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1.
The porosity of a bimodal sediment mixture is affected by the filling of fine particles in the voids of coarse particles when the particle size range is wide. The classical ideal packing models tend to overestimate the filling, and, thus, underestimate the porosity of the mixture. In this study, an existing random filling model is improved by considering a three-dimensional packing configuration, and a new model is developed by considering how many fine particles are required and how many are available to cover the surface of coarse particles in the sediment mixture. The developed models are validated using measured data and compared with existing models. The new model can reproduce well the variation trend of the mixture porosity as the fraction of fine particles varies. 相似文献
2.
Experiments were carried out on granular flows generated by instantaneous release of gas-fluidised, bidisperse mixtures and propagating into a horizontal channel. The mixture consists of fine (< 100 μm) and coarse (> 100 μm) particles of same density, with corresponding grain size ratios of ∼ 2 to 9. Initial fluidisation of the mixture destroys the interparticle frictional contacts, and the flow behaviour then depends on the initial bed packing and on the timescale required to re-establish strong frictional contacts. At a fines mass fraction (α) below that of optimal packing (∼ 40%), the initial mixtures consist of a continuous network of coarse particles with fines in interstitial voids. Strong frictional contacts between the coarse particles are probably rapidly re-established and the flows steadily decelerate. Some internal friction reduction appears to occur as α and the grain size ratio increases, possibly due to particle rolling and the lower roughness of internal shear surfaces. Segregation only occurs at large grain size ratio due to dynamical sieving with fines concentrated at the flow base. In contrast, at α above that for optimal packing, the initial mixtures consist of coarse particles embedded in a matrix of fines. Flow velocities and run-outs are similar to that of the monodisperse fine end-member, thus showing that the coarse particles are transported passively within the matrix whatever their amount and grain size are. These flows propagate at constant height and velocity as inviscid fluid gravity currents, thus suggesting negligible interparticle friction. We have determined a Froude number of 2.61 ± 0.08 consistent with the dam-break model for fluid flows, and with no significant variation as a function of α, the grain size ratio, and the initial bed expansion. Very little segregation occurs, which suggests low intensity particle interactions during flow propagation and that active fluidisation is not taking place. Strong frictional contacts are only re-established in the final stages of emplacement and stop the flow motion. We infer that fines-rich (i.e. matrix-supported) pyroclastic flows propagate as inviscid fluid gravity currents for most of their emplacement, and this is consistent with some field data. 相似文献
3.
We hypothesize that anisotropy in soil properties arises from pore-scale heterogeneity caused by the alignment of aspherical soil particles. We developed a method to predict the permeability tensor from particle shape and packing structure. Digital geometry maps were created for the pore space in regular cubic and random packs of particles with various aspect ratios using a numerical packing algorithm. The lattice-Boltzmann method was used to simulate saturated flow through these packs, and the effect of particle shape and degree of alignment on the permeability tensor was characterized. Results show that the degree of anisotropy in permeability depends not only upon particle shape and alignment, but also on the three-dimensional structure of the pack. In random packs, more oblate particles and higher degrees of particle alignment lead to reduced permeability perpendicular to the direction of particle alignment compared to the direction parallel to particle alignment. 相似文献
4.
S. Santiago R. L. Thomas L. McCarthy J. L. Loizeau G. Larbaigt C. Corvi D. Rossel J. Tarradellas J. P. Vernet 《水文研究》1992,6(2):227-240
Ten large volume water samples were taken from the Rhône River (Switzerland-France) in November, 1989 for recovery of total suspended sediment by continuous flow centrifugation. the samples were freeze-dried and analysed for particle size, organic carbon, total nitrogen, and carbonate. for comparative purposes, four bed sediments collected in July, 1989 are also described. the Rhône can be subdivided into three sections on the basis of the origins of the water. the first section is the Upper Rhône River draining into Lake Geneva. Waters are derived from glaciers, with low temperature and conductivity and high turbidity. Suspended sediment is coarse, has a bimodal distribution, and is low in both organic matter and carbonate. the second reach is from Lake Geneva to the confluence with the Saône at Lyon and has warmer water with higher conductivity and very low turbidity. Suspended sediment is higher in organic matter, with high carbonate originating from the lake. the final section is from Lyon to Arles, with warmer water and higher conductivity and turbidity due to modification by the Saône. Sediment is rich in organic matter, which May, account for an observed decline in oxygen in the river waters downstream from Lyon. Carbonate in these sediments also decreases due to increased turbidity from the Saône. Suspended sediments other than from the Upper Rhône show a remarkable consistency in grain size, predominantly in the fine silts (mode 9-11 μm). This consistency indicates a high degree of suitability for geochemical analysis. Bed sediments were bimodal throughout, with a dominant coarse population in two out of the four samples. Grain size statistical parameters could be easily explained by application of the theory of mixing of two major populations in the sand size (bed traction load) and the fine silt/clay size (suspended sediment load). 相似文献
5.
