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Stable carbon isotope signatures of methane from a Finnish subarctic wetland  [cached]
S. Sriskantharajah,R. E. Fisher,D. Lowry,T. Aalto
Tellus B , 2012, DOI: 10.3402/tellusb.v64i0.18818
Abstract: Methane emissions from Lompoloj nkk , a Finnish aapa mire within the Arctic Circle, were studied by non-intrusive Keeling plot methods, to place better constraints on the seasonal variations in isotopic signature of methane (δ13CCH4) emitted from Arctic wetland. Air samples were collected in Tedlar bags over the wetland at heights of 42 and 280 cm between May and October 2009 and in August 2008. The mixing ratio and δ13C of the methane in the samples were incorporated into Keeling plot analyses to derive bulk δ13CCH4 signatures for the methane inputs to the air above the wetland. The results show an unexpected consistence in δ13CCH4 from early to late summer, clustered around 68.5±0.7‰, but during spring thaw and autumnal freezing, δ13CCH4 is enriched by approximately 2 and 4‰, respectively. The techniques reported in this paper are simple and economical to employ, and give a bulk source signature for the methane inputs to the air above the entire wetland that can be extrapolated to a larger regional area.
Application of Multivariate Statistic of U, Th and Pb Concentrations and Pb Isotopic Signatures in the Assessment of Geogenic and Anthropogenic Sources in a U-Mineralized Area  [PDF]
Adriana Monica Dalla Vecchia, Jorge Carvalho de Lena, Ana Claudia Queiroz Ladeira
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.76001
Abstract:
This work presents a Principal Component Analysis (PCA) study using Pbisotope signatures and U, Th and Pb concentrations from groundwater, sediments and rocks (granites and orthogneisses) of the Complex of Lagoa Real (Bahia, Brazil). This area is naturally enriched in U and Th, with the occurrence of Pb derived from the radioactive decay of the elements (238U, 235U and 232Th) in the form of their stable isotopes 206Pb, 207Pb and 208Pb in addition to the natural isotope 204Pb. Sampling was carried out in the rainy season (December to January) and the points were selected according to regional hydrology and geology. Thirty samples were analyzed: 12 of groundwater (AP) and 18 of sediments (S). The results show that the use of isotopic ratios allows discrimination between geogenic and anthropogenic samples. This information is not obtained using only the analysis of concentration data. Statistically, the isotopic data of Pb stand out as an efficient tool in the characterization of sources in the scenario investigated, allowing an effective environmental monitoring and a better management of the mining activities.
Eco-hydrological model and critical conditions of hydrology of the wetland of Erdos Larus Relictus Nature Reserve

Fang Wang,Lili Liang,Yinsun Zhang,Runhong Gao,

生态学报 , 2009,
Abstract: Erdos Larus Relictus Nature Reserve is the only wetland of international importance to protect Larus Relictus in China. From the early part of this century, the impact of water use, vegetation construction and the climate of the catchment area increasing on the wetland of this Nature Reserve has brought about severe water shortage. Until now, no eco-hydrological model at home or abroad integrates the wetland ecological and hydrological processes. This paper considers the relationship between the food chains of the Larus Relictus and environmental elements, and establishes the eco-hydrological processes from Larus Relictus to damselfly + Chironomidae and the salinity and the area of Bojiang Lake. It also establishes a relationship among Larus Relictus breeding, the area of islands outcropped in the levels of the lake and hydrological season based on the relationship between Larus Relictus breeding and environmental elements. The eco-hydrological model is then constructed according to these relationships. In virtue of the constraints of the lake salinity, the suitable area of the lake is 9.01 km2, and 4.88 km2 for the smallest area. While in accordance with the area of islands outcropped needed for Larus Relictus breeding, the lake area is 11.02 km2 in breeding season corresponding to critical high level.
