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Data from published studies and World Wide Web sources were combined to produce and test a regression model to predict Cs concentration ratios for freshwater fish species. The accuracies of predicted concentration ratios, which were computed using 1) species trophic levels obtained from random resampling of known food items and 2) K concentrations in the water for 207 fish from 44 species and 43 locations, were tested against independent observations of ratios for 57 fish from 17 species from 25 locations. Accuracy was assessed as the percent of observed to predicted ratios within factors of 2 or 3. Conservatism, expressed as the lack of under prediction, was assessed as the percent of observed to predicted ratios that were less than 2 or less than 3. The model's median observed to predicted ratio was 1.26, which was not significantly different from 1, and 50% of the ratios were between 0.73 and 1.85. The percentages of ratios within factors of 2 or 3 were 67 and 82%, respectively. The percentages of ratios that were <2 or <3 were 79 and 88%, respectively. An example for Perca fluviatilis demonstrated that increased prediction accuracy could be obtained when more detailed knowledge of diet was available to estimate trophic level., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The rates of accumulation and subsequent loss of stable cesium (¹³³Cs) by organisms at different trophic levels within plankton-based and periphyton-based food chains were measured following the addition of ¹³³Cs into a small reservoir near Aiken, South Carolina, USA. An uptake parameter u (L kg⁻¹ d⁻¹ dry mass) and a loss rate parameter k (d⁻¹) were estimated for each organism using time-series measurements of ¹³³Cs concentrations in water and biota, and these parameters were used to estimate maximum concentrations, times to maximum concentrations, and concentration ratios (C(r)). The maximum ¹³³Cs concentrations for plankton, periphyton, the insect larva Chaoborus punctipennis, which feeds on plankton, and the snail Helisoma trivolvis, which feeds on periphyton, occurred within the first 14 days following the addition, whereas the maximum concentrations for the fish species Lepomis macrochirus and Micropterus salmoides occurred after 170 days. The C(r) based on dry mass for plankton and C. punctipennis were 1220 L kg⁻¹ and 5570 L kg⁻¹, respectively, and were less than the C(r) of 8630 L kg⁻¹ for periphyton and 47,700 L kg⁻¹ for H. trivolvis. Although the C(r) differed between plankton-based and periphyton-based food chains, they displayed similar levels of biomagnification. Biomagnification was also indicated for fish where the C(r) for the mostly nonpiscivorous L. macrochirus of 22,600 L kg⁻¹ was three times less than that for mostly piscivorous M. salmoides of 71,500 L kg⁻¹. Although the C(r) for M. salmoides was greater than those for periphyton and H. trivolvis, the maximum ¹³³Cs concentrations for periphyton and H. trivolvis were greater than that for M. salmoides., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

To measure the long term retention and seasonal dynamics of an initial 4 kg addition of (133)Cs into an 11.4-ha, 157,000 m(3) reservoir (Pond 4, near Aiken, South Carolina, USA), the concentrations and inventories of (133)Cs in the water column were measured at periodical intervals for 522 days following the 1 August, 1999 release. After rapid declines in concentrations and inventories during the first 90 days, the (133)Cs concentrations in the water column declined at an average proportional rate of 0.004 d(-1). However, there were periods of less rapid and more rapid rates of declines, and these were correlated with periods of increasing and decreasing K concentrations in the water column. The decline rates were less and the K concentrations greater in the winter than in the summer. In the deeper, neighboring monomictic reservoirs of Par Pond and Pond B, a yearly cycle of increasing and decreasing (137)Cs concentrations in the water column is driven by anoxic remobilization of Cs from the sediments into a persistent summer hypolimnion. In Pond 4, whose mean depth of 1.6 m is too shallow to support a persistent anoxic hypolimnion, the pattern of yearly dynamics for K and Cs appear to be related to the accumulation and release of these elements from the extensive, seasonal macrophyte communities. The contrasting results between Pond 4 and Pond B suggest that a full appreciation of the relative importance of 1) anoxic remobilization and 2) accumulation and release by macrophytes in these systems remains to be established., (Copyright 2010. Published by Elsevier Ltd.)

