Treatment of exhaust fluorescent lamps to recover yttrium: experimental and process analyses

The paper deals with recovery of yttrium from fluorescent powder coming from dismantling of spent fluorescent tubes. Metals are leached by using different acids (nitric, hydrochloric and sulphuric) and ammonia in different leaching tests. These tests show that ammonia is not suitable to recover yttrium, whereas HNO(3) produces toxic vapours. A full factorial design is carried out with HCl and H(2)SO(4) to evaluate the influence of operating factors. HCl and H(2)SO(4) leaching systems give similar results in terms of yttrium extraction yield, but the last one allows to reduce calcium extraction with subsequent advantage during recovery of yttrium compounds in the downstream. The greatest extraction of yttrium is obtained by 20% w/v S/L ratio, 4N H(2)SO(4) concentration and 90°C. Yttrium and calcium yields are nearly 85% and 5%, respectively. The analysis of variance shows that acid concentration alone and interaction between acid and pulp density have a significant positive effect on yttrium solubilization for both HCl and H(2)SO(4) medium. Two models are empirically developed to estimate yttrium and calcium concentration during leaching. Precipitation tests demonstrate that at least the stoichiometric amount of oxalic acid is necessary to recover yttrium efficiently and a pure yttrium oxalate n-hydrate can be produced (99% grade). The process is economically feasible if other components of the fluorescent lamps (glass, ferrous and non-ferrous scraps) are recovered after the equipment dismantling and valorized, besides the cost that is usually paid to recycling companies for collection, treatment or final disposal of such fluorescent powders.     

Effluent impact assessment using microarray-based analysis in common carp: a systems toxicology approach

Effluents are a main source of direct and continuous input of pollutants to the aquatic environment, and can cause ecotoxicological effects at different levels of biological organization. Since gene expression responses represent the primary interaction site between environmental contaminants and biota, they provide essential clues to understand how chemical exposure can affect organismal health. The aim of the present study was to investigate the applicability of a microarray approach for unraveling modes of action of whole effluent toxicity and impact assessment. A chronic toxicity test with common carp (Cyprinus carpio) was conducted where fish were exposed to a control and 100% effluent for 21 days under flow-through conditions. Microarray analysis revealed that effluent treatment mainly affected molecular pathways associated with the energy balance of the fish, including changes in carbohydrate and lipid metabolism, as well as digestive enzyme activity. These gene expression responses were in clear agreement with, and provided additional mechanistic information on various cellular and higher level effects observed for the same effluent. Our results demonstrate the benefit of toxicogenomic tools in a “systems toxicology” approach, involving the integration of adverse effects of chemicals and stressors across multiple levels of biological complexity.     

Biodiversity of marine sessile epifauna at an Aegean island subject to hydrothermal activity: Milos, eastern Mediterranean Sea

Sessile macroepifauna was sampled at six rocky sites between 2 and 90 m depth with a number of different methods involving both underwater photography and collection of specimens. A total of 212 species (or varieties) were identified, belonging to seven higher taxa: poriferans (24 species), cnidarians (32), molluscs (8), serpuloidean polychaetes (33), bryozoans (90), brachiopods (4) and ascidians (21). The combined use of a varied array of sampling methods was effective in obtaining a rich faunal inventory. Deep and offshore sites tended to be richer in species than shallow and inshore sites. In all cases species richness was higher at sites closest to hydrothermal vents on the sea floor. Although there are no comparable inventories of marine sessile epifauna in the Aegean, the high number of species found, with a relatively low sampling effort in a restricted area, indicates that the marine biodiversity of this sea is not as low as traditionally believed. Received: 20 January 1999 / Accepted: 25 August 1999     

Contaminated sites: the Canadian situation in an international context.

Over the last 2 decades, policy-makers have been giving increasing attention to the remediation and redevelopment of contaminated sites, especially those located in urban areas commonly referred to as brownfields. Traditionally, private developers have tended to ignore these sites on account of a series of obstacles of a structural-political nature, including variability in regulatory processes, lack of information on soil quality, impractical clean up standards, fear of liability, and limited funding resources for clean ups. This paper examines the types of policy-making measures that are currently being taken in Canada to overcome these obstacles, comparing them to those being taken in the US and Europe. It is argued that the contaminated site-related policies and programs employed to overcome each obstacle, both within Canada and internationally, are converging in style and content as governments are becoming more aware of the types of costs and risks they must share in order to solve the problem effectively. It is also argued that this trend is unfolding in a relatively predictable way, and that policy-making in Canada is evolving more slowly than it is in the other jurisdictions examined.     

