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<br /> Du Pont HLR 394-87
<br /> The progression of benzene, toluene, and xylene concentrations in the lose
<br /> nutrient vessel is puzzling, in that no toluene or xylene were detected upon
<br /> Initial met-up and both were detected on day 2. After day 2 the levels
<br /> progressively decreased (except for 6/8/87 which follows the second addition
<br /> of the throe tubstraates on 6/5/87). The three substrates decreased to
<br /> undetectable levels in the medium nutrient vessel, in spite of the second
<br /> addition on 6/5/87.
<br /> i
<br /> Discussion/Conclusifln
<br /> Xylene area chosen for the CO evolution studies because it is one of the
<br /> more recalcitrant materials in gaabline which is regulated for groundwater by
<br /> the Environmental Protection Agency. The particular isomer employed in this
<br /> study was used because no other isomers of xylene were Immediately available
<br /> from commercial sources. The absence of significant differences between
<br /> treatments and controls at 24, 63, or 72 hr post nutrient addition may
<br /> r indicate that there was an immediate adaptation to xylene utilization and the
<br /> substrate was limited upon further incubation. In addition the unlabeled
<br /> xylene and ethanol used to dilute the labeled xylene may have enhanced the
<br /> initial degradation. Theoretically the DPS! obtained for 4 hr should aleu be
<br /> present at 24 and 72 hr. There was an apparent lose, preasum2bly by
<br /> i' desorption due to saturation of the filter, of the radiolobeled CO22 from the
<br /> filter, or the gradual replacement of the adsorbed labeled CD2 witg unlabeled
<br /> CO2 Therefore, the assumption was anode that the greater the response at 4
<br /> hr, the more optimal the conditions for growth, hence degradation. It was
<br /> difficult to determine rates of degradation using these data; therefore, the
<br /> decision to scale-up on certain treatments was :Wade based upon several other
<br /> pieces of information: when applying nutrient addition to the field, lower
<br /> concentrations are cheaper if they provide reasonable microbial growth, and
<br /> degradation; and, chemical analysis of the groundwater showed very little if
<br /> any natural phosphorus and nitrogen (C. D. Litchfield 7/4/87). The three
<br /> treatments which provided a response within the top 40% of treatments for
<br /> both soil slurries were 5, 6, and 9. Therefore, the low nutrient and medium
<br /> nutrient combinations were selected for scale-up. The top two responsive
<br /> treatments from soil slurry 8-1 both contained trace metalr, while the top
<br /> two responsive treatments for KW-19 did not contain trace metals. This
<br /> may.
<br /> suggest that depending upon the moil location, type, and contarminstSon the
<br /> trace metals may or may not be available.
<br /> A 6h solution of NaDH does not appear to be as good a trapping agent as
<br /> AER for the groundwater from Lodi. However, because the filter did not
<br /> become saturated with radiolsbeled CO2, an increase in mineralization was
<br /> reflected by an increase in CO2 on the filter over seven days. This is the
<br /> best situation from which to determine rates of degradation. z
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