Zhou Jun, Xia Ruizhi, Landis Joshua D, Sun Yufang, Zeng Zhen, Zhou Jing
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Sci Technol. 2024 Oct 1;58(39):17283-17294. doi: 10.1021/acs.est.4c00659. Epub 2024 Jul 27.
Biogeochemical processes of atmospherically deposited cadmium (Cd) in soils and accumulation in rice were investigated through a three-year fully factorial atmospheric exposure experiment using Cd stable isotopes and diffusive gradients in thin films (DGT). Our results showed that approximately 37-79% of Cd in rice grains was contributed by atmospheric deposition through root and foliar uptake during the rice growing season, while the deposited Cd accounted for a small proportion of the soil pools. The highly bioavailable metals in atmospheric deposition significantly increased the soil DGT-measured bioavailable fraction; yet, this fraction rapidly aged following a first-order exponential decay model, leading to similar percentages of the bioavailable fraction in soils exposed for 1-3 years. The enrichment of light Cd isotopes in the atmospheric deposition resulted in a significant shift toward lighter Cd isotopes in rice plants. Using a modified isotopic mass balance model, foliar and root uptake of deposited Cd accounted for 47-51% and 28-36% in leaves, 41-45% and 22-30% in stems, and 45-49% and 26-30% in grains, respectively. The implications of this study are that new atmospheric deposition disproportionately contributes to the uptake of Cd in rice, and managing emissions thus becomes very important versus remediation of impacted soils.
通过一项为期三年的全因子大气暴露实验，利用镉稳定同位素和薄膜扩散梯度技术（DGT），研究了大气沉降镉（Cd）在土壤中的生物地球化学过程及其在水稻中的积累情况。我们的研究结果表明，在水稻生长季节，通过根系和叶片吸收，大气沉降对水稻籽粒中约37%-79%的镉含量有贡献，而沉降镉在土壤库中所占比例较小。大气沉降中生物有效性高的金属显著增加了土壤中DGT测定的生物有效部分；然而，这一部分按照一级指数衰减模型迅速老化，导致暴露1-3年的土壤中生物有效部分的百分比相似。大气沉降中轻镉同位素的富集导致水稻植株中镉同位素显著向更轻的方向偏移。使用改进的同位素质量平衡模型，叶片、茎杆和籽粒中，沉降镉通过叶片和根系吸收分别占47%-51%和28%-36%、41%-45%和22%-30%、45%-49%和26%-30%。本研究的意义在于，新的大气沉降对水稻吸收镉的贡献不成比例，因此与修复受影响土壤相比，控制排放变得非常重要。
