DISTRIBUIÇÃO E FRACIONAMENTO DO Hg EM SEDIMENTOS DO RIO PARAÍBA DO SUL – RJ, BRASIL

Mercury distribution and fractionation were determined in sediments from the Paraíba do Sul River – RJ, Brazil. Total mercury concentration ranged from 1 to 158 ng g-1. Hg associated with the weakly bound fraction was dominant in the estuarine areas (main - 60% and secondary - 55%); followed by fluvial end member (48%) and mangrove (18%). These results reinforce the mercury availability to fluvial and estuarine areas and emphasize the key role played by mangroves as an efficient biogeochemical barrier. In conclusion, the continuous reduction of the mangrove ecosystem around the world can exacerbate the damage resulting from the mercury accumulation.

ARSÊNIO E ARROZ: TOXICIDADE, METABOLISMO E SEGURANÇA ALIMENTAR

Arsenic is considered a semimetal, and its wide distribution in the Earth's crust in different chemical forms, including organic and inorganic species, has a great deal of influence on the mechanisms of toxicity. Exposure to arsenic can be either through occupational practice (use of pesticides) or by the consumption of water and food containing the element. Rice is considered a fundamental constituent of the basic diet of Brazilians and is usually cultivated in flooded conditions. Such a plantation system results in an increased amount of As in the soil and hence a greater accumulation of As in the plant, which is highlighted by the inorganic species' classification as highly toxic. Besides the use of mitigation techniques to reduce the toxicological risk, monitoring the concentration of As and its chemical species in rice and rice products is required through the establishment of legislation in the area. Thus, some world organizations are conducting improved research to determine and establish acceptable concentrations of As and its chemical species in rice, e. g., in 2012, FDA researchers described a chemical speciation methodology for As in rice and rice products. Hence, the application of existing chemical speciation methods and the establishment of parameters for ensuring food security and exposure risk assessment deserve particular consideration.

Physiological and biochemical characterization of the assai palm (Euterpe oleracea Mart.) during seed germination and seedling growth under aerobic and anaerobic conditions

Physiological and biochemical aspects of assai palm during seed germination and early seedling growth were investigated. Seeds collected from plants growing in flooded and upland forests were used to determine the influence of normoxic (aerobic) and anoxic (anaerobic) conditions in germination and the initial and average time of development in the roots and shoots. After 75 days, seedlings germinated under normoxia were transferred to trays and submitted to flooding. Seed reserves (lipids, proteins, soluble sugars and starch) were monitored for quiescent and germinated seeds maintained under normoxic and anoxic conditions, as well as after 5, 10 and 20 days of seedling growth. Alcohol dehydrogenase (ADH) activity was quantified in roots and leaves of seedlings without or with flooding (partial and total). Seeds were not able to germinate under anoxia. Different strategies of storage mobilization of lipids, proteins, soluble sugars and starch were observed in seeds of each environment. ADH activity was induced by anoxia, with the highest level observed in the leaves. This study showed that, under normoxic conditions, the best developmental performance of assai palm seeds, from flooded or upland forest areas, during germination was associated with primary metabolites mobilization and seedling flooding tolerance with increased ADH activity. We conclude that the assai palm is well adapted to the anoxic conditions provoked by flooding.

GAS EXCHANGE IN YOUNG PLANTS OF Tabebuia aurea(Bignoniaceae Juss.) SUBJECTED TO FLOODING STRESS1

