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: 我国近海大气汞的时空分布及海-气交换研究
作者: 王纯杰
学位类别: 博士
答辩日期: 2016-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 张晓山
关键词: Atmospheric mercury, Air-sea exchange, Wet and dry deposition, Chinese marginal seas, Changdao ; 大气汞,海-气交换,干湿沉降,中国近海,长岛
其他题名: Spatial-temporal distributions and air-sea exchange of atmospheric mercury in Chinese marginal seas
学位专业: 环境科学
中文摘要:   汞的特殊性质(如长距离输送、迁移转化和强富集性等)使得它成为一种全球性的污染物。大气中汞的物理化学特性和迁移转化过程决定了它们在大气中的存留时间和对环境的效应。大气中的汞按操作上的定义可分为三种形态:气态元素汞(GEM)、活性气态汞(RGM)和颗粒态汞(HgP),大气汞可以通过光致氧化还原等方式从一种形态转化为另外一种形态。由于  GEM  具有较高的挥发性、较低的水溶性和较低的化学特性,所以它在大气中可以长时间(0.3 1年)存留;尽管 RGM和  HgP占大气总汞(TAM)的比例还不到  5%,但它们在大气汞干湿沉降方面发挥着非常重要的作用,而干湿沉降是大气汞进入海洋的重要方式。东亚地区是全球人为汞排放量最大的地区,中国是世界上人为汞排放量最大的国家,由于工业经济的发展,其汞的排放量还在逐年增加。高的人为汞排放量可能会导致我国及周边地区较高的大气汞浓度和干湿沉降通量。然而目前对我国近海大气汞的时空分布及海-气交换的研究还非常有限。
    本研究通过结合海岸站点(长岛气象站)的长期观测和依托科考船对我国近海(黄渤海、东海和南海)的随航观测,系统地研究了我国近海及长岛地区的大气汞及其海-气交换。我们分别于 2013  年的夏季和秋季对东海进行了两次科学考察,于 2014 年的春季和秋季对黄渤海进行了两次科学考察,又于  2015年的秋季对南海进行了一次科学考察。本研究的目的是揭示我国近海不同形态大气汞的时空分布,探讨大气汞与气象参数之间的关系,估算我国近海汞的海-气交换通量和大气汞的干湿沉降通量,最后估算我国近海及长岛地区汞的收支。我国近海的观测结果表明,南海 GEM的浓度(1.52  ± 0.32 ng m3)和一些开阔大洋海域的浓度相当,黄海和东海的浓度稍高于南海的浓度,而渤海的浓度(2.51 3.64 ng m3)明显高于黄海、东海和南海,说明渤海在一定程度上受到了人为污染的影响。长岛地区 GEM的浓度表现出明显的季节变化特征:冬、春、夏、秋四个季节 GEM的浓度依次降低,分别为  3.11 ± 1.89,2.40 ± 1.33,2.31 ± 1.01和  1.96 ± 1.02 ng m−3,说明长岛地区 GEM的浓度和渤海海域的浓度相当,但高于黄海、东海和南海海域的浓度。黄渤海和南海的观测结果显示,黄渤海  RGM  的浓度相差不大,南海海域RGM  的浓度明显高于黄渤海,这可能是由于南海较高的光照和气温有利于RGM 的产生。长岛地区 RGM 的浓度表现出明显的季节变化特征:夏季 >  春秋季  > 冬季,而细颗粒态汞(HgP2.5)的季节变化特征与  RGM  相反。相关性分析结果表明,RGM与光照和气温呈显著正相关关系,而与湿度呈显著负相关关系。此外,研究期间  RGM  的浓度都表现为白天明显高于夜间,说明光照对RGM 的产生有促进作用。渤海 HgP2.5的浓度高于其它海域,HgP2.5的浓度在黄海和南海都表现为近岸高于远海。我们还分析了不同粒径范围内(< 0.4 10 µm,九级)颗粒态汞的浓度,结果表明,总颗粒态汞(用  HgP10  表示)的浓度以及细颗粒态汞(HgP2.1)与 HgP10的比例(即  HgP2.1/ HgP10)都表现为近岸高于远海,说明近岸受人为影响明显;长岛地区 HgP10的浓度高于我国近海,并且  HgP10的浓度和 HgP2.1/ HgP10的值都表现出明显的季节变化特征。
    不管在我国近海还是长岛地区,RGM的干沉降通量都远高于  HgP的干沉降通量,RGM的干沉降通量占  TAM干沉降通量的比例在  85%以上。粗颗粒态汞(HgP2.1 10)在 HgP10的干沉降方面发挥决定作用。长岛观测站  HgP10和 RGM的干沉降通量都高于我国近海,并且长岛  HgP10  的干沉降通量表现出明显的季节变化特征:冬季 > 春季 > 夏季 > 秋季,而 RGM干沉降通量的季节变化特征
与 HgP10相反。我国近海大气 RGM和  HgP10的干沉降通量分别为  5.68和  0.69gm 2 yr 1,长岛大气 RGM和HgP10的干沉降量通量分别为  11.0和1.74   g m2 yr 1。长岛大气汞的湿沉降通量为 1.80 g m2 yr1。
    根据表层海水中溶解性气态汞(DGM)和近海面大气中 GEM的浓度,我们利用气液交换模型估算了我国近海汞(主要为 Hg0)的海-气交换通量。结果表明,Hg0的海-气交换通量在空间上变化不大。长岛近岸海水中  DGM  的浓度和 Hg0的海-气交换通量都表现出明显的季节变化特征:夏季 > 秋季 > 春季 >冬季。东海海域 Hg0的年排放量为  27.6吨,大约占全球海洋年均汞排放量的比例为  0.98%,但是东海的面积占全球海洋面积的比例  0.21%。我们在黄渤海和南海也发现了相似的趋势,即各海域汞排放通量与全球海洋汞排放通量的比例高于各海域面积与全球海洋面积的比例,表明我国近海是大气汞的重要再排放源。
英文摘要:       The special characteristics of mercury (Hg), such as  the long-range atmospheric transport, transformation and biomagnification, and  the role as a neurotoxin, make it a ubiquitous  and  potent pollutant  of global  concern.  Once Hg  is released  into  the atmosphere, its  physical and  chemical properties  and transformation processes  will determine  its subsequent  fate  and  transport. Hg  in  the atmosphere  exists  in  three major operationally  defined  forms: gaseous  elemental Hg  (GEM or  Hg0),  reactive gaseous  Hg  (RGM), and  particulate  Hg  (HgP).  Hg can  be  transformed  from  one species to  another via photo-oxidation,  photo-reduction, reactions with  halides, and other  oxidation   or  reduction   reactions.  