Biogeochemistry of dissolved carbon,major, and trace elements during spring flood periods on the Ob River     

Sergey N. Vorobyev  Oleg S. Pokrovsky  Larisa G. Kolesnichenko  Rinat M. Manasypov  Liudmila S. Shirokova  Jan Karlsson  Sergey N. Kirpotin 《水文研究》2019,33(11):1579-1594

Detailed knowledge of the flood period of Arctic rivers remains one of the few factors impeding rigorous prediction of the effect of climate change on carbon and related element fluxes from the land to the Arctic Ocean. In order to test the temporal and spatial variability of element concentration in the Ob River (western Siberia) water during flood period and to quantify the contribution of spring flood period to the annual element export, we sampled the main channel year round in 2014–2017 for dissolved C, major, and trace element concentrations. We revealed high stability (approximately ≤10% relative variation) of dissolved C, major, and trace element concentrations in the Ob River during spring flood period over a 1‐km section of the river channel and over 3 days continuous monitoring (3‐hr frequency). We identified two groups of elements with contrasting relationship to discharge: (a) DIC and soluble elements (Cl, SO₄, Li, B, Na, Mg, Ca, P, V, Cr, Mn, As, Rb, Sr, Mo, Ba, W, and U) negatively correlated (p < 0.05) with discharge and exhibited minimal concentrations during spring flood and autumn high flow and (b) DOC and particle‐reactive elements (Al, Fe, Ti, Y, Zr, Nb, Cs, REEs, Hf, Tl, Pb, and Th), some nutrients (K), and metalloids (Ge, Sb, and Te), positively correlated (p < 0.05) with discharge and showed the highest concentrations during spring flood. We attribute the decreased concentration of soluble elements with discharge to dilution by groundwater feeding and increased concentration of DOC and particle‐reactive metals with discharge to leaching from surface soil, plant litter, and suspended particles. Overall, the present study provides first‐order assessment of fluxes of major and trace elements in the middle course of the Ob River, reveals their high temporal and spatial stability, and characterizes the mechanism of river water chemical composition acquisition.  相似文献   

Comparison of trends in stream water quality     

J. M. Potts  D. Hirst  J. D. Miller  A. C. Edwards  D. A. Elston 《水文研究》2003,17(12):2449-2462

A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying trend. The method involves fitting the model twice, once with the underlying trends constrained to be identical for each river and once with the trends unconstrained. Statistical properties are assessed by simulation methods that allow for the autocorrelation in the residuals from the unconstrained fit. The method is applied to data from two streams in the Balquhidder catchments in the Highlands of Scotland and to data from the Dee, Don and Ythan rivers in the north‐east of Scotland. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

河道入湖污染物量计算精度分析   总被引：1，自引：0，他引：1  

马倩  冯昕 《湖泊科学》2012,24(5):663-666

入湖污染物量计算精度的高低决定入湖污染物量分析结果的客观性和准确性.本文以太湖为例,分析2010年环太湖河道入湖污染物量、时空分布情况及多年环太湖河道入湖染污物量变化情势.在此基础上,使用现在已有监测条件分析时段内每日水量水质监测数据计算逐日入湖污染物量时段累积值,并以此作为现有分析计算河道入湖污染物量的最高计算精度值.通过设定不同监测方案、采用不同计算方法分析河道入湖污染物量及其计算精度,认为现有分析计算的河道入湖污染物量已是每日河道水量水质同步监测下河道入湖污染物量的80%左右.针对河道入湖污染物量计算精度的分析可为制定科学的河道入湖污染量监测方案、提高河道入湖污染物量计算精度提供技术支撑.  相似文献   

巢湖四条入湖河流硝态氮污染来源的氮稳定同位素解析   总被引：6，自引：1，他引：5  

刘姝  孔繁翔  蔡元锋  阳振  王济奎  史小丽 《湖泊科学》2012,24(6):952-956

采用氮稳定同位素技术对巢湖四条主要污染输入河流(南淝河、十五里河、派河和双桥河)的氮污染状况和硝态氮来源进行研究.结果表明,巢湖四条入湖河流氮污染最严重的是十五里河,其次是南淝河和派河,双桥河的污染相对较轻.硝态氮的稳定同位素分析结果表明,巢湖四条入湖河流的硝态氮污染物在季节上受到不同因子的影响.十五里河和南淝河的硝态氮污染主要来源于城市生活污水和工业废水;派河的硝态氮污染在冬季主要来源于工业废水,春季来源于农业面源,而在夏季主要受到雨水的影响;双桥河的硝态氮污染冬、春季主要来源于农业面源,夏季主要受雨水的影响.此外本研究结果还表明巢湖四条主要入湖河流的氮污染源主要为铵态氮,因此今后要对铵态氮的来源进行同位素示踪.  相似文献   

