318-9 Use of Urban Residuals to Reduce Pb and As Bioaccessibility.

See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Symposium--S11/S02 Joint Symposium On the Beneficial Re-Use of Wastes and Environmental Implications of Waste Recycling: I
Tuesday, October 23, 2012: 10:45 AM
Duke Energy Convention Center, Room 250, Level 2
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Sally Brown, University of Washington, Seattle, WA and Ganga Hettiarachchi, Agronomy, Kansas State University, Manhattan, KS
The safety of urban farming has been questioned due to the potential for contamination in urban soils.  A laboratory incubation, field trial and 2nd laboratory incubation were conducted to test the ability of high Fe biosolids based composts to reduce the bioaccessibility of soil Pb and As in situ. Lead and As bioaccessibility were evaluated using an in vitro assay.   Changes in Pb, As, and Fe speciation were determined on select samples after the 2nd laboratory incubation using µ- XRF mapping followed by µ-XANES. A compost with Fe added during wastewater treatment (Fe WTR compost) added to soils at 100 g kg-1 decreased Pb bioaccessibility in both laboratory incubations.  Mixed results were observed for As. Composts tested in the field trial (Fe added as Fe powder or FeCl2) did not reduce bioaccessible Pb with limited reductions observed in bioaccessible As.  These composts also had no effect on Pb bioaccessibility during the 2nd laboratory incubation. Bulk XANES showed association of Pb with sulfates and carbonates in the control soil. µ- XANES  for 3 points in the Fe WTR amended soil showed Pb present as Fe sorbed Pb  (88 and 100%  of two points) and pyromorphite (12% and 53% of two points).  Bulk XANES of the Fe WTR compost showed 97% of total Fe present as Fe3+. The results of this study indicate that addition of high Fe biosolids compost is an effective means to reduce Pb accessibility only for certain types of Fe rich materials.
See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Symposium--S11/S02 Joint Symposium On the Beneficial Re-Use of Wastes and Environmental Implications of Waste Recycling: I