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At least 793 records · Page 44Linked to original sources

PubMed2001

Effect of sediment toxicity on anaerobic microbial metabolism.

Mineralization of a readily biodegradable aromatic compound (benzoate) by intrinsic microorganisms in the anoxic sediment was used to quantify the inhibitory effect of heavily contaminated sediment from the Arthur Kill estuary (NY/NJ Harbor system, USA) on the anaerobic metabolism by naturally present bacterial populations. In anoxic microcosms, the effect of varying ratios of contaminated sediment:site water and contaminated sediment:noncontaminated sediment (Flax Pond, Stony Brook, NY, USA) were investigated. In all cases, increasing the ratio of Arthur Kill sediment in the microcosms showed an inhibitory effect on the rate of 14C-benzoate mineralization as measured by the evolution of 14CO2. This inhibitory effect could be alleviated through dilution of the sediment with noncontaminated sediment, resulting in some cases in mineralization rates that were greater by an order of magnitude. The toxicity of the sediment was confirmed by whole-sediment Microtox bioassay. Analysis of the sediment revealed high (>200 mg/kg) levels of Pb, Cu, Zn, and Cr, suggesting that heavy metals may contribute to overall sediment toxicity.

Bacteria, Anaerobic↗

PubMed2001

A rapid screening method for acid-volatile sulfide in sediments.

A new, direct method for the determination of acid-volatile sulfide (AVS) in sediments is presented. The method utilizes the direct reaction of Clines reagent with small amounts of sediment followed by colorimetric determination of AVS and offers fast analysis times without the need for specialized glassware or equipment. A comparison between AVS measured by this method and that measured by a purge-and-trap AVS method shows a linear relationship (r = 0.986, p < 0.001), although the method underestimates the AVS concentration measured by the purge-and-trap method. Sample throughput by the direct AVS method is more than 10 times that of purge-and-trap methods. The applicability of the direct AVS method to the rapid screening of AVS concentrations in sediments and for evaluating sediment quality with respect to metal contamination is demonstrated.

Acids↗

PubMed2002

A comparison of the transport and fate of polychlorinated biphenyl congeners in three Great Lakes food webs.

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow < 6.4 from sediment and approximately half of their body burden of PCB congeners with log Kow > or = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.

Animals↗

PubMed2003

Factors influencing the design of bioaccumulation factor and biota-sediment accumulation factor field studies.

A series of modeling simulations was performed to evaluate the underlying factors and principles that drive the uncertainty in measured bioaccumulation factors (BAFs) and biota-sediment accumulation factors (BSAFs) for fish, and to determine which sampling designs minimize those uncertainties. Temporal variability of chemical concentrations in the water column, and the metabolism rate and n-octanol-water partition coefficient (Kow) for the chemical were determined to be the dominant factors that influenced the field-sampling design. Spatial variability of the chemical concentrations, food web structure, and the sediment-water column concentration quotient had a lesser importance upon the overall design. The simulations also demonstrated that collection of composite water samples in comparison to grab water samples resulted in reductions in the uncertainties associated with measured BAFs. Some illustrative sampling design structures for BAF and BSAF measurements based upon the temporal variability of chemical concentrations in the water column and the metabolism rate and Kow for the chemical were developed. These illustrative designs provided a sense of how sampling design structures, that is, the number and spacing over time of sampling events, might be influenced by differences in temporal variabilities, metabolism rates, and Kow. Although the importance of spatial variability was discounted as a major factor in the design process, sampling of water and sediment across the immediate home range of the sampled organism is required for successful measurements because poor spatial coordination of organism, water, or sediment samples will yield BAFs and BSAFs with large and unknown biases.

Animals↗

PubMed2003

Accumulation of 137Cs by larvae of the midge Chironomus riparius from sediment effect of potassium.

We studied the effect of potassium on the uptake of radiocesium from sediment by larvae of the midge Chironomus riparius. Sediment ingestion rate was determined for one week. After 24 h the gut content remained constant, indicating that equilibrium was reached between sediment ingestion and sediment elimination. These data were used to account for radiocesium present in the gut in subsequent uptake experiments. Reference sediment was equilibrated with solutions containing different concentrations of potassium: 1, 10, 100, and 1,000 microM. Adsorption of 137Cs to the sediment was investigated. Three different radiocesium levels (0.3, 0.6, and 1.2 KBq/ml) were applied at the four different potassium levels. In all cases more than 94% of all radiocesium was adsorbed to the sediment within 48 h. The sediment, equilibrated with the four different potassium levels, was spiked with a constant amount of 296 Bq/ml 137Cs. Accumulation by midge larvae was followed for one week, and subsequently elimination was followed for another week. No significant differences in radiocesium levels in midge larvae among the treatments were found after one week of exposure. However, using a one-compartment accumulation model, a small but significant effect of potassium in water and sediment on the uptake and elimination rate constants (ka and ke) was found. These results indicate that although differences were rather small, radiocesium accumulation decreased with increasing potassium level in the sediment.

Adsorption↗

PubMed2003

How do mangrove forests induce sedimentation?

The mangrove forests play a significant role as sediment traps. They reduce tidal flows and induce sedimentation of soil particles at low tide. However, there are no such processes taking place in the non-mangrove areas. Site of Avicennia-Rhizophora interphase is more efficient than Avicennia and or Rhizophora zones, in trapping the sediment by 30, 25 and 20% respectively at low tide as compared to high tide.

Ecosystem↗

PubMed2002