δ³⁴S-Value Measurements in Food Origin Assignments and Sulfur Isotope Fractionations in Plants and Animals

Abstract

The delta(34)S values of biological material, especially food commodities, serve as indicators for origin assignments. However, in the metabolism of higher plants sulfur isotope fractionations must be expected. As a matter of fact, the delta(34)S values of the sulfate- and organic-S, respectively, of Brassicaceae and Allium species vegetables showed differences between 3 and 6 per thousand, and differences in glucosinolates were between 0 and 14 per thousand. delta(34)S-value differences of total-S between individual tissues of the same plant were approximately 3 per thousand. It is believed that these relatively small and variable fractionations are due to the partition of individual S-metabolism steps to different plant compartments, where they may occur independently and quantitatively. The delta(34)S values of herbivore muscle meat and milk relative to the diet and between an animal and its child had trophic shifts of approximately 1.5 per thousand. (34)S enrichments of up to 4 per thousand were observed for hair, hooves, and horn, an isotope fractionation of -5 per thousand between the diet sulfate and cartilage. Therefore, the reported agreements between delta(34)S value of biomass and primary S sources are true for only bulk material and not for individual compounds or tissues.

Sulphur-isotope compositions of pig tissues from a controlled feeding study

“…This has been observed in other studies (e.g., Arneson and MacAvoy, 2005;Barnes and Jennings, 2007;Tanz and Schmidt, 2010) Richards et al (2003) analysed horse hair under controlled feeding conditions and determined that hair keratin was 34 S-depleted relative to diet by ∼−1 ‰. In contrast, we determined a small 34 S-enrichment relative to diet of +1.2 ± 0.3 ‰.…”

“…There are, however, few controlled feeding studies involving animals that can be reliably used to make inferences about tissue -diet and tissue -tissue isotopic discrimination for humans. Studies using, for example, invertebrates (e.g., McCutchan et al, 2003), fish (e.g., Barnes and Jennings, 2007) and ruminants (e.g., Tanz and Schmidt, 2010) as animal models, although valuable in their field, are of limited use for human palaeodietary reconstruction. More relevant feeding experiments using pigs (Gonzalez-Martin et al, 2001), horses (Richards et al, 2003) and mice (Arneson and MacAvoy, 2005) have been hampered by small sample sizes or few replicates per dietary group, and have not included the investigation of archaeologically-relevant tissues (i.e., bone collagen).…”

Multi-element stable isotope analysis of H, C, N and S in hair and nails of contemporary human remains

“…Under protein deficiency, hair got enriched in 34 S by 4‰ compared to diet. Results of Tanz and Schmidt [60] indicate an enrichment of 34 S up to 4‰ in hair, hooves and horn of herbivores relative to diet. They conclude that δ 34 S values of animal samples basically reflect the diet but show small 34 S enrichments relative to it, depending on the animals' nutrition status, the trophic level and the individual tissue [60].…”

“…Results of Tanz and Schmidt [60] indicate an enrichment of 34 S up to 4‰ in hair, hooves and horn of herbivores relative to diet. They conclude that δ 34 S values of animal samples basically reflect the diet but show small 34 S enrichments relative to it, depending on the animals' nutrition status, the trophic level and the individual tissue [60]. Additionally, as in metabolism methionine generally is depleted in 34 S compared to cysteine [60], alteration in the concentration of methionine respectively cysteine can result in changes δ 34 S values along the nail plate.…”

A calf for all seasons? The potential of stable isotope analysis to investigate prehistoric husbandry practices

“…There are currently few publications with significant  34 S data-sets from archaeological skeletal material, due to technical difficulties of the analysis which are now largely being overcome (Nehlich and Richards, 2009;Privat et al, 2007;Tanz and Schmidt, in press). Our understanding of the ways in which these can be interpreted are therefore at an early stage, although it is clear that the data can reflect mobility related to the geology of the region of plant growth at the base of the food chain and to the proximity of the coastline, where the 'sea spray' effect of marine sulphates can be reflected in the dietary resources (Richards et al, 2001;Richards et al, 2003).…”