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We want to collect rainfall samples to establish a local meteoric water line using stable isotope ratios (δD and δO18). We've built our own rainfall totalizers and bottles will be switched on a monthly basis. What is the best way to clean collection bottles as well as other components of the rainfall totalizers if they will be re-used? Is washing with distilled water and air-drying adequate?
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passed through 0.45 μm Millipore filters into 20 ml high-density polyethylene bottles.
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What is the detailed methdology for RBC Fe enrichment studies using stable isotopes of iron. Any help will be valuable.
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I just came across this paper. Hope this helps.
'Iron Absorption and Red Blood Cell Incorporation in Premature Infants Fed an Iron-Fortified Infant Formula' by Meghan C McDonald, Steven A Abrams & Richard J Schanler.
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The food web analysis using stable carbon and nitrogen will be done separately for GFP and other finfish in the particular reservoir in Sri Lanka. Therefore, Isotopic tagging using stable carbon and nitrogen isotopes will not be possible. We are looking for another stable isotope that we could be working with to isotopic tagging of GFP post-larvae? Any references or ideas are highly appreciated.
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Isotopic tagging Using stable isotopes except carbon and nitrogen?
They can be used on land as well as in the ocean and have revolutionized how researchers study animal movement.
'You Are What You Eat'
Stable isotope analysis is based on the principle ‘you are what you eat.' Stable isotope ratios vary among food webs and are incorporated into an animal's tissue via its diet (Hobson 1999). It is thus sometimes possible to infer the whereabouts of an animal moving between food webs. It is important, however, to choose the appropriate tissue for isotopic analysis, as tissues differ in how metabolically active they are (Rubenstein & Hobson 2004). Keratin-based tissues, such as hair, feather, nail, claw or bill, are metabolically inert after synthesis. They are usually used to study seasonal movements because an isotopic record reflecting the location of tissue synthesis remains unchanged. Conversely, metabolically active tissues provide dietary and source information for a relatively shorter period. For example, blood plasma and liver turnover elements in a matter of days or even hours, but this process takes up to several weeks in muscle and whole blood, and up to several months or even years in bone collagen (Hobson 1999). Studies that examine long-term movements therefore use metabolically inert tissues, while studies on recent movements (e.g., distinguishing between newly arrived and resident individuals) use metabolically active tissues with rapid turnover rates.
Stable Isotopes Used in Terrestrial Systems
Carbon (13C/12C)
Carbon isotopic signatures can be used to distinguish plants that use C3, C4 and CAM modes of photosynthesis, as the C4 and CAM pathways lead to lower carbon fractionation than C3 photosynthesis (Karasov & Martínez del Rio 2007). Carbon isotopes can thus be used to reconstruct migratory routes, if the geographical distribution of C3, C4and CAM plants is known and the diet preferences of the study species (Hobson 1999). Carbon isotopic changes corresponding to dietary changes in a migratory species were first demonstrated in bats (Fleming et al. 1993). It has since been used in other migratory species, including lesser snow geese (Chen caerulescens), in which it was used to infer the wintering origin (Alisaukas et al. 1993). More recently, other stable isotopes, such as nitrogen and strontium, have been added to increase the spatial resolution (Hobson 1999). Carbon isotopes have also been used to infer individual fitness of migratory birds arriving at the breeding ground (Marra et al. 1998). An intriguing avenue for future research is the isotopic discrimination of exhaled breath (CO2), which does not require sacrificing the study animal to obtain a tissue sample (Hobson & Wassenaar 2008).
Nitrogen (15N/14N)
One of the most important applications of nitrogen stable isotopes is its ability to determine the trophic level of a species. Nitrogen undergoes an increase (2-4%) in heavy isotope enrichment with each trophic level and can therefore serve as a tool in determining dietary shifts (Hobson & Wassenaar 2008). A potential problem is that nitrogen is a building block of proteins and therefore may succumb to protein catabolism occurring during migration, which can cause increased nitrogen isotope fractionation that is unpredictable (Hobson & Wassenaar 2008).
Hydrogen (2H/1H)
Deuterium (the heavy hydrogen isotope) has revolutionized stable isotope analysis in the study of animal migration. Unlike other stable isotopes, which require analysis on a species-by-species basis, deuterium signatures can be used to create a continental isotopic map, which is applicable to all migratory species (Figure 1). Deuterium ratios vary strongly with weather conditions, resulting in highly predictable spatial variation across continents (Hobson & Wassenaar 2008). Constructing continental maps that predict deuterium levels is therefore relatively straightforward, given the large amount of existing data on continental weather patterns. These maps detailing variation in deuterium were quickly utilized by biologists to determine migratory origins of species. Deuterium ratios in feathers and claws were shown to be effective indicators of breeding latitude in birds (Hobson & Wassenaar 2008, Bearhop et al. 2003). Determination of migratory origins using hydrogen does not necessarily require sacrificing individuals. Nevertheless, there are several pitfalls when using hydrogen isotope analysis. There are small-scale heterogeneities that are not accounted for in global isotopic maps, including variation with altitude (Hobson & Wassenaar 2008).
Figure 1: Contours of growing season average deuterium (δD) values in precipitation in North America used to link organisms to broad geographic origins.
Filled circles represent the location of sampling sites.
© 2012 Nature Education Modified from Hobson (1999). All rights reserved. 📷
Stable Isotopes in Aquatic Systems
Carbon (13C/12C)
Carbon isotopes in tissues of aquatic animals reflect the primary producers in the area of feeding and therefore can be used determine diet and movement in space and time, following the same principle used in terrestrial studies. Carbon isotope ratios in marine systems have been utilized to determine movements of migratory species between inshore and offshore ecosystems and dietary changes during migration. They have not yet been applied to migratory species in freshwater systems. Fry (1981) showed that inshore seagrass beds were more enriched in C13 compared to those offshore, and used this patterns to determine life history cycle and migratory movement in several populations of Texas brown shrimp (Penaeus aztecus). Hobson et al. (1994) also used this trend in offshore and inshore carbon isotopic fractionation to distinguish populations of migratory seabirds in British Colombia, Canada. Carbon isotope ratios have also been used to show dietary changes in migrating whales. Schell et al. (1989) determined that oscillations in carbon isotope ratios were due to different zooplankton in the wintering and summer areas of bowhead whale (Balaena mysticetus). Peaks in carbon oscillations were also utilized to determine dietary changes in southern right whale's (Eubalaena australis) migratory route (Best & Schell 1996). The distinct isotopic differences between freshwater and marine food webs, the latter of which is more enriched in C13 were used to identify feeding areas in seabirds, and distinguishing subpopulations in seals (Mizutani et al. 1990, Smith et al. 1996).
Nitrogen (15N/14N)
As mentioned above, nitrogen isotope ratios change when protein catabolism is taking place. This allows distinguishing migratory routes in which animals continue to feed from routes in which they do not. In bowhead whales oscillations in nitrogen isotopic ratios were used to determine that they were in fact feeding during southward migration, but fasted during northward migration (Best & Schell 1996). Likewise, juvenile sooty shearwaters (Puffinus griseus) were shown to be feeding during northward migration while adults did not (Minami & Ogi 1997). Nitrogen fractionation has also been used to distinguish trophic levels in migratory fish in fresh and marine environments (Hobson & Wassenaar 2008).
Oxygen (18O/16O)
Oxygen was the first stable isotope used to determine migratory history in marine environments. Stable isotope analyses using marine oxygen have used barnacle shells attached to the study animal. As barnacles grow, the oxygen stable isotope profiles in the calcite of their shells reflect the salinity and temperature of ambient waters. Therefore, large animals moving through parts of the ocean that differ in temperature and salinity will carry with them information on where they have been in their barnacles. This approach was first used to delineate the life history of California gray whales (Eschritchitius robustus), and was also used in combination with carbon to delineate periods of time where loggerhead turtles (Caretta caretta) spent during migration (Killingley 1980, Killingley & Lutcavage 1983).
