The potential leaching and mobilization of trace elements from FGD-gypsum of a coal-fired power plant under water re-circulation conditions

Experimental and geochemical modelling studies were carried out to identify mineral and solid phases containing major, minor, and trace elements and the mechanism of the retention of these elements in Flue Gas Desulphurisation (FGD)-gypsum samples from a coal-fired power plant under filtered water recirculation to the scrubber and forced oxidation conditions. The role of the pH and related environmental factors on the mobility of Li, Ni, Zn, As, Se, Mo, and U from FGD-gypsums for a comprehensive assessment of element leaching behaviour were also carried out. Results show that the extraction rate of the studied elements generally increases with decreasing the pH value of the FGD-gypsum leachates. The increase of the mobility of elements such as U, Se, and As in the FGD-gypsum entails the modification of their aqueous speciation in the leachates; UO₂SO₄, H₂Se, and HAsO₂ are the aqueous complexes with the highest activities under acidic conditions. The speciation of Zn, Li, and Ni is not affected in spite of pH changes; these elements occur as free cations and associated to SO₄² in the FGD-gypsum leachates. The mobility of Cu and Mo decreases by decreasing the pH of the FGD-gypsum leachates, which might be associated to the precipitation of CuSe₂ and MoSe₂, respectively. Time-of-Flight mass spectrometry of the solid phase combined with geochemical modelling of the aqueous phase has proved useful in understanding the mobility and geochemical behaviour of elements and their partitioning into FGD-gypsum samples.     

The potential leaching and mobilization of trace elements from FGD-gypsum of a coal-fired power plant under water re-circulation conditions

Experimental and geochemical modelling studies were carried out to identify mineral and solid phases containing major, minor, and trace elements and the mechanism of the retention of these elements in Flue Gas Desulphurisation (FGD)-gypsum samples from a coal-fired power plant under filtered water recirculation to the scrubber and forced oxidation conditions. The role of the pH and related environmental factors on the mobility of Li, Ni, Zn, As, Se, Mo, and U from FGD-gypsums for a comprehensive assessment of element leaching behaviour were also carried out. Results show that the extraction rate of the studied elements generally increases with decreasing the pH value of the FGD-gypsum leachates. The increase of the mobility of elements such as U, Se, and As in the FGD-gypsum entails the modification of their aqueous speciation in the leachates; UO₂SO₄, H₂Se, and HAsO₂ are the aqueous complexes with the highest activities under acidic conditions. The speciation of Zn, Li, and Ni is not affected in spite of pH changes; these elements occur as free cations and associated to SO₄ ² in the FGD-gypsum leachates. The mobility of Cu and Mo decreases by decreasing the pH of the FGD-gypsum leachates, which might be associated to the precipitation of CuSe₂ and MoSe₂, respectively. Time-of-Flight mass spectrometry of the solid phase combined with geochemical modelling of the aqueous phase has proved useful in understanding the mobility and geochemical behaviour of elements and their partitioning into FGD-gypsum samples.     

Effect of cooling rate and laser process parameters on additive manufactured Fe–Ti–C metal matrix composites microstructure and carbide morphology

In this paper, laser additive manufacturing (LAM) of Fe–TiC composite coating on AISI 1030 carbon steel is investigated using a numerical and experimental method. In order to have a desired result using LAM, it is crucial to understand the effects of the process parameters’ values on the TiC morphology and microstructure. For this purpose, the LAM process is numerically simulated in order to calculate cooling rate and peak temperature. Experimental data and numerical results are in good agreement in terms of the phase development. Results show that cooling rate plays a crucial role in phase transformation in the clad, however, final microstructure strongly depends on the cooling rate and powder's chemical composition. Two main carbide morphologies (i.e. dendritic and particulate) are studied and relevant cooling rates are detected. Based on this paper and developed map, it is possible to control the cooling rate in order to achieve specific carbide morphologies in the clad. In this study, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to characterize clads’ microstructure.     

National pathways to the Sustainable Development Goals (SDGs): A comparative review of scenario modelling tools

The recently-adopted global Sustainable Development Goals (SDGs) will have significant implications for national development planning in both developed and developing countries in the post-2015 period to 2030. Integrated, nationally-owned SDG strategies will be at the centre of national efforts to implement the new sustainable development agenda. The long-run processes and systems perspective that are inherent in the SDGs present complex analytical problems for policymakers and analysts. Scenario analysis and quantitative modelling will be important analytical tools to support national sustainable development planning, and there is an increasingly sophisticated suite of models available to decision makers. This paper reviews and assesses a broad range of different quantitative models that have the potential to support national development planning for the SDGs. The study develops a typology and inventory of 80 different models, and then reviews the comparative strengths, weaknesses and general utility of different models through an initial screening and subsequent multi-criteria analysis of short-listed models. Current gaps in model capabilities are highlighted in the context of providing analytical support for national development planning for the SDGs. While some existing models are particularly relevant, it is unlikely that an ideal model can analyse all SDG targets and variables of interest within a single modelling framework. Top-down ‘macro framework’ models are likely to be more useful for undertaking system-level or economy-wide scenario analysis driven by the national long-term goals and targets, and for exploring trade-offs and synergies among sectors. Bottom-up sectoral models will be able to support far more detailed option-level impact analysis of concrete interventions, technologies and investments. Combining both approaches within an analytical framework will provide a robust approach for analysis and decision-making. The results highlight a range of potential gaps in current modelling capabilities, and provide some new tools to assist with model selection.     

