I had a bit of time today, so I went through the map and made an updated table of the data currently displayed. But I included only those results reported as "rainwater" (not soil, snow, tap water, etc.). These are shown as ug/L, although in a handful of cases there were no units listed, and I had to guess. I generally guessed generously that they were reported in mg/L, and converted accordingly.
Out of 60 samples, 45 (75%) reported aluminum below detection levels. Of the 57 samples that indicated that they tested for barium, 35 (61.4%) were reported as "not detected". The sample from Ewel C. from Colorado was a clear outlier, and I suspect that he took figures reported in ug/L and incorrectly submitted them as "PPM". The only other unusual sample was from Dane W. (presumably Wigington), showing 3,450 ug/L from a thunder storm - and as reported in the historical literature, higher amounts of Al tend to be found in water from rapid storms (see Struempler, AW. 1975.
Trace metals in rain and snow during 1973 at Chadron, Nebraska).
Leaving out that one outlier from CO, and treating "not detected" samples as zero, I get a mean of 114.78 ug/L aluminum, and 8.72 ug/L barium. Even if one removes all of the "ND" results, the average is 444.79 ug/L aluminum, and 22.6 ug/L barium - not at all unusual compared to what has been reported in the scientific literature.
Note the one sample from Dr. I.S. Perlingieri in Maine - both Al and Ba were "ND". Numerous people also tested for arsenic, but all had an "ND" result. In retrospect, I should have included the pH results.