The influence of peat volume change and vegetation on the hydrology of a kettle-hole wetland in Southern Ontario, Canada
P. Whittington,M. Strack,R. van Haarlem,S. Kaufman
Mires and Peat , 2007,
Abstract: Links between local hydrology and vegetation type exist in wetlands, yet it is unclear what role peat volume change plays in these interactions. We measured peat volume change and hydraulic conductivity (Kfield) at three contrasting sites located on the quaking vegetation mat of a kettle-hole peatland in southern Ontario. The three sites had visibly different plant communities and were named, according to their dominant vegetation, Sedge (Carex spp.), Typha (Typha angustifolia) and Carr (Cornus stolonifera). Peat was also collected for laboratory studies of peat volume change, vertical (Kv) and horizontal (Kh) hydraulic conductivity and the effect of compression on hydraulic conductivity (Kc).In the field, the water table rose throughout the study period, resulting in swelling of the peat. Peat volume change above the -100 cm layer was 11.2%, 6.0% and 3.8% at the Sedge, Typha, and Carr sites respectively. In laboratory samples, a falling water table caused compression of the peat below the structured surface mat, and relative peat volume change between the sites followed the same pattern as in the field. Kfield, Kv and Kh generally decreased with depth from ca. 10-2 to 10-6 cm s-1. In the surface layers (0 to -50cm) K trended Carr>Typha>Sedge, whereas the reverse trend was observed in deeper peat. Artificial compression affected K only in the uppermost layers (0 to -15cm). The decline in Kc with compression also trended Sedge>Typha>Carr. Differences in peat volume change and K are probably related to differences in vegetation and soil structure, and may be important for maintaining suitable growing conditions within each community.
Pyrolysis of oil at high temperatures: Gas potentials, chemical and carbon isotopic signatures
Hui Tian,XianMing Xiao,LiGuo Yang,ZhongYao Xiao,LiGuo Guo,JiaGui Shen,YuHong Lu
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0590-0
Abstract: Although the gas cracked from oil has been believed to be one of the important sources in highly matured marine basins, there are still some debates on its resource potentials and chemical and isotopic compositions. In this study a Cambrian-sourced marine oil sample from the Silurian reservoir of well TZ62 in the central Tarim basin was pyrolyzed using sealed gold tubes with two different pyrolysis schemes: continuous pyrolysis in a closed system and stepwise semi-open pyrolysis. The results show that the maximum weight yield of C1–5 gases occurs at EasyRo=2.3% and the residual gas potential after this maturity is only 43.4 mL/g, about 12% of the yield of 361 mL/g at EasyRo=2.3%. Combined with the results of kinetic modeling, the main stage of gas generation from oil cracking is believed within the EasyRo=1.6%–2.3%. The increase in the volume yield of C1–5 gases at EasyRo>2.3% in a closed system is mainly related to the re-cracking of previously formed C2–5 wet gases, not the direct cracking of oil. The stepwise pyrolysis experiments show that the gas from the cracking of residual oil at EasyRo>2.3% is characterized by very high dryness index (higher than 92%) and heavy methane carbon isotopes ranging from 28.7% to 26.7%, which is quite different from the gases from the continuous pyrolysis in a closed system. The kinetic modeling of methane carbon isotope fractionation shows that the carbon isotopes of methane within the main stage of gas generation (EasyRo<2.3%) are far lighter than the carbon isotopes of the precursor oils under a geological heating rate of 2 °C/Ma. The above observations and results provide some new clues to the accurate recognition and objective resource evaluation of oil cracking gas in highly mature marine basins.
