Ambiente e Sustentabilidade | Artigos em revistas internacionais / Papers in international journals
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- Leaching of pyrite by acidophilic, heterotrophic, iron-oxidizing bacteria in pure and mixed culturePublication . Nicolau, Paula Bacelar; Johnson, D. BarrieSeven strains of heterotrophic iron-oxidizing acidophilic bacteria were examined to determine their abilities to promote oxidative dissolution of pyrite (FeS2) when they were grown in pure cultures and in mixed cultures with sulfur-oxidizing Thiobacillus spp. Only one of the isolates (strain T-24) oxidized pyrite when it was grown in pyrite-basal salts medium. However, when pyrite-containing cultures were supplemented with 0.02% (wt/vol) yeast extract, most of the isolates oxidized pyrite, and one (strain T-24) promoted rates of mineral dissolution similar to the rates observed with the iron-oxidizing autotroph Thiobacillus ferrooxidans. Pyrite oxidation by another isolate (strain T-21) occurred in cultures containing between 0.005 and 0.05% (wt/vol) yeast extract but was completely inhibited in cultures containing 0.5% yeast extract. Ferrous iron was also needed for mineral dissolution by the iron-oxidizing heterotrophs, indicating that these organisms oxidize pyrite via the “indirect” mechanism. Mixed cultures of three isolates (strains T-21, T-23, and T-24) and the sulfur-oxidizing autotroph Thiobacillus thiooxidans promoted pyrite dissolution; since neither strains T-21 and T-23 nor T. thiooxidans could oxidize this mineral in yeast extract-free media, this was a novel example of bacterial synergism. Mixed cultures of strains T-21 and T-23 and the sulfur-oxidizing mixotroph Thiobacillus acidophilus also oxidized pyrite but to a lesser extent than did mixed cultures containing T. thiooxidans. Pyrite leaching by strain T-23 grown in an organic compound-rich medium and incubated either shaken or unshaken was also assessed. The potential environmental significance of iron-oxidizing heterotrophs in accelerating pyrite oxidation is discussed.
- Possible applications for municipal solid waste fly ashPublication . Ferreira, Célia; Ribeiro, A. B.; Ottosen, Lisbeth M.The present study focuses on existing practices related to the reuse of Municipal Solid Waste (MSW) fly ash and identifies new potential uses. Nine possible applications were identified and grouped into four main categories: construction materials (cement, concrete, ceramics, glass and glass–ceramics); geotechnical applications (road pavement, embankments); “agriculture” (soil amendment); and, miscellaneous (sorbent, sludge conditioning). Each application is analysed in detail, including final-product technical characteristics, with a special emphasis on environmental impacts. A comparative analysis of the different options is performed, stressing the advantages but also the weaknesses of each option. This information is systemized in order to provide a framework for the selection of best technology and final products. The results presented here show new possibilities for this waste reuse in a short-term, in a wide range of fields, resulting in great advantages in waste minimization as well as resources conservation.
- Delineation of estuarine management areas using multivariate geostatistics: the case of Sado EstuaryPublication . Caeiro, Sandra; Goovaerts, Pierre; Painho, Marco; Costa, Maria HelenaThe Sado Estuary is a coastal zone located in the south of Portugal where conflicts between conservation and development exist because of its location near industrialized urban zones and its designation as a natural reserve. The aim of this paper is to evaluate a set of multivariate geostatistical approaches to delineate spatially contiguous regions of sediment structure for Sado Estuary. These areas will be the supporting infrastructure of an environmental management system for this estuary. The boundaries of each homogeneous area were derived from three sediment characterization attributes through three different approaches: (1) cluster analysis of dissimilarity matrix function of geographical separation followed by indicator kriging of the cluster data, (2) discriminant analysis of kriged values of the three sediment attributes, and (3) a combination of methods 1 and 2. Final maximum likelihood classification was integrated into a geographical information system. All methods generated fairly spatially contiguous management areas that reproduce well the environment of the estuary. Map comparison techniques based on κ statistics showed that the resultant three maps are similar, supporting the choice of any of the methods as appropriate for management of the Sado Estuary. However, the results of method 1 seem to be in better agreement with estuary behavior, assessment of contamination sources, and previous work conducted at this site.
