Document ZnvNwzLvBV0K0RB26yyO2qNMV

AR226-2682 4 AR226-2682 C-8 BIODEGRADATION IN ----GROUND WATER---- Andrew Hartten Dave Ellis May 7, 1998 GEOLOGICAL CROSS SECT SAMPLING LOCATIONS SITE CONCEPTUAL MODEL Source Areas Former anaerobic digestion pond (sludges removed) C-8 up to 614 mg/kg @ 8 - 10 foo Ground water at 309 SITE CONCEPTUAL MODEL Hydrogeology Sand and gravel 65-100 feet deep Yields up to 300 GPM Production wells influence GW flo Linear velocity 1 ft/day K= loo ft/ LUBECK WELL FIELD Travel time from anaerobic pond is about 5 years *& 2 ppb discharge concentration WHY STUDY C-8 DEGRADAT IN GROUND WATER? Long exposure to C-8 Lone residence times Available Relatively simple Converting Biodegradation R Constants to Half-lives C = C^e"^, where k is the rate consta If you solve the equation C = C^e'^, fo and t when C = 0.5C,, than t = -0.693/k t is half-life in days and k is the rate co For example: k-Wim9~= a half-life days or 1 year HI METHOD REQUIREMENTS GW velocity and direction Wells along a single flow line Analyses of parent and daughte Sorption information C-8 IN GROUNDWATER Distance c-8 pp MW-1 MW-2 MW-3 MW-4 MW-5 MW-6 Lubeck 0 220 520 800 1770 2440 2900 5.64 0.234 0.487 0.084 0.05 0.02 0.002 DETECTION LIMITS PQL =0.051 MDL = 0.0255 We use the MDL if concentration below niethod dete^tym lim^t M H 0 ifr '1 M g K g M s 0 0) 0 0) J "m APPARENT LOSS RATE Y O.OT2X SLOPE = 0.002=k R2 r - '-y^y-yyffy INTERPRETATION t ^ 0.69^k*v) However, k must be corrected for G velocity using the "retardation facto t = 0.693/(k*v*Rf) SORPTION/RETARDATION Rf = 1 + (pb/n) * (K^FJ ForC-8, K^=WOO F(,C= 0.0005 Pb=1.8 n=0.3 ______ivc=1 13o ------LI II II ---- > ' --------t ' IMPACT OF RETARDATION Velocity Slope*v 365 ft/yr 100 ft/yr A, 365 ft/vr 100 ft/yr 0.73 0.20 RetatfUfced ^ 0.0145 0.053 Half L 0.95 y 3.5 ye A . -S A^. I ^ m 13.1 y 47.7 y SENSITIVITES -Sp"- :{ Aquifer organic carbon content det retardation factor - big impact on T GW velocity - big impact on T 1/2 Intermediate source appears to exis Changes ability to fit data. 3M was not able to^nd either fluor or C-7 daughter products. CONCLUSIONS C-8 half life appears to be slow: ha from 13 to 48 years No biodegradation products found Rate estimate sensitive to TOC and Rate estimate very* sensitive to Koc