Hyunwook Choo Qian Zhao Susan E. Burns Terry W. Sturm Seung Ho Hong 《地球表面变化过程与地形》2020,45(7):1499-1509
Sedimentation – including erosion, transport, and deposition of coarse-grained particles – is a primary and growing environmental, engineering, and agricultural issue around the world. Soil erosion occurs when the hydrodynamic force induced by flowing water exceeds the geotechnical resistance of soils, as measured by critical shear stress for initiation of soil-particle motion. Even though various quantitative methods have been suggested with respect to different types of soil, the most widely accepted formula to estimate critical shear stress for coarse-grained soil is a direct function of the median grain size of the soil particles; however, the erosion resistance of soils also varies with other geotechnical properties, such as packing density, particle shape, and uniformity coefficient. Thus, in this study, a combined rolling–lift model for particle detachment was derived based on theoretical analysis. A series of experimental flume tests were conducted with specimens prepared with standard soil types, as well as laboratory-prepared mixtures of coarse-grained soil to validate the theoretical model and determine the effect of other geotechnical properties on the erosion characteristics of coarse grains, coupled with the effect of median particle size. The results indicated that the median grain size is the primary variable determining the resistance of coarse grains, but the critical shear stress also varies with the packing density of the soil matrix. In addition, angular particles show more erosion resistance than rounded particles, and the erosion potential of a soil decreased when the grain is well graded (higher value of uniformity coefficient). Additionally, regression analysis was performed to quantify the effect of each parameter on the critical shear stress of coarse grains. © 2020 John Wiley & Sons, Ltd. 相似文献
6.
A generalized probabilistic model is developed in this study to predict sediment entrainment under the incipient motion, rolling, and pickup modes. A novelty of the proposed model is that it incorporates in its formulation the probability density function of the bed shear stress, instead of the near-bed velocity fluctuations, to account for the effects of both flow turbulence and bed surface irregularity on sediment entrainment. The proposed model incorporates in its formulation the collective effects of three para-meters describing bed surface irregularity, namely the relative roughness, the volumetric fraction and relative position of sediment particles within the active layer. Another key feature of the model is that it provides a criterion for estimating the lift and drag coefficients jointly based on the recognition that lift and drag forces acting on sediment particles are interdependent and vary with particle protrusion and packing density. The model was validated using laboratory data of both fine and coarse sediment and was compared with previously published models. The study results show that all the examined models perform adequately for the fine sediment data, where the sediment particles have more uniform gra-dation and relative roughness is not a factor. The proposed model was particularly suited for the coarse sediment data, where the increased bed irregularity was captured by the new parameters introduced in the model formulation. As a result, the proposed model yielded smaller prediction errors and physically acceptable values for the lift coefficient compared to the other models in case of the coarse sediment data. 相似文献
7.
