Characterization of a limestone in a batch fluidized bed reactor for sulfur retention under oxy-fuel operating conditions

CO₂ and SO₂ are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O₂ and recirculated CO₂. With this technology the CO₂ concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO₂ recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO₂ partial pressure, SO₂ concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO₃ or by sulfation of the CaO (indirect sulfation) formed by CaCO₃ calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO₂ partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO₂ partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO₂ concentration.     

High mercury bioaccumulation in Pacific salmons from the Sea of Okhotsk and the Bering Sea

Mercury (Hg) accumulation in fishes is a serious threat for food security because mercury induces dieseases. Here we studied the total mercury content in four species of Pacific salmon (pink, chum, sockeye and chinook), caught in the Sea of Okhotsk, the Bering Sea, and the Kuril oceanic waters. Results show that the lowest concentration of mercury was found in the pink salmon, and the highest was 5–6 times higher in sockeye. Hg concentrations exceed several times those in other species of Pacific salmon from the North Pacific     

Food Security in Protracted Crises: Building More Effective Policy Frameworks

This paper considers the principal elements that underpin policy frameworks for supporting food security in protracted crisis contexts. It argues that maintaining the food entitlements of crisis-affected populations must extend beyond interventions to ensure immediate human survival. A 'policy gap' exists in that capacities for formulating policy responses to tackle the different dimensions of food insecurity in complex, fluid crisis situations tend to be weak. As a result, standardised, short-term intervention designs are created that fall short of meeting the priority needs of affected populations in the short and long term and only partially exploit the range of policy options available. The paper discusses key attributes of agency frameworks that could support more effective policy processes to address longer term as well as immediate food security needs. Additionally, it points to some main challenges likely to be encountered in developing such frameworks and, with the participation of beneficiaries, translating them into effective action.     

Cellular alterations in Mytilus galloprovincialis (LMK) and Tapes philippinarum (Adams and Reeve, 1850) as biomarkers of environmental stress: field studies in the Lagoon of Venice (Italy)

A long-term biomonitoring study was carried out in the Lagoon of Venice (North-East Italy) with the aim of evaluating variations in biological responses to environmental stress in estuarine bivalves. Two different species, the mussel Mytilus galloprovincialis and the clam Tapes philippinarum, both widespread in the Lagoon, were studied in several sites. Two cellular biomarkers: lysosomal membrane stability in digestive cells and thickness of digestive epithelia, were evaluated in native organisms (on a seasonal basis), and in organisms which have been transferred from a reference site to several differently influenced ones. Results indicate that, to some extent, both test and organisms were able to highlight site-specific differences, but the effects of pollution were generally more easily detected by reduction in lysosomal stability than by reduction in digestive tubule epithelium. Further findings show that the inherent variability of a number of natural parameters, particularly in the reference sites, produced less effective results when biological responses in the reference organisms were compared with the polluted ones. The assessment of the two conditions was most valuable when they referred to the 25-75% range of values comprised within the seasonal medians, recorded respectively in control and polluted sites. Impaired from steady states were most effectively distinguished when the control values were medians from two reference locations. Lately, the overall results indicate that both biomarkers are more suitably deployed through the translocation approach, revealing it to be more sensitive than traditional biomonitoring, at least in the sense that it may overcome problems related to the adaptation of native organisms to sub lethal chronic pollution levels.     

Evolution of lead concentration in the particulate matter of Santiago,Chile, since 1978

Santiago is a city of over 4.5 million inhabitants and about 415000 motor vehicles using leaded gasoline. Twenty-four-hour samples were taken of total and fractionated particulate matter using a low-volume system and two Andersen cascade impactors, between 1978 and 1989 at different sites of the city of Santiago. Lead concentrations were determined by atomic absorption spectrophotometry. The results show that Pb concentrations vary greatly depending on the site selected. Higher values are always detected near the city center. An annual variation with the highest value during the autumn-winter period (May–July) is clearly observed. Lead concentrations versus size are clearly biased to particles smaller than 2 µm. A correlation is observed between Pb concentrations and the suspended particulate matter under 3 µm at different sites of the city. The curves of Pb concentration versus size of the aerosols emitted by the gas exhaust of motor vehicles using leaded gasoline are similar to those of the atmospheric aerosols.     

Management of the zinc chain

In this study, a substance chain approach as a tool contributing to a sustainable development has been tested by applying it to zinc. An analysis of the western world zinc substance chain has been made in order to identify the main routes of zinc losses from the chain. Technologically feasible options to improve the management of the chain have been selected and applied to a modelled chain. With the emphasis on resource management, the model has been designed to evaluate the impact of options on the input of primary zinc into the chain. The consequences of the options for the energy resources have been analyzed.Redesigning the global zinc chain using the chosen technologically feasible options has lead to a lower primary zinc input when compared to the present chain, but a 45% primary zinc input is still needed, while the improved chain requires 8% less energy. To obtain a further decrease of primary zinc input in the chain, research should focus on emission abatement during zinc usage, where especially corrosion of galvanized steel forms a problem, and on the prevention of mixed-product waste streams with a low average zinc concentration. The energy analysis shows that options to improve the zinc chain should be carried out carefully, avoiding extra demands on the energy resources.The study indicates that designing a substance chain, along with even simple modelling, results in a good tool to calculate the impact of different kinds of options on the total chain.     