Emission ratio and isotopic signatures of molecular hydrogen emissions from tropical biomass burning  [PDF]
F. A. Haumann,A. M. Batenburg,G. Pieterse,C. Gerbig
Atmospheric Chemistry and Physics Discussions , 2013, DOI: 10.5194/acpd-13-11213-2013
Abstract: In this study, we identify a biomass-burning signal in molecular hydrogen (H2) over the Amazonian tropical rainforest. To quantify this signal, we measure the mixing ratios of H2 and several other species as well as the H2 isotopic composition in air samples that were collected in the BARCA (Balan o Atmosférico Regional de Carbono na Amaz nia) aircraft campaign during the dry season. We derive a relative H2 emission ratio with respect to carbon monoxide (CO) of 0.31 ± 0.04 ppb/ppb and an isotopic source signature of 280 ± 41‰ in the air masses influenced by tropical biomass burning. In order to retrieve a clear source signal that is not influenced by the soil uptake of H2, we exclude samples from the atmospheric boundary layer. This procedure is supported by data from a global chemistry transport model. The ΔH2/ΔCO emission ratio is significantly lower than some earlier estimates for the tropical rainforest. In addition, our results confirm the lower values of the previously conflicting estimates of the H2 isotopic source signature from biomass burning. These values for the emission ratio and isotopic source signatures of H2 from tropical biomass burning can be used in future bottom-up and top-down approaches aiming to constrain the strength of the biomass-burning source for H2. Hitherto, these two quantities relied only on combustion experiments or on statistical relations, since no direct signal had been obtained from in-situ observations.
Isotope hydrology of dripwaters in a Scottish cave and implications for stalagmite palaeoclimate research
L. Fuller, A. Baker, I. J. Fairchild, C. Sp tl, A. Marca-Bell, P. Rowe,P. F. Dennis
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2008,
Abstract: Dripwater hydrology and hydrogeochemistry is particularly useful in constraining the meaning of speleothem palaeoclimate archives, for example using δ18O signatures. Here, we calibrate the relationship between δ18O in precipitation, percolation waters and contemporary calcite deposits, at Tartair cave, Sutherland, NW Scotland, an Atlantic site sensitive to regional changes both of temperature and precipitation. Monthly precipitation displayed a 7.1‰ range in δ18O, a negative linear relationship with rainfall amount, and no correlation with temperature. Autogenically-derived cave percolation waters show little variation in δ18O during the same period and their annual weighted mean is the same as that of the local precipitation. This evidence together with hydrological data and electroconductivity values indicates that percolation waters are well mixed and dominated by stored water. Calculated values of δ18O of calcite deposited in this cave environment indicate that the cave deposits are forming close to isotopic equilibrium and kinetic effects are negligible. Comparison of a high-resolution δ18O stalagmite record with the instrumental record of climate indicates that isotopically heavy values are reflective of relatively cold, dry conditions (and vice-versa for warm, wet condition) and hence that stalagmite oxygen isotopes provide an appropriate means of investigating the palaeoclimate in this location.
Isotope hydrology of dripwaters in a Scottish cave and implications for stalagmite palaeoclimate research
L. Fuller,A. Baker,I. J. Fairchild,C. Sp?tl
Hydrology and Earth System Sciences Discussions , 2008,
Abstract: Dripwater hydrology and hydrogeochemistry is particularly useful to constrain the meaning of speleothem palaeoclimate archives, for example using δ18O signatures. Here, we calibrate the relationship between δ18O in precipitation, percolation waters and contemporary calcite deposits, at Tartair cave, Sutherland, NW Scotland, an Atlantic site sensitive to regional changes both of temperature and precipitation. Monthly precipitation displayed a 7.1‰ range in δ18O, a negative linear relationship with rainfall amount, and no correlation with temperature. Autogenically-derived cave percolation waters show little variation in δ18O during the same period and their annual weighted mean is the same as that of the local precipitation. This evidence together with hydrological data and electroconductivity values indicates that percolation waters are well mixed and dominated by stored water. Calculated values of δ18O of calcite deposited in this cave environment indicate that the cave deposits are forming close to isotopic equilibrium and kinetic effects are negligible. Comparison of a high-resolution δ18O stalagmite record with the instrumental record of climate indicates that isotopically heavy values are reflective of relatively cold, dry conditions (and vice-versa for warm, wet condition) and hence that stalagmite oxygen isotopes provide an appropriate means of investigating the palaeoclimate in this location.
