soil contamination) [4]. Unlike various contaminants in the environment (i.e., organic materials), metals need to be reduced, removed, or immobilize from the soil by transformation techniques such as phytoremediation. Although plant roots can absorb heavy metals via soil solution, depending on their phytoavailability [5], the phytoremediation time is relatively long [6]. Nevertheless, other remediation techniques are available to remove heavy metals from soils [7; 8]. Among the various contaminants present in the environment, arsenic is one of the heavy metals that are more frequently found in contaminated sites [9; 10]. Arsenic is considered a metalloid since it exhibits both properties of metals and non-metals [2]. Arsenic contamination is distributed unevenly, worldwide. It happens due to natural and anthropogenic processes [11], such as volcanic eruptions, rock mineralization, and industrial and mining activities [12; 13]. Arsenic can be introduced into the soil by the discharge of industrial wastewaters that contain different heavy metals [7]. Moreover, fertilizers, pesticides, manure, and sludge are significant sources of arsenic in agricultural soils [2]. Arsenic is one of the most toxic and carcinogenic elements associated with various chronic disorders [14; 15; 16]. Although [PERSON] et al. [17] reported the presence of arsenic in the liver of ground doves (_Columbina passerine_, 0.046 mg/kg) and house sparrows (_Passer domesticus_, 0.025 mg/kg), it did not reach the toxic thresholds. Nevertheless, [PERSON] and [PERSON] [18] reported a decrease in chicks' growth due to a 50 mg/kg arsenic content in their diet. According to the prevailing environmental conditions, arsenic species are classified as organic and inorganic. However, arsenate (As+5)--an inorganic arsenic species--is more frequently found in aerobic environments, such as the aerated or unsaturated zone of the soil, compared to organic arsenic species [11]. Despite the efforts made to study the effects of heavy metal contamination on soil properties, there is scarce information about the impact of arsenic contamination on the mechanical and hydraulic properties of the soil. Therefore, it remains a problem in environmental geotechnics due to the uncertainty in the mechanical behavior of civil structures founded on such soils. Unsaturated soils experience negative pressures called suction. Soil suction (\(\psi_{t}\)) is measured through its components, known as matric (\(\psi_{m}\)) and osmotic suctions (\(\psi_{o}\)). The \(\psi_{o}\) depends on the effect the dissolved salts and contaminants can create in the pore water. Nevertheless, its contribution to \(\psi_{t}\) is negligible in natural soils. In contrast, the \(\psi_{m}\) is developed by capillary forces and adsorption due to the soil's structure [19] and is determined by the soil's particle size [20]. Soil suction varies according to the structure and moisture content of the soil. The curve that describes such variations is known as the soil-water retention curve (SWRC). This curve is used to evaluate the essential aspects of unsaturated soil mechanics because of its hydromechanical coupling [21] that has diverse applications on contaminated soils, protective barriers for excavations, and the remediation of contaminated sites [22]. Moreover, the reactions between soils and contaminants have a coordinated effect on the \(\psi_{o}\), which, in turn, affects the mechanical properties of contaminated soils [23] and the liquid's movement regulation through the soil mass due to the subsequent changes in its geotechnical properties [23; 24; 25]. A frequently used method to evaluate soil suction is the filter paper method due to its reliability [26; 27; 28; 29] and the suction range it covers (from 0 to 1 \(\times\) 10\({}^{6}\) kPa and from 1000 to 500,000 kPa for the total and matric suction, respectively) [27]. This test method is described by the ASTM D5298 standard [30].