Controlling factors and environmental implications of mercury contamination in urban and agricultural soils under a long-term influence of a chlor-alkali plant in the North–West Portugal

This study aims at assessing the extent of total mercury (Hg) contamination in urban and agricultural soils under long-term influence of a chlor-alkali plant, located at about 1 km away from a town centre. Moreover, it aims at identifying the main factors controlling Hg contents’ distribution and associated potential hazards to environment and human health. The median value of total Hg for soil surface layer (0–10 cm) was 0.20 mg/kg (data ranging from 0.050 to 4.5 mg/kg) and for subsurface layer (10–20 cm) 0.18 mg/kg (data ranging from 0.046 to 3.0 mg/kg). The agricultural area showed higher Hg concentrations (ranging from 0.86 to 4.5 mg/kg) than urban area (ranging from 0.05 to 0.61 mg/kg), with some results exceeding target values set by the Dutch guidelines. Mercury concentrations observed in the studied area are more likely to be associated with the influence of the chlor-alkali plant and with the use of historically contaminated sludges and water from a nearby lagoon in agriculture, than to the impacts of urban development. The statistical correlations between Hg concentrations and soil properties suggest that anthropogenic metal sources should influence the spatial distribution more than the geological properties. Although the Hg emissions were drastically reduced 10 years ago, the area under influence of the chlor-alkali plant is still facing potential health and environmental threats arising from soil contamination.     

Gravity data as a tool for landfill study

This paper shows the potential of gravity data to map a buried landfill bottom topography. To this end, a gravity inversion method is presented for estimating the landfill’s bottom depths at discrete points assuming a decrease of the density contrast with depth according to a hyperbolic law. The method’s efficiency was tested using synthetic data from simulated waste landfills, producing estimated bottom topographies very close to the true ones. The method’s potentiality has been further evaluated in applying it to the gravity data from the abandoned Thomas Farm Landfill site, Indiana, USA, whose bottom topography is known. The estimated topography showed close agreement with the known Thomas Farm Landfill’s bottom topography.     

CI-Miner: semantically enhancing scientific processes

The realization of an international cyberinfrastructure of shared resources to overcome time and space limitations is challenging scientists to rethink how to document their processes. Many known scientific process requirements that would normally be considered impossible to implement a few years ago are close to becoming a reality for scientists, such as large scale integration and data reuse, data sharing across distinct scientific domains, comprehensive support for explaining process results, and full search capability for scientific products across domains. This article introduces the CI-Miner approach that can be used to aggregate knowledge about scientific processes and their products through the use of semantic annotations. The article shows how this aggregated knowledge is used to benefit scientists during the development of their research activities. The discussion is grounded on lessons learned through the use of CI-Miner to semantically annotate scientific processes in the areas of geo-sciences, environmental sciences and solar physics: A use case in the field of geo-science illustrates the CI-Miner approach in action.     

A high-resolution Holocene record on the Southern Brazilian shelf: Paleoenvironmental implications

A high-resolution, multi-proxy record has been used to determine the environmental changes during the Holocene on the southern Brazilian shelf. Present oceanographic conditions reveal wind and freshwater input as the determinants of short-term productivity changes in the study area. Magnetic susceptibility and grain-size variations, together with proxies of productivity (organic carbon, carbon accumulation rate, Ba, Sr, and Ca content, Ba/Al, Ba/Ti, and Al/Ti ratios) were analyzed and compared with proxies of redox condition (V/Ti ratio), terrigenous input (Fe/Ca and Ti/Ca ratios), as well as other Element/Ti ratios, to evaluate the paleoceanographic and paleoclimatic changes over the period.The core covers a time interval of about 7650 years, with sedimentation rates varying from 0.025 to 0.250 cm a⁻¹, which represent time intervals of between 8 and 80 a per sample. There is a clear change in the sedimentation rate at about 2800 B.P.All grain-size and elemental results indicate the occurrence of conspicuous changes between 5200 and 5000 cal. B.P., as well as between 3000 and 2800 cal. B.P. A comparison of the results with the palynological information available from the adjacent continental areas suggests that the sedimentary changes in this last interval may be correlated with the onset of modern climatic conditions in South America, and especially, with the onset of the Plata Plume Water, a water mass that carries cold, less saline waters towards the north. However, minor changes are observed at ca. 1500 B.P. and are correlated with an increase in the atmospheric humidity. Furthermore, a time-series analysis undertaken using several proxies indicated the occurrence of Sub-Milankovitch cycles, which may be compared with those reported worldwide.     

Trans-alkaline magmatism in the Serrinha–Pedro Velho Complex,Borborema Province,NE Brazil and its correlations with the magmatism in eastern Nigeria

The Solânea Complex (572 ± 8 Ma) comprises various intrusions that total 200 km². It cuts Palaeoproterozoic migmatized orthogneisses of the Serrinha–Pedro Velho Complex, which is part of the São José do Campestre Massif, North Tectonic Domain of the Borborema Province, NE Brazil. It is a post-collisional intrusion constituted of coarse-grained biotite–amphibole monzogranites, fine-grained leucogranites and diorites. Major, trace and rare earth elements data, used to constrain the origin and nature of these rocks, indicate that the monzogranites display chemical features of weakly peraluminous ferro-potassic trans-alkaline granitoids, similar to coeval occurrences described in eastern Nigerian. Sm–Nd data together with the whole rock geochemical data suggest that: (I) the monzogranites were generated by partial melting of tonalitic gneiss from the lower crust, leaving behind a granulitic residue; (II) the diorites originated by partial melting of an enriched lithospheric mantle; (III) the evolution of the Solânea Complex involved magma mixing between the monzogranites and diorites. K-feldspar and amphibole fractionation appear to have occurred during the evolution of the monzogranites.Leucogranites constituting an elliptical shaped intrusion (80 km²), the Dona Inês Pluton, are intruded to the north of the Solânea Complex. They also occur as small intrusions cross-cutting the border of the Solânea Complex. Geochemical and isotopic data suggest that the leucogranites were generated by melting of crustal Palaeoproterozoic rocks. Rb–Sr data gave an age of 544 ± 16 Ma.Trans-alkaline magmatism is associated with ductile–brittle deformation in the Serrinha–Pedro Velho Complex of the São José do Campestre Massif. This event follows the peak of an extensional-related high-temperature metamorphism (upper amphibolite to granulite facies), with estimated age of 578 to 574 Ma. If a pre-Gondwana reconstruction is considered, this event is seen to extend to the African side of Gondwana in eastern Nigeria.     

