A spatiotemporal model for predicting grain aphid population dynamics and optimizing insecticide sprays at the scale of continental France

We expose here a detailed spatially explicit model of aphid population dynamics at the scale of a whole country (Metropolitan France). It is based on convection–diffusion-reaction equations, driven by abiotic and biotic factors. The target species is the grain aphid, Sitobion avenae F., considering both its winged and apterous morphs. In this preliminary work, simulations for year 2004 (an outbreak case) produced realistic aphid densities, and showed that both spatial and temporal S. avenae population dynamics can be represented as an irregular wave of population peak densities from southwest to northeast of the country, driven by gradients or differences in temperature, wheat phenology, and wheat surfaces. This wave pattern fits well to our knowledge of S. avenae phenology. The effects of three insecticide spray regimes were simulated in five different sites and showed that insecticide sprays were ineffective in terms of yield increase after wheat flowering. After suitable validation, which will require some further years of observations, the model will be used to forecast aphid densities in real time at any date or growth stage of the crop anywhere in the country. It will be the backbone of a decision support system, forecasting yield losses at the level of a field. The model intends then to complete the punctual forecasting provided by older models by a comprehensive spatial view on a large area and leads to the diminution of insecticide sprayings in wheat crops.     

Mutagenicity of diesel engine exhaust in the Ames / Salmonella assay using a direct exposure method

The aim of this study was to investigate the potential mutagenic activity of diesel engine exhaust in the Ames/Salmonella assay using a direct aerosol exposure system. So, TA 98 and TA 100 strains, with or without added S9 mix, were exposed to diesel emissions after varying degrees of filtration. Variants of these two strains, deficient in nitroreductase (TA 98NR and TA 100NR) or over-expressing O-Acetyl Transferase (YG 1024 and YG 1029), were also exposed to total (unfiltered) diesel exhaust to highlight the putative mutagenicity of any nitro-PAHs present in these emissions. Mutagenic activity of the diesel exhaust was demonstrated on Salmonella typhimurium, strains TA 100 and variants TA 100 NR and YG1029. The use of a particle filter did not modify the genotoxicity of the diesel emissions, indicating a major contribution of the gas phase to the mutagenicity of these diesel emissions. The prominent role of the particulate-associated nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) claimed by some authors working on diesel exhaust organic extracts was not confirmed by our results with native diesel exhaust exposure. Our results show that the gas phase is potentially more mutagenic than the particles alone.     

Development of a Specific Anti-capsid Antibody- and Magnetic Bead-Based Immunoassay to Detect Human Norovirus Particles in Stool Samples and Spiked Mussels via Flow Cytometry

Food and Environmental Virology - Human noroviruses impose a considerable health burden globally. Here, a flow cytometry approach designed for their detection in biological waste and food samples...     

Investigating the metal contamination status from recycling e-waste sites from Dakar,Senegal

Environmental Science and Pollution Research - In Senegal, processes employed for recycling e-wastes result in release of so-called heavy metals in the environment. In this study, the metal...     

Heat waves and health risks in the northern part of Senegal: analysing the distribution of temperature-related diseases and associated risk factors

Environmental Science and Pollution Research - The Sahelian zone of Senegal experienced heat waves in the previous decades, such as 2013, 2016 and 2018 that were characterised by temperatures...     

Resilience from the ground up: how are local resilience perceptions and global frameworks aligned?

Numerous resilience measurement frameworks for climate programmes have emerged over the past decade to operationalise the concept and aggregate results within and between programmes. Proxies of resilience, including subjective measures using perception data, have been proposed to measure resilience, but there is limited evidence on their validity and use for policy and practice. This article draws on research on the Decentralising Climate Funds project of the Building Resilience and Adaptation to Climate Extremes and Disasters programme, which supports communities in Mali and Senegal to improve climate resilience through locally controlled adaptation funds. It explores attributes of resilience from this bottom‐up perspective to assess its predictors and alignment with food security, as a proxy of well‐being. We find different patterns when comparing resilience and the well‐being proxy, illustrating that the interplay between the two is still unclear. Results also point to the importance of contextualising resilience, raising implications for aggregating results.     

3D geometric structures and biological activity: Application to microbial soil organic matter decomposition in pore space

During the past 10 years, soil scientists have started to use 3D Computed Tomography in order to gain a clearer understanding of the geometry of soil structure and its relationships with soil properties. We propose a geometric model for the 3D representation of pore space and a practical method for its computation. Our basic idea consists in representing pore space using a minimal set of maximal balls (Delaunay spheres) recovering the shape skeleton. In this representation, each ball could be considered as a maximal local cavity corresponding to the “intuitive” notion of a pore as described in the literature. The space segmentation induced by the network of balls (pores) was then used to spatialize biological dynamics. Organic matter and microbial decomposers were distributed within the balls (pores). A valuated graph representing the pore network, organic matter and distribution of micro-organisms was then defined. Microbial soil organic matter decomposition was simulated by updating this valuated graph. The method was implemented and tested using real CT images. The model produced realistic simulated results when compared with data in the literature in terms of the water retention curve and carbon mineralization. A decrease in water pressure decreased carbon mineralization, which is also in accordance with findings in the literature. From our results we showed that the influence of water pressure on decomposition is a function of organic matter distribution in the pore space. As far as we know, this is the approach to have linked pore space geometry and biological dynamics in a formal way. Our next goal will be to compare the model with experimental data of decomposition using different soil structures, and to define geometric typologies of pore space shape that can be attached to specific biological and dynamic properties.