[ RadSafe ] Question on total river water activity

[Jaro Franta]

Dear Radsafers,

Taking the example of a large river like the St. Lawrence, what would be the
total river water activity discharge rate ?

Eisenbud's Environmental Radioactivity says that typical "surface water"
Radium activity (only!) ranges from 4 - 19 Bq/m^3
It doesn't differentiate between rivers or lakes as "surface water".

The St.Lawrence has a flow rate of 9,850 m^3/sec = 851E6 m^3/day or 0.3E12
m^3/y -- yielding about 3 GBq/y of Radium.

How much activity would the other uranium decay chain nuclides add to this
rough estimate ?

Also, would there be significant seasonal changes due to fertiliser runoff
from agricultural areas ? (phosphate fertiliser contains elevated
concentrations of uranium & daughters).

Finally, are there any published surveys that provide detailed statistics ?

Thanks in advance.

 Jaro
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