Influences of high-level atmospheric gaseous elemental mercury on methylmercury accumulation in maize (Zea mays L.)
Influences of high-level atmospheric gaseous elemental mercury on methylmercury accumulation in maize (Zea mays L.)
复制标题
大气高浓度气态元素汞对玉米（Zea mays L.）甲基汞积累的影响
DOI：
10.1016/j.envpol.2020.114890
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发表时间：
2020
影响因子：
8.9
通讯作者：
Chen Jian
中科院分区：
文献类型：
--
作者：
Sun Ting;Wang Zhangwei;Zhang Xiaoshan;Niu Zhenchuan;Chen Jian
玉米（Zea maysL.）叶片在气孔吸收和表面吸附大气汞（Hg）方面起着重要作用。然而，大气气态元素汞（GEM）对玉米植株中甲基汞（MeHg）积累的影响知之甚少。通过田间开顶箱试验和土壤汞富集试验，研究了玉米组织中甲基汞积累对不同浓度GEM的响应。在OTCs实验中，玉米上部叶的平均甲基汞浓度（0.21 ± 0.08 ng g −1）高于底部叶（0.15 ± 0.05 ng g−1），这与土壤汞富集实验中的结果（玉米上部叶：0.41 ± 0.07 ng g−1，玉米底部叶：0.60 ± 0.05 ng g−1）不一致。玉米叶片中甲基汞浓度与大气汞浓度呈显著正相关，表明大气汞浓度升高促进了玉米叶片中甲基汞的积累，这可能与叶片表面汞的甲基化有关。OTCs实验中成熟玉米籽粒的甲基汞浓度较低（0.12-0.23 ng g−1），表明玉米籽粒积累甲基汞的能力较低。玉米籽粒中93-96%的甲基汞和51-73%的总汞从灌浆期到籽粒成熟期在所有GEM水平处理中损失，这意味着玉米籽粒发生了自我解毒。玉米根中甲基汞含量与土壤汞含量呈显著线性关系（R2= 0.98，p < 0.01），说明玉米根中甲基汞主要来源于土壤。本研究提供了一个新的发现，即大气中高浓度的GEM会增加玉米叶片中甲基汞的积累，玉米籽粒可能会发生自我解毒。汞在玉米叶表面的甲基化和玉米籽粒对汞的自我解毒机制有待进一步研究。
Maize (Zea maysL.) leaves play an important role in stomatal uptake and surface adsorption of atmospheric mercury (Hg). However, the influence of atmospheric gaseous elemental mercury (GEM) on methylmercury (MeHg) accumulation in maize plants is poorly understood. In this study, we conducted a field open-top chambers (OTCs) experiment and a soil Hg-enriched experiment to investigate the response of MeHg accumulation in maize tissues to different GEM levels in the air. Maize upper leaves had a higher average MeHg concentration (0.21 ± 0.08 ng g−1) than bottom leaves (0.15 ± 0.05 ng g−1) in the OTCs experiment, which was inconsistent with that in the soil Hg-enriched experiment (maize upper leaves: 0.41 ± 0.07 ng g−1, maize bottom leaves: 0.60 ± 0.05 ng g−1). Additionally, significantly positive correlations were found between MeHg concentrations in maize leaves and air Hg levels, suggesting that elevated air Hg levels enhanced MeHg accumulation in maize leaves, which was possibly attributed to methylation of Hg on leaf surfaces. Mature maize grains from the OTCs experiment had low MeHg concentrations (0.12–0.23 ng g−1), suggesting a low accumulation capability of MeHg by maize grains. Approximately 93–96% of MeHg and 51–73% of total Hg in maize grains were lost from the grain-filling stage to the grain-ripening stage at all GEM level treatments, implying that self-detoxification in maize grains occurred. MeHg concentrations in maize roots showed a significant linear relationship (R2= 0.98, p < 0.01) with soil Hg levels, confirming that MeHg in maize roots is primarily from soil. This study provides a new finding that elevated air GEM levels could enhance MeHg accumulation in maize leaves, and self-detoxification may occur in maize grains. Further studies are needed to clarify these mechanisms of Hg methylation on maize leaf surfaces and self-detoxification of Hg by maize grains.