Chernobyl radiocaesium in upland watershed-lake systems, Galloway, south west Scotland

Abstract

Levels of Chernobyl radiocaesium found in the upland region of Galloway, south west Scotland were relatively high e.g. catchment mean134Cs inventories ranged from 5.72±2.64 kBq m2 to 8.72±1.46 kBq m2. The nuclear weapons test137Cs content of soils and peats was significantly augmented. Accurate assessment of spatial variations and temporal changes in the levels of contamination, however, are inhibited by its marked, short-range heterogeneity. No significant change in mean catchment inventories was detected over a twelve month period. Lake sediment inventories, however, were consistently enhanced from initially lower levels of contamination than their catchments' surfaces. Pre Chernobyl catchment and lake sediment137Cs inventories, however, show no such contrast. Both are substantially lower than rainfall based predictions. These observations of the relative levels of Chernobyl and pre-existing radiocaesium in watersheds and their waterbodies have important implications for both the assessment of the catchment and lake residence times of particle-associated contaminants and the use of lake sediment records as monitors of such pollutants.