José Albertino Bendassolli

Dinâmica do ecótono floresta-campo no sul do estado do Amazonas no Holoceno, através de estudos isotópicos e fitossociológicos

This paper presents a comparative study between organic soil horizons formed in depressions located at the forest/savanna boundary in the Southern Amazon Basin. The influence of the paleovegetation dynamics, based on carbon isotope ( 12 C, 13 C and 14 C) data of soil organic matter (SOM) and plants was evaluated, as well as the present vegetation dynamics, inferred from the modern vegetation structure, composition and phytosociology. The uppermost soil horizon in savanna showed higher total carbon content than in forest. 13 C and 14 C data from soil samples indicated a predominance of C 3 plants in the early Holocene. About 7000 to 3000 14 C yr BP the influence of C 4 plants increased, indicating savanna expansion probably related to a drier climate in the region. Since approximately 3000 14 C yr BP, the carbon isotope data suggest the expansion of forest probably due to a wetter climate. The presence of typical boundary plant species (Sclerolobium paniculatum and Himatanthus sucuuba) in the savanna also suggested present forest expansion.

Sulfur isotope ratio (34S:32S) measurements in plant material by inductively coupled plasma mass spectrometry

The34S : 32S isotope ratio in plant material was determined using measurements at m/z 48 and 50, corresponding to the 32S16O+ and 34S16O+ species, respectively, by inductively coupled plasma mass spectrometry (ICP-MS). The sulfur species in aqueous solutions and plant digests were separated and pre-concentrated in an anion-exchange resin (AG1-X8) column inserted in a flow system. The isotope ratio measurements for a sulfur solution containing 17 mg l–1 was characterized by an RSD of <1%. Results for plant material enriched in 34S were in agreement with those obtained by magnetic deflection mass spectrometry using electron ionization at the 95% confidence level. A sample throughput of 45 h–1 was achieved.

Implantação de Programas de Gerenciamento de Resíduos Químicos Laboratoriais em universidades: análise crítica e recomendações

Laboratory Waste Management Programs have been established in several universities all over the world. These programs are important because they provide the understanding and protection of the environment, encouraging the waste generators responsibility and, mainly, accomplishing sustainable practice in the laboratory, in accordance with the Agenda 21. In this context, based on a literature review, the present work discusses the subject, introducing some recommendations to be applied in universities. A questionnaire applied to researchers of this area shows important information about the start of the programs, mainly difficulties, among other cares. This study allowed the proposition of basic rules about the establishment of laboratory waste management.

Nitrogen immobilization of urea and ammonium sulphate applied to maize before planting and as top-dressing in a no-till system

Ammonium sulfate (AS) and urea (U), labeled with 15N, were applied to no-till maize, 33 days before and 10 days after sowing, at a single rate of 80 kg ha-1 of N incorporated 5-7 cm deep along furrows spaced 0.8 m. Corn was sown after black oat (Avena strigosa Schieb.).The amount of immobilized N and of N-fertilizer recovered by corn plants was evaluated at the following plants stages: 4-5 leaves, 11-12 leaves, flowering, and at harvest. Treatments were applied in a randomized block design with three replications. The analysis of variance was performed based on one factorial scheme (2 x 6) with two sources in pre-planting (AS and U) on six sampling dates, and on a second (2 x 3) with two sources in top-dressing on three sampling dates. This field experiment was carried out on a Typic Acrustox in Uberlandia, Minas Gerais state, Brazil. Pre-planting applications resulted in a maximal AS-N immobilization 22 days after fertilizer application (9.1 kg ha-1 or 11.4 % of applied N), whereas the maximum immobilization of U-N occurred 11 days after fertilizer application (46.5 kg ha-1 or 58.1 % of applied N). Until harvest, the plants (aerial part, grains and roots) had accumulated 66.0 and 47.9 of AS-N and U-N, respectively (use efficiency of 82.5 and 59.9 % of applied N). N top-dressing resulted in 12.5 % less N immobilized applied as both sources in all growth stages, evidencing that the soil biomass did not compete with the plants for N-fertilizer, in agreement with results of the growing season 1999/2000. In both growing seasons (1999/2000 and 2000/2001) corn plants assimilated an average 8.9 and 15.4 kg ha-1 of AS-N for each kg of immobilized N-fertilizer from pre-planting and top-dressing, respectively, in the stage of 11-12 leaves and at flowering. For U-N these values were 4.5 and 5.2 kg ha-1, respectively, presenting a lower ratio of immobilized AS-N in top-dressing. Highest corn yields were obtained in the AS treatments (mean grain yield of 8.543 kg ha-1) independent of the application time. Urea treated plants obtained average grain yields of 7.767 kg ha-1 for both application periods. These results show that for pre-planting fertilizers the immobilization-mineralization N turnover was faster in the AS than in the U-N treatment. Consequently, N assimilation by corn plants was higher in the AS treatments. Only U-N was significantly immobilized more also in the second growing season when top-dressed, thus limiting plant N uptake.

