Absorption, accumulation, and distribution of atmospheric metals in rice (Oryza sativa L.)

Crop metal contamination caused by atmospheric metal pollution has been increasingly reported. To investigate the absorption, accumulation, and distribution of atmospheric metals in rice (Oryza sativa L.), a field experiment was conducted with rice grown at an atmospheric metal pollution site and a background site. The concentrations of Pb, Cd, Cu, Mn, and Zn in the atmospheric deposition at the pollution site were significantly higher than those at the background site. Consequently, the rice tillering number decreased by 56–64% and the yield decreased by 53–69% at the pollution site compared to the background site. Particularly, Pb isotope analysis found that 76% of the Pb in the rice grain at the pollution site was attributed to atmospheric Pb. Furthermore, observations by transmission electron microscopy found penetration through the leaf cuticle seems to be the primary pathway for the absorption of atmospheric metals. Using laser ablation inductively coupled plasma-mass spectrometry, it was found that the distribution of metals in rice grains at the two sites was similar, with Pb, Cr, Fe, Mn, Cu, and Ca mainly in the bran layer while Cd and Zn uniformly distributed throughout the entire grains. Possible solutions to address atmospheric metal pollution in crops are discussed.