Reduction of mercury(II) by tropical river humic substances (Rio Negro) - A possible process of the mercury cycle in Brazil

The evolution of elemental Hg from its environmental compounds has already been supposed to be an important process within the global mercury cycle. The present study characterizes the abiotic reduction of Hg(II) ions by typical river humic substances (HS) conventionally pre-isolated by the adsorbent XAD 8 from the Rio Negro near Manaus, Brazil. For the investigation of this reduction process a special reaction and Hg(0) trapping unit combined with cold-vapor atomic absorption spectrometry (CVAAS) was developed. Preconcentration of traces of mercury(II), if required, was obtained by a home-made FIA system using microcolumns filled with the Hg(II)-selective collector CheliteS(R) (Serva Company). The effect of environmentally relevant parameters such as the pH value, the Hg(II)/HS ratio and the HS concentration on the I-IE;(II) reduction process was studied as a function of the time. The Hg(0) production was highest at pH 8.0 and in the case of decreasing HS amounts (0.5 mg) when about 65% of initially 1.0 mug Hg(H) was reduced within 50 h. Moreover, the reduction efficiency of HS towards HE;(II) strongly depended on the HS concentration but hardly on the Hg(II)/HS ratio. The reduction kinetics followed a relatively slow two-step first-order mechanism with formal rate constants of about 0.1 and 0.02 h(-1), respectively. Based on these findings the possible relevance of the abiotic evolution of mercury in humic-rich aquatic environments is considered. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Interaction of mercury(II) with humic substances from the Rio Negro (Amazonas State, Brazil) by means of an ion exchange procedure

The aquatic humic substances (HS) investigated in this study with respect to their binding capability towards mercury(II) were isolated from the river Rio Negro, Amazonas State - Brazil, by means of the adsorbent XAD 8. Labile/inert fractions of inorganic Hg(II) complexes formed with these HS were characterized using an ion-exchange batch and column technique, respectively, based on Chelite S. This collector exhibits high Hg(II) distribution coefficients, Kd, up to the order of 104 decreasing, however, in the case of small Hg(II)/HS ratios (< 0.1 μg Hg(II) / mg HS). The influence of different complexation parameters (ratio of Hg(II)/HS, pH, contact time, complexing time) relevant for Hg(II) binding in aquatic environments was assessed. The Hg(II) lability in dissolved HS is mainly influenced by the mass ratio of Hg(II)/HS and the ageing of Hg(II)-HS species formed. This is particularly obvious in the case of low Hg(II) loading of HS where slow transformation processes of freshly formed Hg(II)-HS species significantly decrease their lability, leading to incomplete recoveries (< 20%) of the total Hg(II) bound to HS.

Conhecimento popular sobre plantas medicinais em comunidades rurais de mata atlântica - Itacaré, BA, Brasil

This study's goal was to caryy out an ethnobotanical survey focusing on the knowledge and use of medicinal plants within two rural communities (Marambaia and Camboinha), which are situated in an Environmental Protection Area in Atlantic Forest of Southern Bahia, Brazil. These communities use medicinal plants as an important therapeutic activity, which permits the rural inhabitants to be self-sufficient regarding health care. Data were collected through interviews with 26 families (24% of the total). The medicinal plants collected (98 species) were catalogued, identified and deposited at the Herbarium Rio Clarense (HRCB). They belong to 40 families so that Lamiaceae was the most cited. The majority of these species (78%) are cultivated, usually in backyards by local inhabitants. The leaf is the most common part of the plant used in medicinal preparations. The species with the greatest number of citations were Chenopodium ambrosioides L. and Lippia alba (Mill) N.E. Br. These species are also associated with the highest number of therapeutic uses. Use agreement and diversity index from this survey were compared to other surveys conducted in Brazilian Tropical Forests.

