Key Laboratory of Karst Georesources and Environment (Guizhou University), Ministry of Education, Guiyang 550025, China; College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China; Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guiyang 550025, China.
Key Laboratory of Karst Georesources and Environment (Guizhou University), Ministry of Education, Guiyang 550025, China.
J Environ Sci (China). 2022 Sep;119:93-105. doi: 10.1016/j.jes.2022.02.023. Epub 2022 Feb 27.
Humus is often used as an organic modifier to reduce the bioaccumulation of heavy metals in plants, but the effects of different humus components from different sources on the fate of mercury (Hg) in paddy fields are still unclear. Here, fulvic acid (FA) and humic acid (HA) extracted from composted straw (CS), composted cow dung (CCD), peat soil (PM) and lignite coal (LC) were used to understand their effects on the methylation and bioaccumulation of Hg in paddy soil by pot experiments. Amendments of both FA and HA largely increased the abundance of Hg-methylating microbes and low-molecular-weight organic matters (e.g, cysteine) in paddy soil. They were also found to change the aromaticity, molecular size and Chromophoric DOM concentration of DOM, and resulted in heterogeneous effects on migration and transformation of Hg. All the FA-amended treatments increased the mobility and methylation of Hg in soil and its absorption in roots. Nevertheless, FA from different sources have heterogeneous effects on transport of Hg between rice tissues. FA-CCD and FA-PM promoted the translocation of MeHg from roots to rice grains by 32.95% and 41.12%, while FA-CS and FA-LC significantly inhibited the translocation of inorganic Hg (IHg) by 52.65% and 66.06% and of MeHg by 46.65% and 36.23%, respectively. In contrast, all HA-amended treatments reduced the mobility of soil Hg, but promoted Hg methylation in soil. Among which, HA-CCD and HA-PM promoted the translocation of MeHg in rice tissues by 88.95% and 64.10%, while its accumulation in rice grains by 28.43% and 28.69%, respectively. In general, the application of some FA and HA as organic modifiers to reduce Hg bioaccumulation in rice is not feasible.
腐殖质通常被用作有机调节剂，以减少重金属在植物中的生物积累，但不同来源的腐殖质成分对稻田中汞（Hg）命运的影响仍不清楚。在这里，我们使用从堆肥秸秆（CS）、堆肥牛粪（CCD）、泥炭土（PM）和褐煤（LC）中提取的富里酸（FA）和腐殖酸（HA），通过盆栽实验来了解它们对稻田中 Hg 甲基化和生物积累的影响。FA 和 HA 的添加大大增加了 Hg 甲基化微生物和低分子量有机物（如半胱氨酸）在稻田土壤中的丰度。它们还改变了 DOM 的芳香度、分子量和发色 DOM 浓度，并对 Hg 的迁移和转化产生了不均匀的影响。所有 FA 处理均增加了土壤中 Hg 的迁移性和甲基化以及其在根系中的吸收。然而，不同来源的 FA 对 Hg 在水稻组织间的迁移具有不同的影响。FA-CCD 和 FA-PM 分别将 MeHg 从根部向水稻籽粒的迁移率提高了 32.95%和 41.12%，而 FA-CS 和 FA-LC 则分别显著抑制了 52.65%和 66.06%的无机 Hg（IHg）和 46.65%和 36.23%的 MeHg 向水稻籽粒的迁移。相比之下，所有 HA 处理均降低了土壤 Hg 的流动性，但促进了土壤中 Hg 的甲基化。其中，HA-CCD 和 HA-PM 分别将 MeHg 在水稻组织中的迁移率提高了 88.95%和 64.10%，而将其在水稻籽粒中的积累率提高了 28.43%和 28.69%。总的来说，将某些 FA 和 HA 作为有机调节剂应用于降低水稻中的 Hg 生物积累是不可行的。
