Time evolution of Pb(II) speciation in pampa soil fractions

FERREYROA, GISELE V.; MONTENEGRO, ANDREA C.; TUDINO, MABEL B.; LAVADO, RAÚL S.; MOLINA, FERNANDO V.

CHEMICAL SPECIATION AND BIOAVAILABILITY

SCIENCE REVIEWS 2000 LTD

Lugar: Londres; Año: 2014 vol. 26 p. 210 - 218

0954-2299

Soil pollution by heavy metals, particularly lead is an important environmental concern; the bioavailability of such pollutants is strongly dependent on its chemical form. Here, the speciation of Pb(II) in soil fractions as a function of time shortly after its incorporation 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 but shows a lower and constant value in the winter run. A high proportion is found to be adsorbed onto the stable (aluminosilicates+quartz) mineral fraction. The results strongly suggest that, even at a short time after soil pollution with Pb, a high proportion is adsorbed onto the mineral fraction, with only a low fraction being bioavailable;. The most stable (mineral incorporated) form is observed to increase with time. Soil water content appears to be more important than temperature in determining the differences between the two