HR: 0800h
AN: B11D-0762    [Abstracts]
TI: Mercury Binding and Mobilization in Post-fire Soil Horizons
AU: * Burke, M P
EM: megaburke@ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Navarro, B
EM: bridgetn@ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Mendez, C
EM: caromend@gmail.com
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Lopez, S
EM: ibeatnessa@yahoo.com
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Ferreira, M
EM: marciaferreira@ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Rademacher, L
EM: lrademacher@pacific.edu
AF: University of the Pacific, Dept of Geosciences, University of the Pacific 3601 Pacific Avenue, Stockton, CA 95211, United States
AU: Jay, J
EM: jjay@seas.ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AU: Hogue, T S
EM: thogue@seas.ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering 5732 Boelter Hall, Los Angeles, CA 90095, United States
AB: Fires affect watersheds in many ways, including through increased erosion and sediment transport, decreased water quality, and transport and cycling of nutrients and metals. This research addresses mercury (Hg) mobilization within post-fire stream systems, focusing on the influence of soil particle size on binding affinity and potential transport. Using a network of sampling sites within the Piru Creek watershed, affected by the Day Fire during September 2006, total mercury (THg) was measured in soils collected before, during, and after the 2006- 07 storm season. Unburned and burned soil samples from various levels of burn intensity were collected in one- inch increments to a depth of 6 inches and partitioned into fine, medium and coarse fractions. THg concentrations within each grain fraction were measured in triplicate using a Milestone Direct Mercury Analyzer. Initial findings indicate a loss of THg at the surface in the burned soils, as well as increased levels of THg at depths of 2-4 inches. We hypothesize this to be due to volatilization of Hg due to burning, which is either released upward into the atmosphere, or becomes bound to organic matter and settles just below the surface during the formation of a hydrophobic layer. Surface loss may also be attributed to post-fire erosional processes and storm transport. Additionally, analysis of the size fractionated soils reveals that the highest readings of THg in unburned soils occurred in the fine sediments in every case. THg concentrations in fine sediments in the burned soils were not significantly higher than THg concentrations in medium or coarse sands. More recently collected samples show evidence of continuing atmospheric deposition of Hg at the soil surface. Leaching tests are also being performed on this same set of soils to aid in evaluating potential mobilization of THg from transported soils during storm events.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0461 Metals
DE: 1800 HYDROLOGY
DE: 1865 Soils (0486)
DE: 1871 Surface water quality
SC: Biogeosciences [B]
MN: 2007 Fall Meeting