Generally,   GEM  is  very   stable  in   the atmosphere  with  a  residence  time  of  0.31  year  due  to  its  high   volatility,  low solubility,  and  chemical  stability.  RGM  and   HgP  play  an  important  role  in  Hg deposition though they  generally account for <  5% of total  atmospheric Hg (TAM),and atmospheric Hg (mainly RGM and  HgP) deposition is identified as the dominant source of  atmospheric Hg to  the ocean.  Atmospheric Hg emissions  from East  Asia were much  higher than  those from  other continents in  global emission  inventories.China is  the largest contributor  to global atmospheric  Hg, where  anthropogenic Hg emissions are likely to further increase with the  development of industrial ecomomy. Higher Hg emissions in China may result  in elevated atmospheric Hg concentrations and deposition  levels, and  then cause Hg  pollution in  the surrounding regions.  But we have little  knowledge on the atmospheric  Hg speciation and air-sea  exchange of gaseous  Hg  in  the Chinese  marginal  seas  due  in  part  to  sparse  data from  these regions.
      Based   on   the   long-term   measurements   at   a   coastal   station   (Changdao Meterological Observatory)  and the  cruises covering  the majority areas  of Chinese marginal seas (i.e., Bohai Sea: BS, Yellow  Sea: YS, East China Sea: ECS, and South China  Sea:  SCS),  this  thesis  systemically  investigated  the  cycling  of  Hg in  the
atmosphere  and  air-sea exchange  of  Hg  in  the  Chinese  marginal seas  (including Changdao  Observatory). Two  oceanographic  cruises  were carried  out  in  the ECS during the summer and fall of  2013; another two oceanographic cruises were carried out in  the BS and  YS during the  spring and  fall of 2014;  finally, an oceanographic cruise was  carried out  in  the SCS  during the  fall of  2015. The  main objectives  of these   cruises   are   to   identify   the   spatial-temporal   distributions    of   speciated atmospheric  mercury  (GEM, RGM,  and  HgP)  in  air,  to  explore the  relationships between speciated  atmospheric Hg  and meteorological  parameters, and  to estimate the air-sea  Hg0 flux  and  the wet  and dry  depositon flux  of atmospheric  Hg  in the Chinese  marginal  seas,  and  finally  estimate the  mass  balance  of  Hg  in  Chinese marginal seas and Changdao Observatory.
     The  measurements  in   the  Chinese  marginal  seas  suggested   that  the  GEM concentrations in the SCS (1.52 ± 0.32 ng m3) were comparable to those of the open oceans, and  the  GEM concentratios  in the  YS  and ECS  were  slightly higher  than those in  the SCS,  while the  GEM  values in  the BS  were significantly  higher than those  in the  YS,  ECS,  and SCS,  indicating  that  the BS  was  polluted.  The  GEM concentrations at  Changdao  exhibited distinct  seasonal  variation with  the order  of winter (3.11 ± 1.89 ng m−3)  > spring (2.40 ± 1.33 ng m−3) > summer  (2.31 ± 1.01 ngm−3)  >  fall (1.96  ±  1.02  ng  m−3).  The results  show  that  GEM  concentrations  at Changdao were  comparable to  those in the  BS, while  higher than those  in the  YS,ECS and SCS.
