Controlled combustion tests and bottom ash analysis using household waste with varying composition

The influence of the co-combustion of household waste with either sewage sludge, shredder fluff, electronic and electrical waste (WEEE) or PVC on the bottom ash quality and content was investigated under controlled laboratory conditions using a pot furnace. This laboratory approach avoids the interpretation problems related to large variations in input waste composition and combustion conditions that are observed in large scale MSW incinerators. The data for metals content, transfer coefficients and leaching values are presented relative to data for a base household waste composition that did not contain any of the added special wastes. The small WEEE invited direct measurement of precious metals content in the ashes, where measurement accuracy is facilitated by using only mobile phone scrap for small WEEE. The analyses were carried out for different particle size ranges that are of relevance to the recyclability of metals and minerals in the ashes. Positive correlations were found between elements content of the input waste and the bottom ashes, and also between increased levels of Cl, Mo and Cu in the input waste and their leaching in the bottom ashes. These correlations indicate that addition of PVC, small WEEE and shredder fluff in input waste can have a negative influence on the quality of the bottom ashes. Enrichment of Au and Ag occurred in the fractions between 0.15 and 6 mm. The precious metals content represents an economically interesting intrinsic value, even when the observed peak values are properly averaged over a larger volume of ashes. Overall, it has been shown that changes in quality and content of bottom ashes may be traced back to the varied input waste composition.     

Constitutive and herbivore‐induced volatiles in pear,alder and hawthorn trees

Summary. Qualitative and quantitative differences among pear cultivars were found in constitutive and Cacopsylla-induced volatiles, depending on experimental treatment of the trees (i.e., uninfested and partly or completely infested by psyllids). Blend differences were also found between pear cultivars and wild-type pear, alder and hawthorn–the latter trees are frequently present in pear orchard hedgerows. ?Interesting differences were found in the presence of methyl salicylate and (E,E)-α-farnesene, two compounds previously found to mediate attraction of predatory bugs towards psyllid-infested pear trees. Methyl salicylate is expressed constitutively and is induced systemically by infestation in the whole plant of all four cultivars. (E,E)-α-farnesene on the other hand showed also systemic induction in Bartlett, NY10355 and Beurré Hardy, but in partially infested Conference trees it was induced locally, only in herbivore-damaged leaves. No methyl salicylate or (E,E)-α-farnesene were identified in honeydew. In field collected headspace samples of alder leaves infested by aphids and leaf beetles we found methyl salicylate but no (E,E)-α-farnesene, whereas in uninfested hawthorn neither were identified. Insight in the variability of damage-related pear volatiles will have important implications for integrated pest management in the field. Received 27 August 2002; accepted 28 November 2002 R1D=" Correspondence to: Petru Scutareanu, e-mail:scuterea@science.uva.nl     

Residential Construction, Land Use and the Environment. Simulations for the Netherlands Using a GIS-Based Land Use Model

The present generation of geographical information systems supports strategic planning processes in several ways. They are able to store, manage and analyse the enormous amount of data needed. Another more output-oriented use is the visualisation of the diversity of locational preferences and perspectives of different interest groups and stakeholders. For the simulation of (more indirect) effects of autonomous or planned developments land use modelling can be applied. A step further is the definition and implementation of a set of indicators that show the impact of land use change on different aspects of space and the environment in order to facilitate the (political) discussions, that are an essential part of strategic planning.This paper focuses on the application of a GIS-based simulation model in the framework of the Fifth National Physical Planning Report in the Netherlands. The simulation model generates future land use in the Netherlands given several growth scenarios and a spatial strategy that comprises both foreseen strategic and autonomous developments. Special attention is paid to residential construction because this is expected to be one of the major driving forces in land use changes. An analysis of residential construction for the period 1980–1995 reveals that residential construction has been relatively concentrated in areas close to existing urban areas. New town policies also played a rather strong role during this period. The presence of natural areas (woods and wetlands) plays a significant though limited role in the choice where to build new dwellings. The simulation results for the year 2020 are used to assess the effects of land use changes for a range of environmental indicators.     

