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题名: 原位研究水稻中汞的富集与大气/土壤来源
作者: 陈剑
学位类别: 硕士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 王章玮
关键词: 开顶式气室,气态单质汞,生理指标,水稻,CO2,open-top chamber, GEM, physiological indexes, rice, CO2
其他题名: Research in situ on accumulation and air/soil origination of mercury in rice
学位专业: 环境工程
中文摘要:     大气汞作为一种全球污染物,对其源和汇的认识仍存在很多不确定性,陆地植被是大气汞重要的源,也可能是大气汞缺失的汇,而汞循环中的一个中心问题是植物中的汞是来自大气还是土壤。农作物是陆地植被的重要组成部分,研究农作物中汞的来源与富集对汞的生物地球化学循环具有重要意义。本文采用开顶式气室气态单质汞熏蒸实验和土壤加汞培育实验,原位研究水稻各器官汞富集对大气/土壤汞浓度和  CO2浓度升高的响应关系,以及对水稻叶片气体交换参数和生理生化指标的影响。结果如下:
    在每一个生长时期,水稻根中汞含量与土壤汞含量呈显著正相关(R=0.9779~0.9998, P<0.05),但随生长时期的延长而降低,与大气汞浓度无显著相关性(P>0.05),表明水稻根中汞主要来自于土壤。水稻茎中汞含量随大气汞浓度的升高呈线性增加(下部茎 RB=0.9872~0.9998,上部茎 RU=0.9779~0.9987, P<0.05),上部茎中汞含量要高于下部茎,随生长时期的延长先降低后升高;茎中汞含量随土壤汞含量的升高呈二次拟合线性增加(分蘖期R=0.9772,下部茎RB=0.9855~0.9999,上部茎RU=0.9986~0.9998, P<0.05),上部茎中汞含量低于下部茎,随生长时期的延长持续降低,表明水稻茎中汞含量受大气和土壤汞的共同影响,但大气汞对其影响更大。水稻叶中汞含量随大气汞浓度的升高呈显著正相关(R=0.9998~0.9999,  P<0.05),且随生长期的延长而增加,在生长前期随土壤汞含量的增加呈二次拟合线性增加(分蘖期R=0.9707,拔节期 R=0.9866, P<0.05),在生长后期与土壤汞含量无显著相关性(P>0.05),但在高汞处理下叶片汞含量显著高于对照,表明水稻叶中汞主要来自于大气,有很少一部分来自于土壤。水稻米粒中汞含量与大气汞浓度无显著相关性(P>0.05),谷壳和乳熟稻穗中汞含量随大气汞浓度升高而增加。利用实验建立的函数关系对水稻地上生物质中汞的大气来源进行估算,水稻叶中至少60%~94%的汞来自大气,上部茎中至少 64%~85%的汞来自大气,而大气对下部茎的贡献为 66%~83%,由此表明水稻地上部分生物质中的汞主要来自于对大气汞的吸收。
    随大气汞浓度的升高,扬花期水稻叶片净光合速率(Pn)、气孔导度(Gs)和胞间 CO2浓度(Ci)均较对照略微下降,蒸腾速率(Tr)显著升高(P<0.05),乳熟期各指标无显著差异,除 Ci外均较扬花期低;Pn、Gs、Ci和 Tr在扬花期和乳熟期与土壤汞含量均无显著相关性(P>0.05),表明大气汞对水稻叶片的光合作用、气孔开放程度以及蒸腾生理功能有一定影响,而土壤汞对叶片生理功能无影响。随大气汞浓度升高,拔节期水稻叶片脯氨酸(Pro)含量显著增加(P<0.05),丙二醛(MDA)含量先急剧增加然后降低,在45 ng•m-3 的汞浓度下达到最大,SOD活性先增大,在15 ng•m-3的汞浓度下达到最大后又开始下降;在扬花期,Pro含量随大气汞浓度的升高先增加后下降,且明显比拔节期高,MDA含量和  SOD活性无显著变化,且较拔节期低;在成熟期,Pro含量与MDA含量与大气汞浓度无显著相关性(P>0.05),但在高汞处理下较高;随土壤汞含量的升高水稻叶片中  Pro含量、MDA含量和SOD活性在各生长期均无显著相关性(P>0.05),但在高汞处理和生长后期较高,表明大气汞对水稻叶片的影响比土壤汞更显著,这与叶片中汞的积累有关,且 Pro、MDA和  SOD三者的协同反应使得水稻叶片对汞胁迫产生了抗性。本实验处理水平下大气汞浓度的升高对水稻株高、穗长、有效穗数、结实率、千粒重和生物量均无显著影响。
    随大气中 CO2浓度的升高,水稻根部、茎部、叶部和果实中的汞含量在背景大气汞浓度(5±2 ng•m-3)和较高大气汞浓度(45~50 ng•m-3)下均有降低的趋势,这可能与大气CO2浓度升高降低气孔导度,促进光合作用,增加生物量,引起植物根系的变化,以及与汞的复合作用有关。
英文摘要:       Mercury(Hg) is a global pollutant, and the source/sink of the atmospheric mercury  are still uncertainties. Terrestrial vegetation is an important source of atmospheric mercury, and meanwhile it  could be the  missing sink of  atmospheric mercury. It  is the key  issue in the global Hg cycling whether the  large amount of Hg stored in vegetation  originates from the soil or from the atmosphere.  Crops are an important part of terrestrial vegetation,  therefore the research on the origination and accumulation of Hg in crops is significantly important to biogeochemical  cycling of  mercury. In  this  paper, the  experimental study  in  situ on  the response of mercury enrichment in rice organs  and the impact of gas exchange parameters,physiological and biochemical indexes in  rice foliage to elevated air/soil Hg  and CO2  with open top chambers (OTCs)-gaseous elemental  mercury (GEM) fumigation experiment and soil Hg enriched experiment. Results as follows:
      In  each growth  period, Hg  concentrations  in rice  root were  correlated  significantly (R=0.9779-0.9998, P<0.05) with soil Hg concentrations but decreased with the extension of the  growth  period,  and  insignificantly  (P>0.05)  correlated  with air  Hg  concentrations,indicating  that  Hg in  rice  root  was  mainly  from soil.  Hg  concentrations  in  rice  stems increased  linearly   (Bottom  stem  RB=0.9872-0.9998,  RU=0.9779-0.9987,   P<0.05)  with elevated air Hg  and increased first and  then declined with the  extension of growth period,Hg in the upper stem was usually higher than that in the bottom stem. With elevated soil Hg, Hg concentrations in stems increased by second-order polynomial (Tillering stage R=0.9772,RB=0.9855-0.9999, RU=0.9986-0.9998, P<0.05) and  Hg in upper stem was lower  than that in bottom stem, and  continued to decrease with the extension of  period, indicating that Hg in  stems  affected  synthetically  by air/soil  Hg,  and  air  Hg  was  the  bigger  impact.  