Aquatic systems bioaccumulation

The criteria listed in Section 4.3.1 were applied to the selection of biological indicators to ensure their relevance and utility for assessing trends in the bioaccumulation of MeHg associated with altered loadings of mercmy to aquatic systems. This evaluation, based largely on the discussion in Section 4.3.2, is summarized in Table 4.1. 

Nendza, M. (1991). QSARs of bioconcentration validity assessment of logPow/ logBCF correlations. In Bioaccumulation in Aquatic Systems, eds. Nagel, R. and Loskill, R., Series, VCH, Weinheim, Germany, pp. 43-66. 

No experimental information could be found in the available literature on bioconcentration or bioaccumulation of endrin aldehyde or endrin ketone. Estimated BCFs indicate some potential for bioaccumulation for both compounds. No information was found on concentrations of either of these compounds in aquatic systems, but it would be expected that levels would be nondetectable or very low, and that they would continue to decline. Therefore, additional information is not needed at this time. 

The problem of toxic pollutants is difficult to handle because of the great variety of chemicals involved. They represent a hazard not only to aquatic life, but also to human health, either through direct exposure or indirectly through consumption of contaminated fish or waterfowl. The degree of hazard depends on the pollutanf s toxicity, rate of discharge, persistence and distribution in the aquatic system, and bioaccumulation potential. Some highly volatile compounds, when discharged into water, evaporate and become air pollutants. 

Hildebrand SG, Cushman RM, Carter JA. 1976. The potential toxicity and bioaccumulation in aquatic systems of trace elements present in aqueous coal conversion effluents. Proc Univ MO Annu Conf Trace Subst Environ Health. 10 305- 313. 

Once produced PAHs can be transported through the atmosphere or the water column if directly discharged via uncombusted petroleum. In the air, PAHs partition between the gas and particle phases, can undergo photochemical and oxidation reactions, be washed out by precipitation and deposit to aquatic surfaces by both wet and dry deposition. Once in the aquatic system, PAHs partition between the dissolved and particulate phases, can undergo photochemical reactions and bioaccumulate in the lower trophic levels. 

PAHs enter the environment from both natural and man-made sources, and the anthropogenic point and nonpoint sources are the major sources. The nonpoint sources are diffuse sources disseminated through the air and waterways. In aquatic systems, PAH-enriched particles or floes may settle to the lake s bottom under calm conditions and accumulate in the sediments. Once the PAH-enriched particles have accumulated in the lake s floor, they may undergo a number of changes that are mediated by chemical or microbial activities. As a result, the bound PAHs can be released from the sediment into the water phase. Once they enter the water column, they may also enter phytoplankton. The PAHs in phytoplankton may then bioaccumulate in the food web. This can cause both acute and chronic effects in fish, birds and other mammals that feed on aquatic organisms (Zhang, 1998). 

Paquin PR, Santore RC, Farley K, Di Toro DM, Wu KB, Mooney KG, Winfield RP. 2003. Metals in aquatic systems a review of exposure, bioaccumulation, and toxicity models. Pensacola (FL) SETAC Press, 168 p. 

In aquatic systems, in addition to the complexation of metal ions by natural organic matter, metal bioavailability, bioaccumulation, and toxicity are highly affected by water hardness and alkalinity (Banks et al. 2003). This is also applicable to metal mixtures where complexation of metals can occur even at higher rates than when single chemical compounds are present. 

Nagel R, Loskill R, editors. 1991. Bioaccumulation in aquatic systems. Contributions to the assessment. Weinheim (DE) VCH. 

Butte W (1991) In Nagel R, Loskill R (eds) Bioaccumulation in Aquatic Systems, contribution to the Assessment. Proceedings of an International Workshop, Berlin 1990. VCH Weinheim New York Basel Cambridge, pp 29... 

Demethylation in the water column and sediments is receiving increasing attention. Both abiotic (e.g.. Sellers et al., 1996, 2001) and biotic (e.g., Pak and Bartha, 1998 Marvin-Dipasquale and Oremland, 1998 Marvin-Dipasquale et al., 2000 Hintehnann et al., 2000) processes are imphcated. The result is that MMHg accumulation in aquatic systems represents a balance between methylation, bioaccumulation, and the demethylation processes. In sediments, MMHg decomposition is particularly important, and it is possible that some sediments represent net sinks, rather than net sources, for MMHg in the water column. 

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