Water, Environment and Urban Systems Laboratory

Abstract Climate change is altering thermal stratification in lakes worldwide. Reduction in winter mixing lead to prolonged oxygen depletion, lasting for years to centuries, potentially becoming permanent. Although there is convincing evidence of lake deoxygenation globally, its duration, timing, and impacts over decadal to centennial timescales remain uncertain. Here, we introduce a novel model-data assimilation approach using 150 years of limnological and paleolimnological data to evaluate the anthropogenic impact and future of deep dissolved oxygen in Lake Geneva. We find that climate change has influenced winter mixing, with divergent effects on bottom oxygen concentrations before and after eutrophication. Over centennial timescales, eutrophication, not climate warming, triggered unprecedented bottom-water hypoxia. However, by 2100, climate change will be the main driver of hypoxia in Lake Geneva and similar lakes, even with reduced phosphorus concentrations. With climate change locking in the effects of phosphorus loading on hypoxia, the significance of reducing loading remains intact.

We report the use of efficient visible-light sensitive allyl (QA) and epoxidized (QE) quinizarin derivatives as photoinitiating systems when combined with an appropriate electron donor (methyldiethanol amine, MDEA), an electron acceptor (iodonium salt, Iod), or a H donor (thiol derivative), for free-radical photopolymerization (FRP), cationic photopolymerization (CP), and a thiol–ene process. These systems have demonstrated excellent initiating properties under air or in laminated conditions under visible-light irradiation (LEDs@405, 455, and 470 nm or Xe lamp) for FRP, CP, or the thiol–ene process and appear more efficient than the well-known camphorquinone-based photoinitiating systems. As highlighted by electron paramagnetic resonance (EPR) and laser flash photolysis experiments, QA (or QE) acts either as an electron donor via a photoinduced electron transfer pathway with Iod or as a proton/proton-coupled electron transfer promoter with MDEA or a thiol derivative. Two types of interpenetrated polymer n...

Inadequate urban waste management in Cote d’Ivoire is the heavy metal source in soils used to produce vegetables. This represents a potential risk of food contamination. In order to find an efficient technique for soils depollution before their use in agriculture, an experimental study had demonstrated the ability of species of Acacia (mangium, auriculiformis and crassicarpa) to extract heavy metals from landfill soils. This work was undertaken to determine rhizosphere processes controlling Acacia growth in polluted soil. An experiment was carried out in hydroponic culture and on thin layer of landfill polluted soil during 3 months. During this experiment, growth parameters, soil chemical properties, heavy metal contents in soil (total and various fractions) and in plants were measured at the end of experiment. Results show that plant growth is related to the development of strategies in root zone. Plants released protons in their rhizosphere and lowering the redox potential, especially under Acacia crassicarpa, which stored the most level of heavy metal in in biomass. The other species produce organic acids allowing plants to grow with high biomass in soil with high content of heavy metal. Acacia crassicarpa is therefore the species better suited for depollution of landfill soil.

Land-based macroplastic is considered one of the major sources of marine plastic debris. However, estimations of plastic emission from rivers into the oceans remain scarce and uncertain, mainly due to a severe lack of standardized observations. To properly assess global plastic fluxes, detailed information on spatiotemporal variation in river plastic quantities and composition are urgently needed. In this paper, we present a new methodology to characterize riverine macroplastic dynamics. The proposed methodology was applied to estimate the plastic emission from the Saigon River, Vietnam. During a two-week period, hourly cross-sectional profiles of plastic transport were made across the river width. Simultaneously, sub-hourly samples were taken to determine the weight, size and composition of riverine macroplastics (>5cm). Finally, extrapolation of the observations based on available hydrological data yielded new estimates of daily, monthly and annual macroplastic emission into the ocean. Our results suggest that plastic emissions from the Saigon River are up to 4 times higher than previously estimated. Importantly, our flexible methodology can be adapted to local hydrological circumstances and data availability, thus enabling a consistent characterization of macroplastic dynamics in rivers worldwide. Such data will provide crucial knowledge for the optimization of future mediation and recycling efforts.

Although the interaction between phages and bacteria has already been well described, it only recently emerged that human viruses also interact with bacteria in the mammalian gut. We studied whether this interaction could occur in tap water and thus confer enteric viruses protection against temperature and the classical disinfection treatments used in drinking water production. We demonstrated that the addition of lipopolysaccharide or peptidoglycan of bacterial origin to enterovirus provides thermal protection through stabilization of the viral capsid. This interaction plays a role when viruses are exposed to disinfection that targets the capsid, but less so when the virus genome is directly targeted. The interaction seems to be serotype-specific, suggesting that the capsid protein sequence could be important. The protection is linked to a direct association between viral particles and bacterial compounds as observed by microscopy. These results show that bacterial compounds present in the environment can affect virus inactivation.

The concept of urban resilience has taken a leading edge by incorporating the multiscalar interactions within an urban system, revealing the short- and long-term impacts, spatial dependencies, and inequalities. The issue now is to enable local authorities and urban stakeholders to grasp and apply the resilience approach. Technical networks and urban services supporting urban development (drinking water supply, public transportation, etc.) are an interesting case study to apply the resilience concept. The urban resilience approach, tested with the managers of service provision in the City of Paris, demonstrates the effectiveness of integration and collaboration. First, an autodiagnosis realized with each manager identifies the service dependencies and its capacity for continuous operation in case of disturbance. Then workshops raise manager awareness of their interdependencies and feed the discussion toward technical and organizational solutions in an integrated approach. This macroscopic analysis is then completed by a territorial assessment of urban service resilience. In doing so, the spatial and temporal dimensions emphasize gaps but also margins of manoeuver in managing resilient urban services. Our results show that manager strategies can be focused on protection, adaptation, or recovery of their service. However, these are sometimes contradictory and threaten the resilience of the whole system. Indeed, in highlighting the different strategies set up by managers, the region’s resilience can be discussed at different scales: the urban service, the system of urban services, the City of Paris, and the Parisian metropolis. Then we emphasize the difficulties in applying the resilience concept and suggest solutions to improve the conditions for urban resilience and sustainability.

Radio Frequency IDentification (RFID) is an advanced tracking technology that can be used to study the spatial organization of individual’s spatio-temporal activity. The aim of this work is firstly to build a new RFID-based autonomous system which can follow individuals’ spatio-temporal activity, a tool not currently available. Secondly, the authors aim to develop new tools for automatic data mining. In this paper, they study how to transform these data to investigate the division of labor, the intra-colonial cooperation and conflict in an ant colony. They also develop a new unsupervised learning data mining method (DS2L-SOM: Density based Simultaneous Two-Level - Self Organizing Map) to find homogeneous clusters (i.e., sets of individual which share a similar behavior). According to the experimental results, this method is very fast and efficient. It also allows a very useful visualization of the results.