IMHE OpenIR  > 山地表生过程与生态调控重点实验室
长寿湖水库沉积泥沙来源的多种示踪研究
Alternative TitleSourcing sediment deposited by tracers in the Changshou reservoir
Language中文
高进长
Thesis Advisor贺秀斌
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline土壤学
Keyword137cs 210pbex 颗粒组成 养分 重金属 泥沙来源 长寿湖水库
Other Abstract

长寿湖水库位于长江流域三峡库区,其所在流域为龙溪河流域是三峡库区的一个重要组成部分,龙溪河流域对长寿湖水库库区的生态环境健康和水库水质安全起着重要作用。应用泥沙来源的多种示踪技术,判定长寿湖水库沉积泥沙来源,对科学合理地制定水库泥沙调控策略和龙溪河流域水土保持措施具有重要的现实意义和科学价值,并且对三峡水库的泥沙来源研究具有重要的借鉴意义。因此,本论文通过野外调查采样和室内试验分析,阐述沉积泥沙及泥沙养分和重金属垂直变化特征及成因解析,对长寿湖水库沉积泥沙剖面进行断代定年和泥沙沉积动态过程解析,应用多种示踪技术探讨长寿湖水库沉积泥沙来源。论文主要研究结果和结论如下:(1)沉积泥沙剖面定年及泥沙沉积动态分析在2014年5月于龙溪河流域的长寿湖水库,应用重力采样器采集三个代表性样点的沉积泥沙样芯,每一个样芯从上而下平均2 cm均匀分层取样。分别利用容重和颗粒组成、人类活动特殊事件对TOC和TN的影响、137Cs和210Pbex放射性核素、降雨侵蚀力与颗粒粒径的密切关系,对水库沉积泥沙剖面进行断代定年,判定沉积泥沙剖面的年代分别是1956、1963、1982、1989、1998和2005。具体是根据沉积泥沙容重和颗粒组成在1956年建水库建设前后沉积泥沙与原有的河滩、土壤之间的显著差异,判定沉积泥沙的起始时间;137Cs比活度的1963年峰值,是可靠的断代标志,利用137Cs比活度在沉积泥沙剖面的峰值标志1963;根据流域降雨侵蚀力极大峰值与沉积泥沙颗粒变粗呈现粘粒的极低谷值之间相对应的关系,龙溪河流域在1982、1989和1998年,降雨量出现峰值对应着降雨侵蚀力出现极大峰值,与沉积泥沙细颗粒的极低谷值之间相对应;由人类对长寿湖水库养鱼政策的影响,即肥水网箱养鱼后泥沙TOC和TN增加,2005年全面禁止肥水网箱养鱼使泥沙TOC和TN含量出现峰值,可判定沉积泥沙剖面年代。从水库建成的1956年到2013年,样点A、B和C的沉积泥沙,年均沉积速率分别为1.586 cm/a、1.138 cm/a和0.655 cm/a。1982-1988年期间,样点A和B沉积泥沙的沉积速率达到最大值,分别是2.286 cm/a和2.000 cm/a,样点C的年平均速率也较大,为 0.857 cm/a,这段时间是我国开始实施家庭联产承包责任制,农民耕种对耕地扰动强烈,同时,这期间龙溪河流域降雨总量偏多,两者的共同作用使土壤侵蚀强烈和水库泥沙沉积速率显著增加;1989-1997年,样点A、B和C泥沙的年沉积速率较大,为1.778 cm/a,1.778 cm/a和1.111 cm/a,原因是实施退耕还林还草、建造梯田等措施的初期,人为扰动土壤表层,增加土壤表层的不稳定性,易造成土壤侵蚀产沙。2005-2013期间,样点A、B和C泥沙的年沉积速率分别为1.556 cm/a、0.444 cm/a和0.667 cm/a,即当植被覆盖度的增加到一定程度,起到改善环境与减蚀作用,土壤侵蚀逐渐得以控制。1956年,长寿湖水库的建库初期,砂粒逐渐增加,细颗粒逐渐增加,样芯A、B和C的92 cm、66 cm和38 cm以上的部分是水库建成之后淤积的泥沙,很可能受到河岸或河床物质的影响,粗颗粒泥沙占主要部分,反映水库建设之初河岸物质被浸泡而不稳定,或者库岸侵蚀及土体崩塌,最后泥沙沉积到水库底部。样点A的40 cm、B的24 cm和C的14 cm,沉积时间大约是1980年代中后期,这时正是我国进行农村家庭联产承包责任制的时期,农民大量开荒种田,农田耕作方式粗放,结合1982和1989年降雨量大,降雨侵蚀力较大,共同作用致使土壤侵蚀强烈,泥沙颗粒变粗。1998年后,国家实施全面禁伐的政策,加上配套实施的退耕还林还草措施、天然林资源保护工程等,均减少了流域内陡坡地段的水土流失,但是,植树造林之初,土壤表层被破坏,疏松的表层土壤,更容易受到降雨的侵蚀,并随雨水、径流输移到水库中淤积沉淀,泥沙粗颗粒逐渐增加。自2005年,泥沙粒径垂直变化呈现出泥沙颗粒变细的现象,可能是由于近十几年耕地保护性耕作和在植树造林政策下植被覆盖度增加,土壤侵蚀减小。(2)水库沉积泥沙养分和重金属垂直变化及成因分析在水库建成之初,TOC、TN和TP由大变小,富含NCP的库岸表层泥沙和低水位表层土壤,在长期水的浸泡冲刷下,CNP随着表层泥沙和表层土壤,进入水库,沉淀淤积,随着库岸中富含CNP的土层被侵蚀和淤积于水库中,含量逐渐减小,沉积泥沙中的TOC、TN和TP逐渐减少。在1980年代中后期,TOC、TN和TP均呈现逐渐增加的趋势,且分别在样芯A、B和C的12-14 cm、4-6 cm和6-8 cm深度处达到峰值,可能是开始肥水网箱养殖,残饵、粪便等养殖废物在养殖区逐渐积累,导致水体和沉积泥沙中CNP含量增加,在2005年,长寿湖水库全面禁止肥水养鱼,禁止投放动物粪便和化肥到水库中,TOC、TN和TP在2005年出现峰值;在2005-2013年,沉积泥沙中TOC、TN和TP逐渐减少,由于沉积于底泥的氮、磷等各种营养物质作为内源物质,逐渐释放到水体中,使泥沙中CNP含量逐渐减少。沉积泥沙中重金属含量由大到小为Zn>Cr>Ni>Pb>Cu>Co>Cd。在1956年长寿湖建设之初,受到水库泥沙淤积的影响,泥沙重金属含量具有由高逐渐减小趋势;在1989-1998年期间,随着我国经济的发展使城镇、工厂废水的排放量逐渐增加,沉积泥沙中重金属元素有逐渐增加的趋势;从2005-2013年期间,除Cd含量逐渐减小外,其余重金属含量增加显著。Pearson相关性分析显示Cd、Co、Cr、Cu和Ni,具有显著或极显著相关性,主成分分析发现Cd、Co、Cr、Cu和Ni可解释变量的55%以上,说明自然来源是影响泥沙重金属含量的主要因素;Zn和Pb相关性较弱且二者之间的相关性较差,且二者之间受不同来源或受控因素有差异,主成分分析表明Zn和Pb主要受到龙溪河流域人类的生活污水和工业排放的影响;而泥沙Cd受到自然和人类活动的综合影响。