Deciphering the effect of mixed Sphagnum rubellum – Molinia caerulea on litterdecomposition through the 3D fluorescence analysis of Water ExtractableOrganic Matter.

International audienceSphagnum peatlands are experiencing varying perturbations, which jeopardize their ability to storevast amount of carbon. Vegetation change driven by changes in temperature and hydrology as aresult of potential/predicted climate change. Vascular plant percentage covers are expected toincrease. This will lead to changes in the relative proportion of litters reaching the soil (increase ofvascular plant litter). Thus, it implies possible litter mixture effect that did not exist before. The globalaim of this study was to study specific interactions between Sphagnum rubellum (a peat forming moss)and a vascular plant which tends to colonise many Sphagnum peatlands, Molinia caerulea. Field andlaboratory studies have shown that mixing litters of Sphagnum rubellum and Molinia caerulea has asignificant synergistic effect on the decomposition of organic matter (assessed by measuring littermass loss with time). It is not always easy to explain what factors are involved in this effect. Thespecific aim of this study was to investigate the pertinence of analysing the fluorescencecharacteristics of Water Extractable Organic Matter (WEOM) extracted from Sphagnum rubellum andMolinia caerulea litters incubated in monoculture and in mixture with PARAFAC to explain such aneffect. A primary analysis of the 3 main fluorophores showed that compared to the Sphagnum litter,the gamma fluorophore tended to increase with incubation time. This was first interpreted as anincrease of products originating from cell microbial lysis. The gamma fluorophores intensity in theWEOM from the measured mixed litters was lower than the intensity calculated from the litter inmonoculture (additive effect). This suggests that microbial biomass in Molinia caerulea litter, in theexperiment conditions, experiences lethal conditions. Mixing with Sphagnum rubellum litter preventedthis lethal effect. It is proposed that the Sphagnum rubellum litter maintain moisture conditionsfavourable to decomposition of Molinia caerulea litter. Here we present further discussion of theseresults from the PARAFAC analysis of the datase

TRAC, a collaborative computer tool for tracer-test interpretation

Artificial tracer tests are widely used by consulting engineers for demonstrating water circulation, proving the existence of leakage, or estimating groundwater velocity. However, the interpretation of such tests is often very basic, with the result that decision makers and professionals commonly face unreliable results through hasty and empirical interpretation. There is thus an increasing need for a reliable interpretation tool, compatible with the latest operating systems and available in several languages. BRGM, the French Geological Survey, has developed a project together with hydrogeologists from various other organizations to build software assembling several analytical solutions in order to comply with various field contexts. This computer program, called TRAC, is very light and simple, allowing the user to add his own analytical solution if the formula is not yet included. It aims at collaborative improvement by sharing the tool and the solutions. TRAC can be used for interpreting data recovered from a tracer test as well as for simulating the transport of a tracer in the saturated zone (for the time being). Calibration of a site operation is based on considering the hydrodynamic and hydrodispersive features of groundwater flow as well as the amount, nature and injection mode of the artificial tracer. The software is available in French, English and Spanish, and the latest version can be downloaded from the web site http://trac.brgm.f

SNO KARST: A French Network of Observatories for the Multidisciplinary Study of Critical Zone Processes in Karst Watersheds and Aquifers

Karstaquifers and watersheds represent a major source of drinking water around the world. They are also known as complex and often highly vulnerable hydrosystems due to strong surface-groundwater interactions. Improving the understanding of karst functioning is thus a major issue for the efficient management of karst groundwater resources. A comprehensive understanding of the various processes can be achieved only by studying karst systems across a wide range of spatiotemporal scales under different geological, geomorphological, climatic, and soil cover settings. The objective of the French Karst National Observatory Service (SNO KARST) is to supply the international scientific community with appropriate data and tools, with the ambition of (i) facilitating the collection of long-term observations of hydrogeochemical variables in karst, and (ii) promoting knowledge sharing and developing cross-disciplinary research on karst. This paper provides an overview of the monitoring sites and collective achievements, such as the KarstMod modular modeling platform and the PaPRIKa toolbox, of SNO KARST. It also presents the research questions addressed within the framework of this network, along with major research results regarding (i) the hydrological response of karst to climate and anthropogenic changes, (ii) the influence of karst on geochemical balance of watersheds in the critical zone, and (iii) the relationships between the structure and hydrological functioning of karst aquifers and watersheds

Advanced nano-biocomposites based on starch

Starch as a biopolymer directly extracted from nature has received much attention in recent years due to its strong advantages such as low cost, wide availability, renewability, and total compostability without toxic residues. Starch-based materials always display properties that are less satisfactory than those of traditional polymer materials, which can be ascribed to the inherent characteristics of starch. To make such materials to be truly competitive and to widen its applications, the development of starch-based nano-biocomposites could be a promising solution. This chapter provides the fundamental knowledge related to starch-based nano-biocomposites as well as the most recent developments in this area. Various types of nanofillers that have been used with plasticized starch are discussed such as montmorillonite, cellulose nanowhiskers, and starch nanoparticles. The preparation strategies for starch-based nano-biocomposites with these types of nanofillers and the corresponding dispersion state and related properties are also largely discussed