No abstract

Purpose Over-accumulation of cadmium and lead in rice grain is a global concern as it has adverse health impacts. Atmospheric deposition is an important source of heavy metal accumulation in soil, but contribution to crops has not been quanti ed and the mechanisms of foliar Cd and Pb uptake via the stomata of rice leaves exposed to atmospheric fallout are unclear.Methods To quantify the contribution of atmospheric deposition on Cd and Pb accumulation in rice grains, a rice pot experiment with three exposure treatments (T1, all day exposure without geotextile membranes; T2, all day exposure with geotextile membranes; T3, daytime exposure with geotextile membranes; and T4, night exposure with geotextile membranes) using severely (ZZ) and moderately (XT) polluted soils was conducted.Results Cd content in shoots and roots was T1 > T2, T3 > T4 in XT soils, and T1 > T2, T4 > T3 in ZZ soils, while Pb content in both soils was T1 > T2, and T4 > T3. Cd and Pb contents in rice grains showed the same trend. Using the tracer of isotope tracer ratios ( 114/111 Cd, 112/111 Cd, and 207/206 Pb, 208/206 Pb) the contribution of atmospheric deposition to rice grains was quanti ed as 63.55% and 18.01% for Cd, and 27.69% and 41.13% for Pb in XT and ZZ soils, respectively.Conclusions Foliar uptake atmospheric deposition had substantial effect on Cd and Pb accumulation in rice grains and the control of heavy metal foliar uptake should be paid more attention in to maintain rice safety production.

Leafy vegetables cultivated in kitchen gardens and suburban areas often accumulate excessive amounts of heavy metals and pose a threat to human health. For this reason, plenty of studies have focused on low accumulation variety screening. However, identifying specific leafy vegetable varieties according to the foliar uptake of air pollution remains to be explored (despite foliar uptake being an important pathway for heavy-metal accumulation). Therefore, in this study, the lead (Pb) and cadmium (Cd) contents, leaf morphology, and particle matter contents were analyzed in a micro-area experiment using 20 common vegetables. The results show that the Pb content in leaves ranged from 0.70 to 3.86 mg kg−1, and the Cd content ranged from 0.21 to 0.99 mg kg−1. Atmospheric particles were clearly scattered on the leaf surface, and the particles were smaller than the stomata. Considering the Pb and Cd contents in the leaves and roots, stomata width-to-length ratio, leaf area size, enrichment factor, and translocation factor, Yidianhongxiancai, Qingxiancai, Baiyuanyexiancai, Nanjingjiangengbai and Sijixiaobaicai were recommended for planting in kitchen gardens and suburban areas as they have low accumulation characteristics. Identifying the influencing factors in the accumulation of heavy metals in vegetables through foliar uptake is important to help plant physiologists/environmentalists/policy makers to select suitable varieties for planting in air-polluted areas and thus reduce their threat to human health.