Light attenuation – a more effective basis for the management of fine suspended sediment than mass concentration?

2014 ◽  
Vol 69 (9) ◽  
pp. 1867-1874 ◽  
Author(s):  
Robert J. Davies-Colley ◽  
Deborah J. Ballantine ◽  
Sandy H. Elliott ◽  
Andrew Swales ◽  
Andrew O. Hughes ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Mass Concentration ◽  
Light Attenuation ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Optical Measurements ◽  
Suspended Particulate ◽  
Sediment Mass ◽  
Fine Suspended Sediment ◽  
Mass Concentrations

Fine sediment continues to be a major diffuse pollution concern with its multiple effects on aquatic ecosystems. Mass concentrations (and loads) of fine sediment are usually measured and modelled, apparently with the assumption that environmental effects of sediment are predictable from mass concentrations. However, some severe impacts of fine sediment may not correlate well with mass concentration, notably those related to light attenuation by suspended particles. Light attenuation per unit mass concentration of suspended particulate matter in waters varies widely with particle size, shape and composition. Data for suspended sediment concentration, turbidity and visual clarity (which is inversely proportional to light beam attenuation) from 77 diverse New Zealand rivers provide valuable insights into the mutual relationships of these quantities. Our analysis of these relationships, both across multiple rivers and within individual rivers, supports the proposition that light attenuation by fine sediment is a more generally meaningful basis for environmental management than sediment mass. Furthermore, optical measurements are considerably more practical, being much cheaper (by about four-fold) to measure than mass concentrations, and amenable to continuous measurement. Mass concentration can be estimated with sufficient precision for many purposes from optical surrogates locally calibrated for particular rivers.

scholarly journals Mutual relationships of suspended sediment, turbidity and visual clarity in New Zealand rivers

2015 ◽  
Vol 367 ◽  
pp. 265-271 ◽  
Author(s):  
D. J. Ballantine ◽  
A. O. Hughes ◽  
R. J. Davies-Colley
Keyword(s):  
Water Quality ◽  
Suspended Sediment ◽  
Aquatic Ecosystems ◽  
Water Quality Monitoring ◽  
Suspended Particulate ◽  
Sediment Mass ◽  
Data Scatter ◽  
Significant Interest ◽  
Sufficient Precision ◽  
Mass Concentrations

Abstract. Many river water quality monitoring programmes do not measure suspended particulate matter (SPM) mass concentrations despite significant interest in its multiple effects on aquatic ecosystems. Regular monthly sampling usually intercepts rivers in baseflow when suspended sediment mass concentrations and fluxes are relatively low and not of particular interest. New Zealand’s National Rivers Water Quality Network (NRWQN) is probably typical in not measuring SPM mass, although visual clarity and nephelometric turbidity are routinely measured. In order to better characterize SPM in NZ rivers, total suspended sediment (TSS) was temporarily added to the NRWQN. Turbidity, visual clarity and TSS are mutually inter-related over all 77 sites, although with considerable data scatter. However, within individual rivers turbidity and visual clarity are typically fairly closely related to TSS and provide fair to excellent surrogates. Therefore, TSS need not be measured routinely because it can be estimated with sufficient precision for many purposes from visibility or turbidity.

scholarly journals Fine Sediment Modeling During Storm-Based Events in the River Bandon, Ireland

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1523 ◽  
Author(s):  
Juan T. García ◽  
Joseph R. Harrington
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Storm Event ◽  
Storm Events ◽  
Event Scale ◽  
Model Based ◽  
Sediment Volume ◽  
Bed Erosion

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

River loggers - a new tool to monitor riverine suspended particle fluxes

2001 ◽  
Vol 43 (9) ◽  
pp. 115-120 ◽  
Author(s):  
A. W. Mitchell ◽  
M. J. Furnas
Keyword(s):  
Suspended Sediment ◽  
Suspended Particle ◽  
Sediment Concentration ◽  
Wet Season ◽  
Overlying Water ◽  
Optical Surfaces ◽  
Sufficient Power ◽  
Suspended Sediment Concentrations ◽  
Fine Suspended Sediment

The Australian Institute of Marine Science (AIMS) has developed an in situ digital turbidity logger (AIMS River Logger) to record time series of fine suspended sediment concentrations in North Queensland rivers. The loggers use dual LED transmissometers (15 and 85 mm pathlength) to measure in situ turbidity associated with the range of suspended sediment concentrations (0-5 g L-1) encountered in regional rivers. A system of wiper brushes clean the optical surfaces prior to instrument readings. Overlying water depth and temperature are concurrently recorded. Internal batteries provide sufficient power for unattended deployments of 6+ months with readings taken at 30 minute intervals. Records of suspended sediment concentrations in the lower Tully River over three wet seasons (1996, 1997, 2000) are shown in relation to concurrent river discharge. Peaks in suspended sediment concentration coincide with discharge events. During each event, peak sediment concentrations typically occur during the rising stage of the hydrograph, then decline rapidly prior to significant falls in water level. Derived suspended loads during discharge events are generally proportional to the size of the event, though higher responses are recorded during the initial flood event of each wet season.

