【作者】 贾铁飞；

【导师】 俞立中；

【作者基本信息】 华东师范大学 ， 自然地理学， 2008， 博士

【摘要】 本学位论文以地处长江中下游沿江地区的巢湖作为研究对象,通过野外考察、沉积剖面分析、湖心沉积柱样钻取、沉积物实验室分析、历史文献考证资料整理、历史时期自然灾害分析等,在全新世全球环境、气候演变的背景下,着重对巢湖地区湖泊沉积记录的环境变化事件与环境演变过程、史志资料记录的自然灾害及其序列、历史时期人类活动与流域环境变化的相互影响过程等问题,进行了系统研究,得出以下主要结论:1.中全新世以来巢湖变化体现了四个显著的特点:河湖相沉积在时间上和空间上均存在频繁的相变过程;伴随着频繁的湖面水位升降存在着频繁的湖面涨缩过程;由湖泊沉积指示的气候干湿变化频繁;人类活动影响逐渐增强。中全新世以来巢湖流域气候的反复性、逆转性变化,具有较强烈的气候突变色彩,被认为是导致区域文明中断的主要因素,也给人类社会带来灾难。2.巢湖CH-1孔沉积物粒度分析、磁学分析、年代学分析,可将该钻孔沉积指示的巢湖环境、气候变化划分为4段:①沉积物年代1 177 aA.D.～1 271aA.D.为湿润时期,并与中世纪暖期的时间相吻合;②1 271 aA.D.～1 747 aA.D.,湿润与干旱交替作用的时期,共有5次极端干旱事件,其中最盛干旱事件在1 747 aA.D.,代表中国东部“小冰期”盛期;③1 747 aA.D.～1 865 aA.D.,是小冰期盛期后持续回暖的阶段;④1 865 aA.D.～今,是一个冷干化的过程,盛期在1930’s A.D.。3.CH-1孔沉积物15项化学元素和营养元素分析表明,巢湖沉积物总体上对中世纪暖期、“小冰期”、20世纪初冷期均有较好的记录。化学元素和营养元素经过粒度校正后显示,自1 860’s开始Cu、Zn元素具有非自然水平的异常增长,1 660’s开始营养元素开始出现非自然水平的富集。4.CH-1孔沉积物粘土矿物分析显示,沉积年代1 912 aA.D.存在一个极端干冷过程事件,其他干冷年代为1 865 aA.D.、1 536 aA.D.～1 583 aA.D.、1 442aA.D.。伊利石Hw值、IJ值、开行指数均表明巢湖地区近千年来总体气候环境的暖湿趋向。5.CH-1孔沉积物的孢粉谱可划分为3个带:沉积物年代1 177 aA.D.～1 477 aA.D.,孢粉指示为温和、较湿的气候环境;1 477 aA.D.～1 771 aA.D.,是暖热潮湿的气候环境:1 771 aA.D.～1 977 aA.D.,为温湿气候环境,温度和湿度均比前期低。利用森林指数(W)可定量地划分出干湿变化:1 177 aA.D.～1 477aA.D.,是一个森林占绝对优势的湿润温暖时期,恰好跨越中世纪暖期。1 477aA.D.～1 853 aA.D.,巢湖地区森林衰退非常严重的时期,正好穿越了整个“小冰期”。森林指数可为利用孢粉分析资料定量刻画植被环境提供新的途径。6.根据对CH-1孔沉积物所指示的环境变化事件的捕捉,可以将环境变化事件分为3种类型:环境变化突发事件、极端事件、转折事件;据此可将巢湖地区近千年来环境变化划分为6个时期:①沉积物年代1 177 aA.D.～1 300aA.D.,总体气候温暖湿润,但存在短期干旱极端事件;②1 300 aA.D.～1 480aA.D.,总体气候温和湿润,森林发育极其繁盛;③1 480 aA.D.～1 600 aA.D.,气候总体温和干旱,森林开始退化;④1 600 aA.D.～1 750 aA.D.,气候总体寒冷干早,森林退化;⑤1 750 aA.D.～1 880 aA.D.,气候总体温和湿润;⑥1 880aA.D.～今,气候总体温暖湿润,森林繁盛。7.通过主成分筛选,确定8个密切反映环境变化信息的指标变量,以此对巢湖CH-1孔沉积物进行聚类分析,可将沉积物划分为3类、4亚类。据此建立了近千年来巢湖地区环境演变综合序列:1 177～1 241 aA.D.,干旱、温和时期;1 241～1 488 aA.D.,湿润、温和时期;1 488～1 635 aA.D.,干旱、温和时期;1 635～1 753 aA.D.,干旱、寒冷时期;1 753～1 818 aA.D.,干旱、温暖时期;1 818 aA.D.～今,湿润、温暖时期。8.1 750 aA.D.左右是巢湖环境变化的一条重要分野线,沉积物磁学参数和粒度参数显示其前后存在差异显著的沉积特点,可能指示该时间前后存在着流域范围的调整;而在环境变化特点上,1 750 aA.D.前后也呈现显著不同,总体上之前气候较冷、之后气候较暖。9.总体上看,近千年来巢湖沉积记录具有良好的对全球变化的响应,对全球性中世纪暖期、“小冰期”气候变化响应的沉积记录清晰、明确,并与其他研究结论基本一致。巢湖地区“小冰期”气候特点表现为,在总体温和、湿润的气候背景上插入若干次强劲的冷干波动,造成气候环境的较强不稳定性。气候环境系统稳定性衰减是造成巢湖地区自然灾害频发、重灾的主要原因之一。10.经过粒度校正后,CH-1孔沉积物Cu、Zn元素的富集系数最大,且与沉积物粘土组分、磁学参数具有良好的相关关系,判断在沉积物年代1 860’s开始的Cu、Zn元素非自然水平异常增长,可以视为人为影响下的金属元素污染,是对安徽近代工业起始(安庆内军械所,建于1861年)的沉积响应;沉积物的营养元素分析则指示了以P元素非自然水平富集标志的1 660’s人口、耕地数量大幅增加,以TOC、TN、TP元素非自然水平富集标志的1 880’s的又一次人口、耕地数量的大幅增加,沉积记录显示此时起巢湖已经开始逐步富营养化。化学元素和营养元素的粒度校正,可为甄别化学元素的非自然原因富集提供新的途径。11.巢湖流域地区近500 a来自然灾害较为频繁,清代自然灾害明显比明朝频繁;水灾均较旱灾更为严重:水旱灾害的形成与气候环境干湿变化的“节奏”基本一致,近500a来巢湖地区水旱灾害的形成,主要源于气候环境变化的驱动,自然因素为灾害发生的主因。同时,气候环境稳定性衰减也是形成水旱灾害频发、重灾频现的原因之一。12.近500 a来巢湖地区水旱灾害状况说明,明清时期巢湖地区人类对自然灾害的适应尚处于被动状态。主动适应环境变化,需要人类对环境变化规律有正确的认识和掌握,这还有赖全球变化研究的进一步深入。本学位论文在沉积物年代学分析、高分辨率沉积物样品获取、对环境演变代用指标差异的解释、人类活动的湖泊沉积响应等方面,尚存在一些问题有待今后研究继续深入。本文研究表明,沿江湖泊全新世(尤其是晚全新世以来)河流与湖泊交互作用的沉积记录分析、沿江湖泊地区历史时期人类活动的沉积记录与沉积响应、人类对环境演变的适应等方面,应是今后工作中需要重点研究的课题。更多还原

