Jaime Wilson Vargas de Mello

Pedogenesis and pre-Colombian land use of “Terra Preta Anthrosols” (“Indian black earth”) of Western Amazonia

Abstract The “Terra Preta de Indio” (Indian black earth) or Terra Preta of Western Amazonia is a thick, dark-coloured, anthropic epipedon, usually rich in nutrients. It occurs mostly at the fringes of the Terra Firme, along the Amazon river banks, overlying deep strongly weathered soils. We studied selected chemical, physical and mineralogical properties of seven soils, ranging from the Tertiary Plateau down to the Amazon river floodplain in the Iranduba district, near Manaus, Amazonas, Brazil. Three Terra Preta soils were classified as anthropogenic (Anthropic Xanthic Kandiudult, Anthropic Xanthic Kandiudox and Anthropic Dystropepts). Chemical, mineralogical and micropedological attributes, such as high total and available P and mica flakes in pottery remains found in the Terra Preta, indicate that the origin of soil materials of these anthrosols is closely associated with neighbouring floodplain (varzea) soils and sediments. Amazon floodplain soils were the source of soil material for pottery, since 2:1 clay minerals are not found in the Tertiary Plateau (Terra Firme) sediments. Total and available P contents of Terra Preta are associated with microfragments of bone apatite with high P and Ca values. In the anthrosols under cultivation, these values are less, with increasing Al release suggesting acidification and losses of nutrients. Large amounts of Mn and Zn occur in the anthrosols and in high-fertility floodplain soils. It is unlikely that well-drained Tertiary Plateau (Terra Firme) area far away from lowland Amazon floodplain soils could develop high-fertility Terra Preta on the top of nutrient-poor Oxisols (Latosols). The suggested model of Terra Preta formation between the Tertiary Plateau and nutrient-rich Amazon floodplain does not extend to other nutrient-poor, smaller, floodplains draining the deep-weathered interfluves of the Brazilian Uplands. This raises reservations about estimates of precolonial human population densities for the Amazon basin as a whole, assuming the widespread occurrence of such anthrosols farther inland.

The role of Al-Goethites on arsenate mobility

The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As retained by the Fe compounds under anoxic conditions were investigated in this study. The (hydr)oxides were synthesised, and adsorption isotherms and As(V) adsorption maxima at different pH were measured. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens, and periodically sampled to evaluate the contents of soluble As and Fe. The As(V) adsorption maxima decreased in the following order: Fh > AlGt(13) > AlGt(20) > AlGt(23) > Gb > Hm > Gt. In terms of surface area, Gb, Gt, and Hm showed higher As(V) loading capacity than Fh, suggesting available reactive sites not fully occupied by arsenate on Fh. The same hypothesis can be considered for Al-goethites, as they showed even lower arsenate loading capacity per surface area. The presence of structural Al in the goethites enhanced considerably the As uptake capacity and stability under reducing conditions. Therefore, the Al-goethites showed good potential as adsorbents to remove As from water. S. putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing As into solution. Al-goethites showed a decrease in Fe and As mobilisation as structural Al increased.

REMOVAL OF Cu, Cr, Ni, Zn, AND Cd FROM ELECTROPLATING WASTES AND SYNTHETIC SOLUTIONS BY VERMICOMPOST OF CATTLE MANURE

ABSTRACT This study was undertaken to evaluate the retention of Cu, Cr, Ni, Zn, and Cd under laboratory conditions from synthetic solution and electroplating wastes by vermicompost. A glass column was loaded with vermicompost, and metal solutions were passed through it. Metal concentrations were then measured in the eluate in order to evaluate the amounts retained by the vermicompost. Measurements of pH, metal concentrations, moistness, organic matter and ash contents, and infrared and XRD spectroscopy were used for vermicompost characterisation. Vermicompost residues obtained from this process were used for plant nutrition in eroded soil collected from a talus near a highway. Metal retention (in g of metal/kg of vermicompost) from effluents ranged from 2 for Cr and Zn to 4 in the case of Ni. In synthetic solutions, the values for metal retention were 4 for Cd and Zn, 6 for Cu and Ni, and 9 for Cr. The results also showed that metal concentrations in the purified effluents were below the maximum values established for waste discharges into rivers by the Brazilian Environmental Standards. The relatively high available Cd concentration of the vermicompost residue resulted in plant damage. This effect was attributed to the presence of Cd in the synthetic solution passed through the vermicompost. The data obtained do not give a complete picture of using vermicompost in cultivated lands, but such values as are determined do show that it can be suitable to remove heavy metals from industrial effluents.

