WA4 Metals in the Environment: Chemistry and Fate Issues
Room 16A/B, Level 4
8:00 AM - 12:00 PM, Wednesday, 12 November 2003
Chair: Bell, Russell ,
Co-chair: Campbell, Peter ,
(355) Lead and Zinc Migration in the Big River System, Southeastern Missouri.
Wronkiewicz, D1, McBurnett, J1, Faeth, A1, Wolf, S1, Mendosa, C1, Krizanich, G1, Struttman, S1, Hemmann, R1, Adams, C1, 1 University of Missouri-Rolla, Rolla, MO, USA
ABSTRACT- Over 300 years of mining in the "Old Lead Belt" of Missouri has resulted in the accumulation of over 250 million tons of waste tailings. Water and sediment samples were collected from the Big River and associated tributaries during four sampling periods (March, June, September, and December 2002) to evaluate potential contaminant transport processes. Solution pH values gradually increased from a low of 7.3 from tailings pile streams to a high of 8.3 on the Big River. Many metals are released from the tailings piles in a soluble or colloidal form. Zinc contents are highest in tributary streams emanating from tailings piles (ranging up to 20,825 ppb) with up to 82 and 88% passing through a 0.02 and 0.45 
m filter, respectively. Lead is also released in a soluble or colloidal form, with maximum concentrations of 623 ppb, and 13 and 23% passing through the two filter sizes. Zinc contents were reduced to 150-225 ppb upon entering the Big River, with the <0.02 m fraction representing only 2 to 8% of the total. Zinc values were reduced to detection (0.6 ppb) further downstream. Lead concentrations in the Big River ranged from 195-285 ppb with between 92-99% associated with >5.0 mm sized particles. Contributions from this size fraction increasing during flood stage. Manganese contents correlate well with Zn and Pb, suggesting that these metals may be coupled in transport. In the bed load sediments, Zn contents were highest in the silt- to clay-sized fraction, ranging up to 1600 and 26,400 ppm for Big River and tailings pile sediments, respectively. Lead contents were also highest in the fine sediment fraction, with up to 2800 and 24,800 ppm for Big River and tailings pile sediments, respectively. Detrital grains of Pb and Fe sulfide increase in roundness and decrease in size down river. These grains do not appear to survive transport distances of more than 10 miles.
Key words: zinc, lead, sediments, mine waste