The groundwater contained in the basement formations of sub-Saharan countries is the main source of drinking water for the population in rural and semi-rural areas. Captured by boreholes and wells, it is used for domestic purposes, irrigation, and other socio-economic activities. Given the increased pressure on the resource due to population growth and urbanization, assessing its origin, availability, and quality for sustainable management is imperative. This study was carried out in the Kara River Watershed (KRW) in northern Togo. The study aimed at determining the recharge and mineralization processes of the groundwater in the watershed using conventional graphs, multivariate statistical analyses, and geochemical modelling. Physico-chemical (pH, temperature, and TDS), chemical (Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, Cl-, NO3- and SiO2), and isotopic (δ2H and δ18O) analyses were carried out on 149 groundwater samples (boreholes and wells). The results showed that the isotopic composition of the groundwater suggests recharge of meteoric origin, often influenced by secondary evaporation and important mixing processes. From a hydrochemical point of view, the groundwater is generally low mineralized with TDS ˂ 1000 mg/L. These waters' main mineralization processes are water/rock interactions and human activities influence. The heterogeneity of the geological formations is responsible for the spatial variability of the water chemistry, with CaMg-HCO3-, intermediate, and Na-HCO3- water types predominating. Hydrolysis of silicate minerals, ion exchanges, and dissolution of carbonate minerals (calcite and dolomite) are responsible for water mineralization. Nitrates of human and animal origin often strongly degrade water quality. The results of this study will enable decision-makers to implement a relevant strategy for the sustainable management of groundwater resources, particularly in the city of Kara, where human activities massively impact groundwater quality.Keywords: Recharge processes, hydrochemistry, water/rock interactions, hard-rock aquifer, human activities, Kara River, Togo.

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.

This study investigated the adsorption of Cu2+ and Pb2+ onto a histosol (peat soil) as a function of pH and compared it to their adsorption onto its humin fraction. The use of the NICA-Donnan model, considering humic acid and humin as soil reactive solid phases and fulvic acid as reactive dissolved organic matter, satisfactorily described the adsorption behaviour of Cu2+ and Pb2+ onto histosol. Both metals were adsorbed mainly via carboxylic sites of both solid phases with a higher contribution of humic acid. Nevertheless, this study highlighted the significant role of humin, accounting for up to 37

In the Kara River Watershed (KRW, northern Togo), drinking water is mainly supplied by groundwater flowing through fissures in the metamorphic formations of the Dahomeyides belt. The study was based on the use and valorisation of hydrogeological archive dataset from 1970s to 2021. The database comprises 1389 boreholes, but only 710 are considered after pre-treatment, and provides information mainly on total depth, weathering thickness, discharge at drilling, piezometric level, specific discharge, transmissivity, and the nature of the lithology tapped. The methodological approach involved statistical analysis of data, characterization of the fissured horizon, establishment of relationships between hydrodynamic parameters and satellite image processing. The results showed that the aquifers structure is close to those observed worldwide in hardrock context and they provide operational details on the hydrogeological functioning of these environments in the West African particular context. From the surface downwards, aquifers show a layer of saprolite (thickness between 0.2 and 37.3 m) acting as a storage level, a fissured layer whose permeability depends on the number and connectivity of the fissures, and then a level of very low permeability, unfissured bedrock. In the study area, the depth of the useful fissured medium is 52 m with an average useful discharge of 7.1 m3 h- 1. The coefficients of variation for specific discharge and transmissivity are greater than 100%, reflecting the structural heterogeneity of the study area. Analysis of the discharges measured in the boreholes as a function of lithology shows that the metasediments are more productive than other geological formations. Finally, all the geological, hydrogeological, and hydrodynamical data have been used to propose a preliminary conceptual model of the watershed's hardrock aquifers. These results will serve as decision-making tools for water managers and will facilitate the policy of integrated management of groundwater resources at the scale of the KRW. The developed methodology also shows how archive data should be used to achieve optimized management of aquifers without major investments.

