IMHE OpenIR  > 山地表生过程与生态调控重点实验室
三峡库区小流域泥沙来源复合指纹识别研究
Alternative TitleSediment Source Fingerprinting for a small Agricultural Catchment in the Three Gorges Reservoir Region
Language中文
郭进
Thesis Advisor文安邦
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline土壤学
Abstract三峡库区一直被认为是我国水土流失最严重的地区之一,本区侵蚀泥沙问题备受关注。由于研究基础薄弱、手段有限,许多重要结论,仍需要进一步研究探讨。深入系统的案例研究是区域侵蚀泥沙研究所缺少的。本研究以三峡库区忠县境内申家河小流域(34.09 km2)为对象,利用复合指纹识别技术结合核素示踪技术(沉积物137Cs、210Pbex法计年),开展流域泥沙来源的定量研究。    本研究是利用复合指纹识别技术结合核素示踪技术开展库区小流域侵蚀泥沙及其来源定量研究的一次尝试。论文着眼于研究流域尺度的拓展效应,基于坡面塘库-支流河道-库湾消落带的泥沙输移/赋存路径,探寻流域侵蚀产沙的空间变化。研究内容:① 以山坪塘农业小流域塘库泥沙淤积为对象,重建塘库近代泥沙淤积历史,开展塘库近代沉积泥沙来源及其变化研究,揭示流域侵蚀产沙对土地利用改变的响应;② 开展基于次暴雨事件的库区支流河道悬移质泥沙来源及其过程动态定量解析;③ 针对库区支流消落带泥沙淤积问题,初步尝试使用泥沙来源的指纹识别技术定量解析库湾消落带泥沙来源。主要研究结论如下:    (1) 基于137Cs计年法而建立了塘库沉积泥沙剖面时间序列,137Cs剖面蓄积峰位于深度60 cm处(137Cs活度5.95 ± 0.29 Bq?Kg-1)大致对应于1963年泥沙沉积层。据此估算出塘库泥沙多年平均淤积速率为1.2 cm?a-1。塘库沉积泥沙平均密度取经验值1.28 g?cm-3,试验农业小流域面积0.11 km2,则菱角塘小流域塘库多年平均淤沙模数为378 t?km-2?a-1。    根据塘库沉积物的137Cs法计年及平均沉积速率,可定性划分剖面年代:利用泥沙来源的复合指纹识别技术可定量解析不同泥沙来源。表层10 cm沉积泥沙大致代表最近10年(2003-2013)年间的流域泥沙淤积。其三种土地利用类型泥沙来源之相对输沙贡献率多年平均分别为,旱地82%,撂荒地16%,林地仅2%;多年平均淤沙模数分别为旱地310 t?km-2?a-1,撂荒地60 t?km-2?a-1,林地8 t?km-2?a-1。10-60 cm泥沙大致对应于过去40(1963-2003)年间塘库泥沙淤积。该时段泥沙的两种泥沙来源相对输沙率多年平均值分别为旱地(坡耕地)为85%,林地为15%;则有其多年平均淤沙模数分别为321 t?km-2?a-1,57 t?km-2?a-1。    (2) 流域侵蚀产沙强度受暴雨强度、径流量影响而波动,径流含沙率最大值为0.35(g/L)。河道产流初期,林地、坡耕地、水田三种来源之相对输沙贡献率分别为36%、57%、7%,柑橘园输沙率为0。随着降雨过程持续,坡耕地侵蚀输沙比重始终在71%以上,尤其以径流消退阶段,径流携沙的84% 来自坡耕地。各土地利用类型泥沙来源相对输沙率加权平均分,坡耕地平均相对输沙率77%,其次为林地平均输沙率11%,水田、柑橘园的相对平均输沙率分别8%、4%。拟合优度检验结果表明,混合模型拟合结果相对平均误差为6.4%。故推断水田来沙量微弱,柑橘园侵蚀产沙可以忽略。    两种主要土壤类型泥沙来源区域的输沙比重并不固定。流域内紫色土耕作区域作为主要来源贡献了约62% 的泥沙,黄壤耕作区域相对输沙率为38%。在降雨、耕作管理等外部条件基本相似条件下,径流泥沙输移路径可能成为影响流域输沙的关键因素。坡面水系越复杂,输移路径越远,泥沙发生分选和沉积的概率将增加,最终导致输沙量减小。    (3) 相对于流域坡面表土颗粒组成,消落带沉积泥沙粘粒出现富集,富集率为1.65;粉粒含量与坡面土壤组成相近;0.02-0.2mm的细砂含量相比坡面表土有所降低;而0.2-2mm的粗砂部分出现富集,富集率为1.24。两种原因,175m以上发生侵蚀,消落带干湿交替,发生崩塌。分析结果表明,除铅(Cd)、钴(Co)、铬(Cr)和铅(Pb)这四种重金属元素外,其余元素均出现了不同程度的富集,其中富集最严重的铜(Cu),富集率为1.98。    对消落带6个断面河岸两侧采集的12个沉积泥沙表层样(2-3cm)泥沙来源示踪结果表明,林地相对输沙率在24% - 70%之间变化,平均输沙率为43%;流域内坡耕地作为干流消落带沉积泥沙的第二个重要来源,相对输沙贡献率介于7% - 61%,平均相对输沙率为39%。水田、柑橘园平均输沙比重分别为2%、16% ,仅部分消落带沉积泥沙样点中能发现以上来源。林地成为消落带沉积泥沙的主要来源(43%),这与通常的认识相矛盾,而柑橘园平均输沙比重占到16%,异常偏高。干流河道消落带泥沙,除来源于悬移质泥沙沉积,还有可能受到河水倒灌影响;另外,消落带175m水位以上坡面林地侵蚀泥沙在消落带沉积可能导致了林地输沙比重升高。    各沉积空间点两种土壤类型泥沙来源并不固定,紫色土相对输沙贡献率3% - 100%,而黄壤相对输沙贡献率0 - 97%。库湾断面消落带12个沉积泥沙样不同土壤类型来源相对输沙贡献率算术平均结果, 紫色土区域的侵蚀产沙59%,黄壤区域平均侵蚀输沙贡献率约为41%。支流悬移质的62% 源于紫色土区域,而黄壤区域输沙贡献仅占38%,悬移质泥沙与消落带沉积泥沙的两中土壤类型来源区域输沙比重基本相似。    (4)土地利用方式不同,对于地表的改造影响有差;流域尺度变化必然导致侵蚀产沙空间变异。流域侵蚀产沙出现动态变化属必然,泥沙来源也并不固定。利用泥沙来源的复合指纹识别技术,较好解释的基于不同尺度域的区域泥沙来源,揭示了悬移质泥沙来源的内在变异,方法具有一定实用性。
Other AbstractThe Three Gorges Reservoir Region (TGRR) is always considered to be one of the most serious soil erosion areas in our country. Erosion and sediment problems in this area have attracted increased attention by many researchers.Due tow eak basal researches and limited means, many important conclusions still needs the further research study.In-depth and systematic case study is the kind of research that regional erosion and sediment has been lacking.The research selected the Shenjiahe watershed (34.09 km2) in the Zhongxian county in the TGRR area as the research objects and used composite fingerprinting technique-based , nuclide tracer technique by 137Cs and 210Pbex dating method of pond and reservoir deposits as supplement in order to quantifying catchment scale sediment source.    