Lead-210 in Natural Waters.

The distribution of lead-210 which enters the oceans subsequent to its production in the atmosphere by radon-222 decay, shows an increase with depth in sea water. By use of a simplified two-layer model of the ocean, a residence time of lead in the upper mixed layer of less than 2 years is derived. It is suggested that the marine biosphere is responsible for the conveyance of lead from surface to deeper waters. The distribution of lead-210 in the Colorado River indicated a rapid removal along the path from its origin in the feed waters to the reservoir at Lake Mead.