During the period 2019–2020, size-segregated aerosol samples containing elemental and organic carbon (EC and OC) were investigated. These samples were collected weekly using an eight-stage cascade impactor from an urban site located at Aksaray University, Aksaray. The quantification of EC and OC was carried out through a thermal-optical transmission device. The results revealed consistent size distribution attributes of EC and OC between winter and summer. Although EC accounted for an insignificant percentage (4.4%) of particulate matter (PM) in the PM9.0–10.0 fraction during winter, a more substantial portion of OC in the same fraction (13.4%) comprised EC. Seasonal variations were distinct for EC but not significant for OC. Strong correlations between OC and EC were observed in coarse particle fractions, indicating a common source, with weaker correlations in fine particles. The highest OC/EC ratio was in the PM0.43–0.65 fraction, followed by PM2.1–3.3. The ratio of OC to EC in fine PM exceeded the threshold of 15 consistently. The observation indicates that as particle size increases, there is a noticeable decline in the OC to EC ratios. Secondary organic aerosols (SOA) accounted for 60.8% (winter) and 89.8% (summer) of OC values, emphasizing the substantial impact of SOA on Aksaray's atmosphere. Both seasons exhibited a multimodal distribution of ambient OC. In winter, the EC distribution was dominated by fine particles, with a bimodal pattern (PM1.1–2.1 and PM0.43–0.65 peaks). Common pollutant sources, including traffic emissions, road dust, biogenic emissions, and coal combustion, were identified for both seasons in coarse and fine particle fractions. These findings underscore the importance of emission control strategies targeting fine PM in Aksaray. 相似文献
8.
《国际泥沙研究》2019,34(6):550-563
The effects of turbulence on water-sediment mixtures is a critical issue in studying sediment-laden flows. The sediment concentrations and particle inertia play a significant role in the effects of turbulence on mixtures. A two-phase mixture turbulence model was applied to investigate the turbulence mechanisms affecting sediment-laden flows. The two-phase mixture turbulence model takes into account the complicated mechanisms arising from interphase transfer of turbulent kinetic energy, particle collisions, and stratification. The turbulence in sediment-laden flows is the result of the interaction of four factors, i.e. the production, dissipation, diffusion, and inter-phase transfer of turbulent kinetic energy of mixtures. The turbulence production and dissipation are two dominant processes which balance the turbulent kinetic energy of mixtures. The turbulence production represents turbulence intensity, while the inter-phase transfer of turbulent kinetic energy denotes the effect of particles on the turbulence of sediment-laden flows. Although, the magnitude of the inter-phase interaction term is much less than that of the turbulence production and dissipation terms, due to an approximate local balance between production and dissipation of the turbulent kinetic energy, even the small order of the inter-phase interaction has a significant impact on the turbulent balance of sediment-laden flows. The presence of particles plays a duel role in the turbulence dissipation of mixtures: both promotion and suppression. An important parameter used to determine the turbulent viscosity of mixtures, which is constant in clear water, is the function of the sediment concentration and particle inertia in sediment-laden flows. 相似文献
9.
The settling potential of fine sediment is known to be influenced by particle size, shape, density and porosity, and is commonly predicted using Stokes's law, despite its known limitations for modelling the behaviour of natural particles. In order to develop an improved understanding of the potential for fine sediment to settle out of suspension or undergo transport by hydraulic processes, it is important to examine the role of particle structure in detail. In this study, stepwise regression was used to identify which structural properties of particles exert an important control on fine sediment behaviour in river systems. The presence of composite particles and their associated particle size, porosity and fractal dimension were shown to be the most important controls on settling potential. Composite particles that form in the aquatic environment (flocs) were shown to have significantly different form and behaviour from composite particles of terrestrial origin (aggregates). Importantly, it was demonstrated that particle structure and behaviour exhibited consistencies between contrasting river catchments in different locations. An understanding of the mechanisms responsible for the formation of composite particles is viewed as providing a valuable input to efforts to model the mobilisation, transport and fate of fine sediment. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
10.
颗粒随机堆积问题是物理和工程领域的热门问题。椭球颗粒随机堆积体系作为球形体系的拓展,增加了旋转自由度,从而表现出更复杂的性质,由于椭球颗粒比球形颗粒更类似于自然界中普遍存在的非规则颗粒,因此其研究具有重要的实用价值。研究三维颗粒堆积结构问题一般需要CT成像技术,本文介绍了如何利用医用CT对三维椭球随机堆积体系进行成像研究的技术细节,包括如何通过图像处理的方法获取椭球颗粒的空间位置、取向和体积,如何利用接触数标度函数拟合的方法得到近邻颗粒间的接触信息等。本文的研究内容和方法为利用各种X射线CT成像方法研究三维颗粒体系提供了技术参考。 相似文献
11.
