Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment and Climate, Jinan University, Guangzhou 510632, China.
Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China.
Sci Total Environ. 2024 May 20;926:171809. doi: 10.1016/j.scitotenv.2024.171809. Epub 2024 Mar 19.
Soil cadmium (Cd) can affect crop growth and food safety, and through the enrichment in the food chain, it ultimately poses a risk to human health. Reducing the re-mobilization of Cd caused by the release of protons and acids by crops and microorganisms after stabilization is one of the significant technical challenges in agricultural activities. This study aimed to investigate the re-mobilization of stabilized Cd within the clay mineral-bound fraction of soil and its subsequent accumulation in crops utilizing nitrogen ammonium nitrogen (NH-N) and nitrate nitrogen (NO-N), at 60 and 120 mg kg. Furthermore, the study harvested root exudates at various growth stages to assess their direct influence on the re-mobilization of stabilized Cd and to evaluate the indirect effects mediated by soil microorganisms. The results revealed that, in contrast to the NO-N treatment, the NH-N treatment significantly enhanced the conversion of clay mineral-bound Cd in the soil to NHNO-extractable Cd. It also amplified the accumulation of Cd in edible amaranth, with concentrations in roots and shoots rising from 1.7-6.0 mg kg to 4.3-9.8 mg kg. The introduction of NH-N caused a decrease in the pH value of the rhizosphere soil and stimulated the production and secretion organic and amino acids, such as oxalic acid, lactic acid, stearic acid, succinic acid, and l-serine, from the crop roots. Furthermore, compared to NO-N, the combined interaction of root exudates with NH-N has a more pronounced impact on the abundance of microbial genes associated with glycolysis pathway and tricarboxylic acid cycle, such as pkfA, pfkB, sucB, sucC, and sucD. The effects of NH-N on crops and microorganisms ultimately result in a significant increase in the re-mobilization of stabilized Cd. However, the simulated experiments showed that microorganisms only contribute to 3.8-6.6 % of the re-mobilization of clay mineral-bound Cd in soil. Therefore, the fundamental strategy to inhibit the re-mobilization of stabilized Cd in vegetable cultivation involves the regulation of proton and organic acid secretion by crops.
土壤中的镉（Cd）会影响作物生长和食品安全，通过食物链的富集，最终对人类健康构成威胁。减少稳定化后作物和微生物释放质子和酸引起的镉再活化是农业活动中的重大技术挑战之一。本研究旨在利用氮铵氮（NH-N）和硝酸盐氮（NO-N），在 60 和 120 mg kg 下，研究土壤中粘土矿物结合态固定的镉的再活化及其随后在作物中的积累。此外，研究在不同生长阶段收获根分泌物，以评估其对稳定化镉再活化的直接影响，并评估土壤微生物介导的间接影响。结果表明，与 NO-N 处理相比，NH-N 处理显著促进了土壤中粘土矿物结合态 Cd 向 NHNO-可提取态 Cd 的转化。它还放大了 Cd 在可食用苋菜中的积累，根和茎叶中的 Cd 浓度从 1.7-6.0 mg kg 增加到 4.3-9.8 mg kg。NH-N 的引入降低了根际土壤的 pH 值，并刺激了作物根系产生和分泌有机和氨基酸，如草酸、乳酸、硬脂酸、琥珀酸和 l-丝氨酸。此外，与 NO-N 相比，根分泌物与 NH-N 的联合作用对与糖酵解途径和三羧酸循环相关的微生物基因的丰度有更显著的影响，如 pkfA、pfkB、sucB、sucC 和 sucD。NH-N 对作物和微生物的影响最终导致稳定化 Cd 的再活化显著增加。然而，模拟实验表明，微生物仅对土壤中粘土矿物结合态 Cd 再活化的 3.8-6.6%有贡献。因此，抑制蔬菜栽培中稳定化 Cd 再活化的根本策略涉及对作物质子和有机酸分泌的调节。
