The intensive use of nitrogen (N) fertilizers in maize (Zea mays L.) cropping in sub-Saharan Africa (SSA) contributes significantly to nitrous oxide (N₂O) emissions. Due to limited data on emissions and emission factors (EFs) in SSA, this study investigates GHG emissions and proposes EFs under different fertilization regimes in maize cropping in Burkina Faso (West Africa). A randomized complete block design was used with five treatments: (i) control: no fertilizer (CK), (ii) cattle manure (M), (iii) chemical fertilizer (NPK), (iv) a combination of chemical fertilizer and cattle manure (NPKM) at the national recommended rate, and (v) farmers’ practices, which involve chemical fertilizer combined with manure at the farmers’ rate (NPKM+). Cumulative N₂O emissions varied significantly among treatments (p < 0.05), with the highest under NPKM (2.86 kg N₂O-N ha⁻¹) and the lowest under CK (1.93 ± 0.11 kg N₂O-N ha⁻¹). NPKM also showed the highest methane (CH₄) uptake (−0.62 kg CH₄-C ha⁻¹; p < 0.001), while CK exhibited an increasing trend (0.74 kg CH₄-C ha⁻¹). The highest N₂O EF was recorded for NPK (0.37 ± 0.05%), 63% lower than the Intergovernmental Panel on Climate Change default value. Although NPKM treatment resulted in the highest global warming potential and maize yield, it also achieved the lowest greenhouse gas intensity per unit of yield, highlighting a more efficient trade-off between productivity and climate impact with nitrogen fertilizer use. NPKM+ was the most effective in maintaining high maize productivity with lower yield-scaled N₂O emissions and GHG intensity. These findings suggest that an integrated approach combining organic and inorganic fertilizers can mitigate soil GHG emissions. Further research is needed to refine climate-smart fertilizer combinations for sustainable maize production in SSA.

Groundwater continues to be useful as the main source of drinking water in semi-arid and arid regions of sub-Saharan Africa. The main goal of this work is to assess the health risks associated to the consumption of borehole water in urban and peri-urban areas of Niamey in Niger. Hydrochemical analyses were carried out from water samples of 16 boreholes using standard methods (AFNOR). The parameter measured are pH, Electric conductivity (EC), HCO₃^-, NO₃^-, NO₂^-, Cl^-, SO₄^2-, F^-, Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺ and Mn²⁺. 80% of the samples are very risky for the populations. About 56% of boreholes have a nitrate concentration < 30 mg/L and 44% of samples have more than 50 mg/L corresponding the limit standard set by the WHO. High nitrite contents (NO₂^-) were determined from the same borehole water samples and contain more than 10 mg/L, and are considered unfit. Main causes are the lack of good urban wastes managements, and the uncontrolled use fertilizers in the agricultural sectors. The sites containing between 2 and 3 mg/L of Fe²⁺ are located in areas of lateritic soils. About 12% of samples contain Mn²⁺ above the WHO standard (0.4 mg/L). This study of few boreholes from Niamey and its close rural areas demonstrates that nitrate, nitrite and manganese contents may cause major risks, in particular gastric, cardiovascular, carcinogenic and neurological diseases. With the growing population and urbanization, the lack of sanitation and of good management of urban waste, monitoring of groundwater quality is urgently need to preserve human health. Regular, rapid and less costly monitoring of the pH and electrical conductivity of urban borehole waters can help to prevent the risk of poisoning by nitrate, nitrite and by heavy metals such as manganese.

Soils are a vital natural resource that deserves more attention and affection, because they are full of everything that living beings need to survive. Now, soil hydric erosion is a phenomenon that causes serious problems of flooding and limiting food production in semi-arid climate zones, leading to a chronic socio-economic and environmental disasters. This process is further exacerbated by the ever-increasing global warming. This study aims to better understand the processes and consequences of water erosion, in order to better prevent the risks that could be associated with the rising of global temperature. The study area is located in the semi-arid climate of Isser watershed in the northern-west of Algeria. Soils of the area have a silty-clay texture. The surfaces are covered with little gravel (8%), covered to 72% of vegetable debris and are cracked up to 53%. These characteristics may reduce the runoff velocities and protect soils against erosion. However, clearing, overgrazing and farming systems favor runoffs that cause transfers of sediments through the destruction of the surface physical-chemical properties and thereby its natural structural stability. The study shows a slowdown in the infiltration rate of runoff water when soils are severely dehydrated. This may be an explanation for the paradoxes of the recent floods in arid and semi-arid areas of the world. Soils aridification due to global warming could increase its cracking and damage their structural stability. This climatic phenomenon will result in the recurrence of floods and the massive infiltration of surface water into groundwater, thus generating their pollution. The study also shows that the sum of all chemical properties (moisture, OM, soil carbon, calcite, and total nitrogen) in percentage is highly correlated with soil structural stability. Therefore, the key factor in mitigating this process would be to maintain a sufficient level of organic matter in the soils.

Coal Bottom Ash (CBA) is an important second source of strategic metals such as Lithium (Li) and Rare Earth Elements (REEs). Its recovery generates new strategic resources in the current climate and environmental context. It is in this context of resource circularity that this study aims to assess the economic potential of Li and REEs in six CBA samples from Sonichar, in Niger. X-ray diffraction and chemical (XRF and ICP-MS) analyses were performed on the six CBA samples to determine their mineralogical and chemical composition (oxides, Li and REEs). The Enrichment Coefficient (EC), the percentages of critical metals (Cp), excessive metals (Ep) and non-critical metals (Up), as well as the economic prospectivity coefficient (Cout1), were used to assess the economic potential for Li and REEs recovery. The main oxides present in the CBA are: SiO2 (51.99%), Al2O3 (23.79%) and Fe2O3 (4.43%). The main minerals are: mullite (70.16%), quartz (29.21%) and hematite (0.63%). The CBA samples have high Li contents, ranging from 89.65 to 109.59 mg/kg, and low REE contents, all of which decrease from MC1 (< 80 μm) to MC6 (16-20 mm). The EC values for Li range from 5.48 to 4.48 (EC > 1). These EC values indicate Li enrichment. All the REEs EC values were below 1 (EC < 1). The Li and REEs EC values increase as the particle size decreases. The parameters used to assess the economic potential of REEs gave the following results: CpMean = 33.03%, EpMean = 39.03%, UpMean = 27.94%, and CoutlMean = 0.85. Taking into account the average values of CpMeam = 33.03% and Cout1Mean = 0.85, the Sonichar CBA can be considered a promising secondary source for the recovery of REEs. This study opens up prospects for the extraction of Li and REEs contained in the Sonichar CBA. Major Findings: This study confirms the Li and REEs potential of the Sonichar Niger CBA, with an enrichment coefficient > 5 for Li, and a critical metals percentage of 33.03% and an economic prospectivity coefficient of 0.85 for REEs, making the Sonichar CBA a promising secondary source for the recovery of Li and REES.