One of the mechanisms of sudden particle release from grain surfaces in natural porous media is a decrease in salt concentration of the permeating fluid to below the critical salt concentration. Particle release can cause a change in hydraulic conductivity of the matrix, either by washing out the fines and thus increasing the pore sizes or by the plugging of pore constrictions. The phenomenon of permeability changes as a result of particle detachment was investigated in a series of column experiments. Coarse and fine sediments from the Hanford Formation in southeast Washington were tested. Columns were subject to a pulse of highly saline solution (NaNO3) followed by a fresh water shock causing particle release. Outflow rates and changes in hydraulic head as well as electric conductivity and pH were monitored over time. No permeability decrease occurred within the coarse matrix alone. However, when a thin layer of fine sediment was embedded within the coarse material (mimicking field conditions at the Hanford site), permeability irreversibly decreased to 10% to 20% of the initial value. Evidence suggests that most of this permeability decrease was a result of particles detached within the fine layer and its subsequent clogging. An additional observation was a sudden increase in pH in the outflow solution, generated in situ during the fresh water shock. Because layered systems are common in natural settings, our results suggest that alteration between sodium solution and fresh water can lead to particle release and subsequently reduce the overall permeability of the matrix. 相似文献
12.
The history of natural fire and its relationship to climate during the last three glacial-interglacial cycles in the Southern coast areas of China and the northern continental shelf of the South China Sea (SCS) are discussed based on the statistic study of charcoal particles and associated pollen data from ODP 1144 Site (20° 3′N, 117° 25’E, 2037 m in water depth). According to the results of the charcoal and pollen study, the sediments from the upper 225 m are divided into 8 zones (C1–C8), which might be correlated with the Marine Isotope Stage 1–8 (MIS1-8) respectively. Our study indicates that during the last glacial period (MIS2, 4), the influx of charcoal particle was much higher than that from the interglacial period, suggesting strong occurrence of natural fire and dry climate. During MIS 6 and MIS 8 (C6, C8), although the influx of fine charcoal particles was quite high, the influx of the coarse and medium charcoal particle were much low, which might be due to the smaller source area of fire probably resulting from the limited exposure of the continental shelf before MIS5. During the interglacial period (MIS1, 5, 7), the influxes of charcoal particles were much lower, implying dropping of intensity of the natural fire and then a humid climate. Another reason is that the continental shelf was submerged into the sea during the interglacial periods, and the source areas of fire were reduced then. Although the influx of the fine charcoal particles was much lower during MIS3, the influx of the coarse and medium charcoal particles were almost equal to those of MIS4 (C4), which suggests that the intensity of the natural fire remained quite high and the climate was considerably dry during that period. 相似文献
13.
The history of natural fire and its relationship to climate during the last three gla cial-interglacial cycles in the Southern coast areas of China and the northern continental shelf of the South China Sea (SCS) are discussed based on the statistic study of charcoal particles and associated pollen data from ODP 1144 Site (20° 3′N, 117° 25′E, 2037 m in water depth). Accord ing to the results of the charcoal and pollen study, the sediments from the upper 225 m are divided into 8 zones (C1-8), which might be correlated with the Marine Isotope Stage 1-8 (MIS1-8)respectively. Our study indicates that during the last glacial period (MIS2, 4), the influx of charcoal particle was much higher than that from the interglacial period, suggesting strong occurrence of natural fire and dry climate. During MIS 6 and MIS 8 (C6, C8), although the influx of fine charcoal particles was quite high, the influx of the coarse and medium charcoal particle were much low,which might be due to the smaller source area of fire probably resulting from the limited exposure of the continental shelf before MIS5. During the interglacial period (MIS1, 5, 7), the influxes of charcoal particles were much lower, implying dropping of intensity of the natural fire and then a humid climate. Another reason is that the continental shelf was submerged into the sea during the interglacial periods, and the source areas of fire were reduced then. Although the influx of the fine charcoal particles was much lower during MIS3, the influx of the coarse and medium charcoal par ticles were almost equal to those of MIS4 (C4), which suggests that the intensity of the natural fire remained quite high and the climate was considerably dry during that period. 相似文献
14.
