Introduction purpose: As population growth and industrial expansion continue, surface freshwater reservoirs such as dams have become increasingly vital due to their accessibility and ease of treatment. However, the quality of these water sources has significantly deteriorated, primarily due to the discharge of domestic and industrial wastewater. The proliferation of extensive algal blooms has led to significant challenges in maintaining drinking water quality and raised concerns about public health. This study investigates the impact of various water sources on the physicochemical quality of an Algerian dam over four seasons (December 2020 - October 2021) and explores the factors influencing the occurrence of cyanobacterial blooms to better understand and manage this excessive growth.

Methods: Physicochemical properties and algal composition of the dam water were analyzed monthly to determine nutrient sources and environmental factors affecting cyanobacterial proliferation.

Results: The analysis revealed that the Timgad stream and Reboua valley are notable sources of nutrient enrichment. Elevated temperatures and high nutrient loads, particularly total phosphorus (TP), in Timgad dam water facilitate the proliferation of blue-green algae. Additionally, limited nitrogen content favors the dominance of nitrogen-fixing cyanobacteria such as Aphanizomenon and Oscillatoria. The study also highlights that the low flow rate and high nutrient load of the Timgad stream create favorable conditions for cyanobacterial growth. Conclusions: Nutrient inputs, temperature, and hydrological conditions significantly influence cyanobacterial blooms. Understanding these factors is crucial for implementing effective water management strategies to reduce algal proliferation and protect freshwater quality.

Algerian natural zeolite (denoted NZ) was modified by Hydrochloric Acid (denoted as HZ) and Sodium Hydroxide solution (denoted as NaZ). XRF results indicate that SiO2 is the predominant mineral for the three zeolites. XRD analysis revealed that NZ is primarly  composed of mordenite, followed by chabazite and smaller amounts of quartz.  MEB-EDX results showed slight variations in the Si and Al content for HZ and NaZ, without significant changes to the core structure of the zeolite.  This study aimed to assess the impact of acid and alkalin modification on the removal of two cationic textile dyes (BR₄₆ and BY₁₃) from aqueous solutions. Initial dye concentration, contact time and pH were studied in a batch system. The adsorption capacities of NZ, NaZ and HZ increased with longer contact times, higher initial concentrations, and elevated temperatures. The equilibrium state was rapidly reached and could be described using pseudo-second-order kinetic model. The Freundlish isotherm model provided a good fit for the adsorption process. Pourcentage removal was the highest for NaZ, achieving 97.62% for BR₄₆ and 98.97% for BY₁₃. The lowest removal percentages were noted at pH= 8 for HZ and pH=10 for NZ and NaZ. Adsorption process was spontaneous and endothermic.

The Bellezma Mounts, located in the northeast of Algeria, present cases of hydrothermalism with temperatures ranging between 30° C and 63° C. For the evaluation of the thermal potential of this dissymmetrical mountains chains (often rectified in the South, where Cretaceous and Jurassic limestones emerge), we used a multidisciplinary approach, notably geology, geophysics, hydrogeology, hydrochemistry and the isotopic tool. Hydrogeological investigations have shown that these carbonate formations can offer an important aquifer potential. From the hydrochemical point of view, the warm waters of the Bellezma mounts are characterized by the presence of three different chemical facies: the sulfated-sodium, the bicarbonate-calcium and the chloride-calcium. Evaporite terrigenous origin is attributed to sodium, chlorides and sulphates of these waters. The thermal waters circulation in this region, at great depths in the crystallophyllian formations and the carbonate ones, in contact with terrigenous salt formations, could be responsible of the salinity characterizing these waters, in some places. Geothermometry has shown that these thermal waters acquire a high temperature in their original tanks coming from a depth ranging from 1100 to 2600 m through a fault system that affects the basement. The use of the isotopic tool has shown that the thermal waters of this region are ancient and that their recharge is weak or non-existent.

Polluted water poses significant health risks when it is part of the water sources used for irrigation, leading to the contamination of soil and plants by various pollutants. This work aims, firstly, to assess the degree of pollution of Wadi El Gourzi water (Batna, Algeria), and then to verify the consequences on their use for the irrigation of market garden plants for everyday consumption (lettuce, cilantro, parsley and spinach), both in the aerial part (stems and leaves) and in the soil where they are grown. This study focuses on trace metals (Cr, Pb, Zn and Cd). Soil pollution was assessed by calculating the soil pollution index (PI), while the uptake of these elements by plants was monitored by the transfer factor (TF). The analyses of the Wadi El Gourzi water with the flame atomic absorption spectrophotometer (FAAS) show a maximum abnormal concentration of Cr (17.37 mg∙dm–3), Pb (0.71 mg∙dm–3) and Cd (0.45 mg∙dm–3). For the analysis of the soils irrigated by these waters, the results of the PI show that the soils used for the cultivation of parsley and lettuce are polluted by several metals (PI > 1). The concentrations of trace metals elements (TMEs) in the sampled plants show a significant accumulation of Zn, Cd, Pb and Cr by the vegetables (coriander, parsley, spinach and lettuce). These concentrations are above the permitted standards.

The Teleghma plain is located in northeastern Algeria, in the upper valley of Oued Rhumel. It is characterised by a semi-arid climate with average annual precipitation of 300 mm/ year. The shallow aquifer of Mio-Plio-Quaternary is powered mainly by carbonate formations of the Eocene surrounding the région. The uncontrolled use of groundwater for irrigation has caused water stress in the area which has threatened the degradation of water quality. On the other hand, the intense use of chemical fertilisers for agriculture aims has caused groundwater pollution by nitrates where concentrations exceeded the standard limit recommended by the world health organisation.

Tolga groundwater is one of Biskra's most important water supplies for both drinking and agriculture. The purpose of this study is to assess the hydrochemical and isotope (2H and 18O) signature of water in the Tolga area. To evaluate the hydrogeology of groundwater in the Tolga region, a chemical, piezometric, and isotopic research was employed. The results of the Piper diagram revealed that there is just one major hydrochemical facies in the research region, which corresponds to Ca–Mg–Cl–SO4. The piezometry of limestone sheets shows that as one goes westward, the turns become less substantial, with turns about 20 meters and a piezometric level of 140 m. For the rst time, the local meteoric water line (LMWL) was drawn for Complexe Teminal (CT) and Continental Intercalaire (CI) on Tolga groundwater. The Tolga area LMWL refers to the equation δ2H= 7,18 δ18O + 4.17 with R2 about 0.85. CI and CT measurement locations indicate deuterium excess values ranging from 8.35 to 12.57. Indeed, the majority of values were more than 10‰ (mean of 10.36 ± 2.01‰). Furthermore, waters from Eocene have an isotopic composition of-7.57 ± 0.68‰ in δ18O and − 49.04 ± 4.69‰ In δ2H. The results of the sample characterisation analysis show that the majority of the groundwater samples analysed are of the Ca-Mg-SO4 water type. In addition, the intense exploitation aquifer water and the region's arid climatic conditions resulted in a large decrease in the piezometric limestone level. Finely, the signature of 2H and 18O data indicate that water comes from local precipitation and recent water, and groundwater recharge is in uenced by quick in ltration.