ABSTRACT The Paratudo (Tabebuia aurea) is a species occurring in the Pantanal of Miranda, Mato Grosso do Sul, Brazil, an area characterized by seasonal flooding. To evaluate the tolerance of this plant to flooding, plants aged four months were grown in flooded soil and in non-flooded soil (control group). Stomatal conductance, transpiration and CO2 assimilation were measured during the stress (48 days) and recovery (11 days) period, totalling 59 days. The values of stomatal conductance of the control group and stressed plants at the beginning of the flooded were 0.33 mol m-2s-1 and reached 0.02 mol m-2 s-1 (46th day) at the end of this event. For the transpiration parameter, the initial rate was 3.1 mol m s-1, and the final rate reached 0.2 or 0.3 mol m-2 s-1 (47/48 th day). The initial photosynthesis rate was 8.9 mmol m-2s-1 and oscillated after the sixth day, and the rate reached zero on the 48th day. When the photosynthesis rate reached zero, the potted plants were dried, and the rate was analyzed (11th day). The following values were obtained for dried plants: stomatal conductance = 0.26 mol m-2 s-1, transpiration rate = 2.5 mol m-2 s-1 and photosynthesis rate = 7.8 mmol m-2 s-1. Flooded soil reduced photosynthesis and stomatal conductance, leading to the hypertrophy of the lenticels. These parameters recovered and after this period, and plants exhibited tolerance to flooding stress by reducing their physiological activities.

Anthrax in cattle in southern Brazil: 1978-2006

Ten outbreaks of anthrax occurred in cattle from 1978 to 2006 in southern Brazil, in 5 municipalities on the border with Uruguay, a country where the disease is frequent. The 10 outbreaks represented 0.2% of all bovine specimens received during the period by the Regional Diagnostic Laboratory of the Federal University of Pelotas, causing 267 deaths in a risk population of 6,605 head. The disease affected young and adult cattle mainly during summer. Only one farmer reported that sheep and horses were also affected. Clinically the peracute form was more frequent, but in some outbreaks the acute form with a clinical manifestation period of 6-48 hours was also observed. The source of infection was not established; but the reduced rainfall, associated with low, flat, flooded lands used for agriculture followed by animal grazing after harvest was probably related to the disease occurrence. Annual vaccination is an efficient way to prevent the disease.

Competition periods of crabgrass with rice and soybean crops

Determining the periods of weed competition with crops helps the producer to choose the most appropriate time to use weed control practices. This strategy allows for the reduction of the number of herbicide applications, reducing costs and the environmental impact of pesticides. The objectives were to determine the period before the interference (PBI) of crabgrass (Digitaria ciliaris) competing with flooded rice, the critical period of interference prevention (CPIP) of crabgrass with soybean and the effects of competition on the grains yield and their components. Experiments were conducted with the coexistence of BRS Querência rice cultivar with crabgrass, for periods of 0, 7, 14, 21, 28, 35, and 110 days after emergency (DAE) and Fundacep 53RR soybean cultivar, whose periods of coexistence and control of crabgrass were 0, 7, 14, 21, 28, 35, and 156 DAE. Rice can grow with crabgrass infestation until 18 DAE, while soybean should remain free from the presence of crabgrass in the period between 23 and 50 DAE. The grain yield and its components, in the crops studied, are affected when grown with crabgrass.

Temporal and spatial variations in the structure of macroalgal communities associated with mangrove trees of Ilha do Cardoso, São Paulo state, Brazil

Temporal and spatial variations in species composition and vertical distribution of macroalgal communities growing on mangrove trees were analyzed bimonthly in the Ilha do Cardoso State Park, São Paulo state (25°03'S and 47°55'W), Southeastern Brazil. The macroalgal communities from mangroves of Perequê and Sítio Grande rivers comprised 10 and 18 taxa respectively. Bostrychia radicans (Mont.) Mont. and B. calliptera (Mont.) Mont. were the predominant taxa, present almost throughout the year and in all the sites studied. The species composition of macroalgal communities from both mangroves presented temporal and spatial variations related to environmental factors. The highest number of taxa was observed during colder, drier months, coinciding with the highest means of high water neap and short periods of continuous emersion (April to August). Some mangrove algae such as B. calliptera, Rhizoclonium spp., Caloglossa spp., and Boodleopsis pusilla (Collins) W. Taylor, Joly et Bernatowicz showed a high degree of tolerance to desiccation, being able to tolerate continuous emersion up to six days. The spatial variations in species composition were related to light, as observed in Catenella caespitosa (Withering) L. Irvine, which occurred in well-lit sites. No pattern of vertical zonation was observed, since Rhizoclonium spp., B. radicans, and B. calliptera occur over the entire vertical range. Variations in the range of vertical distribution of macroalgae of Perequê mangrove were mainly related to the variations in the tidal levels (mean high water neap and/or mean high water spring) while those observed in Sítio Grande mangrove were related to salinity variations, except for B. calliptera and Caloglossa spp. related to tidal levels and high irradiance, respectively.

