Elevated CO2 levels affects the concentrations of copper and cadmium in crops grown in soil contaminated with heavy metals under fully open-air field conditions.

Elevated CO(2) levels and the increase in heavy metals in soils through pollution are serious problems worldwide. Whether elevated CO(2) levels will affect plants grown in heavy-metal-polluted soil and thereby influence food quality and safety is not clear. Using a free-air CO(2) enrichment (FACE) system, we investigated the impacts of elevated atmospheric CO(2) on the concentrations of copper (Cu) or cadmium (Cd) in rice and wheat grown in soil with different concentrations of the metals in the soil. In the two-year study, elevated CO(2) levels led to lower Cu concentrations and higher Cd concentrations in shoots and grain of both rice and wheat grown in the respective contaminated soil. Elevated CO(2) levels slightly but significantly lowered the pH of the soil and led to changes in Cu and Cd fractionation in the soil. Our study indicates that elevated CO(2) alters the distribution of contaminant elements in soil and plants, thereby probably affecting food quality and safety.