Climate impact studies of sediment transport on the Adriatic coastal zone

The study of the impact of climate change on the environment has been based, until very recently, on an global approach, whose interest from a local point of view is very limited. This thesis, on the contrary, has treated the study of the impact of climate change in the Adriatic Sea basin following a twofold strategy of regionalization and integration of numerical models in order to reproduce the present and future scenarios of the system through a more and more realistic and solid approach. In particular the focus of the study was on the impact on the physical environment and on the sediment transport in the basin. This latter is a very new and original issue, to our knowledge still uninvestigated. The study case of the coastal area of Montenegro was particularly studied, since it is characterized by an important supply of sediment through the Buna/Bojana river, second most important in the Adriatic basin in terms of flow. To do this, a methodology to introduce the tidal processes in a baroclinic primitive equations Ocean General Circulation Model was applied and tidal processes were successfully reproduced in the Adriatic Sea, analyzing also the impacts they have on the mean general circulation, on salt and heat transport and on mixing and stratification of the water column in the different seasons of the year. The new hydrodynamical model has been further coupled with a wave model and with a river and sea sediment transport model, showing good results in the reproduction of sediment transport processes. Finally this complex coupled platform was integrated in the period 2001-2030 under the A1B scenario of IPCC, and the impact of climate change on the physical system and on sediment transport was preliminarily evaluated.

Experimental and numerical analyses about the efficiency of flow through devices for the sediment controll in urban runoff

As land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, particle size distribution and specific gravity). The efficiency in terms of particles retained has been evaluated as a function of influent flow rate and particles characteristics; results have been compared to efficiency evaluated applying an overflow rate model. Furthermore the role of particles settling velocity in efficiency determination has been investigated. After the experimental runs on the gully pot, a standard full-scale model of an hydrodynamic separator (HS) has been tested under unsteady influent flow rate condition, and constant solid concentration at the input. The results presented in this study illustrate that particle separation efficiency of the unit is predominately influenced by operating flow rate, which strongly affects the particles and hydraulic residence time of the system. The efficiency data have been compared to results obtained from a modified overflow rate model; moreover the residence time distribution has been experimentally determined through tracer analyses for several steady flow rates. Finally three testing experiments have been performed for two different configurations of a full-scale model of a clarifier (linear and crenulated) under unsteady influent flow rate condition, and constant solid concentration at the input. The results illustrate that particle separation efficiency of the unit is predominately influenced by the configuration of the unit itself. Turbidity measures have been used to compare turbidity with the suspended sediments concentration, in order to find a correlation between these two values, which can allow to have a measure of the sediments concentration simply installing a turbidity probe.

Water, sediment and soil physicochemical interactions in freshwater, brackish and saline systems

The physicochemical interactions between water, sediment and soil deeply influence the formation and development of the ecosystem. In this research, different freshwater, brackish and saline subaqueous environments of Northern Italy were chosen as study area to investigate the physicochemical processes which occur at the interface between water and sediments, as well as the effects of soil submergence on ecosystem development. In the freshwater system of the Reno river basin, the main purpose was to define the heavy metals hazard in water and sediments of natural and artificial water courses. Heavy metals partitioning and speciation allowed to assess the environmental risk linked to the critical action of dredging canal sediments, for the maintenance of the hydraulic safety of plain lands. In addition, some bioremediation techniques were experimented for protecting sediments from heavy metals contamination, and for giving an answer to the problem of sediments management. In the brackish system of S. Vitale park, the development of hydromorphic and subaqueous soils was investigated. The study of soil profiles highlighted the presence of a soil continuum among pedons subjected to different saturation degrees. This investigation allowed to the identification of both morphological and physicochemical indicators, which characterize the formation of subaqueous soils and describe the soil hydromorphism in transitional soil systems. In the saline system of Grado lagoon, an ecosystem approach was used to define the role of water oscillation in soil characterization and plants colonization. This study highlighted the close relationship and the mutual influence of soil submergence and aeration, tide oscillation and vegetation cover, on the soil development. In view of climate change, this study contribute to understand and suppose how soil and landscape could evolve. However, a complete evaluation of hydromorphic soil functionality will be achieved only involving physiological and biochemical expertise in these kind of studies.