Flooding effects in seedlings of Cytharexyllum myrianthum Cham. and Genipa americana L.: responses of two neotropical lowland tree species

Six-month-old seedlings of Cytharexyllum myrianthum and Genipa americana, two common tree species in different flood-prone areas in Brazil, were flooded for up to 90 days to compare their survival and growth responses under these conditions. Seedlings of both species were found to be relatively tolerant to flooding but growth responses changed according to treatment and plant species. Growth of G. americana was reduced by flooding, showing a decrease in root and leaf dry mass, root/shoot ratio and height, without showing any adaptive morphological changes. On the other hand, growth of C. myrianthum seedlings was stimulated under flooding conditions, showing an increase in root dry mass, root/shoot ratio, height, stem diameter and some morphological changes in roots and stems, i.e., development of new roots and stem base hypertrophy. These results could be regarded as an experimental corroboration of the field observations, showing that these species could be indicated for restoration programs of some Neotropical wetlands.

Tree population and community dynamics in a Brazilian tropical semideciduous forest

The dynamics of the tree community and 30 tree populations were examined in an area of tropical semideciduous forest located on the margin of the Rio Grande, SE Brazil, based on surveys done in 1990 and 1997 in three 0.18 ha plots. The main purpose was to assess whether variations in dynamics were related to topography and the effects of a catastrophic flood in 1992. Rates of mortality and recruitment of trees and gain and loss of basal area in two topographic sites, lower (flooded) and upper (non-flooded), were obtained. Projected trajectories of mean and accelerated growth in diameter were obtained for each species. In both topographic sites, mortality rates surpassed recruitment rates, gain rates of basal area surpassed loss rates, and size distributions changed, with declining proportions of smaller trees. These overall changes were possibly related to increased underground water supply after the 1992 flood as well as to a c. 250-year-old process of primary succession on abandoned gold mines. Possible effects of the 1992 flood showed up in the higher proportions of dead trees in the flooded sites and faster growth rates in the flood-free sites. Species of different regeneration guilds showed particular trends with respect to their demographic changes and diameter growth patterns. Nevertheless, patterns of population dynamics differed between topographic sites for only two species.

Coolability of porous core debris beds : Effects of bed geometry and multi-dimensional flooding

This thesis addresses the coolability of porous debris beds in the context of severe accident management of nuclear power reactors. In a hypothetical severe accident at a Nordic-type boiling water reactor, the lower drywell of the containment is flooded, for the purpose of cooling the core melt discharged from the reactor pressure vessel in a water pool. The melt is fragmented and solidified in the pool, ultimately forming a porous debris bed that generates decay heat. The properties of the bed determine the limiting value for the heat flux that can be removed from the debris to the surrounding water without the risk of re-melting. The coolability of porous debris beds has been investigated experimentally by measuring the dryout power in electrically heated test beds that have different geometries. The geometries represent the debris bed shapes that may form in an accident scenario. The focus is especially on heap-like, realistic geometries which facilitate the multi-dimensional infiltration (flooding) of coolant into the bed. Spherical and irregular particles have been used to simulate the debris. The experiments have been modeled using 2D and 3D simulation codes applicable to fluid flow and heat transfer in porous media. Based on the experimental and simulation results, an interpretation of the dryout behavior in complex debris bed geometries is presented, and the validity of the codes and models for dryout predictions is evaluated. According to the experimental and simulation results, the coolability of the debris bed depends on both the flooding mode and the height of the bed. In the experiments, it was found that multi-dimensional flooding increases the dryout heat flux and coolability in a heap-shaped debris bed by 47–58% compared to the dryout heat flux of a classical, top-flooded bed of the same height. However, heap-like beds are higher than flat, top-flooded beds, which results in the formation of larger steam flux at the top of the bed. This counteracts the effect of the multi-dimensional flooding. Based on the measured dryout heat fluxes, the maximum height of a heap-like bed can only be about 1.5 times the height of a top-flooded, cylindrical bed in order to preserve the direct benefit from the multi-dimensional flooding. In addition, studies were conducted to evaluate the hydrodynamically representative effective particle diameter, which is applied in simulation models to describe debris beds that consist of irregular particles with considerable size variation. The results suggest that the effective diameter is small, closest to the mean diameter based on the number or length of particles.

