To first order, δCu values in organisms are driven by the δCu values of source materials. The δCu values of various soils from different regions have been found to vary from -0.34 to +0.33‰ depending on the biogeochemical processes taking place in the soil and the ligands with which Cu complexes. Organic-rich soils generally have lighter δCu values than mineral soils because the organic layers result from plant litter, which is isotopically light.
In plants, δCu values vary between the different components (seeds, roots, stem and leaves). The δCu values the roots of rice, lettuce, tomato and durum wheat plants were found to be 0.5 to 1.0‰ Cu-depleted relative to their source, while their shoots were up to 0.5‰ lighter than the roots. Seeds appear to be the most isotopically light component of plants, followed by leaves, then stems.
Rivers sampled throughout the world have a range of dissolved δCu values from +0.02 to +1.45‰. The average δCu values of the Amazon, Brahmaputra and Nile rivers are 0.69, 0.64 and 0.58‰, respectively. The average δCu value of the Chang Jiang river is 1.32‰, while that of the Missouri river is 0.13‰.