Water and soil biotic relations in mercury distribution

The distribution of Hg is considered both in terms of its availability in soil fractions and the relationship between Hg in plant samples and Hg in ambient soils or other supportive media. The plants were grouped by habitat into epipedic-epiphytic (mosses, lichens) and endopedic-aquaticmarine (Basidiomycetes and algae) samples; non-vacular and vascular forms were also distinguished. Sources included Alaska, Hawaii, New England and Iceland. Brief consideration was also given to Hg distribution in a plant-animal-soil community. Data were expressed in terms of plant Hg content and plant substratum concentration ratio. Average Hg contents and concentration ratios, and modal ranges for the ratios were determined. The results showed similar average Hg contents in all groups (126 to 199 ppb) but a low value (84 ppb) in the lichens; terrestrial forms had ratios of 3.5 to 7.6 whereas the marine algae yielded a figure of 78.7. The modal ranges were 1 to 2 fold for mosses and lichens, 2 to 10 fold for Basidiomycetes and vascular plants and > 10 fold for algae. In addition to the modal ratio in the range 2–10 common to all 275 vascular plant samples, a secondary mode in the range 0 to 0.1 appeared only in the Alaska-New England group, over 500 km distant from active thermal sites. Thus evidence for both exclusion and concentration behavior was obtained.