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Brian T. Frus <br /> Pacific Environmental Group, Inc. <br /> Project: 310-01.04 <br /> Date: February 1, 1993 <br />{ <br /> CONCENTRATION <br /> DECAY <br /> This document shows the results of decay in <br /> influent concentrations to a soil vapor <br /> extraction system. And calculates the theoretical <br /> mass of TPH removed from soils at a site. <br /> Initial conditions: <br /> ug <br /> Initial concentration CO 40000• — <br /> Half-concen- thalfA 50 day <br /> tration: <br /> cf <br /> Flow Rate: flow 2- <br /> M <br /> Asymtote: (Percent of initial Cf 10 <br /> concentration,CO) : <br /> Compute decay constant, <br /> kA: <br /> ln(2) -1 <br /> kA� = kA = 0.014•time <br /> thal fA <br /> Decay function: <br /> 4 <br /> [Cf -_(kA• t) . Cf <br /> C:(t) := CO• 1 - e + <br /> 10011 100 <br /> Graph the decay in concentration, C <br /> over time: <br /> is t '1:T= 0 day,2 day 360 day t2 := 0• day,30• day . .360- day <br /> CO t2 1 <br /> C(t2) • — <br /> day u <br /> 0 40000 <br /> 30 27751.1 <br /> 60 19669.9 <br /> C(t) *. 90 14338.3 - <br /> 120 10820.7 <br /> 150 8500 <br /> 180 6968.9 <br /> 210 5958.7 <br /> 240 5292.3 <br /> ug 270 4852.6 <br /> 0- - p 300 4562.5 <br /> 1 C 330 4371.1 <br /> 0- day t 360 day 360 4244.8 <br /> Y <br /> F <br />