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Transferência química na cadeia solo-mandioca-cabelo humano na região de Caxiuanã (Estado do Pará) e sua importância ambiental
(Universidade Federal do Pará, 2008-05-02) CARMO, Marciléia Silva; KERN, Dirse Clara; http://lattes.cnpq.br/8351785832221386; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
In the area of Caxiuanã, State of Pará, stands out the occurrence of several sites with soils type Amazon Dark Earth (TPA). They are dark soils characterized by the presence of ceramic fragments and high concentrations of Ca, Mg, Mn, P, Zn and C, when compared with other soils of Amazonia. They are fertile soils used for subsistence agriculture, mainly the cassava (Manihot esculenta Crantz). In attempt to know the physical, chemical, mineralogical and fertility characteristics of these soils and the interrelations between these and the adjacent areas (AD), cultivated or not with cassava, as well as the capacity of adsorption of nutrients and possible potentially toxic metals by the cassava and the transfer to the human body using hair analysis (mineralogram) the present work was developed. Aiming these results, sites were selected with TPA with and without cassava roçado (TPA/CR and TPA/SR) and adjacent areas also with or without cassava roçado (AD/CR and AD/SR). Samples of soils and cassava including the roots (tubers), leaves and tucupi were collected in the ranches with AD and without AD. Samples of human hair were collected of the riverine population that consumes the cassava of the studied roçados, here denominated: TPA family, those who live in TPA/CR areas; and AD family, those who live in AD/CR areas. The soil samples were submitted to grain size (humid-via), mineralogical (XRD), and chemical (ICP-MS of major, minor and trace elements) besides the fertility analysis. In the cassava samples (roots and leaves) the macronutrients (P, K, Ca, Mg, S), micronutrients (Fe, Mn, Zn, Co, B, Cu, Mo and Ni), non-nutrients and the toxic elements (Pb, Cd, Ce, Sn, Sc, Cr, Zr, Sr, Ba, Al, Na, Hg, Se and As) were determinate by ICP-MS. In hair samples, the essential (S, Ca, Zn, Mg, Cu, Se, Sr, Mn, B, I, Cr, V, Co and Mo), additional (P, Fe, Na and K) and toxic elements (Pb, Bi, Al, Ba, Hg, Ni, Sn, Sb, As, Cd, Ag, U and Th) were also determinate by ICP-MS, what characterize the mineralogram, and correspond to most of elements analyzed in the soils and cassava. The soils are mainly composed by quartz, kaolinite and hematite + goethite, and accessories as anatase, muscovite / illite and zircon. This way they are constituted mainly by SiO2 and Al2O3, besides Fe2O3, TiO2, K2O and Zr. The tendency to the decrease of Al2O3 and Fe2O3 concentrations and the increase of SiO2 concentrations and lots of ignition from B-horizons to A-horizons is really according to the classic evolution of the soils under tropical climate with tropical forest covering. The studied ADEs present pedologic profile similar to other TPAs with high contents of organic carbon and to other TPAs in A-horizons. The concentrations of total Ca, Mg, Mn, Zn and P are relatively high when compared to the Amazonian soils, one of the great distinctions among TPA soil and the adjacent area, and compared to the TPA soils of Caxiuanã and other areas of Amazonia. However, the available P contents are lower, due to the continuous use of TPA in agriculture of roçado. Therefore, as expected, it is probable that the use of TPA in agriculture of roçado is progressively exhausting the nutrient reserves, but in less intensity than the common soils of Amazonia. The chemical analyses of the cassava show that the macronutrients and micronutrients are mainly concentrated in the leaves, and the concentrations do not depend on the soil in which it was cultivated, TPA or AD. In the root (pellicle, skin and pulp) with lower contents than in the leaves, the analyzed elements are mainly concentrated in the pellicle. The non-nutrient and toxic elements found in the cassava are mainly concentrated in the pellicles, followed by the leaves, skin and pulp. The pulp -the part of the cassava used in the human diet - therefore is impoverished in macro and micronutrients, as well as in non-nutrient and toxic elements. The tucupi - the liquid phase - presents low concentrations of the analyzed elements (nutrients, non-nutrients and toxic), while the solid extract is especially composed by C, K, Mg, P and Ca, besides Na, as oxalates and phosphates. The transfer factor (TF) from the soils to the cassava cultivated in TPA and AD areas was elevated in relation to macronutrients (K, Ca, Mg and P), mainly in the leaves, and medium to micronutrients (Fe, Mn, Zn, Co, Mo and Ni) being higher in the cassava cultivated in AD areas due to the lower content of those elements in AD soils and also to the fact that the cassava absorbs only the substances necessary to the basic physiologic function. This way, it’s evident why TPA, much enriched in nutrients, is more appropriate for the agriculture in continuous cultivation of cassava. The hair mineralogram of the researched families of Caxiuanã shows that the variance of the concentrations of the essential and additional elements is higher in TPA than in AD family, while the average concentrations were similar in the two families. On the other hand, the concentrations of toxic elements are relatively higher in the AD family, mainly Pb and Al. The essential and additional elements contents are below the reference values while the toxic elements Al, Pb, Sb and Ba, are above the range of normal values. The concentrations of the essential and additional elements are cumulative with the age. The concentrations of Fe, Al and Bi are higher in the children, therefore susceptible to toxic elements (Al and Bi). According to the sex, the essential, additional and toxic elements are more concentrate in women. The concentrations of essential and additional elements, mainly Mg, Zn, Ca, Sr, Se, Co and P are lower, and of toxic elements Ni, Pb, Sb and As are higher in smokers. This suggests that the habit of smoking possibly inhibits the absorption of most of the elements essential to the capillary formation. Probably due to the possible coexistence with smokers, high concentrations of Ni, Pb, Sb and As were found in among several children, being considered passive smokers. Among the identified geochemical associations, Hg-Sb-Ag-Zn-Bi-Pb-Se-Cd association reflects the smokers. The obtained data of this work and its discussion show that the TPA soils are in fact fertile and the adjacent areas (AD) are relatively impoverished, and the TPA soils enriched in nutrients allow the continuous cultivation of cassava that absorbs from the soil only the necessary for its physiologic function. The pulp of the cassava leaves - more consumed by the man, impoverished in macro and micronutrients - contributes to the poor diet of the riverine population of Caxiuanã. The chemical composition of the cassava didn't show dependence with the soil type (TPA or AD). The chemical composition of the hair of the population of Caxiuanã that feed on cassava cultivated in TPA and AD areas confirms the poor alimentary diet. The mineralogram also shows that the principal external factor of contamination is the tobacco, and perhaps the kitchen aluminum utensils. So the mineralogram is used as a valuable tool to evaluate environmental impacts related to the human health. Therefore, the problems related to the human health in the area of Caxiuanã are in part due to the poor alimentary diet and the habit of smoking, because the soils don't present evidences of anthropic impacts neither of geogenic anomalies.