Bioaccumulation and risk assessment of heavy metals in soil-crop systems in Liujiang karst area, Southwestern China

Evaluating the bioaccumulation and health risk of heavy metals in soil-crop systems is essential in Liujiang karst regions. In the current study, the single and comprehensive uptake effects of heavy metals (i.e., Cu, Cr, Cd, As, and Zn) between rice and sugarcane and their rhizosphere soils were investigated. The estimated daily ingestion (EDI), target hazard quotient (THQ), and hazard index (HI) were estimated for health risk assessments. The results showed that the mean contents of Cu, Cr, Cd, As, and Zn in rice soils were 25.8, 168, 1.91, 20.0, and 160 mg/kg, respectively, and those in sugarcane soils were 28.8, 186, 0.44, 31.0, and 108 mg/kg. Rice soils were mainly contaminated by Cd, and Cd and Cr were the main pollutants in sugarcane soils. The average concentrations of Cu, Cr, Cd, As, and Zn in rice grains were 1.79, 0.15, 0.16, 0.11, and 12.7 mg/kg, respectively, and in sugarcanes were 0.10, 0.036, 0.022, 0.006, and 0.38 mg/kg. Both crops tended to take up Cd more effectively, and rice grains exhibited higher accumulation capacities of heavy metals in edible part than sugarcanes. Prediction models of Cd and comprehensive accumulation factors were established for rice and sugarcane, and different soil factors affect metal accumulation in crops cultivated in different types. Due to the exposure to As and Cd through rice consumption, non-carcinogenic risks are likely to occur in Liujiang residents.