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At least 1,171 records · Page 65Linked to original sources
PubMed2002

Developments in a methodology for the design of engineered invert traps in combined sewer systems.

Sediments within sewers can have a significant effect on the operation of the sewer system and on the surrounding natural and urban environment. One possible method for the management of sewer sediments is the use of slotted invert traps. Although invert traps can be used to selectively trap only inorganic bedload material, little is known with regard to the design of these structures. This paper presents results from a laboratory investigation comparing the trapping performance of three slot size configurations of a laboratory-scale invert trap. The paper also presents comparative results from a two-dimensional computational model utilising stochastic particle tracking. This investigation shows that particle tracking consistently over-predicts sediment retention efficiencies observed within the laboratory model.

Engineering↗
PubMed2003

Effects of organic amendments on the toxicity and bioavailability of cadmium and copper in spiked formulated sediments.

We evaluated the partitioning and toxicity of cadmium (Cd) and copper (Cu) spiked into formulated sediments containing two types of organic matter (OM), i.e., cellulose and humus. Amendments of cellulose up to 12.5% total organic carbon (TOC) did not affect partitioning of Cd or Cu between sediment and pore water and did not significantly affect the toxicity of spiked sediments in acute toxicity tests with the amphipod Hyalella azteca. In contrast, amendments of natural humus shifted the partitioning of hoth Cd and Cu toward greater concentrations in sediment and lesser concentrations in pore water and significantly reduced toxic effects of both metals. Thresholds for toxicity, based on measured metal concentrations in whole sediment, were greater for both Cd and Cu in sediments amended with a low level of humus (2.9% TOC) than in sediments without added OM. Amendments with a high level of humus (8.9% TOC) eliminated toxicity at the highest spike concentrations of both metals (sediment concentrations of 12.4 microg Cd/g and 493 microg Cu/g). Concentrations of Cd in pore water associated with acute toxicity were similar between sediments with and without humus amendments, suggesting that toxicity of Cd was reduced primarily by sorption to sediment OM. However, toxic effects of Cu in humus treatments were associated with greater pore-water concentrations than in controls, suggesting that toxicity of Cu was reduced both by sorption and by complexation with soluble ligands. Both sorption and complexation by OM tend to make proposed sediment quality guidelines (SQGs) based on total metal concentrations more protective for high-OM sediments. Our results suggest that the predictive ability of SQGs could be improved by models of metal interactions with natural OM in sediment and pore water.

Amphipoda↗
PubMedDate not supplied

[Indication of Northern Caspian regions by biochemical (enzymatic) indices of water and bottom sediments].

We evaluated ecological status in the region of mixing of river and sea waters in the northern Caspian Sea with high anthropogenic pressure. We studied the regions of Volga River fore-delta, the water areas neighboring ancient hydrological transects, and the sea regions between the transects. The water areas were evaluated by biochemical degradation of organic compounds (proteinase and amylase activities) in water and bottom sediments as well as hydrochemical indices of water (salt composition and contents of dissolved oxygen and biogenic compounds). In conditions of active vegetation of phytoplankton and higher aquatic plants soon after the highest wave of the Volga flood, we studied distribution of hydrolytic enzyme activities involved in the global production/destruction cycle of high molecular weight organic compounds (proteins and polysaccharides). The data obtained with the trypsin-azocasein and alpha-amylase-modified starch tests indicates pollution of water and surface sediments in the lower reaches of Volga and the inflow sea regions.

Environmental Monitoring↗
PubMed2005

[Eco-toxicity diagnosis on sediments of petroleum wastewater irrigation channel].

Sediment samples were collected from several sites in the upper, mid and lower reaches of the petroleum wastewater irrigation channel in eastern Shenyang of China, and the concentrations of their Cu, Zn, Pb, Cd and mineral oil were analyzed. The results showed that the pollutants were accumulated in all of sediment samples, with 408-118,300 mg x kg(-1) mineral oil, 17.83-78.53 mg x kg(-1) Cu, 35.76-155.16 mg x kg(-1) Zn, 8.50-31.03 mg x kg(-1) Pb and 0.1-1.0 mg x kg(-1) Cd. The sediments showed an inhibition or stimulation effect on plant root elongation and a lethal and sub-lethal effect on earthworm. The inhibition rate of root elongation based on germination test was -29.81 to 93.8%. During 14 d exposure, the maximum mortality rate of earworm was 100%, and during 14d and 28d exposure, the inhibition rate of its body weight growth was -36.6%-(-)6.08% and -40.4%-6.1%, respectively. The study indicated that a long-term irrigation with petroleum wastewater resulted in the accumulation of pollutants in channel sediments and enhanced eco-toxicity.

