Printed in the United States of America. Available from National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road, Springfield, Virginia 22161 Price: Printed Copy $7.60; Microfiche $2.25 This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the Energy Research and Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, tnakes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. .._.._._._ QRNL-5002 UC-I 1 - Environmental and Earth Sciences Contract No. W-7405-eng-26 Environmental Sciences Division ULATIBN FACTORS FOR IN FRESHWATER BI Henry A. Vanderpl oeg Dennis C. Parzyck ... William H. Milcox James R.. Kercher Stephen ‘1. Kaye 1 1 iii ... This report analyzes over 200 carefully selected papers to provide concise data sets and methodology for estimation of bioaccumulation factors for tritium and isotopes of strontium, cesium, iodine, manga- nese, and cobal t in major biotic components of freshwater environments Bioaccumulation factors of different tissues are distinguished where significant differences occur. Since conditions in the laboratory are of ten unnatural in terms of chemi cal and ecological re1 ati onships this review was restricted as far as possible to bioacciiniulation factors determined for natura? systems. Because bioaccumu ation factors were not available for some shorter-lived radionuc ides, a methodology for converting bioaccurnul ation factors of stab e isotopes to those of shorter-lived radionuclides was derived and utilized. The bioaccumulation factor for a radionuclide in a given organism or tissue may exhibit wa’de variations among bodies of water that are related to differences in ambient concentrations of stable-element and carrier-element analogues. To account for these variations simple models are presented that relate ~ioac~u~~~a~~o~factors to stable- element and carrier-element concentrations in water. The effects of physicochemical form and other factors in causing deviatfcmns from these models are discussed. Bfoaccumulation factor data are examfned in the context of these models, and bioaccurnulation factor relations for the selected radionuclides are presented. S UMMA R Y BIOA~C~~U~ATI~~FACTOR CONCEPTS The biOWXUMulatiOn factor for an organism or tissue i is’the -state ratio of radionuclide concentration in the organism or tissue to that in water: where BF(RIi = bioaccumulation factor for radionuclide R in organism or tissue i, [RIi = radionuclide concentration (pCi/g fresh wejght) in organism or tissue i and [RIW = radionuclide concentration in water ($i/g)3 a constant. Bioaccumulation factors are used to p-edict radionuclide c~~c~~~r~t~~~~ in whole organisms or their tissues from knowledge of the ~ad~~nL~~li~~ concentration in water for chronic releases of radionuclides. Bjo- accumulation factors for radionuclid2s were related to ambient concentrations of their stable or novisotopic carrier element analogues according to three idealized patterns. The first pattern is that the bioaccumulation factor for radionuclide R in organism or tissue i, BF(RIi, is constant regfirdless of stable-element or carrier-element concentration : The second pattern applies to an element that is homeostatically Vi maintained at a constant concentration in organism or tissue i: Where Xi = concentration of stable element in organism or tissue i , a constant (ug/g fresh weight) , and [CIkJ '= concentration of corresponding stable element in water (vg/g 1 * The third pattern applies to a radioisotope and its non-isotopic carrier element which is horneostatical ly maintained at a constant Concentration in i: qi = discrimination coefficient, Zi* = concentration of non-isotopic carrier element in organ- ism or tissue i, a constant (Iig/g fresh weight), and [C*3, = concentration of nsn-isotopic carrier element in water (ug/y) " The discrimination coefficient, qi , is the ratio ([R]i/lC*]i)/( [RIP// [C*Iw), where [C*], is the carrier element concentration in i. Equation (3) is often rewritten in the form: vii Radionuclides exist in a wide variety of physicochemical forms in natural waters, and their different forms have different avail- abilities to the food chain, Sediments, too, may be source of radionuclides to biota, and sediment type can influence the avail- ability. For those elements that are hsmeostatically maintained at constant concentrations in a giver organism, the concentration of stable element in the organism is independent of concentration of stable element in water or its availability in prey, sediment, and different physicochemical forms in the water. In contrast, dif- ferences in availability of radionucl ides in different sediment types and different physicochemical forms in water can 'lead to niarked deviations from the idealized patterns of Equats'ons (1) and (3)- lrlhen bioaccumulation factors were not available for radiunuclides they were estimated froni bioaccumwl ation factors of the corresponding stable elements. Owing to physical decay, the bioaccumulation factor of a short-lived radionuclide is much less than that of the stable element or longer-lived nuclides. 