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71.
Due to the growing rate of urbanization and a rapid and unplanned development in many tropical coastal areas, there continues to be an increasing concern in relation to the impact of anthropogenic activities on mangrove sediments. In southeastern Brazil, the Sepetiba Bay becomes an example of an ecosystem in the process of accelerated degradation. Previous studies highlighted the activities related with zinc processing by an industry on the Madeira’s Island as one of the main source of heavy metal to Sepetiba Bay. Despite the end of the industrial activities in the area, the waste reservoir became the main source of pollutant to the surrounding area. Analyses of Cd, Pb, Cu, Cr, Hg, Ni, Zn, particle size and nutrients of 20 sediment samples collected in the mangrove of the Madeira Island showed that the waste reservoir is the main source of contaminant to the mangrove. The statistic analyses showed that the moisture content and organic matter play an important role in the geochemical dynamic of heavy metal in the area. 相似文献
72.
N. Vogt A.‐N. Chen A.F.J. Moffat J.M. Matthews R. Kuschnig D.B. Guenther J.F. Rowe S.M. Rucinski D. Sasselov W.W. Weiss 《Astronomische Nachrichten》2013,334(10):1101-1106
Variability on all time scales between seconds and decades is typical for cataclysmic variables (CVs). One of the brightest and best studied CVs is TT Ari, a nova‐like variable which belongs to the VY Scl subclass, characterized by occasional low states in their light curves. It is also known as a permanent superhumper at high state, revealing “positive” (PS > P0) as well as “negative” (PS < P0) superhumps, where PS is the period of the superhump and P0 the orbital period. TT Ari was observed by the Canadian space telescope MOST for about 230 hours nearly continuously in 2007, with a time resolution of 48 seconds. Here we analyze these data, obtaining a dominant “negative” superhump signal with a period PS = 0.1331 days and a mean amplitude of 0.09 mag. Strong flickering with amplitudes up to 0.2 mag and peak‐to‐peak time scales of 15–20 minutes is superimposed on the periodic variations. We found no indications for significant quasi‐periodic oscillations with periods around 15 minutes, reported by other authors. We discuss the known superhump behaviour of TTAri during the last five decades and conclude that our period value is at the upper limit of all hitherto determined “negative” superhump periods of TTAri, before and after the MOST run. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
73.
Ursula Mendoza Arthur Ayres Neto Rodrigo C. Abuchacra Cátia Fernandes Barbosa Alberto G. Figueiredo Jr. Manoela C. Gomes Andre L. Belem Ramsés Capilla Ana Luiza S. Albuquerque 《Geo-Marine Letters》2014,34(4):297-314
The Cabo Frio region in the state of Rio de Janeiro, southeast coast of Brazil, is characterized by a local coastal upwelling system and converging littoral sediment transport systems that are deflected offshore at Cabo Frio, as a consequence of which a thick cross-shelf sediment deposit has developed over time. To investigate the evolution of this muddy deposit, geophysical, sedimentological and geochemical data from four sediment cores (3.8–4.1 m in length) recovered in water depths between 88 and 141 m were analyzed. The high-resolution seismic data show variable sediment thicknesses ranging from 1 to 20 m, comprising two sedimentary units separated by a high-impedance layer at a depth of about 10 m below the seafloor at the coring sites. According to the available age datings, the upper sedimentary unit is late Pleistocene to Holocene in age, whereas the lower unit (not dated) must, by implication, be entirely Pleistocene in age. The boomer-seismic reflection signal can be divided into three echo-types, namely transparent (inner shelf), stratified (middle shelf) and reflective (outer shelf), each type seemingly related to the local sediment composition. The upper 4 m of the upper sedimentary unit is dominated by silty sediment on the middle shelf, and by upward-fining sediments (silty sand to sandy silt) on the inner and outer shelf. The downcore trends of P-wave velocity, gamma-ray density and acoustic impedance are largely similar, but generally reversed to those of water and organic carbon contents. Total organic carbon contents increase with decreasing mean grain size, periodic fluctuations suggesting temporal changes in the regional hydrodynamics and primary productivity fuelled by the local upwelling system. The reconstruction of sedimentation rates in the course of the Holocene is based on 35 AMS age datings of organic material recovered from variable downcore depths. These range from a maximum of 13.3 cm/decade near the base of the inner shelf core (7.73–7.70 ka BP) to generally very low values (<0.11 cm/century) over the last thousand years in all cores. Over the last 6 ka there appear to have been three distinct sedimentation peaks, one between 6 and 5 ka BP, another between 4 and 3 ka PB, and one around 1 ka BP. Due to different time intervals between dates, not every peak is equally well resolved in all four cores. Based on the similar sedimentology of the inner and outer shelf cores, an essentially identical sedimentation model is proposed to have been active in both cases, albeit at different times. Thus, already during the last glacial maximum, alongshore sediment transport was deflected offshore by a change in shoreline orientation caused by the Cabo Frio structural high. The source of terrigenous material was probably a barrier-island complex that was subsequently displaced landward in the course of sea-level rise until it stabilized some 6.5 ka BP along the modern coast. 相似文献
74.
