Fe,Mn, P and S Speciation in Sediments from the Capivara Hydroelectric Dam Lake (Brazil) as an Indicator of Anthropogenic Influences

The conservation of large water resources is essential for the preservation of human life. The quantification and, more importantly, the speciation of chemical substances that indicate the presence of anthropogenic contamination in water resources are of great importance. This paper presents the results of analysis for the determination of organic, inorganic and total phosphorus, pseudo‐sulfur, and iron and manganese, in five fractions, in water sediments collected from the Capivara Hydroelectric Power Plant, Brazil. A study on the seasonal variation of these parameters was conducted, with data having been collected in the winter and in the summer, at two sites along the dam, 5 km apart, close to the city of Primeiro de Maio. Phosphorous was found in sediments and adjacent soil in the organic form (OP), and was used as an indicator of anthropogenic influence on the reservoir banks. Speciation of potentially toxic Mn showed that it is present in the exchangeable fraction of the 0–5 cm depth layer (sediment/water interface), making its transfer to the water column possible. Results from this study showed that domestic and industrial effluent treatment measures are needed for the preservation of the quality of aquatic environments.     

Aerosol characterization and optical thickness retrievalsusing GOME and METEOSAT satellite data

Summary ?Retrievals of atmospheric aerosol optical thickness are highly dependent on the choice of the class describing the aerosol properties leading to significant errors while using classes available in the literature. High spectral resolution measurements from GOME (Global Ozone Monitoring Experiment) between the ultraviolet and the near infrared can be used for an accurate characterization of the aerosol optical properties. The radiometer MVIRI (METEOSAT Visible and Infrared Imager) on board the geostationary satellite METEOSAT, while being equipped only with broadband VIS channel, ensures an adequate half-hourly monitoring of the atmospheric conditions over a large portion of the Earth. The present algorithm is based on a combination of data from both sensors for the retrieval of the aerosol optical thickness at the reference wavelength of 0.55 μm (AOT). A case of a desert dust outbreak from the African continent over the Atlantic Ocean is examined. AOT values obtained using a priori fixed classes taken from the literature are compared with those retrieved with this algorithm using the GOME-derived classes. Systematic differences of the order of a few tenths on average are found which remain significant also after considering the measurement errors. This represents a novelty introduced by the synergetic use of both sensors. Received March 13, 2002     

The 18 June 1997 Companion supercells: Multiparametric Doppler radar analysis

Summary ?On 18 June 1997 two simultaneous supercells 50 km apart swept the Po valley W-NW to E-SE. An exceptional hailfall lasted for more than 3 hours over a strip 200 km wide. There are no records of companion supercells over northern Italy, a fact that attributes to the present observations a considerable meteorological interest. The forcing due to a baroclinic wave disturbance created the synoptic conditions favourable for storm development. A closer mesoscale analysis conducted using the Local Analysis and Prediction System (LAPS) indicates that the interaction of the storm systems with the low-level frontal high-humidity band is a key aspect of their evolution. The operational polarimetric Doppler weather radar of S. Pietro Capofiume was used for a volumetric analysis of the storm system focusing on the microphysical and dynamical structure, and wind patterns. Reflectivity and Doppler wind fields document the transition from multicell to supercell phase for one of the storms. Differential reflectivity (Z_DR) fields are examined. Positive Z_DR columns are detected in connection with the storms strong updraft. Flare echoes hint to the presence of substantial hailshafts. The spectrum width field is used to investigate internal motions. Limited dual Doppler analysis is carried out and results are discussed in terms of storm evolution properties. Received June 30, 1999/Revised February 3, 2000     

A computational study of nonresonant cross-field diffusion of energetic particles due to their interaction with interplanetary magnetic decreases

We present a new method of calculating cross-field diffusion of charged particles due to their interactions with interplanetary magnetic decreases (MDs) in high heliospheric latitudes. We use a geometric model that evaluates perpendicular diffusion to the ambient magnetic field as a function of particle's gyroradius, MD radius, ratio between fields outside and inside the MD, and a random impact parameter. We use Ulysses magnetic field data of 1994 to identify the MDs and get the empirical size and magnetic field decrease distribution functions. We let protons with energies ranging from 100 keV to 2 MeV interact with MDs. The MD characteristics are taken from the observational distribution functions using the Monte Carlo method. Calculations show that the increase in diffusion tends to saturate when particles' gyroradius becomes as large as MD radii, and that particles' gyroradius increases faster than diffusion distance as the energy of the particles is increased.     

