Adsorption/desorption of arsenic by tropical peat: influence of organic matter, iron and aluminium

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Absorção e níveis críticos de fósforo na parte aérea da mamoneira cultivada em diferentes classes de solos

Soil that has a high degree of weathering, with more inorganic P bound to Fe and Al oxides, has less P availability to plants. Thus, the critical element of a plant refers to the level below which the growth rate and plant production decreases, demonstrating the need for supplementary fertilization. Accordingly, an experiment was conducted in a greenhouse at Embrapa Algodao with the objective of evaluating the response of castor plants to five doses of P in four types of soil with different adsorption characteristics and critical levels of foliar P. The experimental design was completely randomized in a 4 x 5 factorial design, four types of soil and 5 levels of P with four replications. For TCo, there was an increase in height growth, with dose of 229.6 mg dm(-3) responsible for maximum plant height (74.3 cm). The largest diameter stem (17.58 mm) was observed in CXve with an application of 229.6 mg dm(-3) of P; a decrease was seen when using higher doses. The increase in leaf area was smaller in RY (4724.8 cm(2)), where it was obtained with a dose of 280.2 mg dm(-3). In general, critical levels of P in the plant shoots did not vary much between the soils. The critical level of P in castor bean shoot dry mass was higher (4.61 g kg(-1)) in TCo, this result being directly related to the low clay content of the soil.

Empobrecimento e podzolização de solos lateríticos da bacia do Rio Negro e gênese dos podzóis na alta Bacia da Amazônia

Pós-graduação em Geografia - IGCE

Geoquímica de perfis lateríticos na chapada sedimentar do Triângulo Mineiro

The ferruginous sandstone (Serra da Galga member) from Marilia formation present in sedimentary mining triangle plateaus - MG (southeast Brazil) is still not properly characterized, as well as the presence of a rich layer Fe nodules which is not properly understood, as are the alteration products of this material that may be linked to the presence of refractory clays which are characterized by intimate relationship between Fe and Al. Aluminum is widely present on top of these plateaus. This course conclusion paper characterized the mineralogy and distribution of smaller elements both rust sandstone evolved as soil above this sandstone. The characterization has been done by using X-ray fluorescence techniques (XRF), the iron was removed by using the CBD method (dithionito-citratebicarbonate), and X-ray diffraction (XRD) and analysis of the products extracted by the CBD method by ICP- OES were made to characterize the material. The results of the XRF show great variation of Al and Si, Fe with almost constant behavior in the average depth of 110 cm, where it has the highest concentration levels. Fe appear associated with the V and Ce. CDB results show a clear relation of Fe with Al. Al does not have in this case compared with Cr or any other item. The concentration of extracted Al was always below the concentration of Fe. In the region, the formation of this Latosols- Gleysols system is subject to topography and its influence on local water regime, a regime that has direct influence on the formation of supergene accumulations as in the area and results in aluminum accumulation in refractory clays exploited by IBAR mining

Phosphorus Availability in an Oxisol Amended with Biosolids in a Long-Term Field Experiment

Many extractors are used to quantify available P in soils, but few studies have assessed the availability of P in soils of the wet tropics amended with high rates of biosolids. In this study, ion exchange resin, Mehlich-1 solution, and Fe-impregnated strips were used to quantify available P in samples from an Oxisol amended with surface-applied biosolids in a long-term field experiment. The soil's maximum capacity for P adsorption was also estimated. Experimental design consisted of randomized blocks, with four treatments and three replicates. Samples of biosolids were collected every year during the experiment, from 1999 to 2002. In 1999, two applications were made before growing maize (Zea mays L.) in austral summer and winter. Treatments were: Control (no biosolids added); B (biosolids added at rates based on their total N content); B2 (biosolids added at twice the rate of B), and B4 (biosolids added at four times the rate of B). Soil samples were collected at 0- to 0.1-, 0.1- to 0.2-, and 0.2- to 0.4-m depths. Biosolids were broadcast applied and incorporated into the soil to a depth of 0.2 m using a rotary hoe. The Oxisol had a high P-adsorption capacity (around 2450 mg kg(-1)) because of its high contents of clay and Fe and Al oxides. All the extractors were effective at assessing P availability and were positively correlated among themselves. Available P soil contents correlated positively with P content in maize leaves and grains, and the resin method yielded the highest correlation with P contents in leaves and grains.