Book reviews

Ecological Politics in an Age of Risk. Ulrich Beck, translated by Amos Weisz, 1995 Cambridge, Polity Press, first published Germany 1988. ISBN 0 7456 077632, hb £39.50; ISBN 0 7456 13772, pk £12.95

Environmentally Sustainable Business: a local and regional perspective. Peter Roberts, 1995, London, Paul Chapman. ISBN 1 85396 240 6, price not given

Methods of Environmental Impact Assessment. Peter Morris & Riki Therivel (Eds) 1995, London, UCL Press, 378 pp. ISBN 1 85728 117 9, hb £45.00; 1 85728 118 7, pb £14.95

A Guide to Local Environmental Auditing. Hugh Barton & Noel Bruder, 1995, London, Earthscan, 370 pp. ISBN 1 85 383 2340, pb £18.95

Household Waste Recycling. Richard Waite, 1995, London, Earthscan, ISBN 1 8538 3 2421, hb £29.95

A Seed in Time: Proceedings of the 3rd International Conference on Urban and Community Forestry. Forestry Commission, 1994. ISBN 0 885 38 328 3, £9.50 inc p&p (Copies available from: Marcus Sangster, Forestry Commission, 231 Corstorphine Road, Edinburgh EH12 7AT)

Environmental Policy in New Zealand: the politics of clean and green? Tom Buhrs & Robert Bartlett, 1993, Auckland, Oxford University Press viii + 192 pp.

Green Politics. Stephen Rainbow, 1993, Auckland, Oxford University Press xv + 106 pp.

The Future of Community Lands: human resources. E. Ndione, P. DeLeener, M. Ndiaye, P. Jacolin & J.-P. Perier, 1995, London, Intermediate Technology, 236 pp. ISBN 1 339 2480, £14.95     

Improvement of the Bag-Mediated Filtration System for Sampling Wastewater and Wastewater-Impacted Waters

Environmental surveillance of poliovirus (PV) plays an important role in the global program for eradication of wild PV. The bag-mediated filtration system (BMFS) was first developed in 2014 and enhances PV surveillance when compared to the two-phase grab method currently recommended by the World Health Organization (WHO). In this study, the BMFS design was improved and tested for its usability in wastewater and wastewater-impacted surface waters in Nairobi, Kenya. Modifications made to the BMFS included the size, color, and shape of the collection bags, the filter housing used, and the device used to elute the samples from the filters. The modified BMFS concentrated 3–10 L down to 10 mL, which resulted in an effective volume assayed (900–3000 mL) that was 6–20 times greater than the effective volume assayed for samples processed by the WHO algorithm (150 mL). The system developed allows for sampling and in-field virus concentration, followed by transportation of the filter for further analysis with simpler logistics than the current methods. This may ultimately reduce the likelihood of false-negative samples by increasing the effective volume assayed compared to samples processed by the WHO algorithm, making the BMFS a valuable sampling system for wastewater and wastewater-impacted surface waters.     

Immunotoxic effects of organotin compounds in Tapes philippinarum

One of the most harmful groups of coastal pollutants is the organotin compounds (OTCs) which have severe effects on both aquatic organisms and mammals including humans. The immunotoxic effects of OTCs were studied in the cultivated clam Tapes philippinarum by determining the immunosuppressant role on in vitro yeast phagocytosis at low doses (0.01, 0.05, 0.1 μM). The phagocytic index was significantly reduced in an irreversible non-lethal manner depending on concentration and lipophilic affinity. The order of inhibition was TBT≥DBT>MBT for butyltins and TPTC>TPTA≥TPTH for triphenyltins.     

The impact of economic activity in Asturias on greenhouse gas emissions: consequences for environmental policy within the Kyoto Protocol framework

Climate change is one of the major worldwide environmental concerns. It is especially the case in many developed countries, where the greenhouse gas emissions responsible for this change are mainly concentrated. For the first time, the Kyoto Protocol includes an international agreement for the reduction of the net emissions of these gases. To fulfil this agreement measures designed to reduce or limit current emissions have to be brought into force. Consequently, fears have arisen about possible consequences on competitiveness and future development of manufacturing activities and the need for support mechanisms for the affected sectors is obvious. In this paper, we carry out a study of the emissions of gases responsible for climate change in Asturias (Spain), a region with an important economic presence of sectors with intensive emissions of CO(2), the chief greenhouse gas. To be precise, in the first place, the volumes of direct emissions of the said gases in 1995 were calculated, showing that the sectors most affected by the Kyoto Protocol in Asturias are iron and steel and electricity production. Secondly, input-output analysis was applied to determine the direct and indirect emissions and the direct, indirect and induced emissions of the different production sectors, respectively. The results derived from the direct and indirect emissions analysis and their comparison with the results of the former allow us to reach some conclusions and environmental policy implications.