Estimating return periods for daily precipitation extreme events over the Brazilian Amazon     

Eliane Barbosa Santos  Paulo Sérgio Lucio  Cláudio Moisés Santos e Silva 《Theoretical and Applied Climatology》2016,126(3-4):585-595

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Spatiotemporal variability of methane over the Amazon from satellite observations     

Igor Oliveira Ribeiro  Rodrigo Augusto Ferreira de Souza  Rita Valéria Andreoli  Mary Toshie Kayano  Patrícia dos Santos Costa 《大气科学进展》2016,33(7):852-864

The spatiotemporal variability of the greenhouse gas methane(CH_4) in the atmosphere over the Amazon is studied using data from the space-borne measurements of the Atmospheric Infrared Sounder on board NASA's AQUA satellite for the period 2003–12. The results show a pronounced variability of this gas over the Amazon Basin lowlands region, where wetland areas occur. CH_4 has a well-defined seasonal behavior, with a progressive increase of its concentration during the dry season, followed by a decrease during the wet season. Concerning this variability, the present study indicates the important role of ENSO in modulating the variability of CH_4 emissions over the northern Amazon, where this association seems to be mostly linked to changes in flooded areas in response to ENSO-related precipitation changes. In this region, a CH_4 decrease(increase) is due to the El Nino-related(La Ni ?na-related) dryness(wetness). On the other hand, an increase(decrease) in the biomass burning over the southeastern Amazon during very dry(wet) years explains the increase(decrease) in CH_4 emissions in this region. The present analysis identifies the two main areas of the Amazon, its northern and southeastern sectors, with remarkable interannual variations of CH_4. This result might be useful for future monitoring of the variations in the concentration of CH_4, the second-most important greenhouse gas, in this area.  相似文献   

Modelling the impacts of wildfires on runoff at the river basin ecological scale in a changing Mediterranean environment     

Mário G. Pereira  Luís Sanches Fernandes  Sérgio Carvalho  Regina B. Santos  Liliana Caramelo  Ana Alencoão 《Environmental Earth Sciences》2016,75(5):392

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Groundwater,Acid and Carbon Dioxide Dynamics Along a Coastal Wetland,Lake and Estuary Continuum     

Luke C. Jeffrey  Damien T. Maher  Isaac R. Santos  Ashly McMahon  Douglas R. Tait 《Estuaries and Coasts》2016,39(5):1325-1344

Coastal wetlands are hotspots for biodiversity and biological productivity, yet the hydrology and carbon cycling within these systems remains poorly understood due to their complex nature. By using a novel spatiotemporal approach, this study quantified groundwater discharge and the related inputs of acidity and CO₂ along a continuum of a modified coastal acid sulphate soil (CASS) wetland, a coastal lake and an estuary under highly contrasting hydrological conditions. To increase the resolution of spatiotemporal data and advance upon previous methodologies, we relied on automated observations from four simultaneous time-series stations to develop multiple radon mass balance models to estimate groundwater discharge and related groundwater inputs of acidity and dissolved inorganic carbon (DIC), along with surface water to atmosphere CO₂ fluxes. Spatial surveys indicated distinct acid hotspots with minimum surface water pH of 2.91 (dry conditions) and 2.67 (flood conditions) near a non-remediated (drained) CASS area. Under flood conditions, groundwater discharge accounted for ～14.5 % of surface water entering the lake. During the same period, acid discharge from the acid sulphate soil section of the continuum produced ～4.8 kg H₂SO₄?ha^?1 day^?1, a rate much higher than previous studies in similar systems. During baseflow conditions, the low pH water was rapidly buffered within the estuarine lake, with the pH increasing from 4.22 to 6.07 over a distance of ～250 m. The CO₂ evasion rates within the CASS were extremely high, averaging 2163?±?125 mmol m^?2 day^?1 in the dry period and 4061?±?259 mmol m^?2 day^?1 under flood conditions. Groundwater input of DIC could only account for 0.4 % of this evasion in the dry conditions and ～5 % during the flood conditions. We demonstrated that by utilising a spatiotemporal (multiple time-series stations) approach, the study was able to isolate distinct zones of differing hydrology and biogeochemistry, whilst providing more reasonable groundwater acid input estimates and air–water CO₂ flux estimates than some traditional sampling designs. This study highlights the notion that modified CASS wetlands can release large amounts of CO₂ to the atmosphere because of high groundwater acid inputs and extremely low surface water pH.  相似文献   

