Duan Gui-Lan, Wang Fang, Cen Kuang, Wang Bo-Xun, Cheng Wang-da, Liu Yue-Chuan, Zhang Hong-Mei
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
Huan Jing Ke Xue. 2017 Sep 8;38(9):3927-3936. doi: 10.13227/j.hjkx.201703185.
Cadmium (Cd) is classified as a Group-1 human carcinogen and rice consumption constitutes a major source of dietary intake of Cd for populations whose staple food is rice. Straw incorporation is widely performed in Cd-contaminated paddy fields, which may significantly affect the bioavailability of Cd in soil and the distribution of Cd in rice plants, consequently altering Cd accumulation in rice grains. In this study, both pot and field trials were conducted to investigate the effects of different amounts of straw incorporation (0.0%, 1.0%, 2.5%, and 5.0%) on Cd sub-cellular distribution in rice plants and Cd accumulation in rice grains. The results showed that Cd was mainly sequestered in cell wall, accounting for 86%-95% and 30%-51% of total cadmium in root and shoot cells, respectively. In shoot cells, about 35%-61% of Cd was distributed in cellular soluble fractions. When rice straw was incorporated at 1.0% and 2.5% levels, Cd sequestration in the cell wall significantly increased and Cd translocation from roots to shoots significantly decreased. However, when rice straw was incorporated at the 5% level, Cd sequestration in root cell walls significantly decreased and Cd translocation from roots to shoots significantly increased at the tillering stage. At the filling stage, 5% rice straw incorporation still significantly increased Cd sequestration in root cell walls and Cd translocation from roots to shoots did not significantly change. The rice straw and rape straw used for the field trail contained high concentrations of Cd (0.49 and 0.67 mg·kg, respectively). Rape straw incorporation alone or together with lime did not significantly affect Cd accumulation in brown rice or rice straw. Rice straw incorporation alone did not significantly affect Cd accumulation in brown rice or rice straw, while incorporation with lime significantly decreased Cd accumulation in both brown rice and rice straw. Biochar application can also significantly reduce Cd accumulation in rice and when biochar was added together with lime, the reduction in Cd accumulation in rice was more significant. Therefore, at Cd-contaminated paddy fields, rice straw or rape straw is not suggested to be returned directly; incorporation with lime would be better for reducing Cd accumulation in rice grains. The results of this study will provide theoretical and practical guidance for the safe production of rice and for straw recycling at Cd-polluted paddy fields.
镉（Cd）被列为第1类人类致癌物，对于以大米为主食的人群而言，食用大米是膳食中镉摄入的主要来源。在受镉污染的稻田中广泛进行秸秆还田，这可能会显著影响土壤中镉的生物有效性以及镉在水稻植株中的分布，进而改变镉在稻谷中的积累。在本研究中，进行了盆栽试验和田间试验，以探究不同秸秆还田量（0.0%、1.0%、2.5%和5.0%）对水稻植株中镉的亚细胞分布以及稻谷中镉积累的影响。结果表明，镉主要螯合在细胞壁中，分别占根细胞和地上部细胞总镉含量的86% - 95%和30% - 51%。在地上部细胞中，约35% - 61%的镉分布在细胞可溶性组分中。当秸秆还田量为1.0%和2.5%时，细胞壁中镉的螯合显著增加，镉从根部向地上部的转运显著减少。然而，当秸秆还田量为5%时，分蘖期根细胞壁中镉的螯合显著减少，镉从根部向地上部的转运显著增加。在灌浆期，5%的秸秆还田仍显著增加根细胞壁中镉的螯合，且镉从根部向地上部的转运没有显著变化。用于田间试验的稻草和油菜秸秆含有高浓度的镉（分别为0.49和0.67 mg·kg）。单独施用油菜秸秆或与石灰一起施用对糙米或稻草中镉的积累没有显著影响。单独施用稻草对糙米或稻草中镉的积累没有显著影响，而与石灰一起施用则显著降低了糙米和稻草中镉的积累。施用生物炭也能显著降低水稻中的镉积累，当生物炭与石灰一起添加时，水稻中镉积累的降低更为显著。因此，在镉污染的稻田中，不建议直接还田稻草或油菜秸秆；与石灰一起施用对减少稻谷中镉的积累会更好。本研究结果将为镉污染稻田的水稻安全生产和秸秆循环利用提供理论和实践指导。
