Variations In Stable Isotopic Composition Research Articles

Temporal Variation in Stable Isotopic Composition of Rainfall and Groundwater in a Tropical Dry Forest in the Northeastern Caribbean

AbstractKarst topography links rainfall to groundwater recharge; therefore, possible changes in the hydrology can play an important role in ecosystem function especially in tropical dry forests where water is the most limiting resource. This study investigates the temporal variation in isotopic composition (δ18O and δD values) of rainwater and groundwater in the Guánica Dry Forest of southwestern Puerto Rico. The study not only establishes a dataset of oxygen and hydrogen isotopic composition of rainwater to assist in local ecohydrological studies but also establishes the origin of rainfall in the semiarid region of the island. The geographical position of Puerto Rico in the northeastern Caribbean causes the study site to receive marine air masses from the North Atlantic Ocean and Caribbean Sea. This research documents the monthly to annual variability in stable isotopic composition of rainwater and estimates the source of groundwater recharge in the Guánica Dry Forest.To calculate the local meteoric water line (LMWL), the authors analyzed the isotopic signatures of rainwater, collected at near-monthly intervals from January 2008 to December 2011. The LMWL (δD = 7.79δ18O + 10.85) is close to the global meteoric water line (δD = 8.17δ18O + 11.27). Isotopic signatures of rainwater for the Guánica Dry Forest are consistent with southeastern Caribbean, where rainfall is of marine origin with an annual cycle contributed by sea surface temperature (SST) and significant intermonthly fluctuations due to rainfall and winds during tropical weather events. The d-excess values in the period of data collection (2008–11) respond to the rainfall–evaporation balance, with little seasonal cycle and strong pulsing events. Comparison of rain and groundwater isotopic compositions in the United Nations Educational, Scientific and Cultural Organization (UNESCO) Man and the Biosphere Programme (MAB) Guánica Dry Forest indicates that groundwater recharge is confined to rainfall events of more than 90 mm. Imbalances between rainfall and drought place cumulative stresses on ecosystems where plants and animals synchronize their growth phenology and reproduction to climatic patterns, especially in areas with variable annual cycles. Therefore, it is useful in ecohydrological studies to determine the origins and temporal dynamics of rainfall and groundwater recharge in the Caribbean, where predictions of climate models indicate drying trends.

Hydrogen and oxygen isotopic records in monthly scales variations of hydrological characteristics in the different landscape zones of alpine cold regions

Monthly scale variations in stable isotopic composition in precipitation and various water bodies were analyzed in this study using data collected from a field station. Experimental observation was performed to analyze processes in the glacier-snow zone, alpine cold desert zone, marsh meadow zone, alpine shrub zone, and mountain grassland zone based on the isotopic and hydrochemical analyses of glacier, snow, frozen soil, groundwater, and other water sources in the headwater catchment of the alpine cold region. δ18O and δD values of precipitation and various water bodies in Mafengou River Basin exhibited strong seasonal variations. Precipitation and various water bodies were rich in δ18O and δD during the wet season and relatively negative in δ18O and δD during the dry season. The isotopic content of various water bodies in Mafengou River Basin was dependent on temperature, elevation of the recharge area, and amount of precipitation. Lower temperatures were typically associated with lower δ18O and δD values and are believed to be mainly responsible for the seasonal patterns observed in the isotopic values of various water bodies in Mafengou River Basin in the alpine cold region. Seasonal variations were larger in streams where recent precipitation is the main source of the flow and smaller in streams where groundwater is the dominant source of water.

A study on the spatial variations in stable isotopic composition of precipitation in a semiarid region of Southern India

AbstractThe stable isotope analysis of all major rain events from Moinabad (MB), Rajendranagar (RN) and Osmanasagar (OS) reservoir, three closely placed locations in Hyderabad, India, were carried out during the 2005 to 2008 period. The OS station recorded the highest amount of rainfall with an average value of 1000 mm, whereas the MB station recorded the lowest average rainfall of 790 mm. The stable isotope (δ18O) values of the precipitation samples during these period varied from −11.43‰ to −0.03‰ for the MB station, −8.21‰ to 0.54‰ for the RN station and −11.47‰ to 0.72‰ for the OS station. The d‐excess of precipitation at the three stations also showed considerable variations and revealed that the precipitation in the region undergoes significant modification through secondary evaporation during its fall. The possible causes for these observed spatial and temporal variations in amount and the isotopic composition of precipitation in a small geographical area within the city were studied. The observed variations may be attributed to the regional scale differences in water budget induced by rapid urbanisation activities in the city coupled with the differences in secondary effects undergone by the falling drops. This study elucidating changes in precipitation patterns in the city and its possible causes may largely help in its water balance calculation. Copyright © 2011 John Wiley & Sons, Ltd.

