中国科学院生态环境研究中心机构知识库
Advanced  
RCEES OpenIR  > 大气环境科学实验室  > 学位论文
题名: 同位素示踪研究气态甲基汞对水稻甲基汞富集的影响
作者: 孙婷
学位类别: 硕士
答辩日期: 2016-04
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: a stable isotope addition technique ; 同位素示踪 ; open top chambers experiment ; 开顶气室熏蒸实验 ; atmospheric methylmercury ; 气态甲基汞 ; rice ; 水稻 ; methylmercury accumulation ; 甲基汞富集
其他题名: Investigating the influence of Gaseous Methylmercury on accumulation of Methylmercury in Rice(Oryza sativa L.) Using a Stable Isotope Tracer Technique
学位专业: 环境科学
中文摘要:     甲基汞(MeHg)具有很强的神经毒性,因而被人们广泛关注。在汞污染地区,水稻中 MeHg的含量已经受到影响,因此,认清水稻中  MeHg的来源与富集特征对人体健康和生态系统的风险评估具有重要意义。目前,尚未有水稻MeHg直接大气来源的研究报道。本文采用同位素示踪技术,并结合开顶气室熏蒸 (open  top  chambers,OTCs)实验和土壤加汞培育实验(soil  Hg  enriched experiment),研究水稻各部位对气态甲基汞浓度的响应关系,进而探讨气态甲基汞是否是水稻 MeHg的一个大气来源。此外,本文还研究了气态单质汞(GEM)对水稻 MeHg富集的影响。结果如下:
    建立了可连续产生浓度低、发生效率高的气态二甲基汞(DMeHg)发生系统。即在甲基钴胺素(MeCo):标准汞溶液(Hg2+)的质量浓度比为  10:1,盐度(0-0.01 mol•L-1),pH=4及载气流速为  20 mL•min-1的条件下,通过改变标准汞溶液的浓度及反应温度来获得浓度低且相对稳定的气态 DMeHg。结果为:9℃条件下,0.025  mg•L-1、0.015  mg•L-1 的汞标准溶液与  MeCo  反应得到的气态DMeHg的产生速率在  0-40  h内缓慢上升,在40-140  h期间基本趋于稳定,产生速率分别维持在 300 pg•min-1和150 pg•min-1;在  18℃条件下,0.025 mg•L-1、0.015 mg•L-1的Hg2+溶液产生 DMeHg的速率在  0-50 h内缓慢上升,在50-130 h期间基本趋于稳定,产生速率分别维持在  500  pg•min-1和 300pg•min-1。气态DMeHg的发生系统为系统研究气态甲基汞对水稻各部位  MeHg富集的影响,提供了可靠的技术支撑。
    发现了气态甲基汞是水稻各部位中 MeHg的大气来源。本部分利用稳定同位素(199Hg2+)示踪技术,并结合开顶气室熏蒸实验和土壤加汞培育实验,研究气态甲基汞对水稻 MeHg富集的影响及  MeHg在水稻各部位中的迁移。结果表明水稻各部位中同位素标记的 Me199Hg 的含量与气态甲基汞(199Hg2+标记)的浓度显著正相关(R=0.8993~1, p<0.05),表明气态甲基汞是水稻各部位  MeHg的重要来源;此外,水稻各部位中同位素标记的 Me199Hg浓度占总  Me199Hg(包括来自环境中的 Me199Hg 和同位素标记的 Me199Hg)浓度的比例随气态甲基汞浓度的增加和生长期的延长不断增加,且在 3200pg•m-3的气态甲基汞浓度熏蒸条件下成熟期的水稻,比例接近 100%,表明气态甲基汞对水稻各部位中MeHg富集的贡献随气态甲基汞浓度的增加和生长期的延长不断增加,且在3200pg•m-3  的气态甲基汞浓度熏蒸条件下的成熟期的水稻,水稻各部位中的MeHg主要来自大气。值得关注的是,在OTCs实验中,水稻精米和糙米中MeHg的含量及气态甲基汞对水稻精米和糙米 MeHg富集的贡献值基本一致,表明精米具有很强的 MeHg富集能力,籽粒中的  MeHg主要富集在精米中。水稻对空气中  MeHg 的富集是一个“吸收-转移-累积”的动态过程。对不同气态甲基汞浓度熏蒸下的水稻不同生长阶段各部位 MeHg含量的分析发现:水稻成熟前,茎叶从空气中吸收气态甲基汞;在成熟期间,茎和叶中的 MeHg则被转移、富集至精米中。
    发现了GEM 对水稻各部位中  MeHg  的富集没有显著的影响。水稻根中MeHg的含量与与GEM 含量无线性关系(p>0.05),与土壤中 MeHg的含量明显正相关(R=0.9462-0.9870, p<0.05),表明在 GEM熏蒸实验中,GEM对水稻根中  MeHg 的富集影响不明显,水稻根中的  MeHg  主要来自土壤。水稻茎中MeHg的含量随土壤  MeHg含量的增加而线性增加(上部茎:R=0.8560,p>0.05;下部茎:R=0.9178-0.9484,p<0.05),与GEM 含量没有明显的相关性(p>0.05),但在气室熏蒸实验中上部茎中 MeHg的含量高于下部茎;而在土壤加汞培育实验中下部茎 MeHg 的含量高于上部茎,表明在 GEM 熏蒸实验中,GEM可能对水稻上部茎 MeHg的富集有一定的影响,但水稻茎主要受土壤汞的影响。水稻叶中 MeHg含量与土壤  MeHg含量显著相关(R=0.9708,  p<0.01),与 GEM含量无线性关系,但在气室熏蒸实验中实验组叶中 MeHg的含量高于对照组,表明水稻叶中的  MeHg 可能受  GEM 的影响。水稻籽粒中 MeHg  的含量与土壤MeHg呈显著正相关(R=0.9046-0.9865,p<0.05),与  GEM含量无明显的线性关系(p>0.05),表明在 GEM 熏蒸实验中,GEM 对水稻籽粒中 MeHg  的富集影响不明显,水稻籽粒中的 MeHg主要来自土壤,但在水稻上部茎和叶中MeHg的含量受一定程度大气汞含量影响的情况下势必会对水稻籽粒甲基汞的富集产生影响,究竟多大程度或量化其贡献还需进一步实验研究。
英文摘要:   Methylmercury (MeHg)  is known as  its highly hypertoxicity. In  areas polluted by mercury,  the MeHg concentration  in rice  has be  influenced, therefore, it  is very significant  to  figure  out the  sources  and  accumulation  of  MeHg  in  rice  for risk assessment  of  human  health  and ecosystem.  There  is  no  report  about  the  direct atmospheric source of MeHg in rice at  present. In this study, a stable isotope(199Hg2+)addition technique was used, combined with field open top chambers(OTCs) and soil mercury enriched experiments  to study the response  of MeHg accumulation in  each rice part  to the  gaseous MeHg  concentration, and  then to figure  out if  the gaseous MeHg is an atmospheric source of rice MeHg. Results showed that:
      We established a system which can continuously produce low concentration and high efficiency of gaseous  DMeHg. In this study, when  the mass concentration ratio of  methylcobalamin(MeCo)   and  standard   mercury  solution(Hg2+)=10:1,   salinity (0-0.01  mol•L-1),   pH=4.0  and   carrier  gas   flow  rate   at  20  mL•min-1,   DMeHg
generation  rates  of  0.025  mg•L-1 and  0.015  mg•L-1  mercury concentrations  were increasing slowly  during 0-40 h  and stable during  40-140 h, and  maintaining about 300  pg•min-1  and150  pg•min-1  at  the  temperature  of  9℃,and  the  rates of  0.025 mg•L-1 and 0.015 mg•L-1 mercury concentrations were increasing slowly during 0-50
