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I
<br /> •
<br /> Sparging with either Nitrogen or Ozone had a similar effect on several parameters The
<br /> concentrations of arsenic, molybdenum, potassium, sodium, chloride, and sulfate did not
<br /> change significantly The concentrations of calcium, magnesium, and alkalinity
<br /> decreased, while pH increased, which in turn resulted in lower conductivity and TDS
<br /> measurements These changes were expected due to stripping of carbon dioxide The
<br /> concentrations of barium, iron, and manganese decreased, probably due to precipitation
<br /> brought on by the increase in pH or, in the case of manganese, conversion to manganese
<br /> dioxide, a solid
<br />' Sparging with nitrogen did not significantly affect bromide, bromate, total chromium,
<br /> Cr(VI), rutrate, or ORP However, these parameters did change in the Ozone test Total
<br /> Cr and Cr(VI) increased from below their respective detection limits to 79 WL and 73
<br />' µg/L, respectively, which indicates that chromium in the soil can be oxidized The
<br /> concentration of nitrate increased from < 0 25 mg/L nitrate-N to 11 mg/L, due to
<br /> oxidation of reduced nitrogen species such as ammonia, nitrite or organic nitrogen)
<br />' Bromide decreased with concomitant formation of bromate, though the amount of
<br /> bromate formed (155 µg/L) was less than would be expected if all of the bromide lost
<br /> was converted to bromate (The concentration of bromide was 209 µg/L lower in the
<br /> Ozone test than in the Control Assuming one bromide molecule is converted to one
<br /> bromate molecule, this is equivalent to 348 µg/L bromate ) Finally, ORP increased,
<br /> •
<br /> confirming that oxidizing conditions had been achieved
<br /> 1
<br /> Aluminum, antimony, beryllium, cadmium, cobalt, copper, lead, mercury, nickel,
<br /> selenium, silver, thallium, tungsten, vanadium, and zinc were not detected in any aqueous
<br />' phase, though several were present in the soil
<br /> 3.3 Formation and Fate of Cr(VI)
<br /> The concentration of Cr(VI) in the COC Removal Tests is shown in Table 5 Cr(VI) was
<br />' not detected above the detection limit of 1 µg/L in Untreated GW, the Control, or the
<br /> Nitrogen test, but was seen at 73 µg/L in the Ozone test
<br />' Two tests were run to assess whether Cr(VI) could likely naturally attenuate The first
<br /> test measured the available Cr(VI) reducing capacity of soil which was found to be >
<br /> 65,000 µg Cr(VI)/kg of field moist soil This is greater than the estimated amount of
<br /> Cr(VI;--730 poNg soil—that can be generated by ozonation (Ozone treatment
<br /> increased the concentration of Cr(VI) by 73 µg/L in the COC removal test This is
<br /> equivalent to the oxidation of 730 µg Cr/kg of soil ) This information indicates that
<br />' untreated site soil has the capacity to reduce Cr(VI), though it should be noted that the
<br /> capacity of soil within the treatment zone—i e , soil exposed to ozone—might be lower
<br />' The second test to evaluate potential natural attenuation of Cr(VI) involved contacting
<br /> • ozone-sparged groundwater—which contained Cr(VI)---with untreated soil This
<br /> PRIMA Environmental 10 Evai of Ozone
<br /> ENSR-Unocal 5498
<br /> January 27, 2005
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