Numerical study on the effect of submerged depth on the horizontal plate wave energy converter

The growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method （FVM）. In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid （VOF） is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea （HP） on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for HP=0.53 m （88% of the depth）. This efficiency is 17% larger than that found in the worst case （HP=0.46 m, 77% of the depth）.     

Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata,Southwest Atlantic)

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.     

Orographic distillation and spatio‐temporal variations of stable isotopes in precipitation in the North Atlantic

Little is known about the spatial and temporal variability of the stable isotopic composition of precipitation in the North Atlantic and its relationship to the North Atlantic Oscillation (NAO) and anthropogenic climate change. The islands of the Azores archipelago are uniquely positioned in the middle of the North Atlantic Ocean to address this knowledge gap. A survey of spatial and temporal variability of the stable isotope composition of precipitation in Azores is discussed using newly presented analyses along with Global Network of Isotopes in Precipitation data. The collected precipitation samples yield a new local meteoric water line (δ²H = 7.1 * δ¹⁸O + 8.46) for the Azores region and the North Atlantic Ocean. The annual isotopic mean of precipitation shows a small range for the unweighted and precipitation mass‐weighted δ¹⁸O‐H₂O values. Results show an inverse relation between the monthly δ¹⁸O‐H₂O and the amount of precipitation, which increases in elevation and into the interior of the island. Higher amounts of precipitation (from convective storm systems) do not correspond to the most depleted values of stable isotopes in precipitation. Precipitation shows an orographic effect with depleted δ¹⁸O‐H₂O values related to the Rayleigh effect. Monthly δ¹⁸O‐H₂O values for individual precipitation sampling stations show little relationship to air temperature. Results show a local source of moisture during the summer with the characteristics of the first vapour condensate. The stable isotope composition of precipitation is strongly correlated to the NAO index, and δ¹⁸O‐H₂O values show a statistically significantly trend towards enrichment since 1962 coincident with the increased air temperature and relative humidity due to climate change. Results are in line with observations of increasing sea surface temperature and relative humidity.     

Assessing the severity of disturbance for intertidal and subtidal macrobenthos: The phylum-level meta-analysis approach in tropical estuarine sites of northeastern Brazil

The phylum-level meta-analysis approach was applied to assess the status of disturbance of intertidal and subtidal macrobenthos in two estuaries in northeastern Brazil that are subject to different sources of pollution. Previously published estuarine data were included in the body of knowledge considered in the meta-analysis, to improve the reliability of the assessment of the Brazilian samples. Further multivariate and distributional techniques were applied to discriminate differences between estuaries and assess the pollution status of each. Phylum-level multivariate comparisons based on community attributes succeeded in discriminating the estuaries, and species distributions against abundance separated the estuaries in terms of pollution status. The meta-analysis indicated an almost indistinguishable moderate pollution status for both systems. Addition of new comparative data to the meta-analysis did not improve its sensitivity. Although the meta-analysis yielded satisfactory results in detecting disturbance in tropical estuaries, the method is not very sensitive to differences in sources of pollution.     

A multidimensional streamline-based method to simulate reactive solute transport in heterogeneous porous media

We present a new streamline-based numerical method for simulating reactive solute transport in porous media. The key innovation of the method is that both longitudinal and transverse dispersion are incorporated accurately without numerical dispersion. Dispersion is approximated in a flow-oriented grid using a combination of a one-dimensional finite difference scheme and a meshless approximation. In contrast to previous hybrid alternatives to incorporate dispersion in streamline-based simulations, the proposed scheme does not require a grid and, hence, it does not introduce numerical dispersion. In addition, the proposed scheme eliminates numerical oscillations and negative concentration values even when the dispersion tensor includes the off-diagonal coefficients and the flow field is non-uniform. We demonstrate that for a set of two- and three-dimensional benchmark problems, the new proposed streamline-based formulation compares favorably to two state of the art finite volume and hybrid Eulerian–Lagrangian solvers.     

An upwelling filament off southwest Iberia: Effect on the chlorophyll a and nutrient export

The present paper describes the chemical and biological characteristics of an upwelling filament off southern Iberia in October 2004, based on a total of 42 CTD casts, along with ADCP velocity measurements distributed by an almost regular grid of 15 km mean spacing. Stations were sampled from the surface to a maximum depth of 400 dbar, for nutrients (nitrate, phosphate and silicate) and chlorophyll a determination. The effect of cross-shelf exchange of nutrients and chlorophyll a between the coastal and oceanic waters was also investigated. Data revealed that, during the cruise conducted under relaxed winds, a relatively small filament was formed down to 75 m. However, an amount of 180 t of chlorophyll a was estimated there accompanied by low nutrient concentrations. The observed water properties reveal that SW Iberia is similar to NW Iberia, showing the continuity of the Canary Upwelling System along the Iberian Peninsula, one of poorest upwelling systems of the oceanic eastern boundaries. Nevertheless, the amounts of chlorophyll and nutrients transported through the filament are significant, revealing that those play a key role in the seaward export of matter with an important impact on the regional oceanography of this region. Considering the periods of strong upwelling events and the extent of their duration along the year, the amounts of exported matter must be hugely increased and responsible for the high productivity of these waters.     

