Mass loading of nickel and uranium on plant surfaces: application of laser ablation-ICP-MS
Tracy Punshon,*a,b Brian P. Jackson,b Paul M. Bertschb and Joanna Burgera
aConsortium
for Risk Evaluation with Stakeholder Participation, Environmental and
Occupational Health Sciences Institute, Division of Life Sciences, Rutgers
University, 604 Allison Road, Piscataway, NJ 08854, USA. E-mail: punshon@l:rel.edu
bThe University of Georgia, Savannah River Ecology Laboratory,
Drawer E, Aiken, SC 29802, USA
Received 8th September 2003, Accepted 2nd December 2003
First published as an Advance Article on the web 20th January 2004
Transport
of contaminated sediments from a former radiological settling pond results
in the deposition of U and Ni in the Lower Tims Branch (LTB) (Aiken, SC,
USA). Uranium is unavailable for plant uptake, but elevated U and Ni concentrations
associated with foliage of understory plants suggested mass loading. Mass
loading of contaminated soil on Andropogon elliottii Chapman
(poaceae) was investigated using laser ablation inductively coupled plasma
mass spectrometry (LA-ICP-MS). The technique allows for rapid quantitative
elemental depth profiling. Fresh washed and unwashed leaves (n
= 5) from the contaminated area were compared with those from an uncontaminated
area, analysing Ni and U at ten randomly chosen points on each leaf. Nickel
and U concentrations differed significantly between washed and unwashed
leaves from LTB. Particles on unwashed leaves measured up to 300 µm
in diameter, and were enriched with U. Uranium was detected on the surface
of the leaf, whereas Ni was detected within leaf tissues. In unwashed
L TB leaves, Ni and U concentrations did not significantly differ in areas
with and without visible particles, suggesting that there were much smaller
particles, indistinguishable at x 100 magnification, which contributed
to the overall metal burden. Washing removed the majority of the Ni and
U on the surface, but residual U and Ni was detected. Irregularities in
the leaf surface, such as scars from herbivory contained elevated U concentrations
despite a washing step, presumably from trapping soil particles. Laser
ablation ICP-MS revealed that mass loading makes a significant contribution
to the contaminant burden of understory plants at L TB.
SREL Reprint #2720
Punshon, T., B. P. Jackson, P. M. Bertsch and J. Burger. 2004. Mass loading of nickel and uranium on plant surfaces: application of laser ablation-ICP-MS. Journal of Environmental Monitoring 6:153-159.
