Sulphur isotope composition of stream water, moss and humus from eight arctic catchments in the Kola Peninsula region (NW Russia, N Finland, NE Norway)

In summer 1994, stream water, moss and humus samples were collected for sulphur isotopic analysis from eight catchments located in the western Kola Peninsula region, where several industrial centres emit high loads of SO2 and other elements to the atmosphere. Three potential sources of sulphur and their isotopic signatures were identified: (1) marine (delta(34)S +20 to +21 parts per thousand CDT), (2) anthropogenic 34 emissions (<+10 parts per thousand), and (3) geogenic (variable delta(34)S, mostly <+10 parts per thousand). Averaged per catchment, the sulphur isotopic composition varies between +6.0 and +16.3 parts per thousand for stream water sulphate, +6.0 and +8.4 parts per thousand for moss sulphur, and +5.2 and +12.2 parts per thousand for humus sulphur. The delta(34)S composition of stream water from the more remote catchments is quite variable, reflecting several natural (geogenic) sources, but it becomes restricted to the range +8 to +10 parts per thousand near the pollution sources. A plot of delta(34)S vs. 1:SO4 in stream water suggests that sulphate originating from the smelters has a delta(34)S value approximate to+9.5 parts per thousand, and is a dominant source. Sulphur isotope values for moss and humus are consistent with the deduced composition for the emitted sulphur, though for humus a component of geogenic sulphur incorporated via vegetation uptake may play a role. Further isotopic characterisation of atmospheric emissions, together with environmental samples, is needed to better understand sulphur sources and sinks in the area.