共查询到17条相似文献，搜索用时 125 毫秒
1.
根据长江与黄河各一个完整水文年的调查数据,并结合历史资料分析了我国这两条大型河流活性硅((RSi,RSi=溶解硅(DSi)+生物硅(BSi))的入海通量及长时间序列的变化规律与影响因素.结果表明,长江与黄河RSi的组成存在显著的差异,二者水体中BSi/RSi的平均比值分别为0.22和0.49;黄河DSi的年平均浓度为长江的74%,而BSi年平均浓度却是长江的3倍.黄河水体中相对较高的BSi浓度反映了黄河流域水体浑浊度与土壤侵蚀程度较高,源自黄土高原高的泥沙输送量是导致黄河水体中BSi浓度较长江高的主要原因.长江与黄河下游RSi通量在丰水期、平水期与枯水期的比值分别为5.3∶3.1∶1.6与3.8∶3.4∶2.8,长江半数以上的RSi入海通量是在丰水期输出的,而黄河在3个时期的差异不明显.相比于径流的变化,1958-2014年间长江DSi通量变化主要是由DSi浓度的变化引起的,流域气候变化(如温度变化)是其浓度及其通量年代际变化的重要原因;而黄河1985-2001年间DSi通量下降是由于径流量与DSi浓度降低的双重原因引起的.气候变化,特别是温度的变化会对流域硅的风化速率与硅的产出产生重要影响,但其具体的影响有待进一步揭示. 相似文献
2.
《中国科学:地球科学》2015,(7)
分析了黄河水体中悬浮颗粒物(SPM)、溶解硅(DSi)、生物硅(BSi)、植硅体和其他相关参数,旨在揭示自然过程与人为活动对黄河输送硅的影响.结果表明,黄河中溶解硅浓度自1986年以来明显下降;1986~2010年,约有34%的溶解硅因土壤侵蚀的减少而滞留在黄河流域.来源于高等植物的植硅体占河流生物硅的67.2%~96.3%,并以平滑棒形为主要形态.由于含沙量大,黄河生物硅浓度普遍高于世界其他河流,在近黄河口处的利津站位,BSi/(BSi+DSi),BSi/SPM比值分别为0.5和0.003,这表明黄河悬浮颗粒物携带的生物硅是河流输送硅的一个重要组成部分.黄河中相对较高的生物硅含量反映了黄河流域浑浊度与土壤侵蚀程度较高;源自黄土高原巨大的泥沙通量可能是导致黄河中生物硅含量较高的原因,这与世界河流系统生物硅通量随产沙模数增大而增加的趋势相一致.在黄河口外的渤海沉积物中的生物硅也主要由植硅体所构成,平滑棒形同样是其主要的形态.研究表明,由河流输送的生物硅主要由来源于表层土壤侵蚀的植硅体所构成,其也是近岸水域硅生物地球化学循环的重要部分. 相似文献
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长江流域水库"过滤器效应"对入海溶解硅通量的影响 总被引：3，自引：2，他引：1
根据1960-2000年间长江大通水文站记录的水、沙以及硅、氮、磷等数据,结合1954-2006年间长江流域库容大于108 m3的162座水库的库容、上游径流量、总磷等数据,利用Vollenweider模型分析了水库"过滤器效应"对入海溶解硅(DSi)通量的影响.结果表明:1)1990s相比1960s,长江入海DSi通量下降了约1.85×106 t/a,减少了大约25.3%;入海DSi通量的下降与流域径流波动、入海悬沙通量下降以及溶解无机氮通量的增加紧密相关.2)流域水库明显改变径流的自然过程,增加径流的滞留时间,流域90%以上的水库对上游径流的滞留时间超过0.05年,水库产生显著的DSi"生物过滤器"效应.模型计算显示流域大型水库对DSi的累计滞留量可达0.85×106 t/a,占年均入海DSi通量(1990-2000年)5.4×106 t的15.7%,是入海DSi通量减少量(1.85×106 t/a)的45.9%.3)根据保守估计,流域162座大型水库内泥沙累计淤积量达6.75×108 t/a,不仅使悬沙入海通量显著下降,而且造成大量颗粒吸附的外源和内源DSi颗粒沉淀,这对入海DSi通量减少也起到重要贡献.但目前对水库"泥沙过滤器"的滞留机理并不清楚,需要展开进一步的研究. 相似文献
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江西柘林水库是长江中游的大型峡谷型旅游性水库,库容79.2×10~8m~3,长115 km.2015年4月在56 km的中心库区走航和定点测量了水库表层水体浮游藻类、叶绿素a(Chl.a)浓度与溶解无机氮(DIN)浓度、溶解无机磷(DIP)浓度、溶解硅(DSi)浓度、水温、浊度和溶解氧浓度等环境因子的分布特征.结果表明:1)水库属于中营养水体,表层主要浮游藻类(细胞丰度1000 cells/L)有34种,平均生物量为0.41 mg/L.主要优势藻类(优势度≥0.02)为硅藻和蓝藻,藻类组成与DIN浓度、DIP浓度、DSi浓度和水温等环境因子关系密切,4种因子对藻类结构的解释水平达60%以上.2)水库水体Chl.a浓度具有显著的次表层叶绿素最大值(SCM)现象,SCM层深度为3~8 m,厚度为2~7 m,SCM层占整个水体的25.2%~74.1%.SCM层的藻类对营养盐吸收消耗致使DIN、DIP和DSi浓度下降,同时藻类的产氧使溶解氧浓度增加.3)水库对DSi具有显著的生物过滤器效应,中、上层约有11%~12%的DSi被生物吸收利用,从上游至下游,累积约有21%的DSi被藻类吸收沉降于库底.4)人类氮、磷排放对水库生态和水质有严重影响,毗邻县城区域水体的Chl.a和DIP浓度分别是自然河段的2.9倍和3倍左右. 相似文献
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三峡水库对长江N、P营养盐截留效应的模型分析 总被引：23，自引：2，他引：21
在长江流域干支流NP营养盐现场观测资料的基础上利用模式分析的方法分析了三峡水库对上游营养盐的截流效应. 三峡水库投入使用后发育出的水库生态系统可将上游输入的2%-7%溶解态无机氮和13%-42%的溶解态无机磷固定于浮游生物中库区水体中生物有机碳总量可保持在0.84109-2.65109mol的范围. 相应地三峡工程可减缓长江下游及长江口区的富营养化趋势但却在一定程度上加剧了长江中下游营养盐N/P比上升的趋势. 相似文献
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流域场镇发展下三峡水库典型入库河流水体碳、氮、磷时空特征及富营养化评价 总被引：2，自引：0，他引：2