The effect of flow turbulence on growth, nutrient uptake and stable carbon and nitrogen isotope signatures inChara fibrosa

Exposure to water movement has been observed to alter various processes in the plants including growth, hormone concentration and nutrient uptake. In the current study, Chara fibrosa was exposed to three different turbulence conditions and compared with a control. Turbulence was generated in the laboratory by using a vertically oscillating grid setup. Exposure to turbulence caused a reduction in shoot length and nutrient uptake in C. fibrosa. Variation of stable isotope composition was measured as a surrogate variable that is able to integrate variations of many physiological processes. It was initially hypothesized that the reduction of diffu- sion boundary layer around the plant will increase isotopic discrimination against 13 C and 15 N, when exposed to increasing turbulence. Although the results generally agree with the hypothesis, a trend of increment was observed in d 13 C in the plants exposed to turbulent velocities from 0.46 to 1.93 cm s x1 , against the hypothesis. Mechanical stress induced reduction of carbon uptake and lipid peroxidation due to the development of oxidative stress may be the reasons behind the above-mentioned trend. The study exhibits that the net effect of physical and physiochemical changes of the plants was displayed in d 13 C signatures and it is important to consider physical conditions of the local environment, in using stable isotope signatures for ecosystem studies.

Sulfur Degassing From Volcanoes: Source Conditions, Surveillance, Plume Chemistry and Earth System Impacts

Research Article| January 01, 2011 Sulfur Degassing From Volcanoes: Source Conditions, Surveillance, Plume Chemistry and Earth System Impacts Clive Oppenheimer; Clive Oppenheimer 1Le Studium, Institute for Advanced Studies, Orléans and Tours, France2Centre National de la Recherche Scientifique-Institut National des Sciences de, l’Univers, Université d’Orléans, Université François Rabelais de Tours, Institut des Sciences de la Terre d’Orléans, 1a rue de la Férollerie, Orléans 45071, France3Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, United Kingdom Search for other works by this author on: GSW Google Scholar Bruno Scaillet; Bruno Scaillet 2Centre National de la Recherche Scientifique-Institut National des Sciences de, l’Univers, Université d’Orléans, Université François Rabelais de Tours, Institut des Sciences de la Terre d’Orléans, 1a rue de la Férollerie, Orléans 45071, France Search for other works by this author on: GSW Google Scholar Robert S. Martin Robert S. Martin 4School of Biological and Chemical Sciences, Queen Mary, University of London, United Kingdom, co200@cam.ac.uk Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2011) 73 (1): 363–421. https://doi.org/10.2138/rmg.2011.73.13 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Clive Oppenheimer, Bruno Scaillet, Robert S. Martin; Sulfur Degassing From Volcanoes: Source Conditions, Surveillance, Plume Chemistry and Earth System Impacts. Reviews in Mineralogy and Geochemistry 2011;; 73 (1): 363–421. doi: https://doi.org/10.2138/rmg.2011.73.13 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search Despite its relatively minor abundance in magmas (compared with H2O and CO2), sulfur degassing from volcanoes is of tremendous significance. It can exert substantial influence on magmatic evolution (potentially capable of triggering eruptions); represents one of the most convenient opportunities for volcano monitoring and hazard assessment; and can result in major impacts on the atmosphere, climate and terrestrial ecosystems at a range of spatial and temporal scales. The complex behavior of sulfur in magmas owes much to its multiple valence states (−II, 0, IV, VI), speciation (e.g., S2, H2S, SO2,... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Preservation of primary stable isotope signatures of peat-forming plants during early decomposition — observation along an altitudinal transect