h and stable  during 50-130 h,  and maintaining about  500 pg•min-1 and300  pg•min-1 at  the  temperature  of  18℃.Therefore  this  system  can  continuously  produce low concentration and  high efficiency of  gaseous DMeHg, and  is safe  and reliable.This DMeHg generation system is  benefit to further research the effect  of gaseous MeHg
on rice MeHg accumulation.
    We discovered  that gaseous  MeHg is  an atmospheric source  of MeHg  in eath rice part.  A stable  isotope  (199Hg2+) addition  technique,  combined with  OTCs and soil Hg enriched  experiments were used to study  the influence of gaseous MeHg  on rice MeHg accumulation, and MeHg translation in eath  rice part. The results showed that  MeHg concentrations  spiked  by   199Hg2+  in eath  rice  parts  were significantly correlated with gaseous MeHg  concentrations (R=0.8993~1,p<0.05), suggesting that gaseous  MeHg was  important  atmospheric source  of  MeHg in  eath  rice  parts; In addition, the  ratio of  MeHg concentration  spiked by  199Hg2+  and total  Me199Hg  in eath rice  part(include Me199Hg  which came  from surrounding  and Me199Hg  spiked by  199Hg2+)  was increasing with  the gaseous  MeHg concentration  and extension of growth period,  in addition,  when the  gaseous MeHg  concentration was  3200pg/m3 and the  growth period  was ripening stage,  the ratio  was gradually closed  to 100%,indicating  that  with  the  gaseous  MeHg  level  increasement  and  the extension  of growth period, the contribution of gaseous MeHg to MeHg accumulation  in eath rice parts was increased,  and when the gaseous  MeHg concentration was 3200pg/m3  and the growth  period  was ripening  stage, MeHg  in eath  rice parts  were  mainly came from  armosphere;  To  be  noticed,  in  OTCs  experiment,  MeHg  concentrations  in polished and  unpolished rice  grain and  the ratio  of MeHg  concentration spiked  by 199Hg2+  and total  Me199Hg in eath  rice parts  was  almost consistent,  indicating that polished rice  grain has  strong ability of  MeHg accumulation, and  grain MeHg  was mainly  accumulated  in polished  grain.  MeHg  accumulation  in  rice is  a  dynamic process,  which  include  absorption,transfer  and  accumulation.  The  analyzation  to MeHg concentrations in  eath rice parts of different  growing seasons and in different gaseous MeHg  concentrations fumigation  showed that,  leaf and  stem could  absorb gaseous MeHg before ripening stage, and  most of MeHg in leaf, stem was translated to rice grain during the ripening stage.
    We discovered  that  there were  no obvious  influences of  GEM on  rice  MeHg accumulation.  MeHg levels  in  root  were  significantly  correlated with  soil  MeHg concentrations (R=0.9462-0.9870, p<0.05)  but insignificantly correlated with air  Hg concentrations (p>0.05), indicating that MeHg in rice root was mainly from soil. The
MeHg  concentrations  in  stem  increased  linearly  with  soil   MeHg  concentrations (upper  stem:R=0.8560,p>0.05;bottom   stem:R=0.9178-0.9484,p<0.05),  and   no obvious linear  correlation with  the GEM.  However, MeHg concentrations  in upper stem  were generally  higher  than  those in  bottom  stem  in  OTCs experiment,  and MeHg levels in bottom stem  were usually higher than that in upper stem,  suggesting that MeHg  in stem was  mainly from soil,  and the  upper stem might  be affected by the GEM. MeHg concentrations in leaf  were significantly correlated with soil MeHg (R=0.9708, p<0.01),  and did  not linearly  correlate with air  Hg (p>0.05).  However,the  MeHg concentrations  in  these experimental  groups  were higher  than  those in control group in OTCs experiment, indicating that MeHg in  leaf might be influenced by  both   soil  MeHg  and   air  Hg.   MeHg  concentrations  in   grain  were   linearly correlated with soil  MeHg concentrations (R=0.9046-0.9865, p<0.05),  and were not linearly  correlated  with  air  Hg(p>0.05).  Moreover,  view  of  the  effects  of  GEM accumulation  in   upper  stem   and  leaf,   it  certainly   will  impact   on  the   MeHg accumulation  in  rice  grain.  However,  the quantification  of  the  effect  need  more research work.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36957
Appears in Collections:大气环境研究室_学位论文