C. Cavarroc C. Moutou D. Gandolfi B. Tingley M. Ollivier S. Aigrain R. Alonso J.-M. Almenara M. Auvergne A. Baglin P. Barge A. S. Bonomo P. Bordé F. Bouchy J. Cabrera S. Carpano L. Carone W. D. Cochran S. Csizmadia H. J. Deeg M. Deleuil R. F. Díaz R. Dvorak M. Endl A. Erikson M. Fridlund M. Gillon E. W. Guenther T. Guillot A. Hatzes G. Hébrard L. Jorda A. Léger H. Lammer T.-O. Lev C. Lovis P. J. MacQueen T. Mazeh A. Ofir H. Parviainen T. Pasternacki M. P?tzold D. Queloz H. Rauer D. Rouan B. Samuel A. Santerne J. Schneider J. Weingrill G. Wuchterl 《Astrophysics and Space Science》2012,337(2):511-529
CoRoT is a space telescope which aims at studying internal structure of stars and detecting extrasolar planets. We present here a list of transits detected in the light curves of stars observed by CoRoT in two fields in the anti-center direction: the LRa03 one observed during 148 days from 3 October 2009 to 1 March 2010 followed by the SRa03 one from the 5 March 2010 to the 29 March 2010 during 25 days. 5329 light curves for the LRa03 field and 4169 for the SRa03 field were analyzed by the detection team of CoRoT. Then some of the selected exoplanetary candidates have been followed up from the ground. In the LRa03 field, 19 exoplanet candidates have been found, 8?remain unsolved. No secured planet has been found yet. In the SRa03 field, there were 11 exoplanetary candidates among which 6 cases remain unsolved and 3 planets have been found: CoRoT-18b, CoRoT-19b, CoRoT-20b. 相似文献
75.
Shallow-water hydrothermal activity is widely present at Azores archipelago. Organisms in such environments present great potential as sentinels of the effects derived from chronically exposure to increased temperature, metal concentrations and reduced pH. This study aimed to evaluate metal concentration in Corallina elongata collected at locations exposed and not exposed to shallow-water hydrothermal activity and evaluate changes in its calcareous structure. Elemental concentration was determined and morphometric analysis was performed by scanning electron microscopy. Thicker cell walls and a bleached appearance were observed on C. elongata specimens from the hydrothermally active location, as well as increased concentrations of elements associated to volcanic activity.This study reports on metal accumulation and morphometric changes in the calcareous structure of C. elongata from a hydrothermally active location, adding new data for further research on such habitats and communities, providing an insight on how coralline algae might be affected by ocean acidification. 相似文献
76.
Ricardo Henrique Moreton Godoi Patricia Y. Hirata Andre V. L. Bitterncourt Ana F. L. Godoi Miguel Jafelicci Jr Francisco J. dos Santos Rafael Bini Liuz F. Zara Cynara L. N. Cunha Ana P. K Soares Eduardo F. Gobbi Sanja Potgieter‐Vermaak José E. F. C. Gardolinski José M. Reis Neto Giuliana Gatto Rotondo Rene van Grieken 《洁净——土壤、空气、水》2012,40(4):364-372
Suspended particles and dissolved substances in water provide reactive surfaces, influence metabolic activity and contribute to the net sediment deposition. It therefore plays an important part in the ecology and quality of the water mass. The water quality in reservoirs is crucial and it is naturally maintained by flushing and sedimentation, which continuously remove phosphorus from the water. In some reservoirs, however, these removal processes are countered by recycling of ions which could play a key role to start and/or maintain the eutrophic state. The combination of macro‐, trace‐ and microanalysis techniques can be useful to trace pollution sources through a chemical fingerprint, whether be during an acute environmental disaster or a long‐term release of pollutants. The water quality and total metal content of reservoir sediments were assessed in a reservoir, situated in the capital of the Paraná State, in the South‐Eastern part of Brazil. The goal of this paper was to determine the metal presence in the sediment and metal and ionic speciation in the Green River reservoir water. Water and bed sediment samples, collected from various sites during 2008 and 2009, were investigated using XRF, ICP‐OES, ICP‐MS, XRD and zeta potential measurements. Based on the results, the heavy metal concentration and chemical composition of the suspended matter in the water samples, as well as the sediment's chemical composition will be discussed. 相似文献
77.
