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AR226-2682 RECYCLED AR226-2682 i C-8 BIODEGRADATION IN ---------- GROUND WATER------ Andrew Hartten Dave Ellis May 7, 1998 g N O W 0o) >J EID473110 \ GEOLOGICAL CROSS SECTION S d rfih RJZ036078 SAMPLING LOCATIONS SITE CONCEPTUAL MODEL Source Areas Former anaerobic digestion ponds (sludges removed) C-8 up to 614 mg/kg @ 8 - 1 0 foot depth Ground water at 30' q ESI O w 0o) 00 EID473113 SITE CONCEPTUAL MODEL - 2 Hydrogeology Sand and gravel 65-100 feet deep Yields up to 300 GPM Production wells influence GW flow paths Linear velocity 1 ft/day K= loo ft/day ta H o it #* RJZ036081 LUBECK WELL FIELD I Travel time from anaerobic ponds is about 5 years / **" -* 2 ppb discharge concentration M Ha RJZ036082 M w \ WHY STUDY C-8 DEGRADATION IN GROUND WATER? Long exposure to C-8 Long residence times Available **%. \I \ M H Relatively simple O r^t>* RJZ036083 Converting Biodegradation Rate Constants to Half-lives________ C = C0e`kt, where k is the rate constant If you solve the equation C = C0e'kt, for k and t when C = 0.5Cothan t = -0.693/k where t is half-life in days and k is the rate constant . For example: k - l l m r ^ a half-life of 365 days or 1 year METHOD REQUIREMENTS GW velocity and direction Wells along a single flow line Analyses of parent and daughters Sorption information C-8 IN GROUNDWATER 1Distance c-8 ppm MW-1 MW-2 MW-3 MW-4 1 MW-5 MW-6 Lubeckj 0 220 520 800 1770 2440 2900 Xf .<,4 5.64 0.234 0.487 0.0842 0.05 0.02 0.002 1.1 . If if RJZ036086 S* V AV il DETECTION LIMITS PQL =0.051 MDL = 0.0255 We use the MDL if concentration is below giethod detection limit APPARENT LOSS RATE istance RJZ036088 EID473121 illiiW RJZ036089 EID473122 't>' INTERPRETATION t = 0.693/(k*v) However, k must be corrected for GW velocity using the "retardation factor". t = 0.693/(k*v*R^ H ... O i U*4 -s K i s 4 RJZ036090 SORPTION/RETARDATION Rf = 1 + (Pb/n) * 0*FJ For C-8, Km-WOO Foc= 0.0005 pb= 1.8 n = 0.35 li .1 R ,= 13.8 RJZ036091 * .% fC I IMPACT OF RETARDATION i mmtmmm RJZ036092 : i !' S8 outo> Velocity Slope*v Half Life 365 ft/yr 100 ft/yr * 365 ft/vr 100 ft/yr 0.73 0.20 R etried \ 0.0145 0.053 0.95 years 3.5 years *A, 13.1 years 47.7 years ,, * II. 3 ( SENSITIVITES Aquifer organic carbon content determines retardation factorbig impact on Tl/2 GW velocity - big impact on T 1/2 Intermediate source appears to exist. Changes ability to fit data. 3M was not able to^nd either fluoride or C-7 daughter products. M H O iir . $ i RJZ036093 CONCLUSIONS I C-8 half life appears to be slow: half life from 13 to 48 years No biodegradation products found by 3M Rate estimate sensitive to TOC and V m Ha Rate estimate very*sensitive to KqC l 1 RJZ036094