Tatiana Betson - Academia.edu (original) (raw)

Papers by Tatiana Betson

Publication list Introduction Stable isotopes General considerations Definitions Mechanisms of is... more Publication list Introduction Stable isotopes General considerations Definitions Mechanisms of isotope fractionation 1) Physical fractionations 2) Chemical fractionations Isotopomers Measurements of isotope and isotopomer abundance 1) IRMS 3) FTIR 2) NMR Climate change Open questions Tree rings as a proxy for climate (dendroclimatology) 1) Physical characteristics of tree rings 2) Chemical characteristics of tree rings Persistent organic pollutants in the environment Definition Identification of their origin and fate Results and conclusions Paper I Paper II Paper III Paper IV Unpublished results related to Paper IV General conclusion

EGU General Assembly Conference Abstracts, Apr 1, 2009

Abundances of deuterium (D) and 18O in precipitation carry climate signals. Both isotopes are inc... more Abundances of deuterium (D) and 18O in precipitation carry climate signals. Both isotopes are incorporated into leaf photosynthate, and in a second step into tree rings. Strikingly, while D and 18O climate signals in precipitation are related, tree-ring records of both isotopes do not generally go in parallel. This contribution investigates this discrepancy, based on a comparison of the fractionation mechanisms for both isotopes. We present a strategy to detect plant acclimation on time scales of centuries from intramolecular deuterium distributions (D isotopomers). We showed recently that specific C-H groups of glucose units exchange with water during cellulose synthesis in tree trunks, in agreement with the biochemistry of cellulose formation. Most importantly, this result allows separating influences of source water and of D fractionations in the plant, and hence to isolate climate signals and physiological signals. NMR measurements of intramolecular D distributions of glucose demonstrate that each C-H group has a distinct abundance (each D isotopomer), corresponding to its unique biochemical history, and can serve as independent information channel. Therefore, isotopomers increase the information content of isotopes several-fold. Thus, using D isotopomers, a situation may be achieved where experimental quantities overdetermine the number of variables to be reconstructed. This increased information content can be retrieved along the following strategies. Similar to C-O groups that exchange during cellulose synthesis, D isotopomers of C-H groups which heavily exchange should adopt the D abundance of source water and associated climate signals. We will present tree-ring results that support the feasibility of this approach. C-H groups that are not affected by isotope exchange are passed from leaves to the trunk, and can therefore transmit leaf-level information to tree rings. On the leaf level, overall D abundance of photosynthate is influenced by transpiration, but individual D isotopomer abundances are ultimately set by enzyme isotope effects. In tree-ring cellulose, abundance differences between exchanging and non-exchanging isotopomers reflect evaporative enrichment and may be exploited to reconstruct humidity. Finally, we have shown that abundance ratios of non-exchanging D isotopomers are wholly determined by biochemical isotope fractionations, independent of source water. Consequently, isotopomer ratios represent signals of leaf-level metabolic regulation, which are deposited in tree rings. For example, one isotopomer ratio responds to the CO2 concentration during photosynthesis. This effect reflects CO2-induced changes of the metabolic flux ratio of photosynthesis versus photorespiration. Photorespiration reduces the efficiency of photosynthesis, therefore this isotopomer ratio may reveal plant acclimation on time scales of decades, and associated trends in plant productivity. Combining signals reflecting metabolic regulation with climate signals opens the possibility to study acclimation of plants to increasing atmospheric CO2 and concomitant climatic changes, on time scales of decades and centuries.

Analytica Chimica Acta, Sep 1, 2006

The δ 2 Hand δ 13 C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the c... more The δ 2 Hand δ 13 C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and-anisoles. δ 2 H-values ranged between −235‰ and +75‰ whereas δ 13 C-values were found in the range −22‰ to −38‰. No correlation between δ 2 Hand δ 13 C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution. 2 H NMR was used to quantify abundances of 2 H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the δ 2 H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the δ 13 C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in 2 H with increasing degree of chlorination. Different δ 2 H-values of the starting material will also impact the δ 2 H-values of the chlorination products.

Chemical Geology, Jun 1, 2008

The deuterium (D) abundance of tree-ring cellulose archives past climatic conditions, but previou... more The deuterium (D) abundance of tree-ring cellulose archives past climatic conditions, but previous attempts to access this archive have led to conflicting results. Based on an overview of D fractionation mechanisms in plants, we explain why past measurements of D abundance yield ...

Proceedings of the National Academy of Sciences of the United States of America, Dec 7, 2015

Terrestrial vegetation currently absorbs approximately a third of the annual anthropogenic CO2 em... more Terrestrial vegetation currently absorbs approximately a third of the annual anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However,terrestrial net primary production is highl ...

