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<br />winter of 1965-66 showed maximum levels of 24 mg/i sodium chromate, <br />1.7 mg/i hexavalent chromium, and 3.9 mg/i total chromium in the <br />snowmelt sampled (Cargill, Inc., 1967). <br />In addition to toxicity some deicing compounds may pose a <br />more subtle threat to the receiving waters. Schraufnagel (1965) <br />in discussing substitute deicing compounds, describing the glycols <br />and alcohols in particular, as "having extremely high biochemical <br />oxygen demand (BOD), ranging from 70 to 133 percent of the <br />product weight". This is in contrast to urea which has a BOD.5: <br />weight ratio of only 9 percent and sewage with a 0.02 percent <br />ratio. Schraufnagel concluded that certain deicers, such as <br />ethylene glycol, if released into a nearby stream can exert <br />tremendous demand on existing dissolved oxygen. The report gave <br />an example which indicated that "one pound of deicing compound <br />with a BOD:weight ratio of 1.0, if discharged into a waterway <br />having 7 mg/i dissolved oxygen, will utilize all the oxygen <br />available in about 17,000 gallons of streamflow." <br />Another major concern in snowmelt discharges relates to the <br />lead concentration. Dramatic increases in the lead content of <br />the world's atmosphere have been demonstrated from analysis of <br />the G+eenland ice cap (Chow and Earl, 1970). Concentrations have <br />risen from 0.08 pg/kg in 1940 to 0.21 pg/kg in 1965. Large <br />quantities of lead are present in the atmosphere of urban centers <br />as shown by Colucci, et al. (1969). Values as high as 18.4 pg/m3 <br />have been found at sites near heavy traffic. Lead is a primary <br />contaminant of automobile emissions and tends to be deposited <br /> <br />20 <br /> <br />. <br />