Maria Alice Santanna

Using a two site-reactive model for simulating one century changes of Zn and Pb concentration profiles in soils affected by metallurgical fallout.

Predicting the transfer of contaminants in soils is often hampered by lacking validation of mathematical models. Here, we applied Hydrus-2D software to three agricultural soils for simulating the 1900-2005 changes of zinc and lead concentration profiles derived from industrial atmospheric deposition, to validate the tested models with plausible assumptions on past metal inputs to reach the 2005 situation. The models were set with data from previous studies on the geochemical background, estimated temporal metal deposition, and the 2005 metal distributions. Different hypotheses of chemical reactions of metals with the soil solution were examined: 100% equilibrium or partial equilibrium, parameterized following kinetic chemical extractions. Finally, a two-site model with kinetic constant values adjusted at 1% of EDTA extraction parameters satisfactory predicted changes in metal concentration profiles for two arable soils. For a grassland soil however, this model showed limited applicability by ignoring the role of earthworm activity in metal incorporation.

Tampão Santa Maria (TSM) como alternativa ao tampão SMP para medição da acidez potencial de solos ácidos

The SMP buffer contains p-nitrophenol and potassium chromate, both hazardous substances. A solution without toxic substances, the so-called Santa Maria buffer (TSM) was developed to reproduce performance of the SMP buffer used to estimate potential acidity of soils in Rio Grande do Sul and Santa Catarina (SMP-RS/SC). Acid titrations of the SMP- RS/SC buffer and various mixtures of the components of the new buffer were performed, using multiparametric regression analysis to obtain the optimal TSM composition. The efficiency of TSM in reproducing SMP-RS/SC was tested in 21 soils from Rio Grande do Sul and the Cerrado. The potential acidity was measured by wet incubation with calcium carbonate. The soil-buffer pH obtained with TSM and the SMP-RS/SC pH values were similar, and consequently the values of potential acidity and lime recommendations were similar as well. The TSM can be used instead of SMP-RS/SC, without the need to change laboratory interpretations to estimate the potential acidity or lime requirement of soils.

Evaluation of Sikora instead of SMP buffer to estimate the potential acidity of brazilian soils

Despite the efficiency of the Shoemaker, McLean, Pratt (SMP) buffer method in estimating soil acidity, the presence of p-nitrophenol and potassium chromate in the solution, both hazardous substances, has caused increasing environmental concerns. The purpose of this study was to test Sikora method (Sikora, 2006) as an alternative to the adapted SMP buffer method, generally used to estimate potential acidity of Southern Brazilian soils. For the test, 21 soils in the South and Cerrado regions of Brazil were sampled. (1) The potential acidity values of these soils range from 35.95 to 4.02 cmolc kg-1 of soil, reflecting a wide acidity variation. The Sikora buffer does not mimic the adapted SMP buffer used in Southern Brazil, since the former has a low ability to distinguish soils with different acidity from each other, probably due to the higher buffer capacity than of the adapted SMP solution.