【Abstract】 With Chaohu Lake as its study object,which is located in the areas along the middle and lower reaches of the Yangtze River,and taking the methods of field investigation, comparison among the sedimentary piles,drilling lacustrine deposits core in the centre of lake,laboratory analysis of sediments,textual research of documents as well as an analysis of natural disasters in the historical periods et al,this doctoral dissertation focuses on exploring such issues as the environmental events and the environmental evolution process whose records were kept in the deposits,natural disasters and their sequences reflected in historical documents,interaction process between human activity and drainage area environmental change against the background of global environment and climate evolution in Holocene.It is concluded that:1.Four remarkable characteristics have been shown in the environmental evolution of Chaohu Lake since the Holocene metaphase:There has been a frequent phase transition process both temporally and spatially in the fluvial-lacustrine deposits.The area of Chaohu Lake has frequently expanded and contracted in accordance with the ascent and decent of lake level.Dry and wet climate indicated in the lake sediments have changed frequently.The influence of human activity has gradually increased.2.According to an analysis of the age data,granularity and magnetics of deposits in Chaohu lake,sample core CH-1 could be divided into 4 sedimentary chronological sections,to wit:①1 177 aA.D.to 1 271 aA.D.is proven to be a wet period,matched along with the Medieval Warm Period（MWP ）.②1 271 aA.D.to 1 747 aA.D.is proven to be a wet / dry alternative action period, with a total of 5 extreme drought events,including the drought maximum in 1 750 aA.D.or so,which indicates the climatic characteristics of The Little Ice Age（LIA ） in East China.③1 747 aA.D.to 1 865 aA.D.is proven to be a continuous milder stage after The Little Ice Age Maximum.④1 865 aA.D.to Present is proven to be a colding and drying climatic process,whose maximum happened in the 1930’s A.D.3.According to a 15-indicator analysis of the chemical elements and mineral nutrient of deposits in core CH-1,it is shown that lacustrine deposits in Chaohu Lake basically indicate the MWP,LIA and the cold period in the early 20^th century.After taking normalization of the chemical elements and mineral nutrients content,it is seen that the contents of Cu and Zn have increased with unnatural levels since 1860s,while the content of mineral nutrients has enriched with unnatural levels since 1660s.4.According to an analysis of the clay mineral of deposits in core CH-1,it is shown that there was an extreme cold and dry event in 1 912 aA.D,with other cold and dry events separately in 1 865 aA.D.,1 536 aA.D.to 1 583 aA.D.and 1 442 aA.D..It is also proven by the Hw,IJ and Ns values of Illite that the general trend of climatic environment is to be much warmer and wetter for the past approximate millennium.5.The sporopollen spectrum of deposits in core CH-1 could be divided to 3 pollen zones according to the sedimentary chronology,to wit:①a wetter climatical environment from 1 177 aA.D.to 1 477 aA.D..