(3)沉积泥沙来源分析将泥沙来源示踪因子技术的方法运用到长寿湖水库沉积泥沙物源示踪研究中,采样方法为典型的森林小流域和农田小流域代替传统样点采样方法,增加了泥沙来源样本的代表性,从流域空间位置上将沉积泥沙来源划分为龙溪河上游、中游、下游,从土地利用类型上把流域泥沙来源分为林地(森林小流域)和耕地(农田小流域)。长寿湖水库泥沙来源,森林小流域和农田小流域泥沙来源分别为31%和69%,单位面积的耕地产沙量时单位面积的林地产沙量的1.43倍,说明龙溪河流域农田小流域(耕地)仍然是本区域土壤侵蚀产沙的主要区域,耕地特别是坡耕地频繁翻松、耕作,加之较多的山地丘陵区较陡的坡度,地块完整性较差,因此,仍需要进一步加强对耕地水土流失的预防和治理。按照泥沙流域空间来源,龙溪河流域上游、中游和下游的泥沙来源所占比例分别为13%、71%和16%,中游(垫江)的主要土壤类型是耕地,因此,垫江县耕地是土壤侵蚀和水土流失的严重区域,也是治理和预防土壤侵蚀和水土流失的关键区域;下游的区域距离长寿湖水库最近,特别是湖区周边,轻微的土壤侵蚀亦能使泥沙进入水库,需要加强水库周围区域的水土保持措施。

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The study area of Changshou reservoir in the Longxi catchment is located in the Three Gorges Area of the Upper Yangzte River. The study area is an important component of the Three Gorges Area to protect the health of the ecological environment and the water quality. Using multiple tracer technologies to predicate the sediment source of the Changshou reservoir, it is helpful to set up scientific and reasonable control strategies of the Changshou reservoir and soil and water conservation measures in the Longxi catchment. Therefore, the present study has field investigation and experimental analysis, to reveal the characteristic of the sediment including nutrients and heavy metals, to determine the date of the sediment profiles and analysis the sediment deposited dynamic process, and to research the sediment source by using tracer technologies. The main results and conclusions in this dissertation are as follows: (1) Dating the sediment profiles and analysising sediment deposited dynamicSome sediment cores were retrieved from the Changshou reservoir in 2014, using a gravity corer equipped with an acrylic tube with an inner diameter of 6 cm. The extracted cores were sectioned at 2 cm intervals. All sediment core samples were dried, sieved (<2 mm) and weighed. Based on bulk density and particle size, human activites and nutrients, 137Cs and 210Pbex technologies, and particle size and rainfall erosivity, the present paper dated sediment profiles chronosequence, that were 1956, 1963, 1982, 1989, 1998 and 2005. Based on the significant difference between bulk density and particle size in the sediment before and after the construction of the Changshou reservoir which was constructed in 1956 with significant difference between the original river bed or soil and sediment, it determined the starting time of sediment deposited in 1956. Using the 1963 peak of 137Cs in a sediment profile, it was a reliable date marks in 1963. According to the relationship of the peak rainfall and rainfall erosivity corresponding to coarse particle size, it could find the time of 1982, 1989 and 1982 in sediment profiles. By human activities of fish farming policy, the peaks of TOC and TN content in sediment profiles was the time in 2005 due to the ban of fish culture in cage with fowl manure