The preservation of the primary stable isotope compositions of peat-forming plants in peat was tested along a short (< 3.5 km), steep (739–1393 m asl) altitudinal transect. The stable isotope compositions in plant cube samples taken from the surface of mires were compared with the stable isotope compositions in cube samples of the underlying young peat for the following elements: hydrogen, carbon, nitrogen, oxygen and sulfur (HCNOS). Electron paramagnetic resonance (EPR) measurements were also compared. Statistically significant correlations (p ≤ 0.03) for the pairs of plant-peat samples among all analyzed elements suggested that the stable isotope compositions of peat are primarily determined by the stable isotope compositions of the peat-forming plants. This implies that preservation of the plants' primary stable isotope variations (e.g., from the time of plant growth) is well preserved in young peat and that the overall decomposition during peat formation has only a secondary influence on the final peat stable isotope composition. We were able to detect relative variations in stable isotope composition between plants growing in different conditions and/or at different times. The EPR results confirmed the more anoxic conditions of decomposition at lower altitudes and more oxic conditions at higher altitudes, which involved an increase in oxygen centered free radicals. The observed correlations between the stable isotope compositions of plants and altitude indicated that the δ 13C value of peat-forming plants is primarily controlled by growing season temperature, while the δ 2H and δ 18O values are controlled by stable isotope composition of surface water. The δ 15N and δ 34S values appear to reflect different distributions and concentrations of anthropogenic pollution at the sites of peat-forming plant growth. A strong and statistically significant correlation between altitude/temperature and δ 13C of plants and peats indicates a good preservation of primary stable carbon isotope composition. Thus, the analysis of peat stable isotope compositions could be useful for paleoclimate and paleoenvironmental evaluations.

A study on the factors affecting the stable isotopic composition in precipitation of Tamil Nadu, India

AbstractStable isotope measurements in precipitation help us to form the basic inference about the origin and the state of water in different environments. The precipitation samples collected during the South West Monsoon (SWM) during August 2007 from 37 different locations in the state help in deriving the first preliminary local meteoric water line (LMWL) for the Tamil Nadu State. The study reveals that there are three main sources of water vapours, namely South East Arabian Sea (SEAS), Indian Ocean (IO) and evaporation from local water bodies. There are wide variations in the altitude and amount of rainfall received in the state. It is also noted that there is a significant variation in the latitude and the distance from the coast. Hence, an attempt is made in this paper to study the factors controlling the composition of stable isotopes in precipitation with reference to amount of rainfall, latitude, altitude and the continental effect. The altitude and continental effect shows good correlation to the variations in stable isotope composition. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Variations in stable isotope compositions (δ13C, δ18O) of calcite within exhumation-related veins from the Sanbagawa metamorphic belt

Stable isotope compositions (δ13C, δ18O) of calcite within the veins hosted by the Sanbagawa metamorphic rocks in the Nagatoro area, Kanto mountains, Japan gave clues on movement of fluids during exhumation. The host rock calcite shows the nearly uniform δ18O values ranging from +14.5 to +16.5‰ (V-SMOW), and wide δ13C variation from −12.1 to +1.3‰ (V-PDB). The δ13C values of calcite within the exhumation-related veins also have wide variation, and the Δhost-vein (= δ13Chost rock-δ13Cvein) value vary depending on vein thickness and textures. Thin stretched crystal veins contain calcite with δ13C value close to that of the host rock calcite (Δhost-vein < ±2‰). In contrast, calcite grains within the thick blocky veins have homogenous δ13C values with large variations with host rock (Δhost-vein = +3.5 - −3.0‰). The latter types of sealed cracks may have played as dominant pathways of regional fluid flow.

Factors controlling seasonal variations in stable isotope composition of particulate organic matter in a softwater eutrophic lake

Weekly water samples were taken to measure stable isotope composition (δ13C and δ15N) of particulate organic matter (POM) in Lake Wauberg, Florida, from June 1994 to May 1995. The average δ13C of POM was ‐19.3%, consistent with an autochthonous origin from phytoplankton production, and exhibited a seasonal pattern that coincided with changes in water temperature, pH, CO2 concentration, and phytoplankton biomass in the surface water. The 13C enrichment in POM was attributed to reduced isotope fractionation due to carbon (C) limitation and the use of an isotopically heavy dissolved inorganic carbon pool supported mainly by atmospheric invasion and anaerobic respiration. Intermittent declines in δ13C of POM were related to the frequent collapses of phytoplankton blooms and increases in CO2 concentration resulting from both increased community respiration and terrestrial loading. Average δ15N of POM was 1.3% and varied within a narrow range (20.1% to 2.5%). No significant correlation between phytoplankton biovolume and the δ15N of POM was found. The low δ15N is indicative of strong N2 fixation, which is in line with the low concentration of dissolved inorganic nitrogen and the presence of high biovolume of N2‐fixing cyanobacteria in the surface water. This study suggests that stable C isotopes are good proxies for surface water CO2 concentration and primary production, while stable N isotopes can be used to indicate N2 fixation.

