Transcript VO+SE+UE Stabile Isotope in der Ökologie * Stable Isotope Tracing

Ina Rennisch
Anna Zappe
Background information
 analyse hair samples from 65 cities across the U.S.
 „you are what you eat“
 model: hair isotopic compositions as a function of
drinking water and dietary input
 meassures δ2H and δ18O
 maps were constructed using the information gained
from the water samples to predict the isotopic
composition of the human hair (across 48 states)
4 potential sources
 dietary organic molecules
 dietary waters
 drinking waters
 atmospheric oxygen
 influence the synthesis within the hair follicle
Materials & Methods
 hair samples
 randomly collected
 tap water samples
 3 x 25mL per city
 mass spectrometer
 continuous flow mode
 carrier gas: He
Hypothesis
 nonexchangeable δ2H and δ18O
 insights: water and diet across
geographical regions
 correlation: hair and water samples
 model: diet and water
incorporate into keratin
Model Derivation
 keratin: synthesized from amino acids
 H atoms in keratin
 no isotopic exchange
 recorders of isotopic inputs
 model:
 sources and isotopic effects  determine H and O
isotopic composition of the amino acids incorporated
into hair keratin
Model Derivation 2
 location of H and O fixation in amino acids depends on
 amino acids
 pH
 O atoms in carbonyl  exchanged during digestion
 isotopic composition of gut water
 oxygen of keratin: relates to gut water
 H atoms in carboxyl, amide and sulfhydryl groups
exchange with the H in water
 H atoms in C-H bonds cannot be exchanged
Model Derivation 3
 H atoms in amino acids:

essential: C-H atoms in keratin should reflect the δ2H
values of food sources

nonessential: nonexchangeable H atoms may reflect:



δ2H values of dietary amino acids
amino acids synthesized in the body
 δ2H of nonexchangable H in keratin in human hair
should relate to water of the hair follicle
Influence
 H and O in follicle and gut water: multiple sources
 δ2H difference of cells and their surrounding water:
exchange of intra- and extracellular water
 2 water pools in human:
 describe influence of H ratio of tap water on water in the follicle
 H isotopic composition of hair follicle water is a mixture of
 extracellular (blood) water
 produced through the metabolism of dietary foods
 body water: other composition as drinking water  mixture of
 drinking water
 water derived from metabolism
Predictions and Implications
 observed slope: evidence that H and O atoms in hair
derived from secondary water pools
 scatter exceeded measurement prediciton
 could be related to continental supermarket diet
 robustness of model predicitons was tested
 analysed a second set of hair samples  barbershops
 predict isotope ratio of tap water
Mapping
 maps of δ2H and δ18O
values (496 locations)
 heaviest hair expected
in the southern parts:
Gulf coast, Texas,
Oklahoma
 lightest hair predicted in
region of the northern
Rockies
Results
 hair and tapwater samples from 18 states
 standard deviations within a city were generally small
 lightest values were from nothern Montana
 heaviest values were from southern Oklahoma
 Conclusion: water samples from same city are
isotopically similiar
Results 2
 linear relationship between these two parameters
 interpretation: 27% and 35% of the H and O in
hair were derived from local drinking water
Detecting Movements
 Beijing, China to Salt Lake City, Utah
 hair: sequential recorder of
changes in diet
 changes: detected in the
first interval after arriving
in Utah
 detectable: geographic movements
 locations with contrasting isotope ratios in tap water
Discussion: Deviation
 nonregional water sources
 bottled water
 juices
 barbershop
 visitors
Discussion: Scatters
 dietary differences
 H and O composition influenced by
 dietary inputs
 drinking water
 O also influenced by
 atmospheric O
Discussion
 near „constancy“ of dietary input
 continental supermarket diet
 not only locally derived foods
 stronger local water and hair isotope relationships:
 historical populations
 geographically isolated populations
Future research
 specifying regions of origin in
 anthropological
 archaeological
 forensic studies
 estimating the region-of-origin
 not sufficiently explored yet
Referenzen
Ehleringer J. R., Bowen G. J., Chesson L.A., West A. G.,
Podlesak D. W. & Cerling T. E. (2007): Hydrogen and
oxygen isotope ratios in human hair are related to
geography. In: Proceedings of the National Academy
of Sciences of the United States of America, Feb.
2008, pp. 2788 – 2793. The National Academy of
Sciences of the USA.
Thank you for your attention!