Generally, soils of arid and semi-arid regions have low water retention properties due to high sand and low organic carbon contents. This study aimed at quantifying the effect of date palm-based organic amendments (OAs) on the water retention properties of two soils (sandy loam and silty loam), as well as the influence of sand supplementation (0.5–2 mm) on the magnitude of the effect of OAs. Different grain size distributions were obtained by adding sand to natural soils. For this purpose, sand was added to the two soils (1/3 and 2/3) and different soil-OA combinations were tested at a dose of 3% by mass: compost alone, biochar alone and a mixture of biochar and compost (50:50 in mass), in addition to unamended control soils. Soil water contents were measured at nine matric potentials ranging from the saturation to the permanent wilting point. Biochar was more efficient than compost at improving soil water retention. The effect of organic amendments on water retention increased with sand content. In most cases, soil water content values were significantly higher for biochar-amended soils than for unamended or compost-amended soils. The weakness of the effect of compost addition (if alone) was probably due to its properties and notably its high mineral content and electrical conductivity. Soil sand supplementation led to higher differences between the OA-amended soils and unamended soils. Changes in available water capacity reached +26% and +80% in a sandy loamy soil enriched with 2/3 sand and amended with compost and with biochar, respectively, compared to the unamended soil. These results show that sand content (and more generally, soil texture) influences the effect of OA application. Thus, the application of biochar from date palm residues in soil seems to be an effective solution to improve the water retention properties of coarse textured soils and contribute to optimizing the use of water resources in irrigated areas.

In the Sahel, millet (Pennisetum glaucum L.) is one of the main cereals cultivated as rain-fed crops, predominantly by vulnerable small producers, on poor soils leading to increasingly low growth and production. The aim of this work was to increase millet production by using organic manure (compost) at low cost (accessible to all) and respectful of the environment. The methodology used was participatory (with producers) and consisted of monitoring the growth and yield parameters of two varieties (local and improved) of millet by applying three doses of compost: low dose (1 tha-1 ), medium dose (3 tha-1 ) and high dose (5 tha-1 ) with a control (without compost). The results showed that millet achieves most of its growth in height before the 71st day after sowing. The high dose of compost increased the height of the millet plants by more than 22 cm and the number of tillers by more than 17% compared to the control. The variety of millet did not directly affect plant height and number of tillers. The high dose of compost increased the yield by more than 44% and the dry matter by more than 37% compared to the control. The yield of the improved millet variety increased by more than 32% compared to the local variety. The local variety had an increase in dry matter of more than 11% compared to the improved variety. The study helped convince several producers to accept the use of compost. Its large-scale extension, in producers' fields, could convince those who are reluctant to adopt innovation.

The groundwater contained in the basement formations of sub-Saharan countries is the main source of drinking water for the population in rural and semi-rural areas. Captured by boreholes and wells, it is used for domestic purposes, irrigation, and other socio-economic activities. Given the increased pressure on the resource due to population growth and urbanization, assessing its origin, availability, and quality for sustainable management is imperative. This study was carried out in the Kara River Watershed (KRW) in northern Togo. The study aimed at determining the recharge and mineralization processes of the groundwater in the watershed using conventional graphs, multivariate statistical analyses, and geochemical modelling. Physico-chemical (pH, temperature, and TDS), chemical (Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, Cl-, NO3- and SiO2), and isotopic (δ2H and δ18O) analyses were carried out on 149 groundwater samples (boreholes and wells). The results showed that the isotopic composition of the groundwater suggests recharge of meteoric origin, often influenced by secondary evaporation and important mixing processes. From a hydrochemical point of view, the groundwater is generally low mineralized with TDS ˂ 1000 mg/L. These waters' main mineralization processes are water/rock interactions and human activities influence. The heterogeneity of the geological formations is responsible for the spatial variability of the water chemistry, with CaMg-HCO3-, intermediate, and Na-HCO3- water types predominating. Hydrolysis of silicate minerals, ion exchanges, and dissolution of carbonate minerals (calcite and dolomite) are responsible for water mineralization. Nitrates of human and animal origin often strongly degrade water quality. The results of this study will enable decision-makers to implement a relevant strategy for the sustainable management of groundwater resources, particularly in the city of Kara, where human activities massively impact groundwater quality. Keywords: Recharge processes, hydrochemistry, water/rock interactions, hard-rock aquifer, human activities, Kara River, Togo.

Agricultural residues are generated during the production and processing of agricultural crops. Under modern date palm plantation practices, field operations generate huge quantities of residues, which are discarded with little valorization. The date palm agro-industry produces significant amounts of waste. The accumulation of these residues can cause ecological damage to the oasis ecosystems. There is a lack of comprehensive data on long-term research studies that aim to assess the impact of date palm waste management practices. Composting and/or pyrolysis of date palm residues showed benefits for improving soil physical and chemical properties, particularly in sandy soils. This claim holds particular significance for arid and semi-arid regions, which are characterized by low fertility and are susceptible to soil degradation, accentuated by ongoing climate change. This review summarizes the existing literature concerning the valorization of date palm residues with regards to compost and pyrolysis processes, as well as the impact of their application on soil quality. Further research is required to assess the effects of using date palm residues for better soil amendment management. Research should focus on composting and biochar technologies for date palm residues and their application in arid and semi-arid regions to combat soil erosion and degradation. Increasing the beneficial uses of date palm residues could lead to sustainable and economic growth in dry areas.