Seasonal Distribution of Airborne Trace Elements and Water-Soluble Ions in Sao Paulo Megacity, Brazil

This study deals with the seasonal distribution of Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn and water soluble ions (Cl-, PO43-, NO3-, SO42-, HCOO-, CH3COO-, oxalate, succinate, Na+, NH4+, K+, Mg2+ and Ca2+) found in PM10 samples (particulate matter less than 10 mu m in diameter) Sao Paulo City, Brazil, (April 2003-May 2004). Higher atmospheric levels were found for SO42-, NO3-, Cl- and PO43- while the main organic anions were oxalate and formate. Atmospheric levels for elements were: Fe > Al > Ca > K > Na > Mg > Zn > Cu > Pb. Some sources were predominant for some species: (i) fuel burning and/or biomass burning (NO3-, HCOO-, C2O42-, K+, Mg2+, Ca2+, Fe, Pb, Zn, Al, Ca, K and Mg), (ii) gas-to-particle conversion (SO42- and NH4+) and (iii) sea salt spray (Cl-, Na+ and Na).

Metalli nel particolato atmosferico: distribuzione granulometrica e valutazione del contributo della combustione di biomasse

La tossicità delle polveri atmosferiche è associata sia alla natura granulometrica sia al carico di contaminanti, da qui la necessità di investigare oltre la concentrazione delle PM in atmosfera anche la loro composizione chimica. In questo studio è stata effettuata una prima caratterizzazione da un punto di vista sia granulometrico che chimico del particolato atmosferico campionato in una zona suburbana di Riccione (Castello degli Agolanti). In particolare sono state determinate le concentrazioni di metalli quali Pb, Cd, Ni, Zn, Cu, Fe e Al nel PM 2,5 PM 10 e PM totale. Inoltre, dato che uno degli scopi dello studio è quello di verificare il contributo della combustione di biomasse sul carico complessivo di contaminanti, il periodo di campionamento comprende il giorno delle Fogheracce, festa popolare in cui vengono accesi diversi falò all’aperto. Complessivamente sono stati prelevati 13 campioni di 48 ore per ogni frazione granulometrica dal 9 Marzo all’8 Aprile 2011. Dallo studio emerge che nel periodo di campionamento, mediamente il contributo antropogenico è dominante per Pb, Cd, Ni Cu e Zn dovuto principalmente al traffico veicolare. Tali metalli, ad eccezione del Cu infatti si concentrano nel particolato più fine. Al e Fe invece sono principalmente marker delle emissioni crostali e si concentrano nella frazione grossolana. Interessante quanto registrato nella giornata delle Fogheracce. Oltre ad una variazione nel contenuto relativo dei metalli con un forte arricchimento di Pb e Al, per quest’ultimo si nota anche un forte incremento della sua concentrazione nella frazione PM2.5 ad indicare una diversa sorgente emissiva. Si evidenzia in questo studio un importante contributo nel carico di inquinanti da parte di combustioni di biomasse all’aperto.

Fruit yield and growth parameters of several Carica papaya L. genotypes in a temperate climate

The aim of this work was to evaluate changes in growth and productivity parameters of different precocious hybrids and a naturalized variety of papaya under both greenhouse and field cultivation in a temperate climate (the center of the province of Santa Fe, Argentina). In view of the aforesaid, the purpose of our research was to identify further genotypes better suited for the cultivation of this species in temperate climates and demonstrate the need for the use of semi-controlled systems to make possible the cultivation of these promising genotypes in middle latitudes. The average yield was 291% higher in greenhouse than in the field. The average productivity for hybrid genotypes compared with the naturalized variety more than doubled in both environments. Considering behavior in height, leaf area index and yield parameters, hybrids H2 (principally), and H4 showed a great adaptation for use in semi-forced systems. The use of greenhouse and short stature papaya hybrids allows its feasible and surely profitable cultivation in non- tropical climates.

Sesquióxidos de hierro en bosques templado húmedos del estado de Hidalgo, México

Se estudian las formas de hierro extraídas con oxalato ácido de amonio, pirofosfato de sodio, ditionito-citrato-bicarbonato, así como el hierro total en disolución en suelos Alisoles en el municipio de Acaxochitlán, Hidalgo, México. Los suelos estudiados soportan distintos tipos de vegetación forestal: Pinus patula Schlecht and Cham (Pp), Pinus teocote, (Pt) y Quercus spp, (Q). El objetivo del trabajo fue determinar si la vegetación influye significativamente sobre las diferentes fracciones de hierro (Fe) en el suelo. Los contenidos de Fe total son significativamente mayores en suelos bajo vegetación de Pp (14,5% de Fe2O3), el mayor porcentaje de ferrihidrita (38,0% del Fe total en suelo) y de complejos organominerales de Fe y óxidos amorfos de Fe (20,9% y 16,3% respectivamente del Fe total en suelo, se dio en el bosque de Pt. En los suelos bajo bosques de Pp predominaron formas de Fe lábil (56,7% del Fe total en suelo) y formas cristalinas de Fe (goetita/hematita). La vegetación de Q mostró mayor alteración de los suelos y en el caso de Pt y Pp se presentó una mayor evolución en el proceso de organización estructural de los oxihidróxidos de Fe. El tipo de vegetación forestal influye en el grado de evolución del suelo, y en la distribución, contenido y formas de óxidos de Fe. En un orden de mayor a menor el contenido de Fe total en el suelo fue Pinus patula > Quercus spp > Pinus teocote.

