Connectivity of post-fire runoff and sediment from nested hillslopes and watersheds     

Codie Wilson  Stephanie K. Kampf  Sandra Ryan  Tim Covino  Lee H. MacDonald  Hunter Gleason 《水文研究》2021,35(1):e13975

Wildfire increases the potential connectivity of runoff and sediment throughout watersheds due to greater bare soil, runoff and erosion as compared to pre-fire conditions. This research examines the connectivity of post-fire runoff and sediment from hillslopes (< 1.5 ha; n = 31) and catchments (< 1000 ha; n = 10) within two watersheds (< 1500 ha) burned by the 2012 High Park Fire in northcentral Colorado, USA. Our objectives were to: (1) identify sources and quantify magnitudes of post-fire runoff and erosion at nested hillslopes and watersheds for two rain storms with varied duration, intensity and antecedent precipitation; and (2) assess the factors affecting the magnitude and connectivity of runoff and sediment across spatial scales for these two rain storms. The two summer storms that are the focus of this research occurred during the third summer after burning. The first storm had low intensity rainfall over 11 hours (return interval <1–2 years), whereas the second event had high intensity rainfall over 1 hour (return interval <1–10 years). The lower intensity storm was preceded by high antecedent rainfall and led to low hillslope sediment yields and channel incision at most locations, whereas the high intensity storm led to infiltration-excess overland flow, high sediment yields, in-stream sediment deposition and channel substrate fining. For both storms, hillslope-to-stream sediment delivery ratios and area-normalised cross-sectional channel change increased with the percent of catchment that burned at high severity. For the high intensity storm, hillslope-to-stream sediment delivery ratios decreased with unconfined channel length (%). The findings quantify post-fire connectivity and sediment delivery from hillslopes and streams, and highlight how different types of storms can cause varying magnitues and spatial patterns of sediment transport and deposition from hillslopes through stream channel networks.  相似文献   

Evaluation of riverbed magnetic susceptibility for mapping biogeochemical hot spots in groundwater-impacted rivers     

Chen Wang  Martin A. Briggs  Frederick D. Day-Lewis  Lee D. Slater 《水文研究》2021,35(5):e14184

Redox hot spots occurring as metal-rich anoxic groundwater discharges through oxic wetland and river sediments commonly result in the formation of iron (Fe) oxide precipitates. These redox-sensitive precipitates influence the release of nutrients and metals to surface water and can act as ‘contaminant sponges’ by absorbing toxic compounds. We explore the feasibility of a non-invasive, high-resolution magnetic susceptibility (MS) technique to efficiently map the spatial variations of magnetic Fe oxide precipitates in the shallow bed of three rivers impacted by anoxic groundwater discharge. Laboratory analyses on Mashpee River (MA, USA) sediments demonstrate the sensitivity of MS to sediment Fe concentrations. Field surveys in the Mashpee and Quashnet rivers (MA, USA) reveal several discrete high MS zones, which are associated with likely anoxic groundwater discharge as evaluated by riverbed temperature, vertical head gradient, and groundwater chemistry measurements. In the East River (CO, USA), widespread cobbles/rocks exhibit high background MS from geological ferrimagnetic minerals, thereby obscuring the relatively small enhancement of MS from groundwater induced Fe oxide precipitates. Our study suggests that, in settings with low geological sources of magnetic minerals such as lowland rivers and wetlands, MS may serve as a complementary tool to temperature methods for efficiently mapping Fe oxide accumulation zones due to anoxic groundwater discharges that may function as biogeochemical hot spots and water quality control points in gaining systems.  相似文献   

准噶尔盆地玛湖凹陷西斜坡三叠系百口泉组扇三角洲优质储集层预测          下载免费PDF全文

桑林翔  刘军  王贵文  王苏天  李全  张云龙 《古地理学报》2020,22(6):1053-1064

针对准噶尔盆地玛湖凹陷西斜坡风南地区三叠系百口泉组扇三角洲砂岩物性空间变化大、优质储集层(孔隙度大于7.4%,渗透率大于0.05×10^-3μm²)预测难的问题,在沉积岩石学、地震沉积学以及地震反演和解释理论指导下,综合利用测井、岩心和三维地震等资料开展了高精度层序地层划分、沉积微相描述和优质储集层地震反演研究。建立了风南井区四级层序地层格架,明确了扇三角洲多期水进水退的充填过程,指出SSQ3和SSQ5是优质储集层的发育层系;识别出扇三角洲平原分流河道、河道间和扇三角洲前缘水下分流水道、河口坝、席状砂等沉积微相,指出扇三角洲平原是优质储集层发育相带;通过应用高分辨层序地层纵向边界和沉积相横向边界约束,进行分层相控叠后地震波阻抗反演,提升储集层预测精度,在SSQ3和SSQ5预测5个优质储集层发育区,提出3口井的井位建议,钻探均获工业油流。  相似文献   

Day-Night and Gastrointestinal Changes in Winter Feeding Intensity and Prey Composition of Apogon lineatus Inhabiting the Southeastern Waters of Korea     

