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1 <br /> Advanced GeoEnvironmental <br />' Larry's Auto <br /> March 4, 1996 <br />' Page 2 <br /> COMMENT <br />' Findings of low general and selective microbial populations may be indicative of biotoxicity due <br /> to excessive levels of contaminant (or other undefined biotoxin such as heavy metals) It should <br />' be noted that at concentrations above 7,500 ppm, materials containing solvents (such as gasoline) <br /> may exert a lethal effect on may microorganisms Also contributing to the low concentrations <br /> of recoverable microbes is insufficient levels of oxidized and reduced forms of nitrogen We <br /> recommend that ammoruum nitrate be added to these soils in order to raise combined rutrogen <br /> levels to 50-100 ppm Along with diluent water, such action will not only improve <br /> physicochemical conditions, but may also act to minimize biotoxicity <br /> It should also be noted that failure to recover selective biodegraders may reflect insufficient time <br /> of exposure of microorganisms to contaminant to allow for an appropriate subpopulation of <br /> selective degraders to adaptively develop <br /> We suggest that nutrients (along with water) be added initially to determine whether such action <br />' is sufficient tc, improve physicochemical conditions and microbial population dynamics <br /> Depending on results, bioaugmentation may be required to facilitate the development and <br /> maintenance of an appropriate biodegrading population (assuming biotoxicity can be averted) <br /> Should you have any questions concerning these results, please do not hesitate to contact me <br /> AKK ch <br /> 1 <br /> 1 <br /> 1 <br />