Reconstruction of the provenance and distribution of terrigenous sediments off NE South America over the last 30ka

We investigate the redistribution of terrigenous materials in the northeastern (NE) South American continental margin during slowdown events of the Atlantic Meridional Overturning Circulation (AMOC). The compilation of stratigraphic data from 108 marine sediment cores collected across the western tropical Atlantic shows an extreme rise in sedimentation rates off the Parnaíba River mouth (about 2°S) during Heinrich Stadial 1 (HS1, 18-15 ka). Sediment core GeoB16206-1, raised offshore the Parnaíba River mouth, documents relatively constant 143Nd/144Nd values (expressed as epsilonNd(0)) throughout the last 30 ka. Whereas the homogeneous epsilonNd(0) data support the input of fluvial sediments by the Parnaíba River from the same source area directly onshore, the increases in Fe/Ca, Al/Si and Rb/Sr during HS1 indicate a marked intensification of fluvial erosion in the Parnaíba River drainage basin. In contrast, the epsilonNd(0) values from sediment core GeoB16224-1 collected off French Guiana (about 7°N) suggest Amazon-sourced materials within the last 30 ka. We attribute the extremely high volume of terrigenous sediments deposited offshore the Parnaíba River mouth during HS1 to (i) an enhanced precipitation in the catchment region and (ii) a reduced North Brazil Current, which are both associated with a weakened AMOC.

Chemistry and accumulation rates of Jurassic to early Cretaceous sediments from the central equatorial Pacific

Sedimentation in the central Pacific during the Jurassic and Early Cretaceous was dominated by abundant biogenic silica. A synthesis of the stratigraphy, lithology, petrology, and geochemistry of the radiolarites in Sites 801 and 800 documents the sedimentation processes and trends in the equatorial central Pacific from the Middle Jurassic through the Early Cretaceous. Paleolatitude and paleodepth reconstructions enable comparisons with previous DSDP sites and identification of the general patterns of sedimentation over a wide region of the Pacific. Clayey radiolarites dominated sedimentation on Pacific oceanic crust within tropical paleolatitudes from at least the latest Bathonian through Tithonian. Radiolarian productivity rose to a peak within 5° of the paleoequator, where accumulation rates of biogenic silica exceeded 1000 g/cm**2/m.y. Wavy-bedded radiolarian cherts developed in the upper Tithonian at Site 801 coinciding with the proximity of this site to the paleoequator. Ribbon-bedding of some radiolarian cherts exposed on Pacific margins may have formed from silicification of radiolarite deposited near the equatorial high-productivity zone where radiolarian/clay ratios were high. Silicification processes in sediments extensively mixed by bioturbation or enriched in clay or carbonate generally resulted in discontinuous bands or nodules of porcellanite or chert, e.g., a "knobby" radiolarite. Ribbon-bedded cherts require primary alternations of radiolarian-rich and clay-rich layers as an initial structural template, coupled with abundant biogenic silica in both layers. During diagenesis, migration of silica from clay-rich layers leaves radiolarian "ghosts" or voids, and the precipitation in adjacent radiolarite layers results in silicification of the inter-radiolarian matrix and infilling of radiolarian tests. Alternations of claystone and clay-rich radiolarian grainstone were deposited during the Callovian at Site 801 and during the Berriasian-Valanginian at Site 800, but did not silicify to form bedded chert. Carbonate was not preserved on the Pacific oceanic floor or spreading ridges during the Jurassic, perhaps due to an elevated level of dissolved carbon dioxide. During the Berriasian through Hauterivian, the carbonate compensation depth (CCD) descended to approximately 3500 m, permitting the accumulation of siliceous limestones at near-ridge sites. Carbonate accumulation rates exceeded 1500 g/cm**2/m.y. at sites above the CCD, yet there is no evidence of an equatorial carbonate bulge during the Early Cretaceous. In the Barremian and Aptian, the CCD rose, coincident with the onset of mid-plate volcanic activity. Abundance of Fe and Mn and the associated formation of authigenic Fe-smectite clays was a function of proximity to the spreading ridges, with secondary enrichments occurring during episodes of spreading-center reorganizations. Callovian radiolarite at Site 801 is anomalously depleted in Mn, which resulted either from inhibited precipitation of Mn-oxides by lower pH of interstitial waters induced by high dissolved oceanic CO2 levels or from diagenetic mobilization of Mn. Influx of terrigenous (eolian) clay apparently changed with paleolatitude and geological age. Cyclic variations in productivity of radiolarians and of nannofossils and in the influx of terrigenous clay are attributed to Milankovitch climatic cycles of precession (20,000 yr) and eccentricity (100,000 yr). Diagenetic redistribution of biogenic silica and carbonate enhanced the expression of this cyclic sedimentation. Jurassic and Lower Cretaceous sediments were deposited under oxygenated bottom-water conditions at all depths, accompanied by bioturbation and pervasive oxidation of organic carbon and metals. Despite the more "equable" climate conditions of the Mesozoic, the super-ocean of the Pacific experienced adequate deep-water circulation to prevent stagnation. Efficient nutrient recycling may have been a factor in the abundance of radiolarians in this ocean basin.

