Page 31 - PR 2014 2016 07 Nuclear Science and Technology

Nuclear Science and Technology | Progress Report 173

Region indicated variability in the elements lichens collected from tree barks at different
concentrations with the proximity and in- sampling sites in the CUASO were cleaned,
tensity of the different emission sources and freeze-dried and ground for analyses. The
these results indicated four possible emission analytical methods of X - ray fluorescence
origins, such as vehicular plus soil resuspen- spectrometry (XRFS) and neutron activation
sion, industrial, marine aerosol and tree bark analysis (NAA) were applied to these analy-
composition itself. ses. Replicate analyses of a lichen sample by
XRFS and NAA, indicated good homogeneity of
the sample for the elements determined. The
lichen results showed that the mean concen-
trations of As, Br, Ca, Cd, Co, Cr, Cs, Rb, Sb, Se and
U were higher in samples from CUASO than
those from regions considered unpolluted. For
Fe, K, La, S, V and Zn, they were of the same
order of magnitude. For some elements, the hot
spots of their concentrations were probably
verified due to the dispersion of particulate
material from laboratory or incinerator emis-
sions and building constructions.

Production and characterization of
biological reference materials

A certified reference material (CRM) is a ref-
erence material accompanied by a certificate,
whose values are certified by a procedure
which establishes its traceability to an accu-
rate realization, in which the value is expressed
and each certified value is accompanied by an
uncertainty at a given level of confidence. Cer-
tified reference materials are still not widely
used in Brazil and other Latin American coun-
Fig 22. Radar chart of element concentrations in different
bark layers of Sibipiruna and Tipuana trees. Concentra- tries. The main reason is the high cost of these
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tions are given in µg kg unless indicated with asterisks materials, since most of them are imported.
(* - indicates concentration in mg kg and ** - in g kg ).
-1
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Reference materials are important tools in the
quality assurance of analytical results as they
Biomonitoring of chemical element are used in method validation, calibration of
pollutants using Epiphytic lichen instruments and in the realization of the trace-
ability of analytical results to stated references.
In this study, for passive biomonitoring of air The Neutron Activation Laboratory has been
pollution levels at the Cidade Universitária involved in the development of Brazilian bio-
Armando Salles de Oliveira (CUASO), Univer- logical reference materials, such as mussel and
sity of São Paulo campus, epiphytic lichens of fish with support of the International Atomic
Canoparmelia texana species were used. The Energy Agency (IAEA).