基于多源资料的一次弓状强飑线成熟结构研究     

孙玉婷  李红莉  汪小康  康兆萍  肖艳姣  林建 《气象科学》2023,43(5):632-642

利用局地分析和预报系统(Local Analysis and Prediction System, LAPS),结合多源资料,分析了2018年3月4日暖区强飑线成熟阶段的热动力结构和大风形成机制。结果表明：暖区内层结不稳定范围向东扩展和强的垂直风切变,驱动飑线组织化加强并向前移动和发展。成熟阶段飑线热动力结构呈现出两支强入流和冷池的典型特征,即前侧入流在低层(0～3.0 km)辐合上升,部分气流在高层翻转流向系统前侧,无后向流出;后侧中层(4.0～5.5 km)入流进入云体后部,在水凝物强烈相变降温作用下,密度增大转而下沉;下沉气流区降雨蒸发冷却增强了雷暴冷池。相比于飑线南段单一的对流线,北段弓形特点突出,后侧入流下降,加之存在尾随层状云,有更大的潜在冷却作用,促进气流加速下沉增强地面雷暴高压,最终导致更强的极端大风。  相似文献   

Spillage sedimentation on large river floodplains          下载免费PDF全文

John Lewin  Philip J. Ashworth  Robert J. P. Strick 《地球表面变化过程与地形》2017,42(2):290-305

Active deposition across the floodplains of large rivers arises through a variety of processes; collectively these are here termed ‘spillage sedimentation’. Three groups of 11 spillage sedimentation styles are identified and their formative processes described. Form presences on large river floodplains show different combinations of active spillage styles. Only some large floodplains have prominent levees; some have coarse splays; many have accessory channel dispersion and reworking, while still‐water sedimentation in lacustrine environments dominates some lower reaches. Infills are also commonly funnelled into prior, and often linear, negative relief forms relating to former migration within the mainstream channel belt. Shuttle Radar Topography Mission (SRTM) and Landsat 8 data are used to map spillage form types and coverage along a 1700 km reach of the Amazon that has an active floodplain width of up to 110 km with a systematic character transformation down‐valley. Spillage forms associated directly with mainstream processes rarely account for more than 5% of the floodplain deposits. There is a marked decrease in floodplain point bar complexes (PBC) over 1700 km downstream (from 34% to 5%), and an increase in the prevalence of large water bodies (2% to 37%) and accompanying internal crevasses and deltas (0% to 5%). Spillage sedimentation is likely within the negative relief associated with these forms, depending on mainstream sediment‐laden floodwater inputs. Spillage style dominance depends on the balance between sediment loadings, hydrological sequencing, and morphological opportunity. Down‐river form sequences are likely to follow gradient change, prior up‐river sediment sequestration and the altered nature of spilled loads, but also crucially, local floodplain relief and incident water levels and velocities at spillage times. Considering style distribution quantitatively, as a spatially distributed set of identifiable forms, emphasizes the global variety to spillage phenomena along and between large rivers. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Wood and sediment storage and dynamics in river corridors          下载免费PDF全文

Ellen Wohl  Daniel N. Scott 《地球表面变化过程与地形》2017,42(1):5-23

Large wood along rivers influences entrainment, transport, and storage of mineral sediment and particulate organic matter. We review how wood alters sediment dynamics and explore patterns among volumes of in‐stream wood, sediment storage, and residual pools for dispersed pieces of wood, logjams, and beaver dams. We hypothesized that: volume of sediment per unit area of channel stored in association with wood is inversely proportional to drainage area; the form of sediment storage changes downstream; sediment storage correlates with wood load; the residual volume of pools created in association with wood correlates inversely with drainage area; and volume of sediment stored behind beaver dams correlates with pond area. Lack of data from larger drainage areas limits tests of these hypotheses, but the analyses suggest that sediment volume correlates positively with drainage area and wood volume. The form of sediment storage in relation to wood appears to change downstream, with wedges of sediment upstream from jammed steps most prevalent in small, steep channels and more dispersed sediment storage in lower gradient channels. Pool volume correlates positively with wood volume and negatively with channel gradient. Sediment volume correlates well with beaver pond area. More abundant in‐stream wood and beaver populations present historically equated to greater sediment storage within river corridors and greater residual pool volume. One implication of these changes is that protecting and re‐introducing wood and beavers can be used to restore rivers. This review of the existing literature on wood and sediment dynamics highlights the lack of studies on larger rivers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The effect of lithology on valley width,terrace distribution,and bedload provenance in a tectonically stable catchment with flat‐lying stratigraphy          下载免费PDF全文

Amanda Keen‐Zebert  Mark R. Hudson  Stephanie L. Shepherd  Evan A. Thaler 《地球表面变化过程与地形》2017,42(10):1573-1587

