## 1 Introduction  
Soils can become contaminated with heavy metal(loid) emissions from anthropogenic and natural sources [1, 2, 3]. Although there are several heavy metal(loid)s, arsenic (As) is a carcinogenic metalloid, and is known to be one of the world's most hazardous chemicals, causing several health-related complications in humans [4, 5, 6]. Arsenic in the soil can leach into groundwater and contaminate drinking water, posing a serious risk to human health. Various methods have been employed to remediate heavy metals in soil, such as soil washing, in situ flushing, adsorption, phytoremediation, immobilization techniques (e.g., solidification) / stabilization or encapsulation, and electrokinetic extraction [7, 8, 9, 10, 11]. In recent years, solidification/stabilization (S/S) of arsenic in contaminated soil has emerged as a promising immobilization technology to remediate contaminated lands [8, 11, 12, 13, 14]. In this technique, the constituent contaminants are bound to the contaminated soil using simple stabilizing agents (or stabilizers), hindering the release of heavy metal(loid)s from the soil [15, 16, 13, 15]. This method has various advantages; for example, it is cost-effective, the raw materials are easily available, and it does not produce harmful byproducts during application [15]. The stabilized land can be used for several purposes, such as plantings, gardens, or industry buildings. The stabilized soils can be used as secondary construction material for roads, buildings, and parking lots. Studies have shown that stabilization helps to reduce heavy metal(loid) leaching [8; 15; 16]. Evaluating heavy metal(loid) leaching from stabilized contaminated soil after long-term exposure is important for assessing effective remediation (stabilization) and environmental impacts, because the stabilization bonding has the potential to weaken with long-term weathering. Furthermore, aggregates of stabilized soil may disintegrate into smaller particles with external stresses, such as parking lots or roads. The fractures may be exposed to rainwater infiltration, allowing metal leaching in the water-soluble constituents. Thus, the long-term release of As and any severe release from the stabilized soils requires assessment if we are to protect human health in stabilization-remediated sites. The constituent chemicals leached from contaminated soil and/or other solid materials can be evaluated using different leaching tests [17]. Tests include the batch leaching test, toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and single and sequential chemical extractions [8; 18; 19; 20]. These leaching tests have been widely used due to their simple design, low cost, and short duration. However, these methods cannot represent the release of constituents over different time intervals, and the information is limited to a single liquid-to-solid (L/S) ratio time period [18; 19]. Furthermore, all leaching tests use acidic solutions, making it impossible to evaluate any pH changes with leaching. Recently, studies have tested the release of chemicals using various percolation column tests, such as Nordest (1995), CEN (2004), NEN (2004), OECD (2004), ISO (2007), DIN (2009), and USEPA (2013) [17; 18; 19].These experiments replicate long-term leaching conditions. To the best of our knowledge, only one study has evaluated the release of constituents from stabilized soil using column tests [21]. However, this study used acid rain as a percolating fluid, it did not assess any long-term releases beyond 15 days, and samples were not examined for any cumulative releases as a function of the cumulative L/S ratio. In the current study, we conducted up-flow percolation column tests, representing the actual field leaching conditions, to evaluate chemical leaching and pH changes in the stabilized soil materials for long-term exposure to precipitation.