Sediment Distribution Coefficients and Concentration Factors for ...

metal ion is commonly believed to be the bioavailable form. It is outside thescope of this study to consider the speciation of the metals in the dissolvedphase and therefore all metal in the dissolved phase is essentially presumed tobe in one pool.Some confusion may arise from the different terminology used in theliterature. Bioaccumulation factors of elements are analogous to bioconcentrationfactors, except that the former are defined as grams element per gramtissue (or whole organism) divided by grams element per gram water (dissolvedplus particulate). In this case, the total water contains both dissolved elementand element bound to suspended particulate matter. Since particle loads inoceanic systems are typically low (less than 1 mg/L), total and dissolved elementconcentrations are very nearly identical, even for particle reactive metals.Differences can become pronounced, however, for particle reactive metals inturbid coastal waters, where extreme particle loads of tens of mg/L can occur.It should also be noted that, except for algae, the term CF as used in thesecircumstances does not imply that all the elements within the organism areconcentrated by direct accumulation from the water. It is simply a value thatrelates the concentration in the organism, which may have been derived byuptake from sea water, particulate matter and food, to that of the medium inwhich it lives.The term is also used by radiobiologists studying the accumulation ofradionuclides by organisms under controlled laboratory conditions, usually thatof direct uptake from sea water. In some experiments, the results obtained aresimilar to those derived from environmental data; in others they are not. Thereare many reasons for such discrepancies, and these are often the subjects ofinvestigation. It is therefore potentially misleading to use laboratory deriveddata uncritically, and, wherever possible, environmentally derived data havebeen used in this report, although these may be equally varied for a number ofreasons, and often environmental CF data are simply lacking for certainelements.3.2. FACTORS AFFECTING CFsA number of factors must be considered in evaluating the applicability ofCFs in marine organisms. The preponderance of data on metal and radionuclideconcentrations in marine organisms is based on work with organisms fromtemperate ecosystems. Only recently have attempts been made to measuremetal concentrations in polar organisms, and some attempts have begun to comparetemperate and polar CFs. Given the limited data available on this issue, allconclusions must be considered preliminary. However, studies suggest that, as a27