Tree Density on a Vegetated Uranium Mill Tailings Site and Associated Estimates of Ra-226 in Above Ground Biomass
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Abstract
The transfer of Ra-226 to the terrestrial pathway will depend on the uptake by indigenous species which colonize dry areas of inactive or abandoned uranium mill tailings sites. The density of Trembling aspen and White birch, their heights and biomass values, have been determined 10 to 15 years after revegetation. In addition the percentage composition of the ground cover for herbs, shrubs and grasses is evaluated.
For aspens of less than 1m in height, the density of 0.0536 trees/m^2 was considerably higher than for the birches of the same height with 0.0097 trees/m^2 decrease to 0.0049 and 0.0010 respectively for 3 to 4m tall trees. Trees taller than 4m were rarely found. The ground cover biomass (approximately 125 g/m^2) consisted generally of two types: either shrubs were dominant or herbs and grasses prevailed.
From Ra-226 concentrations in different above-ground biomass components and the average composition of the vegetation on one square metre, transfer values were estimated. Annual transfer by herbal biomass (leaves, herbs and grasses) ranged from 330 to 760 pCi/m^2. The standing crop of woody biomass was estimated to range from 450 to 1700 pCi/m^2.
For aspens of less than 1m in height, the density of 0.0536 trees/m^2 was considerably higher than for the birches of the same height with 0.0097 trees/m^2 decrease to 0.0049 and 0.0010 respectively for 3 to 4m tall trees. Trees taller than 4m were rarely found. The ground cover biomass (approximately 125 g/m^2) consisted generally of two types: either shrubs were dominant or herbs and grasses prevailed.
From Ra-226 concentrations in different above-ground biomass components and the average composition of the vegetation on one square metre, transfer values were estimated. Annual transfer by herbal biomass (leaves, herbs and grasses) ranged from 330 to 760 pCi/m^2. The standing crop of woody biomass was estimated to range from 450 to 1700 pCi/m^2.
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