Influence of Salinity and Conductivity of Brackish Waters on the Chemical Properties of Guinean Mangrove Soils and Their Suitability for Making Earthen Bricks

This study examines the impact of salinity and brackish water conductivity on the chemical characteristics of Guinean mangrove soils and their suitability for making mud bricks. The waters of seven coastal and estuarine sites were analyzed to determine their chemical parameters (pH, CE, TDS, salinity) and compared to the characteristics of the adjacent soils. The results reveal a high variability between the parameters analysed at the water level (EC: 528 to 8,936 μS/cm; salinity: 10 to 300 mg/L) and at the soil level (acidic pH: 5.5–5.8; chlorides up to 265 mg/kg). This confirms the influence of saline intrusions on soil mineralization. Statistical analyses, based on robust methods (permutation and bootstrap tests), show a very strong correlation between CE and TDS (r = 1.00; p < 0.001) and highlight the major role of mineralization in the structuring of the data (PC1 ≈ 82%). These results highlight that areas with high mineralization (Kaporo Bridge, Tobolon) have high risks of efflorescence and brick degradation, while sites with low CE/TDS (Lambagni, Limbita 2) are more favorable. To ensure the durability of the bricks, corrective measures are recommended: pH adjustment by alkaline amendment, reduction of soluble salts by washing or partial substitution, and stabilization with appropriate binders. The integration of these practices is essential to limit the effects of saline intrusion and ensure the performance of earthen constructions in coastal areas.