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Niue Radioactivity

The mystery as to why Niue Island has natural radioactivity levels 100 times those of other Pacific islands may have been solved. Theories have suggested the high levels came from salt spray, hot spring deposits or from marine sediments laid down when the island was submerged.

Dr Neil Whitehead, a nuclear scientist with DSIR Physical Sciences, says his investigations show that Niue's unusual soils once absorbed minute quantities of radioactive uranium contained in seawater.

Heat rising from the dormant collapsed volcano on which the coral island sits had drawn cold seawater in through the sides of the 200-metre-thick coral layer. The geothermal process brought the seawater up through porous coral to the thin soil, where the uranium was deposited. Enough uranium and uranium daughter-products remain in the soil to produce high radiation levels.

High levels of antimony, silver and gold are also found near the surface. There are hopes that significant deposits of these may exist at depth. More disturbingly, very high levels of mercury have also been found in the soil.

DSIR