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14C Calculations Based on

PHREEQC Inverse ModelResults

1) GetImC, the total carbon in the initial water

!ou also the "now AI, the14C activit#

$easured in the initial water

%) Get the $ass trans&er a$ounts o& the di&&erent

carbon 'hases (oin( into or out o& solution,

e(3

CaCOm &or calcite, 2COm &or C%, 3 2( )CaMg COm

&or dolo$ite, etc*

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+) eter$ine or esti$ate the 14C activit# o& the

various carbon 'hases (oin( into or out o& the

solution- 3CaCOA &or calcite, 2COA &or C%,

3 2( )CaMg COA &or dolo$ite, etc*

4) Calculate .nd/14C activit# assu$in( no

radioactive decay) &or the &inal solution based

on the PHREEQC inverse $odel results 0or

ea$'le-

( 2 2 3 3 3 2 ( ) (

I

C I CO CO CaCO CaCO CaMg CO CaMg CO

nd F

C

m A m A m A m AA

m

=

whereF

Cm is the total carbon in the &inal

solution

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2) 3o $a"e sure that #ou have the ri(ht value o&

F

C

m , co$'areF

C

m &ro$ the PHREEQC

out'ut &ile to #our own carbon balance

calculation derived &ro$ the PHREEQC

results-

2 3 3 2( )2F IC C CO CaCO CaMg COm m m m m=

) .s a &urther chec", do also the 1+C $ass

balance calculation-( )

2 2 3 3 3 2 3 2

13 13 13 13

( ) ( ) 2 I

C I CO CO CaCO CaCO CaMg CO CaMg COF

C F

C

m C m C m C m C m

m

=

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5) Calculate the corrected 14C a(e, t /in #ears)

&or a (iven PHREEQC inverse $odel, &ro$

#our calculated value o& .nd/14C activit#

assu$in( noradioactive decay) and &ro$ the

14C activit#, .$,0, actuall# $easured &or the

&inal water-

,

5730ln

ln2nd

m F

At

A

=