流域场镇式发展是三峡地区城乡统筹发展的重要模式,通常形成河流两岸串珠状的场镇分布格局,这种人类活动的点状聚集特征对入库河流水环境的综合影响并不清楚.选择三峡库区流域场镇发展特征明显的黑水滩河及主要支流为研究对象,于2014年9月至2015年6月期间对流域内分布的主要场镇前后的水体进行碳、氮、磷浓度的监测分析,探讨场镇分布对流域水体生源要素时空格局的影响.研究结果表明,黑水滩河干、支流水体总有机碳(TOC)和溶解性有机碳浓度为4.5~39.2和3.2~31.4 mg/L,总氮(TN)、铵态氮和硝态氮浓度范围为1.12~6.96、0.87~5.00和0.073~0.881 mg/L,总磷(TP)、溶解性总磷和正磷酸盐浓度范围为0.078~0.454、0.049~0.310和0.025~0.222 mg/L,不同形态的碳、氮、磷含量变化幅度较大;黑水滩河干、支流流经不同场镇区前后,水体各形态碳、氮、磷浓度均不同程度增加(其中TOC、TN和TP的增幅范围分别为4.7%~61.3%、26.7%~144.7%和12.8%~50.7%),而在无场镇分布的干流河段,水体碳浓度变化不大,氮、磷浓度明显降低,表明水体生源要素的空间变异特征受到流域场镇分布格局与河流自净能力的双重影响,导致黑水滩河干流自上游向下游碳浓度呈“阶梯式”增长,氮、磷浓度呈“波动式”增长;相关分析显示,流域水体碳、氮、磷浓度均呈极显著的正相关关系,即场镇发展模式下河流水体污染物呈同步变化的趋势,表明山地河流流域内串珠状场镇发展模式导致从上游向下游水体污染物呈明显的累积效应,并进一步超出水体自净能力,造成下游水体恶化.河流碳、氮、磷浓度的季节变化主要受径流稀释作用影响,表现为夏秋季低、春季高的模式;富营养化综合指数表明,黑水滩河各监测断面全年属于富营养状态以上,表层水体氮污染严重,磷污染较轻;初步估算黑水滩河每年向三峡水库输入TOC、TN、TP通量达4057、1001和47 t,对三峡水库水环境安全具有严重威胁.三峡库区沿河串珠状场镇式发展形成了一种“点面”双重特征的污染模式,未来河流水环境污染防控中应予以关注. 相似文献
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高锰酸盐指数是我国水环境质量评价和污染控制考核的重要指标,其浓度高低能反映水体受到有机物污染的严重程度.2003年三峡水库投入运行后,长江中下游干流水文情势发生了重大变化.为此,研究了长江中下游干流耗氧有机污染物的典型参数——高锰酸盐指数的时空变化特征.结果表明,长江中下游干流水体：2004年以来,高锰酸盐指数总体趋降,且目前已处于较低水平并趋于稳定;不同江段和水期高锰酸盐指数变化趋势不一致;耗氧有机污染物以溶解态为主,且溶解态所占比例沿程趋于降低,南津关、汉口、吴淞口下23 km断面溶解态占比中位值分别为0.862、0.734和0.598;可沉降颗粒物对水体中高锰酸盐指数浓度影响较低,尤其在研究河段上游段,悬浮颗粒中所含耗氧物质占总量比例中位值分别为0.138、0.266和0.402;上游江段水体同一监测断面不同测线和测点间高锰酸盐指数测定值差异不显著;河口段则存在显著差异,尤其是表层和底层之间;沿江城市江段近岸水域水体中耗氧物质污染程度较低,其澄清样中高锰酸盐指数均值在1.91～3.45 mg/L之间,仅局部城市江段和水期出现值高于6.0 mg/L的现象. 相似文献
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总磷是长江流域备受关注的污染物。来自长江上游的物质输送对长江中下游、对入海口水域水生态都具有重要影响。研究了1998—2019时期长江上游和中下游之间的衔接断面暨三峡水库出水断面的磷通量及形态变化。整个研究时段分为3个阶段:1998—2002(阶段Ⅰ,三峡水库运行之前),2003—2013(阶段Ⅱ,作为过渡时期)及2014—2019(阶段Ⅲ,三峡水库实现175m正常蓄水位且金沙江下游段向家坝和溪洛渡水库运行后),以阶段Ⅰ、Ⅲ为重点时段进行对比分析。研究表明,2014—2019年总磷年通量平均为5.67万t/a,比1998—2002年减少了38.0%;溶解态磷年通量为4.02万t/a,增加了60.0%;颗粒态磷年通量为1.67万t/a,减少了74.9%。磷的主导形态由颗粒态变为溶解态,溶解态磷通量占比由27.5%上升为70.9%;相应地,颗粒态磷通量占比由72.5%下降为29.1%。总磷、溶解态磷和颗粒态磷通量均表现为丰水期>平水期>枯水期。近20年来,水沙关系发生了巨大变化,含沙量(SS)与水量(Q)正相关性大幅下降,其拟合方程的斜率由1.44下降为0.10,R2... 相似文献
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三峡水库成库后水体中CODMn、BOD5空间变化 总被引：7，自引：0，他引：7
根据2004年2、5、8月,三峡水库成库后6个水平断面、4个垂直断面采样分析,对水体水质参数、DO以及CODMn和BOD5的水平分布和垂直分布进行了研究.研究结果表明,成库后BOD5达到国家地表水Ⅰ类标准,CODMn不同季节变化较大,水质范围在Ⅱ-Ⅳ类标准.BOD5、CODMn变化范围分别在0.1-1.3 mg/L,1.8-6.3 mg/L,受三峡水库成库的影响,水平分布上,DO、CODMn、BODs在成库区域低于上游区;CODMn含量丰水期＞平水期＞枯水期;BODs浓度降低主要与污染物停留时间变长有关,CODMn主要是与泥沙沉积有关.垂直分布上,污染物3个层次变化不显著,未出现分层现象.枯水期、平水期、丰水期颗粒态含量占总CODMn范围分别为5.5%-27.3%,9.1%-28.8%,48.6%-78.3%.三峡水库对CODMn、BOD5有净化作用,枯水期成库区域通量CODMn、BODs比上游区降低44%、76%,平水期降低13.5%,32%,丰水期降低31.8%、19.1%.各采样站点有机物通量和流量有显著的相关性.大宁河库湾受浮游藻类生长的影响,DO饱和率高于干流库区. 相似文献
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This paper summarizes the latest developments, future prospects, and proposed countermeasures of reservoir sedimentation and channel scour downstream of the Three Gorges Reservoir (TGR) on the Yangtze River in China. Three key results have been found.(1) The incoming sediment load to the TGR has been significantly lower than expected.(2) The accumulated volume of sediment deposition in the TGR is smaller than expected because the overall sediment delivery ratio is relatively low, and the deposition in the near-dam area of the TGR is still developing.(3) River bed scour in the river reaches downstream of the Gezhouba Dam is still occurring and channel scour has extended to reaches as far downstream as the Hukou reach. Significantly, sedimentation of the TGR is less problematic than expected since the start of operation of the TGR on the one hand;on the other hand, the possible increases in sediment risks from dependence on upstream sediment control, deposition in the reservoir, and scour along middle Yangtze River should be paid more attention.