This thesis describes the development and the use of quantitative deuterium Nuclear Magnetic Reso... more This thesis describes the development and the use of quantitative deuterium Nuclear Magnetic Resonance spectroscopy (NMR) as a tool in two areas of environmental research: the study of long term climate-plant interactions and the source tracking of persistent organic pollutant. Long-term interactions between plants and climate will influence climate change during this century and beyond, but cannot be studied in manipulative experiments. We propose that long tree rings series can serve as records for tracking such interactions during past centuries. The abundance of the stable hydrogen isotope deuterium (D) is influenced by physical and biochemical isotope fractionations. Because the overlapping effects of these fractionations are not understood, studies of the D abundance of tree rings led to conflicting results. We hypothesized that both types of fractionations can be separated if the D abundance of individual C-H groups of metabolites can be measured, that is if individual D isotopomers are quantified. The first paper describes a technique for quantification of D isotopomers in tree-ring cellulose by NMR. The technique showed that the D isotopomers distribution (DID) was non-random. Therefore, the abundance of each isotopomer potentially contains individual information which suggests an explanation for the conflicting results obtained by measuring the overall D abundance (dD). In the second paper, this technique was used to study hydrogen isotope exchange during cellulose synthesis in tree rings. This revealed that some C-H positions exchange strongly with xylem water, while others do not. This means that the exchanging C-H positions should acquire the D abundance of source water, which is determined by physical fractionations, while non-exchanging C-H positions of tree-ring cellulose should retain biochemical fractionations from the leaf level. Therefore, the abundance of the corresponding D isotopomers should contain information about climate and physiology. When analysing tree-ring series, the DIDs should reflect information about temperature, transpiration and regulation of photosynthesis. In the third paper, we showed that CO2 concentration during photosynthesis determines a specific abundance ratio of D isotopomers. This dependence was found in metabolites of annual plants, and in tree-ring cellulose. This result shows that D isotopomers of tree-ring series may be used to detect long-term CO2 fertilisation effects. This information is essential to forecast adaptations of plants to increasing CO2 concentrations on time scales of centuries. In the fourth paper, the source of persistent organic pollutants in the environment was tracked using DID measurements. The dD values of two compounds of related structures were not enough to show indisputably that they did not originate from the same source. However, the DIDs of the common part between the two compounds proved that they did not originate from the same source. These results underline the superior discriminatory power of DIDs, compared to dD measurements. The versatility of DID measurements makes them a precious tool in addressing questions that can not be answered by dD measurements.

(A) Chemical structures and whole-molecule δ2H values. (B) Overla... more (A) Chemical structures and whole-molecule δ2H values. (B) Overlay of deuterium NMR spectra of reference samples of p, p′-DDD (black, reference 1) and p, p′-DDT (red). Integrals of the signals are proportional to the abundance of the respective 2H isotopomers. Ar-2H denotes isotopomers carrying 2H in the aromatic moieties of the respective compound. Positions of signals (“chemical shifts”) differ between DDT and DDD because they reflect the stereoelectronic properties of each molecule; these chemical shift differences do not influence the integration of signals.</p

[a]Relative to C2HR2 = 1.[b]<... more [a]Relative to C2HR2 = 1.[b]from reference <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110648#pone.0110648-Armbruster1" target="_blank">[23]</a>.[c]See Materials and Methods for calculations.Deuterium abundance data of DDT and related compounds.</p

Regulatory Toxicology and Pharmacology, 2019

Investigation of number of replicate measurements required to meet cigarette smoke chemistry regu... more Investigation of number of replicate measurements required to meet cigarette smoke chemistry regulatory requirements measured under Canadian intense smoking conditions, Regulatory Toxicology and Pharmacology (2019), doi:

Regulatory Toxicology and Pharmacology, 2017

Analytical Chemistry, 2006

Proceedings of the National Academy of Sciences, 2015

Significance Decadal-scale metabolic responses of plants to environmental changes, including the ... more Significance Decadal-scale metabolic responses of plants to environmental changes, including the magnitude of the “CO 2 fertilization” effect, are a major knowledge gap in Earth system models, in agricultural models, and for societal adaptation. We introduce intramolecular isotope distributions (isotopomers) as a methodology for detecting shifts in plant carbon metabolism over long times. Trends in a deuterium isotopomer ratio allow quantification of a biogeochemically relevant shift in the metabolism of C 3 plants toward photosynthesis, driven by increasing atmospheric CO 2 since industrialization. Isotopomers strongly increase the information content of isotope archives, and may therefore reveal long-term acclimation or adaptations to environmental changes in general. The metabolic information encoded in isotopomers of plant archives bridges a fundamental gap between experimental plant science and paleoenvironmental studies.

PloS one, 2014

The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still ind... more The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still indispensable in the fight against malaria, although DDT and related compounds pose toxicological hazards. Technical DDT contains the dichloro congener DDD (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene) as by-product, but DDD is also formed by reductive degradation of DDT in the environment. To differentiate between DDD formation pathways, we applied deuterium NMR spectroscopy to measure intramolecular deuterium distributions (2H isotopomer abundances) of DDT and DDD. DDD formed in the technical DDT synthesis was strongly deuterium-enriched at one intramolecular position, which we traced back to 2H/1H fractionation of a chlorination step in the technical synthesis. In contrast, DDD formed by reductive degradation was strongly depleted at the same position, which was due to the incorporation of 2H-depleted hydride equivalents during reductive degradation. Thus, intramolecular iso...

Regulatory Toxicology and Pharmacology, 2015

There is a drive toward the mandated lowering and reporting of selected toxicants in tobacco smok... more There is a drive toward the mandated lowering and reporting of selected toxicants in tobacco smoke. Several studies have quantified the mainstream cigarette emissions of toxicants, providing benchmark levels. Few, however, have examined how measured toxicant levels within a single product vary over time due to natural variation in the tobacco, manufacturing and measurement. In a single centre analysis, key toxicants were measured in the tobacco blend and smoke of 3R4F reference cigarette and three commercial products, each sampled monthly for 10 months. For most analytes, monthly variation was low (coefficient of variation <15%); but higher (P20%) for some compounds present at low (ppb) levels. Reporting toxicant emissions as a ratio to nicotine increased the monthly variation of the 9 analytes proposed for mandated lowering, by 1-2 percentage points. Variation in toxicant levels was generally 1.5-1.7-fold higher in commercial cigarettes compared with 3R4F over the 10-month period, but increased up to 3.5-fold for analytes measured at ppb level. The potential error (2CV) associated with single-point-intime sampling averaged $20%. Together, these data demonstrate that measurement of emissions from commercial cigarettes is associated with considerable variation for low-level toxicants. This variation would increase if the analyses were conducted in more than one laboratory.