| 水稻对气态单质汞的吸收与挥发 |
| 摘要点击 1975 全文点击 637 投稿时间：2017-04-05 修订日期：2017-06-15 |
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| 中文关键词 水稻 气态单质汞 叶面积指数 汞挥发 通气组织 |
| 英文关键词 rice gaseous elemental mercury leaf-area index Hg volatilization aerenchyma |
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| 中文摘要 |
| 湿地是汞的重要富集场所，其还原性底质会促进气态单质汞的产生.湿地植物已进化出一系列适应淹水环境的生态特征，其中发达的通气组织可以从大气向根部输送氧气满足根系的呼吸作用.以水稻这一典型的湿地植物为例，研究其根系及通气组织是否也能成为根际气态汞向大气运输的通道，并探究其过程和影响因素.通过设计密闭分室培养装置将水稻根部与地上部分隔开，对水稻根部进行汞蒸气暴露，并通过气体吸收剂吸收由叶片挥发出的气态汞.结果表明，水稻可以从根系吸收气态单质汞并向地上组织迁移，其中根系的汞含量与水稻根孔隙度呈显著负相关，并呈二次拟合（R=0.8309，P<0.01）；而水稻地上部汞迁移量与水稻根表面积和根体积均呈线性正相关（R=0.896，P<0.01；R=0.871，P<0.01）.由根系吸收的汞最终可通过水稻叶片挥发进入大气，叶片汞的挥发量随着叶片面积的增加呈线性增加（R=0.897，P<0.01），单位叶面积汞挥发量与水稻蒸腾作用强度呈线性显著正相关（R=0.73，P<0.01）.证明了水稻根系不仅能吸收气态单质汞，并且能将汞从根部转运到地上部，再通过叶片的气孔释放到空气中.为进一步揭示湿地生态系统中汞的迁移及调控机制提供了科学依据. |
| 英文摘要 |
| Wetlands are important sinks for mercury, and its reducing substrate favors the production of gaseous elemental mercury. In order to adapt to the anoxic condition, wetland plants usually have developed aerenchyma to transfer oxygen from the shoots to the roots to supply their roots respiration. In this study, a typical wetland plant, rice, is used to investigate whether its aerenchyma can also be a channel for the transportation of rhizosphere gaseous mercury into the atmosphere. In addition, the underlying mechanisms will be evaluated. In this study, the roots of rice were separated from the shoots by an air-tight chamber. Roots were exposed to saturated mercury vapor in the root chamber, and the gaseous mercury volatilized from the leaf chamber was absorbed by an active carbon absorbent. The results showed that gaseous elemental mercury could be transferred to shoots after absorption by the roots. The mercury in the roots decreased polynomially with root porosity (R=0.8309, P<0.01), while the mercury in the above ground tissues showed a positive correlation with root surface area and root volume (R=0.896, P<0.01; R=0.871, P<0.01). It was also indicated that the mercury absorbed by the roots could be volatilized into the atmosphere through the leaves. The volatilization of the mercury from the leaves increased positively with the leaf area (R=0.897, P<0.01). There was also a significant positive correlation between the mercury volatilization per unit leaf area and transpiration intensity (R=0.73,P<0.01). The results proved that rice can absorb gaseous elemental mercury through its roots and transfer it above ground for emission into the atmosphere through the stomata of the leaves. This provides a scientific basis for further investigations to reveal mercury behavior and its mechanisms in wetland ecosystems. |
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