(1) Sediment trapped by dams built along the upper Yangtze River and billion tons of loose materials on unstable slopes produced by the Wenchuan Earthquake could be new sediment sources for the upper Yangtze River. More seriously, possible release of this sediment into the upper Yangtze River due to new earthquakes or extreme climate events could overwhelm the river system, and produce catastrophic consequences.(2) Increasing sediment deposition in the TGR is harmful to the safety and efficiency of project operation and navigation.(3) The drastic scour along the middle Yangtze River has intensified the down-cutting of the riverbed and erosion of revetment, it has already led to increasing risk to flood control structures and ecological safety. It is suggested to continue the Field Observation Program, to initiate research programs and to focus on risks of sedimentation. 相似文献
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Should the Three Gorges Dam be blamed for the extremely low water levels in the middle–lower Yangtze River? 
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下载免费PDF全文 Extremely low water level events have frequently occurred in the middle–lower Yangtze River (MLYR) in recent years (2006–2011). Most of these drought events coincided with the initial operation of the Three Gorges Dam (TGD). The TGD was therefore the focus of controversy about the causes of the hydrological droughts of the rivers and lakes of the region. We quantified the effects of the TGD's operation on water levels from 2006 to 2011 using a newly developed hydrodynamic model. The operation of the TGD significantly exacerbated the severe hydrological droughts that occurred in late September to November because of water impoundment, but it increased water levels from April to early June in the MLYR because of the drawdown of TGD water levels. Evidence suggests that the recent extremely low water levels were mainly because of the remarkable decline in inflows to the MLYR resulting from precipitation changes and possible human activities. Nevertheless, it should be noted that the effects of the TGD on downstream rivers and lakes will be intensified in the foreseeable future. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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The impact of silt trapping in large reservoirs on downstream morphology: the Yangtze River 总被引：2，自引：0，他引：2
The sediment load of the Yangtze River (China) is decreasing because of construction of dams, of which the Three Gorges Dam (TGD) is the best known example. The rate of the decline in sediment load is well known, but changes in the sediment grain size distribution have not been given much attention. The TGD mostly traps sand and silt while clay is flushed through the reservoir. A large amount of sand is available in the Yangtze River downstream of the reservoir, and therefore the pre-dam sand concentration is not substantially