Sediment Size Classes Research Articles

A New Method for Evaluating Particle Size Distribution and Aggregated Portion of Eroded Sediment

ABSTRACT Amethod has been developed for determining size distributions of undispersed sediment without relying on pipette withdrawals. This method also evaluates portions of aggregates and primary particles in each sediment size class. The approach involves use of size distribution of coarse sediment as determined by wet sieving, size distribution of the dispersed total sediment sample, some special sieve analyses of sediment finer than 63 ixm, and deductive reasoning. The results computed by this method yield a sediment size distribution based on the physical size of the sediment for all size groups rather than a composite of two partial distributions: (a) physical size for the sieved portion and (b) an equivalent size for the aggregates in the pipetted portion. Results from Brooksville clay illustrate the problem with compositing such partial distributions. For the composite method, no sediment was in the 32 to 63 jLtm size group whereas the new method showed that nearly 6% was in this size group. The composite results also indicate 20% more of the sediment sample in sizes smaller than 16 jLtm than should be according to the new method.

Effects of Two Sediment Size-Classes on Survival of Steelhead and Chinook Salmon Eggs

Abstract We compared, in the laboratory, egg survival, and alevin and fry size of steelhead Oncorhyncus mykiss (formerly Salmo gairdneri) and chinook salmon O. tshawytscha after incubations in 16 mixtures of two distinct size-classes of sediment. Fine sediments were less than 0.84 mm in diameter, and coarse sediments were 0.84–4.6 mm in diameter. We incubated recently fertilized and eyed steelhead eggs and chinook salmon eggs in Whitlock–Vibert boxes placed in controlled-flow channels. Egg survival in both sediment types was inversely related to the percentage of sediments within the incubation gravel; the poorest survival occurred in fine sediments. Percentage egg survival was positively related to intragravel water velocities, which ranged from 36 to 1,550 cm/h. No definitive relationship was found between sediment size and concentration, and alevin and fry quality. Overall, our results indicated that different sizes and mixtures of sediment can affect egg survival differently. The results confirmed tha...

Sedimentary characteristics of sabellariid worm reefs ( Phragmatopoma lapidosa Kinberg)

Sedimentary characteristics of worm reefs constructed by the sabellariid polychaete Phragmatopoma lapidosa Kinberg were examined to determine whether sediments of specific size and/or composition were selected for use in tube construction. Sediment size class distributions and CaCO 3 content were determined for samples of worm reef and unconsolidated beach sediment collected from six locations along a 250 km stretch of Florida's south-east shoreline during 1984. Results of the analyses indicated that CaCO 3 sediment particles ranging from 0·25-0·50 cm in diameter were used preferentially for tube construction at all sites regardless of local beach sediment characteristics.

Organic geochemistry of suspended and settling particulate matter in Lake Michigan

Organic matter contained in particulate matter in Lake Michigan waters and sediments has been characterized by CN ratios and by distributions of biomarker fatty acids, alkanols, sterols, and aliphatic hydrocarbons. Differences in organic constituents of particulate matter from various depths and distances from shore indicate a complex interaction of production, transformation, and destruction of the organic matter contained in sinking particles. Near-surface material contains important contributions of landderived organic matter, presumably of eolian input. Midwater particles have predominantly aquatic organic material of algal origin. At the sediment-water interface, selective suspension of the finer fractions of surficial sediments enriches bottom nepheloid layers with these sediment size classes. As a result, near-bottom particulate matter has an aquatic biomarker character. Organic matter associated with sinking particles undergoes substantial degradation during passage to the bottom of Lake Michigan, and aquatic components are selectively destroyed relative to terrigenous components.

Study of factors influencing variation in size characteristics of fluvioglacial sediments

Factor analysis using promax oblique rotation was used in a study of fluvioglacial sediments of Late Weichsilian (Wurm) age. The use of oblique rotation allowed a more realistic interpretation of the factors and understanding of relationships between sedimentsize classes. At the second-order level, two factors are operatable, one producing variations in the coarse-size range, the other in the fine-size range. The factors are uncorrelated and mutally unrelated. At the first-order level are six factors, four representing aspects of the second-order factor of coarse size and two representing the fine size. The factor producing the variation in the coarse size is the most important one. At the lowest level in the hierarchy scale are the individual size variables. Results show that the number of factors required to account for the variation in a sediment-size data set is a function of the scale at which the problem is examined.