Park  Joo Myun  Jung  Hae Kun  Lee  Chung Il  Huh  Sung-Hoi 《Ocean Science Journal》2019,54(1):141-146

Ocean Science Journal - Diel and gastrointestinal changes in relation to the feeding intensity and prey composition of Apogon lineatus were investigated through the analysis of the diet contents of...  相似文献   

Temperature-Dependent Bifurcated Seasonal Shift of Phytoplankton Community Composition in the Coastal Water off Southwestern Korea     

Kang  Yoonja  Kang  Hee-Yoon  Kim  Dongyoung  Lee  Young-Jae  Kim  Tae-Ik  Kang  Chang-Keun 《Ocean Science Journal》2019,54(3):467-486

Ocean Science Journal - Coastal water around the archipelago off southwestern Korea has been bathed in an unprecedented pool of warm water in summer in recent years. Here, we examined phytoplankton...  相似文献   

Development of the cyclic p–y curve for a single pile in sandy soil     

Sung-Ha Baek  Joonyoung Kim  Seung-Hwan Lee 《Marine Georesources & Geotechnology》2018,36(3):351-359

Pile foundations that support transmission towers or offshore structures are dominantly subjected to cyclic lateral load induced by wind and waves. For a successful design, it is crucial to investigate the effect of cyclic lateral loads on the pile behavior that is loaded laterally. Although the p–y curve method is generally utilized to design the cyclic laterally loaded pile foundations, the effect of cyclic lateral loads on the pile has not been properly implemented with the p–y curve. This reflects a lack of consideration of the overall stiffness change in soil–pile interaction. To address this, a series of model pile tests were conducted in this study on a preinstalled aluminum flexible pile under various sandy soil conditions. The test results were used to investigate the effect of cyclic lateral loads on the p–y behavior. The cyclic p–y curve, which properly takes into account this effect, was developed as a hyperbolic function. Pseudo-static analysis was also conducted with the proposed cyclic p–y curve, which showed that it was able to properly simulate cyclic laterally loaded pile behavior in sandy soil.  相似文献   

The Effects of Ocean Acidification on Feeding and Contest Behaviour by the Beadlet Anemone <Emphasis Type="Italic">Actinia equina</Emphasis>     

Tess Olivia Bamber  Angus Charles Jackson  Robert Philip Mansfield 《Ocean Science Journal》2018,53(2):215-224

Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO₂ will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems.  相似文献   

Mesozoic mafic magmatism in North China: Implications for thinning and destruction of cratonic lithosphere   总被引：3，自引：0，他引：3  

Yongfei Zheng  Zheng Xu  Zifu Zhao  Liqun Dai 《中国科学:地球科学(英文版)》2018,61(4):353-385

The North China Craton (NCC) has been thinned from >200 km to <100 km in its eastern part. The ancient subcontinental lithospheric mantle (SCLM) has been replaced by the juvenile SCLM in the Meoszoic. During this period, the NCC was destructed as indicated by extensive magmatism in the Early Cretaceous. While there is a consensus on the thinning and destruction of cratonic lithosphere in North China, it has been hotly debated about the mechanism of cartonic destruction. This study attempts to provide a resolution to current debates in the view of Mesozoic mafic magmatism in North China. We made a compilation of geochemical data available for Mesozoic mafic igneous rocks in the NCC. The results indicate that these mafic igneous rocks can be categorized into two series, manifesting a dramatic change in the nature of mantle sources at ~121 Ma. Mafic igneous rocks emplaced at this age start to show both oceanic island basalts (OIB)-like trace element distribution patterns and depleted to weakly enriched Sr-Nd isotope compositions. In contrast, mafic igneous rocks emplaced before and after this age exhibit both island arc basalts (IAB)-like trace element distribution patterns and enriched Sr-Nd isotope compositions. This difference indicates a geochemical mutation in the SCLM of North China at ~121 Ma. Although mafic magmatism also took place in the Late Triassic, it was related to exhumation of the deeply subducted South China continental crust because the subduction of Paleo-Pacific slab was not operated at that time. Paleo-Pacific slab started to subduct beneath the eastern margin of Eruasian continent since the Jurrasic. The subducting slab and its overlying SCLM wedge were coupled in the Jurassic, and slab dehydration resulted in hydration and weakening of the cratonic mantle. The mantle sources of ancient IAB-like mafic igneous rocks are a kind of ultramafic metasomatites that were generated by reaction of the cratonic mantle wedge peridotite not only with aqueous solutions derived from dehydration of the subducting Paleo-Pacific oceanic crust in the Jurassic but also with hydrous melts derived from partial melting of the subducting South China continental crust in the Triassic. On the other hand, the mantle sources of juvenile OIB-like mafic igneous rocks are also a kind of ultramafic metasomatites that were generated by reaction of the asthenospheric mantle underneath the North China lithosphere with hydrous felsic melts derived from partial melting of the subducting Paleo-Pacific oceanic crust. The subducting Paleo-Pacific slab became rollback at ~144 Ma. Afterwards the SCLM base was heated by laterally filled asthenospheric mantle, leading to thinning of the hydrated and weakened cratonic mantle. There was extensive bimodal magmatism at 130 to 120 Ma, marking intensive destruction of the cratonic lithosphere. Not only the ultramafic metasomatites in the lower part of the cratonic mantle wedge underwent partial melting to produce mafic igneous rocks showing negative ε_Nd(t) values, depletion in Nb and Ta but enrichment in Pb, but also the lower continent crust overlying the cratonic mantle wedge was heated for extensive felsic magmatism. At the same time, the rollback slab surface was heated by the laterally filled asthenospheric mantle, resulting in partial melting of the previously dehydrated rocks beyond rutile stability on the slab surface. This produce still hydrous felsic melts, which metasomatized the overlying asthenospheric mantle peridotite to generate the ultramafic metasomatites that show positive ε_Nd(t) values, no depletion or even enrichment in Nb and Ta but depletion in Pb. Partial melting of such metasomatites started at ~121 Ma, giving rise to the mafic igneous rocks with juvenile OIB-like geochemical signatures. In this context, the age of ~121 Ma may terminate replacement of the ancient SCLM by the juvenile SCLM in North China. Paleo-Pacific slab was not subducted to the mantle transition zone in the Mesozoic as revealed by modern seismic tomography, and it was subducted at a low angle since the Jurassic, like the subduction of Nazca Plate beneath American continent. This flat subduction would not only chemically metasomatize the cratonic mantle but also physically erode the cratonic mantle. Therefore, the interaction between Paleo-Pacific slab and the cratonic mantle is the first-order geodynamic mechanism for the thinning and destruction of cratonic lithosphere in North China.  相似文献   