Characterization and use of biosorbents prepared from forestry waste and their washed extracts to reduce/remove chromium     

F. A. Santos  L. Alban  C. L. C. Frankenberg  M. Pires 《International Journal of Environmental Science and Technology》2016,13(1):327-338

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Nonparametric Estimation to Reconstruct the Deformation History of an Active Fold in the Caspian Basin     

I. R. Sánchez-Borrego  J. I. Soto  M. Rueda  I. Santos Betancor 《Mathematical Geosciences》2016,48(8):985-1011

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Nitrogen uptake in light versus darkness of the seagrass Zostera noltei: integration with carbon metabolism          下载免费PDF全文

Ana Alexandre  João Silva  Rui Santos 《Marine Ecology》2016,37(5):1050-1056

We conducted a study that shows that light and dark conditions do not affect the uptake rates of ammonium and nitrate by the seagrass Zostera noltei. This is an important advantage over some seaweed species in which these rates are severely reduced at night. In the light, the ammonium uptake rates were initially higher (15 and 20 μmol·g^?1·h^?1) and stabilized at a rate of 5 μmol·g^?1·h^?1 after 1 h, whereas in the dark the rates remained constant at a rate of 10 μmol·g^?1·h^?1 over the first 180 min of incubation. The rates of nitrate uptake in the light were high within the first 120 min of incubation (7.2–11.1 μmol·g^?1·h^?1) and decreased afterwards to lower values (0.8–3.9 μmol·g^?1·h^?1), whereas in the dark the rates fluctuated around 0.0–11.1 μmol·g^?1·h^?1 throughout the whole incubation time (7 h). The soluble sugar content of Z. noltei leaves increased significantly with both ammonium and nitrate incubations in the light, indicating the metabolic outcome of photosynthesis. In the dark, there was no significant variation in either the soluble sugar or in the starch content of leaves, rhizomes or roots in either the ammonium or nitrate incubations. However, the total starch content of plants decreased at night whereas the total soluble sugars increased, suggesting a process of starch catabolism to generate energy with the consequent production of smaller monosaccharide products. The starch content of rhizomes decreased significantly during the light incubations with nitrate but not with ammonium. These results suggest that carbohydrate mobilization is necessary for Z. noltei to account for extra energetic costs needed for the uptake and assimilation of nitrate. Furthermore, our results suggest that nitrate uptake, at least during the day, requires the mobilization of starch whereas the uptake of ammonium does not.  相似文献   

New discoveries of vertebrate remains from the Triassic of Riba de Santiuste,Guadalajara (Spain)     

Mélani Berrocal-Casero  Julia Audije-Gil  Rui Alexandre Castanhinha  Juan Alberto Pérez-Valera  Vanda Faria dos Santos  Manuel Segura 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(4):526-541

The palaeontological sites of Riba de Santiuste and Sienes (Riba de Santiuste area) are located in the province of Guadalajara, Spain. They include a stratigraphic interval in Muschelkalk facies belonging to the “Cuesta del Castillo Sandstones” Formation and “Royuela Dolostones, Marls and Mudstones” Formation. These sites include numerous fossil plants, direct vertebrate remains, and vertebrate swim traces. The vertebrate remains correspond to a multitude of anatomical elements of Sauropterygia (Nothosauroidea, Placodontia) and possible Archosauria (Rauisuchia) remains. The fossil material attributed to nothosaurs includes teeth, coracoids, a thoracic vertebra, some isolated vertebral centra, humerus, rib fragments, and some dorsal and caudal vertebrae. The remains attributed to placodonts correspond to fragments of skull, quadrate, teeth and osteoderms. Other undetermined sauropterygian remains, such as ulnas, fragments of long bones, fragments of ribs, and articular facets of ribs have been also recovered. Additionally, a fragment of mandible and an intervertebral disk of indeterminate reptiles whose size could be compatible with archosaurs are also described. These bones are exceptionally well-preserved because the fossilization processes have preserved the microstructure of the tissues. The sites also show vertebrate traces, with parallel scratch impressions interpreted as swim traces. The relative stratigraphic position and the palaeontological content of these sites suggest a Ladinian age (Middle Triassic). The interpretation of the sedimentary facies here described also suggests that the sites could correspond to detrital-carbonate mixed deposits of coastal intertidal to supratidal environments.  相似文献   

