Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130012, China.
Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130012, China; University of Chinese Academy of Sciences, Beijing 100049, China.
J Environ Sci (China). 2022 Sep;119:50-58. doi: 10.1016/j.jes.2021.12.007. Epub 2021 Dec 21.
Soil macroinvertebrates as ecosystem engineers play significant, but largely ignored, roles in affecting mercury (Hg) cycle by altering soil physical-chemical properties. Ant is likely expanded into boreal mires with climate warming, however, its impacts on Hg cycle remained poorly understood. We compared total Hg (THg) and methylmercury (MeHg) contents in soils from antmounds (Lasius flavus) and the nearby ambient in a boreal mire in Northeast China. The present work seeks to unravel factors that controlling MeHg levels in case of ant appearance or absence. The average THg was 179 µg/kg in the ant mound and was 106.1 µg/kg in nearby soils, respectively. The average MeHg was 10.9 µg/kg in the ant mound and was 12.9 µg/kg in nearby soils, respectively. The ratios of MeHg to THg (%MeHg) were 7.61% in ant mounds and 16.75% in nearby soils, respectively. Ant colonization caused THg enrichment and MeHg depletion, and this change was obvious in the 10-20 cm depth soil layer where ants mainly inhabited. Spectrometry characteristics of soil dissolved organic matter (DOM) exert a stronger control than microorganisms on MeHg variation in soils. A structural equation model revealed that the molecular weight of DOM inhibited MeHg irrespective of ant presence or absence, while humification conducive to MeHg significantly in ant mound soils. Microorganisms mainly affected Hg methylation by altering the molecular weight and humification of DOM. We propose that the effects of ant colonization on MeHg rested on DOM feature variations caused by microorganisms in boreal mires.
土壤大型无脊椎动物作为生态系统工程师，通过改变土壤物理化学性质，在影响汞（Hg）循环方面发挥着重要但在很大程度上被忽视的作用。随着气候变暖，蚂蚁可能会扩展到北方泥炭地，但它们对 Hg 循环的影响仍知之甚少。我们比较了中国东北北方泥炭地蚂蚁丘（Lasius flavus）及其附近土壤中的总汞（THg）和甲基汞（MeHg）含量。本研究旨在揭示在有或没有蚂蚁存在的情况下控制 MeHg 水平的因素。蚂蚁丘中的平均 THg 为 179µg/kg，附近土壤中的平均 THg 为 106.1µg/kg。蚂蚁丘中的平均 MeHg 为 10.9µg/kg，附近土壤中的平均 MeHg 为 12.9µg/kg。蚂蚁丘中的 MeHg 与 THg 的比例（%MeHg）分别为 7.61%和 16.75%。蚂蚁的定殖导致 THg 富集和 MeHg 耗尽，这种变化在蚂蚁主要栖息的 10-20cm 土壤层中更为明显。土壤溶解有机质（DOM）的光谱特征对 MeHg 变化的控制作用强于微生物。结构方程模型表明，DOM 的分子量抑制了 MeHg 的形成，而有利于 MeHg 的形成，这在蚂蚁丘土壤中更为明显。微生物主要通过改变 DOM 的分子量和腐殖化程度来影响 Hg 甲基化。我们提出，蚂蚁定殖对 MeHg 的影响取决于微生物引起的 DOM 特征变化。