A series of xylose-based ligands was obtained using a convenient approach, in a few steps from D-xylose. The complexation properties of these ligands towards Au3+ cations have been studied through different methods (multinuclear NMR, mass spectrometry, elemental analysis). The biological properties (antibacterial and anti-tumoral) of all the isolated xyloside Au(III) complexes were investigated in vitro. The xyloside Au(III) complexes gave the highest activities against E. coli (vs P. aeruginosa, S. aureus and S. epidermidis). The study also revealed that the nature of the sugar may play an important role in determining the selectivity of the antibacterial effect. Preliminary anti-tumoral evaluations showed that one complex containing a polyamine chain, exhibited interesting anti-proliferative activities on breast tumor cell lines MDA-MB-231 and BT-20. The anti-migratory effect of this complex also showed an average 35 % reduction in cell migration on the same two cancer cell lines.

Humin, which is the insoluble part of humic substances, plays an important role in regulating the behavior and fate of metallic trace elements at the soil/water interface. However, compared to the two other fractions of humic substances, humic and fulvic acids, humin has been the least studied due to its insolubility and difficulties in purification. In this study, humin was extracted from a peat soil following the International Humic Substances Society (IHSS) protocol. The adsorption behavior of copper(II) and lead(II) onto humin as a function of pH was studied at different solid charges and metallic cation concentrations and was described by the NICA–Donnan model. The proportion of the two types of functional groups considered in this model, carboxylic and phenolic groups, was determined by cross polarization/magic angle spinning solid-state 13C nuclear magnetic resonance spectroscopy (13C CP/MAS NMR). The NICA–Donnan model was applied to describe the adsorption of copper(II) and lead(II) onto humin using generic parameters previously defined for humic acids with only few parameter adjustments. This approach allowed a good description of experimental adsorption data at the different tested conditions with the main involvement of carboxylic moieties in the metallic cation adsorption. This study highlights the reactivity of humin, an important fraction of soil organic matter little studied until now, toward copper(II) and lead(II) and proposes, for the first time, a simple and pertinent approach using the NICA–Donnan model to successfully describe and predict the binding of these two metallic cations onto humin.

The cultivated dryland soils of North Africa present low fertility and productivity due to low organic matter content (Brahim et al., 2021). Date palm residues are an abundant resource in these regions and only a minor part is recovered in oasian agroecosystems. The ISFERALDA project – Improving Soil FERtility in Arid and semi-arid lands using Local organic DAte palm residues – aims at developing the use of organic amendments based on traditional production (composting and slow pyrolysis) as a key tool to improve soil fertility and soil properties.The objective of this study was to quantify the effects of compost and biochar based on date palm residues on soil water retention. Two soils with properties similar to North Africa soils (sandy loam texture, alkaline pH, low organic matter content) were collected in a semi-arid Mediterranean area of southeast Spain. In addition, and in order to test further the influence of soil texture, soil sand content was artificially increased by supplementing the natural soils with washed quartz sand. The different types of organic amendments were tested at a dose of 60 t/ha (Edeh et al., 2020): compost alone, biochar alone and mixture of compost and biochar (50:50 in weight). Water content was measured using pressure membrane apparatus at nine different matric potential (pF), ranging from the saturation to the permanent wilting point.The results showed that water retention was higher in soil with organic amendments regardless of the pF and the soil type. For a specific soil, the addition of biochar alone or in combination with compost to the soil resulted in higher values than compost alone. The improvement in water retention properties was more pronounced for soils amended with sand. Thus, composting and/or pyrolysis of date palm residues is a viable alternative to improve the water retention properties of sandy and loamy soils. Keywords:Date palm – arid and semi-arid lands – organic amendments – soil water retentionReferences :Brahim, N., Karbout, N., Latifa, D., & Bouajila, A. (2021). Global Landscape of Organic Carbon and Total Nitrogen in the Soils of Oasis Ecosystems in Southern Tunisia. Agronomy, 11, 1‑17.Edeh, I. G., Mašek, O., & Buss, W. (2020). A meta-analysis on biochar’s effects on soil water properties—New insights and future research challenges. The Science of the Total Environment, 714, 136857. https://doi.org/10.1016/j.scitotenv.2020.136857

The Kara River watershed (KRW), northern Togo, is facing climate-change impacts that have never been clearly characterized. Six decades of rainfall data (1961–2020) from six measuring stations ideally distributed across the watershed were used in this study. The flow records from two stations situated in contrasting locations on the KRW were also used. Statistical tests were conducted to assess the spatial and temporal variability of the rainfall and to detect tendencies within these meteorological series. The water balance method and calculation of the dry-off coefficient and of the groundwater volume drained by rivers allowed evaluating the impact of climatic evolution on surface flow and on groundwater volumes during the six decades studied. The results showed contrasting spatiotemporal variability of rainfall (and of aquifer recharge) over the watershed with a decreasing tendency upstream and an increasing one downstream. At the same time, the water volume drained by the aquifer to sustain the river’s base flow decreased from −22% to −36% depending on the measuring station. These results constitute a decision-making tool for Togolese water resource managers and are of primary importance for characterizing the fate of water resources worldwide in regions subject to severe droughts.