Isotopic signatures (δ 13C and δ15N) of muscle, carapace and claw in Phrynops geoffroanus (Testudines: Chelidae)
Marques, Thiago S.;Tassoni-Filho, Maurício;Ferronato, Bruno O.;Guardia, Isabela;Verdade, Luciano M.;Camargo, Plínio B. de;
Zoologia (Curitiba) , 2011, DOI: 10.1590/S1984-46702011000300016
Abstract: the isotopic composition ( δ13c and δ 15n) of muscle, carapace and claw was determined from six wild individuals of phrynops geoffroanus (schweigger, 1812) in order to verify the variation between those tissues. the mean values of δ13c e δ 15n were, respectively, -19.48 ± 0.81‰ (-20.8 - -18.64‰) and 7.23 ± 0.67‰ (6.49 - 8.3‰) for muscle, -16.52 ± 0.98‰ (-17.88 - -15.43‰) and 7.29 ± 0.54‰ (6.74 - 7.97‰) for carapace and -18.57 ± 0.97‰ (-19.97 - -17.26‰) and 4.36 ± 0.33‰ (3.93 - 4.79‰) for claw. we found a significant difference for the tissues evaluated for both δ13c and δ15n. muscle and claw were statistically similar and more depleted in 13c than the carapace. nonetheless, claw was more depleted in 15n than muscle and carapace tissues. these results are likely related to differences in metabolic processes involved on each tissue formation. the description of the isotopic signatures variation in p. geoffroanus tissues provides a baseline for future investigations on the diet reconstruction of this species when more than one tissue is involved.
Entrainment, annual circulation and groundwater inflow in a chain of lakes as inferred by stable 18O isotopic signatures in the water column  [cached]
Emanuel BRAIG,Gerhard WELZL,Willibald STICHLER,Uta RAEDER
Journal of Limnology , 2010, DOI: 10.4081/jlimnol.2010.278
Abstract: The stable oxygen isotopic signature δ18O of water has been proved to be a useful marker in hydrological lake studies. However, it is applied only sporadically to determine the extent of mixis and stratification, which is vital for all hydrological and limnological studies. We present a study of the changes in δ18O, temperature and Schmidt stability in the water column of three adjacent lakes of very different mixis types (polymictic to meromictic) over almost one year (May 2008 to April 2009). The response of δ18O to important hydrologic processes (entrainment, stratification, circulation, groundwater inflow) and weather influences (cooling period, ice cover and melt water inflow) is discussed. The lakes are part of the Osterseen chain of lakes south of Munich, Germany. Although hydrologically connected, these lakes show various mixis types (polymictic to meromictic) due to large differences in size, groundwater inflow and water renewal time. Polymixis and the strong subsurface inflow of groundwater in Lake Waschsee (25.6 × 103 m3) were indicated by the same trends in the δ18O signature throughout all water layers and by the mean overall signature (-9.94‰) being very close to δ18O of local groundwater (-10.01‰ ± 0.06). δ18O signatures of the larger dimictic Lake Fohnsee (2298.3 × 103 m3) revealed a highly significant trend towards lower values of δ18O in its hypolimnion, indicating inflow of groundwater. A cooling period during the summer stratification characterised by high wind speeds resulted in a considerable drop of lake surface temperatures and Schmidt stability (up to 25%) in lakes Fohnsee and Eishaussee and was followed by a deepening of the mixed upper water layer and entrainment of hypolimnetic water layers. This was clearly shown by a signal change in deeper water layers formerly constant in δ18O. The permanent meromixis present in Lake Eishaussee (297.0 × 103 m3) could also be confirmed by isotopic signatures, as bottom water layers remained significantly isolated in δ18O from the remaining water column over the whole study period. We summarize that the oxygen isotopic signature of water is an easy to interpret, excellent indicator of important hydrologic processes in a lake and can readily be integrated into routine sampling. The present findings will further contribute to the analysis of hydrological data as well as to the interpretation of paleoclimatic reconstructions using proxies of lake water δ18O.
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