Stable Isotopes: Tools for Understanding Past Climatic Conditions and Their Applications in Chemostratigraphy
01 Jan 2015-pp 65-92
TL;DR: In this paper, the use of stable isotopes of the most widely used elements viz. oxygen, carbon, and nitrogen from the marine realm and their systematics is discussed in order to understand the pattern of evolution of the earth's climate system, its rhythm, and pulse using various natural archives such as marine and lacustrine sediments.
Abstract: The present climatic deterioration including the much debated anthropogenic acceleration to the global warming phenomenon has drawn the attention of scientific community, policy makers as well as the general public to the problem of climate change. Chemostratigraphic techniques have proven to be very useful to understand the past climate of the earth that has been changing naturally on timescales ranging from decades to millions of years. Therefore, it is important to filter out the natural signal to correctly gauge the effects induced by humans. This is where the science of paleoclimatology becomes very important. It helps us to understand the pattern of evolution of the earth's climate system, its rhythm, and pulse using various natural archives such as marine and lacustrine sediments, speleothems, ice cores, corals, trees, etc., that hold the clue to the past climate variability. Several proxies are studied from such natural archives to reconstruct the past climatic changes. Out of these, the stable isotopes are one of the most useful and widely employed. In this present study, we explain the methodology behind the application of the stable isotopes as a proxy to reconstruct past climatic changes. We present here a few examples of the stable isotopes of the most widely used elements viz oxygen, carbon, and nitrogen from the marine realm and their systematics. The use of chemostratigraphic techniques like application of oxygen isotopes in stratigraphy, temperature, salinity, and ice-volume reconstruction; Cenozoic oxygen and carbon isotope curves; the limitations in the form of vital effect and diagenesis in the case of foraminifera; use of nitrogen and carbon isotopes as productivity and provenance indicator, respectively, are presented in this paper.
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TL;DR: It is shown that the marine organic matter is unusually more depleted in 13C than the terrestrial organic matter, which helps explain high δ13C values of SOM as noted by earlier studies in central Arctic sediments despite a high terrestrial contribution.
Abstract: Accurate estimation of relative carbon deposition (marine vs. terrestrial) is required for understanding the global carbon budget, particularly in the Arctic region, which holds disproportionate importance with respect to global carbon cycling. Although the sedimentary organic matter (SOM) concentration and its isotopic composition are important tools for such calculations, uncertainties loom over estimates provided by organic-geochemical bulk parameters. We report carbon and nitrogen concentrations and isotopes (δ13C and δ15N) of SOM at an Arctic fjord namely Kongsfjorden. We find that the bound inorganic nitrogen (ammonium attached to the clay minerals) forms a significant proportion of total nitrogen concentration (~77% in the inner fjord to ~24% in the outer part). On removing the bound nitrogen, the C/N ratio shows that the SOM in the inner fjord is made up of terrestrial carbon while the outer fjord shows mixed marine-terrestrial signal. We further show that the marine organic matter is unusually more depleted in 13C (~-24‰) than the terrestrial organic matter (~-22.5‰). This particular finding also helps explain high δ13C values of SOM as noted by earlier studies in central Arctic sediments despite a high terrestrial contribution.
23 citations
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TL;DR: This review discusses the ongoing developments in tracing migration pathway and distribution of lead in various terrestrial-compartments and investigates the processes regulating the Pb isotope geochemistry taking into account the source identification of lead, its transformation among miscellaneous terrestrial- compartment and detoxification mechanism in soil-plant system.
