Rare earth elements in soils and cultivated Brassica perviridis from Northern and North Central Vietnam

The critical importance of rare earth elements (REE) for modern industry and agriculture has led to their large-scale release into the environment, raising significant toxicity concerns. Twenty-three soil samples collected across Northern and North Central Vietnam and Brassica perviridis growing on the corresponding soils were analyzed using instrumental neutron activation analysis. In the soil, seven REE (Sc, La, Ce, Nd, Sm, Tb, and Yb) were detected, with contents spanning wide ranges: from Tb (0.159-2.43 mg/kg) to Ce (13.6-147 mg/kg). In plant samples, only La and Sm, with mean values 43 and 2.6 mg/kg, were reliably quantified. The REE patterns indicate a general enrichment of light REEs in the analyzed soils. Depending on the soil properties, this pattern exhibited either positive or negative Ce anomalies. Additionally, positive Sm anomalies were found in the samples collected from Lao Cai (apatite mining area) and Lac Thuy (metal mining area). A La anomaly was found in the samples collected near the large shipping port in Cat Hai, which can be associated with seaport activity. Finally, an assessment of La and Sm accumulation in Brassica perviridis and their potential health risks were evaluated. The results indicate no risk from La through daily vegetable consumption, while assessment of Sm impact cannot be evaluated due to a lack of reference data.