Sediments factors affecting toxicity

Suedel, B.C., Deaver, E. and Rodgers Jr, J.H. (1996) Experimental factors that may affect toxicity of aqueous and sediment-bound copper to freshwater organisms, Archives of Environmental Contamination and Toxicology 30 (1), 40-46. 

One of the most significant enviromnental factors affecting microbial degradation is the oxygen status of the sediment, often indirectly measured as the oxidation-reduction potential. Bottom sediments are viewed as the ultimate sink for many toxic organics. The oxygen status... 

Comparison of the relative sediment toxicity of different SPs can be difficult as there are a variety of different test methods and endpoints evaluated, in addition to other confounding factors relating to sediment quality. Amweg et al. [28] determined the toxicity of six SPs to //. azteca in 10-day studies at 23 °C in natural sediments containing 1-6% OC. Toxicity data were reported as bulk sediment concentrations and normalized to the organic carbon content (Table 5). The results indicated that normalization removed some, but not all, of the variability between sediments. Other factors such as sediment texture may also affect bioavailability and hence apparent toxicity in sediment studies. 

Bioavailability from Environmental Media. Toxicity studies in animals indicate that absorption of hexachlorobutadiene through the gastrointestinal tract, respiratory tract, and skin can occur. Studies which identify the relationship between absorption and the matrix of soils, sediments, and foods would be useful in establishing whether or not absorption is significantly affected by such factors. 

Particular interest has.been devoted to the interactions of PCBs among benthic fauna, sediment and pore water, and based on field and laboratory tests, the following factors have been evidenced to affect its bioaccumulation (i) toxic chemical structure (Goerke Ernst, 1977) ... 

Chemicals, which are persistent, toxic and liable to bioaccumulation, are called PTBs. They have primarily local effects. Persistence is the evidence that the substances half-life is greater than two months in water and greater than sue months in soil or sediment. Toxicity is the potential to adversely affect human health and/or the environment. Bioaccumulation is the evidence that the Bio-Accumulation Factor (BAF) is greater than 5000. Up to 1995, there was no clear definition of which products belong to this class [394]. Heavy metals, such as mercury and POPs fall into this category. 

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