A series of flume experiments were done to investigate the effect of grain composition on the critical gradient and discharge of debris flows initiated in seasonal gullies. The results indicated that the critical gradient and discharge for debris flow initiation decrease initially, and then increase as the mass content of fine particles (<2 mm) increases. As the mass content of fine particles increases, the angle of repose, permeability of widely graded gravel soils, and the incipient motion conditions of the coarse grains in non-uniform sediments decrease at first, and then increase. The mass content of fine particles of all inflection points is the same. The theoretical model based on the combination of hydrodynamic force and shear stress is more applicable to the prediction of the critical gradient for debris flow initiation. The critical discharge model considering the effect of non-homogeneity of the soil and the size of coarse and fine grains provides a more accurate prediction of debris flow initiation than other models based on the mean diameter. 相似文献
15.
Zhao Wei Youze Xu Yanyan Zhao Yuanyuan Zhao Leilei Bai Helong Jiang Changhui Wang 《国际泥沙研究》2021,36(4):542-554
Sediment resuspension is an important way for shallow lake internal pollution to interact with the overlying water column,and the pollution risks are reasonably related to the retention of resuspended sediment particles in overlying water.In the current study,the settling of resuspended sediment particles was comprehensively investigated under different disturbances using five urban lake sediments.The results show that the particle size distributions of resuspended sediment from different lakes exhibited similar variations during settling with disturbance,although varied settling times were observed under static conditions.During settling with and without disturbance,sediment particle sizes were mainly within 8-63μm at the initial stage,and were<8μm in the later stages of settling.Based on these settling characteristics,the sediment particle size was divided into sand(>63μm),silt(8-63μm),and very fine silt and clay(<8μm)fractions.Kinetic analysis suggested that sediment settling for different particle sizes could be well described by the first-and second-order kinetic equations,especially when settling was disturbed(r2=0.727-0.999).The retention of resuspended sediment could be enhanced as particle sizes decreased and disturbance intensities increased.Furthermore,a water elutriation method was successfully optimized,with separation efficiencies of 56.1%-83%,to separate sediment particles into the defined three particle size fractions.The chemical compositions of sediment were found to change with different particle sizes.Typically,calcium tended to form large-size sediment,while the total contents of aluminum,iron,magnesium,and manganese showed significantly negative correlations with sediment particle sizes(p<0.01)and tended to distribute in small-size particles(e.g.,<8μm).Overall,the sediment particle size related settling dynamics and physicochemical properties suggested the necessity on determining the pollution of resuspended sediment at different particle sizes for restoration of shallow lakes. 相似文献
16.
Total organic carbon(TOC) and grain size distribution(sand,silt,and clay) in the ephemeral Mahi River(western India) sediments were measured to look at their effectiveness in understanding the late Quaternary monsoon conditions.Four sites spread across the alluvial zone and three sites from the estuarine zone were sampled.TOC concentration in the sediments of the alluvial and estuarine zone sites ranged between 0.04 and 0.39%and 0.04 and 0.23%,respectively.It was observed that grain size differed significantly at the alluvial zone sites,whereas an uniform trend was found in the estuarine zone sites.The study indicated that low concentration of TOC and coarse size fractions(sand) in sediments were well correlated with available records of arid/weaker palaeomonsoon periods,whereas higher concentration of TOC and fine grain size fractions(silt + clay) in sediments were well correlated with available records of enhanced palaeomonsoon periods of the ephemeral Mahi River.Uniform concentrations of TOC and fine grain size particles in sediments at the estuarine zone sites are attributed to the backwater in the system,deeper sedimentation,and/or greater decomposition processes.It is concluded that,TOC and grain size distributions in the ephemeraL river sediments are simple and effective parameters to develop an understanding about late Quaternary monsoon conditions in ephemeral rivers. 相似文献
17.
