232Th 228Ra

half life = 5.7 years = 0.12 yr-1

TTO1981-1989

Bob KeyPrinceton

1. Measure inventory of 228Ra in upper km of Atlantic Ocean.

Flux 228Ra = Inventory x

2. Subtract riverine and sediment fluxes.

3. Estimate 228Ra in SGD.

Procedure:

SGD Flux =228Ra flux (atoms)

[228Ra]SGD (at/L)

Estimate Submarine Groundwater Discharge (SGD)to the Atlantic Ocean

Distribution of 228Ra in SGD (226 samples)

Median = 6.5 x 106 at/L Mean = 17 x 106 at/L

(1.5 dpm/L) (3.9 dpm/L)

medianmean

Total 228Ra Inventory = 2.9 x 1024 atoms

Decay = 3.5 x 1023 at/yr

River flux = 0.3 x 1023 at/yr

Sed. flux = 1.3 x 1023 at/yr

SGD flux = 1.9 x 1023 at/yr

Mean 228Ra in SGD =17 x 106 at/L (3.9 dpm/L)

Median 228Ra in SGD =6.5 x 106 at/L (1.5 dpm/L)

SGD flux = 1-3 x 1016 L/yr

40-120% of the river water flux; probably >>river metal, nut, C flux

River flux = 2.4 x 1016 L/yr

TTO1981-1989