Fluorine enrichment of vegetables and soil around an abandoned aluminium plant and its risk to human health

In the process of electrolytic aluminium production, a large amount of fluoride is deposited into the surrounding environment. The growth of crops within these areas creates a state of high stress in plants that can easily result in excessive fluorine enrichment in agricultural products, which in turn poses a health threat to humans via the food chain. However, it is not clear what the degree of influence is or how long the impacts of fluorides in soil and agricultural products last for. In this study, 122 vegetable species and 36 surface soil samples were collected within 10 km of an aluminium plant that had been abandoned for five years. The single factor index and the geological accumulation index methods were used to evaluate the degree of fluorine pollution in vegetables and soil within the study area. The hazard index and the hazard quotient were used to assess vegetable and soil health risks, respectively. The results showed that the fluorine content of 89.26% of agricultural products exceeded the Chinese Maximum Levels of Contaminants in Foods and was higher than in other regions, indicating that the emissions of fluoride from the aluminium plant still had a significant effect on fluorine accumulation in vegetables. The total fluorine (Fₜ) content in the surrounding surface soil (average value 1328.32 mg kg⁻¹) was similar to the soil fluorine background in the nearby uncontaminated settlement area, but the soil water-soluble fluorine (Fw) was very high, indicating that the fluorine pollutants emitted from the aluminium plant had gradually been diluted by the high background of the original soil, but the solubility of these pollutants was higher (average 15.00 mg kg⁻¹) and would continue to threaten the safety of agricultural products in this region. Within 1 km of the abandoned aluminium plant, the degree of fluorine enrichment in vegetables, and Fₜ and Fw in soil were significantly higher than other ranges, indicating that this was the main fluoride deposit area. Based on the HI and HQ evaluation, vegetables and ground dust around the aluminium plant still had high non-carcinogenic risks for children, even though it has been abandoned for more than five years.