Mauro Mele Silvia Inzoli Mauro Giudici Riccardo Bersezio 《Geophysical Prospecting》2014,62(3):631-645
Electrical conductivity of alluvial sediments depends on litho‐textural properties, fluid saturation and porewater conductivity. Therefore, for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers, it can be useful to characterize the prevailing mechanisms of electrical conduction (electrolytic or shale conduction) according to the litho‐textural properties and to the porewater characteristics. An experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the Po plain (Northern Italy), characterized by different grain‐size distribution, and fully saturated with porewater of variable conductivity. The bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two‐component model, which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample, and with a three‐component model. The latter is based on the two endmember mechanisms, surface and electrolytic conduction, but takes into account also the interaction between dissolved ions in the pores and the fluid‐grain interface. The experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume. 相似文献
18.
Simulated rainfall experiments were performed on bare, undecomposed litter layer and semi-decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m−2, respectively, to evaluate the effect of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi-decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi-decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi-decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion. 相似文献
19.
Senapathi VENKATRAMANAN Thirunavukkarasu RAMKUMAR Irudhayanathan ANITHAMARY Govindaraj RAMESH 《国际泥沙研究》2011,(4):460-470
The distribution of grain size parameters along 11 km stretch of the beach sediments between Karikal and Nagore,reveals that the mean grain size exhibits a marked decreasing trend on either side of the mouth of the Tirumalairajanar River which flow from west to east.The sediments are mainly of medium to coarse grained,moderately sorted,near-symmetrical skewed to fine skewed and leptokurtic to mesokurtic in nature.Interrelationship of various parameters shows bimodal nature of sediments having dominance of medium to coarse sand.The major part of the sediment fall in a coarse to fine grained category(sand and silt).Based on the CM(Coarser one percentile value in micron) pattern,the sediment fall in rolling and suspension field.These factors includes the sediments discharged from the river mixes with offshore sediments and with the sediments eroded from a source rock.The effect of wave sorting, and the northward drifting of sediments by littoral current are understandable.Results indicate that the Tirumalairajanar River is the most important source for modern sediments in the study area.The agitation by waves is an important sorting mechanism in the study area,and the net sediment transport in the study area is northward.The findings are based on the grain sizes and also corroborated by shortterm observations of the beach sediment dynamics and transport during the monsoon and summer seasons between Karaikal and Nagore region. 相似文献
20.
Jennifer Drummond Aslan Wright-Stow Paul Franklin John Quinn Aaron Packman 《水文研究》2020,34(21):4128-4138
Wood additions to streams can slow water velocities and provide depositional areas for bacteria and fine particles (e.g., particulate organic carbon and nutrients sorbed to fine sediment), therefore increasing solute and particle residence times. Thus, wood additions are thought to create biogeochemical hotspots in streams. Added wood is expected to enhance in-stream heterogeneity, result in more complex flow paths, increase natural retention of fine particles and alter the geomorphic characteristics of the stream reach. Our aim was to directly measure the impact of wood additions on fine particle transport and retention processes. We conducted conservative solute and fluorescent fine particle tracer injection studies in a small agricultural stream in the Whatawhata catchment, North Island of New Zealand in two reaches—a control reach and a reach restored 1-year earlier by means of wood additions. Fine particles were quantified in surface water to assess reach-scale (channel thalweg) and habitat-scale (near wood) transport and retention. Following the injection, habitat-scale measurements were taken in biofilms on cobbles and by stirring streambed sediment to measure fine particles available for resuspension. Tracer injection results showed that fine particle retention was greater in the restored compared to the control reach, with increased habitat-scale particle counts and reach-scale particle retention. Particle deposition was positively correlated with cobble biofilm biomass. We also found that the addition of wood enhanced hydraulic complexity and increased the retention of solute and fine particles near the wood, especially near a channel spanning log. Furthermore, particles were more easily remobilized from the control reach. The mean particle size remobilized after stirring the sediments was ~5 μm, a similar size to both fine particulate organic matter and many microorganisms. These results demonstrate that particles in this size range are dynamic and more likely to remobilize and transport further downstream during bed mobilization events. 相似文献