Nitrogen-15 labeling of Crotalaria juncea green manure

A grande maioria dos estudos com a utilizacao de material vegetal marcado com o isotopo 15N nao apresentam detalhes tao importantes sobre como foram obtidos esses materiais. Em se tratando de marcacao de leguminosas as dificuldades em se obter material marcado com 15N sao ainda maiores pelo fato de serem plantas fixadoras de nitrogenio. Isso posto foi estabelecida uma tecnica de marcacao de leguminosas com nitrogenio (15N), com o objetivo de obter material vegetal marcado isotopicamente para estudos de dinâmica do nitrogenio. Cultivou-se a leguminosa crotalaria juncea (Crotalaria juncea L.), em Argissolo Vermelho Amarelo distrofico, em campo. Ao se aplicarem via foliar 58,32 gramas de ureia em oito canteiros experimentais, (ureia com 70,57 ± 0,04% de atomos de 15N) parceladas em tres vezes, obteve-se material vegetal marcado seco que continha 2,412 % em atomos de 15N em uma massa seca equivalente a 9 Mg ha-1. Essa marcacao permite o uso dessa massa vegetal em estudos de dinâmica de nitrogenio.

Stable sulfur isotope fractionation by anion exchange chromatography: production of compounds enriched in 34S

The separation of the 34S isotope was carried out by isotopic exchange between sulfurous acid in solution and bisulfite anions adsorbed on a quaternary ammonium (Dowex 1X8 and Dowex 2X8, 100-200 mesh) packed in six anion exchange columns. Each resin column packed with the anion exchange resin had a height of 115 cm and 2.2 cm in diameter. The columns were connected in series during the displacement of bisulfite bands. For the experiments, a band of bisulfite was fixed to the anion resin, initially in the hydroxyl ion form, and subsequently eluted with 0.2, 0.3, 0.4, or 0.6 mol L-1 HCl solution. The hydrochloric acid solution was kept under nitrogen at 245 kPa, in order to prevent the evolution of gases and the oxidation of the bisulfite band. The experiments with the Dowex 1X8 resin showed that the best results in terms of maximum enrichment (18.66 atom % 34S) and total 34S accumulated mass (161.7 mg, excess) were obtained by elution of the bisulfite band for 50 m with 0.2 and 0.3 mol L-1 HCl, respectively. The depleted portion of the band was periodically replaced with natural bisulfite, at 10 m intervals during elution.

Gerenciamento de resíduos químicos e águas servidas no laboratório de isótopos estáveis do CENA/USP

A system for disposal and recovery of the main effluents and chemical waist from isotope separation plants and enriched compounds-15N and 34S production has been carried out at the Stable Isotope Laboratory (LIE) of the CENA/USP. Around four hundred thousand liters of effluents has been recovered yearly. Among the recovered chemical wastes, the more relevant are: ammonia; brome; ammonium and sodium sulfate; sodium hydroxide; sulfur dioxide; and hydrochloric acid. Chemical wastes containg recoverable heavy metals (Ag, Cr and Cu) and solvents (methanol, ethanol and acetone) are processed and recovered. Gaseous emissions, mainly H2S are used for recovery of heavy metals solutions. The minimization of the residues waters, as well the reduction of electric energy consume was established using a water deionization system. A cost/effect balance of the process is reported.

