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文摘
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汞是引人注目的全球性污染物,植被叶片吸收是大气汞的主要去除途径之一.然而,当前对于大气-植被叶片汞通量交换过程及吸收后的汞在植被体内的归趋等认识尚有不明确之处.本文利用单一大气汞同位素标记技术,测定了大气汞浓度为0、2、5、10 ng·m~(-3)时,C_3植物水稻与C_4植物玉米叶片汞交换通量的变化特征,并分析了标记的汞同位素在植被体中根-茎-叶的分布比例.结果表明:(1)水稻和玉米叶片汞的沉降通量与大气汞浓度呈显著正相关关系;(2)植物叶片汞的沉降通量有明显的昼夜变化,水稻和玉米的吸收通量白天均高于晚上;(3)玉米对大气汞的补偿点白天为0.63 ng·m~(-3),夜间为2.85 ng·m~(-3);水稻白天为1.24 ng·m~(-3),夜间为1.32 ng·m~(-3),水稻对大气汞的富集能力强于玉米,但二者的补偿点均显著低于国内大气汞浓度;(4)植被从大气吸收的汞主要集中在植物地上部,水稻叶片分布88.92%,茎中分布11.08%,而玉米叶片分布90.95%,茎中分布7.09%,根中分布1.96%.这些结果表明,农田系统的植被能富集大气中的汞,并主要贮存在叶片内部,向茎、根迁移量较少,是大气汞的重要汇.上述结论为进一步估算中国农田系统的大气汞汇与认识汞在大气-叶片-茎-根-土壤中循环提供了科学依据. |
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其他语种文摘
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Mercury (Hg) is a global pollutant. Uptake of atmospheric Hg by foliage is considered to be the major pathway for scavenging Hg from atmosphere. Currently,there are still knowledge gaps in atmosphere-foliage flux exchange processes,and the ultimate fate of the Hg uptake by foliage. Therefore,we used a single mercury (~(202)Hg~0) labelling technique to characterize processes of atmosphere-foliage Hg flux exchange,and distribution of absorbed Hg in the plants of rice (C_3 plant) and maize (C_4 plant). Results shown that Hg uptake by plant was significantly correlated to the atmospheric Hg concentration under the spike 0,2,5,and 10 ng·m~(-3 202)Hg~0 concentrations. In addition,the atmosphere-foliage Hg flux exchange exhibited a distinct diurnal variation,and much higher uptake rates were observed during the daytime. Based on the relationship between the flux and atmospheric Hg concentration,we calculated that the atmospheric Hg compensation point for corn was 0.63 ng·m~(-3) during daytime and 2.85 ng·m~(-3) during nighttime,and for rice was 1.24 ng·m~(-3) during daytime and 1.32 ng·m~(-3) during nighttime,suggesting rice has higher ability of atmospheric Hg accumulation. Both compensation points were significantly lower than domestic regional atmospheric mercury concentration. Finally,we obtained the distribution data for the uptake Hg in the plant organs. Both corn and rice exhibited that the uptake Hg was predominantly distributed in the foliage (90.95% for corn,and 88.92% for rice),followed by the stem (7.09% for corn,and 11.08% for rice),and lowest in the root (1.96% for corn,and ~ 0 for rice). Our results indicate that the vegetation in the farmland of China acts as an atmospheric Hg sink due to lower composition point when compared to the atmospheric Hg concentration,and the transport of Hg through leafstem-root is very difficult. Overall,it provides some insight into the estimation of Hg sink in cropland ecosystems in China,and Hg transport and accumulation in the atmosphere-foliage-soil ecosystems. |
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来源
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环境化学
,2018,37(3):419-427 【核心库】
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DOI
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10.7524/j.issn.0254-6108.2017080902
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关键词
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汞同位素标记
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大气-植被
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交换通量
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汞分配特征
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地址
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1.
中国科学院地球化学研究所, 环境地球化学国家重点实验室, 贵阳, 550081
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中国科学院大学, 北京, 100049
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Lamar大学土木工程学院, USA, Beaumont Texas
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语种
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中文 |
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文献类型
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研究性论文 |
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ISSN
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0254-6108 |
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学科
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环境科学基础理论;环境污染及其防治 |
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基金
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国家973计划
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国家自然科学基金重点项目
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中国科学院贵阳地球化学研究所环境地球化学国家重点实验室基金
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文献收藏号
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CSCD:6220269
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