reduced. The availability of silt on the Yangtze River bed is limited, and it is expected that most silt will be removed from the riverbed within one to two decades. In order to evaluate the impact of the change in grain size distribution on the tidal flats of the Yangtze Estuary, a highly schematized tidal flat model is setup. This model broadly reveals that the observed deposition rates are exceptionally large because of the high sediment concentration, the abundance of silt, the seasonal dominance of waves (shaping a concave profile), and the offshore tidal asymmetry. The model further suggests that deposition rates will be limitedly influenced by reductions in clay or fine silt but strongly impacted by reductions in median to coarse silt. The response of the downstream morphology to reservoir sedimentation therefore strongly depends on the type of trapped sediment. As a consequence, silt-dominated rivers, such as the Yangtze River and the Yellow River may be more strongly impacted than sand-dominated systems. 相似文献
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Dejiang Fan Hongyan QiXiaoxia Sun Yong LiuZuosheng Yang 《Continental Shelf Research》2011,31(2):129-137
Annual sedimentary layers in core A from the Yangtze River (Changjiang) subaqueous delta were identified based on high-resolution biogenic silica (BSi) and grain-size records. The contents of BSi, the sediment grain-size and the sensitive grain-size fractions of <13.14 μm and 13.14-250 μm illustrated steady coincident fluctuations with the depth profile of core A. These fluctuations were inferred to reflect seasonal changes in physical and biological processes. For example, variations in the content of BSi likely represent changes in primary production in flood versus dry seasons. It in flood seasons was several times higher than that in dry seasons. The amounts of <13.14 and 13.14-250 μm fractions were complimentary to each other and co-varied with the BSi amount. Therefore, the BSi, grain-size and sensitive fractions can be used as proxies for the annual sedimentation. From 1992 to 2005, the estimated sedimentary rate based on the annual layer varied from 1.0 to 3.5 cm/a (mean of 2.07 cm/a), and these values varies with the annual sediment discharge from the Yangtze River to the sea. The significant seasonal variations in the water discharge, sediment load, ocean hydrodynamics and primary production, which are common in the area affected by the East Asian monsoon, are likely responsible for the formation of the annual sedimentary lamination. 相似文献
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The impact of Three Gorges Reservoir refill operation on water levels in Poyang Lake,China 总被引：1，自引：1，他引：0