and chemical fertilizer. From Changhou reservoir built in 1956, the annual average sedimentation rates were 1.586 cm/a, 1.138 cm/a and 0.655 cm/a in cores A, B and C, respectively. The maximum values of annual average sedimentation rates were 2.286 cm/a and 2.000 cm/a in cores A and B, respectively. The implement of the household contract responsibility in the period, farmers strongly worked on the land, at the same time, the rainfall was heavily. The combination made strongly soil erosion in the Longxi catchment and sedimentation rate in the Changshou reservoir. The higher values of annual average sedimentation rates were 1.778 cm/a, 1.778 cm/a and 1.111 cm/a in cores A, B and C, respectively in 1989-1997. The probable reason was that human disturbance of soil surface in the early period of the implementation of returning farmland to forest and grassland, building terraces and so on made unstable soil surface to cause soil erosion easily. The lower values of annual average sedimentation rates were 1.556 cm/a, 0.444 cm/a and 0.667 cm/a in cores A, B and C, respectively in 2005-2013 due to the increase of vegetation coverage to improve environment and weaken soil erosion.Sediment below a depth of 92 cm, 66 cm and 38 cm in cores A, B and C, respectively was coarse, and this reflected the original base of the reservoir while the Changshou dam was completed. The bank erosion inputs occurred possibly as a result of soil collapse in the submerged portions and this material was delivered directly into the reservoir and deposited. Since the depths of 40 cm, 24 cm and 14 cm in cores A, B and C, respectively, that is about mid-and late-1980s, the sediment particle was coarse due to the comprehensive influence of strongly disturbance on the land by the household contract responsibility and heavily rainfall erosity by heavily rainfall. At the initial phase of the implementation of returning farmland to forest and grassland soil surface was unstable and surface soil was susceptible eroded to make coarse particle size. Since 2005, sediment particle size was fining due to vegetation coverage increased and soil erosion decreased in the Longxi catchment. (2) The vertical variation and cause analysis of nutrients and heavy metals in the reservoir sediment profilesTOC, TN and TP changed from large to small at the beginning of construction. It was found that surface sediment and soil with rich CNP eroded and ran into the reservoir when the water level was high. With surface bank or/and soil erosion with rich CNP was eroded, the content CNP of the sediment in the reservoir decreased. Since the depth of 40 cm, 24 cm and 14 cm in cores A, B and C, respectively, that was the mid- and late-1980s, TOC, TN and TP increased and showed peaks at the depth of 12-14 cm, 4-6 cm and 6-8 cm. Cage farming