Effect of suspended sediment on fertilization success in the scleractinian coral Pectinia lactuca

2012 ◽  
Vol 92 (4) ◽  
pp. 741-745 ◽  
Author(s):  
Paul L.A. Erftemeijer ◽  
Mary Hagedorn ◽  
Michael Laterveer ◽  
Jamie Craggs ◽  
James R. Guest
Keyword(s):  
Suspended Sediment ◽  
Scleractinian Coral ◽  
Coral Species ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Fertilization Success ◽  
Coral Recruitment ◽  
Short Term ◽  
Coral Spawning ◽  
Fine Suspended Sediment

The effect of increased levels of suspended sediment on fertilization success in the scleractinian coral Pectinia lactuca was investigated in a laboratory experiment following a mass coral spawning event on reefs off Singapore. Egg–sperm bundles were collected from tank-spawned coral colonies collected from the field several days prior to the anticipated mass spawning. Eggs and sperm from each colony were separated and distributed systematically across replicated treatments (N = 9) with three concentrations of fine suspended sediment. Spawning and embryo development in Pectinia lactuca followed a pattern similar to other scleractinian coral species. There was a significant effect of increased suspended sediment concentration on fertilization success (P < 0.05). Both high- (169 mg l−1) and medium- (43 mg l−1) suspended sediment treatments decreased fertilization success compared to controls. These results imply that increased turbidity levels (whether chronic, such as in the waters around Singapore, or short-term, caused by a dredging operation)—when coinciding with the coral spawning season—may affect the reproductive success of corals and compromise coral recruitment and recovery of degraded reefs.

Determination of Settling Velocity of Suspended Sediment in Estuary

2014 ◽  
Vol 670-671 ◽  
pp. 805-808 ◽  
Author(s):  
Hui Ming Huang ◽  
Da Ke Chen ◽  
Wei Na Zhang ◽  
Cheng Chen
Keyword(s):  
Suspended Sediment ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Cohesive Sediments ◽  
The Changjiang River ◽  
Sediment Particle Size ◽  
Logarithmic Distribution ◽  
Sediment Data

The settling velocity of sediment is a hot issue and a basic problem in study of sediment transport and estuarine engineering. According to field hydrodynamics and sediment data around the South Passage of the Changjiang River in China, this paper detected the characteristics of sediment particle size and vertical distribution pattern of suspended sediment concentration, and further estimated the settling velocity of suspended sediment in three methods. The results show that the sediments including suspended and bed load can be categorized into cohesive sediments and the sediment concentration profile agree well with logarithmic distribution. Furthermore, by comparison, it is found that the Rouse formula is more reasonable for estimating the settling velocity of fine sediment, but the Zhang Ruijin and Stokes formula obviously underestimate the values of settling velocity, caused by do not taking into account the flocculation of fine sediment in estuary.

scholarly journals Do legacy effects of deposited fine sediment influence the ecological response of drifting invertebrates to a fine sediment pulse?

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
Victoria S. Milner ◽  
Ian P. Maddock ◽  
Iwan Jones ◽  
George C. Bunting
Keyword(s):  
Suspended Sediment ◽  
Community Dynamics ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Control Treatment ◽  
Legacy Effects ◽  
Taxonomic Richness ◽  
Legacy Effect ◽  
Stream Mesocosms ◽  
Habitat Template

AbstractThe deposition of excess fine sediment and clogging of benthic substrates is recognised as a global threat to ecosystem functioning and community dynamics. Legacy effects of previous sedimentation create a habitat template on which subsequent ecological responses occur, and therefore, may have a long-lasting influence on community structure. Our experimental study examined the effects of streambed colmation (representing a legacy effect of fine sediment deposition) and a suspended fine sediment pulse on macroinvertebrate drift and community dynamics. We used 12 outdoor stream mesocosms that were split into two sections of 6.2 m in length (24 mesocosm sections in total). Each mesocosm section contained a coarse bed substrate with clear bed interstices or a fine bed substrate representing a colmated streambed. After 69 days, a fine sediment pulse with three differing fine sediment treatments was applied to the stream mesocosms. Added fine sediment influenced macroinvertebrate movements by lowering benthic density and taxonomic richness and increasing drift density, taxonomic richness, and altering drift assemblages. Our study found the highest dose of sediment addition (an estimated suspended sediment concentration of 1112 mg l−1) caused significant differences in benthic and drift community metrics and drift assemblages compared with the control treatment (30 l of water, no added sediment). Our results indicate a rapid response in drifting macroinvertebrates after stressor application, where ecological impairment varies with the concentration of suspended sediment. Contrary to expectations, bed substrate characteristics had no effect on macroinvertebrate behavioural responses to the fine sediment pulse.

Tide-induced fine sediment resuspension in the well-mixed Hangzhou Bay, East China Sea, China

2011 ◽  
Vol 102 (1) ◽  
pp. 25-34 ◽  
Author(s):  
John Z. Shi
Keyword(s):  
Suspended Sediment ◽  
East China Sea ◽  
Suspended Sediment Concentration ◽  
Sediment Resuspension ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
East China ◽  
Hangzhou Bay ◽  
China Sea ◽  
Suspended Sediment Concentrations

ABSTRACTHangzhou Bay is a typical funnel-shaped high turbid estuary along a mesotidal coast of the East China Sea. In this paper, field studies are undertaken in an attempt to better understand tide-induced fine sediment transport processes in the Bay. Field observations were made mainly of current velocities (speeds and directions) and suspended sediment concentrations at six different relative depths and two stations in September 1992. Results show that (1) high near-bed suspended sediment concentrations varied from 1·81 to 4·00 kg m−3 during the spring tide and from 1·04 to 8·00 kg m−3 during the neap tide; (2) tide-induced near-bed fine sediment resuspension processes are indicated by several periodic suspended sediment concentration peaks; and (3) a hysteresis effect, or suspension-lag, occurs in suspended sediment concentration and resuspension events. Tide-induced fine sediment processes are mainly responsible for very high concentration suspensions of fine sediments in Hangzhou Bay. The occurrence of the suspension-lag phenomenon is likely to be common in other similar muddy tidal environments.

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