Hg concentrations in rice foliage were correlated significantly (R=0.9998-0.9999, P<0.05) with air Hg  and  increased with  the time;  in the  early  growth period,  Hg in  foliage increased polynomially (Tillering stage R=0.9707, Jointing stage R=0.9866, P<0.05) with soil Hg, and insignificantly  correlated   (P>0.05)  with   soil  Hg  in   the  late   growth  period,  but   Hg concentrations in foliage at high soil Hg treatments were significantly higher than that at the control, indicating that  Hg in foliage  was mainly from air  and a small  part was from soil.Base on  the  function of  growth stage  in these  filed experiments,  it  is estimated  that Hg concentrations in foliage, upper-stem and bottom-stem of rice were at least 60%-94%, 64%-85% and  66%-83% from air  respectively, therefore  Hg in rice  aboveground biomass  was mainly contributed from the atmosphere.
    In  flowering  stage,  net  photosynthesis   rate  (Pn),  stomatal  conductance  (Gs)  and intercellular CO2 concentration (Ci) of rice foliage in the  GEM treatment were less slightly than those  in the control,  and transpiration  rate (Tr)  was significantly (P<0.05)  increased with elevated air Hg, and there are no  significant difference for all gas exchange parameter in milk stage, which is lower than those in flowering stage except for Ci; meanwhile, Pn, Gs,Ci, Tr  were insignificantly (P>0.05)  correlated with  soil Hg in  flowering and  milk stage,
indicating  that  air  Hg   had  some  influences  on  photosynthesis,  stomata   opening,  and transpiration physiological functions of rice  foliage, and soil Hg had no effects  on those in rice foliage. Proline(Pro)  concentrations in rice foliage were  increased obviously (P<0.05) with elevated GEM in jointing stage, declined after increasing and reached to the maximum value at 45 ng•m-3 stage among four treatments. The contents of MDAin rice foliage increased first and reached the highest value at 45 ng•m-3  , and then decreased in jointing stage, and it was no significant difference (P>0.05) with  the increase of GEM in  flowering and mature stage. The  activity of SOD in rice foliage  also increased first and then declined at  15 ng•m-3 in jointing stage,in flowering stage, and it was no significant difference (P>0.05) in mature and there was no significant difference (P>0.05) in flowering stage. The contents of Pro and MDA and  the  activity  of SOD  in  foliage  were insignificantly  (P>0.05)  correlated  with elevated soil Hg in each  growth period, and they were little  higher than the control at high Hg treatment and later growth period, indicating that air Hg has the more significant effects than soil Hg to rice foliage, which may be related to the accumulation of Hg in rice foliage, and  the coordinated  response  of Pro,  MDA  and SOD  makes  rice leaves  produce  stress resistance to mercury. At the  level of air Hg treatment  in this experiment, the plant height, ear  length, number  of  effective  panicles,  seed setting  rate,  thousand  kernel weight  and biomass were insignificantly (P>0.05) correlated with elevated air Hg.
    With elevated  air CO2,  Hg concentrations  in rice root,  stems, foliage  and seed  were reduced in the control  (5±2 ng•m-3 ) and high  air Hg treatment (45~50 ng•m-3), which may be related  to that  elevated  CO2 reduced  stomatal conductance,  promoted photosynthesis, increased  biomass and  caused  the changes  of rice  root,  as well  as  the composite  effect between CO2 and mercury.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34462
Appears in Collections:大气环境研究室_学位论文

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Recommended Citation:
陈剑. 原位研究水稻中汞的富集与大气/土壤来源[D]. 北京. 中国科学院研究生院. 2015.
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