Participatory modelling for sustainable development: Key issues derived from five cases of natural resource and disaster risk management

Stakeholder participation is considered a key principle for sustainable development in the context of natural resource and disaster risk management. Participatory modelling (PM) is an interactive and iterative process in which stakeholder involvement is supported by modelling and communication tools. Planning and decision-making for sustainable development (SD)integrate three substantive dimensions − social, ecological and economic. The procedural dimension of SD, however, is equally important, and here we see great potential for PM. In this study, we evaluate five PM research projects against criteria for the procedural dimension of SD. This provides a basis for identifying key issues and needs for further research into PM for SD. While the cases show great potential, especially for supporting knowledge integration, learning and transparent handling of values and perspectives, they indicate a particular need to develop PM in respect of organizational integration. This issue is closely connected to the possibility of effectively implementing PM in practice.     

不同物料堆肥富里酸的结构特征的研究

通过三维荧光平行因子分析（EEM-PARAFAC）和二维相关光谱（2DCOS）分析了富含木质纤维素类物料（果蔬废物和杂草废物）和富含木质素类物料（秸秆废物和园林修剪废物）堆肥形成的富里酸的结构和组成.结果显示，两类堆肥物料形成的富里酸结构差异显著.虽然两类物料的荧光组分含量及变化基本相似，但是特征官能团与其荧光组分的变化顺序却不同.富含木质纤维素类物料堆肥形成的富里酸中类酪氨酸和类色氨酸先于芳环形成，而富含木质素类物料堆肥形成的富里酸中芳环先于类酪氨酸和类色氨酸.并且，研究发现在堆肥高温期和腐熟期，富里酸的芳环含量在木质纤维类和木质类物料中分别增加了约10%和5%，脂肪族的含量分别下降了约10%和6%，说明堆肥过程中富里酸结构中脂肪族逐渐降解并伴随其芳香性逐渐增加；结构方程模型结果表明，类富里酸、脂肪族基团和羧基是富里酸中芳环形成的关键组分.本文研究结果可为明确堆肥过程中富里酸的形成提供理论基础.     

Modelling feeding flow related shrinkage defects in aluminum castings

The process modelling of shape casting is geometrically complex and computationally very challenging. Besides the three-dimensional complex shapes with multiple domains, the defects of interest to industry arise as a consequence of the interaction amongst a range of phenomena. Conventionally, the key phenomena and defect prediction are modelled through empirical relations applied to the simulation results. Such approaches are neither comprehensive nor reliable. This paper presents a 3-D model that is capable of predicting the formation of shrinkage defects explicitly as a function of the interacting continuum phenomena, i.e. free surface flow, heat transfer, and solidification, in complex three-dimensional geometries which allows to identify the distinction between surface depression, surface connected cavities and internal cavities.The model solves the coupled macroscopic conservation equations for mass, momentum, and energy with a phase change during solidification. In the model, the volume deficit due to solidification can either be compensated by depression of the outside surface or by creating a cavity that initiates either on the surface or in the interior of the casting. The solidification morphology is taken into account by using a parameter, which depends on the fraction solid, in the momentum equation. By using an adapted free surface algorithm, it is suitable to predict surface connected defects: depressed surfaces and caved surfaces. A critical pressure serves as a criterion to open internal shrinkage cavities. The model does not need to search for connected zones to feed shrinkage, but the shrinkage distribution will automatically emerge from the continuity equation.This advanced shrinkage model has experimentally been validated successfully using two Al-Si alloys, a skin freezing eutectic alloy and a mushy freezing hypo-eutectic alloy.     

第一届亚太区安全健康海报、录像带创作比赛即将在港举行我国有关职业安全卫生单位积极报名参赛

第一届亚太区安全健成海报、录像带创作比赛即将在港举行我国有关职业安全卫生单位积极报名参赛第十三届亚太区职业安全健康组织大会及展览会将于１９９７年４月２１日至４月２６日在香港举行，这是香港职业安全健康局首次主办的大型国际性会议，预计将有二千多人参加，此...     

THE DEVELOPMENT OF A COMBINED WATER QUALITY INDEX1

ABSTRACT: Use-oriented benefits and treatment costs analysis has been incorporated into a water quality index to show an economically optimized concentration for the treatment of the pollutants and the resulting water quality. This combined water quality index can be used in decisionmaking at the federal and local government levels. Five major pollutants, i.e., coliforms, nitrogen, phosphorus, suspended solids, and detergent, have been considered for the municipal waste water. With each higher level of improvement the treatment costs increase accordingly and the benefits associated with the reuse of this treated waste water will increase too but not for the nutrient removal in agricultural use. The optimal concentration is determined when the marginal costs equal the marginal benefits. The combined water quality index is the combination of the maximum net benefits and the water quality index of the optimized residual concentrations. This water quality index is zero dollars for the Tucson region in this study. The possible reclaimed use of municipal waste water is for agricultural irrigation and recreational lakes for the Tucson region.     

Computer programs for calculating soil loss on a watershed basis

A series of computer programs designed to predict gross annual soil loss on a watershed basis by application of the Universal Soil Loss Equation (USLE) have been developed. The programs provide an easy-to-use, flexible, and standardized means of organizing base data and applying the USLE to large land areas. The programs can be used to assess and to evaluate the effects of changing land-use patterns and conservation practices on soil losses. Critical or problem areas can be readily identified. The USLE Computer Programs are a useful research tool for investigators involved in water quality management, 208 planning, or conservation research.The package of computer programs consists of three main components: data input, the Main Program, and the Totals Program. Input data include both field base data describing the watershed and corresponding values for the factors in the USLE. The Main Program calculates the average rate of soil loss (tons/ acre/yr) and the total soil loss (tons/yr) for the smallest subunit of the watershed identified as the soil unit. Also calculated is an RKLS factor, which is an indication of the erosive potential of a given soil type, slope, and slope length, under a particular rainfall regime. The Totals Program aggregates soil unit losses into progressively larger units, that is, field, farm, subwatershed, and watershed units. An example of the programs' versatility and use is presented.