Nitrogen isotope ratios

Katzenberg, M.A., Saunders, S.R. and Fitzgerald, W.R. 1993 Age differences in stable carbon and nitrogen isotope ratios in a population of prehistoric maize horticulturists. American Journal of Physical Anthropology 90 267-281. 

The 8 C values of the Preclassic humans at Cuello (Table 2.1) average -12.9 0.9%o (n = 28) in collagen, -9.8 1.0 in bone apatite (n = 16), and -8.7 2.3%o in tooth enamel apatite (n = 33) the S N values in collagen average 8.9 1.0%o (n = 23). The discrepancy in the number of specimens is due to the fact that more teeth were available than post-cranial material, while some of the specimens contained insufficient collagen to measure the nitrogen isotope ratios. Additional bone apatite analyses are in progress. 

Keegan, W.F. and DeNiro, M.J. 1988 Stable carbon- and nitrogen- isotope ratios of bone collagen used to study coral-reef and terrestrial components of prehistoric Bahamian diet. American Antiquity 53 320-336. 

Nitrogen is mainly taken in by humans in the form of proteins, so there is no possibility for ambiguity here nitrogen isotopic ratios must reflect those of the protein in the diet. 

Schoeninger, M.J., DeNiro, M.J. and Tauber, H. 1983 Stable nitrogen isotope ratios of bone collagen reflect marine and terrestrial components of prehistoric human diet. Science 220 1381-1383. 

Variations in bone collagen nitrogen isotope ratios in C3 foodwebs are illustrated in Figure 4.2. 

Controlled Diet and Climate Experiments on Nitrogen Isotope Ratios of Rats... 

Nitrogen isotope ratios ( N/ " N) inerease from plants to herbivores to eami-vores and ean be used to estimate the degree of camivory in human diets. Some field studies observe a greater differenee in 5 N between trophie levels in dry, hot habitats than in wet, cool ones. Two hypotheses have been proposed to explain this variation in difference in 8 N between trophic levels. (1) Elevated excretion of -depleted urea in heat/water-stressed animals (2) recycling of nitrogen on protein-deficient diets. Both predict increased diet-tissue 8 N difference under stress. 

The results of heat and water stress experiments (Table 12.3) show that these factors had no significant effects on nitrogen isotope ratios of bone collagen or hair. The mean collagen-diet difference (A Nco-d) values of the water-restricted litters ranged from 2.6 %o for group 10 on diet A (36°, water ad... 

Ambrose, S.H. 1991 Effects of diet, climate and physiology on nitrogen isotope ratios in terrestrial foodwebs. Journal o/,4rc/2aeoZog caZ 18 293-317. 

Ambrose focuses on stable nitrogen isotope ratios and reports the results of controlled diet and climate experiments on rats. He explores trophic level differences and heat stress and their effects on stable isotopes of nitrogen. As with the preceding chapters by Schwarcz and Hedges and van Klinken, Ambrose explores the various biochemical principles that explain why variation is expected under these circumstances. 

Ambrose, S.H. DeNiro, M.J. (1989). Climate and habitat reconstruction using stable carbon and nitrogen isotope ratios of collagen in prehistoric herbivore teeth from Kenya. Quaternary Research 31,407-422. 

Bogaard, A., Heaton, T. H. E., Poulton P. and Merbach, I. (2007) The impact of manuring on nitrogen isotope ratios in cereals archaeological implications for reconstruction of diet and crop management practices. Journal of Archaeological Science 34, 335 343. 

Sealy, J. (1997) Stable carbon and nitrogen isotope ratios and coastal diets in the Later Stone Age of South Africa a comparison and critical analysis of two data sets. Ancient Biomolecules 1, 131 147. 

Ambrose, S. H. and DeNiro, M. J. (1986). Reconstruction of African human diet using bone collagen carbon and nitrogen isotope ratios. Nature 319 321-324. 

Altabet, M.A., and R. Francois. 1994. Sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization. Global Biogeochemical Cycles 8(1) 103-116. 

Now, GC-IRMS can be used to measure the nitrogen isotopic composition of individual compounds [657]. Measurement of nitrogen isotope ratios was described by Merritt and Hayes [639], who modified a GC-C-IRMS system by including a reduction reactor (Cu wire) between the combustion furnace and the IRMS, for reduction of nitrogen oxides and removal of oxygen. Preston and Slater [658] have described a less complex approach which provides useful data at lower precision. Similar approaches have been described by Brand et al. [657] and Metges et al. [659]. More recently Macko et al. [660] have described a procedure, which permits GC-IRMS determination of 15N/14N ratios in nanomole quantities of amino acid enantiomers with precision of 0.3-0.4%o. A key step was optimization of the acylation step with minimal nitrogen isotope fractionation [660]. 

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