SITE INFORMATION AND CORRESPONDENCE_1985-1997

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CLA CL-2 CLCL4 1 OCL-2 OCL-3 OCL-4 /8 16 14 mnaas 0190 12 bdv 14 oonens 010. E2 12 - E 2 E m 10 9 e E 8 O 6 O 6 CI 4 O 4 2 2 0 ■ - 0 I 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 DISTANCE FROM SOURCE(m) DISTANCE FROM SOURCE(m) 3500 CL-1 CL-2 CL-3 CL4 Day 18 OCLA OCL-2 OCL-3 OCL4 �- Day 18 3500 3000 A -�- Day 22 3000 ata -� Day 22 2500 O �- Day 26 U 2500 bnq" -�-- Day 26 2000 a Q W 1500 �- Day 32 Z 2000 �- Dry 32 N 1000 -A Day 34 N 1500 . A Day 34 W 1000 m 5p0 ---•lt- Day 36 m � - Day 36 0- - -- Day 38 0 -}- Day 38 0.0 0.5 1.0 1.5 2.0 X Day 39 0.0 0.5 1.0 1.5 2.0 Day 39 DISTANCE FROM SOURCE(m) DISTANCE FROM SOURCE(m) CL-1 CL-2 CL-3 CL4 OCLA OCL-2 OCL-3 OCL4 3500 3500 was 3000 enauab J 3000 02500 - p a 2500 ORC. W 2000coneraN W 2000 t2 W 1600 W 1500 O JO 1000 JO 1000 Soo r 500 0 0 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 DISTANCE FROM SOURCE(m) DISTANCE FROM SOURCE(m) Figure 6. Concentration of(a) D.O., (b) benzene,and (c)tolu- Figure 7. Concentration of(a) D.O., (b) benzene,and(c)tolu- ene along the Concrete Line. ene along the ORC-Concrete Line. degradation Of toluene under denitrifying conditions it is likely that oxygen in excess of its water solubility primarily upgradient of CL-1. was released by the ORC, which is consistent with the These results indicate that,in the absence of oxygen estimate presented above. The approximately 35 mg/L amendment,there was a small decrease in benzene con- of D.O. that bubbled out of solution during the first centrations and a maximum of 50 percent decrease in 25 days would volatilize approximately less than 1 per- toluene concentrations in the Concrete Line,when com- cent of the dissolved benzene or toluene. pared to concentrations at the first monitoring point Based on transformation stoichiometry, it was (CL-1). Any significant additional reduction in BiT in expected that approximately 3.1 g of 02 would be the ORC-Concrete Line, discussed below, would likely required for complete mineralization of 1 g of benzene be due to aerobic degradation. or toluene. However,some of the carbon would be used for biomass growth, rather than mineralization, thus ORC-Concrete Line reducing the oxygen required for degradation. Allen Assuming an average linear ground water velocity (1991) measured a biomass carbon incorporation of 15 of 32 cm/day (from the bromide temporal data)and the to 40 percent for toluene in Borden sand, which corre- oxygen release rates cited above for the ORC concrete, sponds to an oxygen demand of 2.1 to 2.8 g 02 per gram the expected D.O. concentration in ground water pass- of toluene. Thus, it would be expected that the target ing through the well screen containing ORC-concrete benzene and toluene injection concentrations ofapprox- briquets was approximately 93 mg/L for the first 25 days imately 4 mg/L per compound would require approxi- and 56 mg/L for the remainder of the experiment.Using mately 16.8 to 22.4 mg/L of 02,with a maximum 25 mg/L the Henry's law constant for oxygen provided by Metcalf Of 02 for complete mineralization. Since oxygen water & Eddy (1979), the solubility of oxygen in water (7 C) solubility is approximately 58 mg/L at 7 C.and assuming exposed to a pure oxygen atmosphere can be calculated biotransformation is essentially instantaneous,the com- to be approximately 58 mg/L. Since very small bubbles plete mineralization of BiT should leave approximately were observed in the screens containing ORC concrete, 33 to 41 mg/L D.O. within the well screen containing WINTER 1994 GWMR ■ 125