【作者】 张明；

【导师】 鲍征宇； 陈国光；

【作者基本信息】 中国地质大学 ， 地球化学， 2017， 博士

【摘要】 华东沿海滩涂总面积11056.48 km2,占我国滩涂面积一半左右,是我国重要后备土地资源。前人的研究只局限于小区域、少量元素的研究,缺少针对华东沿海滩涂整体区域地球化学特征及不同类型滩涂围垦后地球化学变化规律的系统研究。本文以华东沿海滩涂区作为研究对象,以1:25万多目标区域地球化学调查所获得的1906个表层样品测试分析数据为基础,应用多种统计分析方法,重点研究了华东地区沿海滩涂沉积物中重金属元素和富营养元素含量特征,讨论了华东地区沿海滩涂中重金属污染和富营养化的程度和影响因素。随后,作者选择了大丰(淤泥质滩涂)、如东(粉砂质滩涂)两个不同物质组成典型滩涂区,分析其在百年尺度下不同围垦年限、不同利用方式滩涂的成土过程、常量元素、重金属元素、营养元素、含盐量、盐基离子和pH的变化规律,并采用相关分析、因子分析等统计方法揭示地球化学指标内在关系。主要的研究结论如下:1、通过对中国东部沿海滩涂中重金属元素含量特征、富集因子和元素共生组合特征分析,中国东部沿海滩涂沉积物中各重金属元素含量总体不高,大多低于世界主要河口三角洲的重金属元素含量水平,污染程度总体不高。2、中国东部(由北向南)的江苏省、上海市、浙江省、福建省的沿海滩涂中重金属的分布特征有较大差别,表现为江苏省沿海滩涂的重金属含量总体偏低,污染叠加弱;浙江省和上海市沿海滩涂中重金属含量一般最高,含量直方图多呈双峰分布,显示强烈的污染叠加,尽管平均值大多未超标,但存在一定量的高值点,其含量已超过国家土壤环境质量II级乃至III级标准,其污染程度值得关注;福建省沿海滩涂中重金属含量则多显示高背景下的部分污染叠加;富集分析显示各种重金属元素均有一定程度的富集,其中尤以As和Hg最为明显,50%以上采样点达到中等富集(EF>2.0)以上;Cr次之;其它重金属元素多为弱富集,中等富集和强富集的比例小。3、Pb、Zn、Hg、Cu、Ni、As是华东地区沿海滩涂中重金属元素的主要组合,代表了沿海滩涂受区域岩石风化背景制约下受人类活动影响的一组元素组合特征。滩涂中重金属元素明显以Fe-Mn氧化物和粘土矿物(以高Al为特征)吸附、有机质(以高OrgC含量为特征)吸附为主要富集机理,并受环境酸碱性的影响,酸性条件(CaO、pH、Na2O低)有利于重金属元素Pb、Zn、Hg、Cu、Ni、As在滩涂沉积物中富集。4、中国东部沿海滩涂沉积物中N、OrgC的含量总体不高;P含量相对较高,局部富营养化较严重;各省市沿海滩涂沉积物中N、P、OrgC含量的分布特征差异明显。5、通过对大丰、如东2个典型区不同围垦年限土壤理化性质分析显示:土壤粒度变化规律是一致的,随着围垦年限增加平均粒径变小,细粒径含量增加,粗粒径含量减少;pH和无机盐总量同时呈现随着围垦年限增加pH和无机盐总量逐渐减小,盐基离子组合和含量也发生变化,Na+、Cl-所占比例减少,Ca2+、Mg2+、SO42-及HCO3-所占比例逐渐增加;Cd、Hg、N、P、F、I等含量都随着围垦年限的增加而增加;As、Cl、Br等含量随着围垦年限的增加而减少。6、土壤风化指数显示两个地区在围垦后呈现成土过程有所差别,在大丰围垦区呈现出富硅贫铝、铁成土过程,而如东则呈现相反成土过程。但同时又都在进行脱盐、脱钙成土过程。7、围垦后土壤理化性质变化对土壤元素含量有着不同程度影响,其中土壤风化指数Na/K、硅铝率和硅铝铁率变化规律能很好解释两个围垦区重金属、卤族元素和营养元素不同变化特征。8、通过对大丰、如东两个典型区不同利用方式滩涂土壤理化性质分析显示:人为影响较大利用方式(如农田)土壤粒径越均匀,细粒径含量越多;无机盐总量呈现出农田、鱼塘、林地含量明显低于潮滩和荒地,盐基离子也从潮滩和荒地中以Cl-、Na+为主向农田和林地中Ca2+、Mg2+、HCO3、SO42-等为主转变;Cd、Hg、Cu、N、P、有机质、I、F等在农田、林地、鱼塘中显示含量特征,As、Cl、Br呈现相反特征;土地利用方式不同对成土过程有所影响,农田、林地和鱼塘中壤风化指数Na/K、硅铝率和硅铝铁率变化明显高于潮滩和荒地。更多还原