Crops, Agricultural↗
PubMed2005

Tracing the influence of sewage nitrogen in a coastal ecosystem using stable nitrogen isotopes.

This paper reviews the use of stable nitrogen isotopes (delta15N) to delineate the influence of sewage nitrogen (N) in coastal ecosystems, drawing extensively on the case of Himmerfjärden, a Baltic Sea bay that receives 15N-enriched tertiary treated sewage that is discharged mainly as dissolved inorganic N (DIN). Gradients of delta15N in macroalgae (Fucus vesiculosus) and surface sediments traced sewage-derived N to 24 km from the outfall but elevated delta15N values (> 7 per thousand) indicated that the sewage influence was most pronounced within 10 km. Comparison of macroalgal delta15N values before and after enhanced tertiary treatment showed a decrease in the spatial impact of sewage N from about 24 km to 12 km from the outfall and a decrease to more marine delta15N values in more recent growth tissues. Sedimentary delta15N records showed that sewage has had a dominant influence on organic matter production in the bay with dramatic increases in sedimentary delta15N during the years of maximum sewage N loads. In cases where sewage N introduces a distinct isotopic signature into a system and where it has had a dominant influence on organic matter production, delta15N values in biota and sediments can be used to trace the spatial and temporal influence of sewage N in aquatic ecosystems.

Ecosystem↗
PubMed2005

Archaeal diversity in tidal flat sediment as revealed by 16S rDNA analysis.

During the past ten years, Archaea have been recognized as a widespread and significant component of marine picoplankton assemblages. More recently, the presence of novel archaeal phylogenetic lineages has been discovered in coastal marine environments, freshwater lakes, polar seas, and deep-sea hydrothermal vents. Therefore, we conducted an investigation into the archaeal community existing in tidal flat sediment collected from Ganghwa Island, Korea. Phylogenetic analysis of archaeal 16S rDNA amplified directly from tidal flat sediment DNA revealed the presence of two major lineages, belonging to the Crenarchaeota (53.9%) and Euryarchaeota (46.1%) phyla. A total of 102 clones were then sequenced and analyzed by comprehensive phylogenetic analysis. The sequences determined in our samples were found to be closely related to the sequences of clones which had been previously obtained from a variety of marine environments. Archaeal clones exhibited higher similarities (83.25-100%) to sequences from other environments in the public database than did those (75.22-98.46%) of previously reported bacterial clones obtained from tidal flat sediment. The results of our study suggest that the archaeal community in tidal flat sediment is remarkably diverse.

Archaea↗
PubMed2002

Bioavailability of sediment-associated benzo(a)pyrene within single- versus multiple-species systems.

A series of experiments were conducted with benzo(a)pyrene (B(a)P) spiked sediments to determine if bioavailability of sediment-associated contaminants is affected by multiple species interactions. Three benthic invertebrates, Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus, were exposed to sediments spiked with radiolabeled B(a)P that was aged for 60 days. Organisms were introduced into the spiked sediments in single, binary, and ternary combinations. Changes in bioavailability were then determined for each species by estimating uptake clearance coefficients (ks) and bioaccumulation factors (BAFs) during 7-day exposures. In general, there was a trend toward lower ks values in binary and ternary exposures compared to the single-species systems. In contrast, BAF estimates were more variable with fewer significant differences noted among treatments. BAF estimates were highest for L. variegatus followed by C. tentans and H. azetca and appear to be dependent on specific feeding and habitat requirements as well as the relative biotransformation/elimination potential of each species. Overall, these results suggest that animal-animal interactions may be important to consider when estimating bioavailability of sediment-bound chemicals.

Animals↗
PubMed2003

Assessment of metal toxicity in sediment pore water from Lake Macquarie, Australia.

Recent investigations into the level of heavy metal enrichment in the sediments of Lake Macquarie have indicated that significant contamination has occurred over the past 100 years, with elevated levels of lead, zinc, cadmium, copper, and selenium being observed in most parts of the lake. Pore water extracted from sediments showing the greatest contamination by these metals exhibited toxicity to the larval development of the sea urchin Heliocidaris tuberculata. However, an analysis of pore water metal concentrations revealed that the concentrations of these metals were too low to cause toxicity. Rather, pore water toxicity was highly correlated with manganese for the majority of sites sampled; subsequent spiking experiments confirmed manganese as a cause of toxicity. Current levels of manganese in the sediments of Lake Macquarie have arisen from natural sources and are not the result of anthropogenic activities. These results reiterate the importance of identifying the causes of toxicity in assessments of sediment contamination, particularly when testing sediment pore waters using sensitive early life stages.

Animals↗