78.
This study used hydrographic data (CTD and ADCP) collected along the north Brazilian continental shelf and the adjacent oceanic area (the north Brazilian zone) and 13 years of monthly data of sea surface temperatures (SSTs) obtained from the Tropical Rainfall Measuring Mission satellite microwave images. In July and August 2001, the core of the North Brazil Current (NBC) with a velocity exceeding 1.2 m s?1 in the upper 150 m was observed near the break of the north Brazilian continental shelf. The satellite and in situ SSTs from the same time indicate that relatively cold waters (<27.5 °C) extended throughout the NBC region where the vertical distribution of temperature displayed a rise of the 26 °C isotherm to near the surface on transects where the NBC was more intense. These observations indicated that the NBC plays an important role in temperature changes in the water column near and/or over the north Brazilian continental shelf margin even at times when, theoretically, the NBC may be expected to be less intense (April–May) and warm waters dominate the area. The distribution of accumulated temperature change reveals that the NBC may contribute to possible nutrient upwelling of the bottom boundary layer along the continental shelf to surficial areas and offshore following the NBC deflection or merely into the North Atlantic. 相似文献
79.
Impacts of Weather Conditions Modified by Urban Expansion on Surface Ozone: Comparison between the Pearl River Delta and Yangtze River Delta Regions 总被引:11,自引:0,他引:11
In this paper, the online weather research and forecasting and chemistry (WRF-Chem) model
is used to explore the impacts of urban expansion on regional weather conditions and its implication
on surface ozone concentrations over the Pearl River Delta(PRD) and Yangtze River Delta(YRD) regions.
Two scenarios of urban maps are used in
the WRF-Chem to represent the early 1990s (pre-urbanization) and the current urban distribution in the
PRD and the YRD. Month-long simulation results using the above land-use scenarios for March 2001 show
that urbanization increases both the day- and night-time 2-m temperatures by about 0.6oC and
1.4oC, respectively. Daytime reduction in the wind speed by about 3.0 m s-1 is larger than
that for the nighttime (0.5 to 2 m s-1). The daytime increase in the PBL height (> 200 m) is
also larger than the nighttime (50--100 m). The meteorological conditions modified by urbanization
lead to detectable ozone-concentration changes in the PRD and the YRD. Urbanization increases the
nighttime surface-ozone concentrations by about 4.7%--8.5% and by about 2.9%--4.2% for the daytime.
In addition to modifying individual meteorological variables, urbanization also enhances the convergence
zones, especially in the PRD. More importantly, urbanization has different effects on the surface ozone
for the PRD and the YRD, presumably due to their urbanization characteristics and geographical locations.
Even though the PRD has a smaller increase in the surface temperature than the YRD, it has (a) weaker
surface wind speed, (b) smaller increase in PBL heights, and (c) stronger convergence zones. The latter
three factors outweighed the temperature increase and resulted in a larger ozone enhancement in the PRD
than the YRD. 相似文献
80.
Relaxed Eddy Accumulation Simulations of Aerosol Number Fluxes and Potential Proxy Scalars 总被引:1,自引:1,他引:0
Andreas Held Edward Patton Luciana Rizzo Jim Smith Andrew Turnipseed Alex Guenther 《Boundary-Layer Meteorology》2008,129(3):451-468
Direct eddy-covariance measurements of aerosol number fluxes obtained during the 2007 CHATS field experiment in Dixon, California,
USA are compared with relaxed eddy accumulation simulations using temperature and water vapour concentration as proxy scalars.
After a brief discussion of the limited time response of the aerosol measurement, the applicability of temperature and water
vapour concentration as proxy scalars for aerosol number concentration is investigated by evaluating scalar and spectral correlation
coefficients as simple measures of scalar similarity. In addition, the proportionality factor b, which compensates for the use of a constant sampling flow in relaxed eddy accumulation, is derived from the time series
of aerosol number, temperature and water vapour, and its variability is analyzed. The reduction of the b factor due to application of a deadband, i.e. the rejection of data when the vertical wind speed is close to zero, is evaluated
for all three studied scalars, and compared with published functional relationships. In this study, using temperature or water
vapour as proxy scalars for aerosol number shows no advantage over the use of a constant b factor. Thus, it is suggested to apply a deadband H
REA
= w′/σ
w
= 0.6 to 0.8 (where w′ is the vertical velocity fluctuation and σ
w
is its standard deviation), to use a theoretical b factor based on a parameterization that includes a stability dependence, and to calculate the deadband effect according to
a derived relation for aerosol relaxed eddy accumulation. 相似文献