Variations in sulphur content and stable sulphur isotope composition of vegetation near a SO2 source at Fox Creek, Alberta, Canada.

The proportion of sulphur found in vegetation increases as an industrial sulphur dioxide emission source is approached, but this trend is modified by topographic extremes. Stable sulphur isotope analysis revealed that increased sulphur concentrations in arborcal and terricolous lichens, andPicea glauca needles were due to incorporation of sulphur emitted as sulphur dioxide by the Kaybob sour gas plant near Fox Creek, Alberta, Canada. It is confirmed thatPicea glauca gets its sulphur from both the soil and the air; arboreal lichens get their sulphur primarily from the atmosphere; and terricolous lichens get theirs from the air and particulate fallout. It is suggested that arboreal lichens selectively excrete isotopically light sulphur when thallus concentrations exceed 1,400 ppm. Accumulation of sulphur in vegetation is dependent, on fumigation episode duration, frequency, and concentration, as well as the plant's ability to avoid injury, but is not closely correlated with average sulphation rates. The implications of terrestrial moss-lichen carpet destruction is discussed.