Sensitivity analysis of a morphodynamic modelling system applied to a coastal lagoon inlet

This work investigates the recent morphological changes at the inlet of a complex coastal system (Ria de Aveiro lagoon, Portugal). This study was carried out using bathymetric data analysis and numerical simulations obtained with the 2DH morphodynamic modelling system MORSYS2D. The present simulations considered only tidal forcing, and a sensitivity analysis was performed by tuning the formula used to compute the sediment transports. A non-uniform sediment grain size distribution for the Ria de Aveiro inlet is considered in the numerical simulations, based on surveys performed in this area. The model results are analysed to assess if they resemble the observed trends of erosion and deposition, as calculated from bathymetric data. A quantitative analysis of the differences between the bathymetric changes obtained through surveys and the numerical results over a period of 3 years considering different sediment transport formulations shows that the formulations of Ackers and White (1973) and Engelund and Hansen (1967) are the ones that best describe the morphodynamic changes driven by tides in the Ria de Aveiro inlet.     

Fingerprinting TCE in a bedrock aquifer using compound-specific isotope analysis

A dual isotope approach based on compound-specific isotope analysis (CSIA) of carbon (C) and chlorine (Cl) was used to identify sources of persistent trichloroethylene (TCE) that caused the shut-down in 1994 of a municipal well in an extensive fractured dolostone aquifer beneath Guelph, Ontario. Several nearby industrial properties have known subsurface TCE contamination; however, only one has created a comprehensive monitoring network in the bedrock. The impacted municipal well and many monitoring wells were sampled for volatile organic compounds (VOCs), inorganic parameters, and CSIA. A wide range in isotope values was observed at the study site. The TCE varies between -35.6‰ and -21.8‰ and from 1.6‰ to 3.2‰ for δ(13) C and δ(37) Cl, respectively. In case of cis-1,2-dichloroethene, the isotope values range between -36.3‰ and -18.9‰ and from 2.4‰ to 4.7‰ for δ(13) C and δ(37) Cl, respectively. The dual isotope approach represented by a plot of δ(13) C vs. δ(37) Cl shows the municipal well samples grouped in a domain clearly separate from all other samples from the property with the comprehensive well network. The CSIA results collected under non-pumping and short-term pumping conditions thus indicate that this particular property, which has been studied intensively for several years, is not a substantial contributor of the TCE presently in the municipal well under non-pumping conditions. This case study demonstrates that CSIA signatures would have been useful much earlier in the quest to examine sources of the TCE in the municipal well if bedrock monitoring wells had been located at several depths beneath each of the potential TCE-contributing properties. Moreover, the CSIA results show that microbial reductive dechlorination of TCE occurs in some parts of the bedrock aquifer. At this site, the use of CSIA for C and Cl in combination with analyses of VOC and redox parameters proved to be important due to the complexity introduced by biodegradation in the complex fractured rock aquifer. It is highly recommended to revisit the study when the municipal well is back into full operation.     

Orders of magnitude increase in soil erosion associated with land use change from native to cultivated vegetation in a Brazilian savannah environment

The Brazilian savanna (cerrado) is a large and important economic and environmental region that is experiencing significant loss of its natural landscapes due to pressures of food and energy production, which in turn has caused large increases in soil erosion. However the magnitude of the soil erosion increases in this region is not well understood, in part because scientific studies of surface runoff and soil erosion are scarce or nonexistent in the cerrado as well as in other savannahs of the world. To understand the effects of deforestation we assessed natural rainfall‐driven rates of runoff and soil erosion on an undisturbed tropical woodland classified as ‘cerrado sensu stricto denso’ and bare soil. Results were evaluated and quantified in the context of the cover and management factor (C‐factor) of the Universal Soil Loss Equation (USLE). Replicated data on precipitation, runoff, and soil loss on plots (5 × 20 m) under undisturbed cerrado and bare soil were collected for 77 erosive storms that occurred over 3 years (2012 through 2014). C‐factor was computed annually using values of rainfall erosivity and soil loss rate. We found an average runoff coefficient of ~20% for the plots under bare soil and less than 1% under undisturbed cerrado. The mean annual soil losses in the plots under bare soil and cerrado were 12.4 t ha^‐1 yr^‐1 and 0.1 t ha^‐1 yr^‐1, respectively. The erosivity‐weighted C‐factor for the undisturbed cerrado was 0.013. Surface runoff, soil loss and C‐factor were greatest in the summer and fall. Our results suggest that shifts in land use from the native to cultivated vegetation result in orders of magnitude increases in soil loss rates. These results provide benchmark values that will be useful to evaluate past and future land use changes using soil erosion models and have significance for undisturbed savanna regions worldwide. Copyright © 2015 John Wiley & Sons, Ltd.