Bioavailability organic contaminants

Huckins, J.N. Petty, J.D. Lebo, J.A. Orazio, C.E. Prest, H.E Tillitt, D.E. Ellis, G.S. Johnson, B.T. Manuweera, G.K. 1996, Semipermeable Membrane Devices (SPMDs) for the Concentration and Assessment of Bioavailable Organic Contaminants in Aquatic Environments. In Techniques in Aquatic Toxicology, Ostrander, G.K., Ed. CRC Press Boca Raton, FL pp. 625-655. 

Vrana, B. Paschke, A. Popp, R Schiiiirmann, G. 2001b, Use of semipermeable membrane devices (SPMDs) Determination of bioavailable organic contaminants in the industrial region of Bitter-feld, Saxony-Anhalt, Germany. Environ. Sci. Pollut. R. 8 27-34. 

Bioavailability of Soil-Sorbed Pesticides and Organic Contaminants... 

The term bioavailability has different meanings in different contexts and disciplines. Numerous definitions of bioavailability exist. Research on the relationship between bioavailability and chemical speciation (forms) originated in the field of soil fertility in the search for a good predictor for the bioavailability of essential plant nutrients (Traina and Laperche 1999). It is well accepted that dissolved nutrients are more labile and bioavailable to plants than solid-phase forms (including sorbed species). The same has been considered to be true for organic contaminants and their availability for microbial degradation. 

Bioavailability issues have been reviewed previously (Mihelcic etal. 1993 Boesten 1993 Baveye and Bladon 1999 Ehlers and Luthy 2003). In this review, we discuss specifically the bioavailability of soil- or sediment-sorbed organic contaminants to pollutant-degrading bacteria. Direct uptake of sorbed contaminants is perhaps the most controversial and least understood process. The definition of bioavailability given by Alexander (2000) will be used in this review. The term bioaccessibility encompasses what is immediately available plus that which may become available, whereas bioavailability refers to what is available immediately. 

Another important factor influencing the bioavailability of organic contaminants is the contact time between the contaminant and soil/sorbent, often referred to as aging. Aging often increases the sorption of organic chemicals by allowing more time for the chemicals to partition deeper into... 

Sediments can also serve as potential exposure routes for aquatic food chains through the bioaccumulation of contaminants by benthic organisms. The potential of sediment contaminants to expose organisms in sediments and the water column is determined by their bioavailability. The bioavailability or bioaccessibility of nonpolar organic contaminants is determined by how strongly they are bound to organic matter in soil and sediment [31, 32]. This fact should be taken into account in a realistic assessment of the environmental risks of these contaminants (Fig. 13). 

The bioavailability of contaminants to wildlife and humans is also an area of critical importance, where contaminants can be taken up in pore water and by dermal contact, particle ingestion, or particle inhalation. The dynamics of sorption/desorption are not currently incorporated into exposure and risk assessment models for organic compounds, where availability, in most cases, is assumed to be 100% [224]. Recently, the following have been demonstrated and reported ... 

Abdul AS, Gibson TL, Rai DN (1990) Use of humic acid solution to remove organic contaminants from hydrogeologic systems. Environ Sci Technol 24 328-333 Alexander M (2000) Aging, bioavailability and overestimation of risk from environmental pollutants. Environ Sci Technol 34 4259-4265... 

In this chapter, the speciation of HOC in the presence of DOM is critically reviewed. Specifically, models will be examined that describe the equilibrium partitioning of HOCs between water and the DOM phase, current analytical techniques for measuring DOM-HOC binding will be critically evaluated, and the importance of DOM s structure in influencing the speciation of HOCs in aquatic systems will be discussed. Finally, the degree to which DOM can influence the bioavailability of organic contaminants to organisms is examined. 

V. EFFECTS OF DISSOLVED ORGANIC MATTER ON HYDROPHOBIC ORGANIC CONTAMINANT BIOAVAILABILITY TO AQUATIC ORGANISMS... 

A few studies (Kukkonen et al., 1989 Kukkonen and Oikari, 1991 Muir et al., 1994) have reported an enhancement of organic contaminant bioavailability to various organisms. In all cases this occurred at low DOM concentrations (< 10 mg/L carbon). Currently, a specific mechanism has not been determined, but Muir and co-workers (1994) have suggested that organic mucus in fish can act in a manner similar to that of DOM and bind contaminants. They observed lower than expected bioaccumulation of pyretheroids in control studies followed by an enhancement with the addition of small amounts of DOM. Nonetheless, this does not explain the enhanced bioaccumulation observed for other aquatic organisms. 

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