Verhalten von Recycling-Materialien in der Umwelt : Labor- und Feldversuche

Im Baugewerbe fallen jährlich mehrere Millionen Tonnen an Baureststoffen an, die nach erfolgter Aufbereitung als Recycling-Baustoffe erneut verwendet werden können. Allerdings besteht Unklarheit hinsichtlich der Stofffreisetzung aus Recycling-Materialien sowie der Parameter, die zur Beurteilung im Wesentlichen heranzuziehen sind. Des Weiteren gilt es der Frage nachzugehen, welche Laborversuche eine realistische Prognose zum Stoffaustrag unter Freilandbedingungen ermöglichen. Ein Ergebnisvergleich aus Feld- und Laborversuchen mit Recycling-Materialien zeigt, dass weder Ammoniumnitrat-Extraktion, pH-stat Versuch noch S4- und Modifizierter S4-Test genauere Prognosen zum Stoffaustrag unter Freilandbedingungen ermöglichen. Mit einem Langzeit-Standtest sowie Schüttelversuchen mit unterschiedlichen Wasser/Feststoff-Verhältnissen lässt sich der Einfluss durch verschiedene Korngrößen sowie Materialabrieb besser kontrollieren. Diese Versuchskombination erlaubt Rückschlüsse auf die Löslichkeit und Verfügbarkeit von Stoffen in den Recycling-Materialien. Die Ergebnisse aus Säulenversuchen weisen auf eine gute Vergleichbarkeit mit den Feldversuchen hin, was sich an denselben vorherrschenden Prozessen bei der Freisetzung für eine Reihe von Stoffen zeigt. Bei mehreren Stoffen treten ähnliche Konzen-trationshöchstwerte bei Säulen- und Feldversuch auf, ebenso zeigt der Vergleich aufsummierter Massenanteile für den Säulenversuch, dass bei einer Reihe von Stoffen eine grobe Abschätzbarkeit für eine Langzeitprognose unter Freilandbedingungen existiert. Als wesentliche Parameter für die Stofffreisetzung aus den Recycling-Materialien sind neben CO2-Einfluss und pH-Wert ebenfalls Temperatureinfluss, Material-Heterogenität sowie einzusetzende Korngröße anzusehen.

Recycling of end of life concrete fines (0 - 4 mm) into silica and cement

The purpose of this work is to find a methodology in order to make possible the recycling of fines (0 - 4 mm) in the Construction and Demolition Waste (CDW) process. At the moment this fraction is a not desired by-product: it has high contaminant content, it has to be separated from the coarse fraction, because of its high water absorption which can affect the properties of the concrete. In fact, in some countries the use of fines recycled aggregates is highly restricted or even banned. This work is placed inside the European project C2CA (from Concrete to Cement and Clean Aggregates) and it has been held in the Faculty of Civil Engineering and Geosciences of the Technical University of Delft, in particular, in the laboratory of Resources And Recycling. This research proposes some procedures in order to close the loop of the entire recycling process. After the classification done by ADR (Advanced Dry Recovery) the two fractions "airknife" and "rotor" (that together constitute the fraction 0 - 4 mm) are inserted in a new machine that works at high temperatures. The temperatures analysed in this research are 600 °C and 750 °C, cause at that temperature it is supposed that the cement bounds become very weak. The final goal is "to clean" the coarse fraction (0,250 - 4 mm) from the cement still attached to the sand and try to concentrate the cement paste in the fraction 0 - 0,250 mm. This new set-up is able to dry the material in very few seconds, divide it into two fractions (the coarse one and the fine one) thanks to the air and increase the amount of fines (0 - 0,250 mm) promoting the attrition between the particles through a vibration device. The coarse fraction is then processed in a ball mill in order to improve the result and reach the final goal. Thanks to the high temperature it is possible to markedly reduce the milling time. The sand 0 - 2 mm, after being heated and milled is used to replace 100% of norm sand in mortar production. The results are very promising: the mortar made with recycled sand reaches an early strength, in fact the increment with respect to the mortar made with norm sand is 20% after three days and 7% after seven days. With this research it has been demonstrated that once the temperature is increased it is possible to obtain a clean coarse fraction (0,250 - 4 mm), free from cement paste that is concentrated in the fine fraction 0 - 0,250 mm. The milling time and the drying time can be largely reduced. The recycled sand shows better performance in terms of mechanical properties with respect to the natural one.

Recycling the city: a sustainable planning framework to reduce, reuse and recycle urban residual spaces