5iaaccumulation factors of shorter- 1 ived radionuclides were estimated from bioaccumulation factors sf the stable element according to the relation: 2 BF(R)i = r<.q 5FWi 7 where k = elimination coefficient of C in i (day-'), A = radioactive decay constant (day-')3 and viii BF(C) = bioaccumulation factor of corresponding stable elemerat in i. B IOBCCUMULA'T ION FACTORS Potassium is a non-isotopic carrier elerrretit For cesiiim because of the?'t- chemi sa7 simi 1 ari ties and the greater abundance of potassi iarn in water. Further, since potassium concentration is horncostatically maintained 3t constant concentrations in animals, the bioaceumulation factor of cesiuin -is given by Equation (3) or (4). Unlike this pattern for animals, potassium concentration of water has only a smal 1 effect on the cesi urn bi oacciiinul ation factor in a1 gae. The primary mode of accimulation of cesium and pstai;siurn in aquatic animals is Prom the food chajn. Absorptl'on efficiency of potassium and cesium from food is high. In animals the excretion coefficient of potassium is about. 3 times larger than the excretion coefficient of cesium. As a result, qi increases by a factor of about 3 with each trophic level. If potassiiern concentrations in the predators and prey are about equal, the cesium bioaccumulation factor increases by a factor of 3 with each trophic level. Because cesi urn a's strmgly adsorbed by suspended particulate materials, especially clays, the proportion of cesium in the soluble phase decreases w'ith increasing suspended solids concentrations. Potassium, too, is sorbed but to a much lesser degree. Since algae accumulate cesium, potassim, and other elements from the soluble phase, the availabilities to the food chain of cesium and of cesium ix relative to potassium decrease with increasing suspended solids concen- trations. Thus, discrimination coefficients and bioaccumulation factors decrease with increasing suspended solids concentrations. On the basis of data available, we recommend the bioaccumulation factors given in Table 1. Stronti um Cal ci um is a non- i so topi c carri er el emen t for stronti um because of their chemical similarities and the greater abundance of calcium in water. Further, since calcium concentration is homeostatically mas’ntained at constant concentrations in animals, the bioaccumulation factor of strontium is given by EqLation (3) or (4). Unlike this pattern for animals, calcium concerttration of water has only a small effect on the strontium bioaccumulation factor in algae, a The primary mode of uptake of strontium and calcium in animals (as well as plants) is from water. As a result, trophic level has little effect on the discrimination coefficient and the bioaccumulation factor of strontium. Further, the discrimination coefficient is relatively independent of calcium concentration in water. Calcium and strontium concentrations in bones and shells are higher than in other tissues of animals. Strontium has physicochemical properties similar to calcium and, like calcium, appears mainly as free ions in water. As a result of this and the fact that the discrimination coefficient is independent of calcium concentration in water, the discrimination coefficient varies little among sites. This implies that the product qici * X Table 1. Recommended bioaccumulation factor relations for 1 ong-1 ived isotopes of cesi urna .. .. .. ..... __I.. .. .- Yaxsn/ Recommended Functional Tissue Envi ronrnent Bioaccumul ati on Group Factor Re1 ation , ... .. Piscivorous b fishes A17 tissues C1 eay waters Piscivorous d fishes A11 tissues Turbid waters on -p i s c i vor ou s M fishes All tissues Clear waters Non-piscivorous fishes All tissues Turbid waters A1 gae Whol e A1 1 waters Aquatic vascul ar plants Whol e A1 1 waters 1 o3 Emergent vascular plants Whol e A1 1 waters Mol 1uscs She1 1 A1 1 waters Soft tissues All waters Invertebrates other than mol 1 uscs WhQl e All waters I o3 Amphibians All tissues A? 1 waters 1 o4 Waterfowl A?? tissues All waters 3x1 o3 I- aTo convert to bioaccumulation factors of 13%s use conversion factors in Table 3.1.1. bSuspended sol