Strontium (87Sr/86Sr)
Stable isotope analysis using strontium is effective for analyzing the origin of anadromous fish (those migrating upriver from the sea to breed in freshwater). Otoliths, a component of the inner ear bone of fish, have annual rings that reflect the isotopic profile of the water where the fish spent its growth period, as the strontium isotope ratios in stream water reflect watershed geology and are thus driven by abiotic processes (Kennedy et al. 1997). Otoliths have therefore been very useful in studying the life history of migratory fish (Hobson 1999). Kennedy et al. (1997) also used strontium stable isotope profiles of natal streams to predict the origins of Atlantic salmon (Salmo salar). This approach has since been extended to determining the natal origin of other Atlantic salmon in combination with nitrogen (Harrington et al. 1998).
Sulfur (34S/32S)
Generally, several isotopes are used to determine dietary sources in migratory species in both marine and terrestrial environments. Of these, sulfur is particularly useful, because its isotope ratios are invariant in the ocean and consistently negative in terrestrial ecosystems. Sulfur isotopic variation has been used to distinguish marine feeding from non-marine feeding populations of birds of prey (Casey & Meehna 2003). However, the majority of studies utilizing sulfur to study shifts between marine and terrestrial food sources have focused on non-migratory species. Sulfur ratios have also been used to determine whether salmon are migratory, and to distinguish hatchery from wild salmon (Weber et al. 2002, Godbout et al. 2010).
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As we know that Li-7 is stable isotope of lithium. When it captures a thermal neutron it divides in alpha particle and triton by n, alpha reaction.
If Li-7 is stable nucleus then why does it transform in H-3 and He-4?
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When 6Li captures a thermal neutron, the resultant compound nucleus of 7Li ends up in an excited state with 7.2508146 MeV above ground level. The preferred de-excitation mode in this case is an alpha decay.
The excitation energy can be calculated using the mass of reactant and end products.
The capture reaction is 6Li + 1n ——> 7Li.
The masses of 6Li, neutron and 7Li are 6.015123 u, 1.008665 u and 7.016004 u respectively.
Therefore the excitation energy of 7Li compound nucleus is
( 6.015123 + 1.008665 - 7.016004) u * 931.50239 MeV/u = 7.2508146 MeV.
Moreover we can calculate the reaction Q value for the below reaction:
6Li + n ——> 4He + 3H
The reaction Q value is (6.015123 + 1.008665 - 4.002603 - 3.016050) u * 931.50239 MeV/u = 4.7832648 MeV.
This 4.7832648 MeV of energy gets distributed between the 4He and 3H. The momentum conservation requires the two particles to be ejected in opposite direction. Using the simultaneous energy and momentum conservation laws, the energy of each particle can be calculated with
Kinetic Energy of 3H particle KE(3H) = m(4He) * Q / ( m(3H) + m(4He)) = 2.7278040 MeV
and
Kinetic Energy of 4He particle KE(4He) = m(3H) * Q / ( m(3H) + m(4He)) = 2.0554608 MeV.
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Analysis of a carbonate (calcite vein) sample yielded d18O of 6.09 (V-SMOW) and d13C of -4.23 (V-PDB), and only 47 ppm Sr. Stable isotopic data indicate 'mantle signature', while Sr abundance is very low (Sr isotopic ratio is not available yet). Can the sample be of a carbonatite vein? If carbonatite, what could be the reason of its extremely low Sr content? Please suggest me some relevant literature on petrogenesis of such type of carbonatite.
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Carbonatites are rarely only calcite. Is there something else in the vein? What is the host rock? Are there any reaction rims or selvages between the vein and the host rock? Do you have the full composition of calcite?
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I am a new player in the field of SILAC. I am curious whether it is normal to preserve the cells which have been labeled with heavy amino acids?
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I would suggest to add 10 to 20% Glycerol to freezing media otherwise water crystals can break th proteins
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Can any clean plastic and/or glass be used? Thank you.
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Have ever heard of Q411FLD?
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Dear all,
in your opinion, which stabile isotopes and isotope ratios are the most important to measure in the natural clay research, and why?
Thank you and best regards,
Josip
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Oxygen and hydrogen because it is the hydroxyl group that is typical of the entire group of phyllosilicates, sheet silicates or clay minerals.
But be reluctant and abstain from using the isotopes of these elements as a substitute for radiometric age dating, e.g., chemo-stratigraphy.
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I have separate algal and zooplankton samples that I want to have stable isotope analysis of C and N performed on.
The samples were filtered onto 0.4 µm glass fibre filters (GF/F) that were then freeze-dried and stored at - 80 degrees. In error, the glass fibre filters were not pre-combusted or pre-weighed prior to having the zooplankton and algal samples filtered onto them.
Is there a way to still use these samples for stable isotope analysis of C and N? I have read that you can scape the material of the filter paper and then place in a tin foil boat for analysis but don't feel confident in the reliability of this approach.
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Hi !
If you get satisfactory results after checking the blank filters, you can use the scraping method for d15N. Just scrape off the layer of filter paper from behind without disturbing the top layer (avoid any contamination while doing so). For d13C, use a part of filter paper if the content is too high after acid fumigation.
Hope this helps !
Prachi
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Looking for the cooperation from geoscientists having laboratory access/facilities to analyze Oxygen and Sulphur isotopes in delta notation and zircon chemistry by LA-ICP-MS.
The above experimental requirements are a part of exploratory work for probing fertlity status of a newly detected porphyry style mineralization in NE Indian Precambrian shield having all basic signature of mineralization.
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There are several labs in Canada to perform such analyses:
- Canadian Centre for Isotopic Microanalysis, U of Alberta
- Geobiology Isotope Lab, U of Toronto, Dept of Geology
- Isotope Science Lab, U of Calgary
also Carleton Univ. and U of Waterloo
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I've de-fatted some bone samples and analysed the "waste solution" via GC-MS to see how well the de-fatting worked before I gelatinise them. However, I don't know what the expected initial lipid content of bone is in mg/L to determine how much has been removed from the bone. The only publication I could find was by During et al. (2015), and they give the lipid content of bone in g/100g. Are there any publications that refer to the lipid content of bone in mg/L?
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If you obtained a morph of the original bone in the demineralisation step, then the C/N from the isotope analysis is an indication of residual lipids (little N in lipids so C/N will be higher than expected). But beware of poor preservation if the bones are old - that also pushes up C/N. Degraded bones patently do not need defatting. Also beware of incomplete demineralisation. You can also continue GC-MS analyses of successive defatting "waste solution" to determine the diminishing returns.
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The Bayesian methods (e.g. MixSIAR) use the mean and standard deviation of each resource in the estimation of resource contribution in diets.
In my case, I have two main resources: littoral and pelagic.
For the pelagic one, I have only the d13C and d15N mean, resulting in loss of observed variation (SD) for the pelagic resource.
Other resource (multi-sample), littoral, have been processed in order to have the mean and the SD.
Do you know a diet estimation method in line with this case?
Thanks for helping
Best regards
Pierre
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Hi Pierre,
I strongly agree with Pierre Cresson. Searching in literature for stable isotope information of the same resource(s) and adding these values to yours would make your model more valid.
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I am looking for template for the Ti in zircon geothermometer. Can someone help with an excel spreadsheet please?
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[log (ppm Ti-in-zircon) + logSiO2−logTiO2] = (5.711 ± 0.072) − (4800 ± 86/T(K)) (Ferry and Watson, 2007).
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I'm aware of Hydrus and Netpath, but are there others? I am highly interested in water stable isotopes in variably saturated and non-equilibrium flow (double porosity/permeability). Any hints would be deeply appreciated.
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stable Isotopes of Water Vapor in the Vadose Zone: A Review of Measurement and Modeling Techniques
Keir Soderberg et al..