Dinâmica da mobilização de elementos em solos da Amazônia submetidos à inundação

Significant part of Amazonia soils stays partially or completely waterlogged for varying periods of days to months, as result of widespread inundation or drainage deficiency in some areas, causing changes in chemical, physical and biological properties. In this work, we aimed to evaluate the dynamics of mobilization of Al, Ca, Fe, K, Mg, Mn, Na, Si, P in soils subjected to controlled six months inundation. Soil solution aliquots were collected periodically during the inundation period, determining all elements in solution. The inundation influenced the kinetics of elements, increasing their mobilization, notably in the first weeks. Levels of Fe in solution were higher in soils with greater amounts of amorphous Fe. In soils with low amorphous Fe and low organic matter contents, mobilization of Fe was very low. Levels of P in solution were influenced by all P forms, but Fe-P forms exerted the greatest influence on mobilized P. Levels of Ca, Mg, K and Na in solution were directly influenced by their exchangeable levels, as well by the Mn and Fe kinetics.

Evaluation of Arsenic Availability in Sulfidic Materials from Gold Mining Areas in Brazil

This study is aimed at evaluating the availability and mobility of arsenic in sulfidic materials from gold mining areas in Minas Gerais State, Brazil. Eight extraction media were employed in a sequential extraction scheme, as follows: exchangeable As; strongly adsorbed As; As coprecipitated with acid-volatile sulfide, carbonates, MnO2, and Al2O3; As coprecipitated with amorphous iron; As linked to crystalline iron oxide; As coprecipitated with silicates; As coprecipitated with amorphous FeS2 and As2S3, and residual As, which was determined by GFAAS. Results demonstrated that in spite of differences in arsenic concentrations, the availability of the metalloid was found to be low for all samples. In general, arsenic was found in less available forms. Nevertheless, most of the arsenic in the environment is retained in the fractions 3, 4, and 5 which are susceptible to dissolution in acid medium, which in turn might be due to oxidation of the sulfide present in the samples.

Effects of Competing Anions and Iron Bioreduction on Arsenic Desorption

Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments, a process also controlled by the presence of competing anions. In this study, we investigated the decoupling of As from loaded Al and Fe (hydr)oxides by competing anions in the presence of iron-reducing bacteria. Hematite, goethite, ferrihydrite, gibbsite and three aluminium-substituted goethites (AlGts) were synthesised and loaded with arsenate, followed by anaerobic incubation with different phosphate or carbonate-containing media in the presence of catalytic iron-reducing bacteria. Soluble Al, As, Fe and P contents were measured in aliquots by inductively coupled plasma optical emission spectrometry following periodical sampling. Shewanella putrefaciens cells were able to utilise both non-crystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing Fe and As into solution. Phosphate and carbonate affected the Fe bioreduction, probably due to the precipitation of metastable mineral phases and also to phosphate-induced stabilisation on the hydroxide surfaces. Phosphate precipitation acted as a sink for As, thus limiting its mobilisation. The highest fraction of desorbed As by phosphate was observed for gibbsite, followed by AlGts. Similarly, gibbsite showed significant amounts of arsenate displaced by carbonate. In spite of its low crystallinity, ferrihydrite was the most efficient compound in retaining arsenate, possibly due to As co-precipitation. This study provides new insight into the management of As-contaminated soils and sediments containing Al-goethites and gibbsite, where the Fe activity may be too low to co-precipitate As-bearing vivianite. Thus, the dynamics of As(V) in flooded soils are significant in agriculture and environmental management.

Distribuição de freqüência de tamanho da fração areia e compacidade relativa de solos desenvolvidos de sedimentos do grupo geológico barreiras

The packing condition of the soil is important for providing direction for land management. In soils developed from recent sediments, the tendency to packing may be related to inherited characteristcs from sedimentation conditions. In a soil toposequence from sandy sediments of Barreiras geological group, in Caravelas city - Bahia, eight soil profiles were selected, five of them from a eucalypt plantation. The soils were allocated in five great groups: Fluvaquent (P1),Duraquod (P2, P8), Haplorthod (P3), Hapludult (P4, P5, P7) and Plintaquult (P6) according to the 7th approximation of USA soil taxonomy. Soil bulk density was determined in 41 horizons along with minimum and maximum soil bulk densities. Values of soil bulk densities were located between the two other densities, thereby obtaining the relative densities. The sand was subdivided into 21 size classes by standard sieves and the data were used to determine mean size, inclusive graphic standard deviation, inclusive graphic skewness and graphic kurtosis. It was observed that higher fine sand content combined with unsorted sand grains enhanced closer packing of soil particles, inducing increments of relative density in soil horizons more resistant to penetration.