Intervariability of Phosphorus Speciation in Selected Mangrove Ecosystems Around the Greater Cochin

Mangrove forests are best developed on tropical shorelines where there is an extensive intertidal zone, with an abundant supply of fine-grained sediment. It receives a mixture of liable and refractory organic and inorganic phosphorus compounds from the overlying water and the surrounding landmasses. Organic phosphorus is not available for mangrove plant nutrition. While inorganic phosphate represents the largest potential pool of plant-available and which are bound in the form of Ca, Fe and Al phosphate. It deals with the scientific investigations on mangrove systems in the Kerala coastline and to investigate nutrient distribution of mangrove ecosystems of greater Cochin area. It discusses the description of study areas such as Murikkumpadam-Vypeen Island and Aroor. Then it deals with the spatial and seasonal distribution of dissolved ammonia, nitrite, nitrate, inorganic phosphate, organic phosphate and the total phosphorus in surface waters of mangrove fringed creeks. Then it discusses the geochemical compositions of mangrove-fringed sediments and also the chemical speciation of phosphorus in sediment cores.

Studies on the Benthic Fauna of the Mangrove Swamps of Cochin Area

Division of Marine Biology, Micrbiology and Biochemistry,Cochin University of Science and Technology

Sulphur Chemistry in Mangrove Systems of Tropical Cochin Estuary

Sulphur is a non conservative major element and is the most active species in the redox processes in nature, especially in aquatic environment . The varying oxidative states from-2 to +6 make it possible to enter into many of the biogeochemical processes. Thus the history, present and future of the chemical composition and behaviour of the natural aquatic systems and sediments have footprints of the sulphur chemistry.Mangroves are considered to be the most productive, fishery supportive ecosystem operating in the intertidal regions. The interlinking of the mangroves with the sulphur chemistry is attempted here.

Characterisation and Distribution of Amino Acids in the Mangrove Sediments of Kochi

Mangrove swamps are unique inter-tidal wetland ecosystems found in sheltered tropical and subtropical shores.Mangrove sediments can be considered as large reservoirs of amino acids,which exist in several different forms,like free amino acids in the sediment micropores,as amino acids,peptides or proteins bound to clay minerals or as amino acids,peptides or proteins bound to humic colloids.Inorder to assess survival conditions of organisms of mangroves,it is important to understand stability of amino acids in the sediments.The amounts of amino acids present in sediment represent a balance between its synthesis and destruction by microorganisms.Thus amino acid analysis offers more insight into the processes of diagenesis,which changes the nature and characteristics of organic matter deposition and decomposition.

Hydrogeochemical evaluation of inorganics and bioorganics in selected aquatic environments

The present study is an investigation to address relevant chemical aspects of the three varied aquatic environments, such as mangroves, river and the estuary. The sampling locations include a thick mangrove forest with high tidal activity, a mangrove nursery with minimal disturbances and low tidal inundation, a highly polluted riverine system and an estuarine site, as reference. Nutrients and bioorganic compounds in the water column and surface sediment were estimated in an attempt to understand the regeneration properties of these different aquatic systems.Assessment of the trace metal pollution was also carried out.