First published: 07 September 2012
Abstract
The stable isotopes of soil water vapor are useful tracers of hydrologic processes occurring in the vadose zone. The measurement of soil water vapor isotopic composition (δ18O, δ2H) is challenging due to difficulties inherent in sampling the vadose zone airspace in situ. Historically, these parameters have therefore been modeled, as opposed to directly measured, and typically soil water vapor is treated as being in isotopic equilibrium with liquid soil water. We reviewed the measurement and modeling of soil water vapor isotopes, with implications for studies of the soil–plant–atmosphere continuum. We also investigated a case study with in situ measurements from a soil profile in a semiarid African savanna, which supports the assumption of liquid–vapor isotopic equilibrium. A contribution of this work is to introduce the effect of soil water potential (Ѱ) on kinetic fractionation during soil evaporation within the Craig–Gordon modeling framework. Including Ѱ in these calculations becomes important for relatively dry soils (Ѱ < −10 MPa). Additionally, we assert that the recent development of laser‐based isotope analytical systems may allow regular in situ measurement of the vadose zone isotopic composition of water in the vapor phase. Wet soils pose particular sampling difficulties, and novel techniques are being developed to address these issues.
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When the stable isotope tracer technology is applied to the soil-plant ecosystem, is there a "regulated" requirement for the sampling time?
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Isotopes and Tracer Techniques for Soil Analysis
Soil Analysis: Recent Trends and Applications pp 69-85 |
  • Manoj Shrivastava
  • P. C. Srivastava
  • S. F. D’Souza
  • Manoj Shrivastava
  • P. C. Srivastava
  • S. F. D’Souz.Centre for Environment Science and Climate Resilient AgricultureIndian Agricultural Research InstituteNew Delhi India
ChapterFirst Online: 08 April 2020
Abstract
Natural and manmade radio and stable isotopes are very useful research tool for soil scientists. Since the nutrient requirements of crops vary considerably with soil type, climatic conditions and plant species, precise knowledge is required on the type, amount, method and time of application of fertilizer materials best suited for specific soil–crop combinations. The availability of isotopes for many plant nutrients such as 13C, 2H, 15N, 32P, 35S, 59Fe, 54Mn, 65Zn, etc. makes it possible for the researchers to explore investigations on soil fertility, nutrient and water use efficiency of plant and soil erosion and degradation and hence provides essential data to develop effective soil and water management strategies to protect soil health and water quality for sustainable crop production.
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For stable isotope analyses of biological components, we normally sample muscle or other soft tissue parts, but for brittle stars, particular for some small sized ones, it seems that we can only sample carbonate skeletons? Any operational protocol to follow, such as acidification. Thanks.
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I attach a few not-very-recent studies that can help choosing a suitable protocol for acidification. Please note that acid washing can affect not only d13C but also d15N values. Thus in some cases it is better to use untreated samples for d15N analysis. Unfortunately acid-washing differently affects d15N in different species and there is no universally applicable methodology. On the other hand, the effect of acid on 15N is usually quite small.
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I am trying to model nutrient uptake and turnover from a long-term experiment. Currently I found a reference to a turnover rate for N used in Burton and Liken's classic study; however, when I asked the authors for the source of their estimate they (1) could not recall, and (2) did not provide a reference in the original paper.
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Dear all,
I am sorry to answer to your question with another question, but I think that you all could actually give me a very good and practical advice here.
Using 13C and 15N, I want to assess changes in diet composition in tadpoles and newt larvae after being exposed to a source of pollutant (with theoretically no direct effect on the consumers). The hypothesis is that the pollutant would affect the density of the sources (not the signature).
My questions are:
-Can we in this case, collect prey and consumers at the same time without really considering tissue turnover of the tadpoles and newt larvae?
-How much would you wait from the application of the pollutant in the water before collecting the animals (considering that in my situation, after max 4 weeks from the application, they will probably develop in adults).
-On the other hand, if you would collect sources and consumers with a delay, how much time would you expected to be necessary between the source and the consumer sampling?
Thank you all, and sorry again for invading your question.
Best regards
Alessandro Manfrin
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I'm analyzing the data and when i calculate the Standard Deviation it's based on the mean of one dataset.
So, what means the precision of the device then for the analytical error?
Guaranteed Precision (1 sigma) at
12,500 ppm (‘Normal’ mode: vapor)
0.12/0.04 Promille for d18O at 10/100 sec
0.3/0.1 Promille for dD at 10/100 sec
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first calibrate sample on VSMOW-SLAP Scale after normalization ignore first two sample results of each replica and calculate their standard deviation. you can also calculate uncertainty using pooled standard deviation formula.
Precision is defined as the standard deviation of the mean of groups of 6 injections over 8 hours.
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I am currently working with EA-IRMS and I repeat my experiment three times for each of my samples. I wanted to know the standard deviation range for my data received by the instrument.
Thank you very much
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I have a problem with EA-IRMS that after running 15N on EA, when switching to run 13C is less stable than usual ===> have to replace left column, how to fix it? Why is the stability of 15N always worse than 13C?
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The investigation of past human mobility and diet using stable isotope measurements of carbon (apatite and collagen), nitrogen, oxygen and strontium is a standardized practice in archaeology. Inter-sample comparisons derived from different labs are usually performed but is not clear if some differences emerging from the use of measurements obtained in distinct laboratories are negligible or on the contrary are significant.
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Thanks Ariana your paper seems quite interesting! I'll read it.
Best
Miguel
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I am currently working on the effects of climatic and vegetational change on mammals for past 15 Ma. I want to ask that how the data of oxygen and carbon stable isotopes can be interpreted in the graphical form. Kindly give your input regarding new software. PS. I have worked on Excel and SPSS but I need an input regarding modern graphical representation trends in Stable Isotope Biology.
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Stellios Tombros
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I was once told that stable isotopes of lighter elements such as H, N C , etc are found in stars, planets, etc. Can anyone suggest any literature which talks about the formation of these isotopes?
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The lightest elements (mainly hydrogen and helium and in trace amounts lithium and beryllium) were formed about 100 seconds after Big Bang through the Big Bang nucleosynthesis (this process lasted up to 20 minutes after Big Bang).
After the formation of stars new elements, from helium to iron, are produced in stellar nucleosynthesis (thermonuclear fusion: CNO cycle, proton–proton chain reaction and triple-alpha process) during stellar evolution.
Elements higher than iron are produced in supernovae through the r-process and s-process.
A very good book about this and generally about properties of stellar interiors and the structure and evolution of stars is: "The Physics of Stars" A. C. Phillips.
About the nuclear physics of stars, you can see also a book of Christian Iliadis "Nuclear Physics of Stars".
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Dear researchers
Pl. suggest the best/recent model or MATLAB code to estimate the paleoaltimetry using stable isotope values. We have long term oxygen and deuterium isotope data.
Thank you
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* Revised paleoaltimetry data show low Tibetan Plateau elevation during the Eocene
  1. Svetlana Botsyun1,2*Pierre Sepulchre1,Yannick Donnadieu1,3, Camille Risi4, Alexi Licht5, Jeremy K. Caves Rugenstein6,7
Science 01 Mar 2019 : Vol. 363, Issue 6430,
Applying stable-isotope paleoaltimetry in greenhouse climates makes the implicit assumption that the factors that control atmospheric distillation and rainfall oxygen isotopic composition (δ18Ow) have remained constant over millions of years. However, the impact of past climate change on δ18Ow values is unclear. In particular, for the Eocene, higher atmospheric CO2 concentration (Pco2) and markedly different Asian paleogeography, including a wide and shallow Paratethys Sea in central China and a latitudinal shift of the southern Tibet margin ~10° to the south, have been hypothesized to modify the Asian climate and regional δ18Ow values. In addition, the carbonate formation temperature is often unknown, increasing the uncertainty in the reconstructed δ18Ow.
