Choice set formation for outdoor destinations: The role of motivations and preference discrimination in site selection for the management of public expenditures on protected areas

Effective public expenditure currently dominates the management focus of many protected areas. This calls for explicit modeling of constraints and motivations that, respectively, obstruct and stimulate visits to selected outdoor destinations. Choice set formation is the result of screening and/or inclusion of specific sites (alternatives) to form the set of sites considered in real choices. Evidence shows that the omission of a structural representation of choice set formation is harmful to econometric inference. Yet, the literature has largely ignored the underlying behavioral phenomenon. We show, using a discrete choice experiment involving selection among seven recreational sites in an Italian national park, that choice set formation is behaviorally relevant, even after controlling for preference discrimination. Motivations (why visit?) are important determinants of preliminary site screening for choice set inclusion, as well as site selection, justifying the additional value of such modeling extension.     

Evaluation of potential genotoxicity of five food dyes using the somatic mutation and recombination test

In this study, different concentrations of five food dyes (amaranth, patent blue, carminic acid, indigotine and erythrosine) have been evaluated for genotoxicity in the Somatic Mutation and Recombination Test (SMART) of Drosophila melanogaster. Standard cross was used in the experiment. Larvae including two linked recessive wing hair mutations were chronically fed at different concentrations of the test compounds in standard Drosophila Instant Medium. Feeding ended with pupation of the surviving larvae. Wings of the emerging adult flies were scored for the presence of spots of mutant cells which can result from either somatic mutation or somatic recombination. For the evaluation of genotoxic effects, the frequencies of spots per wing in the treated series were compared to the control group, which was distilled water. The present study shows that carminic acid and indigotine demonstrated negative results while erythrosine demonstrated inconclusive results. In addition 25 mg mL⁻¹ concentration of patent blue and 12.5, 25 and 50 mg mL⁻¹ concentrations of amaranth demonstrated positive results in the SMART.     

软弱围岩节理性质对隧道塌方范围影响研究*

为探究节理岩体在节理扩展-节理破坏-岩体失稳过程中的力学特性变化及变形破坏规律,采用块体离散元软件3DEC进行数值模拟,对节理岩体中隧道开挖后围岩的应力变形状态进行研究。结果表明:法向刚度较小时,可能造成的塌方范围大,法向刚度较大时,造成的塌方范围小;节理剪切刚度对隧道塌方范围的影响较小;节理内摩擦角变化对断层塌落体及上覆未塌落体范围的影响较小。     

负载TiO_2浮石对污水处理厂二沉池出水的矿化与灭菌研究

城市污水处理厂第二沉淀池出水的污染物浓度较低,经过矿化及灭菌等深度处理后可以同用,从而减轻对淡水资源的需求.本实验采用溶胶-凝胶法制备了负载TiO2的浮石光催化剂,对城市污水处理厂第二沉淀池出水进行了矿化及灭菌处理研究.采用低压汞灯对处理水样照射2 h,有机物降解率可以达到50%,灭菌效率达到100%.处理后的水可以作为农作物灌溉、城市绿化和娱乐用水.负载在浮石表面的TiO2薄膜经过10次的光催化循环实验后,没有明显破损,可以再次循环使用.TiO2浮石具有质轻、机械性能好和价格低等优点,该方法处理废水的适用浓度低,可以广泛应用于微污染水和城市污水处理厂出水的深度处理.     

Survey of trace metals in drinking water supplied to rural populations in the eastern Llanos of Venezuela

To ascertain the water quality for human consumption, chemical parameters such as pH, conductivity and total dissolved calcium, magnesium, iron, aluminum, zinc, copper and manganese were measured during four sampling periods (November 2002; March, May and July 2003) in drinking water wells which supply several forest camps and rural populations located in the eastern Llanos of Venezuela. Copper levels in drinking water in November 2002 were found to be significantly higher (P<0.05) than the other assessed periods. Temporal variations of the other parameters considered were not statistically significant. Calcium and magnesium concentrations were found to be extremely low (mean concentration+/-S.D. of 0.27+/-0.25mg/l for Ca and 0.219+/-0.118 for Mg) during the four sampling periods, probably because of the carbonate bearing scarcity in the soils lithic component. The rest of the metals complied with the Venezuelan and International guidelines of quality criteria for drinking water.     

How do long-term development and periodical changes of river-floodplain systems affect the fate of contaminants? Results from European rivers

In many densely populated areas, riverine floodplains have been strongly impacted and degraded by river channelization and flood protection dikes. Floodplains act as buffers for flood water and as filters for nutrients and pollutants carried with river water and sediment from upstream source areas. Based on results of the EU-funded “AquaTerra” project (2004-2009), we analyze changes in the dynamics of European river-floodplain systems over different temporal scales and assess their effects on contaminant behaviour and ecosystem functioning. We find that human-induced changes in the hydrologic regime of rivers have direct and severe consequences on nutrient cycling and contaminant retention in adjacent floodplains. We point out the complex interactions of contaminants with nutrient availability and other physico-chemical characteristics (pH, organic matter) in determining ecotoxicity and habitat quality, and draw conclusions for improved floodplain management.     

负载TiO2浮石对污水处理厂二沉池出水的矿化与灭菌研究

城市污水处理厂第二沉淀池出水的污染物浓度较低,经过矿化及灭菌等深度处理后可以回用,从而减轻对淡水资源的需求。本实验采用溶胶凝胶法制备了负载TiO₂的浮石光催化剂,对城市污水处理厂第二沉淀池出水进行了矿化及灭菌处理研究。采用低压汞灯对处理水样照射2 h,有机物降解率可以达到50%,灭菌效率达到100%。处理后的水可以作为农作物灌溉、城市绿化和娱乐用水。负载在浮石表面的TiO2薄膜经过10次的光催化循环实验后,没有明显破损,可以再次循环使用。TiO₂浮石具有质轻、机械性能好和价格低等优点,该方法处理废水的适用浓度低,可以广泛应用于微污染水和城市污水处理厂出水的深度处理。     

再生水做景观用水使用含氯消毒剂消毒的副产物及安全性

再生水消毒后主要作为城市杂用水利用,消毒副产物及其毒性的研究非常重要.在浓度为 5～8 mg/L 的消毒剂(ClO2、HClO)量下,灭菌率能够达到 100%.2 种消毒体系均产生少量ClO2-、ClO3-和CHCl3,对检验用水生生物未产生毒性.适当的选择消毒剂浓度,控制反应条件,能够实现再生水的安全回用.