The refill operation of Three Gorges Reservoir (TGR) in the end of flood season significantly alters the water level regimes in Poyang Lake by reducing Yangtze River flow discharge. This study aims to investigate the impact of TGR refill operation on water level probability distribution of the Poyang Lake. The multiple linear regression model was established to estimate the water level with catchment inflow and Yangtze River flow as explanatory variables. A probability distribution of water level was derived and the refill operation effects were quantified by comparing the water level distribution at Xingzi station in the Poyang Lake before and after TGR. It is revealed that Yangtze River flow, rather than the catchment inflow is the dominant factor affecting the water level of Poyang Lake during TGR refill operation period. Results also show that the water level distribution estimated by the derived distribution method can be accepted as a theoretical distribution and has a comparable accuracy as the directly fitted distribution method before TGR. The derived method can be adapted to the environment change, thus is well suited for estimating the water level distribution after TGR. It is observed that Xingzi water levels with different design frequencies have been reduced due to the TGR refill operation. The water level reductions induced by TGR refill operation are 1.28, 0.87, and 0.50 m corresponding with design frequencies of 50, 90 and 99 %, respectively. The results from this work would improve the understanding of the TGR effects on the downstream river–lake system and provide scientific evidences for formulating better scheme for water resources management in this region. 相似文献
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A framework to assess the cumulative impacts of dams on hydrological regime: A case study of the Yangtze River 下载免费PDF全文
下载免费PDF全文 Comparisons of flow time series between preimpact and postimpact periods have been widely used to determine hydrological alterations caused by reservoir operation. However, preimpact and postimpact periods might also be characterized by different climatological properties, a problem that has not been well addressed. In this study, we propose a framework to assess the cumulative impact of dams on hydrological regime over time. The impacts of the Three Gorges Dam (TGD) on the flow regime of the Yangtze River were investigated using this framework. We reconstructed the unregulated flow series to compare with the regulated flow series during the same period (2010 to 2015). Eco‐surplus and eco‐deficit and the Indicators of Hydrologic Alteration (IHA) parameters were used to examine hydrological regime change. Among 32 IHA parameters, Wilcoxon signed‐rank test and principal component analysis identified the October median flow, 1‐ and 3‐day maximum flows, 1‐day minimum flow, and rise rate as representative indicators of hydrological alterations. Eco‐surplus and eco‐deficit showed that the reservoir also changed the seasonal regime of the flows by reducing autumn flow and increasing winter flow. Changes in annual extreme flows and October flows lead to negative ecological implications downstream of the TGD. Ecological considerations should be taken into account during operation of the TGD in order to mitigate the negative effects on the fluvial ecosystem in the middle reach of Yangtze River. The framework proposed here could be a robust method to assess the cumulative impacts of reservoir operation over time. 相似文献