The soil is the primary source of selenium intake for humans and animals. Investigating selenium's migration from soil to crops and the human body holds significant scientific value in assessing agroecosystems and human well-being. This study analyzes selenium levels in soils, crops, and human hair in Aksu, Xinjiang, a selenium-rich farmland, focusing on the Selenium-Crop-Hair System (SCHS). In Aksu's selenium-rich farmland, soil selenium ranged from 0.09 to 4.60 mg/kg, averaging 0.356 mg/kg. Among crops, average selenium content ranked as follows: wheat (0.084 mg/kg) > rice (0.079 mg/kg) > maize (0.065 mg/kg) > carrot (0.058 mg/kg) > walnut (0.044 mg/kg) > apple (0.042 mg/kg) > jujubes (0.039 mg/kg). Human hair displayed selenium content ranging from 0.34 to 0.57 mg/kg, averaging 0.46 mg/kg. Overall, selenium levels in soils, crops, and human hair fall within selenium-moderate to selenium-sufficient ranges. Comparatively, bioaccumulation factors (BAF) of rice/soil (0.22) and hair/soil (1.28) in Aksu surpass those in other Chinese regions, indicating higher selenium bioavailability in the northwestern, China. Rice and carrots, under intense irrigation, exhibited a strong correlation in selenium content among crops, rhizosphere soil, and background soil. Conversely, weak correlations were observed between the edible part of apples, walnuts, jujubes, wheat, maize, rhizosphere soil, and background soil. Intensively irrigated farmland showed higher selenium content in rhizosphere soil and crops compared to rainfed fields, suggesting that irrigation, potentially coupled with intercropping and residue management, may enhance selenium migration and circulation in soils. However, crop selenium content may be more influenced by biological absorption characteristics.
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