②a moist climatical environment from 1 477 aA.D.to 1 771 aA.D..③a moist climatical environment from 1 477 aA.D.to 1 771 aA.D.,but the humidity level was a little lower than before.The wet-dry weather change circle can be quantificationally divided by the Wood Index,to wit:①1 177 aA.D.to 1 477 aA.D.was a moist and warm period in which the forest area was absolutely dominant on the earth,and also just stepped over the Medieval Warm Period.②1 477 aA.D.to 1 853 aA.D.was a period in which the forest in surrounding areas of Chaohu Lake degraded seriously,just matching with the whole The Little Ice Age.The Wood Index offers a new approach to quantitative description of vegetation environment with spore and pollen analysis materials.6.According to the exploratory research of Environmental Change Events indicated by the deposits in core CH-1,the history of the environmental change in surrounding areas of Chaohu Lake for the past approximate millennium could be divided into 6 periods according to the sedimentary chronology.①1 177 aA.D.to 1 300 aA.D.was a moist and warm period in the mass,but short-term extreme drought events also happened at that time.②1 300 aA.D.to 1 480 aA.D.was mainly a moist and moderate period so that the forest flourished very much.③1 480 aA.D.to 1 600 aA.D.was a dry and moderate period in the mass so that the forest started to degrade.④1 600 aA.D.to 1 760 aA.D.was a dry and cold period in the mass so that the forest degraded seriously.⑤1 760 aA.D.to 1 880 aA.D.was a wet and moderate period in the mass.⑥1 880 aA.D.to present has been a wet and warm period in the mass so that the forest has flourished again.7.Through selection of the principal component analysis,8 target variables that closely reflect the information of environmental change are confirmed.Thereby,the cluster analysis of deposits is conducted,and the deposits are further classified into 3 types and 4 subtypes.Based on the classification,integrative sequence of Chaohu Lake Area for the past approximate millennium can be rebuilt:1 177 aA.D.to 1 241 aA.D.was a dry and moderate period;1 241 aA.D.to 1 488 aA.D.was a wet and moderate period;1 488 aA.D.to 1 635 aA.D.was a dry and moderate period;1 635 aA.D.to 1 753 aA.D.was a dry and cold period;1 753 aA.D.to 1 818 aA.D.was a dry and warm period;1 818 aA.D.to present has been a wet and warm period; 8.1 750 aA.D.or so is an important boundary of Chaohu Lake environmental change history.On the one hand,there are remarkably different sedimentary characteristics between its before and after reflected by parameters of magnetics and granularity in deposits,which may indicate an adjustment that occurred during this period;on the other hand,there are notable different characteristics of the environmental change between its before and after,demonstrating a cold climate beforel 750 aA.D.and a warm climate afterl 750 aA.D.in the mass.9.Generally speaking,the Chaohu lake sedimentary records for the past approximate millennium respond to the global environment change well:on the one hand,they