Files in This Item:
File Name/ File Size Content Type Version Access License
孙婷--大气中汞浓度水平对典型农作物甲基汞富集的影响研究.pdf(2089KB)学位论文--限制开放 联系获取全文

Recommended Citation:
孙婷. 同位素示踪研究气态甲基汞对水稻甲基汞富集的影响[D]. 北京. 中国科学院研究生院. 2016.
Service
Recommend this item
Sava as my favorate item
Show this item's statistics
Export Endnote File
Google Scholar
Similar articles in Google Scholar
[孙婷]'s Articles
CSDL cross search
Similar articles in CSDL Cross Search
[孙婷]‘s Articles
Related Copyright Policies
Null
Social Bookmarking
Add to CiteULike Add to Connotea Add to Del.icio.us Add to Digg Add to Reddit
所有评论 (0)
暂无评论
 
评注功能仅针对注册用户开放,请您登录
您对该条目有什么异议,请填写以下表单,管理员会尽快联系您。
内 容:
Email:  *
单位:
验证码:   刷新
您在IR的使用过程中有什么好的想法或者建议可以反馈给我们。
标 题:
 *
内 容:
Email:  *
验证码:   刷新

Items in IR are protected by copyright, with all rights reserved, unless otherwise indicated.

 

 

Valid XHTML 1.0!
Copyright © 2007-2017  中国科学院生态环境研究中心 - Feedback
Powered by CSpace