Mari Lucia Campos

Baseline Concentration of Heavy Metals in Brazilian Latosols

Knowledge of baseline concentrations for heavy metals of environmental and agricultural concern in tropical soils is meager. Latosols are highly weathered soils that cover ∼40% of the Brazilian territory and are by far the most important agricultural soil order in Brazil. This paper aimed to compare two methods for heavy metal extraction from soils, and to provide baseline values of heavy metals for Brazilian Latosols. The soil samples came from the 0–0.2-m layer of 19 different Latosols from the various geographic regions of Brazil. The first experiment compared the USEPA method 3051A (microwave digestion with concentrated HNO3 in closed vessels) with the aqua regia extraction (hot plate digestion with concentrated HCl and HNO3, 3:1, in open vessels) regarding Pb determination. The second analyzed contents of Cd, Cu, Ni, Pb, and Zn, and for this the USEPA method 3051A was used. Heavy metal contents were assessed by flame atomic absorption spectroscopy. Although both methods were highly correlated, the USEPA-3051A rendered Pb contents 29% higher in average than the aqua regia. Average (n=57) and standard deviation values for heavy metals in Brazilian Latosols are 0.66±0.19 mg Cd kg−1, 65±74 mg Cu kg−1, 18±12 mg Ni kg−1, 22±9 mg Pb kg−1, and 39±24 mg Zn kg−1. Considerably variation is due to the inclusion of Latosols derived from a variety of parent materials. The values provided could be useful as reference baseline concentrations for heavy metals in Brazilian Latosols.

Determinação de cádmio, cobre, cromo, níquel, chumbo e zinco em fosfatos de rocha

The possibility of food chain transfer is a matter of concern on studies related to heavy metals in mineral fertilizers. The objective of this paper was to determine the content of heavy methods and to compare three extraction procedures (Embrapa, 1999; USEPA 3051A and USEPA 3050B) for Cd, Cr, Cu, Ni, Pb, and Zn in national and imported rock phosphates. The quantification of the trace elements content was performed by air-acetylene flame atomic absorption spectroscopy. Among the studied phosphates, the thermophosphate presented significantly greater concentrations of Cd, Cr, Cu, Ni, and Zn whereas Cu, Ni, Pb, and Zn were found in greater contents in the natural phosphate 2. The reactive phosphate 3 presented the greatest quantity of Cd (145±13 mg kg-1) and the natural phosphate 2, the highest quantity of Pb (234±9 mg kg-1). The tested methods can be applied in studies concerning heavy metals in phosphate fertilizers.

RELAÇÃO ENTRE O TEOR ABSOLUTO E RELATIVO DE CLOROFILA EM FOLHAS DE VIMEIRO

The traditional methods for chlorophylls quantification in leaves are destructive, time consuming and expensive. One alternative to the destructive methods involve the use portable devices, such as the chlorophyll meter SPAD-502, which measure the green color intensity of the leaves, by providing the SPAD (Soil Plant Analysis Development) index. However, the SPAD index must be adjusted to the chlorophylls content in the leaves of concerned specie. The objective of this work was to calibrate the SPAD index to quantify the chlorophylls content in leaves of osier ( Salix viminalis ). Leaves with colors ranging from yellow-green (chlorotic) to dark green were individually assessed with the SPAD-502 and, thereafter, destructively assessed for contents of chlorophylls a, b and total, expressed in terms of area and fresh mass of the leaves. There was a high determination coefficient (R 2 ) between the SPAD index and the contents of chlorophylls a, b and total in the leaf, expressed in µg cm -2 of leaf area (R² of 0.86, 0.88 and 0.93, respectively) and of between the SPAD index and the contents of chlorophylls a and total, expressed in µg g -2 fresh weight (R² of 0.81 and 0.79, respectively). The results show the chlorophyll meter SPAD-502 is a suitable alternative to the destructive method to quantify chlorophylls (in area basis; µg cm -2 ) in leaves of osier.