Chemical variables influencing microbial properties in composted tannery sludge-treated soil     

A. S. F. Araújo  V. M. Santos  A. R. L. Miranda  L. A. P. L. Nunes  C. T. S. Dias  W. J. de Melo 《International Journal of Environmental Science and Technology》2018,15(8):1793-1800

Repeated applications of composted tannery sludge to arable soils have the potential to greatly alter soil chemistry and thus potentially influence the soil microbial community over time. This study performed multivariate analyses using the data of soil microbial biomass, respiration, and enzymes activities obtained during 5 years (2010–2014) in a long-term experiment with composted tannery sludge amendment. The correlation between the soil microbial and chemical properties, via the analysis of similarity matrices, revealed calcium as the main single factor influencing the microbial properties, in 2010 and 2011. Afterward, chromium was the most important chemical variables driving the microbial properties in 2012, 2013, and 2014. The non-metric multidimensional scaling demonstrated that the soil microbial properties changed with composted tannery sludge application from 2010 to 2014. Multivariate analysis from soil microbial data with composted tannery sludge amendment, during 5 years, showed calcium and chromium as being the most significant variables influencing the soil microbial properties in composted tannery sludge-treated soil.  相似文献   

How the Distribution of Anthropogenic Nitrogen Has Changed in Narragansett Bay (RI,USA) Following Major Reductions in Nutrient Loads     

Autumn Oczkowski  Courtney Schmidt  Emily Santos  Kenneth Miller  Alana Hanson  Donald Cobb  Jason Krumholz  Adam Pimenta  Leanna Heffner  Sandra Robinson  Joaquín Chaves  Rick McKinney 《Estuaries and Coasts》2018,41(8):2260-2276

Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, the direct result of multiple wastewater treatment facility upgrades to tertiary treatment, a process which employs N removal. Here, we document ecosystem response to the N reductions and assess how the distribution of sewage N in Narragansett Bay has changed from before, during, and shortly after the upgrades. While others have observed clear responses when data were considered annually, our seasonal and regional comparisons of pre- and post-tertiary treatment dissolved inorganic nitrogen (DIN) concentrations and Secchi depth data, from bay-wide surveys conducted periodically from the early 1970s through 2016, resulted in only a few subtle differences. Thus, we sought to use stable isotope data to assess how sewage N is incorporated into the ecology of the Bay and how its distribution may have changed after the upgrades. The nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope measurements of particulate matter served as a proxy for phytoplankton, while macroalgae served as short-term integrators of water column bio-available N, and hard clams (Mercenaria mercenaria) as integrators of water column production. In contrast to other estuarine stable isotope studies that have observed an increased influence of isotopically lower marine N when sewage N is reduced, the opposite has occurred in Narragansett Bay. The tertiary treatment upgrades have increased the effluent δ¹⁵N values by at least 2‰. The plants and animals throughout Narragansett Bay have similarly increased by 1–2‰, on average. In contrast, the δ¹³C values measured in particulate matter and hard clams have declined by about the same amount. The δ¹⁵N results indicated that, even after the N reductions, sewage N still plays an important role in supporting primary and secondary production throughout the bay. However, the δ¹³C suggests that overall net production in Narragansett Bay has decreased. In the 5 years after the major wastewater treatment facilities came on-line for nutrient removal, oligotrophication has begun but sewage remains the dominant source of N to Narragansett Bay.  相似文献