EVALUATING BARIUM CONCENTRATIONS IN CAVE SEDIMENTS - INTERPRETING AND UNDERSTANDING THE BARIUM DATABASES

Recent study of surficial sediment in a variety of caves across the Midwestern US yielded results showing notable variations in barium (Ba) content from cave to cave. The sediment study (Smith 2016) included caves formed in the Permian-aged gypsum deposits of Oklahoma and caves hosted in both Ordovician-aged and Mississippian- aged rocks across Missouri and Kentucky. Evaluation of the barium data uncovered interesting disparities in previous soil studies across the US and Canada and related differences in reported ‘average barium’ values in the US and Canada which deserve discussion.

In the US, average barium soil values primarily are reported from a US Geological Survey report published in 1984 (Shacklette and Boerngen, 1984). This report has been embraced and reported by other authors and agencies, including the US Public Health Service’s ATSDR (ATSDR, 2007). However, work subsequent to the USGS investigation (Pahalan and Bertetti, 2000) suggests that analytical lab (and perhaps even sampling) methods can have a significant influence on reported barium values. In addition, more recent barium values reported in Canada and used by Canadian remediation scientists prompt questions about how ‘representative’ the 1984 USGS data might be. A discussion of the variability in Smith’s (2016) data and each of the above reference works is presented along with suggestions for other researchers trying to interpret barium data in soils or sediments and relate barium results to public health guidelines.