Seasonal variation in stable isotopic composition of alas lake water near Yakutsk, Eastern Siberia

Detailed measurements of temporal variations in the stable isotopic composition of precipitation and lake water were conducted in the permafrost region near Yakutsk, eastern Siberia. The δ18O ranged from approximately −30 to −5‰ in precipitation and from −25 to −5‰ in lake water were observed from April to August, 2000. Temporal changes in δ18O of precipitation observed weekly at 12 sites all showed the same trend. The temporal variation of δ18O in lakes classified into two groups: isotopically steady-state lakes with less than 5‰ variation, and non-steady-state lakes with variation exceeding 10‰. In non-steady-state lakes, the water originated from snowmelt, and the δ18O of lake water gradually enriched as a result of evaporation during the summer. In steady-state lakes, the water originated predominantly from 18O-enriched lake water that had evaporated in the previous summer. The temporal volumetric and isotopic variations in alas lakes are accurately depicted by an isotope mass-balance model using Rayleigh fractionation over daily time steps. The inflow of soil water (subsurface flow) was estimated to be constant (200 m3/day) from May to August, based on the difference between observed and simulated lake volumes. Taking the isotopic mass-balance into consideration, the soil water in lower part of the active layer is inferred as a major component of inflow which has a δ18O of about −23‰.

Variation of precipitation δ18O in Langtang Valley Himalayas

The variation of the δ18O in precipitation and the relationship with precipitation amount at Kyangjin Base House and Yala Glacier Camp in Langtang Valley, Nepal Himalayas were analyzed. The variations of the δ18O with precipitation had great scatter, and the correlations between the δ18O and precipitation changed with time on the synoptic scale. On the seasonal scale, there was marked amount effect at Kyangjin Base House. However, the δ18O-precipitation gradient was smaller than that on the synoptic scale. Because of the maintenance of the basic equilibrium between stable isotopic compositions in atmospheric vapor and precipitation, the evaporation enrichment was light during the rainy season. Therefore, the variation of stable isotopic compositions in precipitation was independent on the sampling intervals. Simulations show that the rainfall in Langtang Valley was not the outcome of the initial condensation of ocean vapor that originated from low latitudes. The stable isotopic compositions in precipitation were greatly depleted due to the strong rainout of the vapor from oceans as the vapor was raised over the Himalayas.

Seasonal variation of stable isotopic compositions recorded in a laminated tufa, SW Japan

High-resolution stable isotopic analyses of an annually laminated tufa from Shirokawa, SW Japan, show cyclic variations that correspond to mm-scale summer (dense) and winter (porous) laminae. Both δ 18O and δ 13C values are high in winter and low in summer, and correlate well with each other ( r=0.88). Because the δ 18O content of stream water has remained relatively stable over time, the δ 18O curve reflects seasonal changes in water temperature. Cyclic variation in δ 13C suggests that it is controlled by seasonal changes in the δ 13C of dissolved inorganic carbon in groundwater, which is probably caused by groundwater degassing. This degassing effect is normally strongest during winter when subsurface air is warmer (less dense) than the atmosphere. This decreases P CO 2 in cave air, and the associated degassing of 13C-depleted CO 2 from the groundwater increases the δ 13C value of dissolved inorganic carbon in winter. Calcite was deposited in isotopic equilibrium with stream water. Extreme climatic events, such as drought, can be recorded as anomalies in both the δ 18O and δ 13C curves. This study demonstrates that annually laminated tufa can be used for high-resolution analysis of terrestrial paleoclimate.