Sulfur utilization by rice and Crotalaria juncea from sulfate - 34S applied to the soil

In tropical soils with intensive agriculture an increasing sulfur deficiency has been verified in several crops. The low available S in these soils is caused by the continuous use of concentrated NPK fertilizers. The objective of this work was to evaluate the utilization by rice (Oriza sativa L.) and crotalaria juncea (Crotalaria juncea L.) of sulfur applied to the soil, under greenhouse conditions. Pots with 3 kg of an Argisol (Paleudalf) were used to test the isotopic technique with the stable isotope 34S, adding a solution of sodium sulfate labeled with 34S (14.30 ± 0.05 atom % of 34S) to the soil (70 mg SO4-S per kg-1 of soil) 18 days after sowing both species. The shoots of the crotalaria and rice were harvested, respectively on the 72nd and 122nd days after S fertilization. The concentration and the amount of sulfur in the crotalaria were higher than in rice, due to the higher legume requirement for this nutrient. The sulfur requirement and the short time interval between fertilization and harvest of the crotalaria resulted in a small amount of native SO4-S mineralized in the soil and a small quantity of 34SO4 immobilized by soil microorganisms. Thus, the percentage of sulfur in the crotalaria derived from the fertilizer (Sdff) was higher than in the rice (%Sdffcrotalaria = 91.3 ± 3.5%; %Sdffrice = 66.3 ± 0.8%). The expressive values of %Sdff indicate a low rate of mineralization of SO4-S probably as a consequence of the low available sulfur content in the soil.

Last millennium environmental changes and climate inferences in the Southeastern Atlantic forest, Brazil

This study presents paleoenvironmental data based on pollen, elemental and isotopic compositions of organic matter (TOC, N, δ(13)C and δ(15)N) and (14)C dating of 170 cm lake sediment record. Samplings have been made in Lagoa Grande at Parque Estadual Turístico do Alto Ribeira - PETAR, Southern São Paulo State, Southeastern Brazil. The variations in relative frequencies (in percentage) of arboreal pollen along the core range between 40 and 80%. The δ(13)C values ranged from -23% to -30% and C/N of ~10 to 15, indicating the contribution of terrestrial C(3) plants and algae in the sediment organic matter. The δ(15)N results presented values from 3 to 4.5%, also suggesting a mixture of algae and terrestrial C(3) plants. The (14)C dating indicates modern age for the shallow horizons to ~1030 BP at the base of the core. A probable wetter climate in the period of ~370 BP to ~340 BP was inferred from the data set, which corresponds to a part of the period covered by the Little Ice Age (LIA).

Production of single superphosphate labeled with 34S

Single superphosphate is currently one of the mostly used fertilizers as an alternative source for phosphorus and sulphur. Sulphur presents four stable isotopes (32S, 33S, 34S, and 36S) with natural abundances of 95.00; 0.76; 4.22; and 0.014% in atoms, respectively. Single superphosphate labeled with the 34S isotope was obtained from a chemical reaction in stoichiometric amounts between Ca(H2PO4)2 and Ca34SO4.2H2O. Calcium sulphate (Ca34SO4.2H2O) was enriched with 5.85 ± 0.01 atoms % of 34S. The Ca(H2PO4)2 reagent was obtained from a reaction between CaCl2.2H2O and H3PO4. The reaction between the Ca(H2PO4)2 thus produced and the labeled Ca34SO4.2H2O compound was then performed to obtain the 34S-labeled single surperphosphate. The thermal decomposition of the labeled superphosphate for the production of gaseous 34SO2 was carried out under a vacuum line at 900oC in the presence of NaPO3. The isotopic determination of S (atoms % of 34S) was carried out on an ATLAS-MAT model CH-4 mass spectrometer. The production yield of Ca(H2PO4)2 and labeled single superphosphate were approximately 97 and 99% respectively, and the purity level of the labeled single superphosphate was estimated as 96%. No isotopic fractionation was observed in the production process of 34S-labeled single superphosphate.