This research attempts to use combine composite fingerprinting technique with nuclide tracer technique in order to solve erosion and sediment problems of small watershed in TGRR and quantifying catchment scale sediment source. The research focused on effects of watershed scale extension and based on sediment transport or occurrence way of slope pond-trunk stream- tributaries water level fluctuating to explore spatial change of land use change on sediment yield in the catchment. The research involve: 1.The research selected reservoir silting of pond sediment from a agricultural catchment as the research objects and explored source and variation of modern sediment deposited to uncover how about pond sediment effects on land use patterns change of watershed.2. The research explored the source of pond tributaries water suspended sediment of individual rainfall events and dynamically procedure quantitative analysis.3. For pond tributaries water level fluctuating reservoir silting problem, the research used quantifying catchment scale sediment source to analysis the the source of pond tributaries water suspended sediment. The main results and conclusion are as follows:    (1)The land use 137Cs dating method to build a time series of pond and reservoir deposits section.Peak of 137Cs section accumulation is located in the depths of 60cm(137Cs activity 5.95±0.29 Bq?Kg-1), which corresponds sediments deposition in 1963. Accordingly, the research estimated that the average speed of deposition of pond sediment over the years are 1.2 cm?a-1.Based on average density of pond and reservoir deposites are empirical value of1.28 g?cm-3 and size of experimental agricultural small catchment is 0.11km2, average deposited sediment modulus of pond small catchment is 378 t?km-2?a-1. Deposited sediment surface above 10cm roughly represents catchment deposited sediment in the last 10 years (2004-2013).The average of sediment transport rate of three type of land use types sediment source were that dry land was 82 percent, wasteland was 16 percent and woodland was just 2 percent. Average deposited sediment modulus were that dry land was 310 t?km-2?a-1, asteland was 60 t?km-2?a-1 and woodland was just 8 t?km-2?a-1. 10-60 cm sediment approximately corresponds to pond deposited sediment in the last 40 years. During this period, the average sediment transport rate of the two types of sediment sources were that dry land was 85 percent and woodland was 15 percent. Average deposited sediment modulus were 321 t?km-2?a-1 and 57 t?km-2?a-1.    (2) Rainfall intensity and river runoff have influence on Watershed erosion and sediment yield strength, the maximum value of runoff sediment is 0.35(g/L). At the beginning of river runoff, sediment transport rate of woodland, slope land and paddy fields were 36%、57%、7% respectively, but the orchards was 0.As rain fell,the proportion of deposited sediment transport of slope cropland always was more than 71%. Especially in the period of runoff fading, 84 percent of runoff carrying come from slope cropland.Source of all land use types sediment transport rate weighted average. The average of sediment transport rate of slope cropland was 77%. Next is se
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7857
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
郭进. 三峡库区小流域泥沙来源复合指纹识别研究[D]. 北京. 中国科学院研究生院,2014.
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