The dryland soils of North African region are usually poor in organic matter, which is the cause of low soil fertility. Oases are the main driver of arid areas economy in this region. In oases, date palm is the main source of income for farmers. Oases also represent shelter for local population and even, in some cases, tourism. The harsh environment in the desert regions of North Africa makes these regions vulnerable to many environmental threats. Only a minor part of date palm cultivation by-products are recovered, including for example palm branches used for fixing sand dunes, as fences in oases or for shade. Their valorization as bioresources, with a potential effect on soil fertility (and thus on oases ecosystem productivity), has received little attention to date. Based on the few available results for the maintaining of land productivity and sustainability of the oasis system, the ISFERALDA project aims to increase resilience to climate change of agroecosystem while ensuring comparable or higher incomes to local farmers in semi-arid and arid areas. The project aims at developing the use of organic amendments based on local agriculture wastes, and more specifically the date palm residues, as a key tool in land restoration. Based on traditional production (composting, pyrolysis), the project will focus on refining processes and improving products’ quality and adequacy with plant needs and substrate properties. Innovative farming systems will be developed and contribute sustainable management of date production, generating income and creating employment as well as improving environmental parameters. The influence of different kinds of organic amendments on environment, yield, and socio-economic development will be assessed. ISFERALDA will therefore design a new strategy to support agricultural practices within a framework acceptable to local actors and in line with the objectives of circular economy of local resources and sustainable development. The innovation potential of the project is based on a multidisciplinary and highly integrated approach. In this project, a socio-economic analysis, based on surveys and on the cost/benefit analyses, will familiarize the farmers with the economic interest of the production and use of the proposed organic treatments. Furthermore, an assessment of the benefits for soil quality and fertility (physical, chemical and biological properties) will be conducted. The proposed research activities include: * Detailed description of the characteristics of each amendment studied, refinement of traditional processes, * laboratory experiments to fully describe the properties of the different treatments and to explain the evolution of the physical, chemical and microbiological properties of the soils, * field experiments, in five different representative sites of arid and semi-arid zones in Algeria and Tunisia. The contacts with other stakeholders and particularly the farmers will promote, on one hand, the acceptance of these practices if they are deemed beneficial from an economic and agronomic point of view. On the other hand, it will also disseminate this new knowledge to the agricultural main actors and will upscale the results from case studies to regional and national scale across the Mediterranean Basin.

Detention ponds (DPs) are used to reduce the pesticide inputs from runoff to surface water. This study aimed to assess the role of the sorption process in the mitigation of a DP made up of four successive units and built at the outlet of a vineyard catchment in Champagne (France) to treat runoff waters. Sorption kinetics and isotherms were studied for four pesticides with contrasting properties, cyazofamid (CYA), fludioxonil (FLX), fluopicolide (FLP) and oryzalin (ORY), in the presence of copper in sediments and four emergent macrophyte roots and rhizomes sampled in the DP units 2 (photodegradation) and 3 (phytoremediation). The adsorption equilibrium time (from 24 to 96 h) was less than the hydraulic residence times in the two units (6 and 18 days on average) between November 2016 and November 2017. Sorption equilibrium could then be reached in situ in 85 % of cases. The Kd coefficients of the four pesticides were overall greater in plant roots (14-6742 L kg-1) than in sediments (6-163 L kg-1) because of their affinity for organic matter and the molecular and porous structure of the plant matrices. Typha latifolia and Iris pseudacorus exhibited greater Kd coefficients than Mentha aquatica and Phragmites australis, probably due to their greater specific surface area. The pesticide adsorption capacity in sediments and in T. latifolia and I. pseudacorus roots (ORY >= FLX > CYA > FLP) was linked to their Kow. The estimated total annual amounts of the four pesticides adsorbed in situ were determined to be 1236 mg for unit 2 and 1570 mg for unit 3. The four plants improved the removal efficiency of the unit 3 by 33%. Thus, the establishment of suitable and effective plants should be promoted to optimize sorption processes and DP effi-ciency in reducing water pollution.