Soil volatile mercury, boron and ammonium distribution at Cañadas caldera, Tenerife, Canary Islands, Spain

Spatial distribution of soil Hg, B and NH4 was investigated in the soils of Cañadas caldera, Canary Islands, in the summer of 1992. Soil Hg, B and NH4 were also studied over several transects intersecting structural features. Soil Hg concentration ranged from 10.83 to 45,000 μg kg−1 whereas those of B and NH4 ranged from 8.45 to 4512 μg kg−1 and from 0.31 to 181 mg kg−1, respectively. Probability plot analysis identified 3 geochemical populations for Hg and B whereas only 2 were detected for NH4. Multivariate analysis (cluster, factor and multiple regression analysis) was used to identify subtle geochemical characteristics of the groups and factors and to determine the relationship between Hg, B and NH4 and the soil secondary parameters. High soil Hg, B and NH4 concentrations are interpreted as being related to areas where a convection system has developed, coinciding with the most recent volcanic centers located along the basaltic rift zones and with the main features inside Cañadas caldera: Teide volcano and Roques de García. Background levels of soil volatiles are present in locations where no indication of subsurface thermal activity occurs. Generally, the secondary controls on Hg, B and NH4 are subtle and are overwhelmed in areas characterized by subsurface geothermal activity.