- Heavy metals in MSW incineration fly ashesPublication . Ferreira, Célia; Ribeiro, A. B.; Ottosen, Lisbeth M.Incineration is a common solution for dealing with the increasing amount of municipal solid waste (MSW). During the process, the heavy metals initially present in the waste go through several transformations, ending up in combustion products, such as fly ash. This article deals with some issues related to the combustion of MSW and the formation of fly ash, especially in what concerns heavy metals. Treatment of the flue gas in air pollution control equipment plays an important role and the basic processes to accomplis this are explained. Fly ash from a semi-dry flue gas treatment system is characterized regarding its physical-chemical properties : pH, solubility, chemical composition, and leaching, amongst others. Results indicate a high alkalinity and the presence oflarge amounts of calcium, chlorides, sulfates, carbonates, sodium and potassium. Metal concentrations in fly ash are : 6, 2 g/kg for zinc, 2, 4 g/kg for lead, 1, 7 gzkg fior iron, and 7, 9 g/kg for magnesium. Copper, manganese, chromium and cadmium are also present with 546, 338, 104 and 91 mg/kg ofBy ash, respectively. These results are extremely important in subsequent studies on the treatment of fly ash.
- Spatial sampling design for sediment quality assessment in estuariesPublication . Caeiro, Sandra; Painho, Marco; Goovaerts, Pierre; Costa, Helena; Sousa, SandraUnusual difficulties are encountered when characterizing the spatial distribution of the properties that collectively define the state of estuaries. Due to the variability of these estuarine conditions, greater sampling efforts are often necessary to describe estuarine environments, as compared to other aquatic systems. That is why in coastal management studies, where the collection of data is sometimes very difficult and time-consuming, a robust sampling strategy is essential. The aim of this study is to design a spatial sampling strategy for estuarine sediments, using prior information on the spatial variation of sediment granulometry. Systematic unaligned sampling with a grid cell size of 750 × 500 m was chosen on the basis of semi-variogram analysis, and was shown to have distinct advantages. This design was sampled for sediment parameters using a GPS-receiver and mapped within the digitized shoreline of the estuary. The estuary shoreline was digitized on the basis of aerial ortho-photography with tidal ebb determination. The sampling is intended to define the boundaries of environmental management areas for the Sado Estuary, situated on the west coast of Portugal. The research represents one of the initial phases in the development of a Sado Estuary environmental management system integrated into a Geographic Information System.
- Removal of selected heavy metals from MSW fly ash by the electrodialytic processPublication . Ferreira, Célia; Jensen, Pernille; Ottosen, Lisbeth M.; Ribeiro, A lexandreThis paper aims to assess the applicability of the electrodialytic remediation technique for the removal of zinc, lead, copper and cadmium from municipal solid waste (MSW) incinerator fly ash. A broad range of experimental conditions were studied including current densities, remediation times, use of assisting agents and cell design. Several operational problems were identified during the electrodialytic experiments, among which are formation of precipitates, dryness of sample and partial dissolution of sample creating preferential pathways for the electric current. These problems may explain the low remediation efficiencies obtained. Comparison between experiments showed that generally the use of Na-gluconate as assisting agent leads to better results than distilled water. Increasing the concentration of the assisting agent also results in higher removals.
