3º Encontro Brasileiro sobre Especiação Química
27 – 30 de novembro de 2012
Bento Gonçalves - RS
Monitoring Mercury in size fractionated road dust samples by flow
injection-cold vapor-atomic absorption spectrometry. Where is Hg
coming from?
Agustín Londonio1, Fabián Fujiwara1,2, Raúl Jiménez Rebagliati1, Darío Gómez1,
Patricia Smichowski1,2
smichows@cnea.gov.ar
1 - Comisión Nacional de Energía Atómica, Gerencia Química, 2Consejo Nacional de
Investigaciones Científicas y Técnicas (CONICET)
An investigation was carried out to explore the effect of citric, hydrochloric, oxalic and tartaric
acids on Hg vapor generation of in a flow injection system in conjunction with atomic
absorption spectrometry detection (CV-AAS) for its determination in road dust samples [1].
Samples were collected in Buenos Aires (Argentina) during two months at 15 sites grouped
in five zones with different urban characteristics and traffic profile. They were fractionated in
four fractions (with the following particle diameter (d): A: d < 37 µm, B: 37 < d < 50 µm, C: 50
< d < 75 µm, and D: 75 < d < 100 µm) before Hg determination. The operating conditions
(chemical and physical parameters) and the type and concentration of the acids studied
(citric, hydrochloric, oxalic and tartaric) were assessed for the efficient generation of Hg. The
interfering effect of metals and metalloids, present as minor and major concentrations in road
dust, on Hg signal were evaluated using the four acids. Hydrochloric acid resulted to be the
most convenient reaction medium in terms of sensitivity but a suitable control of interferences
was not reached. For a complex matrix such as road dust, the best control of interferences
was achieved when oxalic acid was tested, even when lower Hg signal were obtained in
comparison with HCl. The detection limit (3σ criterion) turned out to be 0.3 ng g-1. For
checking accuracy, two certified reference materials were analyzed and results were in good
agreement with certified values. Mercury concentrations in road dust ranged between 0.1 µg
g-1 and 4.6 µg g-1 and the mean concentration value resulted to be 1.09 µg g-1. In general, the
finer fractions (A, B) exhibited higher Hg concentrations than the coarser ones (C, D), with
average concentrations (µg g-1) in the order: A (1.5) ~ B (1.6) > C (0.6) = D (0.6). Mercury
data obtained were analyzed statistically together with the other 14 elements measured in
the same samples to find a common pattern. Mercury correlated with S and Zn (present in
liquid fuels). No significant correlations were detected between Hg and other traffic related
elements such as Cd, Cu, Mo, Pb and Sb that are mostly associated with mechanical wear.
These characteristics allow us to link the presence of Hg in Buenos Aires road dust with
exhaust of liquid fuel combustion from vehicles.
References
[1] Londonio, A.; Fujiwara, F.; Jiménez Rebagliati, R.; Gómez, D.; Smichowski, P.; Microchem., 2012,
doi:10.1016/j.microc.2012.03.014