Avaliação de genótipos de soja em semeadura de inverno, em Selvíria, MS: Produção e qualidade fisiológica de sementes

The sowing of soybean out of the conventional period is an option for the production of seeds with high physiological quality. On the other hand, this fact makes necessary the search for cultivars adapted to new environmental conditions. Therefore, additional research is needed to supply more information to producers related to the choice of the most suited cultivars with regard to high seed quality. This research was conducted in Selvíria, MS, Brazil in which the cultivars FT-2000, FT-Inaê, Embrapa 20 (Doko RC), CAC-1, IAC-17, IAC-18, IAC-19, IAC-8-2, FT-101, FT-109, MT/ BR 45 (Paiaguás), MT/BR 50 (Parecis), MT/BR 52 (Curió), MT/BR 53 (Tucano), MT/BR 47 (Canário), MT/BR 49 (Pioneira), BRSMT Uirapuru, BR Emgopa 314 (Garça Branca), MG/BR 46 (Conquista), FT-Estrela, FT-Cometa, Dourados, JAB-11, BR 9 (Savana), FT-Abyara, Embrapa 30 (Vale do Rio Doce), Embrapa 9 (Bays), Embrapa 31 (Mina), IAC-16; IAS 5, EMGOPA-304, and IAC-Foscarin 31 were studied. These cultivars were sown on June 5, 1998, and evaluated both for agronomic characteristics and the physiological potential of the seeds. The experimental units were arranged in the field according to a randomized complete block design with five replicates. The cultivars more adapted to the climatic conditions were Parecis, Bays, CAC-1, Garça Branca, Paiaguás, Pioneira, and IAC-16. It was concluded that winter sowing should start at the beginning of May, with water supply, since June was found to be too late.

Toxicidade de águas e sedimentos em um rio afetado por atividades mineradoras pretéritas

The Ribeira de Iguape River basin received intense mining activities for lead exploiting and, as a result, the river received the discharges of estimated amounts of 5.5 tons/month of material rich in As, Ba, Cd, Pb, Cu, Cr and Zn. In this article, the toxicity of waters and sediments collected in Ribeira de Iguape River was assessed aiming to estimate environmental quality. Three sampling campaigns were conducted, from 2009 to 2010. Toxicity tests with the cladoceran Daphnia similis were done for water samples and for sediments, in this case using sediment-water interface exposure. Results showed in general absence of toxicity for sediments and waters, and only eventually were acute effects registered (marginal toxicity). Results are consistent with the conditions indicated by the literature, of low concentrations of metals in waters and sediments; however they differ from the monitoring made by the state environmental agency, which registered chronic toxicity. The occurrence of eventual acute toxicity indicates that although Ribeira de Iguape River quality is being restored, conditions still are not totally under control.

Teores de iodo em dietas secas e úmidas para gatos adultos comercializadas na cidade do Rio de Janeiro, Brasil

Were analyzed 29 samples, 16 wet and 13 dry cat food of different flavors. The iodine levels ranged from 2.7 to 3.4 (average 2.95 mg/kg/MS) in dry food and 2.9 to 4.0 (average 3.4 mg/kg/MS) in the wet food. Eight samples (27.6%) specified on the package the assurance level (maximum) of iodine, with a dry (2.0 mg/kg/diet) and seven wet (0.04 mg/kg/diet). All non-compliant, because the values were higher than declared. Cats fed commercial diets consume proportionally more iodine in wet food than cats fed dry diets, but both with high levels of iodine. All samples analyzed were above the amounts stated on the labels. Accordingly, the wet and dry commercial food for cats show no reliable values with those reported, resulting in a possible excessive intake of this trace element for animals in question.

Ictiofauna nos trechos médio e baixo rio Pardo, Alto Paraná: inventário

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vale de ferro: estudo histórico e estético das estações ferroviárias do Vale do Paraíba Paulista

Pós-graduação em Artes - IA

Revisitação de Bromeliaceae na APA Santuário ecológico da Pedra Branca Caldas, MG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Florística e fitossociologia das espécies arbóreas de ocorrência e mata ciliar no Alto Rio Pardo, na estância climática de Caconde - SP

Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC

Delimitação de unidades ambientais na bacia do Rio Capivara, Botucatu (SP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Eritrograma e morfometria eritrocitária de avestruzes (struthio camelus) criados na região de São José do Rio Preto, São Paulo, Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização geológico-geotécnica aplicada à instalação de postos de combustíveis em Rio Claro (SP)

Pós-graduação em Geociências e Meio Ambiente - IGCE

Carta geológico-geotécnica como subsídio a elaboração de cartas de sensibilidade ambiental, a derrames de petróleo e derivados, na região do oleoduto Guararema-São José dos Campos, Vale do Paraíba (SP)

Pós-graduação em Geociências e Meio Ambiente - IGCE

Geoarqueologia e paleoidrologia da planicie aluvial holocênica do alto Rio Madeira entre Porto Velho e Abunã - RO

Pós-graduação em Geociências e Meio Ambiente - IGCE