Factors affecting the fate of anthropogenic components

Concentrations of chloroaromatics are usually higher in aquatic than terrestrial animals (deVoogt 1996). In fish, most of the variation in concentrations of DDT and PCBs can be explained by variations in lipid content, trophic level and trophic structure (Rowan Rasmussen 1992), with environmental levels (in water and soil) playing a subordinate role. The ocean serves as a sink for chloroaromatics. 

Bioconcentration factors are higher for fish than their invertebrate prey, by almost an order of magnitude for some Aroclor mixtures (LeBlanc 1995 Box 7.3). Biomagnification factors over several marine trophic levels are usually an order of magnitude greater for PCBs than PCDDs and PCDFs (Niimi 1996 Box 7.3). The pattern of PCBs observed in a particular organism may be controlled by metabolic processes, rather than dietary factors such as the type of prey consumed (Leonards et al. 1994). 

It is worth noting that humans are not the only organisms to affect ecosystems by the input of potentially toxic materials. Phytoplanktonic succession is affected by various chemicals exuded by different species. Some 

Bioavailability is a major control of the extent to which a contaminant builds up in the tissues of an organism, and is determined by factors such as solubility and adsorption on to soil/sediment. Aqueous solubility is influenced by the shape, size and functional group content of a chemical (Aislabie Lloyd-Jones 1995). Whether sorption (adsorption or absorption) is likely to increase or decrease bioavailability and degradation rates in soils is difficult to predict (Harms Zehnder 

The degree and position of chlorination affects the bioavailabilities of chloroaromatic compounds. For example, the higher chlorinated PCBs, PCDDs and PCDFs tend to exhibit lower bioaccumulation rates than their lower chlorinated counterparts in the presence of sediment and soil, apparently reflecting variations in adsorption characteristics of the chloroaromatics (Tarsen et al. 1992 Toonen et al. 1994). 

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