Water Temperature Dynamics in a Complex of Reservoirs and Its Effect on the Temperature Patterns of a Mountain River     

Łukasz Wiejaczka  Małgorzata Kijowska-Strugała  Paweł Pierwoła  Mariusz Nowak 《Water Resources》2018,45(6):861-872

The article presents the spatial and temporal dynamics of water temperature in two reservoirs on the upper course of the Dunajec River in the Polish Carpathians. It aims at presenting how spatial patterns and time evolution of water temperature in the reservoirs affect the water temperature in the river. The analysis is based on the results of water temperature measurements in hydrometric verticals in two reservoirs as well as in the river upstream and downstream of the reservoirs. The measurements were carried out in 2012 and 2013, in hydrometeorological conditions typical for each season of the year. Based on the measurements, it has been demonstrated that the complex of reservoirs affects the water temperature in the river over the year and the existence of the smaller lower reservoir may attenuate the cooling or heating effect of the main reservoir on the river.  相似文献   

An interacting new holographic dark energy in the framework of fractal cosmology     

Ehsan Sadri  Martiros Khurshudyan 《Astrophysics and Space Science》2018,363(11):230

In this paper, we study an interacting holographic dark energy model in the framework of fractal cosmology. The features of fractal cosmology could pass ultraviolet divergencies and also make a better understanding of the universe in different dimensions. We discuss a fractal FRW universe filled with the dark energy and cold dark matter interacting with each other. It is observed that the Hubble parameter embraces the recent observational range while the deceleration parameter demonstrates an accelerating universe and a behavior similar to \(\Lambda \mbox{CDM}\). Plotting the equation of state shows that it lies in phantom region for interaction mode. We use \(\mathit{Om}\)-diagnostic tool and it shows a phantom behavior of dark energy which is a condition of avoiding the formation of black holes. Finally we execute the StateFinder diagnostic pair and all the trajectories for interacting and non-interacting state of the model meet the fixed point \(\Lambda \mbox{CDM}\) at the start of the evolution. A behavior similar to Chaplygin gas also can be observed in statefinder plane. We find that new holographic dark energy model (NHDE) in fractal cosmology expressed the consistent behavior with recent observational data and can be considered as a model to avoid the formation of black holes in comparison with the main model of NHDE in the simple FRW universe. It has also been observed that for the interaction term varying with matter density, the model generates asymptotic de-Sitter solution. However, if the interaction term varies with energy density, then the model shows Big-Rip singularity. Using our modified CAMB code, we observed that the interacting model suppresses the CMB spectrum at low multipoles \(l<50\) and enhances the acoustic peaks. Based on the observational data sets used in this paper and using Metropolis-Hastings method of MCMC numerical calculation, it seems that the best value with \(1\sigma \) and \(2\sigma \) confidence interval are \(\Omega _{m0}=0.278^{+0.008~+0.010} _{-0.007~-0.009}\), \(H_{0}=69.9^{+0.95~+1.57}_{-0.95~-1.57}\), \(r_{c}=0.08^{+0.02~+0.027}_{-0.002~-0.0027}\), \(\beta =0.496^{+0.005~+0.009} _{-0.005~-0.009}\), \(c= 0.691^{+0.024~+0.039}_{-0.025~-0.037}\) and \(b^{2}=0.035\) according to which we find that the proposed model in the presence of interaction is compatible with the recent observational data.  相似文献