Composition and alteration of volcanic rocks of ODP Hole 119-738C

During ODP Leg 119 one basement hole was drilled at Site 738, on the Southern Kerguelen Plateau. The 38.2 m of basement rocks drilled comprises three basaltic aa-lava flows with basal and top breccias, overlain by Turanian marine carbonates. Site 738 basalts probably erupted near a fracture zone, and were emplaced during the plateau-forming stage of Kerguelen Plateau evolution under quiet, subaerial to shallow water conditions. The basalts are T-MORB, chemically resembling Mesozoic continental flood basalts of the southern hemisphere. Two slightly different magma batches are distinguished by Fe, Ti, Al, Zr, and REE concentrations. Prior to eruption, the magmas had undergone significant olivine and some clinopyroxene fractionation. Incompatible and immobile trace element concentrations and ratios point to a veined upper mantle source, where a refractory mineral assemblage retains Nb, Ta, and the HREE. The basaltic melts derived from this regionally veined, enriched upper mantle have high LREE, and especially Ba and Th concentrations and bear the DUPAL isotopic signature gained from deep- seated, recycled, old oceanic(?) crust. A saponite-celadonite secondary mineral assemblage confines the alteration temperature to <170°C. Alteration is accompanied by net gains of H2O, CO2, K2O, and Rb, higher oxidation, minor Na2O, SiO2 gains, and losses of V and CaO. Released Ca, together with Ca from seawater, precipitated as calcite in veins and vesicles, plumbed the circulation system and terminated the rock/open seawater interaction.

Major and rare earth element contents and their speciations in ferruginous nodules and host sediments from the Barents Sea

Contents of Fe, Mn, Al, P, and rare earth elements (REE) in ferruginous nodules and host sediments of the eastern Barents Sea were studied. A direct Fe-P correlation in reactive components of the sediments and nodules was found. The nodules were shown to be formed through Fe(II) oxidation in the surface layer of sediments and cementation of terrigenous fraction of sediments by Fe(III) oxyhydroxides. The latter accumulate phosphorus due to processes of sorption - co-precipitation, by forming Fe(III) hydrophosphates. REE composition in the sediments and nodules normalized to NASC contents is characterized by increased proportion of light REE that may be caused by regional features of their sources. Due to significant share of terrigenous matter in the Fe nodules (up to 65% for Nd), REE composition of bulk samples is similar to that of host sediments. A negative cerium anomaly in composition of reactive REE may result from REE sorption from seawater. REE bulk composition of a ferruginous crust is closer to that of seawater than one of the ferruginous nodules from the sediments because of essentially lower content of diluent terrigenous matter.

