The partitioning of atmospheric iodine-129 in a shallow sand aquifer at Sturgeon Falls, Ontario.

Abstract

The transport and partitioning of 129I has been examined for a shallow groundwater flow system at Sturgeon Falls in northeastern Ontario. Recharge into a sandy surficial postglacial deltaic aquifer occurs in the vicinity of a seasonally-wet boreal forest. Concentrations of stable iodine, 129I, tritium, radiocarbon, stable isotopes and major ions were measured on samples of groundwater and precipitation. The present-day tritium profile delineates the position of the early 1960's thermonuclear bomb-pulse at a depth of approximately 12 m. The concentrations of stable iodine for groundwaters above, near and below the present-day bomb pulse range from 0.07 to 1.7 ppb. The groundwater in the lower aquifer is practically tritium-free (<2 TU) and is considered to be pre-bomb in age. The lesser concentrations of 129I in Sturgeon Falls groundwaters, compared with those from other studies in central Canada, suggest that the levels of 129I in these groundwaters may have been attenuated by complexation or ion exchange with organic materials in the near-surface soil horizons. Additionally, the concentrations of 129I in the mine waters of the Con Mine, in Yellowknife, NWT were examined. (Abstract shortened by UMI.)