Cities are key locations where Sustainability needs to be addressed at all levels, as land is a finite resource. However, not all urban spaces are exploited at best, and land developers often evaluate unused, misused, or poorly-designed urban portions as impracticable constraints. Further, public authorities lose the challenge to enable and turn these urban spaces into valuable opportunities where Sustainable Urban Development may flourish. Arguing that these spatial elements are at the centre of SUD, the paper elaborates a prototype in the form of a conceptual strategic planning framework, committed to an effective recycling of the city spaces using a flexible and multidisciplinary approach. Firstly, the research focuses upon a broad review of Sustainability literature, highlighting established principles and guidelines, building a sound theoretical base for the new concept. Hence, it investigates origins, identifies and congruently suggests a definition, characterisation and classification for urban “R-Spaces”. Secondly, formal, informal and temporary fitting functions are analysed and inserted into a portfolio meant to enhance adaptability and enlarge the choices for the on-site interventions. Thirdly, the study outlines ideal quality requirements for a sustainable planning process. Then, findings are condensed in the proposal, which is articulated in the individuation of tools, actors, plans, processes and strategies. Afterwards, the prototype is tested upon case studies: Solar Community (Casalecchio di Reno, Bologna) and Hyllie Sustainable City Project, the latter developed via an international workshop (ACSI-Camp, Malmö, Sweden). Besides, the qualitative results suggest, inter alia, the need to right-size spatial interventions, separate structural and operative actors, involve synergies’ multipliers and intermediaries (e.g. entrepreneurial HUBs, innovation agencies, cluster organisations…), maintain stakeholders’ diversity and create a circular process open for new participants. Finally, the paper speculates upon a transfer of the Swedish case study to Italy, and then indicates desirable future researches to favour the prototype implementation.

Long-term effects of watershed management on surface runoff and sediment loss in the Ethiopian Highlands

Data on rainfall, runoff and sediment loss from different land use types have been collected by the Soil Conservation Research Programme in seven small catchments (73-673 hectares) throughout the Ethiopian Highlands since the early 1980s. Monitoring was carried out on a storm-to-storm basis for extended periods of 10-20 years, and the data are analysed here to assess long-term effects of changes. Soil and water conservation technologies were introduced in the early years in the catchments in view of their capacity to reduce runoff and sediment yield. Results indicate that rainfall did not substantially change over the observation periods. Land use changes and land degradation, however, altered runoff, as shown by the data from small test plots (30 m2), which were not altered by conservation measures during the monitoring periods. Sediment delivery from the catchments may have decreased due to soil and water conservation, while runoff rates did not change significantly. Extrapolation of the results in the highlands, however, showed that expansion of cultivated and grazing land induced by population growth may have increased the overall surface runoff. Watershed management in the catchments, finally, had beneficial effects on ecosystem services by reducing soil erosion, restoring soil fertility, enhancing agricultural production, and maintaining overall runoff to the benefit of lowland areas and neighbouring countries.

Examining the Justification for Residential Recycling

Municipalities in the United States have for the past two decades initiated two policies to reduce residential solid waste generation by increasing recycling. The first policy, implemented in over 4,000 municipalities in the United States, requires households to pay a fee for each unit of garbage presented at the curb for collection. The second policy, initiated in 8,875 municipalities, subsidizes household recycling efforts by providing free curbside collection of certain recyclable materials. Both initiatives serve as examples of incentive-based environmental policies favored by many economists. But before economists can celebrate this wide-spread adoption of incentive-based environmental policies, further examination reveals that potentially inefficient command and control policies have been more instrumental in promoting recycling than might be commonly known. This article examines the empirical lessons gained from studying twenty years of solid waste policy in the United States and argues for the replacement of several state recycling mandates with a system of state and/or national landfill taxes.

Explaining the Growth in Municipal Recycling Programs: The Role of Market and Non-Market Factors

The implementation of thousands of municipal recycling programs in the United States has increased recycling’s portion of solid waste from 10% to 30% over the past decade. But the lack of accurate data has spurred a debate over whether the growth in recycling can be attributed to market or nonmarket factors. To address this issue, this article conducts a benefit-cost analysis of a municipal recycling program. Results suggest recycling is costly. So why, then, does it remain popular? This article suggests that local governments could be responding to households that perceive a benefit from recycling services. These benefits are estimated with a contingent valuation survey.

Optimal Solid Waste Policy with Centralized Recycling Opportunities

Economic models have demonstrated the efficiency of curbside collection taxes. This paper demonstrates that such efficiencies disappear in economies with centralized recycling options - where recyclable materials can be removed from the waste stream either by households or at a centralized recycling facility. In such economies a curbside garbage tax not only fails to encourage the centralized recycler to internalize the external costs of waste disposal, but introduces inefficiencies to the cost-minimizing mix of household and centralized recycling efforts. The optimal waste policy is a tax assessed further downstream at the landfill rather than at the curb.

The Costs of Municipal Curbside Recycling and Waste Collection

This paper estimates cost functions for both municipal solid waste collection and disposal services and curbside recycling programs. Cost data are obtained from a national survey of randomly selected municipalities. Results suggest, perhaps unsurprisingly, that both marginal and average costs of recycling systems exceed those of waste collection and disposal systems. Economies of scale are estimated for all observed quantities of waste collection and disposal. Economies of scale for recycling disappear at high levels of recycling - marginal and average cost curves for recycling take on the usual U-shape. Waste and recycling costs are also estimated as functions of factor costs and program attributes.