Besides their potential for carbon sequestration, compost and biochar application in agriculture may constitute an alternative to mineral fertilizers by improving soil fertility and productivity in carbon-poor soils. This study focused on the impact of biochar and compost produced from date palm residues on nitrogen (N) leaching and plant uptake in a sandy soil cultivated with barley under arid climatic conditions. In addition to the unamended control soil (S), treatments with biochar (BC), urea (U), biochar + urea (BCU), compost (C) and biochar + compost (BCC) were tested. We followed soil fertility parameters, N leaching losses, N uptake and plant growth. Results showed a significant increase of barley yields with compost compared to urea (+66%) treatment (U), biochar amended (BC) and unamended soil (S). Biochar alone or co-applied with a nutrient source seems to reduce barley shoot biomass and grain yields at short term. Leachate N recovery and soil extractable inorganic N at the end of barley cultivation indicated that compost did not provide N in excess at barley maturation stage. Compost amended soils led to the highest N losses through leaching and thus environmental risk of N vertical transfer. However, compost had positive effects on soil nutrient status and barley yields. No synergistic effect was observed between biochar and compost. In conclusion, this paper highlights that date palm compost improved barley productivity in a coarse-textured soil, but with very short-term effects concerning available soil N.

Rock-based materials exposed to outdoor environments are naturally colonised by an array of microorganisms, which can cause dissolution and fracturing of the natural stone. Biocolonisation of monuments and architectures of important cultural heritage therefore represents an expensive and recurring problem for local authorities and private owners alike. In this area, preventive strategies to mitigate biocolonisation are generally preferred to curative approaches, such as mechanical cleaning by brush or high-pressure cleaning, to remove pre-existing patina. The aim of this work was to study the interaction between biocidal polyoxometalate-ionic liquid (POM-IL) coatings and calcareous stones and evaluate the capacity of these coatings to prevent biocolonisation through a series of accelerated ageing studies in climate chambers, carried out in parallel with a two-year period of outdoor exposure in north-eastern France. Our experiments show that POM-IL coatings did not affect water vapour transfer nor significantly alter the total porosity of the calcareous stones. Simulated weathering studies replicating harsh (hot and wet) climatic weather conditions demonstrated that the colour variation of POM-IL-coated stones did not vary significantly with respect to the natural uncoated stones. Accelerated biocolonisation studies performed on the weathered POM-IL-coated stones proved that the coatings were still capable of preventing colonisation by an algal biofilm. However, a combination of colour measurements, chlorophyll fluorescence data, and scanning electron microscopy imaging of stones aged outdoors in northern France for two years showed that coated and uncoated stone samples showed signs of colonisation by fungal mycelium and phototrophs. Altogether, our results demonstrate that POM-ILs are suitable as preventative biocidal coatings for calcareous stones, but the correct concentrations must be chosen to achieve a balance between porosity of the stone, the resulting colour variation and the desired duration of the biocidal effect over longer periods of time, particularly in outdoor environments.

Chalk groundwater is an important aquifer resource. It is intensively exploited for human use, with a large proportion utilized for drinking water. The improvement of the knowledge on Chalk aquifer hydrogeological functioning is essential for the management of this resource. Here, we developed a methodology based on a combination of hydrodynamic, hydrochemistry and groundwater dating tools. A study site with Chalk outcrops was selected in NE France where groundwater geochemistry and water level were monitored continuously for 2 years from 2017 to 2019 and groundwater residence time was estimated using CFCs and SF6. Overall, the aquifer has an inertial behaviour with respect to recharge. Nevertheless, a rapid water level response following rainfall events was observed at one site, suggesting the presence of highly developed fracture network at the local scale. According to the mixing process (piston flow, exponential or binary mixing) defined at each sampling site, groundwater dating indicated rather heterogeneous ages ranging from modern to about 50 years. High spatial and temporal heterogeneities were observed and interpreted by a combination of hydrogeological setting, residence time and land use information, highlighting main factors governing the Chalk groundwater geochemistry including water level fluctuation, thickness of the Unsaturated Zone (UZ), superficial formations, distribution of fracture network, aquifer-river relations and human activities. A conceptual model was proposed accordingly to explain the hydrogeological functioning of unconfined Chalk aquifers.

The durability of stone monuments is a constant problem as their decay through weathering is irremediable and endless. Fortunately, coatings are becoming more and more efficient and tailored to specific alterations of the stone material. This study aimed at developing an eco-friendly coating with both hydrophobic and biocide properties based on a silane/siloxane emulsion as a water repellent combined with chitosan and silver nitrate as biocides. Chitosan was first added at different concentrations to the water repellent and its efficacy was tested in laboratory conditions by the inoculation of axenic suspension of the green algae Chlorella vulgaris on a building porous limestone. Chlorophyll a fluorescence analysis displayed the chitosan acted on the photosystem of algae and limited their development but its effect was not optimal and higher dose modified the aspect of the stone. Low concentration of silver nitrate achieved a good performance thanks to the combination with the chitosan and the water repellent. The properties of coated stones and the efficacy of the formulation were assessed at two different doses of coating. The results showed that the lowest dose gathered all requirements to both preserve the stone monument with a weak colour change over time and to reach optimal biocide effect and a good hydrophobicity.