## 1 Introduction  
Soil erosion has environmental and socioeconomic significances. In arid areas, soil erosion by wind leads to dust emission to the atmosphere that increase air pollution and risk exposure to human health [1; 2; 3]. Current global estimates of dust-related particulate matter (PM10), which is less than 10 \(\,\mathrm{\SIUnitSymbolMicro m}\) in diameter, loading varies widely from ~6 to 30 million tons [4]. There is uncertainty regarding the relative dust contribution of disturbed soils in non-desert areas, which are subjected to human activities. The continuous population growth increases the land uses of agriculture, mining, and vehicles traveling on unpaved roads in these areas. Such activities change the topsoil properties, reduce the soil stability, and thus increase soil erosion and dust emission [5; 6; 7].  
There is a growing interest in soil stabilization to reduce soil erosion and dust emission from disturbed soil in arid and semi-arid regions. There are various dust-control materials commonly used to reduce dust emission from soils. These products are based on natural and synthetic polymers such as lignin, resin, bitumen, and polyvinyl acetate (PVA). The typical application of these products is by spraying the solution on the soil surface at certain concentration (liter per square meter). Among the common dust-control materials, the hydrous-magnesium chloride (brine) is one of the most efficient application in preventing dust emission [8]. The adverse soil pollution and environmental footprint resulting from the use of the common dust-control materials are still unclear. Moreover, typical applications for dust control do not provide a reinforcement of the topsoil, and thereby stabilization against physical pressures due to vehicle traveling.  
One of the most common materials that is used for soil stabilization is PVA. When the PVA solution is absorbed in the soil, the polymers enveloping the soil particles that remain aggregated after the evaporation processes. PVA is especially efficient in soils with granular texture and with small specific surface area, in which it creates a stable crust with strong tensile strength. However, the environmental impacts of this synthetic polymer and its efficiency in fine-grained soils with high content of dust are still unclear. This raises the need to develop an effective material from the perspectives of dust control, soil stabilization, and environmental footprint. Geopolymers are a group of mineral-based materials that commonly used in the building industry [9]. Geopolymer can be synthesized by mixing calcined kaolin and strongly alkaline solutions (such as NaOH or KOH) and then curing at a room temperature [10]. Several studies have examined the use of various geopolymers for loess soil stabilization, including fly ash, lime, and cement, etc., [11; 12; 13; 14; 15; 16]. However, the use of the anhydrous calcined form of the clay mineral kaolinite (metakaolin) was given less attention in loess stabilization. Loess is a widespread surface deposit in many parts of the world. There is a strong need for loess stabilization in construction requirements and geohazard mitigation due to its propensity to collapse and subsidence after loading and wetting [11; 12]. Moreover, unpaved roads in loess are associated with strong erosion by wind and water, which leads to soil disintegration [7]. This study examined the use of a metakaolin-based geopolymer with different compounds and concentrations for the reinforcement of the topsoil of a semi-arid loess soil.