Groundwater residence time and palaeohydrology in the Otway Basin, South Australia: 2H, 18O and 14C data

Stable isotopes (δ 2H, δ 18O and δ 13C) and radiocarbon ( 14C) have been used in conjunction with chemical data to evaluate recharge mechanisms, groundwater residence time and palaeohydrology within the confined Dilwyn sand aquifer in the Gambier Embayment of the Otway Basin. This aquifer does not receive recharge down-gradient of the hydraulic hinge-line and data have been interpreted along two discrete flow lines. The mean residence time of groundwater (determined by 14C) in the confined aquifer from the hydraulic hinge position to the sea (a distance of about 50 km) along an inferred flow path is approximately 12 800 years. The corresponding hydraulic travel time calculated from Darcy's law is approximately 49 000 years. The apparent discrepancy may be a result of eustatic sea-level lowering during the last glacial. Because the groundwater system is hydraulically connected to the sea, lower sea-level would result in increased gradients and a decrease in groundwater residence time. Variations in stable isotopic composition along flow lines suggest a number of recharge mechanisms. Stable isotope data indicate progressive depletion of 2H and 18O in the groundwaters over the past 30 000 years. Groundwaters older than about 10 000 years B.P. were recharged either during a cooler climate climatic regime (lower precipitation/evapotranspiration and temperature) and/or the vapour source(s) had travelled over greater continental mass than those recharged over the past 10 000 years. Lower chloride concentrations in some of the older groundwaters indicate lower evapotranspiration rates in the recharge areas before 10 000 years ago.

Isotopic study of Pb pollution in surface waters from the northwest Atlantic Ocean

Stable isotopes (δ2H, δ18O and δ13C) and radiocarbon (14C) have been used in conjunction with chemical data to evaluate recharge mechanisms, groundwater residence time and palaeohydrology within the confined Dilwyn sand aquifer in the Gambier Embayment of the Otway Basin. This aquifer does not receive recharge down-gradient of the hydraulic hinge-line and data have been interpreted along two discrete flow lines. The mean residence time of groundwater (determined by 14C) in the confined aquifer from the hydraulic hinge position to the sea (a distance of about 50 km) along an inferred flow path is approximately 12 800 years. The corresponding hydraulic travel time calculated from Darcy's law is approximately 49 000 years. The apparent discrepancy may be a result of eustatic sea-level lowering during the last glacial. Because the groundwater system is hydraulically connected to the sea, lower sea-level would result in increased gradients and a decrease in groundwater residence time. Variations in stable isotopic composition along flow lines suggest a number of recharge mechanisms. Stable isotope data indicate progressive depletion of 2H and 18O in the groundwaters over the past 30 000 years. Groundwaters older than about 10 000 years B.P. were recharged either during a cooler climate climatic regime (lower precipitation/evapotranspiration and temperature) and/or the vapour source(s) had travelled over greater continental mass than those recharged over the past 10 000 years. Lower chloride concentrations in some of the older groundwaters indicate lower evapotranspiration rates in the recharge areas before 10 000 years ago.

STABLE ISOTOPES IN ECOSYSTEM STUDIES

The use of stable isotopes to solve biogeochemical problems in ecosystem analysis is increasing rapidly because stable isotope data can contribute both source-sink (tracer) and process information: The elements C, N, S, H, and all have more than one isotope, and isotopic compositions of natural materials can be measured with great precision with a mass spectrometer. Isotopic compositions change in predictable ways as elements cycle through the biosphere. These changes have been exploited by geochemists to understand the global elemental cycles. Ecologists have not until quite recently employed these techniques. The reasons for this are, first, that most ecologists do not have the background in chemistry and geochemistry to be fully aware of the possibilities for exploiting the natural variations in stable isotopic compositions, and second, that stable isotope ratio measurements require equipment not normally available to ecologists. This is unfortunate because some of the more intractable problems in ecology can be profitably addressed using stable isotope measurements. Stable isotopes are ideally suited to increase our understanding of element cycles in ecosystems. This review is written for ecologists who would like to learn more about how stable isotope analyses have been and can be used in ecosystem studies. We begin with an explanation of isotope terminology and fractionation, then summarize isotopic distributions in the C, N, and S biogeochemical cycles, and conclude with five case studies that show how stable isotope measurements can provide crucial information for ecosystem analysis. We restrict this review to studies of natural variations in C, N, and S isotopic abundances, cxcluding from consideration ~5N enrichment studies and hydrogen and oxygen isotope studies. Our focus on C, N, and S derives in part from our