## 1 Introduction  
Most studies are related to background values, which can be divided into geochemical background values and environmental background values. The \"Geochemical background\" is proposed to distinguish whether the content of elements in a geological unit or a certain area is normal and whether the data outside the background range are abnormal (positive or negative) data [1]. The study of geochemical background values is an important foundational work in the field of Earth sciences. The concept of geochemical background originated in exploration geochemistry, and was initially proposed for mineral exploration purposes [2]. However, with the rise of environmental science, this concept began to be introduced into the field of environmental geochemistry in the early 21 st century [3]. For exploration geochemistry, the anomaly data may be an indication of the existence of a certain deposit or the element migration caused by alteration process [4]. Unlike its traditional meaning in exploration geochemistry, in environmental geochemistry, geochemical background values typically refer to the concentrations of chemical elements in environmental components that are unaffected by contamination. This reflects the inherent chemical composition characteristics of these elements in their natural state and development in the environment [5; 6]. The term \"geochemical baseline\" was first introduced in the International Geological Correlation Programme (IGCP) [7; 8]. Different scholars have provided similar scientific definitions of this term [9; 10], generally referring to the actual content of specific elements or compounds in surface environmental media at a specific point in time. This definition encompasses both natural background concentrations and contributions from diffusion concentrations caused by human activities. Geochemical background values and baseline values are important parameters for describing the geochemical characteristics of a region, aiding in the understanding and evaluation of natural element contents in a specific area. They contribute to understanding regional geological backgrounds and geological processes [6; 11; 12]. The concept and calculation of geochemical background in this study are primarily based on definitions and methods established in exploration geochemistry. Typically [13; 14], the lower limit of anomalies is used to delineate background regions from anomalous regions [15]. Deserts represent a natural resource, with sand dunes covering over 20 million square kilometers globally, distributed across continents worldwide. Approximately 20% of arid regions and numerous coastal areas are characterized by sand dunes, which further extend to encompass gravel deserts and regions influenced by aeolian erosion, collectively affecting over 40% of the Earth's terrestrial surface subjected to aeolian processes. Due to their close relationship with human habitation environments and rich information on modern surface processes and Earth environmental evolution, deserts are considered an indispensable part of the Earth system and have been consistently studied by the international academic community [16; 17]. In China, the Regional Geological Survey Project was initiated in 1979 and remains the longest-running national survey program of its kind by the Ministry of Natural Resources (formerly the Ministry of Land and Resources). While there has been extensive research on background values of inland water system sediments or soils, large areas of desert regions remain unsampled due to their vast size and difficult accessibility. Consequently, the geochemical background of desert regions in China remains largely unexplored. Given these circumstances, initiating research on background values in desert regions is crucial for subsequent desert studies and holds profound significance.