A double-tracer technique to determine the relative importance of water and food as sources of polonium-210 to marine prawns and fish

Abstract

Accumulatlon of polonium In the common prawn Palaemon serratus and the sea perch Serranus scnba was studied expenmentally to clanfy the relative Importance of water and food as sources of the hlgh 210Po concentrations usually found in marlne organisms A double-tracer technlque was used whlch enables dlfferentlating the bioaccun~ulation of PO dissolved in seawater (as 210Po) and the dlgestlve transfer of PO from food (as 208Po) Accumulatlon of d~ssolved PO by prawns was found to occur m a~n l y through adsorption on the exoskeleton w~t h a minor accumulation in internal tissues through the intake of seawater for osmoregulatlon In contrast, 208Po in labelled food was r e a d~l y absorbed and accumulated In the Internal tlssues of prawns Sim~lar expenments w~t h fish indicated that "'PO dissolved in seawater did not contribute directly to PO accumulated in lnternal organs Instead, nearly all internally bound PO resulted from the assimilat~on of 208Po-labelled food Measured PO absorption efficlenc~es were approxmately 0 35 and 0 05 of the Ingested dose for prawns and flsh respect~vely, and roughly corresponded to the assimllatlon effic~encies of proteins from food In both pra\vns and flsh, ingested 208Po distributed In the tissues In a manner s~m~l a r to naturally occurnng 'I0Po in control organlsms, whereas 2'oPo dissolved in seawater parhhoned differently Modelling uptake through both pathways demonstrated that PO in the food accounted for >97 % of the PO measured in these 2 organlsms These expenmental results suggested that, In nature, accumulation of PO by m a n n e organlsms In higher trophlc levels depends upon the prevlous PO blndlng to organlc matter In lower troph~c levels, therefore, PO transfer through manne food-chains is p n m a r~l y a funct~on of the food a s s d a t~o n effic~ency and feeding rate of the organlsms The double-tracer technlque descnbed here IS a useful expenmental tool in the study of PO transfer pathways in manne organisms, and could also be a p p l~e d to the study of other aspects of PO b~ogeochenl~stry

Contrasting transfer of polonium-210 and lead-210 across three trophic levels in marine plankton

“…The AE in prawns fed 210 Po-labeled food was 35% (Carvalho & Fowler 1994), and the AE was estimated to be at least 5 times higher for Po than Pb in shrimp (Carvalho & Fowler 1993 (Carvalho & Fowler 1993). The same results were found in herbivorous copepods, where the AE ranged from 20 to 55% depending on the algal diet (Stewart & Fisher 2003b Pb generally seen in marine zooplankton , and this study) explain the high 210 Po: 210 Pb activity ratios (10 to 1000) in invertebrate tissues (Carvalho & Fowler 1994 Pb into larger crustaceans such as shrimp (Cherry & Heyraud 1982, Heyraud et al 1988, Carvalho & Fowler 1993, isopods (Stepnowski & Skwarzec 2000) and lobsters (Heyraud et al 1987, Durand et al 2002 Po concentrations recorded in natural samples are found in the hepatopancreas of these crustaceans (Cherry & Heyraud 1982), possibly due to sulfur-rich, metal-binding proteins found in high concentrations in these organs. Durand et al (2002) showed that hemocyanin and ferritin from lobsters had extremely high affinities for 210 Po, and Stepnowski & Skwarzec (2000) Pb activity ratios in the hepatopancreas of Baltic crustaceans.…”

Bioaccumulation of polonium‐210 in marine copepods

“…Measurements of 210 Po concentrations in biota (Shannon et al 1970;Folsom and Beasley 1973;Germain et al 1995) can be used to infer the trophic transfer of 210 Po in marine food chains, but few studies have assessed the rates and mechanisms involved in the uptake of 210 Po from food (Carvalho and Fowler 1994). Understanding these processes may explain observations that 210 Po is highly concentrated in the tissue of commercially important vertebrates and invertebrates (Dahlgaard 1996;Stepnowski and Skwarzec 2000).…”

Hydrological, geological, and biological site characterization of breccia pipe uranium deposits in Northern Arizona

“…Polonium (Po) and protactinium (Pa) present the greatest hazards when ingested or inhaled. For example, studies have demonstrated that 210 Po is accumulated to exceptionally high levels in tissues of a variety of marine organisms, well above levels of the parent radionuclide 210 Pb (Carvalho and Fowler, 1994;Stepnowski and Skwarzec, 2000). The behavior of …”