An uptake parameter u (Lkg(-1)d(-1)) and a loss rate parameter k (d(-1)) were estimated for the patterns of accumulation and loss of (133)Cs by three fish species following an experimental (133)Cs addition into a pond in South Carolina, USA. These u and k parameters were compared to similar estimates for fish from other experimental ponds and from lakes that received (137)Cs deposition from Chernobyl. Estimates of u from ponds and lakes declined with increasing potassium concentrations in the water column. Although loss rates were greater in the experimental ponds, the times required to reach maximum Cs concentrations in fish were similar between ponds and lakes, because ponds and lakes had similar retentions of Cs in the water column. The maximum Cs concentrations in fish were largely determined by initial Cs concentrations in the water column. These maximum concentrations in fish and the times required to reach these maxima are potentially useful indicators for assessments of risks to humans from fish consumption.

Free-ranging mammals near the Chornobyl nuclear reactor are experiencing substantial radiation dose rates from intramuscular concentrations of 134,137Cs and skeletal 90Sr. Radiocesium concentrations averaged 3,200 Bq/g of dry muscle, compared to a mean of 297 Bq 90Sr/g in bone for mammals in the Exclusion Zone, a region of restricted human activity surrounding the reactor. Estimates of dose rates from intramuscular sources of radiocesium averaged 2.4 mGy/d within 8 km of the reactor and ranged as high as 60 mGy/d. Overall dose rates from internal 90Sr for mammals in the Exclusion Zone averaged 1.0 mGy/d, although doses to specific tissues are likely much higher. Mammals captured 30 km southeast of the reactor averaged only 2 Bq/g of muscle and were receiving an average of 1.4 µGy/d from internal radiocesium. Dramatic variation exists in the spatial pattern of radiocesium in areas immediately surrounding the reactor and within and between remediated and unremediated regions. The variance of 134,137Sr for taxa among sites was significantly less than that for 134,137Cs. Thermoluminescent dosimeters placed on free-ranging mice showed that dose rates from external sources of radiation were much greater than the dose rates from internal sources of radiocesium. Estimated dose rates in very small areas of the Chornobyl region exceed those reported to impede reproductive success in mammals. [ABSTRACT FROM AUTHOR]

Gamma spectroscopy measurements were used to estimate concentrationsof 241Am and 137Cs in soil profiles to depths of 21 cm at on-site and off-site locations around the Rocky Flats Environmental Technology Site and at regional background locations east of the Front Range between Colorado's borders with New Mexico and Wyoming. Concentrations of these radionuclides were compared with concentrations of 239,240Pu in the same samples. Concentrations of 241Am in soil from depths of 0 to 3 cm decreased in an easterly direction from more than 5.3 kBq kg-1 near the 903 pad to background levels of 1.3 Bq kg-1 5 to 7 km away at a rate that was nearly proportional to the inverse square of distance. Deposits of 137Cs were ubiquitous, averaging 0.12 kBq kg-1 in soil from depths of 0 to 3 cm, but were unevenly distributed around Rocky Flats and the regional background locations. Deviations from the uniform exponential rate at which soil concentrations of 137Cs typically decreased with depth, -0.25 cm-1 at undisturbed sites, enabled us to determine that about 10% of our sampling sites had been disturbed by erosion, tillage, or other factors. The mean rate at which 239,240Pu decreased with depth was about the same, -0.23 cm-1, throughout the study area. Soil concentrations of 241Am decreased with depth at a similar mean rate of -0.22 cm-1 at locations close to the 903 pad where measurements were robust. Ratios between 241Am or 239,240Pu and 137Cs proved more useful for delineating the extent and pattern of contamination from Rocky Flats than did activity concentrations in soil. [ABSTRACT FROM AUTHOR]