【Abstract】 The area of intertidal zone in Eastern China is about 11056.48 km2,which accounts for half of the total intertidal area in China and constitutes a critical backup of land resource.However,current researches are mainly limited to investigations done in a small region and based on a small number of measurements,and there is a lack of a systematic investigation focusing on geochemical characteristics in the whole zone and changes caused by reclamation time in Eastern China intertidal zone.Based on a multi-purposed 1/250,000 geochemical survey in East China intertidal zone organized by China Geological Survey,1906 samples of surface sediments(soils)were taken and 54 geochemical indexes measured for each sample.In this dissertation,multivariate statistics were applied to analyze the data obtained by the project,focused on studying concentration and distribution of heavy metals and nutrition elements in the whole zone and their correlation to other geochemical indexes,and on evaluating the pollution statue of heavy metals and eutrophication in the East China intertidal zone.Two typical areas,Dafeng and Rudong in Jiangsu province,were then chosen to study the changes of physical properties,contents of major elments,heavy metals,nutrient elements,salt etc.,in intertidal soils of after different length of reclamation time.The main conclusions reached in this dissertation are as the followings:1.Through a study on the content distribution and enrichment factors of heavy metals and their correlation with other geochemical indexes,the concentration in the East China intertidal zone as a whole is believed to be relatively low,lower than those of most estuaries in the world.And the pollution of heavy metals is not very serious as believed before.2.In the East China intertidal zone,content distribution of heavy metals shows different styles for different region,i.e.,from north to south,Jiangsu province,Shanghai Municipal,Zhejiang prvince and Fujiang province.It is revealed in this dissertation that contents of heavy metals in Jiangsu is usually lower than in other regions,with a relatively low pollution level of heavy metals,while the concentration distribution of Zhejiang and Shanghai is quite diffent,with higher average concentrations and double peaked distribution showed in histigram,demonstrate a reasonably strong pollution of heavy metals in the intertidal zone of these two regions.Fujiang show a different senario,showing a high background concentration of heavy metals and a less degree of superimposition.Compared to their contents on regional rocks,heavy metals show some degree of enrichment in the East China intertidal zone,especially As and Hg which have reached moderate enrichemnt with enrichment factor EF>2.0.Cr is the next enriched element,while the enrichment of other heavy metals is neglecable,with only a small propotion of moderate enrichment.3.Pb,Zn,Hg,Cu,Ni and As are proved to be a closely correlated group of heavy metals,indicating a similar resource from the weathering of regional rock and affected by authropogenic activities.Factor analysis also demonstrates that this association of heavy metals is believed to be mainly capture by the sediments by adsorption by Fe-Mn oxides,clay minerals(characterized by high aluminum contents),and organic,and be affected by the physicochemical properties of the sediments,benefiting from an acid condition.4.Contents of total nitrogen(N)and total organic carbon(OrgC)is not high as believed previously,Phosphorous content in the East China intertidal zone is generally of modeate level,with large values in some isolated sampling sites,indicating some localized eutrophication.,but N,P and OrgC show a different pattern of concentration distribution for different regions(provinces and municipal).5.Soil physicochemical property of lands with different reclamation durations at two typical reclamation areas(named Dafeng and Rudong)were analyzed and the result indicated a similar variation trend of soil particle sizes in both areas.Soil particle size decreased along with the increase of reclamation time.Soil clay contents presented increase trend with increased reclamation time.By contrast,soil sand contents had opposite change trends.Both soil pH and inorganic salt presented decreased trends with increased reclamation duration,along with the change of composition of base cations.The ratio of Na+ and Cl-decreased while the ratio of Ca2+,Mg2+,SO42-,and HCO3-increased as the reclamation durations went by.For other elements,the total contents of Cd,Hg,N,P,F,and I presented increasing trends as reclamation durations increase,whereas the contents of As,Cl,and Br decreased.6.Soil weathering index indicated that the soil development was different in the two areas.Dafeng reclamation area showed the process of Si enrichment and poor Al Fe,while Rudong showed inverse process.At the same time,desalinate and decalcification were noted both in the two areas.7.The changes of soil grain size,OM,macroelements,pH have important and different impacts on heavy metals,halogen elements,and N,P,which indicated that the physicochemical property changes along reclamation was crucial for the changes of elements.The changes of Na/K,silica-alumina ratio,silica-sesquioxide ratio in soil development can reveal the essential reason for the difference of heavy metals,halogen elements,N and P changes in the two reclaimed areas.8.The analysis on soil physicochemical properties with different land uses in Dafeng and Rudong indicated that soil particle sizesdistributed evenly in human-dominated land uses such as cropland.Moreover,the human-dominated land uses were characterized by high clay and silt contents.The contents of inorganic salt of cropland,fishpond,and forestland were significant lower than those in tidal flats and barren land.In tidal flats and barren land,the major base cations were Cl and Na,while they were Ca2+,Mg2+,HCO3,and SO42-in cropland and forest land.Cd,Hg,Cu,N,P,organic carbon,I,and F accumulated in cropland,forest land,and fishpond,whereas As,Cl,and Br accumulated in tidal flats and barren lands.Land uses exert significant impacts on soil-forming process.The soil weathering indexes such as Na/K,silica-alumina ratio,silica-sesquioxide ratio of cropland,forest land and fishpond were remarkably higher than those in tidal flats and barren land.更多还原