The technique of computational fluid dynamics (CFD) was used to study the concentrations and distributions of indoor radon (222Rn) and thoron (220Rn) as well as their progeny in three dimensions. According to the simulation results, in a naturally ventilated room, the activity distribution of 222Rn is homogeneous except for the places near air diffuser (supply and exhaust) locations. The concentration of 220Rn exponentially decreases with the distance from the source wall which is considered independently. However, as the ventilation rate increased, the concentrations of both 222Rn and 220Rn decreased and their activity distributions become complicated due to the effect of turbulent flow. It suggests that the impact factors of monitoring conditions (sampling site, airflow characteristics, etc.) should be taken into account in obtaining representative concentrations of 222Rn/220Rn for dose assessment. Both the simulation results of activities and their distributions agreed well with the experimental results in a laboratory room. It suggests that the CFD models may be applicable for the estimation of indoor 222Rn and 220Rn as well as their progeny.

The uptake and depuration rate constants for ['4C]2,3,7,8-tetrachlorodibenzo-p-dioxin ("C-TCDD) in growing rainbow trout were obtained in a laboratory experiment involving a 6-h static water uptake exposure at 107 ng/L @pt) followed by a 139-d flow-through depuration period. Improved mathematics were developed for estimating uptake and depuration rate constants and an equilibrium bioconcentration constant that accounts for growth dilution of the total chemical body burden. The uptake and depuration rate constants ( k ; and k2) for I4C-TCDD in rainbow trout (whole fish) were determined to be 108 f 3 ml water/g whole fish/d and 0.012 f 0.001 d-', respectively. Based on these data, the equilibrium bioconcentration constant for TCDD, defined as the ratio of uptake to depuration rate constants, was 9,270 f 1,050, and the elimination halflife, of the total body burden was 58 f 5 d. Clinical observations of the fish concurred with those previously reported by other researchers.

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The concern of this stndy has been the chemical composition of Uaphnia omgnu, the algae (Selenustrum, cnpricornutuni, Ankistrodesmus convolutus) it was fed, the two growth media in which the algae were cultured and the water (Lake Huron, Michigan, USA) in which D. magnu was reared. A synthetic diet (fish chow+alfalfa) was used as a control. The effectiveness of these five diets on the health of the 1). inagna populations was ascertained by t,he weight and number of neonates thus produced. The diet, S. capricornufuin cultured in an organic medium, prodnced the largest mean brood size and the heaviest neonates in unstressed populations. The synthetic diet prodnced the smallest mean brocd size and the lightest neonates. Stressed organisms may produce smaller broods wit.h heavier neonates than unstressed organisms. The erolnticnary significance of this observation is discussed. Statistical studies suggetit that daphnids maintained on the synthetic diet derired no demonstrable nutritive value from the diet in terms of elemental composition or amino acid production. A great similarity in patterns cf amino acid quantity and type was noted in the algae and the daphnids. On further examination it was discoverctl that this pattern was widespread in other aquatic forms, bacteria, fungi, yeasts, casein and was common t o a variety of birds and mammals. It may be suggested that products that are made and stored, such as lipids. are less uniform in pattern among widely diverse species than those that have t o he produced and are not stored. such as amino acids.