Absorption and fluorescence properties of chromophoric dissolved organic matter of the eastern Bering Sea in the summer with special reference to the influence of a cold pool

The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a cold pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (<i>a</i>_g355) and its spectral slope (<i>S</i>) in conjunction with excitation–emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components one, two and five) and two protein-like (a tyrosine-like component three, and a tryptophan-like component four) components. In the extensive shelf region, average absorption coefficients at 355 nm (<i>a</i>_g355, m⁻¹) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m⁻¹, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m⁻¹, 78.38 ± 10.64 μM) and outer (0.185 ± 0.05 m⁻¹, 79.24 ± 18.01 μM) shelves, respectively. DOC concentrations, however were not significantly different, suggesting CDOM sources and sinks to be uncoupled from DOC. Mean spectral slopes <i>S</i> were elevated in the middle shelf (24.38 ± 2.25 μm⁻¹) especially in the surface waters (26.87 ± 2.39 μm⁻¹) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components one, two, and five were most elevated in the inner shelf most likely from riverine inputs. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and <i>a</i>_g355 (mean 66.99 ± 7.94 μM; 0.182 ± 0.05 m⁻¹) and a high <i>S</i> (mean 25.95 ± 1.58 μm⁻¹) suggested substantial photobleaching of the Alaska Coastal Water, but high intensities of humic-like and protein-like fluorescence suggested sources of fluorescent DOM from coastal runoff and glacier meltwaters during the summer. The spectral slope <i>S</i> vs. <i>a</i>_g355 relationship revealed terrestrial and oceanic end members along with intermediate water masses that were modeled using nonlinear regression equations that could allow water mass differentiation based on CDOM optical properties. Spectral slope <i>S</i> was negatively correlated (<i>r</i>² = 0.79) with apparent oxygen utilization (AOU) for waters extending from the middle shelf into the deep Bering Sea indicating increasing microbial alteration of CDOM with depth. Although our data show that the CDOM photochemical environment of the Bering Sea is complex, our current information on its optical properties will aid in better understanding of the biogeochemical role of CDOM in carbon budgets in relation to the annual sea ice and phytoplankton dynamics, and to improved algorithms of ocean color remote sensing for this region

Fragmento de floresta de transição na zona urbana do Município de Macapá: propostas de estudos e aproveitamento.

bitstream/item/81067/1/AP-2012-Fragmento-floresta-documentos-75.pd

The Seismic Signature of Upper-Mantle Plumes: Application to the Northern East African Rift

Several seismic and numerical studies proposed that below, some hotspots upper-mantle plumelets rise from a thermal boundary layer below 660 km depth, fed by a deeper plume source.We recently found tomographic evidence of multiple upper-mantle upwellings, spaced by several 100 km, rising through the transition zone below the northern East African Rift. To better test this interpretation, we run 3-D numerical simulations of mantle convection for Newtonian and non-Newtonian rheologies, for both thermal instabilities rising from a lower boundary layer, and the destabilization of a thermal anomaly placed at the base of the box (700–800 km depth). The thermal structures are converted to seismic velocities using a thermodynamic approach. Resolution tests are then conducted for the same P and S data distribution and inversion parameters as our traveltime tomography. The Rayleigh Taylor models predict simultaneous plumelets in different stages of evolution rising from a hot layer located below the transition zone, resulting in seismic structure that looks more complex than the simple vertical cylinders that are often anticipated. From the wide selection of models tested, we find that the destabilization of a 200 ◦C, 100 km thick thermal anomaly with a non-Newtonian rheology, most closely matches the magnitude and the spatial and temporal distribution of the anomalies below the rift. Finally, we find that for reasonable upper-mantle viscosities, the synthetic plume structures are similar in scale and shape to the actual low-velocity anomalies, providing further support for the existence of upper-mantle plumelets below the northern East African Rift

Seleção de linhagens de feijão-caupi para o cerrado do Amapá.

O cerrado do Amapá possui amplas características para a produção de alimentos, sendo o feijão-caupi uma grande opção. Assim, selecionar cultivares para utilização no processo mecanizado deve ser uma meta a ser seguida, sendo este o objetivo do experimento

Genótipos prostrados de feijão-caupi no Cerrado do Amapá.

O cerrado do Estado do Amapá apresenta totais condições para a produção de grãos, sendo o feijão-caupi uma das opções mais viáveis. Assim, selecionar cultivares para este ambiente deve ser uma das metas da pesquisa. No caso em estudo, o experimento objetivou avaliar linhagens de porte prostrado e semi-prostrado. Em Latossolo Amarelo, clima do tipo Ami, usou-se o delineamento experimental de blocos ao acaso e quatro repetições, adubação de 80 kg ha-1 (superfosfato triplo) e 50 kg ha-1 (cloreto de potássio). A semeadura manual ocorreu em fileiras espaçadas de 0,80 m, com área útil de 8 m2 e população de 100 mil plantas ha-1. A análise de variância mostrou diferença significativa pelo teste de Tukey (p< 0,05). O melhor desempenho produtivo de 1.216,7 kg ha-1 foi da linhagem MNC02-676F-1, que apresenta grão da subclasse mulato, seguida pela cultivar BRS-Pajeú com 1.119,0 kg ha-1, com grão da subclasse sempre verde. A linhagem BRS Juruá alcançou menor período de floração, enquanto o maior comprimento de vagem foi do genótipo MNC02-677F-2. Todas as linhagens mostraram tolerância à incidência de doenças.Disponível em: http://www.conac2012.org/resumos/pdf/133c.pdf. Acesso em: 22 jul. 2013

Determinação de adubação N-P-K em tomateiros no Amapá.

