Contamination characteristics of uncultivated arable lands and health risk warning based on the predicted heavy metal content in rice—Dongting Lake Basin, China

An arable land shortage is emerging due to soil pollution and a growing population, with many cultivated areas experiencing high-intensity utilisation. Uncultivated arable land (UAL) represents a potential resource, essential for safeguarding future food supply. However, the contamination characteristics and risks of heavy metals (HMs) in UAL remain unclear, hindering safe crop production when UAL is activated for farming. A total of 52 soil samples of UAL were collected in the Dongting Lake Basin, China, to assess contamination levels and potential risks of HMs. The study found that Cd (1.11 mg⋅kg⁻¹) and As (43.48 mg⋅kg⁻¹) were the primary pollutants responsible for ecological and occupational health risks in UAL of the Dongting Lake Basin, which were derived from industrial and agricultural sources, respectively. Should these UAL be reclaimed for rice production, dietary exposure to HMs would pose significant non-carcinogenic and unacceptable carcinogenic risks based on predictive models utilising the bioavailable HM content in the soil. According to the predicted content of HMs in rice and the total amount of HMs in soil, UAL was categorized into four groups (reclamation, reclamation after restoration, ecological remediation, and strict control). To ensure the safety of rice production, it is suggested that UAL in the west and south of Dongting Lake Basin could be reclaimed after ecological monitoring and restoration, while UAL in the east of the study area was classified as requiring strict control. This study provides support for reasonable reclamation and risk assessment of UAL.