Accumulation and spatial distribution of arsenic and phosphorus in the fern Pityrogramma calomelanos evaluated by micro X-ray fluorescence spectrometry

The accumulation and spatial distribution of arsenic and phosphorus in the As-hyperaccumulator fern Pityrogramma calomelanos were investigated by micro-energy dispersive X-ray fluorescence spectrometry (μ-EDXRF). Ferns were grown in half-strength Hoagland nutrient solution without and with 1.0, 10 or 30 × 10−3 mol L−1 As during three weeks. Microchemical As and P maps in different areas of the pinna were obtained by μ-EDXRF, and the same elements were also determined in pelletized powdered samples from the pinna, stipe and root. The reference method for the determination of As and P in the fern samples was a validated method based on microwave-assisted acid digestion followed by ICP OES analysis. Correlations between X-ray characteristic emission intensities and the corresponding As and P mass fractions obtained from the analysis of pelletized test samples exhibited linear correlation coefficients higher than 0.98 (n = 42). Better root mean square errors of prediction (RMSEPs) were obtained when different calibration models were built with pinna, stipe and root test samples separately. Arsenic was accumulated mainly in the pinna midrib, secondary veins, and apical and marginal regions of the pinnule of P. calomelanos, causing alterations in the P distribution. The proposed μ-EDXRF method is an appropriate analytical tool for simultaneously mapping As and P in P. calomelanos. In addition, useful information for either environmental monitoring or phytoremediation studies regarding As contamination is properly obtained.

A soil geochemical background for northeastern Brazil

Very few area-representative soil geochemical data exist for the southern hemisphere. A sub-continental scale (1.7 × 106 km2) geochemical sampling expedition in northeastern Brazil delivered 101 representative composite soil samples (30–50 cm depth) for non-anthropogenically influenced areas (mainly pasture land). Major, minor, and selected trace elements, determined by WD-XRF, are discussed with respect to lithology, soil type, biome type, climate and land use. These element concentrations vary up to two orders of magnitude, except for Si (factor ≅ 2.6). Silicon is strongly enriched compared to global averages, whereas most other components show a considerable deficiency. Significant deviations occur compared to results obtained from southern Brazil and from Australia – examples for the few representative data from the southern hemisphere. Anthropogenic influences appear negligible. All environmental parameters, except for land use, play an active role in shaping the geochemical composition. Lithology appears to be partly decoupled from the soils due to their age. The soil composition reflects soil type, biome type, and weathering influences. Most plant nutrients, despite their absolute depletion, show the highest values in Caatinga soils, and the lowest in Atlantic Forest soils. The new data form a robust and valuable tool to support future land use management.

Natural radionuclides and metals intake into soya, corn and lettuce grown on soil amended with phosphogypsum

Phosphogypsum is a by-product of the phosphate fertilizer industry. It is produced by precipitation during wet process of phosphate rocks, thus posing serious problems with its utilization and safe disposal. In Brazil, three main industries are responsible for the production and storage of about 5.5 × 106 tons per year. Phosphogypsum may contain trace metals and radionuclides of U and Th series. Since, in Brazil, phosphogypsum has been used for many years as soil amendment, it is important to know its availability in the environment. The main objective of this study is to evaluate the radionuclides and metals transfer in the soil-to-plant system. To accomplish this task an experiment was carried out in a green house, where two major crop groups (soya bean and corn) and leafy vegetables (lettuce) were grown in two types of soil (clay and sandy) amended with phosphogypsum. The transfer-factors were evaluated for the metals (As, Cd, Cu, Ni and Pb, Ba, Co, Cr, Fe, Zn and REE) and for the radionuclides U, Th, 226Ra, 228Ra, 210Pb and 210Po. The addition of PG to the two soils studied, did not significantly alter the TFs values for all the elements studied.