Cerca de 95% do tomate comercializado em Macapá e proveniente de importações de outras unidades da federação. Apesar da pesquisa agropecuária dispor de recomendação de genotipos adaptados as condições edafoclimaticas do estado, entraves de ordem tecnologica tem dificultado a expansão da tomaticultura no Amapá.bitstream/item/97860/1/CPAF-AP-1998-Determinacao-adubacao.pd

Determinação de níveis economicos de NPK na cultura da alface em Macapá.

A produção de alface no Amapá e insuficiente para atender a demanda local, aliado a esse fato, o abastecimento através de outros centros produtores e dificultado pela perecibilidade do produto e pelo isolamento geografico do estado. Com essa preocupação, diversos genotipos de alface foram avaliados, ja possuindo-se no momento, resultados para sua recomendação aos agricultores.bitstream/item/74279/1/AP-1998-niveis-economicos-npk.pd

Seismic tomographic imaging of the Eastern Mediterranean Mantle: Implications for terminal-stage subduction, the uplift of Anatolia, and the development of the North Anatolian Fault

The Eastern Mediterranean captures the eastwest transition from active subduction of Earth'soldest oceanic lithosphere to continental collision, making it an ideal location to study terminalstagesubduction. Asthenospheric or subductionrelated processes are the main candidates for the region's ∼2kmuplift and Miocene volcanism; however, their relative importance is debated. To address these issues, wepresent new P and S wave relative arrivaltime tomographic models that reveal fast anomalies associatedwith an intact Aegean slab in the west, progressing to a fragmented, partially continental, Cyprean slabbelow central Anatolia. We resolve a gap between the Aegean and Cyprean slabs, and a horizontal tear in theCyprean slab below the Central Anatolian Volcanic Province. Below eastern Anatolia, the completelydetached “Bitlis” slab is characterized by fast wave speeds at ∼500 km depth. Assuming slab sinkingrates mirror ArabiaAnatolia convergence rates, the Bitlis slab's location indicates an Oligocene (∼26 Ma)breakoff. Results further reveal a strong velocity contrast across the North Anatolian Fault likelyrepresenting a 40–60 km decrease in lithospheric thickness from the Precambrian lithosphere north of thefault to a thinned Anatolian lithosphere in the south. Slow uppermostmantle wave speeds below activevolcanoes in eastern Anatolia, and ratios of P to S wave relative traveltimes, indicate a thin lithosphere andmelt contributions. Positive central and eastern Anatolian residual topography requires additional supportfrom hot/buoyant asthenosphere to maintain the 1–2 km elevation in addition to an almost absentlithospheric mantle. Smallscale fast velocity structures in the shallow mantle above the Bitlis slab maytherefore be drips of Anatolian lithospheric mantle

Interaction of subducted slabs with the mantle transition-zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate

Transition zone slab deformation influences Earth's thermal, chemical, and tectonic evolution. However, the mechanisms responsible for the wide range of imaged slab morphologies remain debated. Here we use 2-D thermo-mechanical models with a mobile trench, an overriding plate, a temperature and stress-dependent rheology, and a 10, 30, or 100-fold increase in lower mantle viscosity, to investigate the effect of initial subducting and overriding-plate ages on slab-transition zone interaction. Four subduction styles emerge: (i) a "vertical folding" mode, with a quasi-stationary trench, near-vertical subduction, and buckling/folding at depth (VF); (ii) slabs that induce mild trench retreat, which are flattened/"horizontally deflected" and stagnate at the upper-lower mantle interface (HD); (iii) inclined slabs, which result from rapid sinking and strong trench retreat (ISR); (iv) a two-stage mode, displaying backward-bent and subsequently inclined slabs, with late trench retreat (BIR). Transitions from regime (i) to (iii) occur with increasing subducting plate age (i.e., buoyancy and strength). Regime (iv) develops for old (strong) subducting and overriding plates. We find that the interplay between trench motion and slab deformation at depth dictates the subduction style, both being controlled by slab strength, which is consistent with predictions from previous compositional subduction models. However, due to feedbacks between deformation, sinking rate, temperature, and slab strength, the subducting plate buoyancy, overriding plate strength, and upper-lower mantle viscosity jump are also important controls in thermo-mechanical subduction. For intermediate upper-lower mantle viscosity jumps (×30), our regimes reproduce the diverse range of seismically imaged slab morphologies