Tungsten (W) bioavailability in paddy rice soils and its accumulation in rice (Oryza sativa)

The aim of this study was to investigate the accumulation characteristics of tungsten (W) by different indica rice cultivars from the soil and to assess the potential risks to human health via dietary intake of W in rice consumption. A total of 153 rice (ear) samples of 15 cultivars and the corresponding surface soil samples were collected from 7 cities in Fujian Province of southeastern China. The available soil W were extracted using H₂C₂O₄·2H₂O-(NH₄)₂C₂O₄·H₂O at pH 3.3). Results showed that the total soil W ranged from 2.03 mg kg^-1 to 15.34 mg kg^-1 and available soil W ranged from 0.03 mg kg^-1 to 1.61 mg kg^-1. The W concentration in brown rice varied from 7 μg kg^-1 to 283 μg kg^-1 and was significantly correlated with the available soil W. The highest mean TF_avail (transfer factor based on available soil W) was 0.91 for Te-you 627 (hybrid, indica rice), whereas the lowest was 0.08 for Yi-you 673 (hybrid, indica rice). The TF_avail decreased with the increase in available soil W, clay content, and cation exchange capacity. The consumption of the brown rice produced from the investigated areas in some cultivars by the present study may cause risks to human health.