<p>Threats from man-made radionuclides include waste issues, increasing number of power plants, underground bomb testing, nuclear weapons, and “dirty bombs”. Until recently the ionizing radiation protection system focused on protecting humans with an implied protection of biota. However, goals of sustainable development and precautionary principles for human activity are leading to an inclusion of plant and animal populations in the protection system.</p><p>From this perspective, the present thesis examines wetlands that function as sinks for the radionuclide 137Cs, and describes calculated and measured radiation doses to residing biota. Also, multi-level effects from exposure to low-dose rate ionizing radiation were studied. Accumulation of 137Cs after the Chernobyl accident fallout was studied in a riparian wetland with a mean activity concentration of 1 200 kBq m-2 in Sweden (paper I). A mass balance budget of 137Cs showed that the sedimentation of new material was balanced by the decay process of 137Cs in parts of the wetland (paper I).</p><p>Frogs were identified as organisms of concern in this wetland. Internal radiation doses, based on whole body measurements of frogs, were estimated to be lower than external doses based on soil samples (paper II). Current dose models for biota resulted in a wide range of doses depending on different levels of conservatism in the models. Therefore, in situ measurements with frog-phantoms were found to provide valuable dose information (paper III). Measured doses using frog-phantoms were lower than calculated doses using several dose models. Although a dose conversion factor by FASSET was found to be useful for comparison with measurements in the field. A higher dose was measured to the phantom surface in comparison to inner parts, i.e. the sensitive skin of frogs receives the highest dose. Estimated and measured radiation doses to frogs were below suggested dose rate limits.</p><p>Low-dose rate 137Cs exposure of eggs and tadpoles from three amphibian species, Scaphiopus holbrookii, Bufo terrestris, and Rana catesbeiana, showed no increased levels of strand breaks in red blood cells, and no effects on development, survival or growth up to metamorphosis (paper IV). The ecological factor larval density had a stronger effect on metamorphic traits than low-dose rate radiation. Higher levels of strand breaks were detected after an acute dose in R. catesbeiana than after a chronic dose supporting a dose rate limit for protection of amphibians rather than a dose limit (paper IV).</p><p>Based on current knowledge, frogs in the contaminated wetland are probably not exposed to radiation doses from 137Cs that are harmful for the population. However, variations in sensitivity between populations and species, and adaptive responses have been shown for amphibians exposed to other stressors. This supports further research on effects of chronic low-dose rates of ionizing radiation on amphibians.</p>

Threats from man-made radionuclides include waste issues, increasing number of power plants, underground bomb testing, nuclear weapons, and “dirty bombs”. Until recently the ionizing radiation protection system focused on protecting humans with an implied protection of biota. However, goals of sustainable development and precautionary principles for human activity are leading to an inclusion of plant and animal populations in the protection system. From this perspective, the present thesis examines wetlands that function as sinks for the radionuclide 137Cs, and describes calculated and measured radiation doses to residing biota. Also, multi-level effects from exposure to low-dose rate ionizing radiation were studied. Accumulation of 137Cs after the Chernobyl accident fallout was studied in a riparian wetland with a mean activity concentration of 1 200 kBq m-2 in Sweden (paper I). A mass balance budget of 137Cs showed that the sedimentation of new material was balanced by the decay process of 137Cs in parts of the wetland (paper I). Frogs were identified as organisms of concern in this wetland. Internal radiation doses, based on whole body measurements of frogs, were estimated to be lower than external doses based on soil samples (paper II). Current dose models for biota resulted in a wide range of doses depending on different levels of conservatism in the models. Therefore, in situ measurements with frog-phantoms were found to provide valuable dose information (paper III). Measured doses using frog-phantoms were lower than calculated doses using several dose models. Although a dose conversion factor by FASSET was found to be useful for comparison with measurements in the field. A higher dose was measured to the phantom surface in comparison to inner parts, i.e. the sensitive skin of frogs receives the highest dose. Estimated and measured radiation doses to frogs were below suggested dose rate limits. Low-dose rate 137Cs exposure of eggs and tadpoles from three amphibian species, Scaphiopus holbrookii, Bufo terrestris, and Rana catesbeiana, showed no increased levels of strand breaks in red blood cells, and no effects on development, survival or growth up to metamorphosis (paper IV). The ecological factor larval density had a stronger effect on metamorphic traits than low-dose rate radiation. Higher levels of strand breaks were detected after an acute dose in R. catesbeiana than after a chronic dose supporting a dose rate limit for protection of amphibians rather than a dose limit (paper IV). Based on current knowledge, frogs in the contaminated wetland are probably not exposed to radiation doses from 137Cs that are harmful for the population. However, variations in sensitivity between populations and species, and adaptive responses have been shown for amphibians exposed to other stressors. This supports further research on effects of chronic low-dose rates of ionizing radiation on amphibians.

Lead (Pb), occurs both naturally and as a pollutant in Arctic landscape systems. The ongoing climate change, especially pronounced in the Arctic, changes the premises for Pb transport and mobility. Thus, to predict future development of both natural and pollution Pb, an increased understanding of their storages and flows in an Arctic system is of interest. Here, a Pb mass-balance budget for an entire catchment in West Greenland was calculated. The budget shows that most Pb is stored in terrestrial soils (94%), while 6% of total catchment Pb is in lake sediments. Other Pb-pools are small in comparison (&lt;1% combined). The entire catchment system has a negative balance, with annual inputs of 44 g Pb from precipitation and 67 g Pb from eolian deposition, while 150 g Pb is removed from the system (through sedimentation). Limited lake water outflow (o.15 g Pb yr-1) suggests that the catchment in its entirety acts as a Pb-sink. The terrestrial system, however (wet deposition input of 34 g Pb and hydrological export of 68 g Pb annually), is considered to be a Pb-source to the aquatic system. The magnitude of hydrological and eolian transport is similar, however the former is more important for pollution Pb transport where the latter is more important for natural Pb. The fate of pollutant Pb is determined by future climate change. Wetter conditions could lead to a prolonged export of Pb further down-stream. If drier conditions prevail, eolian transport will be more important and pollution Pb could stay in soils.

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