controlled by pH and oxidation potential. Using the isotopic characteristics of the rocks and the recharge waters as a basis, the relative oxygen shift of the ARD effluent can provide information on: (1) the residence time, (2) the rate of water/rock reactions, and (3) the actual pH at the rock/water interface. This paper offers a methodology for conducting oxygen and hydrogen isotope studies related to ARD and other mineral effluent problems. The methodology is based on: (1) comprehensive sampling of regional waters, ARD effluent and major contributing minerals and rocks, (2) isotopic and elemental analysis, and (3) data interpretation on the basis of a zero-dimensional (mass balance), multi-component mixing model. Received: 15 January 1999 · Accepted: 3 May 1999     

Hydrochemical and stable isotope assessment of tailings pond leakage, Nickel Plate Mine, British Columbia

Received: 19 April 1999 · Accepted: 19 July 1999     

三江中段新特提斯阶段区域流体的性质与状态

对西南三江地区中段各类脉体开展了系统的流体包裹体和部分稳定同位素成分的研究,探讨新特提斯阶段区域流体状态及对区域成矿条件的影响,研究表明,三江中段新特提斯阶段区域流体存在两个性质不同的流体作用区域,中咱地块以西的兰坪盆地和澜沦江－金沙江构造带主要属于低温流体和域,区域流体以ＮａＣｌ类－Ｈ２Ｏ体民分为特征,中低盐度,流动和沉淀过程中的温度不高于２８０℃,其水体部分主要来自大气敢水的下渗和汇聚,中咱地     

Mid-Holocene stable isotope record of corals from the northern Red Sea

We present a study based on X-ray chronologies and the stable isotopic composition of fossil Porites spp. corals from the northern Gulf of Aqaba (Red Sea) covering the mid-Holocene period from 5750 to 4450 ¹⁴C years BP (before present). The stable oxygen and carbon isotopic compositions of five specimens reveal regular annual periodicities. Compared with modern Porites spp. from the same environment, the average seasonal δ ¹⁸O amplitude of the fossil corals is higher (by ca. 0.35–0.60‰), whereas annual growth rates are lower (by ca. 3.5 to 2 mm/year). This suggests stronger seasonality of sea surface temperatures and increased variability of the oxygen isotopic composition of the sea water due to changes in the precipitation and evaporation regime during the mid-Holocene. Most likely, summer monsoon rains reached the northern end of the Red Sea at that time. Average annual coral growth rates are diminished probably due to an increased input and resuspension of terrestrial debris to the shallow marine environment during more humid conditions. Our results corroborate published reports of paleodata and model simulations suggesting a northward migration of the African monsoon giving rise to increased seasonalities during the mid-Holocene over northeastern Africa and Arabia. Received: 4 January 1999 / Accepted: 13 September 1999     

The Paleocene–Eocene transition in the marginal northeastern Tethys (Kazakhstan and Uzbekistan)

We studied two sections that accumulated during the Paleocene–Eocene transition in shelf waters in the northeastern Tethys. Stable carbon isotopic compositions of marine and terrestrial biomarkers are consistent with a ¹³C depletion in the oceanic and atmospheric carbon dioxide pools during the Late Paleocene Thermal Maximum (LPTM; Subzone P5b). The 2–3‰ negative δ ¹³C excursion in planktic foraminifera coincides with minimum δ ¹⁸O values, an incursion of transient subtropical planktic foraminiferal fauna, and the occurrence of an organic-rich sapropelite unit in Uzbekistan, which accumulated at the onset of a transgressive event. Biomarker distributions and hydrogen indices indicate that marine algae and bacteria were the major organic matter sources. During the Late Paleocene (Subzones P4 and P5a), the marginal northeastern Tethys experienced a temperate to warm climate with wet and arid seasons. Most likely, warm and humid climate initiated during the LPTM (Subzone P5b) and subsequently extended during the Eocene (Zone P6) onto adjacent land areas of the marginal northeastern Tethys. Received: 18 May 1999 / Accepted: 2 February 2000     

Geochemical analyses of air from an ancient debris-covered glacier,Antarctica

We examined air trapped in ancient ice from three shallow cores (<35 m deep) recovered from stagnant portions of the Mullins glacier, an 8 km long debris-covered alpine glacier in the McMurdo Dry Valleys that is overlain by several in-situ volcanic ash-fall deposits. Previously reported ⁴⁰Ar/³⁹Ar dates on ash-fall in the vicinity of the core sites average 4.0 Ma, and underlying ice is presumably as old in some areas. We analyzed the elemental and isotopic composition of O₂, N₂, and Ar and total air content of the glacial ice. We also dated the trapped air directly to an uncertainty of ±220 kyr (1σ) by measuring its ⁴⁰Ar/³⁶Ar and ³⁸Ar/³⁶Ar ratios. Our results suggest that the air analyzed is likely a mixture of ancient atmosphere trapped at the time of ice formation and more recent air introduced via cracks in the ice that penetrate to at least 33 m. The isotopic signatures of gases have been complicated by gas loss, as well as a mixture of thermal and gravitational fractionation. The oldest age estimated for the trapped air dates to 1.6 Ma, indicating that the original air is at least as old as 1.6 ± 0.2 Ma. A convergence to older ice ages with increasing depth in the deepest core analyzed (33 m) hints at the possibility that pristine air might be recovered at greater depths. Minor interstitial debris present in the glacial ice (<1%), along with geochemical evidence for in-situ microbial respiration, prohibit direct analysis of CO₂. We measured the triple isotopic composition of O₂ as a proxy for CO₂ and infer that, in the air represented in our ice samples, CO₂ concentrations are within the range observed over the last 800 ka.     