We ran climate simulations with Eocene boundary conditions and varying TP elevation. We accounted for changing Pco2, land surface albedo, orbital variation, and sea-surface temperatures, which potentially cause shifts in δ18Ow, by changing the relative contribution of different air masses and the local hydrological cycle—the evaporation-to-precipitation ratio and the fractioning between convective and large-scale rainfalls. In our simulations, the south-shifted location of the entire Indian foreland induces strong convection over the southern flank of the TP and a radically different pattern of water recycling compared with that of present day. Our simulations reproduce monsoonlike seasonal precipitation over the Indian foreland, with summer convective rainfall reaching the TP. An intense anticyclonic circulation during summer months induces widespread aridity on the northern part of the Plateau. This peculiar atmospheric circulation, together with intensified water recycling and multiple moisture sources, results in a reversed isotopic lapse rate across the southern flank of the TP, with the most negative δ18Ow over northern India and increased δ18Ow northward. On the basis of Eocene experiments with varied boundary conditions, we argue that this is a robust feature of Eocene climate over the region. Furthermore, this pattern is the opposite of the present-day δ18Ow over the Himalayas, which decreases with elevation, driven by orographic rainout following a Rayleigh distillation process. Last, using our simulated temperatures and δ18Ow, we derived virtual carbonates δ18O for different elevation scenarios and compared them with the geological record. Statistical analysis shows that a low TP topography during the Eocene is the scenario that provides the best match between model and data.
* Testing stable isotope paleoaltimetry with Quaternary volcanic glasses from the Ecuadorian Andes
Lily J. Jackson Brian K. Horton Bernardo O. Beate Jordon Bright Daniel O. Breecker
Geology (2019) 47 (5): 411-414.
Abstract
Paleoaltimetry provides critical constraints on orogenic processes. Validation of paleoaltimeters enhances confidence in their application to geologic problems and requires investigations of proxy materials formed at known elevations over known time frames. We evaluated isotope-elevation relationships for late Pleistocene to Holocene (220–0 ka) hydrated volcanic glasses deposited over a 4 km elevation range spanning the Pacific coastal forearc and Andean magmatic arc of Ecuador (0°–1.5°S). Reconstructed δD values of paleometeoric water (δDpw) in the glasses decrease systematically with elevation. Holocene δDpw values are similar to δD values of modern meteoric water (δDmw), whereas late Pleistocene δDpw values are 10‰–30‰ lower than both Holocene δDpw values and δDmw values at high (>2 km) elevations. An elevation reconstruction based on δD differences from a modern or late Pleistocene low-elevation datum (ΔδDmw or ΔδDpw, respectively) using a one-dimensional thermodynamic Rayleigh distillation model parameterized with modern temperature accurately predicts Holocene sample elevations but overpredicts elevations of volcanic glass samples that were deposited during glacial marine isotope stage (MIS) 6 by 1–1.5 km. Late Pleistocene sample elevations are accurately predicted by applying a realistic correction for estimated lower air temperature (by ∼5 °C) during glacial MIS 6. This study validates the applicability of volcanic glass δD values in paleoaltimetry studies, underscores the importance of accounting for climate-induced changes in isotope lapse rates when calculating paleoelevations, and suggests that ΔδDpw might be a sensitive proxy for climate change when applied on time scales over which elevation change was minimal.
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its atomic number is not too high. So what kind of mathematical or physical constraint on its nuclear structure breaks it so easily? Why doesn't it have any natural stable isotope?
If it's one isotope with nearly equal neutron and proton number be produced, why that would not be stable?
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The detailed answer is complicated. Basically, the stability of nuclides depends on their number of protons/neutrons and some configuration are more stable then others (analogue to electronic configurations in the atom). So it turns out that all configurations with 43 protons either decay in Mo (42) or Ru (44) because both these elements have a lot of stable isotopes.
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Stable isotopes are defined as non-radioactive forms of atoms and they exist naturally in the nature. I would like scholars to suggest me some literature or any other aid where I can understand how isotopes are formed, in terms of energy levels and how can we create them artificially in the lab environment. Also, how are these stable isotopes more advantageous when compared to conventional element.
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Hello! There is a lot of resources available in the net regarding stable isotopes. I was able to download an old copy of Robert Michener's and Kate Lajtha's book (2nd.ed, 2007 Blackwell Publishing) on Stable Isotopes in Ecology and Environmental Science. It is quite informative and easy to understand.
It might interest you to know that stable isotopes are naturally occurring. So far, I have not encountered a study (maybe my search is limited) making use of stable isotopes for application other than as indicator for certain parameters. Regarding your question on whether these isotopes are more advantageous than conventional elements, it might really depend on what you want it used for.
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I would like to add the stable isotope value or pH for each sampling point into Piper diagram. Would anyone know how to solve it?
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Piper Diagram demonstrates the chemical composition of water. I have a lot of research in the water field, I also read a lot of papers in this field. I did not find any application of pH or stable isotopes in the Piper Diagram
Best Regards An Dang Tran
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In view of the multifarious analytical procedures involved in examining elemental isotopes (C, N, S, O) in different samples (marine water), I would like to know if there is any standard procedure (also include sample storage/preservation techniques and sample pretreatments) to measure stable isotopes in marine water samples. Also, it would be extremely helpful if any experts here are able to share with me some information on how to analyze C13 in organic and inorganic phase using an EA-IRMS. Your generous input is very much appreciated. And calculation methods.
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Thank you sir
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Do you know any study that found a low trophic position inferred with nitrogen stable isotopes for known predatory aquatic macro-invertebrates?
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It depends on the isotopic baseline in your food web. Primary producers can have a very wide range of d15N, and if the predators specialise on grazers which in turn specialise on a low d15N source, their d15N can be very low as well.
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Dear all,
I am trying to understand the diet of different fish parasites using stable isotope analysis. I have indications (isospace) that some of them are feeding directly on the fish tissues, but others on other sources (not fish tissues). How do I correct C13 and N15 for fractionation in this case? Are you aware of studies and /or correction factors applied to fish parasites?
Best regards
Alessandro Manfrin
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Parasites fractionation values in parasites are an interesting area of study. However, they are not well known (to my knowledge) but this paper does look at some cases: Unusual stable isotope fractionation patterns observed for fish host—parasite trophic relationships. If you are trying to correct for fractionation you must rely on published values or controlled laboratory studies.
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For weighing stable isotope samples
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Hi,
The weighing balance from Mettler Toledo (30078800) should do the job. You should perform a calibration before doing the measurements to make sure your measurements are accurate.
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Hello there,
I am in the sample preparation stage for POM C and N stable isotope measurements. Samples of about 10 liters were first filtered through a 200 micron plankton mesh and then filtered at 60 microns to obtain organisms in the 200-60 micron length range. I will obtain the POM by filtering the remaining sample through pre-combusted GF/F filters. But salt crystallization occurs during filtration. I can not remove this salt even though I wash sample by pure water. Do you have a suggestion to remove this salt?
Thank you.
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I'm not sure how well this may help you, but ammonia hydroxide is a good salt remover. I had some trouble with salts forming when I prepared plankton samples for permanent, dry microscope slides, but a drop of ammonia hydroxide prevented salt formation. But, that might be too destructive to your samples. Dialysis worth trying out.
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Hi,
I am using a closed acryl-glass chamber for plant-labelling experiments (12C & 13C). We want to measure 13CO2 and δ13C using Picarro G1101-i. When we tested the air-tight chamber with a plant inside, we got a sudden increase in δ13C (+20) and slowly decreased to normal values (-14) with in an hour. But when we did a backgroud check for the chamber alone without any plant the δ13C values were extremely high (+80 to +150) without any labelling and with new chambers.
Do any one have experiences with Picarro and δ13C weird values in a closed system?
Is there any material (Acryl glass, steel values, butyl rubber) influencing these values?
Let me know if any one can help me to solve this problem.
Thanks alot in advance.
Best regards,
Saranya
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I want to analyse the diets of infaunal invertebrates from a deep-sea methane hydrates site. The organisms had been preserved in 10 % formalin and then transferred to 70 % ethanol for about 4 years now. I know this preservation method affects the carbon stable isotopic signature and, depending on the organisms, the nitrogen stable isotopic signature too. But I'm having some trouble finding information on the literature about the effects of preservation on sulfur stable isotopes.
Thanks!
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Thank you all for your answers!
