Variations of sulfur isotope ratios in a single lichen thallus: A potential historical archive for sulfur pollution

Utilizing the analytical capability to measure S isotope ratios of small quantities of S in biological material without any chemical pretreatment, the variation of δ34S within a lichen thallus was investigated using old and young segments of fruticose lichen thalli (Alectoria sarmentosa) from an oil refinery area in Come-By-Chance and two coastal areas, Newfoundland, Canada. Old segments of lichen samples from the oil refinery area showed significantly higher δ34S values (1.0–2.5‰) than their corresponding young segments. Lichen samples from two coastal areas showed no noticeable differences in δ34S values between old and young segments. These results demonstrate that lichen thalli record temporal changes in the isotopic composition of atmospheric S and hence constitute a historical archive of atmospheric S pollution.