es8b00530_si_001.pdf (1.47 MB)
Metal Reactivity in Laboratory Burned Wood from a Watershed Affected by Wildfires
journal contribution
posted on 2018-07-18, 19:17 authored by Asifur Rahman, Eliane El Hayek, Johanna M. Blake, Rebecca J. Bixby, Abdul-Mehdi Ali, Michael Spilde, Amanda A. Otieno, Keely Miltenberger, Cyrena Ridgeway, Kateryna Artyushkova, Viorel Atudorei, José M. CerratoWe investigated interfacial
processes affecting metal mobility by wood ash under laboratory-controlled
conditions using aqueous chemistry, microscopy, and spectroscopy.
The Valles Caldera National Preserve in New Mexico experiences catastrophic
wildfires of devastating effects. Wood samples of Ponderosa Pine,
Colorado Blue Spruce, and Quaking Aspen collected from this site were
exposed to temperatures of 60, 350, and 550 °C. The 350 °C
Pine ash had the highest content of Cu (4997 ± 262 mg kg–1), Cr (543 ± 124 mg kg–1),
and labile dissolved organic carbon (DOC, 11.3 ± 0.28 mg L–1). Sorption experiments were conducted by reacting
350 °C Pine, Spruce, and Aspen ashes separately with 10 μM
Cu(II) and Cr(VI) solutions. Up to a 94% decrease in Cu(II) concentration
was observed in solution while Cr(VI) concentration showed a limited
decrease (up to 13%) after 180 min of reaction. X-ray photoelectron
spectroscopy (XPS) analyses detected increased association of Cu(II)
on the near surface region of the reacted 350 °C Pine ash from
the sorption experiments compared to the unreacted ash. The results
suggest that dissolution and sorption processes should be considered
to better understand the potential effects of metals transported by
wood ash on water quality that have important implications for postfire
recovery and response strategies.