Trophic scaling of Percichthys trucha (Percichthyidae) in monospecific and multispecific lakes in western Patagonia

Percichthys trucha is a freshwater fish, endemic to southern South America and widely distributed in both, eastern and western sides of the Andes. P. trucha has been described as top native predator in lacustrine ecosystems, experimenting diet shifting during their life history development. Salmonid invasions have impacted their natural ecology through trophic niche interference and predation over alternative high quality prey. This study focuses on populations of P. trucha in western Patagonia, where its trophic ecology have been less understood. We hypothesised a diet shift between juveniles and adults from lower-trophic position prey towards higher-trophic position prey. Fish were collected from 7 lakes belonging to Puelo and Baker river basins, covering a high diversity of environmental conditions. Stomach content and δ¹⁵N stable isotope ratio of muscle tissues of 313 individuals were analysed. Results indicate significant differences in diet between juveniles and adults, shifting from planktonic/benthic preys towards benthic/piscivory, and concomitantly enrichment in heavier nitrogen isotope suggest trophic scaling. No trophic scaling was observed in populations inhabiting lakes with any other fish species present, essentially due to lack of Galaxias sp. as available prey and absence of cannibalism. Despite the fact that P. trucha and Galaxias sp. co-occur in studied river basins, no salmonid-free lakes harbouring this two native species were found, making it difficult to elucidate exact effects of salmonids on trophic scaling of P. trucha. Consumption of aquatic Odonata nymphs, however, arises as one of potential key mechanism for resilience of native food webs to salmonid invasion.     

Trace elements and stable isotope ratios (δC and δN) in fish from deep-waters of the Sulu Sea and the Celebes Sea

Trace elements (TEs) and stable isotope ratios (δ¹⁵N and δ¹³C) were analyzed in fish from deep-water of the Sulu Sea, the Celebes Sea and the Philippine Sea. Concentrations of V and Pb in pelagic fish from the Sulu Sea were higher than those from the Celebes Sea, whereas the opposite trend was observed for δ¹³C. High concentrations of Zn, Cu and Ag were found in non-migrant fish in deep-water, while Rb level was high in fish which migrate up to the epipelagic zone, probably resulting from differences in background levels of these TEs in each water environment or function of adaptation to deep-water by migrant and non-migrant species. Arsenic level in the Sulu Sea fish was positively correlated with δ¹⁵N, indicating biomagnification of arsenic. To our knowledge, this is the first study on relationship between diel vertical migration and TE accumulation in deep-water fish.     

Tracing anthropogenic inputs to production in the Seto Inland Sea, Japan - A stable isotope approach

The Seto Inland Sea (SIS) receives waste runoff from ∼24% of Japan’s total population, yet it is also important in regional fisheries, recreation and commerce. During August 2006 we measured carbon and nitrogen stable isotopes of particulate organic matter (POM) and zooplankton across urban population gradients of the SIS. Results showed a consistent trend of increasing δ¹⁵N in POM and zooplankton from the western to eastern subsystems of the SIS, corresponding to increasing population load. Principal components analysis of environmental variables indicated high positive loadings of δ¹⁵N and δ¹³C with high chlorophyll-a and surface water temperatures, and negative loadings of low salinities related to inputs from large rivers and high urban development in the eastern SIS. Anthropogenic nitrogen was therefore readily integrated into the SIS food web from primary production to copepods, which are a critical food source for many commercially important fishes.     

Climate fluctuations during the Holocene in NW Iberia: High and low latitude linkages

High resolution benthic foraminiferal stable isotopes (δ¹⁸O, δ¹³C) and molecular biomarkers in the sediments are used here to infer rapid climatic changes for the last 8200 years in the Ría de Muros (NW Iberian Margin). Benthic foraminiferal δ¹⁸O and δ¹³C potentially register migrations in the position of the hydrographic front formed between two different intermediate water masses: Eastern North Atlantic Central Water of subpolar origin (ENACW_sp) and subtropical origin (ENACW_st). The molecular biomarkers in the sediment show a strong coupling between continental organic matter inputs and negative δ¹³C values in benthic foraminifera. The rapid centennial and millennial events registered in these records have been compared with two well known North Atlantic Holocene records from the subtropical Atlantic sea surface temperatures (SST) anomalies off Cape Blanc, NW Africa and the subpolar Atlantic (Hematite Stained Grains percentage, subpolar North Atlantic). Comparison supports a strong link between high- and low-latitude climatic perturbations at centennial–millennial time scales during the Holocene. Spectral analyses also points to a pole-to-equator propagation of the so-called 1500 yr cycles. Our results demonstrate that during the Holocene, the NW Iberian Margin has undergone a series of rapid events which are likely triggered at high latitudes in the North Atlantic and are rapidly propagated towards lower latitudes. Conceivably, the propagation of these rapid climatic changes involves a shift in atmospheric and oceanic circulatory systems.