Abstract: Lead (Pb) is a non-essential and extremely noxious metallic-element whose biogeochemical cycle has been influenced predominantly by increasing human activities to a great extent. The introduction and enrichment of this ubiquitous contaminant in the terrestrial-environment has a long history and getting more attention due to its adverse health effects to living organisms even at very low exposure levels. Its lethal-effects can vary widely depending on the atmospheric-depositions, fates and distribution of Pb isotopes (i.e., 204Pb, 206Pb, 207Pb &208Pb) in the terrestrial-environment. Thus, it is essential to understand the depositional behavior and transformation mechanism of Pb and the factors affecting Pb isotopes composition in the terrestrial-compartments. Owing to the persistence nature of Pb-isotopic fractions, regardless of ongoing biogeochemical-processes taking place in soils and in other interlinked terrestrial-compartments of the biosphere makes Pb isotope ratios (Pb-IRs) more recognizable as a powerful and an efficient-tool for tracing the source(s) and helped uncover pertinent migration and transformation processes. This review discusses the ongoing developments in tracing migration pathway and distribution of lead in various terrestrial-compartments and investigates the processes regulating the Pb isotope geochemistry taking into account the source identification of lead, its transformation among miscellaneous terrestrial-compartments and detoxification mechanism in soil-plant system. Additionally, this compendium reveals that Pb-pools in various terrestrial-compartments differ in Pb isotopic fractionations. In order to improve understanding of partition behaviors and biogeochemical pathways of Pb isotope in the terrestrial environment, future works should involve investigation of changes in Pb isotopic compositions during weathering processes and atmospheric-biological sub-cycles.
14 citations
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TL;DR: In this paper, the authors show that the observed TOC increase is not a result of enhanced productivity but is because of better preservation due to the increased sedimentation rate along with increasingly reducing conditions since mid-Holocene.
Abstract: The earlier studies show a contrasting long-term trend of the South Asian Summer Monsoon (SASM) after attaining the precessional forcing induced mid-Holocene maximum. The increasing total organic carbon (TOC) concentration of marine sediments in the Southeastern Arabian Sea (SEAS) has been interpreted to imply strengthening SASM since mid-Holocene by a few studies. However, TOC concentration is also influenced by redox conditions, sedimentation rate, and an influx of terrigenous matter depending on the regional settings. So, it needs to be ascertained whether the TOC concentration of the sediments in the SEAS is a signal of productivity related to the SASM strength or preservation. Therefore, we studied multiple proxies (TOC, total nitrogen, atomic C/N, δ13Corg, CaCO3, and major and trace elements concentration) for determining the productivity, redox conditions, detrital supply, and provenance in a sediment core from the upper continental slope of the SEAS spanning the past ∼4700 years at centennial scale resolution. The present study shows that the observed TOC increase is not a result of enhanced productivity but is because of better preservation due to the increased sedimentation rate along with increasingly reducing conditions since mid-Holocene. We further show that the SASM has been declining since mid-Holocene after attaining a precession-forced maximum, which corroborates the earlier model ensemble studies.
9 citations
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TL;DR: In this article, the ionic and isotopic composition (δ18O and δ2H) of six high-altitude streams and one pond in the Italian Alps (Noce and Sarca basins) during the ablation season in 2018 were investigated.
Abstract: Glaciers are shrinking due to global warming, resulting in a diminishing contribution of ice and snowmelt to headwaters and subsequent consequences to freshwater ecosystems. Within this context, we tested whether water-stable isotopes are spatio-temporal tracers of (i) water in high altitude periglacial environments, being the isotopic signature of surface water inherited from the snow/icemelt, groundwater, and rainfall; and (ii) regional (year-specific) meteorological conditions, being the isotopic signature of precipitations affected by air temperature, humidity and aqueous vapour origin, ascribing stable isotopes to the list of “essential climate variables″ (ECVs). To this end, we investigated the ionic and isotopic composition (δ18O and δ2H) of six high-altitude streams and one pond in the Italian Alps (Noce and Sarca basins) during the ablation season in 2018. Differences between habitat types (pond, kryal, rhithral, krenal) were detected. More negative values of δ18O and δ2H were recorded in the kryal and glacio-rhithral sites, dominated by ice and snowmelt, in early summer. Less negative values were recorded in these sites in late summer, as well as in the krenal sites, which were dominated by groundwater and rainfall inputs. The isotopic results also show that the complex alpine orography influences air masses and moisture, ultimately resulting in isotopic differences in the precipitations of neighboring but distinct catchments (Sarca and Noce basins). On average, less negative values were recorded in the Sarca basin, characterized by a higher contribution of precipitation of Mediterranean origin. In general, isotopic results of the entire water population appeared to be strongly influenced by the regional climatic anomaly of 2018, which was anomalously warm. Therefore, the study will provide additional information for the climate change debate, proposing water isotopes as ECVs for assessing change in a warmer future.
