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232 Th 228 Ra

Estimate Submarine Groundwater Discharge (SGD)to the Atlantic Ocean. 232 Th 228 Ra. half life = 5.7 years l = 0.12 yr -1. Procedure:. 1. Measure inventory of 228 Ra in upper km of Atlantic Ocean. Flux 228 Ra = Inventory x l 2. Subtract riverine and sediment fluxes.

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232 Th 228 Ra

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  1. Estimate Submarine Groundwater Discharge (SGD)to the Atlantic Ocean 232Th 228Ra half life = 5.7 years l = 0.12 yr-1 Procedure: 1. Measure inventory of 228Ra in upper km of Atlantic Ocean. Flux 228Ra = Inventory x l 2. Subtract riverine and sediment fluxes. 3. Estimate 228Ra in SGD. TTO 1981-1989 228Ra flux (atoms) SGD Flux = [228Ra]SGD (at/L) Bob Key Princeton

  2. Distribution of 228Ra in SGD (226 samples) median mean Median = 6.5 x 106 at/L Mean = 17 x 106 at/L (3.9 dpm/L) (1.5 dpm/L)

  3. 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 TTO 1981-1989 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 River flux = 2.4 x 1016 L/yr 40-120% of the river water flux; probably >>river metal, nut, C flux

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