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D2-glucose, d5-glycerol and 13C2-hydroxybutyrate for continous infusion
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No, the stable isotopes would not dissolve in a saline or distilled water, though the chemical compounds that contain them might.
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Hello!
I am leading a meta-analysis in which I am extracting the mean and errors (SD, SE or CI) from the outputs of stable isotope mixing models. However, stable isotope mixing models can be based on Frequentist and Bayesian stats. So, bayesian stable isotope mixing models outputs rarely show SD/SE/CI. Instead, their outputs are 95% credibility intervals.
My point is: can I use 95% credibility intervals as 95% confidence intervals? If I can not, is it possible to make “the way back” from bayesian parameters to frequentists, converting 95% credibility intervals to 95% confidence intervals?
I have not find any reference on this topic. Any help will be very welcome!
Thank you,
Juliana
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It depends on i) the prior used and ii) how the posterior distribution looks like and the way the credible interval is determined.
If the prior is quite "flat", you don't need to consider it. If the prior is wery informative, it makes a difference and your analysis more complicated.
If the posterior desnity is symmetric and the prior is "flat", then the credible interval is numerically close (or identical) to the confidence interval. If the posterior density is not symmetric and the prior is "flat", then credible- and confidence intervals are numerically similar when the credible interval was determined to leave the same part (2.5%) of the credibility at either side (this is, for instance, not the case for highest-posterior density intervals on skewed posterior densities).
I think it would be more resonable to go for a Bayesian metaanalysis straight away. Instead of trying to find confidence intervals that might correspond to credible intervals, I would try to find reasonable posterior densities for the cases where only confidence intervals were given and combine the posteriors. Only this would tell you what we should believe about the size of the measure, whereas a confidence interval would only tell us what range of hypotheses we would be able to reject for the given (total) set of data.
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I am wondering if moisture content of various pore sizes in soil has different stable isotope composition. Hence I would like to trap water separately from a wide range of matrix potential without a pF pot. Any suggestions?
Thanks.
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Hi Jetse, surely you have to test it, but since they've been used on deep sea sediment cores with over 100m length, it would be worth to give them a try. Sampling pristine pore water is struggling.
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Hi everyone, I am looking for stable isotope studies done with rodents and marsupials from South America.
I only know the work from Dr. Emerson Monteiro Vieira and Dr. Mauro Galetti. Is there any other group working on that?
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Dear Jamile,
Please have a look at these PDF attachments.
Good luck
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I'm doing some work on hydrograph separation using hydrochemical measures. Throughout the literature workers refer to the need to use so called 'conservative tracers' for hydrograph separation. I've always thought of conservative tracers as those chemical species (ions, molecules, isotopes) whose movement is not retarded by interaction with porous media and/or attenuation by biophysical processes (e.g. reduction). Using this criteria Cl, Br and the stable isotopes of water are often referred to as conservative (dissolved Si is also commonly used).
However, when looking to separate a hydrograph into component sources (aquifer, soil and surficial runoff) I see some workers note that the tracers most suited to hydrograph separation are those that are 'conservative with flow.' If a tracer is highly correlated with flow, -/+, then it is better suited to hydrograph separation than one that is poorly correlated with flow. Further, the same workers note that the suitability of a tracer for hydrograph separation varies with the physiographic setting of any given capture zone/catchment, noting it is unwise to assume that tracers suited to hydrograph separation at one site are suited at another.
Conservation of a tracer with flow suggests different concentrations of a given tracer within each key compartment supplying stream flow (e.g., aquifer, soil, surficial zone). In some of the sites I am investigating, Cl and Br are not conservative with flow (i.e., show no correlation) and exhibit little if any meaningful variation in concentration between surficial, soil and aquifer waters that I have sampled. In this setting Cl and Br have proven to be poor tracers of water source. Rather, Total Nitrogen exhibits the strongest correlation with flow (r >0.95), increasing with flow. The increase in TN is correlated with low TN in reducing aquifers, moderate TN in subsoils and highest TN concentrations in 'A' horizon and surficial waters of an intensively farmed catchment. In addition to TN there are other tracers, which are not classically defined as chemically conservative or 'ideal', which are also strongly correlated with flow. These flow conservative tracers also exhibit show strong variation in concentration between the compartments supplying stream flow.
Consequently, I'm tending towards the definition that the most suitable tracers for hydrograph separation are those that are strongly correlated with flow (r >0.9).
I was wondering if anyone else has addressed this issue as it appears there is conflicting definitions of what constitutes a conservative tracer when looking at stream hydrograph separation?
Kind regards,
Clint
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I agree with your definition Clinton of conservative solute tracers as those that move through the system during the time frame of interest with little attenuation or transformation through biogeochemical processes. Exploring linearity of lack thereof among various solutes is an informative approach in this regard. I would also urge you to read the paper by Hooper, 2003, WATER RESOURCES RESEARCH, VOL. 39, NO. 3, 1055, doi:10.1029/2002WR001528 where he discusses various diagnostic approaches to explore when applying mixing models. Another issue to consider is whether there is a significant difference in concentrations of the solutes you are applying in the mixing model among the components that make-up streamflow. In your case, it may be baseflow/slow flow and rapid runoff/interflow, though some systems have a readily identifiable third source of runoff such as overland flow. Hooper mentions that there can be much more complex models as well with 4, 5, or more mixing components if justified. A final topic of discussion you raise is preference for selecting solutes that are correlated with flow. This is also an important consideration, and I would offer that obtaining satisfying model results is facilitated when the solute(s) of interest show predictable correlative behavior as streamflow rises and falls. However, it is not necessary to have this condition in order to have a successful mixing model solution, as long as there are significant differences in concentrations among the solutes for the various components of the hydrograph separation. Finally, examining the behavior of solutes that are not conservative relative to the behavior of those that are can be quite informative and may suggest the importance of biogeochemical processes within the context of your system.
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Dear friends,
The question as I said in the title, I'm not sure about what problems we will get in troubles, If we use the stable isotope approach.
I hava already read some papers about the fish stocking migration between the different habitats.
I think the most problem is that the different tissues hava the different rate of metabolism, for example, the liver and blood cell have very fast rate, just few days, and the white muscle, fin, or bone of fish can present a long period of feeding habit, and the stable isotope values can present previous habitat information. Moreover, the size of fish we collect may be also can influence the result of the stable isotope values, but I'm not sure about it.
you guys can give me some suggetions or advices about the question as much as you konw, if so, thank you very much.
Regards,
Xie Bin
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Hello, your question is very general, the problems in the use of isotopes will depend on the type of isotope you are using. I recommend that you read this book that will help you answer all your questions.
Hobson, K. A., & Wassenaar, L. I. (2008). Tracking animal migration with stable isotopes (Vol. 2). Academic Press.
Viljoen, G. J., Luckins, A. G., & Naletoski, I. (2016). Stable Isotopes to Trace Migratory Birds and to Identify Harmful Diseases: An Introductory Guide. Springer.
I send it to you in attached
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In aquatic ecology research, the relationships between different trophic level are important. Stable carbon and nitrogen isotopes analysis(SIA) are widely used to ravel the interactions between linkages in food web.
The biomass and quantity of top level organisms in food web are always low, and the collection metod requires dead individuals, and which could collect tissue samples easily.
Currently, a large proportion of top predators are rare or threatened. Few articles use the non-lethal methodologies which collect the blood or fins.
Why the non-lethal method is not widely used?
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Such methodologies are widely used, but the resolution is poor. I spent several years doing a master's using fatty acid analysis to differentiate between food sources in Atlantic Tarpon in the early 2000's. It worked...sort of. Here's the thing, fatty acids in tissue are not just diet-related, they're biosynthesized and utilized at different rates based on physiological changes & stresses to the organism. The best paper at the time was produced by a lab in the far white north, and there was so much mathematical black magic used in the paper that few people who were doing the work at the time believed them.