How rock resistance or erodibility affects fluvial landforms and processes is an outstanding question in geomorphology that has recently garnered attention owing to the recognition that the erosion rates of bedrock channels largely set the pace of landscape evolution. In this work, we evaluate valley width, terrace distribution, and bedload provenance in terms of reach scale variation in lithology in the study reach and discuss the implications for landscape evolution in a catchment with relatively flat‐lying stratigraphy and very little uplift. A reach of the Buffalo National River in Arkansas was partitioned into lithologic reaches and the mechanical and chemical resistance of the main lithologies making up the catchment was measured. Valley width and the spatial distribution of terraces were compared among the different lithologic reaches. The surface grain size and provenance of coarse (2–90 mm) sediment of both modern gravel bars and older terrace deposits that make up the former bedload were measured and defined. The results demonstrate a strong impact of lithology upon valley width, terrace distribution, and bedload provenance and therefore, upon landscape evolution processes. Channel down‐cutting through different lithologies creates variable patterns of resistance across catchments and continents. Particularly in post‐tectonic and non‐tectonic landscapes, the variation in resistance that arises from the exhumation of different rocks in channel longitudinal profiles can impact local base levels, initiating responses that can be propagated through channel networks. The rate at which that response is transmitted through channels is potentially amplified and/or mitigated by differences between the resistance of channel beds and bedload sediment loads. In the study reach, variation in lithologic resistance influences the prevalence of lateral and vertical processes, thus producing a spatial pattern of terraces that reflects rock type rather than climate, regional base level change, or hydrologic variability. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Normal fault growth and linkage in the Gediz (Alaşehir) Graben,Western Turkey,revealed by transient river long‐profiles and slope‐break knickpoints          下载免费PDF全文

Emiko Kent  Sarah J. Boulton  Alexander C. Whittaker  Iain S. Stewart  M. Cihat Alçiçek 《地球表面变化过程与地形》2017,42(5):836-852

The Gediz (Ala?ehir) Graben is located in the highly tectonically active and seismogenic region of Western Turkey. The rivers upstream of the normal fault‐bounded graben each contain a non‐lithologic knickpoint, including those that drain through inferred fault segment boundaries. Knickpoint heights measured vertically from the fault scale with footwall relief and documented fault throw (vertical displacement). Consequently, we deduce these knickpoints were initiated by an increase in slip rate on the basin‐bounding fault, driven by linkage of the three main fault segments of the high‐angle graben bounding fault array. Fault interaction theory and ratios of channel steepness suggest that the slip rate enhancement factor on linkage was a factor of 3. We combine this information with geomorphic and structural constraints to estimate that linkage took place between 0.6 Ma and 1 Ma. Calculated pre‐ and post‐linkage throw rates are 0.6 and 2 mm/yr respectively. Maximum knickpoint retreat rates upstream of the faults range from 4.5 to 28 mm/yr, faster than for similar catchments upstream of normal faults in the Central Apennines and the Hatay Graben of Turkey, and implying a fluvial landscape response time of 1.6 to 2.7 Myr. We explore the relative controls of drainage area and precipitation on these retreat rates, and conclude that while climate variation and fault throw rate partially explain the variations seen, lithology remains a potentially important but poorly characterised variable. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The formation of an anabranching planform in a sandy floodplain by increased flows and sediment load          下载免费PDF全文

Marcin Słowik 《地球表面变化过程与地形》2018,43(3):623-638

Anabranching rivers evolve in various geomorphic settings and various river planforms are present within these multi‐channel systems. In some cases, anabranches develop meandering patterns. Such river courses existed in Europe prior to intensive hydro‐technical works carried out during the last 250 years. Proglacial stream valleys, inherited from the last glaciation, provided a suitable environment for the development of anabranching rivers (wide valleys floors with abundant sand deposits). The main objective of the present study is to reconstruct the formation of an anabranching river planform characterized by meandering anabranches. Based on geophysical and geological data obtained from field research and a reconstruction of palaeodischarges, a model of the evolution of an anabranching river formed in a sandy floodplain is proposed. It is demonstrated that such a river system evolves from a meandering to an anabranching planform in periods of high flows that contribute to the formation of crevasse splays. The splay channels evolve then into new meandering flow paths that form ‘second‐order’ crevasses, avulsions and cutoffs. The efficiency of the flow is maintained by the formation of cutoffs and avulsions preventing the development of high sinuosity channels, and redirecting the flow to newly formed channels during maximum flow events. A comparison with other anabranching systems revealed that increased discharges and sediment loads are capable of forming anabranching planforms both in dryland and temperate climate zones. The sediment type available for transport, often inherited from older sedimentary environments, is an important variable determining whether the channel planform is anabranching, with actively migrating channels, or anastomosing, with stable, straight or sinuous branches. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献