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KINUIC ANALYSIS OF LIVQC-/BI'FX REMOVAL • dt =change in time The following equation offers the simple solution C =Coe bt where e =base of natural log -bt=exponent to the base e CO=initial concentration of volatile organic compound in groundwater(µg/3} The equation shows the behavior of the phenomen a�o"exponentiala��Qncentratson ", since the exponential term a-bt appears in it The curve starts from and decreases in proportion to the remaining,thus_ - - --- r - -- - -- - --- ---- log CICO=bt/2.303 or log C=log CO bt/2.303 If C = COa,b=0 6931t1/2 The constant tl/2 corresponds to the length of time i n needed forthe the groundwater of CO to decrease by 50%,t e ,tl� is the half-life of the substance In Figure 6,the mean-log CICO is plotted versus time to derive the approxunate decay • rate observed for the site conditions Note that because the yaxisisth onesgants foo �'OCs indicates proportional r�u tjoI3, (Figure 6a)and BTEX compounds(Figure 6b)were computed some a first approximation. ase rmean value was clearly being fitted to a dampened oscillating decay HVOC removal rates fell between 09t and 14t. TE alue every ratesval o 1 t dafell ysen In alt and.20t This corresponds to a steady rate of reductio to 1 conservative estimate, it would take slightly less than 100 days to reduce the core region(15 2 m wide by 9 1 m deep by 61 m long [50 ft by 30 ft by 200 ft]) to below 5 µg/1, assuming no other sources invade the eddies,with the treatment volume Figure 7 plots the linear decay rates on a logarithmic set of axes to depict the time to bring core region concentrations to 19911. With HVOCs,the time ranged from 50 to 100 days For BTEX compounds,the level ranged between 20 to 60 days. Please note that the H VOOCC is removal rate is somewhat slower since the beginning concentration of 2000 µg/1 total higher than the starting point of the BTEX compounds(50 to 70 µPQ) 8