Moisture source for the Amazon Basin: a study of contrasting years

The regions where the divergence of vertically integrated water vapor flux, averaged over a season or a year, is positive (negative) are sources (sinks) of moisture for the atmosphere. An aerial river is defined as a stream of strong water vapor flux connecting a source and a sink. Moisture flux, its divergence, and sources and sinks over the tropics of South and Central America and the adjoining Atlantic Ocean are obtained for dry years and for wet years in the Amazon Basin. Results show that the Amazon Basin is a sink region for atmospheric moisture in all seasons and that there are two source regions for the moisture in the basin, one situated in the South Atlantic and the other in the North Atlantic, both located equator-ward of the respective subtropical high-pressure centers. The convergence of moisture increases over the Amazon Basin in austral summer, and at the same time it decreases in the Pacific and Atlantic ITCZs. Box model calculations reveal that the wet years, on the average, present about 55 % more moisture convergence than the dry years in the Amazon Basin. A reduction in the moisture inflow across the eastern and northern boundaries of the basin (at 45°W and at the Equator, respectively) and an increase in the outflow across the southern boundary (at 15°S) lead to dry conditions. The annual mean contribution of moisture convergence to the precipitation over the Amazon Basin is estimated to be 70 %. In the dry years, it lowers to around 50 %. The net convergence of water vapor flux over the basin is a good indicator of the wet or dry condition.     

S-wave Velocity Models in the Scotia Sea Region, Antarctica, from Nonlinear Inversion of Rayleigh Waves Dispersion

—More than 60 events recorded by four recently deployed seismic broadband stations around Scotia Sea, Antarctica, have been collected and processed to obtain a general overview of the crust and upper mantle seismic velocities.¶Group velocity of the fundamental mode of Rayleigh waves in the period between 10 s to 30–40 s is used to obtain the S-wave velocity versus depth along ten different paths crossing the Scotia Sea region. Data recorded by two IRIS (Incorporated Research Institutions for Seismology) stations (PMSA, EFI) and the two stations of the OGS-IAA (Osservatorio Geofisico Sperimentale—Instituto Antarctico Argentino) network (ESPZ, USHU) are used.¶The Frequency-Time Analysis (FTAN) technique is applied to the data set to measure the dispersion properties. A nonlinear inversion procedure, "Hedgehog," is performed to retrieve the S-wave velocity models consistent with the dispersion data.¶The average Moho depth variation on a section North to South is consistent with the topography, geological observations and Scotia Sea tectonic models.¶North Scotia Ridge and South Scotia Ridge models are characterised by similar S-wave velocities ranging between 2.0 km/s at the surface to 3.2 km/s to depths of 8 km/s. In the lower crust the S-wave velocity increases slowly to reach a value of 3.8 km/s. The average Moho depth is estimated between 17 km to 20 km and 16 km to 19 km, respectively, for the North Scotia Ridge and South Scotia Ridge, while the Scotia Sea, bounded by the two ridges, has a faster and thinner crust, with an average Moho depth between 9 km and 12 km.¶On other paths crossing from east to west the southern part of the Scotia plate and the Antarctic plate south of South Scotia Ridge, we observe an average Moho depth between 14 km and 18 km and a very fast upper crust, compared to that of the ridge. The S-wave velocity ranges between 3.0 and 3.6 km/s in the thin (9–13 km) and fast crust of the Drake Passage channel. In contrast the models for the tip of the Antarctic Peninsula consist of two layers with a large velocity gradient (2.3–3.0 km/s) in the upper crust (6-km thick) and a small velocity gradient (3.0–4.0) in the lower crust (14-km thick).     

Highly nonlinear wind waves in Currituck Sound: dense breather turbulence in random ocean waves

Ocean Dynamics - We analyze surface wave data taken in Currituck Sound, North Carolina, during a storm on 4 February 2002. Our focus is on the application of nonlinear Fourier analysis (NLFA)...     

Marine debris review for Latin America and the wider Caribbean region: from the 1970s until now, and where do we go from here?

The available literature on marine debris from Latin America and the Wider Caribbean Region was collected and linked, reviewing their methodologies and principal results (quantities, composition and spatial-temporal patterns). The study region comprises 52 coastal countries of which only 14 had registers of works on marine debris. A total of 70 works were available and 69 had their full contents accessed. Brazil dominated the available literature with 70% of the documents. Beaches were the most studied environment, and plastics the prevalent form of contamination in the whole region. The exposure of marine biota (species, type of contact, consequences) was highlighted. The studied region, although still little exploited by this sort of research, shows the same contamination patterns observed world-wide. We also contacted 40 researchers in the area, collecting scientific contributions, opinions and suggestions for improvement of this research field. Further advances and new (urgently needed) lines of research are also discussed.     

BET_VH: exploring the influence of natural uncertainties on long-term hazard from tephra fallout at Campi Flegrei (Italy)

In this paper, we explore the effects of the intrinsic uncertainties upon long-term volcanic hazard by analyzing tephra fall hazard at Campi Flegrei, Italy, using the BET_VH model described in Marzocchi et al. (Bull Volcanol, 2010). The results obtained show that volcanic hazard based on the weighted average of all possible eruptive settings (i.e. size classes and vent locations) is significantly different from an analysis based on a single reference setting, as commonly used in volcanic hazard practice. The long-term hazard map for tephra fall at Campi Flegrei obtained here accounts for a wide spectrum of uncertainties which are usually neglected, largely reducing the bias intrinsically introduced by the choice of a specific reference setting. We formally develop and apply a general method to recursively integrate simulations from different models which have different characteristics in terms of spatial coverage, resolution and physical details. This outcome of simulations will be eventually merged with field data through the use of the BET_VH model.