Isotope work is even more vague than fatty acid analysis. Okay, as Sharon pointed out, sharks may feed in marine and freshwater biomes...but what does that really tell you? Not much! A gut-content study (they can be done non-lethally) can tell you what species are consumed specifically, rather than...over the last year or two the shark fed on saltwater and freshwater organisms. For example, gut content studies in Florida in the 1970's (I believe 1977) found that alligators were feeding on a variety of native fish, turtles, and mammals. The lab I worked in did a preliminary study in the mid-2000's on alligator diet using gut-content analysis and discovered that their diet had switched to 95% exotic fish species. Would an isotope study been able to catch the change? I'm not sure, but I know it's much cheaper and more accurate to have students sort through the stomach contents of an alligator to see what it ate compared to using fatty acids or isotopes to calculate a ratio. What are tiger sharks eating in SW Florida estuaries? Probably saltwater and freshwater organisms when they can get them. But the 8'1" tiger shark I examined had eaten saltwater catfish and batfish. That's more interesting than a vague trophic-level analysis.
Isotope and fatty acid analysis can be good tools IF you are only examining higher-level trophic interactions. If you want fine details, stick to the old, dirty, stinky, disgusting methods that work.
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Stable isotope analysis
When we collect fish muscle samples, some kinds of fishes have lots of intermuscular bones, especially less evolved fishes, and they are hard to remove.
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Probably the simplest approach is to use acidification with 1M HCl to dissolve inorganic carbonate from the bone. This can be done after the samples have been dried or freeze-dried and ground to powder for analysis.
Some authors do find that this procedure does not significantly change the d13C value for fish muscle samples though, so it may not be necessary:
Something to be careful of, is that the acid treatment will also affect the d14N and possibly other isotope ratios as well. If acidifying samples, it is advisable to analyse duplicate samples with and without the acid treatment.
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Adding oxidising agent removes organics form the sediment. Will it affect Mg/ Ca ratio or any other data?
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Since you plan to apply carbon dating, I assume you are dealing with rather unconsolidated sediments that you can wash and sieve with distilled (or tap) water. If the washed residue is not loaded with organic debris - foram residues rarely are - the specimens can be easily picked. One simple rule: avoid chemicals in the processing when there is no real need for using them. For the disintegration of shales and marls we generally use a simple soda solution, but for unconsolidated clays tap water is mostly sufficient.
Never use diluted hydrogenperoxide (H2O2) for processing organic-rich and pyrite-rich sediments as sulfuric acid will be formed. This will partially dissolve and probably to some extent leach the tests. See also the paper by Kennedy & Coe (2014 - Journal of Micropalaeontology) on this problem.
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How to add stable isotope labeled internal standard in samples, does anyone have this kind of protocol?
I need to add IS just in QC or all samples during sample (plasma) preparation ? only one IS is enough or I need a combination of ISs ?  
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Just for metabolic profiling at this moment, we are interested in lipids, amino acid and also glucose metabolites
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Can anyone suggest me, how to use stable isotopes viz., deuterium and oxygen-18 in transport contamination modelling by the aid of Visual MODFLOW Software and the study pertinent to coal mine impact assessment of groundwater regime. Also, please share relevant papers or information.
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I am studying diet in weakfish using stable isotope analysis and I am wondering if performing analysis on the sediment is necessary for the purpose of identifying prey items. 
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 Hi Brian
I think I need more information to provide a useful answer. However, consider C isotope analysis in particular for a moment. Analysis of gut contents will produce C isotope signatures. The signature will depend on the signatures of the various gut contents and the amount of each of the various materials (prey and perhaps other components) present in the gut content (sub)sample. If you are blending (homogenising) total gut contents the same reasoning applies however subsamples taken from the homogenised gut contents should all have the same isotopic signature (within the precison of the mass spec used to measure the isotopes, which depends on the standards samples used - what kind of mass spectrometer are you using?).
Now regarding the prey or rather the C isotopic signature of the prey. It will depend on what they eat. Their signature should reflect the signature of the food items they eat x the amount of the different food items they eat (then it depends on what each prey animal assimilates, ie digests and absorbes and incorporates into structures). This is starting sound like I am deliberately making it complicated but what underlies a simple C isotope value is complicated.
However, if say one type of prey item were separated from the gut contents of fish from one location and analysed then compared to similar subsamples from another location then the environment (ie sediment) might have a noticeable effect on the particular prey item's C isotopic signature. But note that there are many different effects possible and they need to be considered and accounted for (in clever ways) to make sense of such differences between isotopic signatures from different locations.
I think the above is only partly relevant to your actual question though. Unfortunately I am unsure of what you are measuring, the fish tissue, the gut contents, or the typical prey that the fish typically eat? The isotopic signature of the fish tissue (same type of tissue subsampled for each spawning location) should reflect that of the prey they have eaten (ie diet) and the amount. If you are measuring gut contents then does it comprise specifc prey items retrieved from the gut contents (and the same prey items across sites) or the total gut contents? The 'typical prey' might say include more than one prey species and if so the fish isotopic signature should reflect the signature of the multiple prey items x the quantity of each prey item (I'm deliberately being repetitive to that outlined above - I don't know how much you know). For example,
"Weakfish feed on a wide variety of animals, including crabs, amphipods, mysid and decapod shrimps, squid, shelled mollusks, and annelid worms, but chiefly on smaller fish, such as menhaden, butterfish, herring, scup, anchovies, silversides, and mummichogs, of which they destroy vast quantities. The precise diet varies with the locality (that is, with what is most readily available), but small menhaden are probably the most important single item. " http://www.gma.org/fogm/Cynoscion_regalis.htm
With such a wide variety of prey items I wonder whether isotope analysis is going to be helpful. Some studies analyse chemical compounds (composition) in the rings of otiliths which generally correlate with size (age) of fingerling or juvenile fish. Scales can also be used. The isotopic signature of sediments at different locations might be different and might correlate with the isotopic signature of fish tissue samples, if you are lucky. Perhaps the thinking is that fingerlings eat small animals whose isotopic signatures are close to that of the sediments. How much the isotopic signature of sediments differ might be worth establishing before launching into a big campaign.
If you want to be more specific it might help refine the answer.
Best of luck
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This Bosmina was found in Arenal Reservoir, Costa Rica. It is apparentl infected by a fungi, and we are interested to know if there is any experience about this condition, and if ti means something about the environmental condition of the lake.
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You're welcome Dr. Gerardo
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I have data  dD and d 18O and wish to calculate the monthly weighted means
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It is still impossible to answer this as you have not explained what you are measuring.
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I want to send seawater samples for isotopic analyses of N2 and dissolved inorganic carbon to know the enrichment after experiments with 15N2 and H13CO3. I appreciate if anyone know any isotopic analysis lab that does service for MIMS in North America where I could send my samples from Mexico.
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Thanks Fernando. When I ask them a few weeks ago, they said that UC Davis is not doing this analysis (MIMS) any more since a year.
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I have an undetermined stable isotope (SI) trophic model with 2 tracers and 5 sources for a consumer (mix). To address this undetermined model I applied the mixSIR.unknownGroupsR function (http://conserver.iugo-cafe.org/user/eric.ward/Mixing%20model%20with%20unknown%20groups) to combine sources into groups and estimate the proportional contributions of the resultant grouped sources to the consumer (Ward EJ, Semmens BX, Phillips DL, et al (2011) Ecosphere 2:art19. doi: 10.1890/ES10-00190.1). Among the input data required by the R function are: a matrix with the consumer SI data (X); a matrix of raw source SI means (u); a matrix of raw SI source variances (v); and a matrix of sample sizes (k). However, the unknownGroups.R. function does not require the input of a matrix of means (and variances) isotope fractionation values (i.e. trophic fractionation or discrimination) for each of the sources used in the model, as usual in other mixing models (e.g.: mixSIR, SIAR, MixSIAR, FRUITS).
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Hi Hari,
I set the initial threshold to 0 (inputThresh=0):
mixSIR.unknownGroups(X, u, v, k, n.sir, inputThresh=0, …)
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We want to know sampling techniques and frequency for groundwater samples (karst aquifer). In addition, where it is possible to analyse those isotopes.