had been applied in the reservoir since 1980s, which made waste to accumulate in the reservoir. The local government legislated to forbid fertilizer farming fish and banned it completely in 2005. It showed that the trend in TOC, TN and TP gradually decreased because they released into the water and reduced CNP content in the sediment since 2005. Heavy metal in the sediment from big to small was Zn > Cr > Ni > Pb > Cu > Co > Cd. At the beginning of the Changshou dam was completed in 1956, heavy metals in the sediment had the trend from high values to low under the influence of sediment deposition. Heavy metals in the sediment has a increase tendency in 1989-1998 with gradually increasing of urban sewage and factory waste water in the Longxi catchment. Except Cd, heavy metals increased significantly in 2005-2013. Pearson correlation analysis showed that Cd, Co, Cr, Cu and Ni, and has significant or extremely significant correlation. Principal component analysis found that Cd, Co, Cr, Cu and Ni could explain more than 55% and natural source are the principal influence factor. Zn and Pb had weak correlation and different sources. Zn and Pb were largely driven by urban sewage and factory waste water. Cd was affected by natural and human activities.(3) Sediment source analysisUsing sediment source tracer technology to research the sediment source of the reservoir, sampling method for typical small forest and farm catchment instead of traditional method to increase the representative of soil erosion source. Based on the spatial location of Longxi catchment, the catchment was divided into upstream, midstream and downstream, and based on land use types, the sample types were forest land and farmland. Combination the vertical variation and causes of nutrients and heavy metals, sediment source tracer technologies identify sediment source. The steps, firstly was the optimum recognition statistical filtering factor, secondly combined with the multivariate linear mixed model, finally realized the quantitative portion of sediment on the various sources. Based on the land use types, forest catchment and farm catchment were about 31% and 69%, respectively, and the sediment yield per unit area was 1.43 times in farm catchment than forest catchment and farmland was the mainly sediment source with strongly worked on the farm land. Based on the upstream, midstream and downstream yield, sediment source were 13%, 71% and 16%, respectively. It showed that midstream (Dianjiang) was seriously soil erosion and the governance should take measures to prevent soil erosion and water loss. 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18971
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
高进长. 长寿湖水库沉积泥沙来源的多种示踪研究[D]. 北京. 中国科学院大学,2016.
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