Geochemistry of ocean floor and forearc serpentinites

We provide new insights into the geochemistry of serpentinites from mid-ocean ridges (Mid-Atlantic Ridge and Hess Deep), passive margins (Iberia Abyssal Plain and Newfoundland) and fore-arcs (Mariana and Guatemala) based on bulk-rock and in situ mineral major and trace element compositional data collected on drill cores from the Deep Sea Drilling Project and Ocean Drilling Program. These data are important for constraining the serpentinite-hosted trace element inventory of subduction zones. Bulk serpentinites show up to several orders of magnitude enrichments in Cl, B, Sr, U, Sb, Pb, Rb, Cs and Li relative to elements of similar compatibility during mantle melting, which correspond to the highest primitive mantle-normalized B/Nb, B/Th, U/Th, Sb/Ce, Sr/Nd and Li/Y among subducted lithologies of the oceanic lithosphere (serpentinites, sediments and altered igneous oceanic crust). Among the elements showing relative enrichment, Cl and B are by far the most abundant with bulk concentrations mostly above 1000 µg/g and 30 µg/g, respectively. All other trace elements showing relative enrichments are generally present in low concentrations (µg/g level), except Sr in carbonate-bearing serpentinites (thousands of µg/g). In situ data indicate that concentrations of Cl, B, Sr, U, Sb, Rb and Cs are, and that of Li can be, increased by serpentinization. These elements are largely hosted in serpentine (lizardite and chrysotile, but not antigorite). Aragonite precipitation leads to significant enrichments in Sr, U and B, whereas calcite is important only as an Sr host. Commonly observed brucite is trace element-poor. The overall enrichment patterns are comparable among serpentinites from mid-ocean ridges, passive margins and fore-arcs, whereas the extents of enrichments are often specific to the geodynamic setting. Variability in relative trace element enrichments within a specific setting (and locality) can be several orders of magnitude. Mid-ocean ridge serpentinites often show pronounced bulk-rock U enrichment in addition to ubiquitous Cl, B and Sr enrichment. They also exhibit positive Eu anomalies on chondrite-normalized rare earth element plots. Passive margin serpentinites tend to have higher overall incompatible trace element contents than mid-ocean ridge and fore-arc serpentinites and show the highest B enrichment among all the studied serpentinites. Fore-arc serpentinites are characterized by low overall trace element contents and show the lowest Cl, but the highest Rb, Cs and Sr enrichments. Based on our data, subducted dehydrating serpentinites are likely to release fluids with high B/Nb, B/Th, U/Th, Sb/Ce and Sr/Nd, rendering them one of the potential sources of some of the characteristic trace element fingerprints of arc magmas (e.g. high B/Nb, high Sr/Nd, high Sb/Ce). However, although serpentinites are a substantial part of global subduction zone chemical cycling, owing to their low overall trace element contents (except for B and Cl) their geochemical imprint on arc magma sources (apart from addition of H2O, B and Cl) can be masked considerably by the trace element signal from subducted crustal components.

Oxygen isotope concentrations of minerals from the upper kilometer of the ocean crust, DSDP Hole 504B

DSDP Hole 504B is the deepest basement hole in the oceanic crust, penetrating through a 571.5 m pillow section, a 209 m lithologic transition zone, and 295 m into a sheeted dike complex. An oxygen isotopic profile through the upper crust at Site 504 is similar to that in many ophiolite complexes, where the extrusive section is enriched in 18O relative to unaltered basalts, and the dike section is variably depleted and enriched. Basalts in the pillow section at Site 504 have delta 18O values generally ranging from +6.1 to +8.5? SMOW (mean= +7.0?), although minor zeolite-rich samples range up to 12.7?. Rocks depleted in 18O appear abruptly at 624 m sub-basement in the lithologic transition from 100% pillows to 100% dikes, coinciding with the appearance of greenschist facies minerals in the rocks. Whole-rock values range to as low as +3.6?, but the mean values for the lithologic transition zone and dike section are +5.8 and +5.4?, respectively. Oxygen and carbon isotopic data for secondary vein minerals combined with the whole rock data provide evidence for the former presence of two distinct circulation systems separated by a relatively sharp boundary at the top of the lithologic transition zone. The pillow section reacted with seawater at low temperatures (near 0°C up to a maximum of around 150°C) and relatively high water/rock mass ratios (10-100); water/rock ratios were greater and conditions were more oxidizing during submarine weathering of the uppermost 320 m than deeper in the pillow section. The transition zone and dikes were altered at much higher temperatures (up to about 350°C) and generally low water/rock mass ratios (~1), and hydrothermal fluids probably contained mantle-derived CO2. Mixing of axial hydrothermal fluids upwelling through the dike section with cooler seawater circulating in the overlying pillow section resulted in a steep temperature gradient (~2.5°C/m) across a 70 m interval at the top of the lithologic transition zone. Progressive reaction during axial hydrothermal metamorphism and later off-axis alteration led to the formation of albite- and Ca-zeolite-rich alteration halos around fractures. This enhanced the effects of cooling and 18O enrichment of fluids, resulting in local increases in delta 18O of rocks which had been previously depleted in 18O during prior axial metamorphism.