We really appreciate any kind of help.
Thanks a lot
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Dear Mushtaq, thanks a lot  for the link, we had already.
Thanks
Juan
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Ihave a fossil wood, t want to do 13C isotope. So i want  to groove 20 to 50 sampled in the fossil wood about 2 mm wide.
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Use a low speed diamond saw with dual blades and a 2mm spacer. It will cut out a wafer which can be broken into samples. The drill was a good idea too.
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We are looking for a partner or a provider for stable isotopic analysis (S, C and O or any of these) on pore water and water column. 
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PLEASE  ASK DR E. KEREPERTZIS DEPARTMENT OF GEOLOGY
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How using stable isotope for detection of soil contamination?
using isotopes N , O , C , Sr , & ..... for detection of soil Contamination and monitoring and purification?
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Additional link from IAEA
On stable ground: tackling soil erosion with nuclear techniques in Viet Nam
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We want to use scales of fish to follow the variations of Delta O18 . However, these fish are archived in Formol/Formaldehyde during some years and so we have a question " What is the effect of preservative as Formol/Formaldehyde on the analysis of Delta O18 ?"
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On the bioapatite "mineral fraction", we must do a test "fish in preservative as Formol / Formaldehyde", but I think that the isotopic analysis in 18O is always valid.
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I am collecting insects in a forest environment, and looking at the delta Carbon and Nitrogen ratios of different insects in the system (and using it in my bird-related study). However, I need to kill the insects in a Malaise-like trap (but do not feel comfortable using arsenic). I have heard that preservatives such as ethyl alcohol may alter the isotopic values in insects collected. Does anyone have any suggestions on how I can preserve the insects in the collection jar without altering the isotopic signatures? Thanks!
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Hi Francisco.
I appreciate the answer! I have a follow-up question, and wonder whether you could help me by any chance... is there a way to modify the capture section of a malaise trap to let it capture insects live (instead of using ethyl alcohol, as I was planning, or arsenic)?
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Most commonly used isotope in plant is N15 for determination of nitrogen uptake, but why not N14? Is there any possibility to use both isoptopes at same time??
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The use of nitrogen isotopes typically uses both 14N and 15N.  The ratio of 15N/14N as expressed as a ratio against the standard ratio in atmospheric air which is arbitrarily set at 0 permil.  
A not to recent literature review can be found in:
A preliminary study of the carbon and nitrogen isotopic biogeochemistry of lacustrine sedimentary rocks from the Green River Formation (Collister and Hayes, 1991)
Best Regards,
James Collister
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I need to talk with someone who's actually done stable isotope analysis and used SIAR, preferably in the NYC area (I may need hand holding)
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No idea, Russ, sorry
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In the paper of Roberts (2012, GR), the mean curve of εHf(t) is recalculated so that it represents the percentage of depleted mantle input within an available range, with this range being based on the depleted mantle value plus two epsilon units for the maximum, and an evolution line from 4.56 Ga using a crustal Lu/Hf value of 0.015 for the minimum (mantle–input curve in Fig. 1); this mantle input curve is plotted with the mean of the Hf data as zero (Details see in the attachment). However, I still have no idea how to calculate such curve. 
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Roelant Joost Van der Lelij,
Thanks your reply
Zongying
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I have been monitoring the δ15N of two species of floating plants over 5 concentrations of NO3 and NH3.
The measurements have been done over 16 days, with solution changes every 7 days to avoid nutrient limitation.
The idea was to look at the time integration period of these plants and the rate of change in δ15N ratios level out around day 12 – suggesting plants are then at approx. isotopic equilibration with the solutions.
All plants were grown in a green house, with pH between 6-7.5, a 12:12 light dark regime, temp 20-22 deg C, with adequate phosphorus and iron.
The problem:
In both species, for both NO3 and NH3, if I calculate fractionation between day 12 plant δ15N and the source δ15N at each concentration I see a pattern of increasing fractionation with lower N availability.
So effectively there seems to be an inverse relationship between fractionation and concentration.
This was the exact opposite of what I expected, as I thought that when there was limited N, plants took it up without much differentiation, but at excess N, plants could be choosier about taking 14N over 15N = more fractionation).
I feel like I am missing something obvious and wondered if anyone had some “off the top of their head” ideas as to why I might be seeing this?
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It might help if we knew whether the NO3 and NH3 treatments were separate or combined, and how you prevented oxidation of ammonia.  You say the P and Fe were adequate.  How do you know?  What about other nutrients? 
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The analyses of stable isotopes δ2H and δ18O have great significance in the groundwater studies, particularly to understand the mixing of surface and groundwater. How the stable isotope studies help in comprehending the mechanism of fluoride mobilization in groundwater?
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All waters have "fingerprints" of naturally occurring isotopes that provide information about their origin. Among the most powerful and cost-effective fingerprinting tools are the ratios of stable isotopes of hydrogen--deuterium to hydrogen (D/H)--and of oxygen-18 to oxygen-16 (18O/16O). For example, the D/H and 18O/16O ratios in precipitation vary according to elevation and distance from the ocean. An altitude difference of 250 meters produces a clear and measurable change in the two ratios, which is preserved once the precipitation infiltrates to the aquifer.
The stable (2H, 18O) isotopes in integration with radioactive (3H, 14C) can provide detailed insight into and assess the mean groundwater recharge in river basins, regional groundwater flow velocity and residence time, contamination characteristics, flow-paths of intermixing, and identification and delineation of recharging zones and protection zones in the aquifer system. The D/H and 18O/16O ratios can be used also to discriminate among multiple water sources within an aquifer.
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I just know d-excess is used to trace moisture source conditions (RH, temperature etc.
Any other advantages (in atmosphere, surface or subsurface water cycle)?
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If you have repeated measures of D and O-18 at a site, then you can easily calculate D excess, since this is defined by the relation: D excess = d2H - 8 * d18O as first described by Dansgaard, 1964 (Tellus 16: 436-468). The D excess values of precipitation can provide insight to sources of moisture, atmospheric processes, and relative humidity (Merlivat and Jouzel, 1979, J. Geophys. Res. 84: 5029_5033). Time series of D excess values can inform understanding of how climate change may be impacting geographic source areas of precipitation (Puntsag et al., 2016, Scientific Reports, DOI: 10.1038/srep22647). D excess is also interesting to understanding the local water balance as reflected in surface waters and groundwater (Kendall and Coplen, 2001, Hydrol. Proc. 15: 1363-1393). Comparison of the local meteoric water line from precipitation with that obtained from local surface and groundwater can provide insight to ET as D excess tends to decrease with evaporative intensity. It is also important to consider other sources of moisture/recharge such as fog and cloud water, which can be locally important in coastal areas and in mountainous regions. My advice is that if you are measuring D and O-18 of precipitation and local waters through time, then develop the regression relationship for the local meteoric water lines of these respective waters and examine the D excess among other facets of these relationships. This may provide insight to ET, sources of recharge, and other elements of the water balance.
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Dansgaard [1964] say that if the evaporation takes place under non-equilibrium conditions, e.g. fast evaporation, the evaporating surface water probably has a negative d-excess. Besides, relatively low mean condensation temperature for the heaviest rain (i.e. very high clouds) also cause a negative d-excess. If so, the heavy rainfall from tropical cyclone (very high clouds) hereby has a negative d-excess. Am I right? If yes, will the surface seawater have a negative d-excess due to the heavy rainfall? For example, tropical surface seawater suffering from heavy rainfall in the ITCZ?
Note that negative d-excess in seawater of the Mexico Gulf (-3 ‰), especially Mediterranean Sea (lower to -9 ‰) from attached Figure [Schmidt et al., 2007JGR], as i understand it, it may be ascribed to the annual precipitation of Mexico Gulf is more than 1000 mm and the intense evaporation (non-equilibrium) in the Mediterranean Sea, respectively. Is it right?
BTW, can anyone send me some literature about d-excess of the seawater? Thanks a lot!