Empowered to lead: the role of psychological empowerment in leadership

This study examines the relationship between psychological empowerment and leadership. Empowered supervisors are hypothesized to be innovative, upward influencing, and inspirational and less focused on monitoring to maintain the status quo. Tested on a sample of mid‐level supervisors from a Fortune 500 organization, the hypotheses were largely supported. Supervisors who reported higher levels of empowerment were seen by their subordinates as more innovative, upward influencing, and inspirational. No relationship was found between supervisory empowerment and monitoring behaviours. Implications for theory and practice are discussed, and future research directions are suggested. Copyright © 1999 John Wiley & Sons, Ltd.     

基于贝叶斯公式的湖泊富营养化随机评价方法及其验证

为了准确评价湖泊所处的营养状态,进而为湖泊富营养化的防治提供科学依据,提出了基于贝叶斯公式的湖泊富营养化随机评价方法。该法通过计算单个水质指标属于某个评价级别的概率,由最大似然分类原则确定单个水质指标的评价级别,并采用加权平均法推求湖泊富营养化多个水质指标的综合评价级别,具有方法简单、计算工作量小的特点。经全国30个湖泊实测水质资料的验证,随机评价方法与模糊评价方法和灰色评价方法相比较,有29个湖泊评价结果的差异小于等于一个级别,其比例为96.6％,说明这三种富营养化评价方法的计算精度相当。根据各项评价指标与叶绿素的相关系数,计算各项水质指标在富营养化评价中所占权重的方法,适用于浮游植物型湖泊,如果采取等权重方法,则适用于任何类型的湖泊。确定湖泊富营养化评价的水质指标个数和种类的选择具有不确定性,确定湖泊富营养化的评价级别和各个级别对应的水质标准浓度也具有不确定性,因此湖泊富营养化的评价方法具有不确定性。应采用多种途径对湖泊富营养化的评价方法进行研究,并取长补短,使评价结果更趋合理。     

Job characteristics and employee well-being: a test of Warr's Vitamin Model in health care workers using structural equation modelling

Warr's (1987) Vitamin Model was investigated in a representative sample of 1437 Dutch health care workers (i.e. nurses and nurses' aides). According to this model, it was hypothesized that three job characteristics (i.e. job demands, job autonomy, and workplace social support) are curvilinearly related with three key indicators of employee well-being (i.e. job satisfaction, job-related anxiety, and emotional exhaustion). Structural equation modelling (LISREL 8) was employed to test the comprehensive Vitamin Model. The results showed that the fit of the non-linear model is superior to that of the linear model. Except for the relationship between job autonomy and emotional exhaustion, the curvilinear relationships followed the predicted U-shaped or inverted U-shaped curvilinear pattern. Moreover, it appeared that the three job characteristics are differentially related with various indicators of employee well-being. In conclusion, this study partially supports the assertion of the Vitamin Model that non-linear relationships exist between job characteristics and employee well-being. © 1998 John Wiley & Sons, Ltd.     

水溶液中氯代烷烃的催化还原脱氯研究

研究了氯代甲烷系列和氯代乙烷系列的各种氯代烷烃在铁、铜二相金属体系中的还原脱氯反应,分析了氯代有机物结构性质对还原脱氯反应的影响和规律性,探讨了氯代烷烃在金属还原作用下的还原脱氯机理．     

Quantitative Ethnobotany in an Atlantic Forest Fragment of Northeastern Brazil – Implications to Conservation

Two new methods for assessing temporal trends in stream-solute concentrations at specific streamflow ranges were applied to long (40 to 50-year) but sparse (bi-weekly to quarterly sampling) stream-water quality data collected at three forested mesoscale basins along an atmospheric deposition gradient in the northeastern United States (one in north-central Pennsylvania, one in southeastern New York, and one in eastern Maine). The three data sets span the period since the implementation of the Clean Air Act in 1970 and its subsequent amendments.Declining sulfate (O ₄ ^2-) trends since the mid 1960s were identified for all 3 rivers by one or more of the 4 methods of trend detection used. Flow-specific trends were assessed by segmenting the data sets into 3-year and 6-year blocks, then determining concentration-discharge relationships for each block. Declining sulfate (O ₄ ^2-) trends at median flow were similar to trends determined using a Seasonal Kendall Tau test and Sen slope estimator. The trend of declining O ₄ ^2- concentrations differed at high, median and low flow since the mid 1980s at YWC and NR, and at high and low flow at WR, but the trends leveled or reversed at high flow from 1999 through 2002. Trends for the period of record at high flows were similar to medium- and low-flow trends for Ca²⁺+ Mg²⁺ concentrations at WR, non-significant at YWC, and were more negative at low flow than at high flow at NR; trends in nitrate (NO₃ ^-), and alkalinity (ALK) concentrations were different at different flow conditions, and in ways that are consistent with the hydrology and deposition history at each watershed. Quarterly sampling is adequate for assessing average-flow trends in the chemical parameters assessed over long time periods (∼decades). However, with even a modest effort at sampling a range of flow conditions within each year, trends at specified flows for constituents with strong concentration-discharge relationships can be evaluated and may allow early detection of ecosystem response to climate change and pollution management strategies.