- Assessing heavy metal contamination in Sado EstuaryPublication . Caeiro, Sandra; Costa, Maria Helena; Ramos, Tomás B.; Fernandes, F.; Silveira, N.; Coimbra, Ana Paula; Medeiros, G.; Painho, MarcoThe Sado Estuary in Portugal is a good example of a site where human pressures and ecological values collide with each other. An overall contamination assessment has never been conducted in a way that is comprehensible to estuary managers. One of the aims of this work was to select different types of index to aggregate and assess heavy metal contamination in the Sado Estuary in an accessible manner. Another aim was to use interpolation surfaces per metal to compare and gauge the results of the indices and to assess the contamination separately per metal. Seventy-eight stations were sampled within the main bay of the estuary and a set of heavy metals and metalloids was established, Cd, Cu, Pb, Cr, Hg, Al, Zn and As. The sediment fine fraction content, organic matter and redox potential were also analysed. Various indices for contamination, background enrichment and ecological risk were used, tested, compared and performance-evaluated. All metals and metalloids were strongly correlated, and the indices appear to reflect heavy metal variability satisfactorily. Difficulties were found in some indices regarding boundary definition (minimum and maximum) and comparability with other estuaries, thus better methods of standardization should be a priority issue. According to the index that has the highest performance score within the group of ecological risk indices – the Sediment Quality Guideline Quotient – only 3% of the stations are highly contaminated and register a high potential for observing adverse biological effects, whereas 47% display moderate contamination. This index can be complemented with the contamination index, which allows more site-specific and accurate information on contaminant levels. If the aim of work on contamination evaluation is to assess the overall contamination of a study area, the indices are highly appropriate. For spatial and source evaluation per metal, interpolation surfaces should also be used.
- Benthic biotope index for classifying habitats in the sado estuary: PortugalPublication . Caeiro, Sandra; Costa, Maria Helena; Goovaerts, Peter; Marco, Painho; Flavio, MartinsAn integration of sediment physical, chemical, biological, and toxicity data is necessary for a meaningful interpretation of the complex sediment conditions in the marine environment. Assessment of benthic community is a vital component for that interpretation, yet their evaluation is complex and requires a large expenditure of time and funds. Thus, there is a need for new tools that are less expensive and more understandable for managers. This paper presents a benthic biotope index to predict from physical and chemical variables the occurrence of macrobenthic habitats. Parameters such as sediment type, organic matter, depth, and hydrodynamic parameters were selected, through a discriminant analysis, to compute the index. Other authors have used multivariate methods to determine the benthic biotopes for Sado Estuary. The index proved to be a valid tool to classify and assess the spatial patterns of benthic habitat and to synthesize stress biotope gradients.
- Effect of major constituents of MSW fly ash during electrodialytic remediation of heavy metalsPublication . Ferreira, Célia; Ribeiro, Alexandra; Ottosen, Lisbeth M.Electrodialytic remediation (EDR) is a technique in which contaminants are removed from waste material by applying an electric field which forces their movement into concentration chambers through ion-exchange membranes. In the current work EDR is used for the treatment of heavy metal–contaminated fly ash. The objective is to study the impact of major constituents of fly ash on remediation times, on efficiency, and on the performance of membranes. The results show that major constituents foul the ion-exchange membranes, decreasing their ability to transport metal ions out of the waste compartment.
- Kinetics of electrodialytic extraction of Pb and soil cations from a slurry of contaminated soil finesPublication . Jensen, Pernille E.; Ottosen, Lisbeth M.; Ferreira, Célia; Villumsen, ArneThe objective of this work was to investigate the kinetics of Pb-removal from soil fines during electrodialytic remediation in suspension, and study the simultaneous dissolution of common soil cations (Al, Ca, Fe, Mg, Mn, Na and K). This was done to evaluate the possibilities within control of the remediation process to leave a final product suitable for reuse. The Pb-remediation process could be divided into four phases: (1) a “lag-phase”, (2) a period with a high removal rate (7.4 mg/day in average at 40 mA), (3) a period with a low removal rate, and (4) a period where no further Pb-removal was obtained. During the first phase, dissolution of carbonates was the prevailing process, resulting in a corresponding loss of soil mass. During this phase, the investigated ions accounted for the major current transfer, while, as remediation proceeded, hydrogen ions increasingly dominated the transfer. During phase (3) the high conductivity and low voltage suggested that removal may be accelerated by increasing the current density. Overall, 97% of the Pb could be extracted, reducing the final Pb-concentration to 25 mg/kg. The order of removal rates was: Ca > Pb > Mn > Mg > K > (Al and Fe).