There is a growing concern over elevated CO2 levels and increased metal contamination in soils. Elevated atmospheric CO2\nusually increases plant productivity and alters nutrient elements mobility. However, it is still not clear whether rising CO2\ncan result in changes in contaminating elements in crops, for example in different rice cultivars. Therefore, in this study, a\npot experiment was conducted to investigate the combined effects of CO2 elevation levels and metals (Cu and Cd) on rice\ngrowth. The study showed that elevated CO2 led to higher tiller number, root length and grain yield when compared to\nambient CO2. Average Cu concentrations in the tissues of four rice cultivars with elevated CO2 levels were significantly\nlower than those with ambient CO2. The Cd concentrations in three parts of rice cultivars subjected to elevated CO2 levels\nwere higher than those in plants subjected to ambient CO2 levels. In addition, CO2 elevation significantly reduced the pH\nvalues of soils and changed the fractionation of Cu and Cd in soils. The associated risk was assessed using the hazard\nquotient (HQ), which was found to be high for Cd and Cu in all tested varieties of rice, with Cd posing a more severe threat\nthan Cu.
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