Spinel–quartz high temperature paragenesis in Al–Fe granulites from the Ihouhaouene area (NW Hoggar, Algeria)

The spinel–quartz-bearing Al–Fe granulites from Ihouhaouene (In Ouzzal, West Hoggar) have a migmatitic appearance with quartzo-feldspathic layers intercalated with restitic layers. These granulites are characterized by a hercynitic spinel–quartz assemblage typical of high grade terranes. The stability of the spinel–quartz assemblage is attributed to an elevation of temperature (from 800 to >1100 °C) at high pressures (10–11 kbar), followed by an isothermal decompression from 9 to 5 kbar, an evolution typical of the In Ouzzal clockwise P–T path. The Al–Fe granulites’ history can be subdivided into different successive crystallisation stages. During the first stage, the spinel–quartz assemblage formed, probably following a prograde event that also produced partial melting. During a second stage, the primary spinel–garnet–sillimanite–quartz paragenesis broke-down to give rise to the secondary assemblage. The metamorphic evolution and phase relations during this stage are shown in P–T–X pseudosections calculated for the simple FMASH system. These pseudosections show that the orthopyroxene–cordierite–spinel symplectite appeared during a high temperature decompression, as a product of destabilisation of garnet in sillimanite-free microdomains with high X_Mg values. At the same time, the spinel–quartz association broke-down into cordierite in Fe-rich microdomains. Average pressure and temperature estimates for the orthopyroxene–spinel–garnet–cordierite–quartz association are close to the thermal peak of metamorphism (1000 ± 116 °C at 6.3 ± 0.5 kbar). With decreasing temperatures garnet–sillimanite corona developed from the breakdown of the primary spinel–quartz assemblage in the Fe-rich microdomains, whereas cordierite–spinel formed at the expense of primary sillimanite and garnet in the Mg-rich microdomains.     

Instrumental and digital coronagraphy for the observation of the Uranus satellites’ upcoming mutual events

Ground-based observations of faint satellites nearby their planets with 1-2 m class telescopes usually do not allow for high quality astrometry and photometry, due to saturation by the primary or to poor S/N ratio on the satellite images, generally embedded on the scattered light of the planet. Earth-based observations of the Uranus satellites’ upcoming mutual events in 2007-2008 are no exception. In most cases, the event will take place at 4 arcs or less from the planet, with “planet minus satellite” brightness differences of 10 magnitudes. So as to make feasible the observations of these important phenomena, we have developed a prototype of a coronagraph of simple design making use of good quality commercial optical systems. Pilot tests made with this coronagraph with a telescope of show that it is possible to obtain S/N ratios of 50 or higher for 10 s exposures, for satellites as close as 2 Uranus radii from the planet center. We have also developed numerical algorithms which perform digital coronagraphy in the images, with the elimination of the influence of the planets’ scattered light. This procedure considerably improves the S/N ratio of the satellite images (with or without a coronagraph instrument) and shall be applied in the reduction of the observations of the Uranus events so as to achieve the highest possible photometric and astrometric quality.     

Electrochemical Ozone Production as an Environmentally Friendly Technology for Water Treatment

Perspectives, advances and environmental aspects concerning electrochemical ozone production applied to water purification are presented and discussed in relation to the conventional corona process (silent electric discharge). Ozone generated using a laboratory‐made electrochemical reactor was applied for the discoloration/degradation of dyes used in the Brazilian textile industry and for degradation of endocrine disruptors. A constant ozone load of 0.35 ± 0.02 g/h was used throughout. The study, concerning color removal from dye solutions, revealed that total discoloration is rapidly achieved. The degradation rate of the textile dyes evaluated by TOC is little affected by the dye composition and considerably influenced by the pH and ozonation time. Analysis of the COD/TOC‐ratio indicates that ozonation increases oxidation feasibility of the organic matter (dye by‐products) when compared to the original compounds. Ozonation of mixed aqueous solutions containing different endocrine disruptors revealed these compounds are totally degraded with a very high removal rate.     

Nocturnal Surface-Layer Characteristics at the Bottom of a Valley

Nighttime data collected at the bottom of a valley locatedin southern Brazil are studied. The analyzed quantities includemomentum and sensible heat fluxes, turbulence statistics andintermittency factors, and their relationship to the stability parameter.The proper interval for averaging and flux calculations is foundto be 20 min, based on the comparison of the fluxes and therandom error associated in their determination. Each data seriesis classified as calm or windy, according to the mean windspeed. A much better dependency of the variables in terms of thestability parameter is found under windy conditions. Analysis ofthe wind direction and topographic scales indicates that distortioneffects under calm conditions affect the flow, while the flow is inlocal equilibrium for windy conditions. In this case, the sensible heatflux shows a minimum for a value of z/L=0.08, while the momentumflux and the normalized scales of the wind components andtemperature decrease monotonically as the stability increases. Anintermittency factor is proposed and shown to be larger (moreintermittency) for more stable conditions.