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 quantified 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 four 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 isotope ratios tracing method (^114/111Cd, ^112/111Cd, and ^207/206Pb, ^208/206Pb), it can be concluded that the contribution of atmospheric deposition to rice grains was quantified 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 to maintain rice safety production.

Graphical abstract

中文翻译：

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镉的大气沉降贡献及其在稻谷中的积累

目的

稻谷中镉和铅的过量积累是全球关注的问题，因为它会对健康产生不利影响。大气沉降是土壤中重金属积累的重要来源，但对作物的贡献尚未量化，并且通过暴露于大气沉降物的水稻叶片气孔吸收叶面 Cd 和 Pb 的机制尚不清楚。

方法

为了量化大气沉降对水稻籽粒中 Cd 和 Pb 积累的贡献，采用四种暴露处理（T1，无土工膜全天暴露；T2，土工膜全天暴露；T3，土工膜白天暴露; 和 T4，使用严重 (ZZ) 和中度 (XT) 污染的土壤进行夜间土工布膜暴露。

结果

XT土壤中地上部和根部Cd含量为T1>T2、T3>T4，ZZ土壤为T1>T2、T4>T3，Pb含量为T1>T2、T4>T3。水稻籽粒中Cd和Pb含量也呈现出相同的趋势。采用同位素比值示踪法（^114/111 Cd、112 ^{/ 111 Cd、207/ 206} Pb、^208/206 Pb），可以得出大气沉降对稻谷的贡献分别为63.55%和18.01% XT 和 ZZ 土壤中 Cd 和 Pb 分别为 27.69% 和 41.13%。

结论

叶面吸收大气沉降对水稻籽粒中Cd和Pb的积累有显着影响，应加强对重金属叶面吸收的控制，以维护水稻安全生产。

图形概要