6 citations
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TL;DR: In this paper, Galdieria phlegrea was used for municipal wastewater treatment, where it was found to grow in raw effluent and remove more than 50% ammonium and 20% phosphate in 24 hours.
Abstract: Algal based wastewater treatment offers the opportunity to recover, in the form of biomass, the nutrients and internal chemical energy of wastewater. Recently, there has been a growing interest in the use of extremophilic microalgae, as they can easily adapt to difficult and often pollutant-rich environments. The thermo-acidophilic microalga Galdieria phlegrea is a species of recent discovery and great metabolic versatility, but it has still been poorly studied. Here, G. phlegrea was cultivated using raw municipal wastewater in 1 L Erlenmeyer flasks with 700 mL working volume at 37 °C for up to nine days. During the cultivation phase, biomass growth, phycocyanin content, ammonium and phosphate removal from the wastewater, lipid fraction, total carbon and nitrogen in the biomass, and variation in δ13C and δ15N isotopic ratios (a novel analytical contribution in these experiments) were monitored. Results indicated that G. phlegrea was able to grow in raw effluent, where it removed more than 50% ammonium and 20% phosphate in 24 h; total lipid content was in the range of 11–22%, while average C-N content was of 45% and 6%, respectively; isotopic analyses proved to be a useful support in identifying C and N metabolic pathways from effluent to biomass. Overall, G. phlegrea showed consistent performance with similar Cyanidiophyceae and is a potentially viable candidate for municipal wastewater valorization from a circular economy perspective.
4 citations
References
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01 Jan 2012
TL;DR: The Global Energy Assessment (GEA) as mentioned in this paper identifies strategies that could help resolve the multiple challenges simultaneously and bring multiple benefits, including sustainable economic and social development, poverty eradication, adequate food production and food security, health for all, climate protection, conservation of ecosystems, and security.
Abstract: Energy is essential for human development and energy systems are a crucial entry point for addressing the most
pressing global challenges of the 21st century, including sustainable economic and social development, poverty
eradication, adequate food production and food security, health for all, climate protection, conservation of ecosystems,
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A major transformation is therefore required to address these challenges and to avoid potentially catastrophic future
consequences for human and planetary systems. The Global Energy Assessment (GEA) demonstrates that energy
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resolve the multiple challenges simultaneously and bring multiple benefits. Their successful implementation requires
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01 Jan 2013
TL;DR: In this paper, a summary of issues to assist policymakers, a technical summary, and a list of frequently-asked questions are presented, with an emphasis on physical science issues.
Abstract: Report summarizing climate change issues in 2013, with an emphasis on physical science. It includes a summary of issues to assist policymakers, a technical summary, and a list of frequently-asked questions.
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01 Jan 1989
TL;DR: In this article, the physical and enzymatic bases of carbone isotope discrimination during photosynthesis were discussed, noting how knowledge of discrimination can be used to provide additional insight into photosynthetic metabolism and the environmental influences on that process.
Abstract: We discuss the physical and enzymatic bases of carbone isotope discrimination during photosynthesis, noting how knowledge of discrimination can be used to provide additional insight into photosynthetic metabolism and the environmental influences on that process
5,769 citations
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TL;DR: In this paper, a 53-Myr stack (LR04) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm is presented.
Abstract: [1] We present a 53-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N Stacked sedimentation rates provide additional age model constraints to prevent overtuning Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 53 Myr and in the precession band for more than half of the record The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 27–16 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 16 Ma
5,759 citations
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