Moos-monitoring of volatile As and Sb in Yellowstone National Park
Sarah Hofmann (08/2012-04/2014)
Support: Britta Planer-Friedrich, Julia Arndt
Mossbiomonitoring is a cheap and easily appliable method for identifying volatile As- and Sb-emissions from antropogenic and geogenic sources and has been tested successfully in volcanic areas. In June 2013 rain-covered mossbags were exposed in 5 geothermal areas at 47 sites in the Yellowstone National Park (USA) for 17 to 21 days. Mean element accumulations for Bi and Tl were under detection limit, for As 0.038 μg (g moss*day)-1 and for Sb 0,009 μg (g moss*day)-1. In the related aqueous phases Bi was under detection, concentrations for Tl were 0.2 – 0.7 μg L-1, for Sb 18 - 85 μg L-1 and for As 720 - 2030 μg L-1. Positive correlations were determined among arsenic accumulations on mosses and the dominating species arsenite as well as arsenic totals, which indicates a mechanism for release under reducing conditions. However, antimony accumulations didn’t correlate neither with their species nor totals. Furthermore there were no significant large-scale regional “hot spots” of volatile arsenic or antimony release and no clear trends suggesting a preferential degassing from different geothermal features (geothermal affected swamps, mud pots, hot springs, geysers or fumaroles). Under the qualitative ascertained parameters degassing intensities as well as the mosses condition (dry – wet) from their related locations, correlated positive with the observed element accumulations on mosses. Additionally spray water and in general low homogenous element accumulations on mosses complicated a clear interpretation. Moreover degassing from geothermal features seems to be considerably lower than, e.g., from active fumaroles at the island Vulcano (Italy). There were detected comparable element accumulations up to 0.62 μg (g moss*day)-1 for Sb and 10.90 μg (g moss*day)-1 for As for a 3 week exposure with the help of the same method. In further studies longer exposure times or another form of enrichment provided with a cover against spray water should be chosen.