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' Vedose Zone Model <br /> � S <br /> Z <br /> Depletion of the source is assumed to occur due to volatilization and leaching losses <br /> Note that the source is not assumed to undergo microbial decay, or biodegradation, on <br /> the assumption that high soil concentrations are toxic to the microorganisms In terms <br /> of a molar balance this can be written as <br /> dm = --J" — J, (A-8) <br /> dt MW MW <br /> ' where <br /> m = number of moles of chemical per unit area in the <br /> hydrocarbon source [moles/cm2] <br /> ' MW = molecular weight of chemical [g/mol] <br /> J.,, = rate of mass depletion per area due to percolating water <br /> J„ = rate of mass depletion per area due to volatilization <br /> [g/cm2/dl <br /> t = time [d] <br /> tA.41 Aqueous Losses <br /> The leaching loss is assumed to be purely advecttve (due to water percolating through <br /> the source) <br /> ' _ L g <br /> (A-9) <br /> JW — qc"°�1000cm3 1000mg <br /> where <br /> JW = rate of mass depletion per area due to percolating water <br /> ' [g/cmz/d] <br /> q = net recharge or infiltration rate [cm/d] <br /> ' CW, = dissolved phase concentration in the source [mg/1-1 <br /> A-7 <br /> 1 <br />