Global and Regional Impacts of Stabilizing Atmospheric CO2

Among the key issues of concern to the Climate Convention is the stabilization of greenhouse gas concentrations and the minimization of impacts to global agriculture, natural ecosystems and economic development. The purpose of this paper is to couple these issues in consistent, integrated scenarios, using the IMAGE 2.0 model as an integrating tool. Scenarios of gradual stabilization of atmospheric CO₂ at 350 and 450 ppm are compared to a baseline of no policy action in which CO₂ concentration increases to 777 ppm. Under the stabilizaton scenarios substantially smaller areas of wheat and millet, as well as nature reserves, are threatened by climate change, especially in temperate regions. The amount of sea level rise is also reduced under the stabilization scenarios. However, climate continues to change under the stabilization scenarios and therefore some ‘residual’ climate impacts occur. Hence the integrated scenarios indicate that stabilizing greenhouse gas concentrations at or slightly above current levels will lessen impacts as compared to baseline levels, but not eliminate them. This revised version was published online in August 2006 with corrections to the Cover Date.     

荷兰环境协议:分担可持续工业发展的责任

工业界与政府共同努力,可以利用合作性协议来达到雄心勃勃的环境质量目标.这样的协议,只要能激励所涉及工业的革新性能力,就会比命令与控制思路更加卓有成效.政府在其颁发许可证时无法要求各公司开展有深远意义的革新,而且规定变革也不属于法规的性质,除非这些变革肯定能实现.各公司对它们自己的技术可能性要比法规当局清楚得多.然而,对于要取得成功的合作性协议来说,工业界需要改变它的传统态度和采用有益于所有各方的环境政策.     

Creation and preservation of vegetation patterns by grazing

Structural patterns of tall stands (“tussock”) and short stands (“lawn”) are observed in grazed vegetation throughout the world. Such structural vegetation diversity influences plant and animal diversity. A possible mechanism for the creation and preservation of such patterns is a positive feedback between grazing and plant palatability. Although some theoretical studies have addressed this point in a non-spatial setting, the spatial consequences of this feedback mechanism on the stability and spatial characteristics of vegetation structure patterns have not been studied.We addressed this issue by analyzing a spatially explicit individual-based plant-grazer simulation model, based on published empirical relations and the assumption of optimal foraging.In the model, the selection by the grazer of short stands (that have a higher energy content and are more palatable) is affected by traveling costs and the spatial organization of swards. Nevertheless, the most selected biomass in this type of short stands was the optimal biomass predicted by cropping and digestion constraints. As a result of the optimal foraging strategy, the grazers displayed Lévy-flight traveling behavior during the simulations with characteristic exponent μ ≈ 2.Patterns of short and tall stands created by grazing were preserved for at least a decade. Even in seasonal habitat, the spatial organization of the patterns remained relatively constant, despite fluctuations in the area of short stands. Heterogeneity of initial vegetation increased heterogeneity of the grazing-induced pattern, but did not affect its stability.The area of short stands that was preserved by grazing scaled with the herbivore mass to the power 0.4 and with the carrying capacity of the vegetation to the power −0.75.Patterns of tall and short stands can be created and perpetuated by optimally grazing ruminants, irrespective of possible underlying soil patterns. The simulations generate predictions for the stability and spatial characteristics of such structural vegetation patterns.     

Increased carbon dioxide availability alters phytoplankton stoichiometry and affects carbon cycling and growth of a marine planktonic herbivore

Rising levels of CO₂ in the atmosphere have led to increased CO₂ concentrations in the oceans. This enhanced carbon availability to the marine primary producers has the potential to change their nutrient stoichiometry, and higher carbon-to-nutrient ratios are expected. As a result, the quality of the primary producers as food for herbivores may change. Here, we present experimental work showing the effect of feeding Rhodomonas salina grown under different pCO₂ (200, 400 and 800 μatm) on the copepod Acartia tonsa. The rate of development of copepodites decreased with increasing CO₂ availability to the algae. The surplus carbon in the algae was excreted by the copepods, with younger stages (copepodites) excreting most of their surplus carbon through respiration and adult copepods excreting surplus carbon mostly as DOC. We consider the possible consequences of different excretory pathways for the ecosystem. A continued increase in the CO₂ availability for primary production, together with changes in the nutrient loading of coastal ecosystems, may cause changes in the trophic links between primary producers and herbivores.