INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
?Time evolution of Pb(II) speciation in pampa soil fractions?.
Autor/es:
G.FERREYROA; A.MONTENEGRO; M. TUDINO; R. LAVADO; F. MOLINA
Lugar:
Bahìa Blanca
Reunión:
Congreso; XXIV Congreso Argentino de Cienicas del Suelo y II Reunión Nacional de Materia Orgànica y Sustancias Húmicas; 2014
Resumen:
Soil pollution by heavy
metals, particularly lead is an important environmental concern; the
bioavailability of such pollutants is strongly dependent on its chemical form,
thus it is expected that it will be modified by the soil composition and
climate conditions. Here, the speciation of Pb(II) in soil fractions as a function
of time is studied, using a selective sequential extraction method. The sample came
from an Argentinean Pampas region, and was extensively characterized, including
Rietveld analysis of the silt+clay fraction XRD pattern to find the major
mineral components. A shelter experiment was run twice, once in winter, once in
summer. The results show different speciation time profiles in both cases,
showing faster changes in winter due to higher water content. The summer
experiment corresponds to an earlier stage in the speciation profile evolution
compared with winter. The soluble/exchangeable fraction decreases with time in
summer (after 60 days decays, from an initial value of 21.4 %, to 11.5 %) but
shows a lower and relatively constant value in the winter run (10.3-9.6 %). A
high proportion is found to be adsorbed onto the stable
(aluminosilicates+quartz) mineral fraction (between 40 and 60 % approximately).
The results strongly suggest that, even at a short time after soil pollution
with Pb, only a low fraction is bioavailable (10.6 % on average). The most
stable (mineral incorporated) form is observed to increase with time (from 10 %
to about 20 %). Soil water content appears to be more important than
temperature in determining the differences between the two experiments.
Additionally, Pb speciation in a long-term polluted soil is being analyzed.