    The   results   showed   that   there   was   no   significant   difference   in   RGM concentrations  in the  BS  and  YS,  but the  RGM  concentrations  in the  SCS  were generally higher than  those in the  BS and YS.  This was probably  due to the  higher solar  radiation   and  air   temperature   in  the   SCS.  The   RGM  concentrations   at Changdao exhibited significant seasonal variation with the order  of summer > spring or fall  > winter,  while the  HgP2.5 concentrations  also exhibited significant  seasonal variation with the order of winter > spring or fall >  summer. The correlation analysis revealed  that  RGM positively  correlates  with  solar  radiation  and air  temperature while   negatively   correlates    with   relative   humidity.    Additionally,   the   RGM concentrations in  the daytime  were significantly higher  than those  in the  nighttime during the  whole study period.  The above results  indicated that  solar radiation was conductive  to the  production  of RGM.  The  HgP2.5 concentrations  in  the  BS were higher than those in  the YS and SCS, and the  spatial distribution of HgP2.5 generally reflected a  gradient with  high levels  near the  coast of  China and  low levels  in the open  sea, suggesting  the  significant  atmospheric mercury  outflow  from  China.  A cascade impactor was used  to collect HgP in  nine size fractions ranging from  10 µm to <  0.4 µm (nine stages).  The concentrations of  HgP in PM10  (hereafter referred to as  HgP10)   also  tended  to   decrease  from   the  land  to   the  open  sea   except  the measurements in the  BS. Additionally, the ratios  of HgP2.1 to  HgP10 in the nearshore area were higher than  those in the open sea.  Moreover, there was a distinct  seasonal variation of HgP10 concentrations and the ratios  of HgP2.1/HgP10 at Changdao, and the HgP10 concentrations at Changdao were higher than those in Chinese marginal seas.
    The  dry deposition  flux of  RGM  was significantly  higher  than that  of  HgP10 both in Chinese marginal  seas and at Changdao  Observatory. The RGM contributed more than 85% of  the total dry deposition of  RGM and HgP10. Moreover, the  coarse HgP  (HgP2.110) plays  an  important role  in  the dry  deposition  of  HgP10 due  to  the higher  dry deposition  velocities  of  coarse particulate  matters.  The  dry deposition fluxes of RGM and HgP10 at Changdao Observatory  were all higher than those in the Chinese marginal  seas. The dry  deposition flux  of HgP10 exhibited distinct seasonal variation with the order of winter  > spring > summer > fall, while the dry  deposition flux of RGM exhibited seasonal variation with the  order of summer > fall > spring > winter. The annual  dry deposition flux of  RGM and HgP10 in Chinese  marginal seas were 5.68 and 0.69 g m2 yr1,  which were lower than those estimated at Changdao Observatory  (RGM: 11.0  g m2  yr1,  HgP10:  1.74 g  m2  yr1).  The annual  wet deposition flux at Changdao Observatory was 1.80 g m2 yr1.
      The air-sea fluxes  of Hg0 in Chinese marginal  seas were estimated using  a thin film gas  exchange model.  The results  show that  the dissolved  gaseous Hg  (DGM)concentrations in  surface seawater  of the  nearshore area  were higher  than those  in the  open sea  except  the  measurements in  the  BS,  while there  was  no  significant
difference  in  Hg0  fluxes   between  the  nearshore  area  and  open  sea.  The   DGM concentrations  and  Hg0 flux  at Changdao  Observatory  exhibited  distinct  seasonal variation with the order of summer > fall > spring > winter. The emission flux of Hg0 from  the ECS  was estimated  to  be 27.6  tons  yr−1, accounting  for  ~ 0.98%  of  the global  Hg oceanic  evasion  though  the ECS  only  accounts for  ~  0.21%  of global ocean area, indicating  that the ECS plays an  important role in the oceanic  Hg cycle,moreover,  we can  get  similar  results in  the  BS,  YS and  SCS.  The  above  results indicated  that  the  Chinese  marginal  seas  were  the   main  sources  for  the  global aomospheric Hg.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36969
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
王纯杰--我国近海大气汞的时空分布及海-气交换研究.pdf(8344KB)学位论文--限制开放 联系获取全文

Recommended Citation:
王纯杰. 我国近海大气汞的时空分布及海-气交换研究[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
[王纯杰]'s Articles
CSDL cross search
Similar articles in CSDL Cross Search
[王纯杰]‘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