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I think the negative d-excess in surface seawater is related to the intensity of sea surface evaporation, not precipitation. We know that the volume of precipitation is very smaller than the volume of sea.
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The isotopic composition of organic tissue of a specie of deep-water coral will be considered to evaluate the efficiency of food uptake under controlled conditions in a microcosm.
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Hi Renato. Did you try to use ultrasound bath?
We put coral pieces in eppendorfs with buffer or milliQ water, and put it in an ultrasound bath for some minutes to separe tissue from skeleton.
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Can anyone help me in interpretation of these graphs.  
I'm beginner in using CWT for paleoclimates, I need help from experts. 
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Yes, I agree that the above recommendation for the article written by Torrence and Compo (1998) is a helpful article. However, to interpret the scalogram (the 2-D plot of time vs. frequency where the contour of power, the lower of the two plots you showed) one needs to know the shape of the wavelet used to generate the coefficients contoured in the scalogram. For instance, if one used the Morlet wavelet (sinuoidal), then the red zones in the plot would indicate the time and frequency that have sinusoidal components. However, if a different wavelet was used, then the interpretation would be different.
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I am using GAMs in mgcv to look at relative stem densities and weights for a paired dataset (control and treatment) stem data for each sampling location. Should my response variable be, for example, the stem weight ratio of treatment/control or instead, would it be more appropriate to have the treatment stem weight as the response and include the controls stem weight as a co-variate?  
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Hi John,
It's usually best to model the raw data, which in this case is stem weight with control/treatment as a covariate. It can also be easier to choose what distributional assumption you want to make about your error structure of the raw data. For example the error structure of weight will likely be best described as a log-normal distribution. On the other hand, what is the distribution of the error structure of a derived ratio between two log-normal distributed weights......not quite as clear.
Wish you well,
Dan
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Dabundo et al. reported significant contamination of commercial 15N2 gases available, especially the gases supplied by Sigma Aldrich:
The Contamination of Commercial 15N2 Gas Stocks with 15N–Labeled Nitrate and Ammonium and Consequences for Nitrogen Fixation Measurements (Dabundo et al. 2014, PLOS one)
I would be interested if anyone else of this community experienced similar problems and/or how suppliers reacted to inquirie.
Gases of Sigma Aldrich are for example not tested for such contamination, as the company stated upon request. Without testing of each batch, the use of gases of SA cannot be recommended then. As there was no reaction of SA upon release of the mentioned article, the support policy of SA also seems questionable and not what I would expect from a supplier of scientific products.
What is your experience and your recommendations of suppliers?
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Hi Klaus-Holger,
we are using the 15N2 labelling in my lab, since the publication of the Dabundo paper we checked our gases for contamination and it turns out that Campro gases and Cambridge isotope gases were not contaminated since then. In addition to the contaminatio nissue, SA gases are very expensive- so I personally buy now from the other two suppliers..
Best,
Carolin
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I am looking for carbon stable isotope values for xylitol, in an attempt to understand the variable sources of the sugar. I cannot find anything that is published on raw values, or of the relationship between the isotope value of xylitol and its source (e.g. birch bark). Any help (including unpublished data) or comments would be appreciated.
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Might look here too:
The organization might be able to help as well. Most of the studies are using 13C markers, but they must know what "normal" values are to understand the isotope mass balance to make sense of their data.
Hope this helps!
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Question is just as title above.
I have checked that no leak of gas occurred. Generally the value of 29N2 background intensity should be lower than 50 ml/min after machine is in stable situation,so 100mv is too high, and I must paused my analysis procedures. But, why 29N BGD value is so high? And how to fix it on isodat workspace of EA-IRMS? 
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Dear Weiping Mei,
hope your case had been resolved. But if you have further technical problems with IRMS, you can go to http://isogeochem.wikispaces.com/ and qet friendly and professional support from colleagues. Start from searching archives that contain virtually all possible questions and answers.
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Hi,
for an review I am looking for publications that deal with the elemental or stable isotope composition of sea urchin spines (any taxa is welcome). As a good starting point I have choosen Carter´s book on Skeletal Biomineralization - accordingly papers should not be older than 1990. Thank you in advance!
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Cool findings. Thank you Nils!
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I am wondering is it a clear process or more complex? And is the isotopic composition constant for example the d15N value of NOx from gasoline or coal combustion and the d15N-org of lichen thalli is the same?
I will be grateful for any answer or references.
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So I’ve been recently trying to find studies conducted on the possibilities to Amino Acid-date corals. So far I have only found studies that have looked into determining the age of Porites (Erica J. Handy et al., 2012) and Acropora palmata individuals (P. J. Tomiak et al., 2016). I would however be interested in using A. pruinosa individuals, as this is the most abundant species in my field study. I would be using the intra crystallised proteins to analyse the D/L ratio for a few amino acids.  
The main reason why I would be using the AAR method compared to U/Th or Carbon dating is the prices. AAR would be more suitable to my sediment core sampling as I would like to date quite a few samples and Carbon dating would be way too expensive for multiple dating’s. The Uranium Thorium dating method would be also suitable but this method has not proven to be liable in previous studies where I’m working at the moment. Would I however have to carbon date calibrate the A. pruinosa individuals before I start using the AAR method to date all my samples? Or is it possible to determine the ages just based to AAR analysis?
I’m also treating my samples with 60 ° C prior to analysing them. This is because I dry them in the oven after retrieving a sediment core and after the material is sorted. I dry my sample for 48 h, but will this affect the racemization analysis and result? My sample are also collected from the sea floor usually at a 5 m depth. The cores are usually around 40 cm long and I would be dating the bottom, middle and top part of the core using the same species.
Articles:
P.J. Tomiaka, M.B. Andersena, b, , , E.J. Hendya, c, E.K. Potterb, K.G. Johnsond, K.E.H. Penkmane. The role of skeletal micro-architecture in diagenesis and dating of Acropora palmata. Volume 183, 15 June 2016, Pages 153–175
Erica J. Hendy, Peter J. Tomiak,a Matthew J. Collins, John Hellstrom, Alexander W. Tudhope, Janice M. Lough, and Kirsty E.H. Penkmanc. Assessing amino acid racemization variability in coral intra-crystalline protein for geochronological applications. Geochim Cosmochim Acta. 2012 Jun 1; 86(9-2): 338–353.
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Hi Stefan,
In past unpublished studies, I have attempted to determine relative ages of corals using AAR, but have found the results to be far more variable than either mollusks or whole-rock sediment samples.  That said, if the samples are well preserved chemically and mineralogically, and from clear stratigraphic context, it might be worth a pilot study.  AAR will provide only relative ages, but should be able to distinguish Pleistocene from Holocene age samples.  A substantial database of radiometrically calibrated AAR samples would be needed to estimate numerical ages. 
Samples must be air dried and not oven heated to yield reliable results.  The temperature history of the ocean floor location might be available through other proxy methods.  
Best regards,
Paul Hearty
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I now extract 20 gram soil by hot/cold water by 30 mins shaking and 30 mins centrifuge. One of the parameters for analysis is δ 13C. I need to freeze dry extract to get the solid matter for measuring. However, after 1st extraction, the volume of extraction seems to be too little, that's why I want to do 2nd time extraction by adding water again. Anyone has experience on this field? Many thanks.
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You must try doing both because the answer may be soil dependent
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In wetlands terrains, impermeable clay layers are usually found above the sandy aquifer (s), it is neccessary to determine if the groundwater in the aquifer is recharged from vertical pentration of surfcae water or from lateral flow from a nearby (upper stream) region.
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Dear Dr. Zhonghe,
It's as simple as expressed by Dr. Jorge above and more in details by Dr. Ebrahimi previously. You just have to measure the isotopic signature of each end-member in your system (wetland) as well as that of precipitation. Applying the mass conservation equation you would become able to compute the percentage of recharge from any component (end-member) that might contribute to recharge of your groundwater anywhere within your studied aquifer. Chloride being a conservative tracer, you could also use it in combination with isotopes (plotted vs. O-18 for instance) to assess in depth what could be happening within your system.
All the best...