Principal Investigator Charles Harvey
Project Website http://web.mit.edu/harvey-lab/Geochemistry.html
Chemical analyses of a vertical profile into both the shallow and deep aquifers at the field site were observed. Two basic results of the analysis of the solid and dissolved chemical compositions at the site are: (1) the aquifer material has no obvious difference with depth to explain the large peak in dissolved arsenic at 30 m depth and, (2) the groundwater solutes are consistent with organic carbon oxidation, iron oxide reduction and arsenic mobilization upstream of the sampling wells.
Another key observation comes from carbon dating: the dissolved carbon responsible for arsenic mobilization has been transported down from above. Dissolved inorganic carbon (DIC) and methane are much younger than dissolved organic carbon (DOC). Concentrations of inorganic carbon are about an order of magnitude higher than organic. At 19m depth the DIC contains bomb-levels of C-14, so it is very young, and at 30m depth the DIC is much younger than the aquifer. Unless, burrowing animals are extremely hard-working, this carbon must have been transported by flowing groundwater