indicate the global MWP / LIA clearly and definitely;on the other hand,they are almost as same as the result of other work.10.After taking normalization of the chemical elements and mineral nutrients content, the Enrichment indices for Cu,Zn are the highest,correlating well with the clay constituents and magnetic parameters,so it is thought that the contents of Cu and Zn have increased with unnatural levels since 1860s,which could be considered as metal pollution impacted by human activity and is the sedimentary response to the origin of industry in Anhui province（Anqing Inner Armory,founded in 1861）.An analysis of the contents of mineral nutrients indicates one mark of the element P’s enrichment with unnatural levels during the 1660s which explains why the amount of population and arable land had greatly increased during that time.Another mark of the enrichment of TOC,TN,TP with unnatural levels during the 1880s explains why the amount of population and arable land greatly increased again.Sediment records prove that Lake eutrophication had started in Chaohu area since that time.Normalization of the chemical elements and mineral nutrients content could be a new method to discriminate the enrichment as the unusually natural reason. 11.Natural disasters have been frequent for the past approximate 500a in Chaohu drainage area,and occurred in Qing Dynasty more frequently than in Ming Dynasty. Floods are more serious than droughts.The formation discipline of these floods and droughts is in close agreement with the variation of wet/dry climate.It is thought that floods and droughts for the past approximate 500a in Chaohu area result from the drive of climatic environment change,whose mainly formative reason amounts to the natural factor.At the same time,the attenuation of climatic stability is also a formative reason of the frequent and serious disasters.12.The conditions of floods and droughts for the past approximate 500a in Chaohu area illustrate that human adaptation to disasters still stayed in the passive mode in Ming and Qing Dynasty.Positive adaptation to environmental change needs that human beings accurately master the law of Environmental Change,which depends on the further research of Global Change.In this thesis there is still room for improvement in areas such as analysis of the sedimentary chronology,acquisition of High Resolution Deposit Sample,explanation to the difference among the proxy indicators of environmental evolution,lacustrine deposits response to human activity et al.,which is expected to be explored with the further study in future.As is shown in the thesis,three aspects,namely the sediment records analysis of the fluvial-lacustrine-interacted lake in the areas along the Yangtze River in Holocene（especially since Late Holocene）,the sediment records responses to the human activity of the lake in the areas along the Yangtze River in historical periods,and the human adaptation to environmental evolution,should be the primary issues in future research.更多还原