Isotope applications

Our stable isotopes research tackles a range of different applications and involves collaboration not only with colleagues but also a wide range of partners across the globe.

We have a wide range of analytical equipment to facilitate this work.

Changes in isotopic composition over time can be accurately determined at near natural abundance levels by isotope ratio mass spectrometry. Stable isotope signatures can thus be used as natural, intrinsic tracers to study systems where the use of proxies would be impracticable, for example for following the movement of water using dyes. Isotope analysis can therefore provide a powerful tool for tackling many environmentally important questions:

  • The identification of primary and secondary food sources, elucidating predator/prey relationships and constructing food webs.
  • Tracing nutrient and mineral uptake by plants and animals.
  • Determining the relative importance of plants and microbes to greenhouse gas emissions from soil.
  • Measuring environmental stressors by monitoring plant uptake of CO2 and/or water.
  • Tracing the sources of catchments waters.

Information about the functioning of the microbial pool in soils, estuarine and marine sediments is obtained from carbon isotopes in phospholipid fatty acids. Whilst the same isotopes in neutral fatty acids and alkanes may provide a tool for determining the main sources of erosion contributing to riverine sediments

Measuring the stable isotopes in particular compounds (such as phospholipid fatty acids, PLFAs) can provide additional information from that obtained by bulk isotope analysis

Guaranteeing the authenticity of produce and food ingredients is vital to the food and drink industry if it is to combat fraudulent misrepresentation or adulteration of premium products and to maintain consumer confidence. Multi-element isotope signatures are a powerful tool for establishing the geographical and biological origins of food and drink.

Scottish premium foods and Scottish water isoscapes

During 2011/2012, freshwater samples were collected with the support of the Scottish Environment Protection Agency (SEPA) from more than 120 freshwater lochs and reservoirs across Scotland.

Figure A (below) shows preliminary isoscapes generated from measured ?²H values (scale normalised to VSMOW) of standing Scottish freshwaters (118 sampling locations).

Isoscapes are topographical maps showing lines of isotopic composition (of a particular compound or material) are a relatively young tool underpinning research as well as research applications concerned with spatial distribution of biochemical or environmental markers.

In the context of protecting and authenticating premium foods isoscapes of standing Scottish freshwaters provide the reference data to which stable isotope signatures of premium produce or premium food products such as Scottish berries (Figure B) and Scottish whisky (Figure C) should be well correlated. In other words, water isoscapes provide the foundation for using stable isotope signatures as proxy for geographic provenance.

Our fundamental and applied water research is linked to stable isotope based research. It is also engaged in or with the following:

  • Research in and monitoring of climate change; here detailed Scottish water isoscapes will provide a baseline against which future environmental impact can be assessed by monitoring longitudinal changes in the characteristic isotope composition of freshwater lochs and reservoirs.
  • National Waters Inventory for Scotland; at The James Hutton Institute a national baseline study of the state of Scotland’s water resource is currently being carried out to understand resilience to the accumulating catchment pressures of delivering national objectives for food and renewable energy production, water supply for people, ecology and industry. Scottish water isoscapes are one of the many powerful analytical tools used to build a picture of the state of our water resource.
Figure A: Scottish water isoscapes
Figure B: 2H isotopic abundance as exclusion criterion for provenance of soft fruit.
Figure C: Bulk 2H / 18O isotope analysis of bottled whisky can detect counterfeit products.

Radiogenic isotopes are an extremely useful means to determine geological stratigraphy and digenesis from geological materials. For example, working with partners in the oil and gas industry (Isotopic Ltd) we can analyse the strontium (Sr) isotope ratio of the salts from production waters and/or cores of any vintage to characterise reservoir stratigraphy, compartmentalisation and connectivity.

Strontium isotopes can also used for “strontium Isotope stratigraphy” where materials, geological or biological which have precipitated in a marine situation and have retained their original isotope signature can be dated. These Sr isotope ratios are plotted against a very well calibrated data set for global marine Sr isotopes over geological time.

Digenetic alteration of carbonates can also be studied in detail using Sr isotopes. In addition we can analyse samarium and neodymium (Sm-Nd) isotopes for provenancing sedimentary stratigraphy where other methods cannot be applied, for example, bio-stratigraphy.

Carol-Ann Craig, Gillian Martin, Maureen Procee